Orion Drive space battle
Nyrath
depicting Orion drive battleship engaged in combat.
A short sample is here:
http://rhysy.plexersoft.com/Deep%20Space%20Force%20Gallery/US%20test.avi
He has a question. What will the combat damage look like?
He read the following from my website:
http://www.projectrho.com/rocket/rocket3x.html#nuke
> 1e8 watts per square centimeter for about a microsecond will melt
> part of the surface of a sheet of aluminum. 1e9 W/cm2 for a
> microsecond will vaporize the surface, and 1e11 W/cm2 for a
> microsecond will cause enough vaporization to create impulsive shock
> damage (i.e., the surface layer of the material is vaporized at a
> rate exceeding the speed of sound).
and asked the following:
> So what's actually seen visually, i.e. what does impulsive shock
> damage look like ? I figure the kiloton bombs will only be launched
> from the cannons, and I guess they'd blast a bloody great hole in the
> side of the ship but not actually destroy it. The larger ones
> launched from silos could be >~100 megatons - would these entirely
> vapourise a ship (or at least blast it into such small fragments that
> it would look the same), turn it into a great molten lump of metal,
> or just smash it into several large fragments ?
Anyone have some insights?
Background:
His original orion drive concepts:
http://rhysy.plexersoft.com/orion/
http://www.nuclearspace.com/gallery_orion_movie.htm
gallery of orion drive battleships
http://rhysy.plexersoft.com/Deep%20Space%20Force%20Gallery/
His somewhat off-beat alternate future history:
> This one will take the form of a space battle. In 1962 President
> Kennedy was shown a model of the spaceship as a last-ditch effort to
> keep the project alive. This abominable concept was for a ship
> capable of wiping out every Russian city with a population over
> 200,000 from orbit. Sadly the model has now been lost. Descriptions
> of it say it was equipped with 5 inch guns for defence,
> Casaba-Howitzer bombs (a directed-energy nuke), and 500
> Minuteman-style 25 megaton bombs. Kennedy, like the scientists
> involved and any sane person, hated the idea. One year lated the
> Limited Test Ban Treaty was signed and the project was cancelled.
>
> But supposing Kennedy had, for some reason, been a warmonger ? With
> the opportunity of obliterating Communism he would surely have
> enthusiastically endorsed the project. However, it has since come to
> light that though the US had no knowledge of it, the Russians knew of
> the American program and had started their own. So had Battleship
> Orion gone ahead, the result would be a stalemate. The Cold War would
> have continued, each side continuing to build a fleet of space
> battleships, never risking open conflict for fear of total
> annihilation.
>
> I will set the eventual battle in 2050 at Callisto, outermost of the
> Gallilean moons of Jupiter. 2050 provides ample time for development
> of large ships (and I do mean large) and sophisticated space weaponry
> (lasers etc.) but does not lie too far outside the bounds of
> foreseeable advances. I chose Callisto for no real reason; I just
> wanted to render it.
>
> Everything here will be physically and technologically sound. No Star
> Trek shields or tractor beams or spaceships performing impossible
> manoeuvers (with artistic concessions such as audible explosions in
> space). If anyone has any good links to possible space weapons it
> would be much appreciated.
John Reiher
Nyrath <nyr...@projectrho.com.INVALID> wrote:
> A gentleman named Rhys Taylor is making a short movie clip
> depicting Orion drive battleship engaged in combat.
> A short sample is here:
> http://rhysy.plexersoft.com/Deep%20Space%20Force%20Gallery/US%20test.avi
>
> He has a question. What will the combat damage look like?
I don't know, but I would love to see it.
--
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lal_truckee
> In article <Kfqdnd5qO7ayyyDZ...@io.com>,
> Nyrath <nyr...@projectrho.com.INVALID> wrote:
>
>> A gentleman named Rhys Taylor is making a short movie clip
>> depicting Orion drive battleship engaged in combat.
>> A short sample is here:
>> http://rhysy.plexersoft.com/Deep%20Space%20Force%20Gallery/US%20test.avi
>>
>> He has a question. What will the combat damage look like?
>
> I don't know, but I would love to see it.
From a great distance.
I suppose Mr. Taylor has read Niven/Pournelle's version of an Orion
drive battleship engaged in combat in "Footfall?"
Nyrath
> I suppose Mr. Taylor has read Niven/Pournelle's version of an Orion
> drive battleship engaged in combat in "Footfall?"
Indeed he has.
But he just wants to be as scientifically accurate as
possible. Does the blast crumple the side of the
ship like a tin-can, or do all the hull seams
spring leaks, or what?
lal_truckee
For a miss, even a near miss, I'd think blast effect would be quite
small - there's nothing to create overpressure except the gas
representing the original device's mass, which goes to zero effective
density pretty quickly as it expands. The blast effects from an air or
ground burst are primarily created by former air and dirt become plasma
(soon superheated gas) expanding. For a contact burst the shock effect
would depend on how much of the ship was inside the nuclear fireball
radius and itself turned to blast contributing plasma.
However a properly designed space weapon would I suspect be radiation
enhanced - the fast neutrons would kill off the occupants miserably in a
few hours which would be sufficient for real space warfare which of
course occurs at great distances and over days and maybe weeks. Blast is
not the goal of a space weapon, except in SF.
If what is required for the SF plot is physical damage, a bunch of
ballbearings placed in retrograde orbit (relative to the target) is the
way to go. Or maybe ballbearings glued onto pusher-plates surrounding
the device - sort of a mini omnidirectional "Orion device" - would fit
the need for physical damage in a SF spaceship battle.
Mark L. Fergerson
> Nyrath wrote:
>
>> lal_truckee wrote:
>>
>>> I suppose Mr. Taylor has read Niven/Pournelle's version of an Orion
>>> drive battleship engaged in combat in "Footfall?"
>>
>>
>> Indeed he has.
>> But he just wants to be as scientifically accurate as
>> possible. Does the blast crumple the side of the
>> ship like a tin-can, or do all the hull seams
>> spring leaks, or what?
I'd think this largely depends on the ship's construction details, in
view of the below.
> For a miss, even a near miss, I'd think blast effect would be quite
> small - there's nothing to create overpressure except the gas
> representing the original device's mass, which goes to zero effective
> density pretty quickly as it expands. The blast effects from an air or
> ground burst are primarily created by former air and dirt become plasma
> (soon superheated gas) expanding. For a contact burst the shock effect
> would depend on how much of the ship was inside the nuclear fireball
> radius and itself turned to blast contributing plasma.
IOW the expanding gases either nudge the ship to one side more or
less gently, or eat part of it and heave the rest away? OTOH this kinda
assumes the ship is equally stressed for accelerations in all
directions, doesn't it? That sounds somewhat unrealistic for an Orion. A
side-on burst should do more (though still little) crumple/leak damage
than an axis-on one. A burst under the thrust plate would be annoying if
not inconvenient, but hardly damaging. A nose-on burst should at least
blind much of the nav gear. FTM, how about EMP at any orientation?
> However a properly designed space weapon would I suspect be radiation
> enhanced - the fast neutrons would kill off the occupants miserably in a
> few hours which would be sufficient for real space warfare which of
> course occurs at great distances and over days and maybe weeks. Blast is
> not the goal of a space weapon, except in SF.
Well, neutron flux decreases inverse-square, no? How much water
tankage/polyethylene slabs/etc. to stop it at distances outside nudge
range? I'd think the prompt gamma would be more worrisome.
Mr. Taylor should read Carey Sublette's nuke FAQ:
http://nuclearweaponarchive.org/
especially this:
http://nuclearweaponarchive.org/Nwfaq/Nfaq5.html
which details damage "opportunuties" from nukes.
> If what is required for the SF plot is physical damage, a bunch of
> ballbearings placed in retrograde orbit (relative to the target) is the
> way to go. Or maybe ballbearings glued onto pusher-plates surrounding
> the device - sort of a mini omnidirectional "Orion device" - would fit
> the need for physical damage in a SF spaceship battle.
There's always rapid-fire railguns. Or the infamous one-shot
nuke-powered X-ray laser...
Mark L. Fergerson
Nyrath
> For a miss, even a near miss, I'd think blast effect would be quite
> small - there's nothing to create overpressure except the gas
> representing the original device's mass, which goes to zero effective
> density pretty quickly as it expands. The blast effects from an air or
> ground burst are primarily created by former air and dirt become plasma
> (soon superheated gas) expanding. For a contact burst the shock effect
> would depend on how much of the ship was inside the nuclear fireball
> radius and itself turned to blast contributing plasma.
Yes, he is using information I have scraped together from
rec.arts.sf.science and placed here:
http://www.projectrho.com/rocket/rocket3x.html#nuke
The concept is that a nuclear detonation in space will
produce zero blast effects since that requires an
atmosphere (i.e., the blast is air superheated by
the x-ray flux).
So the blast will basically be an incredibly bright
point source of x-rays.
1e8 watts per square centimeter of x-rays delivered in
one microsecond will melt a bit of an aluminum hull.
1e9 watts per square centimeter of x-rays delivered in
one microsecond will vaporize a bit of an aluminum hull.
1e11 watts per square centimeter of x-rays delivered in
one microsecond will vaporize a bit of an aluminum hull.
It will vaporize it at a rate faster than the speed of
sound, and consequently will cause impulsive shock damage.
What Mr. Taylor is interested in is what does
Derek Lyons
>A gentleman named Rhys Taylor is making a short movie clip
>depicting Orion drive battleship engaged in combat.
>A short sample is here:
>http://rhysy.plexersoft.com/Deep%20Space%20Force%20Gallery/US%20test.avi
>
>He has a question. What will the combat damage look like?
His ships won't survive long enough to experience battle damage -
their own drives will save the the enemy the trouble of purchasing and
expending ordinance.
D.
--
Touch-twice life. Eat. Drink. Laugh.
-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL
Derek Lyons
>A gentleman named Rhys Taylor is making a short movie clip
>depicting Orion drive battleship engaged in combat.
>A short sample is here:
>http://rhysy.plexersoft.com/Deep%20Space%20Force%20Gallery/US%20test.avi
>
>He has a question. What will the combat damage look like?
His ships won't survive long enough to experience battle damage -
their own drives will save the the enemy the trouble of purchasing and
expending ordinance.
From the gentlemans' email as quoted by Nyrath:
> Everything here will be physically and technologically sound.
His ship designs fail that criteria.
Luke Campbell
Nyrath wrote:
> http://www.projectrho.com/rocket/rocket3x.html#nuke
> > 1e8 watts per square centimeter for about a microsecond will melt
> > part of the surface of a sheet of aluminum. 1e9 W/cm2 for a
> > microsecond will vaporize the surface, and 1e11 W/cm2 for a
> > microsecond will cause enough vaporization to create impulsive shock
> > damage (i.e., the surface layer of the material is vaporized at a
> > rate exceeding the speed of sound).
>From Lasers and Thier Practical Applications (quoting from memory, the
book is at work, but I'm pretty sure I've remembered the figures
right): condensed matter undergoes impulsive shock vaporization at
irradiences of 1E9 to 1E10 W/cm^3, your figure may be off by one or two
orders of magnitude. Of course, this is considering near IR and
visible radiation - the extra penetrating depth of the nuke's soft
x-rays could increase the necessary irradience.
> > So what's actually seen visually, i.e. what does impulsive shock
> > damage look like ? I figure the kiloton bombs will only be launched
> > from the cannons, and I guess they'd blast a bloody great hole in the
> > side of the ship but not actually destroy it. The larger ones
> > launched from silos could be >~100 megatons - would these entirely
> > vapourise a ship (or at least blast it into such small fragments that
> > it would look the same), turn it into a great molten lump of metal,
> > or just smash it into several large fragments ?
>
> Anyone have some insights?
First, consider a uniform slab of material subject to uniform
irradiation suffient to cause an impulsive shock. A thin layer will be
vaporized and a planar shock will propagate into the material.
Assuming that the shock is not too intense (i.e., not enough heat is
dumped into the slab to vaporize or melt it) there will be no material
damage because of the planar symmetry. However, as the shock reaches
the back side of the slab, it will be reflected. This will set up
stresses on the rear surface, which tends to cause peices of the rear
surface to break off and fly away at velocities close to the shock wave
velocity (somewhat reduced, of course, due to the binding energy of all
those chemical bonds you need to break in order to spall off that
piece). This spallation can cause significant problems to objects that
don't have anything separating them from the hull. Modern combat
vehicles take pains to protect against spallation for just this reason
(using an inner layer of kevlar or some such).
Now, if the material or irradiance is non-uniform, there will be
stresses set up inside the hull material. If these exceed the strength
of the material, the hull will deform or crack. This can cause
crumpling, rupturing, denting (really big dents), or shattering
depending on the material and the shock intensity.
For a sufficiently intense shock, shock heating will melt or vaporize
the hull material, with obvious catastrophic results. At higher
intensities, the speed of radiation diffusion of the nuke x-rays can
exceed the shock speed, and the x-rays will vaporize the hull before
the shock can even start. Roughly speaking, any parts of the hull
within the diameter of an atmospheric fireball will be subject to this
effect.
In any event, visually you would see a bright flash from the surface
material that is heated to incandescence. The flash would be sudden,
only if the shock is so intense as to cause significant heating would
you see any extra light for more than one frame of the animation (if
the hull material is heated, you can show it glowing cherry red or
yellow hot or what have you). The nuke itself would create a similar
instant flash. There would probably be something of an afterglow from
the vaporized remains of the nuke and delivery system, but it will be
expanding in a spherical cloud so quickly I doubt you would be able to
see it. Shocks in rigid materials tend to travel at something like 10
km/s, shock induced damage would likewise be immediate. Slower effects
could occur as the air pressure inside blasts apart the weakened hull
or blows out the shattered chunks, or as transient waves propagate
through the ship's structure, or when structural elements are loaded so
as to shatter normally rather than through the shock. Escaping air
could cause faintly visible jets as moisture condenses/freezes out -
these would form streamers shooting away from the spacecraft at close
to the speed of sound in air - NO billowing clouds.
I hope this helps.
Luke
Luke Campbell
lal_truckee wrote:
> For a miss, even a near miss, I'd think blast effect would be quite
> small - there's nothing to create overpressure except the gas
> representing the original device's mass, which goes to zero effective
> density pretty quickly as it expands. The blast effects from an air or
> ground burst are primarily created by former air and dirt become plasma
> (soon superheated gas) expanding.
As others have noted, the primary danger in space is not from the
"blast" (or rather the rapidly expanding shell of vaporized nuke and
delivery system) but from the pulse of soft x-rays which can push or
smash solid objects through rapid vaporization of a surface layer.
> For a contact burst the shock effect
> would depend on how much of the ship was inside the nuclear fireball
> radius and itself turned to blast contributing plasma.
Just to clear up any confusion, in space there is no fireball per se.
The fireball is a result of radiation diffusion through the air - the
x-rays are absorbed, heat up a layer of air to temperatures high enough
to emit more x-rays, and that heats the next layer of air, and so on,
resulting in an expanding sphere of incandescent air. In space there
is no air to form the fireball. I am not sure if you knew this or not,
but other people might be confused.
Luke
Steve Hix
fair...@gmail.com (Derek Lyons) wrote:
> Nyrath <nyr...@projectrho.com.INVALID> wrote:
>
> >A gentleman named Rhys Taylor is making a short movie clip
> >depicting Orion drive battleship engaged in combat.
> >A short sample is here:
> >http://rhysy.plexersoft.com/Deep%20Space%20Force%20Gallery/US%20test.avi
> >
> >He has a question. What will the combat damage look like?
>
> His ships won't survive long enough to experience battle damage -
> their own drives will save the the enemy the trouble of purchasing and
> expending ordinance.
>
> From the gentlemans' email as quoted by Nyrath:
>
> > Everything here will be physically and technologically sound.
>
> His ship designs fail that criteria.
Now, for extra points, you get to explain *why*.
Nyrath
> In any event, visually you would see a bright flash from the surface
> material that is heated to incandescence. The flash would be sudden,
> only if the shock is so intense as to cause significant heating would
> you see any extra light for more than one frame of the animation (if
> the hull material is heated, you can show it glowing cherry red or
> yellow hot or what have you). The nuke itself would create a similar
> instant flash. There would probably be something of an afterglow from
> the vaporized remains of the nuke and delivery system, but it will be
> expanding in a spherical cloud so quickly I doubt you would be able to
> see it. Shocks in rigid materials tend to travel at something like 10
> km/s, shock induced damage would likewise be immediate. Slower effects
> could occur as the air pressure inside blasts apart the weakened hull
> or blows out the shattered chunks, or as transient waves propagate
> through the ship's structure, or when structural elements are loaded so
> as to shatter normally rather than through the shock. Escaping air
> could cause faintly visible jets as moisture condenses/freezes out -
> these would form streamers shooting away from the spacecraft at close
> to the speed of sound in air - NO billowing clouds.
>
> I hope this helps.
Thank you! That is *exactly* what I was looking for.
John Schilling
wrote:
>A gentleman named Rhys Taylor is making a short movie clip
>depicting Orion drive battleship engaged in combat.
>A short sample is here:
>http://rhysy.plexersoft.com/Deep%20Space%20Force%20Gallery/US%20test.avi
>
>He has a question. What will the combat damage look like?
>
>He read the following from my website:
>
>http://www.projectrho.com/rocket/rocket3x.html#nuke
>> 1e8 watts per square centimeter for about a microsecond will melt
>> part of the surface of a sheet of aluminum. 1e9 W/cm2 for a
> > microsecond will vaporize the surface, and 1e11 W/cm2 for a
> > microsecond will cause enough vaporization to create impulsive shock
>> damage (i.e., the surface layer of the material is vaporized at a
> > rate exceeding the speed of sound).
>
>
>and asked the following:
>> So what's actually seen visually, i.e. what does impulsive shock
> > damage look like ? I figure the kiloton bombs will only be launched
> > from the cannons, and I guess they'd blast a bloody great hole in the
>> side of the ship but not actually destroy it. The larger ones
> > launched from silos could be >~100 megatons - would these entirely
> > vapourise a ship (or at least blast it into such small fragments that
>> it would look the same), turn it into a great molten lump of metal,
> > or just smash it into several large fragments ?
>Anyone have some insights?
First off, the weapon itself. A nuclear explosion in space, will look
pretty much like a Very Very Bright flashbulb going off. The effects
are instantaneous or nearly so. There is no fireball. The gaseous
remains of the weapon may be incandescent, but they are also expanding
at about a thousand kilometers per second, so one frame after detonation
they will have disspiated to the point of invisibility. Just a flash.
The effects on the ship itself, those are a bit more visible. If you're
getting impulsive shock damage, you will by definition see hot gas boiling
off from the surface. Again, the effect is instantaneous, but this time
the vapor will expand at maybe one kilometer per second, so depending on
the scale you might be able to see some of this action. But don't blink;
it will be quick.
Next is spallation - shocks will bounce back and forth through the skin
of the target, probably tearing chunks off both sides. Some of these
may come off at mere hundreds of meters per second. And they will be
hot, red- or maybe even white-hot depending on the material.
To envision the appearance of this part, a thought experiment. Or, heck,
go ahead and actually perform it. Start with a big piece of sheet metal,
covered in a fine layer of flour and glitter. Shine a spotlight on it,
in an otherwise-dark room. Then whack the thing with a sledgehammer,
hard enough for the recoil to knock the flour and glitter into the air.
The haze of brightly-lit flour is your vaporized hull material, and
the bits of glitter are the spallation. Scale up the velocities as
needed, and ignore the bit where air resistance and gravity brings
everything to a halt.
Next, the exposed hull is going to be quite hot, probably close to the
melting point. So, dull red even for aluminum, brilliant white for
steel or titanium or most ceramics or composites. The seriously hot
layer will only be a millimeter or so thick, so it can cool fairly
quickly - a second or two for a thick metallic hull that can cool
by internal conduction, possibly as long as a minute for something
thin and/or insulating that has to cool by radiation.
After this, if the shock is strong enough, the hull is going to be
materially deformed. For this, take the sledgehammer from your last
thought experiment and give a whack to some tin cans. Depending on
how hard you hit them, and whether they are full or empty, you can
get effects ranging from mild denting at weak points, crushing and
tearing, all the way to complete obliteration with bits of tin-can
remnant and tin-can contents splattered across the landscape.
Again, this will be much faster in reality than in the thought
experiment. And note that a spacecraft will have *many* weak points
to be dented, fragile bits to be torn off, and they all get hit at
once. If the hull is of isogrid construction, which is pretty
common, you might see an intact triangular lattice with shallow
dents in between. Bits of antenna and whatnot, tumbling away.
Finally, secondary effects. Part of your ship is likely to be
pressurized, either habitat space or propellant tank. Coolant
and drinking water and whatnot, as well. With serious damage,
that stuff is going to vent to space. You can probably see this
happening (air and water and some propellants will freeze into
snow as they escape, BTW). You'll also see the reaction force
try to tumble the spacecraft, and if the spacecraft's attitude
control systems are working you'll see them try to fight back.
You might see fires, if reactive materials are escaping. But
not convection flames, of course. Diffuse jets of flame, or
possibly surface reactions. Maybe secondary explosions if
concentrations of reactive gasses are building up in enclosed
(more or less) spaces.
That's for shock effect from nuclear weapons in vacuum. Are
there other weapons at work in this hypothetical?
--
*John Schilling * "Anything worth doing, *
*Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" *
*Chief Scientist & General Partner * -13th Rule of Acquisition *
*White Elephant Research, LLC * "There is no substitute *
*schi...@spock.usc.edu * for success" *
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Nyrath
> That's for shock effect from nuclear weapons in vacuum. Are
> there other weapons at work in this hypothetical?
Thank you very much for your information!
Other weapons he is considering include
coilguns and lasers.
He also has retractable heat radiators,
those will glow dull red, correct?
I'm a little confused about that.
If the radiator has a temperature
of about 1600K, the online blackbody
spectrum view gives a color of
dull red.
http://www.shodor.org/refdesk/Resources/Models/BlackbodyRadiation/index.php
But if the heat (not temperature) of the radiator
is high enough, will not the radiative flux
be high enough that the human eye will perceive
it as a white glare? Or am I totally misinformed?
IsaacKuo
> He also has retractable heat radiators,
> those will glow dull red, correct?
> I'm a little confused about that.
> If the radiator has a temperature
> of about 1600K, the online blackbody
> spectrum view gives a color of
> dull red.
> But if the heat (not temperature) of the radiator
> is high enough, will not the radiative flux
> be high enough that the human eye will perceive
> it as a white glare? Or am I totally misinformed?
This is correct, but keep in mind that the temperature of
the radiators is practically the lower limit on the temperature
of whatever they're cooling. In particular, a power reactor
is going to depend upon a large gap between the reactor
core temperature and the radiator temperature. It's quite
a challenge to come up with reasonable radiators for high
power space weaponry (like lasers).
When I was considering concepts for Orion drive space
warfare, I assumed lasers capable enough to make
delicate radiator systems largely impractical. With
massive ablative Orion "battleships" armed with ablative
Orion "missileballs" and lasers, I couldn't come up
with a way to make traditional "eggshell" warships
competetive.
Such "battleships" didn't need sophisticated radiator
systems--they simply used the mass of their thick armor
hulls to absorb the heat. This is okay if the lasers are only
used very briefly--to knock out the other side's radiators or
delicate sensor systems. It's not enough for any sort of
sustained high power laser fire--like trying to defeat an
armored target by overheating it.
If any "battleships" are around, any sort of "eggshell"
warships or missiles would get eliminated by lasers quickly.
This just leaves other heavily armored "battleships" and
cannonball-like armored missiles. The missiles would have
nukes for maneuvering purposes, but not for damaging the
target--physically ramming the target makes more sense.
Still, coil guns might be useful for CIWS defenses. If you
can vaporize an incoming missile, then it wouldn't do
serious damage. If an armored missile stays in one piece
all the way to the target, then this might be as simple as
launching a single nuclear tipped defensive short range
missile. A coil gun could be suitable for launching such
an unarmored low velocity missile; the missile could
include some sideways chemical thrusters for terminal
maneuvering to get in the way of the incoming.
Plausibly, the offensive long range armored missiles could
counter with a chemical explosive warhead. This warhead
detonates outside of CIWS range to fragment the missile
into multiple chunks.
So basically, the relevant weapons systems/platforms
are:
Heavily armored spherical "battleships" armed with
long range lasers, medium range offensive missiles,
and short range defensive missiles. These 25+m
diameter behemoths are carved out of asteroid/moon
material, or some other relatively inexpensive bulk
material. They rely upon ablative Orion nukes for
propulsion. Most of the systems are concentrated
in a well protected central core, but there are also
tunnels for sensors and other systems to pop out of.
Long range lasers--I had assumed practical ranges
of perhaps 10,000km or much more, preventing any
"eggshell" warship or missiles from being a significant
threat to an armored battleship or fixed installation.
Medium range offensive missiles, which are spherical
"cannonballs" propelled and maneuvered by ablative
Orion nukes. Due to the way nukes and ablative Orion
scales down, these lack the Isp of the battleships.
Their smaller diameter means they're less survivable
against sustained laser fire. Thus, it makes sense for
them to be carried on larger "battleship" platforms rather
than simply operating independently from the start.
With a cruise velocity of perhaps 5-10km/s, they could
cross a thousand kilometers in minutes.
Short range defensive missiles, which are unarmored
"eggshell" missiles with high maneuverability chemical
thrusters. These are compact and lightweight compared
to the offensive missiles, and might be designed to
be launched by a "gun" of some type. With a "muzzle"
velocity of perhaps 1km/s, they can only be expected
to reach a few kilometers before enemy lasers knock
them out.
Once I had settled upon the above characteristics of the
"space battleships", I had difficulty coming up with
interesting alternative weapons platforms which could
plausibly compete.
Isaac Kuo
Logan Kearsley
news:1153498666....@i3g2000cwc.googlegroups.com...
> Nyrath wrote:
>
> > He also has retractable heat radiators,
> > those will glow dull red, correct?
> > I'm a little confused about that.
> > If the radiator has a temperature
> > of about 1600K, the online blackbody
> > spectrum view gives a color of
> > dull red.
>
> > But if the heat (not temperature) of the radiator
> > is high enough, will not the radiative flux
> > be high enough that the human eye will perceive
> > it as a white glare? Or am I totally misinformed?
>
> This is correct, but keep in mind that the temperature of
> the radiators is practically the lower limit on the temperature
> of whatever they're cooling. In particular, a power reactor
> is going to depend upon a large gap between the reactor
> core temperature and the radiator temperature. It's quite
> a challenge to come up with reasonable radiators for high
> power space weaponry (like lasers).
Oi? What about using refrigerators to raise the radiator temperature? That's
obviously unworkable for a power reactor, where you need the radiating
temperature to be much lower than the reactor temperature to get any energy
out, but part of said energy could be used to power refrigerators to
actively cool the lasers, armor, etc.
So, you could realistically have two separate sets of radiators, operating
at different temperatures (and colors)- one for the engine, one for
refrigeration.
-l.
------------------------------------
My inbox is a sacred shrine, none shall enter that are not worthy.
IsaacKuo
Logan Kearsley wrote:
>"IsaacKuo" <mec...@yahoo.com> wrote in message
>news:1153498666....@i3g2000cwc.googlegroups.com...
>>This is correct, but keep in mind that the temperature of
>>the radiators is practically the lower limit on the temperature
>>of whatever they're cooling. In particular, a power reactor
>>is going to depend upon a large gap between the reactor
>>core temperature and the radiator temperature. It's quite
>>a challenge to come up with reasonable radiators for high
>>power space weaponry (like lasers).
>Oi? What about using refrigerators to raise the radiator temperature? That's
>obviously unworkable for a power reactor, where you need the radiating
>temperature to be much lower than the reactor temperature to get any energy
>out, but part of said energy could be used to power refrigerators to
>actively cool the lasers, armor, etc.
Refrigeration could be used to lower the temperature of
some equipment which doesn't generate much heat.
This could be used to keep thermal sensors cool, and
possibly the crew compartment.
But using refrigeration to cool high power equipment
implies greatly increased power requirements and thus
greatly increased waste heat rejection capability. It's
a viscious feedback cycle which I don't find plausible
for high power equipment.
>So, you could realistically have two separate sets of radiators, operating
>at different temperatures (and colors)- one for the engine, one for
>refrigeration.
Yes, I could see something like that being used to keep
the crew compartment cool (I'm going to assume that by
"engine" you mean power reactor; an Orion drive doesn't
really have an "engine").
Now, there is the possibility that the power supply doesn't
require radiators, so that just leaves one set of radiators
to cool the crew compartment via refrigeration. For
example, electrical power might be supplied by an efficient
microwave beam receiver array. Or the power could be
supplied by some sort of self cooling "open" reactor, where
electricity is generated by efficient charged particle
interaction while the unused "waste" radiation/particles
vent directly into space.
Isaac Kuo
Logan Kearsley
That depends on how much you want to cool the high power equipment. I don't
think it would be at all plausible to try and keep gigawatt lasers at
room-temperature, for example, but it might be useful to be able to actively
keep them below some 'safety limit' temperature, or extend the time that
they can fire at a certain power level, or decrease the cool down time
between shots.
But, primarily I was thinking that, whatever you're cooling, it's useful to
run the radiators as hot as you possibly can, so as to make it harder for
the enemy to use their lasers to eliminate your heat-rejection capability.
>
> >So, you could realistically have two separate sets of radiators,
operating
> >at different temperatures (and colors)- one for the engine, one for
> >refrigeration.
>
> Yes, I could see something like that being used to keep
> the crew compartment cool (I'm going to assume that by
> "engine" you mean power reactor; an Orion drive doesn't
> really have an "engine").
Right.
> Now, there is the possibility that the power supply doesn't
> require radiators, so that just leaves one set of radiators
> to cool the crew compartment via refrigeration. For
> example, electrical power might be supplied by an efficient
> microwave beam receiver array. Or the power could be
> supplied by some sort of self cooling "open" reactor, where
> electricity is generated by efficient charged particle
> interaction while the unused "waste" radiation/particles
> vent directly into space.
True. So, that's another thing for the animator to consider- what kind of
power supply are the battleships using?
IsaacKuo
>>But using refrigeration to cool high power equipment
>>implies greatly increased power requirements and thus
>>greatly increased waste heat rejection capability. It's
>>a viscious feedback cycle which I don't find plausible
>>for high power equipment.
>That depends on how much you want to cool the high power equipment. I don't
>think it would be at all plausible to try and keep gigawatt lasers at
>room-temperature, for example, but it might be useful to be able to actively
>keep them below some 'safety limit' temperature, or extend the time that
>they can fire at a certain power level, or decrease the cool down time
>between shots.
I don't think that can work. Refrigeration increases
your overall heat rejection requirements, so I think
you'd actually decrease the amount of time you could
keep them firing rather than increasing the amount of
time.
>But, primarily I was thinking that, whatever you're cooling, it's useful to
>run the radiators as hot as you possibly can, so as to make it harder for
>the enemy to use their lasers to eliminate your heat-rejection capability.
This depends on how efficient the lasers are--or more
precisely, it depends on the ratio between laser output
and heat rejection requirements. The overall system
could actually be relatively inefficient but if most of
the wasted energy is directly vented out into space
then it's not a problem.
If you have very efficient lasers--lasers which generate
a lot of beam energy compared to the amount of heat
rejection required, then it may be possible to use
an "overheat the enemy" tactic. You could silence
the enemy's lasers by firing your own lasers continuously
at his radiators.
If you don't have very efficient lasers--there's a lot
of waste heat that must be rejected via a radiation
system--then it's not really plausible to silence an
enemy's lasers by overheating his radiators. You'd
sooner overheat your own radiators than the enemy's.
I tend to find the latter situation more plausible.
While lasers which efficiently turn electrical energy
into laser beams may be plausible, I tend to expect
efficient sources of electrical energy will not be
available. I mention the possibility of an "open"
reactor of some type--but this would be exposed and
vulnerable on the end of a boom or something. I
tend to expect that pulse lasers would knock out
such exposed equipment in no time.
OTOH, if everybody were in "eggshell" warships, then
a reactor on the end of a boom is no more vulnerable
than pretty much any other component of the ship.
>>Now, there is the possibility that the power supply doesn't
>>require radiators, so that just leaves one set of radiators
>>to cool the crew compartment via refrigeration. For
>>example, electrical power might be supplied by an efficient
>>microwave beam receiver array. Or the power could be
>>supplied by some sort of self cooling "open" reactor, where
>>electricity is generated by efficient charged particle
>>interaction while the unused "waste" radiation/particles
>>vent directly into space.
>True. So, that's another thing for the animator to
>consider- what kind of power supply are the battleships
>using?
Yes, the sort of power supply and heat rejection systems
can have as much of an impact on the overall apperance
and layout of the spacecraft as its propulsion system.
Isaac Kuo
Derek Lyons
>Shocks in rigid materials tend to travel at something like 10
>km/s, shock induced damage would likewise be immediate. Slower effects
>could occur as the air pressure inside blasts apart the weakened hull
>or blows out the shattered chunks, or as transient waves propagate
>through the ship's structure, or when structural elements are loaded so
>as to shatter normally rather than through the shock.
Do keep in mind that shocks below the level required to produce
material damage to the hull and structure are still a significant
hazard to the ship. The flexure of the hull and structures can
derange equipment and fixtures leading to a mission kill [1] (if not a
hard kill) even if the ship remains structurally sound.
Also, the irradiation can cause a variety of potentially bothersome
effects *without* significant shock. (Such as changing the color of
radiator surfaces or damaging the coating of optical elements.)
[1] It's often forgotten that ships can be knocked out of battle
without being completely destroyed.
Derek Lyons
>John Schilling wrote:
>> That's for shock effect from nuclear weapons in vacuum. Are
>> there other weapons at work in this hypothetical?
>
>Thank you very much for your information!
>
>Other weapons he is considering include coilguns and lasers.
>
>He also has retractable heat radiators, those will glow dull red,
>correct? I'm a little confused about that. If the radiator has a
>temperature of about 1600K, the online blackbody spectrum view
>gives a color of dull red.
Temporarily overheating the radiators can lead to some interesting
effects as well I suspect.
Logan Kearsley
>
> Logan Kearsley wrote:
> >"IsaacKuo" <mec...@yahoo.com> wrote in message
> >news:1153512234.4...@i3g2000cwc.googlegroups.com...
>
> >>But using refrigeration to cool high power equipment
> >>implies greatly increased power requirements and thus
> >>greatly increased waste heat rejection capability. It's
> >>a viscious feedback cycle which I don't find plausible
> >>for high power equipment.
>
> >That depends on how much you want to cool the high power equipment. I
don't
> >think it would be at all plausible to try and keep gigawatt lasers at
> >room-temperature, for example, but it might be useful to be able to
actively
> >keep them below some 'safety limit' temperature, or extend the time that
> >they can fire at a certain power level, or decrease the cool down time
> >between shots.
>
> I don't think that can work. Refrigeration increases
> your overall heat rejection requirements, so I think
> you'd actually decrease the amount of time you could
> keep them firing rather than increasing the amount of
> time.
It increases your overall heat rejection requirements, but improves heat
rejection from the laser mechanism itself. So, if the laser overheating puts
a limit on how long and/or how often you can fire, as it seems reasonable to
me would be the case with high power, relatively low-efficiency lasers
(except for chemical lasers that vent the lasing medium, but those have
problems of their own), being able to actively cool them would be an
advantage.
> >But, primarily I was thinking that, whatever you're cooling, it's useful
to
> >run the radiators as hot as you possibly can, so as to make it harder for
> >the enemy to use their lasers to eliminate your heat-rejection
capability.
>
> This depends on how efficient the lasers are--or more
> precisely, it depends on the ratio between laser output
> and heat rejection requirements. The overall system
> could actually be relatively inefficient but if most of
> the wasted energy is directly vented out into space
> then it's not a problem.
>
> If you have very efficient lasers--lasers which generate
> a lot of beam energy compared to the amount of heat
> rejection required, then it may be possible to use
> an "overheat the enemy" tactic. You could silence
> the enemy's lasers by firing your own lasers continuously
> at his radiators.
>
> If you don't have very efficient lasers--there's a lot
> of waste heat that must be rejected via a radiation
> system--then it's not really plausible to silence an
> enemy's lasers by overheating his radiators. You'd
> sooner overheat your own radiators than the enemy's.
Unless the enemy is also firing his not-very-efficient lasers, or running
other equipment that produces a lot of heat.
Although, in that case, the enemy could just shut everything off and wait.
You might not just be aiming to silence the enemy's lasers. You might be
trying to overheat the crew. Not sure if/how that would change the
situation.
> I tend to find the latter situation more plausible.
> While lasers which efficiently turn electrical energy
> into laser beams may be plausible, I tend to expect
> efficient sources of electrical energy will not be
> available. I mention the possibility of an "open"
> reactor of some type--but this would be exposed and
> vulnerable on the end of a boom or something. I
> tend to expect that pulse lasers would knock out
> such exposed equipment in no time.
Why would it have to be out on a boom? Why not have most of it protected
inside the ship, with just a vent open to the outside?
Maybe something like a hydrogen-boron "focus fusion" reactor
(http://www.focusfusion.org/index.html), although the particle beam that
produces really wouldn't carry away a whole lot of heat.
I don't know if anybody has surpassed it yet, but laser diodes have been
constructed with efficiencies of up to 71%. They have high divergence,
though. Possibly that could be fixed with a phased array and/or suitable
application of lenses.
I wonder what the limits are to FEL efficiency. The basic idea doesn't
necessarily have to use electrons- you might build a Free Proton Laser, or a
Free Alpha-Particle laser, so perhaps a "focus fusion" reactor could be
coupled directly to a wiggler to generate laser light instead of
electricity.
I wonder about particle beam efficiencies, too. Might it be more efficient,
in terms of energy delivered to the enemy compared to energy lost as heat,
to use particle beam weapons?
Paul F. Dietz
> Such "battleships" didn't need sophisticated radiator
> systems--they simply used the mass of their thick armor
> hulls to absorb the heat.
Per unit mass, you can absorb more heat with
an expendable coolant, particularly if that coolant
is hydrogen. Simply heating the coolant and dumping
it overboard from opposed nozzles will work, but you
can do even better by pressurizing the fluid, expanding
it isothermally to lower pressure, then expelling
it. The isothermal expansion converts some heat to work
and this energy can either drive weapons systems or just
be dumped overboard nonthermally (laser light, microwaves,
electron beam, arc heating of the expelled hydrogen after
the last heat exchanger, etc.)
Paul
Paul F. Dietz
> It's quite
> a challenge to come up with reasonable radiators for high
> power space weaponry (like lasers).
In a free elecron laser, the inefficiency in the laser itself
manifests as heating of the electron beam. So, just dump
the beam into space (along with some positive ions to balance
the charge.)
Paul
Nyrath
> This is correct, but keep in mind that the temperature of
> the radiators is practically the lower limit on the temperature
> of whatever they're cooling. In particular, a power reactor
> is going to depend upon a large gap between the reactor
> core temperature and the radiator temperature. It's quite
> a challenge to come up with reasonable radiators for high
> power space weaponry (like lasers).
Yes. A gentleman named Tony Valle started with
an equation for free energy using the Carnot efficiency,
did a lot of math I did not understand, and concluded
that the optimum heat exchanger is when the cold
side of the heat engine is at 75% of the hot side.
This is not efficient as a heat engine, but if the
total waste heat is dropped by lowering the
temperature of the cold side, the total
radiator area must be increased
(due to the T^4 behavior of the radiation law,
as the temperature of the radiator drops
it dumps heat much less efficiently).
If you want to check his math, go to
http://www.projectrho.com/rocket/rocket3e.html#radiator
and scroll down to the section that
starts with "Here is some scary math about radiators
from Tony Valle"
Nyrath
> Temporarily overheating the radiators can lead to some interesting
> effects as well I suspect.
It has been pointed out to me that a little known fact
about interplanetary combat is that the "Achilles Heel"
of combat spacecraft are the heat radiators.
Luke Campbell
Logan Kearsley wrote:
> I don't know if anybody has surpassed it yet, but laser diodes have been
> constructed with efficiencies of up to 71%. They have high divergence,
> though. Possibly that could be fixed with a phased array and/or suitable
> application of lenses.
Laser diodes have been made with efficiencies of 90%+. As you mention,
their beams are crap. No, lenses can't fix it, there's not enough beam
coherence there to work with.
> I wonder what the limits are to FEL efficiency. The basic idea doesn't
> necessarily have to use electrons- you might build a Free Proton Laser, or a
> Free Alpha-Particle laser, so perhaps a "focus fusion" reactor could be
> coupled directly to a wiggler to generate laser light instead of
> electricity.
Single pass FEL eficiencies are, if I remember correcly, something on
the order of 30%. This is not really relevant, though, since all
energy not extracted as coherent photons remains in the electron beam,
and all this electron kinetic energy can be easily recovered as
electrical energy using the same machinery that accelerated the beam in
the first place. For example, if you are using an electrostatic
accelerator, running the electron beam backwards through the
accelerator turns the electron beam energy into usable electricity
(that can be used to accelerate another electron beam, for example).
This has been demonstrated. A lot of people are even more excited by
using linacs to pump FELs, and then running the electron pulses through
the linac out of phase with the accelerating fields to recover the
energy. In this sense you get a near 100% "wallplug" efficiency at
turning electricity into laser beam energy.
Other charged particles are not very practical for free charged
particle lasers. Radiation occurs when a charged particle is
accelerated. Electrons have a very low mass compared to any other
charged particle, so for a given force, they are accelerated more, and
thus radiate more. In addition, because of their low mass, they go
faster (or, in the relativistic limit, have larger relativistic
effects), which is good for getting them to produce coherent radiation
beams.
The ever popular neodymnium lasers (such as the Nd:YAG workhorse of
moany modern machining lasers) have a quantum efficiency of on the
order of 90%. This means it is theoretically possible to get a
neodymnium laser to operate at close to 90% efficiency. Other effects
have limited the efficiency of real neodymnium lasers to closer to 10%
to 30% (if you want continuous beams, pulsed beam efficiencies are much
lower).
> I wonder about particle beam efficiencies, too. Might it be more efficient,
> in terms of energy delivered to the enemy compared to energy lost as heat,
> to use particle beam weapons?
Particle beams are nearly 100% efficient at turning electrical energy
into beam energy. They have other problems, though (such as a
difficulty keeping them tightly focused).
Logan Kearsley
news:1153532634....@s13g2000cwa.googlegroups.com...
>
> Logan Kearsley wrote:
>
> > I don't know if anybody has surpassed it yet, but laser diodes have been
> > constructed with efficiencies of up to 71%. They have high divergence,
> > though. Possibly that could be fixed with a phased array and/or suitable
> > application of lenses.
>
> Laser diodes have been made with efficiencies of 90%+. As you mention,
> their beams are crap. No, lenses can't fix it, there's not enough beam
> coherence there to work with.
What about phased arrays? AFAIK, the high divergence is a result of their
small size, but a phased array ought to be able to simulate a large
aperture, right?
> > I wonder what the limits are to FEL efficiency. The basic idea doesn't
> > necessarily have to use electrons- you might build a Free Proton Laser,
or a
> > Free Alpha-Particle laser, so perhaps a "focus fusion" reactor could be
> > coupled directly to a wiggler to generate laser light instead of
> > electricity.
>
> Single pass FEL efficiencies are, if I remember correctly, something on
> the order of 30%. This is not really relevant, though, since all
> energy not extracted as coherent photons remains in the electron beam,
> and all this electron kinetic energy can be easily recovered as
> electrical energy using the same machinery that accelerated the beam in
> the first place. For example, if you are using an electrostatic
> accelerator, running the electron beam backwards through the
> accelerator turns the electron beam energy into usable electricity
> (that can be used to accelerate another electron beam, for example).
> This has been demonstrated. A lot of people are even more excited by
> using linacs to pump FELs, and then running the electron pulses through
> the linac out of phase with the accelerating fields to recover the
> energy. In this sense you get a near 100% "wallplug" efficiency at
> turning electricity into laser beam energy.
Oo, excellent. And FELs are tunable, too. So, the net efficiency, and how
much waste heat you have to dump, will depend mainly on the accelerator
efficiency, and the wiggler electromagnet efficiency. You say below particle
beams are near 100% efficient, so that sounds pretty good.
I'm having a bit of trouble imagining how to set up the geometry for
recapturing the electron beam and recovering its energy. With electrostatic
accelerators, I imagine you could just have the whole thing in a straight
line, with one accelerator at each end and a hole in the 'nozzle' end for
the laser beam to emerge from, but that seems less practical for a linac.
> Other charged particles are not very practical for free charged
> particle lasers. Radiation occurs when a charged particle is
> accelerated. Electrons have a very low mass compared to any other
> charged particle, so for a given force, they are accelerated more, and
> thus radiate more. In addition, because of their low mass, they go
> faster (or, in the relativistic limit, have larger relativistic
> effects), which is good for getting them to produce coherent radiation
> beams.
So, using other particles requires stronger wiggler magnets. Obviously,
electrons are ideal, but I just wonder if there are cases (such as when you
can get a 'free' alpha particle beam out of a p-B11 fusion plasma) where it
might be useful to accommodate other particles.
> The ever popular neodymnium lasers (such as the Nd:YAG workhorse of
> moany modern machining lasers) have a quantum efficiency of on the
> order of 90%. This means it is theoretically possible to get a
> neodymnium laser to operate at close to 90% efficiency. Other effects
> have limited the efficiency of real neodymnium lasers to closer to 10%
> to 30% (if you want continuous beams, pulsed beam efficiencies are much
> lower).
>
> > I wonder about particle beam efficiencies, too. Might it be more
efficient,
> > in terms of energy delivered to the enemy compared to energy lost as
heat,
> > to use particle beam weapons?
>
> Particle beams are nearly 100% efficient at turning electrical energy
> into beam energy. They have other problems, though (such as a
> difficulty keeping them tightly focused).
Excellent. Using two accelerators side-by-side to produce a neutral particle
beam would help limit the divergence, but the average particle beam would
still probably have significantly higher divergence than the average laser.
On the other hand, particle beams can be much more penetrating, and produce
secondary radiation.
'Twould be interesting to work out under what circumstances each type of
weapon would be better. Lasers probably win for long range no matter what.
IsaacKuo
I'm less concerned about the waste energy of the laser
engine itself and more concerned about the waste energy
of the electrical power source feeding the laser engine.
An electrically powered high power space weapon is
only a high power space weapon if it's connected to a
high power electrical supply.
Isaac Kuo
IsaacKuo
Paul F. Dietz wrote:
>IsaacKuo wrote:
>>Such "battleships" didn't need sophisticated radiator
>>systems--they simply used the mass of their thick armor
>>hulls to absorb the heat.
>Per unit mass, you can absorb more heat with
>an expendable coolant, particularly if that coolant
>is hydrogen.
But you still get fewer shots overall, compared to
if you can wait for cycles of cooling down, and you've
expended your single use coolant.
The thick armor of a "battleship" serves duty as a
temporary heat sink only as a "bonus" function. Its
primary duties are ablative propellant and armor
protection. Using it for a temporary "heat battery"
doesn't reduce its functionality for the primary
purposes.
In contrast, even if an expendable coolant also
serves another function, using it as an expendable
coolant sacrifices its functionality for that other
function. For example, you might have a store of
water is used for propellant as well as crew
supplies. This could be used as an expendable
coolant, but doing so makes the expended coolant
unavailable for other purposes.
Isaac Kuo
Luke Campbell
Logan Kearsley wrote:
> "Luke Campbell" <lwc...@gmail.com> wrote in message
> news:1153532634....@s13g2000cwa.googlegroups.com...
> > Laser diodes have been made with efficiencies of 90%+. As you mention,
> > their beams are crap. No, lenses can't fix it, there's not enough beam
> > coherence there to work with.
>
> What about phased arrays? AFAIK, the high divergence is a result of their
> small size, but a phased array ought to be able to simulate a large
> aperture, right?
They would if it was the small aperture that was causing problems.
Instead, diode lasers just have terrible beam quality. They lase on
too many modes, with really poor beam coherance. Maybe someday we'll
be able to make a better diode laser. For today's tech, the main
applications for diodes as laser weapons are to pump solid state
neodymnium lasers.
> > > I wonder what the limits are to FEL efficiency. The basic idea doesn't
> > > necessarily have to use electrons- you might build a Free Proton Laser,
> or a
> > > Free Alpha-Particle laser, so perhaps a "focus fusion" reactor could be
> > > coupled directly to a wiggler to generate laser light instead of
> > > electricity.
> >
> > Single pass FEL efficiencies are, if I remember correctly, something on
> > the order of 30%. This is not really relevant, though, since all
> > energy not extracted as coherent photons remains in the electron beam,
> > and all this electron kinetic energy can be easily recovered as
> > electrical energy using the same machinery that accelerated the beam in
> > the first place. For example, if you are using an electrostatic
> > accelerator, running the electron beam backwards through the
> > accelerator turns the electron beam energy into usable electricity
> > (that can be used to accelerate another electron beam, for example).
> > This has been demonstrated. A lot of people are even more excited by
> > using linacs to pump FELs, and then running the electron pulses through
> > the linac out of phase with the accelerating fields to recover the
> > energy. In this sense you get a near 100% "wallplug" efficiency at
> > turning electricity into laser beam energy.
>
> Oo, excellent. And FELs are tunable, too. So, the net efficiency, and how
> much waste heat you have to dump, will depend mainly on the accelerator
> efficiency, and the wiggler electromagnet efficiency. You say below particle
> beams are near 100% efficient, so that sounds pretty good.
Yeah, like I said, you get better than 99% wallplug efficiency.
> I'm having a bit of trouble imagining how to set up the geometry for
> recapturing the electron beam and recovering its energy. With electrostatic
> accelerators, I imagine you could just have the whole thing in a straight
> line, with one accelerator at each end and a hole in the 'nozzle' end for
> the laser beam to emerge from, but that seems less practical for a linac.
Here's a link for a typical energy recovery linac geometry.
http://erl.chess.cornell.edu/
These things are being built now (and some have already been built) to
get x-ray free electron lasers for materials research. Note that if
you put the electron bunch back into the linac in phase with the
accelerating RF fields, you can re-accelerate it rather than decelerate
in to recover its energy. The reason this avenue is not pursued in
modern research is that after many passes, the electron bunches tend to
spread out. You end up with nanosecond long x-ray pulses rather than
fempto- or attosecond long x-ray pulses, meaning less intensity and
lower time resolution (nanoseconds does not let you resolve atomic
motion).
> > Other charged particles are not very practical for free charged
> > particle lasers. Radiation occurs when a charged particle is
> > accelerated. Electrons have a very low mass compared to any other
> > charged particle, so for a given force, they are accelerated more, and
> > thus radiate more. In addition, because of their low mass, they go
> > faster (or, in the relativistic limit, have larger relativistic
> > effects), which is good for getting them to produce coherent radiation
> > beams.
>
> So, using other particles requires stronger wiggler magnets. Obviously,
> electrons are ideal, but I just wonder if there are cases (such as when you
> can get a 'free' alpha particle beam out of a p-B11 fusion plasma) where it
> might be useful to accommodate other particles.
For a particle of velocity v, charge e and relativistic factor gamma,
the radiation from acceleration perpendicular to the direction of
motion is proportional to e^2 gamma^4 v^2. For a given energy E and
mass m, gamma=E/(m c^2) where c is the speed of light in vacuum.
Because of the mass factor, you can already see that proton radiation
will be decreased by a factor of 16E+12. Fusion applications tend to
use particles in the keV range, which is not only low energy but well
into the non-relativistic limit for alpha particles (so v << c). These
factors tend to pretty much kill the raidation from anything other than
electrons.
> > > I wonder about particle beam efficiencies, too. Might it be more
> efficient,
> > > in terms of energy delivered to the enemy compared to energy lost as
> heat,
> > > to use particle beam weapons?
> >
> > Particle beams are nearly 100% efficient at turning electrical energy
> > into beam energy. They have other problems, though (such as a
> > difficulty keeping them tightly focused).
>
> Excellent. Using two accelerators side-by-side to produce a neutral particle
> beam would help limit the divergence, but the average particle beam would
> still probably have significantly higher divergence than the average laser.
The main limiting factor is that when the heavy charged particle
recombines with an electron, the electrostatic attraction of the
electron gives the particle a "kick" during the recombination process.
This adds random motion, i.e., heat, to the beam. For a proton beam,
conservation of energy indicates that you get a heat of 13.6 eV (the
binding energy of hydrogen) per particle. Since it is late, I'll let
someone else work through the math on the beam divergence this gives,
but I recall it is pretty significant.
> On the other hand, particle beams can be much more penetrating, and produce
> secondary radiation.
A free electron laser pumped by a linac has no problem generating
x-rays. If you can get good hard x-ray optics, you can get a beam of
highly penetrating radiation. Admittedly, they will not be as
penetrating as a beam of 50 GeV hydrogen atoms, but with diffraction
limited optics you could be killing other spacecraft across the solar
system. The big problem I see is getting diffraction limited optics.
> 'Twould be interesting to work out under what circumstances each type of
> weapon would be better. Lasers probably win for long range no matter what.
They have in all the scenarios I've ever worked, or seen worked, unless
you severely limit laser technology (to, say, mid IR chemical lasers or
some such).
Eivind Kjorstad
> I don't think that can work. Refrigeration increases
> your overall heat rejection requirements, so I think
> you'd actually decrease the amount of time you could
> keep them firing rather than increasing the amount of
> time.
I'm not so sure...
If you assume your radiators are black-body radiators, then amount
radiated goes up with the T^4 (where the temerpature is measured in Kelvin)
In the absense of active heat-transport (aka heat-pump, refrigeration)
your radiators will be *cooler* than your lasers.
If your lasers can tolerate operating at oh, say 1000K, and you somehow,
magically manage to couple them so well to the radiator that the
radiator reaches 950K, then the radiators will manage to rid you of
45KW/m^2
If you use an active heat-pump, and say pump sufficient heat to make
your radiators 1050K (50K more than the lasers instead of 50K less) then
the heat radiated goes up to 69KW/m^2
The latter is about 55% more than the former. So, it's a win assuming
the heat-pump needed consumes less than half a GW.
I have no idea if 1000K is a reasonable figure for the max
operating-temperature of a laser. Substitute your own number if you want.
It'd probably be reasonable to use an internal heat-storage aditionally,
to pick up spikes in heat-production and/or being able to continue
figthing for a limited time with radiators destroyed. Ice would work.
When out of combat, use the radiators to freeze water. When in combat
and radiators are down, dump the heat into the ice to melt it.
Eivind Kjørstad
Paul F. Dietz
>>'Twould be interesting to work out under what circumstances each type of
>>weapon would be better. Lasers probably win for long range no matter what.
>
>
> They have in all the scenarios I've ever worked, or seen worked, unless
> you severely limit laser technology (to, say, mid IR chemical lasers or
> some such).
Maybe spacecraft would be mostly beam poweered? Have large stationary lasers
sending beams across the solar system to the ships. The ships have large,
light collectors, powering smaller beam weapons that can focus a more intense
beam at shorter distances.
One interesting thing you can do with lasers is cool with them. That is,
if you have an external source of laser light, it can refrigerate an object
by anti-Stokes scattering off resonant scatterers. This has been demonstrated
in the lab with rare earth ions in some exotic glasses. Perhaps this is
a solution to the spacecraft cooling problem?
Paul
Luke Campbell
Paul F. Dietz wrote:
> Luke Campbell wrote:
>
> >>'Twould be interesting to work out under what circumstances each type of
> >>weapon would be better. Lasers probably win for long range no matter what.
> >
> >
> > They have in all the scenarios I've ever worked, or seen worked, unless
> > you severely limit laser technology (to, say, mid IR chemical lasers or
> > some such).
>
> Maybe spacecraft would be mostly beam poweered? Have large stationary lasers
> sending beams across the solar system to the ships. The ships have large,
> light collectors, powering smaller beam weapons that can focus a more intense
> beam at shorter distances.
A couple thoughts pop up about this. The first is that if you match
the bandgap of your photocell material to the wavelength of the laser
light, you can get remarkable efficiency at turning light to
electricity. I seem to recall a figure of around 80% mentioned for a
photocell that was actually built, but that was years ago and I have no
hard references, so don't rely on that figure.
Second, if you want to get beam weapons with this scenario, you can use
a big mirror to collect and refocus the light. Now there is no need to
convert light to electricity and then back to light again. It might
also make sense to use your mirror to concentrate the light on a small
array of high efficiency photocells, since those sorts of photocells
tent to be pricey and you might not want to pay for huge panels of
them.
> One interesting thing you can do with lasers is cool with them. That is,
> if you have an external source of laser light, it can refrigerate an object
> by anti-Stokes scattering off resonant scatterers. This has been demonstrated
> in the lab with rare earth ions in some exotic glasses. Perhaps this is
> a solution to the spacecraft cooling problem?
For a while, I tried to come up with a way to use laser cooling and
trapping to cool and focus neutral particle beams for use as long range
space beam weapons. I never came up with much that was practical, but
maybe it can be done.
The use of a laser to cool a spacecraft is interesting. Instead of
waiting for spontaneous radiation to cool you off, you can exchange
your heat with a high intensity beam. My guess would be that you would
focus the laser into antiparallel propagating beams (perhaps along the
three cartesian axes) across a cell of gas with an absorption resonance
just above the laser frequency, and use the "optical molasses"
technique to cool the gas. This gas, would, of course, also be the
working fluid for a heat exchanger with the hot parts of the
spacecraft.
Note that this would not solve the stealth in space issue that is often
associated with the heating issue - you would be glowing very brightly
from the scattered laser light. You can't intercept the laser light to
prevent it from being detected, because then you'd be getting all that
heat back, plus much much more heat from the absorption of the beam
itself. The best you could do would be to reflect the beam in a known
safe direction. Since your scattered light is no longer coherant or
directional, you are stuck with using imaging optics for focusing it
into a beam, with all the attendant problems thereof.
This would require a lot of laser power for a modest amount of cooling.
The laser light is only going to be scattered into a narrow band of
frequencies near the original frequency, with at best a random
direction. This does not give a whole lot of microstates to work with,
so you will not be able to carry off much entropy (the best case
scenario, of course, is for the laser to absorb enough entropy to
attain a thermal distribution, in which case it would probably work
quite well). Note that this does not invalidate the concept! If large
groundside or orbital high power laser stations are cheap, it may still
be worthwhile.
Logan Kearsley
I'm reminded of the 'refrigerator laser' from _Sundiver_.
By this method, you don't end up with a coherent beam of light to shoot
off, but you do end up with a restricted window of frequencies. I
wonder if it might be at all useful in something like a _Sundiver_
situation, where the ship is immersed in some medium, to act as a heat
pump or to tune your radiating frequencies so that as much of the
radiation as possible avoids getting absorbed right close to the ship.
-l.
Luke Campbell
Logan Kearsley wrote:
> I'm reminded of the 'refrigerator laser' from _Sundiver_.
> By this method, you don't end up with a coherent beam of light to shoot
> off, but you do end up with a restricted window of frequencies. I
> wonder if it might be at all useful in something like a _Sundiver_
> situation, where the ship is immersed in some medium, to act as a heat
> pump or to tune your radiating frequencies so that as much of the
> radiation as possible avoids getting absorbed right close to the ship.
I'd think (though I haven't done the math) that if you are limited to
onboard energy sources, a normal heat pump will beat laser cooling
every time. This is because when you can reach thermal equilibrium
with the hot/cold reservoir, you have a much larger set of microstates
available, and can thus dump much more entropy. Thermal equilibrium
is, by definition, when you have maximal access to all the available
microstates in the system.
For those who don't already know, the Sundiver laser refirgerator will
not work. An ideal laser beam has zero entropy (real lasers have a
vanishingly small entropy) and is thus unable to remove entropy (and
thus heat) from the system. You have to do /something/ to transfer
entropy from the system to the laser beam (at which point you get an
incoherent beam that is most probably going in all directions, and is
less monochromatic than before. Not much like a laser, is it?).
Logan Kearsley
> Logan Kearsley wrote:
> > "Luke Campbell" <lwc...@gmail.com> wrote in message
> > news:1153532634....@s13g2000cwa.googlegroups.com...
>
Reading over Nyrath's useful site, I see a claim of 65% maximum
efficiency for FELs. I presume that's for single-pass.
> > I'm having a bit of trouble imagining how to set up the geometry for
> > recapturing the electron beam and recovering its energy. With electrostatic
> > accelerators, I imagine you could just have the whole thing in a straight
> > line, with one accelerator at each end and a hole in the 'nozzle' end for
> > the laser beam to emerge from, but that seems less practical for a linac.
>
> Here's a link for a typical energy recovery linac geometry.
> http://erl.chess.cornell.edu/
Ah. So the return loop is much larger than the wiggler bit that
actually generates the laser beam. It would be nice to have something a
bit more compact, but if you just bend the beam sharply back around,
you'll have losses to synchrotron radiation. I wonder if you *could*
put a second linac after the wiggler and have the beam shine through
it, or is that as impractical as I first thought?
> These things are being built now (and some have already been built) to
> get x-ray free electron lasers for materials research. Note that if
> you put the electron bunch back into the linac in phase with the
> accelerating RF fields, you can re-accelerate it rather than decelerate
> in to recover its energy. The reason this avenue is not pursued in
> modern research is that after many passes, the electron bunches tend to
> spread out. You end up with nanosecond long x-ray pulses rather than
> fempto- or attosecond long x-ray pulses, meaning less intensity and
> lower time resolution (nanoseconds does not let you resolve atomic
> motion).
That probably wouldn't be much of an issue for weaponized FEL beams.
Could you get better efficiency by re-accelerating a previously used
bunch of electrons, than by decelerating them and putting their
left-over energy into a new group?
Presumably the military has so far been mainly interested in chemical
lasers instead of FELs for portability reasons?
> > > Other charged particles are not very practical for free charged
> > > particle lasers. Radiation occurs when a charged particle is
> > > accelerated. Electrons have a very low mass compared to any other
> > > charged particle, so for a given force, they are accelerated more, and
> > > thus radiate more. In addition, because of their low mass, they go
> > > faster (or, in the relativistic limit, have larger relativistic
> > > effects), which is good for getting them to produce coherent radiation
> > > beams.
> >
> > So, using other particles requires stronger wiggler magnets. Obviously,
> > electrons are ideal, but I just wonder if there are cases (such as when you
> > can get a 'free' alpha particle beam out of a p-B11 fusion plasma) where it
> > might be useful to accommodate other particles.
>
> For a particle of velocity v, charge e and relativistic factor gamma,
> the radiation from acceleration perpendicular to the direction of
> motion is proportional to e^2 gamma^4 v^2. For a given energy E and
> mass m, gamma=E/(m c^2) where c is the speed of light in vacuum.
> Because of the mass factor, you can already see that proton radiation
> will be decreased by a factor of 16E+12. Fusion applications tend to
> use particles in the keV range, which is not only low energy but well
> into the non-relativistic limit for alpha particles (so v << c). These
> factors tend to pretty much kill the raidation from anything other than
> electrons.
Aha. Never mind about free-other-particle lasers, then.
> > > > I wonder about particle beam efficiencies, too. Might it be more
> > efficient,
> > > > in terms of energy delivered to the enemy compared to energy lost as
> > heat,
> > > > to use particle beam weapons?
> > >
> > > Particle beams are nearly 100% efficient at turning electrical energy
> > > into beam energy. They have other problems, though (such as a
> > > difficulty keeping them tightly focused).
> >
> > Excellent. Using two accelerators side-by-side to produce a neutral particle
> > beam would help limit the divergence, but the average particle beam would
> > still probably have significantly higher divergence than the average laser.
>
> The main limiting factor is that when the heavy charged particle
> recombines with an electron, the electrostatic attraction of the
> electron gives the particle a "kick" during the recombination process.
> This adds random motion, i.e., heat, to the beam. For a proton beam,
> conservation of energy indicates that you get a heat of 13.6 eV (the
> binding energy of hydrogen) per particle. Since it is late, I'll let
> someone else work through the math on the beam divergence this gives,
> but I recall it is pretty significant.
According to Nyrath's site, thermal dispersion is less than
electrostatic, approximately 1 to 4 microradians. I dunno what the
basis of that estimate is, though. I'll have to try and work it out
exactly at some point- it'll depend on the average transverse velocity
associated with the thermal energy added during neutralization, and the
forward velocity applied by the accelerators.
> > On the other hand, particle beams can be much more penetrating, and produce
> > secondary radiation.
>
> A free electron laser pumped by a linac has no problem generating
> x-rays. If you can get good hard x-ray optics, you can get a beam of
> highly penetrating radiation. Admittedly, they will not be as
> penetrating as a beam of 50 GeV hydrogen atoms, but with diffraction
> limited optics you could be killing other spacecraft across the solar
> system. The big problem I see is getting diffraction limited optics.
-l.
Luke Campbell
Logan Kearsley wrote:
> Ah. So the return loop is much larger than the wiggler bit that
> actually generates the laser beam. It would be nice to have something a
> bit more compact, but if you just bend the beam sharply back around,
> you'll have losses to synchrotron radiation. I wonder if you *could*
> put a second linac after the wiggler and have the beam shine through
> it, or is that as impractical as I first thought?
Sure, but there's no need to have the laser beam shine through the
linac. Just bend the electron beam a bit as is goes out of the wiggler
(this would be pretty standard on FELs susing a resonating chamber,
anyway, although x-ray FELs don't use a resonator). This scheme is
very similar to what I've seen for electrostatic FELs - accelerate the
electrons up to the high voltage region, run them through the wiggler,
then as they return to lower voltage you get their energy back.
> That probably wouldn't be much of an issue for weaponized FEL beams.
> Could you get better efficiency by re-accelerating a previously used
> bunch of electrons, than by decelerating them and putting their
> left-over energy into a new group?
Since you get around 99% efficiency either way, it probably wouldn't
matter much. For many weapons applications, an ultra-short, high
powered pulse might be exactly what is wanted. Both nanosecond and
hundereds of femptosecond long pulses can cause impulsive shocking, but
several picosecond to several hundered femptosecond pulses are
apparently better at turning light energy into mechanical damage. This
may be less of an issue with x-ray beams, however. For propagation in
atmosphere, you can do some interesting things with self focused beams,
which may mean picosecond or shorter pulses (you probably wouldn't want
it self focused for a long distance, but you could "chirp" the beam so
that the atmosphere compresses the wavefront to self focusing power
levels just before the pulse reaches its target).
> Presumably the military has so far been mainly interested in chemical
> lasers instead of FELs for portability reasons?
There is still active research on naval FELs. A Popular Science
magazine a few months ago had an article on recent military FEL
research. So far, chemical lasers have had the edge because they have
had demonstrated continuous high power output in the megawatt range -
something you don't get yet with other laser types (although solid
state lasers are approaching this performance). Solid state and free
electron lasers have the really big advantage over chemical lasers in
that they can achieve kills for only several cents per shot (the cost
of electricity) rather than thousands of dollars per shot (the cost of
exotic reactive chemicals). That's the reason the military gave for
not deploying the MTHEL, a demonstrated field deployable chemical laser
with a proven record of shooting down rockets, artillery projectiles,
and mortar shells. A couple thousand dollars is a small price to pay
for shooting down an ICBM in boost phase to save a city, but
uneconomical for shooting down mortar shells and cheap rockets. FELs
and solid state lasers can also deliver pulses that cause impulsive
shocks to the target, giving a couple orgers of magnitude more
mechanical damage per energy than just burning a hole like you have to
do with chemical lasers. We still have a way to go before we get
efficient, high power pulses with nanosecond or shorter durations from
solid state lasers, though, but FELs tend to be intrinsicly pulsed
because electrons are easier to accelerate in bunches.
Nyrath the nearly wise
But he wants to ensure that things make sense *before* he
starts animating, he'd hate to have to throw away
already done work. So he'd like a critique of his
battle plan.
Again, for those late to this thread:
His original orion drive concepts:
http://rhysy.plexersoft.com/orion/
http://www.nuclearspace.com/gallery_orion_movie.htm
gallery of orion drive battleships
http://rhysy.plexersoft.com/Deep%20Space%20Force%20Gallery/
The situation is a group of US and Soviet Orion drive
battleships having an engagement around the jovan moon Callisto.
Here is his rough draft of the battle plan.
Critique away.
> As the next scenes are going to be way more complex to animate than
> previous ones, I figure I should post by battle plan before ploughing on.
> Another lengthy post I know, but this has to be right from the word go.
>
> I'll start by animating the Russian attack. I can always render the Allied
> preparations later and play with the order of the various rendered clips to
> give an impression of simultaneity, but I think it will be easier to keep
> track of things by concentrating on one thing at a time wherever possible.
>
> Firstly, now that I have super-low poly ships, a shot of the whole Russian
> fleet showing their greater seperation (say several km between each ship -
> has to be close enough that people can tell those dots in the distance are
> other ships) since firing their pulse units. I figure there should be no
> attempt to hold any kind of tactical reserve by either side, as this would
> mean the enemy could have multiple ships targetting single ships on the
> opposing side. Therefore all ships should be in approximately the same
> plane, facing the enemy, with no ships shadowed by any other.
>
> Then a couple of close-up shots of the missile turrets rotating to target
> the enemy. For some reason they're all currently pointing backwards, but at
> least this will give the opportunity for some Russian voice-overs.
> Simultaneously some of the larger missile silos will open and the Gauss
> cannons will make some adjustments. The same shots could perhaps be
> rendered from a different camera angle, with slightly altered lighting
> direction and ship name, to show that the whole fleet is about to fire.
>
> With all their missiles, the Russians would probably have a decisive
> long-range offensive advantage. Each turret holds 32 missiles and their 12
> turrets per ship, allowing them to rapidly unleash a volley of up to 384
> missiles per ship. However, since the Allies are at this stage some
> considerable distance away, they will have time to target many of the
> missiles and destroy them quickly with lasers (with the earlier
> calculations indicating many megawatts of power available per turret, I
> think the laser would appear as no more than a brief flash). To try and
> counter this the missiles might be programmed to use smaller rockets to
> cause random deviations from their flight path, sacrificing accuracy for
> sheer numbers. Each missile is about 5m long, long enough for a small nuke,
> so even a few hits may cause significant hull damage. Therefore the Allies
> will be unable to ignore this wild frenzied mass-bombardment and must
> commit fully to stopping hit (with those large spherical sections, a few
> hits from these missiles won't be fatal, just damaging).
>
> However, the more deadly threat from the Soviets will be from their much
> larger missiles, the Excaliburs and 100-megaton nukes. The real purpose of
> the missile swarm is not so much to damage the enemy as to provide cover
> for these more powerful weapons. The camera will follow one of the smaller
> missiles in a "chase plane" view, as we see many of them destroyed by laser
> fire and a significant number simply miss due to innaccuracy. There will
> then by a view from a greater distance showing the whole swarm succesfully
> - for the most part - destroyed by the laser defences of the target ship. A
> few should make it through, causing significant hull damage but largerly
> missing critical ares such as laser turrets. Heavy damage will be sustained
> to the forward cooling fins, though the rest will escape largely unscathed.
>
>
> A little while after the missiles have been fired the Gauss cannons will
> also fire in quick succession. Screened by the swarm and difficult to
> target, either one of these will hit (in which case it will blast a gaping
> whole in the forward hull, no reason small nukes couldn't be encased in the
> armour-piercing shells), or one of the big silo-launched missiles will make
> it through the lasers (haven't yet decided which to animate first -
> Excalibur or nuke). Whichever one happens, the alternative will be shown
> happening in a battle between another pair of ships.
>
> Thinking further ahead, at least one Allied ship must use its large, >14GW
> laser to destroy an enemy ship, others may attempt to do so but fail,
> illustrating the difficulty in aligning the whole ship to target the enemy.
> Since they have far fewer missile turrets/silos than the Soviets, they may
> compensate somewhat by more rapid fire from the silos. Nonetheless, the
> Soviets may hold one or two turrets in reserve that may use more accurate
> missiles, and sill have plenty of counter-missiles to quite easily destroy
> much of the Allied attack. Perhaps an e-bomb and/or a nuke should get lucky
> and make it through.
>
> Much further on, probably 3 or 4 Allied ships should be destroyed/crippled
> in the long-range attack (1 Excalibur, 1 nuke, 1 Gauss cannon shot, maybe 1
> Casaba-Howitzer (or perhaps, being slightly more advanced, that one should
> go to the Americans)). With only 2 losses to the Russians they will
> apparently posses an advantage as the fleets move closer together - but by
> this time they may be rapidly running out of missiles. The Allies will also
> posses the ability to accurately and quickly target the missile turrets and
> destroy them with lasers. Gunfire may begin to dominate at closer
> distances, with the both sides firing small nuclear artillery, and the
> Russians immensive armour-penetrating weapons from the Gauss cannons - if
> they can fire before the lasers destroy them.
>
> Well, that's the plan anyway - it's there so people can nit-pick before I
> go ahead and animate it... any crits once the missile swarm has been
> animated will get an ice-cold reception. Shouldn't be too bad to animate
> though, most explosions will only need a brief flash :
http://rhysy.plexersoft.com/Deep%20S...ion%20test.avi
> Some close-ups may be
> also be shown, a new explosion will be necessary for these.
IsaacKuo
Nyrath the nearly wise wrote:
> Rhys Taylor is ready to start animating the space battle proper.
> But he wants to ensure that things make sense *before* he
> starts animating, he'd hate to have to throw away
> already done work. So he'd like a critique of his
> battle plan.
I could literally go on all day about how silly all the unguided
weaponry is, but that would take too long. I'll just stick to
a couple of other issues:
1. The layout of the weaponry and sensors should be changed,
to allow full "broadsides". Right now, there's a strange
4-symmetry going on which might look kind of cool but doesn't
make as much sense as 2-symmetry.
Think about how WWII warships placed the main weaponry
and gun directors along the centerline. This allowed all
weapons and sensors to look in the same direction, except for
straight forward/rearward. They would have placed all secondary
weaponry along the centerline also, except they ran out of space.
For a spaceship, this isn't a problem--both the "top" and the
"bottom" can be used.
2. The fleet spacecraft are just freaky close to each other.
They'd never be so close to each other, especially in a
situation where there are tons of unguided projectiles being
used (never mind for the moment how incredibly silly that is
for space combat).
> > Firstly, now that I have super-low poly ships, a shot of the whole Russian
> > fleet showing their greater seperation (say several km between each ship -
> > has to be close enough that people can tell those dots in the distance are
> > other ships) since firing their pulse units.
IMHO, there should never be a situation where more than
one warship is visibly much more than a dot. If you want
to visibly show more than one hull on screen at a time, do
so from the tactical display of one of the ships--it will feature
zoomed optical views of each "target".
For an external shot of a fleet, you can show flashbulb
bright dots of the pulse units during a shared maneuver.
> > I figure there should be no
> > attempt to hold any kind of tactical reserve by either side, as this would
> > mean the enemy could have multiple ships targetting single ships on the
> > opposing side. Therefore all ships should be in approximately the same
> > plane, facing the enemy, with no ships shadowed by any other.
There are many tactical reasons why you might rather
have ships in a rough line rather than in a plane. In
particular, there's the possibility that the battle is a
high speed interception pass. In this case, the relative
velocities of the opposing fleets is too high for a second
pass.
The defenders have an obvious reason to space out
their forces--so that rear layers can pick off survivors
from the initial confrontation.
What's less obvious is that the same may apply to the
attackers. The defenders may be attacking using
missiles, in which case the attackers are defenders
also--they're defending themselves from the missiles.
> > Then a couple of close-up shots of the missile turrets rotating to target
> > the enemy.
Why are there missile turrets at all? There's a good reason
why we switched from missile launchers to VLS, and they
apply even more in space. The missiles should simply
pop out of their storage tubes. This reduces weight,
complexity, and cost.
> > they will have time to target many of the
> > missiles and destroy them quickly with lasers (with the earlier
> > calculations indicating many megawatts of power available per turret, I
> > think the laser would appear as no more than a brief flash). To try and
> > counter this the missiles might be programmed to use smaller rockets to
> > cause random deviations from their flight path, sacrificing accuracy for
> > sheer numbers.
It's more or less completely implausible to use dodging around
with rockets to avoid laser fire. Instead, there might be some
sacrificial armor to absorb laser fire.
> > Each missile is about 5m long, long enough for a small nuke,
> > so even a few hits may cause significant hull damage. Therefore the Allies
> > will be unable to ignore this wild frenzied mass-bombardment and must
> > commit fully to stopping hit (with those large spherical sections, a few
> > hits from these missiles won't be fatal, just damaging).
Hmm...completely implausible. At reasonable velocities for
Orion drives, a ball bearing should do massive damage to these
thin skinned battleships. (Note that what I consider to be a
"thick skinned" battleship doesn't require a pusher plate.)
A WWII era armor piercing battleship shell has a velocity on the
order of 1km/s and a mass of on the order of a ton. With closing
velocities of maybe 100km/s, a 100gram bullet would have as
much impact energy.
A chemical warhead to spread fragments may be far deadlier
than a nuclear warhead for anti-spaceship work.
> > Thinking further ahead, at least one Allied ship must use its large, >14GW
> > laser to destroy an enemy ship, others may attempt to do so but fail,
> > illustrating the difficulty in aligning the whole ship to target the enemy.
> > Since they have far fewer missile turrets/silos than the Soviets, they may
> > compensate somewhat by more rapid fire from the silos.
The rate of fire for missiles should be...how many do you feel like
firing? With missiles fired straight out of their storage tubes, the
limit on rate of fire simply boils down to what makes the most
tactical sense.
Even if a launcher system is used, it's plausible for an entire missile
magazine to be unloaded within minutes. With engagements occuring
across tens of thousands of kilometers, it may take an hour for the
missiles to reach the target anyway. The difference between launching
them over the course of seconds verses a couple minutes may be
insignificant.
Oh, I imagine you're protesting that it's too boring to have missiles
cruising along for over an hour before reaching the target. Yes,
it's too boring! But that may be what's realistic. Once the enemy
is within effective range, why not start firing? There's no good
reason to wait until you're in knife range of the enemy if you're
armed with a machinegun.
In order to depict realistic space combat in fiction, it's going to
be necessary to use storytelling techniques to compress/skip
the boring waits.
> > Well, that's the plan anyway - it's there so people can nit-pick before I
> > go ahead and animate it... any crits once the missile swarm has been
> > animated will get an ice-cold reception. Shouldn't be too bad to animate
> > though, most explosions will only need a brief flash :
Isaac Kuo
Luke Campbell
use a telescope to aim and focus a weapons-grade laser - a two-for-one
deal.
> > However, since the Allies are at this stage some
> > considerable distance away, they will have time to target many of the
> > missiles and destroy them quickly with lasers (with the earlier
> > calculations indicating many megawatts of power available per turret, I
> > think the laser would appear as no more than a brief flash).
That depends on the nature of the laser, the distance to the target,
and the diameter of the beam pointer telescope.
A continuous beam laser may have to dwell on a missile for some time
before burning through its armor, as would a pulsed laser at long
ranges. At closer ranges, a very high powered pulse could blast or
crumple a missile in one flash. The longer the range, the less intense
the telescope will be able to focus the laser beam, and the longer it
will take to burn through. The larger the telescope, the better it
will be able to focus the beam, and the quicker it will burn through
and the longer the range at which pulses will cause explosive
vaporization.
If you want numbers, lets assume we are dealing with neodymnium
sapphire lasers, frequency doubled to emit green beams (roughly 0.5
microns in wavelength), delivering 1 kilojoule pulses with a 1
nanosecond duration at a 1 kilohertz repitition rate (for a total
average power of 1 megawatt, and a peak power of 1 terrawatt). We'll
have the telescopes have a 5 meter aperture for convenience (that is,
the focusing mirrors are 5 meters across). This means the telescope
can focus the beam into a spot with a diameter equal to 1/10,000,000 of
the distance to the target. At 10,000 km you would have a 1 meter spot
size, at 1000 km, a 10 cm spot size.
To get reliable explosive vaporization, you need 10,000,000,000 watts
per square centimeter. This means that you need to focus the pulse
into an area of 100 square centimeters or less. You get this at about
1000 km. You may get explosive vaporization out of about three times
this range, depending on the hull/armor material of the missiles. Each
pulse will deliver the energy of 0.25 grams of TNT exploding. You will
need to deliver many of these to blast through the hull material or
armor. At 1 kHz, this may not take long, maybe 1/100 of a second for
an unarmored missile, maybe 1/10 of a second (or even a full second)
for a heavily armored missile.
Beyond the range at which you get explosive vaporization, you will need
to rely on heating the missile enough to evaporate its hull/armor into
space. This will take longer. From U.S. military film clips of
megawatt lasers burning holes through unarmored missiles with a beam
spot size that I estimate at about 10 cm across, it takes a second or
two to burn through.
Visually, you will not see any beam, but you will get a powerful green
flash (or continuous green flare, depending on the dwell time) where
the beam is incident on the missile.
> > To try and
> > counter this the missiles might be programmed to use smaller rockets to
> > cause random deviations from their flight path, sacrificing accuracy for
> > sheer numbers.
Lasers are so fast and accurate that dodging will not help. The only
thing you can do is to increase the dwell time it takes for the beam to
destroy a missile. Also, the missiles will surely be guided. Accuracy
will not be a problem.
> > Each missile is about 5m long, long enough for a small nuke,
> > so even a few hits may cause significant hull damage.
Kinetic kill warheads will have a longer lethal detonation range than
nukes. You can expect closing velocities in the 10 to 100 km/s range.
At those speeds, all you need is a big plug of ball bearings and a
small explosive bursting charge. Pop the charge and you get a narrow
cone of lethal projectiles flying toward the target. There are so many
ball bearings that the target cannot shoot them all down, the ball
bearings cover a wide enough area that the target cannot dodge out of
the cone. At velocities greater than about 4 km/s, impact will shock
vaporize the ball bearing and any armor made of matter held together by
chemical bonds, with more energy per unit mass than is supplied by
chemical explosives. The greater the closing speed, the more violent
the explosion. I estimate you can detonate your warheads at about 10
km away at 10 km/s closing speeds with kinetic kill warheads, while you
would need to be within a km or so for a reasonable sized nuke.
> > A little while after the missiles have been fired the Gauss cannons will
> > also fire in quick succession. Screened by the swarm and difficult to
> > target
With lasers, if you can detect the projectile, you can target it. Any
reasonable missile will probably have a better delta-V than a gauss
cannon, though, so gauss cannons are most likely to be used
defensively, projecting a screen of (relatively) slow moving
projectiles to intercept incoming missiles or enemy warships that are
stupid enough to approach closely at high speeds. As an offensive
weapon, though, at the lower velocities nukes start to become a viable
alternative to kinetic kill warheads.
> >
> > Thinking further ahead, at least one Allied ship must use its large, >14GW
> > laser to destroy an enemy ship, others may attempt to do so but fail,
> > illustrating the difficulty in aligning the whole ship to target the enemy.
Lasers focused through a telescope mount shouldn't have this problem -
if you can see the target, you can bring your scope to bear and focus
your beam on it. No need to align the whole ship, just point a scope.
Then there is the issue of tactics. Since the ruskies are using
predominantly missiles, with a smattering of launched ordinance, they
will want to have as large a relative velocity to the yankies as
possible. A fast pass at high speeds with even faster missiles will do
the most damage. The yanks, with their lasers, will want to hover just
on the edge of the effective laser range at low relative velocities, so
they can pick off the missiles in time while blasting the ruskies at
their leasure. If Ivan starts accelerating towards Uncle Sam, the U.S.
should accelerate away from the russians to reduce the closing speed of
the missiles. It also means the yanks can drop projectiles of their
own, so that the ruskies will be accelerating into them, and will hit
them harder.
Luke
Eivind Kjorstad
> But he wants to ensure that things make sense *before* he
> starts animating, he'd hate to have to throw away already done work.
> So he'd like a critique of his battle plan.
First, the ships:
The American one looks as if the ship-part is significantly larger
diameter than the pusher-plate. This would mean, either you detonate the
nukes *very* close to the pusher-plate, or the ship itself gets nuked
with every propulsive nuke.
Since you can turn your ship like you want, there should be atleast one
direction in which all weapons can point.
Shooting unguided "bullets" at these distances is silly and pointless.
If the target has even tiny maneuvering-capacity, it won't be where
you're aiming by the time your bullets arrive where you thougth the ship
was gonna be.
>> Each missile is about 5m long, long enough for a small nuke,
>> so even a few hits may cause significant hull damage.
A "few" hits by nukes "may" cause "significant" hull damage ? What are
these ships made of anyway ?
With any reasonable spaceship a single hit by a nuke will mean instant
kill. Indeed at the speeds an Orion-drive ship can reach, a single hit
by a 10g ball-bearing can easily mean instant kill.
Unless your entire ships are constructed like the pusher-plate, in which
case the enemy could outrun them by a factor of like 100 by constructing
their ships ligther.
>> commit fully to stopping hit (with those large spherical sections, a few
>> hits from these missiles won't be fatal, just damaging).
Completely unreasonable. A hit by anything is fatal, given reasonable
assumptions.
>> fire and a significant number simply miss due to innaccuracy.
Why ? Hitting a 100m or so radius space-ship that is (relative to the
acceleration-capabilities of a rocket) under no acceleration is a simple
task even by todays tech. (it may accelerate, but it can only do so with
perhaps 1G along *one* axis, along any other axis at a miniscule
fraction of that)
>> A little while after the missiles have been fired the Gauss cannons will
>> also fire in quick succession. Screened by the swarm and difficult to
>> target, either one of these will hit.
If you fire a shell at oh, say 100.000 km distance and somehow manage to
make a cannon firing rounds at 10km/s, you're still guessing as to where
the target will be 3 hours from now. Even at very close 10.000km you're
still guessing as to where the target will be 20 minutes from now.
You're proposing to guess where a vehicle that moves at maybe 100km/s
and can maneuver at 1G, and that actively want to be hard to hit will be
20 minutes from now.
This won't work.
>> Since they have far fewer missile turrets/silos than the Soviets, they
>> may compensate somewhat by more rapid fire from the silos.
This is extremely silly.
You can simply toss all the missiles out, they'll float peacefully
alongside your ship until you give them the order to accelerate. Even a
ship with a lot of missiles, and few missile-launchers will be able to
have *all* it's missiles attack at the very same moment, if they so wish.
>> With only 2 losses to the Russians they will
>> apparently posses an advantage as the fleets move closer together -
>> but ...
Certainly. Couldn't have a battle not follow the single, known-to-all
patten of cinematic battles:
Our Heroes suffer high losses initially, and appear to be close to
losing the figth. They then somehow, in the last minute, execute some
daring maneuver and miracolously win the figth. It doesn't matter if
it's Karate Kid, Rocky, or a US orion-drive spaceship.
Which would perhaps make it exciting, except that is *PRECISELY* how 99%
of the viewers will expect the figth to go, long before its even
started. D for originality.
>> Gunfire may begin to dominate at closer distances,
You should consider (or if you did, tell us) what kind of time, distance
and velocities you're talking about.
Are these two enemy fleet meeting from an initial distance of hundreds
of thousands of kilometres and with relative velocity-differences
100km/s or more ?
Or are they two enemy fleet "parked" 100km from eachother when suddenly
and unexpectedly war is declared ?
Eivind Kjørstad
Luke Campbell
Eivind Kjorstad wrote:
> A "few" hits by nukes "may" cause "significant" hull damage ? What are
> these ships made of anyway ?
>
> With any reasonable spaceship a single hit by a nuke will mean instant
> kill.
Read the first part of this thread. Depending on the distance at the
time of detonation, it is not neccessarily an instant kill.
Luke
Logan Kearsley
> First, there's no need to have both laser turrets and telescopes. You
> use a telescope to aim and focus a weapons-grade laser - a two-for-one
> deal.
>
You could do that, and it's probably a good thing to aim for, but mightn't
it be beyond their current engineering abilities for a certain cost?
Sighting telescopes don't need to be particularly large or robust, while the
military laser optics might sacrifice increased precision for larger
apertures and heat dissipation ability at low cost.
IsaacKuo
Logan Kearsley wrote:
>"Luke Campbell" <lwc...@gmail.com> wrote in message
>news:1155610608.9...@m73g2000cwd.googlegroups.com...
>>First, there's no need to have both laser turrets and telescopes. You
>>use a telescope to aim and focus a weapons-grade laser - a two-for-one
>>deal.
This depends on the sort of telescope, I think. You
want to have two sorts of telescopes--narrow field of
view telescopes for tracking a target, and wide field
of view telescopes for detecting a target in the first
place.
I think the laser turrets are suitable for telescopes
with narrow field-of-view, but you'd want a different
sort of telescope for the wide field-of-view telescopes
(Schmidt? Three-Mirror?).
>You could do that, and it's probably a good thing to aim for, but mightn't
>it be beyond their current engineering abilities for a certain cost?
>Sighting telescopes don't need to be particularly large or robust, while the
>military laser optics might sacrifice increased precision for larger
>apertures and heat dissipation ability at low cost.
If anything, the telescopes need a larger aperture than
the laser.
There's an interesting question of what the ideal number
of turrets is. One thing that's counterintuitive is that
the number of turrets has little effect on total firepower.
Your laser engine(s) can fire the beam down a central
corridor, with mirrors to select a branch toward any of
the laser turrets. No matter how many turrets you have,
you can concentrate all laser firepower through one
turret.
I tend to favor two turrets on opposite sides. Besides
providing all around coverage and some redundancy, it
also allows use of a "hunter-killer" tactic. While one
turret fires the laser to kill a target, the other turret
can be scanning to "hunt" for the next target. This
allows a near instantaneous switch from one target to
the next, minimizing down time for the laser engine.
More importantly, this has a big tactical effect on the
enemy's options. Suppose each of your ships only had
one laser turret, and the enemy knows this. Then the
enemy knows it takes some time for you to switch from
the current targets to new targets. If the enemy notices
that all of your ships are firing on particular targets, he
can take advantage of this to open up sensitive sensors
or radiators onboard the non-targeted ships. He knows
that if you want to fire on a different target, he's got enough
time to close protective "shutters". In contrast, with two
turrets per ship nowhere is safe from being targetted.
Isaac Kuo
Logan Kearsley
>
> Logan Kearsley wrote:
> >"Luke Campbell" <lwc...@gmail.com> wrote in message
> >news:1155610608.9...@m73g2000cwd.googlegroups.com...
> >>First, there's no need to have both laser turrets and telescopes. You
> >>use a telescope to aim and focus a weapons-grade laser - a two-for-one
> >>deal.
>
> This depends on the sort of telescope, I think. You
> want to have two sorts of telescopes--narrow field of
> view telescopes for tracking a target, and wide field
> of view telescopes for detecting a target in the first
> place.
>
> I think the laser turrets are suitable for telescopes
> with narrow field-of-view, but you'd want a different
> sort of telescope for the wide field-of-view telescopes
> (Schmidt? Three-Mirror?).
<snip>
> There's an interesting question of what the ideal number
> of turrets is. One thing that's counterintuitive is that
> the number of turrets has little effect on total firepower.
> Your laser engine(s) can fire the beam down a central
> corridor, with mirrors to select a branch toward any of
> the laser turrets. No matter how many turrets you have,
> you can concentrate all laser firepower through one
> turret.
Up to the thermal tolerances of the mirrors, anyway.
And if you're using X-ray lasers, that applies much less strongly (I would
almost say not at all, but I suppose it would be possible to set up a
grazing incidence mirror system to direct the beams wherever you wanted- I
imagine it would be rather bulky and delicate).
> I tend to favor two turrets on opposite sides. Besides
> providing all around coverage and some redundancy, it
> also allows use of a "hunter-killer" tactic. While one
> turret fires the laser to kill a target, the other turret
> can be scanning to "hunt" for the next target. This
> allows a near instantaneous switch from one target to
> the next, minimizing down time for the laser engine.
The advantage is lessened if you have separate wide-field 'hunter'
telescopes. But there is still an advantage in being able to retrain one
turret on a new target while still firing with the other, to allow
instantaneous switching.
Another advantage of having separate telescopes and lasers is that, once
you've started firing, you can't use the laser turret as a telescope to
track its own target anymore.
Luke Campbell
Logan Kearsley wrote:
> "Luke Campbell" <lwc...@gmail.com> wrote in message
> news:1155610608.9...@m73g2000cwd.googlegroups.com...
> > First, there's no need to have both laser turrets and telescopes. You
> > use a telescope to aim and focus a weapons-grade laser - a two-for-one
> > deal.
> >
>
> You could do that, and it's probably a good thing to aim for, but mightn't
> it be beyond their current engineering abilities for a certain cost?
> Sighting telescopes don't need to be particularly large or robust, while the
> military laser optics might sacrifice increased precision for larger
> apertures and heat dissipation ability at low cost.
Once you've got a military beam pointer, you've got a bad-ass
telescope. You can round it out with a plethora of smaller sensor
scopes if you want - they're cheap and give redundancy.
Larger apertures automatically give increased precision - unless you
did a flubbed job grinding the lens (Hubble Space Telescope) or have
buggy software for aligning multiple mirror telescopes or adaptive
optic mirrors. These are the sorts of things that should be worked out
with the prototypes before the laser scopes begin to be mass produced
for the military by the lowest bidder.
Heat dissipation may be important (although not necessarily, dielectric
layer mirrors give you 99.9% reflectivity, and if you are using a
multi-meter mirror to focus a laser with a lethal spot size of 10 cm or
so, heating may not be a concern). If you do have extra doohickies to
draw the heat away from the mirror, it will certainly have been a
priority to make sure they do not compromise the ability of that scope
to focus the beam, which means you get just as good resolution when
using it as a sensor.
Luke
Luke Campbell
IsaacKuo wrote:
> I tend to favor two turrets on opposite sides. Besides
> providing all around coverage and some redundancy, it
> also allows use of a "hunter-killer" tactic. While one
> turret fires the laser to kill a target, the other turret
> can be scanning to "hunt" for the next target. This
> allows a near instantaneous switch from one target to
> the next, minimizing down time for the laser engine.
My ships tend to have about half a dozen scopes. First, this gives
redundancy in case several get taken out by hostile action (or human
error, down time for maintenance, etc). Second, because of the finite
slew time of large scopes, this allows you to cycle through the scopes,
allowing each time to aquire a new target before it is called on to do
its duty. The more powerful the laser, the more important this becomes
- if it takes a microsecond to destroy a target, but twenty seconds to
point a scope at a new target, your rate of zapping incoming enemy
missiles is limited by the number of scopes.
Note that slew time becomes much less of a factor when missiles are
approaching in groups. The scope only has to slew over a small angle
before bringing another missile into its field of view. With adaptive
optics, this can be even faster since you can adjust the focus be
deforming the mirror rather than moving the mount. The latter trick
only works with targets that have a small angular separation between
them, of course.
Luke
Luke Campbell
Logan Kearsley wrote:
> Up to the thermal tolerances of the mirrors, anyway.
> And if you're using X-ray lasers, that applies much less strongly (I would
> almost say not at all, but I suppose it would be possible to set up a
> grazing incidence mirror system to direct the beams wherever you wanted- I
> imagine it would be rather bulky and delicate).
If you've got x-ray lasers and anything like diffraction limited
optics, your range becomes so long that missiles become more and more
irrelevant.
> Another advantage of having separate telescopes and lasers is that, once
> you've started firing, you can't use the laser turret as a telescope to
> track its own target anymore.
This is true for CW lasers, but pulsed lasers would allow simultaneous
tracking and blasting with the same scope. Switch the scope over to
the laser for the nanosecond or so duration of the laser pulse, then
back to the sensor for the cycle time 'till the next pulse.
Luke
IsaacKuo
Luke Campbell wrote:
> My ships tend to have about half a dozen scopes. First, this gives
> redundancy in case several get taken out by hostile action (or human
> error, down time for maintenance, etc).
Because of the plausible speed of slewing over very small angles,
I don't see this as being much of a defense against hostile action.
Small angle slewing by adaptive optics servos would allow all
turrets to be sequentially taken out in rapid succession.
With a long range battle between laser armed "thin skinned" ships,
I see things as degenerating down to who has the laser with the
longest practical range. Whoever can start dealing out damage
at a longer range wins a completely one-sided battle since there
really isn't any way for a thin skinned enemy to close range before
being totally dismantled.
Instead of having a dozen scopes, a single scope with 3x the
diameter would mean an effective range of 3x as much. I do
think that a second scope provides some important redundancy
for things like human error, maintenance downtime, etc.
[...]
> Note that slew time becomes much less of a factor when missiles are
> approaching in groups. The scope only has to slew over a small angle
> before bringing another missile into its field of view. With adaptive
> optics, this can be even faster since you can adjust the focus be
> deforming the mirror rather than moving the mount. The latter trick
> only works with targets that have a small angular separation between
> them, of course.
Like multiple turrets on a single ship, or a swarm of missiles fired
from a ship at long range (a final act as it's getting carved apart
by your laser).
Isaac Kuo
Luke Campbell
IsaacKuo wrote:
> Luke Campbell wrote:
>
> > My ships tend to have about half a dozen scopes. First, this gives
> > redundancy in case several get taken out by hostile action (or human
> > error, down time for maintenance, etc).
>
> Because of the plausible speed of slewing over very small angles,
> I don't see this as being much of a defense against hostile action.
> Small angle slewing by adaptive optics servos would allow all
> turrets to be sequentially taken out in rapid succession.
I was thinking more in the terms of a killer BB swarm kinetic kill
missile. The BB's wouldn't be able to target specific components, but
could easily smash a scope or three. If the craft survives the swarm,
it could still have an effective way to blast additional missiles if it
had some redundancy.
In most of the scenarios I imagine with visible/near UV/near IR lasers,
the lasers are primarily defensive on account of having too short a
range to blast enemy craft 1/3 of an A.U. away. Missiles can reach out
and touch someone on the other side of the solar system. The exception
is engagements in orbit around a contested planet, when lasers can be
used against other spacecraft in orbit, orbital instalations, and
ground targets.
That said, if the lasers are good enough to make long range missiles
unreliable, and you sometimes have to get in close and duke it out beam
to beam like a real man ... err ... spacecraft, then you are quite
right.
Luke
Rhysy
velocities/distances. However I really don't find these tens of
thousands of kilometers distance or up to 100km/s velocities quoted at
all plausible. No-one's going to fight a battle if there's time to
dodge the enemy missiles, or even just leave the combat zone
altogether. It makes no sense. At lower distances, the high relative
velocities I also find highly dubious as I doubt any system is every
going to be perfect to ever be able to accurately target anything at
those kinds of speeds.
Strangely though, people have also raised issue with the unguided
weaponary (which only amounts to a few guns anyway - I barely even
mentioned it in the battle plan). Yet others think that unguided ball
bearings are going to be devastating weapons ! Firstly, unguided
weaponary may have two uses : Actually causing damage, or causing the
opponent to expend resources to avoid it (either dodging at high
distances - which I find highly suspect - or using countermeasurs such
as lasers, or simply having to have lots of armour). Secondly, this
idea of low-mass ball bearings being used to cripple warships is not
plausible in my opinion.
100g ball bearings being fired at 100km/s do have the KE of WWI
battleship shell, but weren't those filled with explosives too ?
Moreover these ships are rather larger than WWI vessels both in size
and mass. As for the claim that a mere 10g ball bearing could be
deadly, this is simply wrong, it doesn't have enough energy. Even if
you did, somehow, get your high-speed tiny ball bearings fired at high
energy from a great distance to hit the enemy, it seems dubious that
such small objects would necessarily have the same effect as a larger
shell. Finally, as I've said, I don't find these immensive velocities
plausible (I would stress that this is not from orbital considerations,
just from a tactical point of view).
IssacKuo suggest a full broadside. Unfortunately, no design changes are
possible at this stage (bar 1, possibly, see later), however, I'm not
convinced that would be a good idea. Better to have all weapons
pointing towards the enemy if possible, it also helps protect the
vulnerable drive section.
On the distances between ships, I fully agree.But they aren't going to
be that close in combat, I have already animated them seperating.
Having them this close at all is an artistic concesstion so that people
can see clearly, "Ah, a fleet of spaceships !" without needing to be
told it's a fleet. I admit it may be necessary to display the ships
closer together in combat than would actually occur - what would be the
point, artistically, in having them too far apart to see ? It would
only serve to add confusion.
Can you explain in more detail why a line is preferred to a plane ? I
can't see much difference.
There are missile turrets so that they can be pointed towards the enemy
and save -albeit slightly- on propellant.
Dodging to avoid lasers is not so implausible I think - a moving target
is simply harder to hit. However that is something that can be changed,
if necessary.
"A chemical warhead to spread fragments may be far deadlier
than a nuclear warhead for anti-spaceship work. " - that's an
interesting point, but you'd have to somehow deliver the chemical to
the interior. If you look at the US ships you'll see all the weapons
are in a completely seperate section to the habitat rings (which may
therefore have very heavy armour), so may use this to shield the
habitats from such attacks. The Russian ships do not have this option,
but this chemical would have to spread to a very wide area to be
effective. An internal modular design would be highly efficient at
stopping such chemical weapons - which must also impact the ship,
whereas a high-yield nuke need not.
" There's no good reason to wait until you're in knife range of the
enemy if you're
armed with a machinegun. " - but as you say the missiles may take an
hour to reach their targets, this analogy doesn't hold. A knife takes a
finite amount of time whereas a machine gun incapacitates instantly -
that's the whole point of the gun. The enemy isn't going to stand idlly
by for an hour being shot at.
Luke Campbell - haven't done the math on the lasers yet but I'll get
round to it.
"Visually, you will not see any beam, but you will get a powerful green
flash (or continuous green flare, depending on the dwell time) where
the beam is incident on the missile. " - showing the beam is another
artistic necessity, I think. The audience needs to see clearly what's
happening, and OK, I like a nice lightshow. :)
"Lasers are so fast and accurate that dodging will not help." - ah, but
are they ? Many claims have been made that such-and-such a system has
such-and-such an amazing accuracy. How it would work in practise is
another matter entirely. The turrets are going to take a finite amount
of time to target very precisely the incoming missiles.
"At velocities greater than about 4 km/s, impact will shock
vaporize the ball bearing and any armor made of matter held together by
chemical bonds, with more energy per unit mass than is supplied by
chemical explosives." - Sounds plausible. Depends on the number and
mass of the ball bearings as to whether they'd be any use : large
cannonballs may be effective, but not small ball bearings. I still
doubt they'd be a guaranteed kill weapon though - any impact weapon is
going to have strong local effects but it's hard to see anything being
a truly lethal ship-killer. I was envisaging KE weapons as attempts to
cripple/disable ships rather than stop them outright. Use of nuclear
charges within the shells should be possible.
"With lasers, if you can detect the projectile, you can target it." -
yes, but it's a lot harder to spot the nuclear weapon if it's hidden
amongst 200 other projectiles.
"No need to align the whole ship, just point a scope. " - the big laser
is probably the one design element I can still alter, since it's been
shown in the closed position throughout. It could instead be labelled
as a docking port/lifeboat hangar, or something. I guess whether you'd
need a laser cannon rather than a turret would depend on how much power
you can channel through a small area without burning your own system.
Currently, the laser turrets are envisaged primarily (though not soley)
as an anti-missile defense system, with the laser cannon acting only as
an anti-ship offensive weapon. Its advantage would be its large area
allowing the beam to be sustained long enough to cause an outright kill
on an enemy ship.
"Since the ruskies are using
predominantly missiles, with a smattering of launched ordinance, they
will want to have as large a relative velocity to the yankies as
possible...." - clearly establishing the velocities and distances is
going to have to be a priority.
Issac :
"In contrast, with two turrets per ship nowhere is safe from being
targetted. " - depends on ship shape. I have 24 on the forward hull to
save on targetting time and ensure absolutely no blind spots. Also
gives redundancy and allows multiple targets to be shot at the same
time.
On lasers as telescopes, I wasn't 100% sure if they could work like
that so I added telescopes for the hell of it. In any case, gives you
redundancy, and no reason warship crews couldn't do a little science to
pass the time, eh ?
Given there are many swings and roundabouts to both lasers and
missiles, I suspect neither will have a decisive advantage overall.
Probably saturating the lasers with missiles at long range will give
missiles an advantage. At closer range, the faster damage speed of
lasers and precision targetting may give them the advantage.
Eivind Kjorstad :
"The American one looks as if the ship-part is significantly larger
diameter than the pusher-plate. This would mean, either you detonate
the nukes *very* close to the pusher-plate, or the ship itself gets
nuked
with every propulsive nuke. " - Not that close - about 40m for a
perfectly symmetrical explosion (a distance comparable with what's
quoted for the original scheme) and therefore quite a lot further for a
directed nuke. It would depend on the yeild, propellant mass, and
pusher plate thickness.
"Since you can turn your ship like you want, there should be atleast
one
direction in which all weapons can point." - which indeed there is for
the Allied ships. Not really any need for the Russians to have this
capability, relying on missiles.
""Shooting unguided "bullets" at these distances is silly and
pointless." - Well firstly from where do you get the impression that
unguided weapons are so important in my scenario ? If you look at the
designs you'll see that they form a minor, almost backup system.
However, it is neither silly nor pointless to force the enemy to engage
in maneuvers that waste pulse units and, perhaps, force him into a more
vulnerable position. Anyway I wasn't thinking of these very high
velocities and distances, which don't sound at all practical to me. At
closer range unguided weapons may at least tie up the enemy defenses
whilst other weapons do the main damage.
"With any reasonable spaceship a single hit by a nuke will mean instant
kill." - the nukes referred to in that context are small, sub-kiloton
nukes, and very large (~1 million tonne) spaceships. Particularly in
the case of the Allied ships there's a huge mass protecting the living
areas. Again it would depend strongly on the exact numbers, but I doubt
very much even 1 kiloton would be sufficient to cause a kill. If I
remember rightly, the T-bridge targeted in Hiroshima survived a 15kt
explosion 40 yards away. Exactly what damage a sub-kiloton nuke would
do on impact/close detonation I do not know, but instant kill ? Seems
unlikely.
Quick check (crossing fingers hoping not to slip up with the
calculator) : say the spaceship is made of steel for argument's sake.
The latent heat of fusion is 247 J/g. Let the nuke by 0.1kt (certainly
doable in a small missile or artillery shell - admittedly it could
probably be quite a bit higher). That's a total of 4.18*10^11 J
available, enough to melt 1.692*10^9g, or 1692 tonnes of steel - some
nasty damage but hardly anything like lethal. And that's ignoring the
(substantially greater amount of) heat needed to raise the steel's
temperature to boiling point, and assuming that all the energy from the
nuke is available as heat absorbed into the ship.
"Indeed at the speeds an Orion-drive ship can reach, a single hit
by a 10g ball-bearing can easily mean instant kill. "
Let's say the ship is a mere 100,000 tonnes of steel (probably in fact
several times larger). To melt it would take 2.47*10^13 J, or about a
6kt nuke (again ignoring steel's initial temperate and assuming all
this energy is somehow available for heating). Whereas even at 100km/s,
a speed, as I've said, seems very unlikely for combat at any kind of
reasonable distance, the KE of the ball bearing turns out to be 50
megajoules. Ho hum. It would therefore take 494,000 such ball bearings
to do the job, or 1 of nearly 5 tonnes in mass, but even then
transmitting all that energy to the entire ship seems unlikely. The
true energy required would be at least a factor 10 higher for a true
kill.
I therefore sumbit that no plausible KE weapon under any remotely
plausible circumstances has any chance of causing a kill to warship of
specified design.
"This won't work." - quite right, that's why I'm not proposing that.
"This is extremely silly.
You can simply toss all the missiles out, they'll float peacefully
alongside your ship until you give them the order to accelerate. Even a
ship with a lot of missiles, and few missile-launchers will be able to
have *all* it's missiles attack at the very same moment, if they so
wish." - this is a reasonable suggestion, although quite how my
proposal for faster launchers could be classed in any way as "extremely
silly" is beyond me. The end result - lots of missiles hitting rapidly
- is identical.
"Which would perhaps make it exciting, except that is *PRECISELY* how
99%
of the viewers will expect the figth to go, long before its even
started. D for originality." - There are a great many historial
examples of battles being won against seemingly overwhelming odds.
Salamis, Marathon, Guagemala, Agincourt, Rorke's Drift, Cannae,
Pharsalus, the Battle of Britain amongst many others. You want to argue
Julius Ceaser was "unoriginal" for defeating numerically superior
opponents by using superior armour and training... riiiight.
jarrod...@msn.com
The Russian fleet is refueling in orbit around Callisto. The Allied
fleet is inbound from the inner solar system. The allied fleet has to
slow down to at least Jovian escape velocity (60 kps relative to
Jupiter) before the start of the engagement. They'll have to slow
further to stay near Callisto (2 kps relative to Callisto) to capture
or bombard the Russian base there. Relative fleet speed at the time of
encounter is therefore less than 4 kps.
The Russian fleet launches barrages of long range missiles when they
are reasonably assured of hits. The limiting factor is cover provided
by Callisto. We'll assume missiles launch at a range of about twice
Callisto's diameter, or about 10,000 km. They don't want to launch
sooner than this because Orion drive performance trumps the nuclear
thermal rockets in the missiles. It's best to hang on to them as
long as possible or fleet maneuvers will make their trajectories
harmless. The missiles are deployed in lines, one for each target
ship. The first 24 missiles are inert dummies. The next three are
radiation enhanced shape charge nukes. The final three are short range
sub-munition busses. Each missile has a delta-V capability of about 20
kps and a 50 ton payload. From the target's point of view the
missiles are stacked one in front of the other; this confuses
targeting, prevents an accurate count of missiles and allows the
important missiles in the rear to use the dummies as cover.
When the missiles close to 1000 km the Allied 40 m lasers start firing.
It takes two seconds to find a target, align the optics, dwell on the
target for 0.01 sec and recharge the laser with a 1000 MW power supply.
This means each laser can destroy 24 missiles. Some ships engage the
missiles from near to far, wasting their energy on the inert dummies.
Smarter crews outmaneuver the missile stacks and engage them in a more
productive order.
Next short range missiles launch from the Allied fleet. These are
chemically propelled, have an initial mass of 500 kg and a total
delta-V of about 5 kps. The Allied short range missiles and Russian
sub-munitions have essentially the same characteristics.
At a range of about 25 km the missile barrages collide. The Allied
short range missiles are trying to get in the path of the incoming
Russian missiles, using their own kinetic energy against them. The
first Russian nuke detonates, trying to clear a path through the
defenses so the following nuke can get closer to the target ship. One
of the nukes gets close enough to damage the Allied ship. Its goal is
to scrub the point defense batteries off of the hull and kill as many
crew as possible with radiation. This will "stun" the target ship
long enough for the sub-munitions to deploy. The killing blow comes
from 5 km out. The sub-munitions deploy and 100 missiles head for the
target. Any surviving point defense coil guns start to take them out,
but as the range closes, the target cannot evade even disabled
missiles. This final phase lasts only 0.2 seconds, as the target is
crippled by a hundred 50 kg tunsten rods impacting at almost 30kps.
There are two more waves behind this. Casualties are an all or nothing
proposition and most are borne by the Allies.
The fleets pelt each other with missile barrages and desperately apply
damage control measures until they are 1000 km apart. They battle has
lasted about 50 minutes. Now the surviving Allied 40 m lasers have a
decisive advantage. At the relative fleet speeds, the lasers have
enough time to fire up to 100 pulses each, more than enough power to
render any Russian ship mission killed. The Allies are limited only by
the damage they have sustained and their ability to dissipate heat.
The Russians bear the bulk of the casualties at this stage.
The fleets continue to blast away at each other amid clouds of coolant
gases and assorted debris until they are within 10 km. By now all the
primary weapons systems are destroyed and the battle is reduced to
hulks pathetically flailing at each other with secondary weapons and
trying to maneuver to blast each other with their Orion drives. Crews
are braving the radiation to keep up the attack or desperately trying
to get their radiators working again.
Survivors get to repeat the process every time their orbits come close
enough, or they get to break orbit and try for safe harbor if they have
the delta-V left. The truly unlucky get to collide and commence the
boarding action.
IsaacKuo
Luke Campbell wrote:
> IsaacKuo wrote:
> > Luke Campbell wrote:
> > > My ships tend to have about half a dozen scopes. First, this gives
> > > redundancy in case several get taken out by hostile action (or human
> > > error, down time for maintenance, etc).
> > Because of the plausible speed of slewing over very small angles,
> > I don't see this as being much of a defense against hostile action.
> > Small angle slewing by adaptive optics servos would allow all
> > turrets to be sequentially taken out in rapid succession.
> I was thinking more in the terms of a killer BB swarm kinetic kill
> missile. The BB's wouldn't be able to target specific components, but
> could easily smash a scope or three. If the craft survives the swarm,
> it could still have an effective way to blast additional missiles if it
> had some redundancy.
I think that if it gets to the point that a missile has reached its
target, it's pretty much game over anyway. Better to prevent that
in the first place, either with long range lasers or short range
defensive missiles. For missile defense, I see short range
missiles/projectiles as being more efficient than lasers. Defensive
"bullets" don't need to be launched at high velocities, and yet
they can use the kinetic energy of the incoming against itself.
Lasers never get this "free energy" boost.
> In most of the scenarios I imagine with visible/near UV/near IR lasers,
> the lasers are primarily defensive on account of having too short a
> range to blast enemy craft 1/3 of an A.U. away. Missiles can reach out
> and touch someone on the other side of the solar system. The exception
> is engagements in orbit around a contested planet, when lasers can be
> used against other spacecraft in orbit, orbital instalations, and
> ground targets.
> That said, if the lasers are good enough to make long range missiles
> unreliable, and you sometimes have to get in close and duke it out beam
> to beam like a real man ... err ... spacecraft, then you are quite
> right.
That's really the problem--how do these long range missiles
survive in the face of extended exposure to long range laser
fire? Even with an effective range of only, say, 12,000km, it
would take even a fast 100km/s missile two minutes to
cross the distance. If each laser can take out one missile
per second, then a fleet of ten ships could wipe out a wave
of a thousand fast missiles with laser fire alone. That isn't
even counting the short range defenses.
If we consider a simplified scenario where there are no short
range defenses, then we still have the matter of the target's
own offensive long range missiles. If both you and the enemy
have ten thousand missiles, then the enemy can defend
against your missiles by shooting them down with their
own missiles. Any missiles that they can take out with
long range lasers are a bonus.
So what's the incentive to fire your missiles from outside
laser range? The enemy will shoot down some or all of
them with lasers, and then the rest get taken out by the
enemy's own missiles. The end result is that you've
expended some missiles while the enemy has expended
fewer missiles.
The situation gets even less favorable for the attacker
if you assume the existence of cheap low Isp defensive
missiles.
That's why I tend to assume offensive missiles are fired
from short-medium range and have comparatively low
Isp. They need to be cheap enough to use en masse
to brute force their way past cheap defensive missiles.
This still leaves open the question of how the launching
ship itself made its way past enemy laser fire, of course.
I don't think thin skinned warships can plausibly do it,
but maybe thick skinned "asteroid battleships" could.
Maybe.
Isaac Kuo
Luke Campbell
Rhysy wrote:
> OK, I should probably have determined the relative
> velocities/distances. However I really don't find these tens of
> thousands of kilometers distance or up to 100km/s velocities quoted at
> all plausible. No-one's going to fight a battle if there's time to
> dodge the enemy missiles, or even just leave the combat zone
> altogether. It makes no sense.
Except that the missiles are guided. You try to dodge them, they
follow you. You try to leave the combat zone, they follow you.
Now there is the question of whether the missiles have the delta-V that
the main ship has. If you cannot pack an orion drive or other nuclear
drive on the missiles, then the orion drive main ships can run away
given enough time/distance. On the other hand, if the missile's drive
has anywhere near the performance of the main craft's drives, the
missiles have a huge advantage at maneuvering. The reason is that the
main craft will only expend about 1/4 their delta V to close with a
target, because the crew all want to get home and they need to expend
another 1/4 of the delta V to slow down at (or after) the mission
objective, 1/4 to accelerate back towards home, and 1/4 to stop at
home. The missiles don't care about getting home. They don't care
about stopping. They can exhaust all their delta-V in one sprint to an
intercept course with the target. Here, "intercept" is one of those
nice military euphamisms for crashing into the target (or at least
getting within a few km, so the KK ball bearings or nukes or whatever
can do their work)
> At lower distances, the high relative
> velocities I also find highly dubious as I doubt any system is every
> going to be perfect to ever be able to accurately target anything at
> those kinds of speeds.
There are technical chalenges, but they seem quite doable. The U.S.
military has repeatedly demonstrated this ability (although there were
technical glitches at first). Hitting small target with another small
target at 20 km/s is doable, and this is a direct hit. If you only
need to detonate a nuke within 100 meters or so, or send a cloud of
ball bearings out in a swarm that is 100 meters across by the time of
impact with the craft, it gets much easier.
> Strangely though, people have also raised issue with the unguided
> weaponary (which only amounts to a few guns anyway - I barely even
> mentioned it in the battle plan).
Your description made the missiles seem to be unguided. If they are
guided, you will not loose accuracy by jinking about during approach
(but while jinking may help in dodging incoming kinetic projectiles, it
will not help against lasers).
> Yet others think that unguided ball
> bearings are going to be devastating weapons !
The ball bearings themselves are unguided, but the missiles that
deliver them are not. closing at 20 km/s (say), and releasing the BBs
from 200 km out, the ball bearings drift for only ten seconds before
encountering their target. They are launched with enough precision to
give a cone centered on the current position of the craft, and over a
wide enough cone that in that half second, the craft has no chance of
accelerating away from the cone in time. Detonating closer to the ship
means you get more densly spaced ball bearings, but gives the craft
more time to shoot down the missile, something of a trade off.
> Secondly, this
> idea of low-mass ball bearings being used to cripple warships is not
> plausible in my opinion.
>
> 100g ball bearings being fired at 100km/s do have the KE of WWI
> battleship shell, but weren't those filled with explosives too ?
> Moreover these ships are rather larger than WWI vessels both in size
> and mass. As for the claim that a mere 10g ball bearing could be
> deadly, this is simply wrong, it doesn't have enough energy. Even if
> you did, somehow, get your high-speed tiny ball bearings fired at high
> energy from a great distance to hit the enemy, it seems dubious that
> such small objects would necessarily have the same effect as a larger
> shell.
A single ball bearing is probably not going to be a ship killer.
That's why the missile carries tens of thousands of them, and releases
them in a swarm. Remember, too, after discharging the BBs, the main
body of the missile is still closing at 10 to 100 km/s. There's no
reason the drives/reactor/fuel tanks/etc can't also be guided during
that last second or so. The BBs cause many small holes and wipe out
surface emplacements (turrets, scopes, sensors, heat radiators). This
may cripple or mission kill the craft. If it doesn't, the collision
with the main body of the missile will destroy the craft - I mean
destroy it. Reduce it to drifting fragments and chunks, or at least
put so large a gaping hole in it that it is no more than a drifting
hulk. The difference is that the defending craft has maybe an extra
ten seconds to shoot down the main body of the missile, while blasting
10,000 BBs out of the sky is hopeless.
> Finally, as I've said, I don't find these immensive velocities
> plausible (I would stress that this is not from orbital considerations,
> just from a tactical point of view).
The side armed with missiles and kinetic weapons will want as high of
velocitiy as possible, to enhance the hitting power of their weapons
and to give the other side less chance to shoot the weapons (and the
opposing craft!) down. Targeting will not be a problem, as has been
demonstrated with modern technology.
> Dodging to avoid lasers is not so implausible I think - a moving target
> is simply harder to hit. However that is something that can be changed,
> if necessary.
It has been repeatedly demonstrated with military test lasers (google
for THEL, MTHEL, ABL, MIRACL), with astronomical telescopes, with
radars (across interplanetary distances, even), military sensors
(trying to scan or "paint" hostile evading targets) that putting a beam
of electromagnetic radiation exactly where you want it is a
technologically doable challenge. The only way to dodge is at very
close ranges and high velocities, where your movement is so fast that
the scope can't slew about in time to track you. Farther away, the
beam will be on target.
> "A chemical warhead to spread fragments may be far deadlier
> than a nuclear warhead for anti-spaceship work. " - that's an
> interesting point, but you'd have to somehow deliver the chemical to
> the interior.
I think the idea was to use the warhead to spread fragments of the
missile toward the target craft - the ball bearing cocept again.
> " There's no good reason to wait until you're in knife range of the
> enemy if you're
> armed with a machinegun. " - but as you say the missiles may take an
> hour to reach their targets, this analogy doesn't hold. A knife takes a
> finite amount of time whereas a machine gun incapacitates instantly -
> that's the whole point of the gun. The enemy isn't going to stand idlly
> by for an hour being shot at.
They can try to dodge if they want, but the missiles will track them
and home in on them. Note that even if the enemy manages to outrun the
missiles, you have made him waste a valuable resource - his delta-V.
If he does not have enough propellant to finish his mission, you've
won. He may not even have enough propellant to get home, in which case
the other side is now out some very expensive craft that will need to
be replaced.
> "Visually, you will not see any beam, but you will get a powerful green
>
> flash (or continuous green flare, depending on the dwell time) where
> the beam is incident on the missile. " - showing the beam is another
> artistic necessity, I think. The audience needs to see clearly what's
> happening, and OK, I like a nice lightshow. :)
And I will sadly shake my head and be disappointed, just like every
time I see supposedly "realistic" space battles that show visible
beams.
Now there is a way - after the first few pulses have blasted bits off
the other guys, you can get gas and dust and smoke and fragments
escaping into space that the beam has to go through to hit the target.
The light scattered from these gases and particulates can give a
visible beam for a short distance before the target. You can get neat
dynamic effects as the beam flickers into and out of visibility as the
gas jets intercept it, as debris drifts into its path and flares
brightly before vaporizing, and so on.
But really, if you are trying to make a realistic clip, just see where
invisible beams takes you. You get fancy light shows from the flashes
and sparks and incandescent debris at the target.
> "No need to align the whole ship, just point a scope. " - the big laser
> is probably the one design element I can still alter, since it's been
> shown in the closed position throughout. It could instead be labelled
> as a docking port/lifeboat hangar, or something. I guess whether you'd
> need a laser cannon rather than a turret would depend on how much power
> you can channel through a small area without burning your own system.
Not really. The advantage of a scope is so overwhelming everyone will
want to use one, and mirrors can be so reflective (99.9% or more at a
known wavelength) and large (so the beam is spread out more and heats
the mirror less) that any plausable laser can be guided and focused
with a scope. Note that the ABL, with a multimegawatt laser, is
focused through a scope with a diameter of about a meter.
> At
> closer range unguided weapons may at least tie up the enemy defenses
> whilst other weapons do the main damage.
Even the close range weapons will probably have guidance and minimal
maneuvering capabilities. Just a small chemical rocket with 100 m/s
delta-V can mean the difference between having an incoming missile
dodge (because it can) and smacking that rocket out of the sky.
> the nukes referred to in that context are small, sub-kiloton
> nukes, and very large (~1 million tonne) spaceships.
To me, a sub-kiloton weapons nuke in space sounds completely pointless.
A 0.1 kT and a 100 kT nuke both require the same amount of plutonium,
the same amount of triggering explosives, the same amount of neutron
and radiation reflectors, tritium and berylium, and etcetera. For the
same expense and mass, you can have a 100 kT fission bomb. For not too
much more mass, you can have half a megaton or more fusion bomb. This
gives you longer kill ranges and causes more havoc in general.
The point of 0.1 kT bombs is to limit collateral damage. For this kind
of engagement, you don't need to worry about collateral damage.
> Quick check (snipped check)
You don't need to melt the entire craft to destroy it. Mechanical
damage in the form of shocks is much more effective at breaking up
objects than thermal means. Smash, don't burn. Or, in the case of
impulsive vaporization, smash by burning (but it is the smash that does
the damage).
> I therefore sumbit that no plausible KE weapon under any remotely
> plausible circumstances has any chance of causing a kill to warship of
> specified design.
A half ton missile impacting at 20 km/s will handlily take it out, no
questions asked. 10,000 ten gram ball bearings at 20 km/s will
puncture and perforate it and cripple many of its surface emplacements.
Note that unlike some other posters, I am not convinced that a ten gram
hypervelocity projectile will cause significant damage to the main body
of an armored warship. Sure, you've got huge heaps of kinetic energy,
but you've not got very much momentum. Momentum is what keeps things
going in one direction. The greater your ratio of KE to momentum, the
more spherical the resulting explosion and the less penetration into
the interior you will get. You can carve out a lot of craters on the
armored surface, though.
In particular, armor designed to protect spacecraft from hypervelocity
projectiles will probably use some variation on the whipple shield -
have a think outer layer of armor, a gap, and then several thick plates
separated by gaps. The impact with the thin outer layer vaporizes the
projectile, and the resulting plasma and re-condensed debris spreads
out before impacting the first inner layer. The inner layer absorbs
much of the impact, and will do so more easily because of how much the
debris has spread, but if it also fails, it will slow down and spead
out the debris even more before encountering the next layer, and so on.
These sheilds seem to be quite effective against orbital debris in
near earth orbit. A large or fast enough projectile will of course
defeat the armor, but it is considerably more effective than a solid
armor slab.
Luke
IsaacKuo
Rhysy wrote:
>OK, I should probably have determined the relative
>velocities/distances.
This REALLY should have been the first thing you figured out.
Without a sense of scale, you might as well have space
fighters shaped like giant robots duking it out with beam
sabres and plasma axes. (Trust me, this looks REALLY COOL!
Do it!)
>However I really don't find these tens of
>thousands of kilometers distance or up to 100km/s velocities quoted at
>all plausible. No-one's going to fight a battle if there's time to
>dodge the enemy missiles, or even just leave the combat zone
>altogether.
You don't just "dodge" enemy missiles. Missiles are guided.
If you make a maneuver, a missile will also maneuver, so it
hits anyway. This is the whole reason why today's missiles
can hit a target even after travelling hundreds of kilometers
to do so.
The 100km/s figures come from the fact that you're using
orion drives. Orion drives are capable of higher velocities
than chemical rockets or solid core nuclear thermal rockets.
What's the point of using Orion drives if you're not going
to use its capabilities? It's like making jet fighters
which only travel at a hundred miles per hour.
But the main thing driving up the speculated combat distances
is the plausible effective range of laser weapons. Even
with today's technology, lasers with a range of at least
4000km could be fielded (Space Based Laser). This sort of
range is potentially useful because it means a small number
of satellites could provide global coverage against
ballistic missiles. There's no real reason why today's
technology couldn't be scaled up to have an effective range
of tens of thousands of kilometers--it's just that we
have no current need for such long ranges. Earth just
isn't that big.
>It makes no sense. At lower distances, the high relative
>velocities I also find highly dubious as I doubt any system is every
>going to be perfect to ever be able to accurately target anything at
>those kinds of speeds.
Those speeds don't represent unreasonably high slew rates
when you're firing from tens of kilometers away. With
high velocities, it might actually be easier to hit the
enemy with a long range laser than with a self guided
short range missile.
With a self guided missile, hitting a fast incoming target
is very challenging. The target starts off as a miniscule
dot which is barely moving, and then as it gets closer that
dot blows up in brightness by the inverse square law (or
inverse r^4 with active radar!), while the apparent motion
blows up inversely (1/r). It is HARD to design a missile
sensor which can handle this wide range of behavior with
the necessary precision. From the perspective of the missile,
the target is a small unmoving dot until suddenly ZOOM--it's
a streak off to some side as the missile misses. It sounds
like an impossible problem to solve.
However, there's a neat little "trick" to give accuracy
to missiles, called "beam-riding". This is where a
guiding vehicle shines a conical beam at the target,
and the missile keeps itself centered on the beam.
In this case, there are no issues with inverse laws or
inverse square laws. The missile merely needs to be
able to maneuver with as much thrust as the target to
stay on target. This beam-riding "trick" is used a lot
in real life.
>Strangely though, people have also raised issue with the unguided
>weaponary (which only amounts to a few guns anyway - I barely even
>mentioned it in the battle plan).
They figure quite prominently in the design of the
ships you propose. That they're even included at all
is a bit silly.
>Yet others think that unguided ball
>bearings are going to be devastating weapons !
No one who thinks unguided ball bearings are plausible
space weapons knows what they're talking about.
Note that Luke Campbell did propose a ball bearing
WARHEAD for long range MISSILES. He even proposed
a reasonable knife-fight range of 10km as a possible
warhead detonation range. This showers the target
area with a shotgun conical spread of ball bearing
fragments, and could be more effective than a nuclear
warhead.
>Firstly, unguided
>weaponary may have two uses : Actually causing damage, or causing the
>opponent to expend resources to avoid it (either dodging at high
>distances - which I find highly suspect - or using countermeasurs such
>as lasers, or simply having to have lots of armour).
There's no need to dodge unguided weaponry, because
the chances of them even hitting if you don't dodge
is minimal. Just look at real life artillery. Here,
we're talking about really short ranges of maybe 20km.
An unguided shell at this range has more or less no
chance of hitting a point target. In contrast, a GPS
guided shell has an extremely high chance of hitting
a point target.
>Secondly, this
>idea of low-mass ball bearings being used to cripple warships is not
>plausible in my opinion.
>100g ball bearings being fired at 100km/s do have the KE of WWI
>battleship shell, but weren't those filled with explosives too ?
Not much. Almost all of the mass of each shell was
dumb iron just to handle the shock of firing and to
penetrate the enemy's armor. A small explosive charge
was included because that's what would do the most
damage once the armor was penetrated--otherwise, the shell
would punch entirely through the target only depositing
a very small fraction of its kinetic energy.
The dynamics of hypervelocity collisions is very
different. There's no risk of "shoot through" with
a hypervelocity collision. The projectile and whatever
it hits is vaporized in a spectacular explosion. It's
like the effect of shell guns on wooden battleships.
>IssacKuo suggest a full broadside. Unfortunately, no
>design changes are possible at this stage
Pity. Oh well, I thought this was the most minor of
possible suggestions, as it wouldn't require you to
change your overall plan, scales, or chosen weaponry.
>(bar 1, possibly, see later), however, I'm not
>convinced that would be a good idea. Better to have all weapons
>pointing towards the enemy if possible, it also helps protect the
>vulnerable drive section.
The drive section isn't vulnerable--it's plausibly
the least vulnerable part of the entire ship. It's
got this sturdy chunk of metal designed to widthstand
nuclear explosions. If anything, you want to point it
at the enemy, so you can hide stuff behind it! Of
course, the enemy isn't going to just let you do that.
The enemy will space his forces apart so that there is
no single direction to defend against. That's just
common sense.
Anyway, superfiring centerline weapons can all fire
straight forward. In naval ships, superfiring is
limited by the fact that turrets high above the
waterline decrease stability and require heavy
armored support structures. In a space ship, there's
no such limitation on superfiring.
>On the distances between ships, I fully agree.But they aren't going to
>be that close in combat, I have already animated them seperating.
>Having them this close at all is an artistic concesstion so that people
>can see clearly, "Ah, a fleet of spaceships !" without needing to be
>told it's a fleet. I admit it may be necessary to display the ships
>closer together in combat than would actually occur - what would be the
>point, artistically, in having them too far apart to see ? It would
>only serve to add confusion.
As I said, you can display an entire fleet using a
tactical display, or by showing them as a collection
of flashbulb nuclear detonation "dots" maneuvering
together.
Think about what a tactical display is going to look
like. Is it just going to be a blank screen with
some tiny dots on it? No, each dot is going to be
associated with data about what it is. This isn't
air combat where there's a need to not overly obstruct
the pilot's view--that's why a jet fighter display
is made up of thin lines. There's nothing interesting
to obscure, so each "dot" will be replaced with a
zoomed in telescopic optical view of the target.
>Can you explain in more detail why a line is preferred
>to a plane ? I can't see much difference.
It depends on the tactical situation. In some tactical
situations, you'd want to space out your forces roughly
in a single plane. For example, if you want to enter
laser range simultaneously with all forces, you'd want
to arrange them all on the same sphere around the
intended target.
In other tactical situations, you may want to space
out your forces in depth (not all along a single line,
probably, because this allows the enemy to concentrate
its defenses along one axis). For example, if you're
using swarms of missiles it may make most sense to
send in your ships one at a time. A ship can expend
all of its missiles at once and then retire from the
battle (possibly by blowing through, or by getting
itself blown up by intense short range enemy fire).
The follow-up attacks can thus concentrate only on
whichever enemy ships have survived so far, rather
than wasting their missiles on redundant targeting.
>There are missile turrets so that they can be pointed
>towards the enemy and save -albeit slightly- on propellant.
It saves virtually nothing in propellant, but it
costs a lot of mass in magazine/loading systems.
Missile racks where the missiles simply get launched
straight out of their tubes weigh less than racks
where the missiles need to be shuffled around to load
into a launcher.
>Dodging to avoid lasers is not so implausible I think - a moving target
>is simply harder to hit. However that is something that can be changed,
>if necessary.
Change it. The small angle adjustments necessary to
track a "dodging" target can be applied practically
instantaneously using the adaptive optics's servos.
>"A chemical warhead to spread fragments may be far deadlier
>than a nuclear warhead for anti-spaceship work. " - that's an
>interesting point, but you'd have to somehow deliver the chemical to
>the interior.
No. You don't understand. We're talking about a chemical
warhead which explodes before reaching the target.
See, a nuclear warhead produces a flash of radiation that
is deadly out to a certain range, but beyond which it
probably just causes some heating to the outer hull.
In contrast, the kill zone of a fragmentation warhead
extends over an unlimited distance--being further away
simply means a lower chance of getting hit by a fragment.
This can be very important, tactically. You may discover
in combat that the enemy's short range defenses have an
effective range of, say, 20km. If your missiles are
nuclear tipped, you're completely screwed. There's no way
they'll ever do damage to the enemy. If your missiles
are tipped with a chemical fragmentation warhead, you can
adjust your tactics to detonate the missiles from 20+km
away. Sure, you might be operating outside the ideal
range of the warhead, but you at least have a CHANCE to
kill the target.
>" There's no good reason to wait until you're in knife range of the
>enemy if you're
>armed with a machinegun. " - but as you say the missiles may take an
>hour to reach their targets, this analogy doesn't hold. A knife takes a
>finite amount of time whereas a machine gun incapacitates instantly -
>that's the whole point of the gun. The enemy isn't going to stand idlly
>by for an hour being shot at.
Yes, the enemy isn't going to stand idly by. But what
exactly is the enemy going to do about it? Dodge? The
missiles simply follow anyway. Fire defensive missiles?
Sure...but they could do the exact same thing at short
range also. You don't gain anything by waiting around.
Laser fire? Okay, that's the big one. But for your
scenario to work at all, you need to assume that for
some reason the lasers are utterly pathetic.
>Luke Campbell - haven't done the math on the lasers yet but I'll get
>round to it.
You'll do a LOT better by letting Luke Campbell do the
math for you. Seriously.
>"Visually, you will not see any beam, but you will get a powerful green
>flash (or continuous green flare, depending on the dwell time) where
>the beam is incident on the missile. " - showing the beam is another
>artistic necessity, I think. The audience needs to see clearly what's
>happening, and OK, I like a nice lightshow. :)
You can get a nice lightshow just from the "muzzle flashes"
and the exploding targets.
Also, you can get visible beams near the target for real.
As part of the target gets blasted away, fragments and
vapor will be expelled in all directions. A high power
laser beam firing through this very thin "smoke" will be
visible (but far dimmer than the target spot).
>Quick check (crossing fingers hoping not to slip up with the
>calculator) : say the spaceship is made of steel for argument's sake.
>The latent heat of fusion is 247 J/g. Let the nuke by 0.1kt (certainly
>doable in a small missile or artillery shell - admittedly it could
>probably be quite a bit higher). That's a total of 4.18*10^11 J
>available, enough to melt 1.692*10^9g, or 1692 tonnes of steel - some
>nasty damage but hardly anything like lethal.
[...]
>I therefore sumbit that no plausible KE weapon under any remotely
>plausible circumstances has any chance of causing a kill to warship of
>specified design.
Damage is NOT done by melting the target. Damage is primarily
done by explosions causing physical shock and propelling
fragments through the ship. It takes much less energy to
punch through a plate of steel with a fragment than it does
to melt it.
Consider what any real life metal ship looked like when it
was destroyed. It might have been ripped into several pieces
due to internal explosions, but practically all of the actual
metal would still be there in solid form. It takes stupid
amounts of energy to melt it down. No one does it. There's
no need. Perforate a target with lots of holes, or rip it
apart...don't melt it to slag.
If you use the "does it have enough energy to melt the
target" criteria, then every weapon ever used short
of a nuke impossibly short on power.
> You can simply toss all the missiles out, they'll float peacefully
> alongside your ship until you give them the order to accelerate. Even a
> ship with a lot of missiles, and few missile-launchers will be able to
> have *all* it's missiles attack at the very same moment, if they so
> wish." - this is a reasonable suggestion, although quite how my
> proposal for faster launchers could be classed in any way as "extremely
> silly" is beyond me. The end result - lots of missiles hitting rapidly
> - is identical.
The thing which is silly is the idea that anyone would be
limited by a slow missile launch rate. You suggest that
somehow the guys with the faster launchers make up for
the fact that the other side has more missiles overall.
In fact, it's only plausible for the total number of missiles
to matter. Either side can launch them as fast as they want.
>"Which would perhaps make it exciting, except that is *PRECISELY* how
>99%
>of the viewers will expect the figth to go, long before its even
>started. D for originality." - There are a great many historial
>examples of battles being won against seemingly overwhelming odds.
>Salamis, Marathon, Guagemala, Agincourt, Rorke's Drift, Cannae,
>Pharsalus, the Battle of Britain amongst many others. You want to argue
>Julius Ceaser was "unoriginal" for defeating numerically superior
>opponents by using superior armour and training... riiiight.
Julius Ceaser was unoriginal for doing that. It's a
cliche strategy which works. For a military leader trying
to acheive his objectives, originality takes a back seat
to military effectiveness.
To me, the damning thing about your scenario is that there's
no attempt on the part of either side to employ actual tactics.
In all of the historical battles you reference, the military
commanders made plans and made tactical decisions according to
the unfolding tactical situation and stratigic objectives.
It wasn't just a case of mashing two opposing forces against
each other and hoping for the best.
Here on rec.arts.sf.science, we tend to get caught up in
the technology and pay short shrift to tactics and strategy.
But the latter can be the really interesting story.
Imagine someone from the American Civil War era trying to
imagine what air combat would be like. He might imagine
fleets of "airships" lining up next to each other to exchange
"broadsides". Could he have ever imagined the tactically
rich scenarios of dogfighting maneuvers?
More recently, consider what happened when jet fighters
and guided missiles were developed. Based on the numbers,
a lot of smart technologically minded people thought that
dogfighting was dead. Opposing jets would simply make a
single high speed pass, loosing their missiles and then
returning home (if they survived). Sounds like a good
theory on paper, but what happened in real life? Dogfights.
It would be decades before the vision of BVR "push-button"
air combat would come true, and even now we don't discount
the possibility that dogfights will still occur.
In all of our speculations about what space combat would
be like, I always have the sneaking suspicion that we're
the equivalent of American Civil War era people trying to
speculate what aerial combat would be like. The way things
move around in space is so completely unlike the way
things move around in the air or water or land. I suspect
that whatever space combat is actually like, it will
involve more interesting tactics than anything we've
come up with.
The frustrating things to me is...the interesting tactics
of space combat will be entirely intuitive and obvious
to future generations. Just as we're intuitively familiar
with what air combat is like, future generations will
be intuitively familiar with what space combat will be like.
And today's speculative space warships will look as silly
to them as Land Battleships look to us.
Isaac Kuo
IsaacKuo
Luke Campbell wrote:
[...about a fragmentation proximity warhead...]
>The difference is that the defending craft has maybe an extra
>ten seconds to shoot down the main body of the missile, while blasting
>10,000 BBs out of the sky is hopeless.
This is the reason why I think the innermost layer of
short range defenses should be to fire nuclear pulse
units at relatively low velocity (maybe 1km/s or less).
It's better to lob a dozen nukes at a BB swarm and
vaporize the whole lot of them than it is to lose
the ship.
If you're defending against just one missile, then
you can even pop out a bunch of nukes at zero velocity
and then thrust away from the incoming to put this
collection of defensive nukes between you and the threat.
Of course, the enemy is probably not going to be so
accomodating and would rather simultaneously attack
with several missiles from different directions.
Cinematically, I think the struggle between attacking
missiles and short range defenses could be quite
spectacular.
>It has been repeatedly demonstrated with military test lasers (google
>for THEL, MTHEL, ABL, MIRACL), with astronomical telescopes, with
>radars (across interplanetary distances, even), military sensors
>(trying to scan or "paint" hostile evading targets) that putting a beam
>of electromagnetic radiation exactly where you want it is a
>technologically doable challenge. The only way to dodge is at very
>close ranges and high velocities, where your movement is so fast that
>the scope can't slew about in time to track you. Farther away, the
>beam will be on target.
The issues of slew rate as well as 1/r^2 and 1/r^4 effects
on sensors make it so that the best laser to defend your
ship at point blank range is actually a laser on some other
warship. This is one reason for spacing out your warships
far from each other--it makes it easier to support each
other with defensive laser fire.
>In particular, armor designed to protect spacecraft from hypervelocity
>projectiles will probably use some variation on the whipple shield -
>have a think outer layer of armor, a gap, and then several thick plates
>separated by gaps. The impact with the thin outer layer vaporizes the
>projectile, and the resulting plasma and re-condensed debris spreads
>out before impacting the first inner layer. The inner layer absorbs
>much of the impact, and will do so more easily because of how much the
>debris has spread, but if it also fails, it will slow down and spead
>out the debris even more before encountering the next layer, and so on.
>These sheilds seem to be quite effective against orbital debris in
>near earth orbit. A large or fast enough projectile will of course
>defeat the armor, but it is considerably more effective than a solid
>armor slab.
This depends upon how thick the armor needs to be. If
the goal is to use the minimum mass required to protect
from tiny impact debris, then this is ideal. However,
once the thickness of the armor gets to be much greater
than the diameter of the payload, then spacing the armor
is less attractive due to the increased area being
protected.
My favorite pet concept of ablative Orion battleships
feature thick spherical hulls with relatively small
payload cores. I've been rethinking this basic concept
lately, though. It seems to solve some relatively easy
problems by introducing a lot of hard problems. I
still think the basic idea of using propellant as armor
is sound, but...
Isaac Kuo
IsaacKuo
jarrod...@msn.com wrote:
>Try this scenario:
Hmm...an interesting scenario. Some nitpicks...
>The Russian fleet is refueling in orbit around Callisto. The Allied
>fleet is inbound from the inner solar system. The allied fleet has to
>slow down to at least Jovian escape velocity (60 kps relative to
>Jupiter) before the start of the engagement. They'll have to slow
>further to stay near Callisto (2 kps relative to Callisto) to capture
>or bombard the Russian base there. Relative fleet speed at the time of
>encounter is therefore less than 4 kps.
I'll presume the goal is to capture the Russian base. For
bombardment, there's no reason to slow down until AFTER
the base has already been wiped out by the hypervelocity
bombardment.
>The Russian fleet launches barrages of long range missiles when they
>are reasonably assured of hits. The limiting factor is cover provided
>by Callisto. We'll assume missiles launch at a range of about twice
>Callisto's diameter, or about 10,000 km. They don't want to launch
>sooner than this because Orion drive performance trumps the nuclear
>thermal rockets in the missiles.
This works if we assume the Russian fleet doesn't know
the Allied fleet's objective. If they know the objective,
then they can launch missiles at any time in orbit around
Callisto. Still, there's no particular reason to fire
earlier anyway.
>It's best to hang on to them as
>long as possible or fleet maneuvers will make their trajectories
>harmless. The missiles are deployed in lines, one for each target
>ship. The first 24 missiles are inert dummies. The next three are
>radiation enhanced shape charge nukes. The final three are short range
>sub-munition busses. Each missile has a delta-V capability of about 20
>kps and a 50 ton payload. From the target's point of view the
>missiles are stacked one in front of the other; this confuses
>targeting, prevents an accurate count of missiles and allows the
>important missiles in the rear to use the dummies as cover.
This isn't entirely plausible. The Allied fleet won't be
deployed in a single tight group, but rather spaced
apart into at least two spaced apart taskforces. The
reason for spacing out the ships is precisely to prevent
any blind spots.
Conversely, the Russian fleet should be spaced apart into
at least two taskforces so they have no blind spots
(although they perhaps need this less because they've got
sensor stations on Callisto).
>When the missiles close to 1000 km the Allied 40 m lasers start firing.
>It takes two seconds to find a target, align the optics, dwell on the
>target for 0.01 sec and recharge the laser with a 1000 MW power supply.
>This means each laser can destroy 24 missiles. Some ships engage the
>missiles from near to far, wasting their energy on the inert dummies.
>Smarter crews outmaneuver the missile stacks and engage them in a more
>productive order.
All it takes is at least two spaced apart taskforces and
they can pick and choose their targets at will without
wasting any maneuvering fuel.
(I personally find 1000km to be an implausible short
effective range for a 40m diameter laser, but let's
just go with it for now, regardless.)
>Next short range missiles launch from the Allied fleet. These are
>chemically propelled, have an initial mass of 500 kg and a total
>delta-V of about 5 kps. The Allied short range missiles and Russian
>sub-munitions have essentially the same characteristics.
>At a range of about 25 km the missile barrages collide. The Allied
>short range missiles are trying to get in the path of the incoming
>Russian missiles, using their own kinetic energy against them. The
>first Russian nuke detonates, trying to clear a path through the
>defenses so the following nuke can get closer to the target ship. One
>of the nukes gets close enough to damage the Allied ship. Its goal is
>to scrub the point defense batteries off of the hull and kill as many
>crew as possible with radiation. This will "stun" the target ship
>long enough for the sub-munitions to deploy. The killing blow comes
>from 5 km out. The sub-munitions deploy and 100 missiles head for the
>target. Any surviving point defense coil guns start to take them out,
>but as the range closes, the target cannot evade even disabled
>missiles. This final phase lasts only 0.2 seconds, as the target is
>crippled by a hundred 50 kg tunsten rods impacting at almost 30kps.
>There are two more waves behind this. Casualties are an all or nothing
>proposition and most are borne by the Allies.
This interaction between incoming missiles vs defense sounds
pretty good to me.
I personally don't think there's any point in using nukes
to try to punch through defenses or scrub off the point
defenses...a fragmentation warhead would work just as
well for those purposes except that it would seriously
damage the entire ship rather than just exposed point
defense weapons.
One sort of "ball bearing" warhead I like would be something
like a Metal Storm battery. In this variant, called a
"pile gun", a pile of alternating discs of metal and
explosive is used. The explosives are detonated one by
one, firing the discs of metal one at a time with an
extremely high rate of fire. The discs are slightly
concave so that the metal discs crumple up into crude
balls. After firing the entire pile, the result is a
very long line of ball projectiles. Thus, a defensive
nuke could only wipe out a few of them at once.
>The fleets pelt each other with missile barrages and desperately apply
>damage control measures until they are 1000 km apart. They battle has
>lasted about 50 minutes. Now the surviving Allied 40 m lasers have a
>decisive advantage. At the relative fleet speeds, the lasers have
>enough time to fire up to 100 pulses each, more than enough power to
>render any Russian ship mission killed. The Allies are limited only by
>the damage they have sustained and their ability to dissipate heat.
>The Russians bear the bulk of the casualties at this stage.
I think the Allies would satisfy themselves with using
their own missiles purely for defense. They know they
have the upper hand.
>The fleets continue to blast away at each other amid clouds of coolant
>gases and assorted debris until they are within 10 km.
Here's my first major nit-pick. The Allies have an
overwhelming firepower advantage at 1000km. They have
no incentive to close and every incentive to keep the
range open. If the Allies can close to 1000km, they'll
maneuver to keep the range open and prevent a close
range engagement.
Now, if the Russians didn't already know about the
Allied laser capabilities, they surely have figured it
out based on the lasers being used against their
missile waves. What's good against missiles is good
against their ships. They know that the Allies have
laser weaponry good out to at least 1000km, and they
know they don't have any weaponry to answer it in
return.
The result? The Russians have two choices--try to
stay outside of 1000km range, or try to maneuver in
such a way to force closing quickly to point blank
range. For example, they might try to do some
clever orbital slingshot around one of Jupiter's
moons to engage the Allied fleet in a high speed
pass. The Allied fleet could see this coming and
would try to prevent such a closure to close range.
Both sides will be furiously running tactical
simulations and determinine what sort of maneuvers
could result in favorable engagement ranges. Note
that this situation can be extremely complex in the
orbit of Jupiter, with several major moons offering
slingshot maneuver points (and they're constantly
moving around in orbit). It can be very complex
even with just a duel between two ships. With two
opposing fleets of multiple ships, each capable of
"dropping off" groups of missiles at any time, the
possibilities are dizzying!
Despite the fact that these maneuvers may take
hours or days, the sheer complexity of the situation
means that it would take a tactical genius to
work out the best tactics. Chess is child's
play compared to this. A genius on one side could
implement a winning plan and the enemy might see
the scenario unfolding before their eyes for hours
before finally realizing what the plan was after
it's too late.
Isaac Kuo
Rhysy
Here we go again...
"Except that the missiles are guided. You try to dodge them, they
follow you. You try to leave the combat zone, they follow you."
I did originally consider 10m diameter Orion missiles but they never
made it in. So the battleships may well be capable of dodging or
leaving. Issac argues that, assuming dodging to be impossible, it won't
make any difference whether the missiles are fired early, but I
disagree. Give the missiles an hour to hit their target and the target
has an hour to hit the missiles - surely more than long enough for any
defensive system. Give them a minute and the chances of hitting them
will be much reduced. It doesn't even matter about the individual
performance of the defensive missiles (if indeed they are missiles),
enough time allows you as many attempts to hit them as you have mass to
spare.
"There are technical chalenges, but they seem quite doable. The U.S.
military has repeatedly demonstrated this ability (although there were
technical glitches at first). Hitting small target with another small
target at 20 km/s is doable, and this is a direct hit."
Well, if it's been done, then I suppose I must conceed that point.
However, it certainly can't be any easier hitting a high speed target.
"The BBs cause many small holes and wipe out
surface emplacements (turrets, scopes, sensors, heat radiators). This
may cripple or mission kill the craft. If it doesn't, the collision
with the main body of the missile will destroy the craft - I mean
destroy it. Reduce it to drifting fragments and chunks, or at least
put so large a gaping hole in it that it is no more than a drifting
hulk."
OK, I can't help but like that.
" The only way to dodge is at very
close ranges and high velocities, where your movement is so fast that
the scope can't slew about in time to track you. Farther away, the
beam will be on target."
Oh, very well, consider the dodging idea dumped.
"And I will sadly shake my head and be disappointed, just like every
time I see supposedly "realistic" space battles that show visible
beams. "
I thought you might say that. Sorry, but I just don't see how a battle
without visible beams would be comprehensible to the general audience.
Imagine a flock of missiles spontaneously combusting - it would look
ridiculous. I see nothing wrong with making artistic concessions,
entertainment is not a sin. There is no point in making a
non-entertaining, non-comprehendable space battle.
"The light scattered from these gases and particulates can give a
visible beam for a short distance before the target. You can get neat
dynamic effects as the beam flickers into and out of visibility as the
gas jets intercept it, as debris drifts into its path and flares
brightly before vaporizing, and so on."
Although this would indeed look quite spectacular - maybe even more so
than solid beams - believe me it is much harder than it sounds. I doubt
it would even be possible with the software I use.
"Note that the ABL, with a multimegawatt laser, is focused through a
scope with a diameter of about a meter. "
Ah. I suppose the big laser idea had better be ditched then.
"For the same expense and mass, you can have a 100 kT fission bomb".
Didn't realize that. I thought there were limits on how small you could
make a kt yeild bomb.
"A half ton missile impacting at 20 km/s will handlily take it out, no
questions asked. "
The whole ship ? How ?
"10,000 ten gram ball bearings at 20 km/s will
puncture and perforate it and cripple many of its surface emplacements.
"
I suppose they might damage your glass laser equipment but I can't see
them doing much more, never mind puncturing the hull. As you said, the
momentum of such a small ball is very small, and it's KE isn't that
impressive either.
"This REALLY should have been the first thing you figured out."
Ah well, never mind.
"They figure quite prominently in the design of the
ships you propose."
Err.. no, they don't. A few guns and Gauss cannons, and that's it.
Compare that with the number of missiles available to the Soviets and
they become insignificant.
"That they're even included at all is a bit silly. "
You can never, EVER have enough backup.
"Pity. Oh well, I thought this was the most minor of possible
suggestions, as it wouldn't require you to change your overall plan,
scales, or chosen weaponry."
Were it made a few weeks ago, I might have considered. It's not that it
would be difficult to reposition the weapons, it's that in that time
I've animated 2min of it, and re-rendering the whole thing now for a
highly arguable point would only delay things and waste time that could
be better spent.
"The drive section isn't vulnerable--it's plausibly the least
vulnerable part of the entire ship."
No, it's easily the most vulnerable. If your pusher plate suffers an
impact, you're not going anywhere. Even weaker would be the gas-filled
pistons, gas bags and the trapdoor. If any single component is damaged
then you are, temporarily at least, scuppered.
" It's got this sturdy chunk of metal designed to widthstand nuclear
explosions. " - explosions of a pre-determined yeild at a
pre-determined distance. A wide margin for error could be built in, but
any missile impact is going to be lethal to the drive section. The only
advantage of hiding behind it would be to use it as a shield to protect
the rest of the ship, and hope any remaining friendly ships can come to
your rescue later.
Line of battle tactics - still not sure if I understand this right.
Sounds like it depends strongly on having some ships out of range,
which is seems may be almost impossible. Choosing the eventual
distances used will, I'm afraid, probably be subject to more artistic
constraints.
"Change it." - Done.
"We're talking about a chemical warhead which explodes before reaching
the target. " - OK, what sort of chemical is going to threaten a
heavily armoured warship 20km away ?
" Fire defensive missiles? Sure...but they could do the exact same
thing at short
range also. You don't gain anything by waiting around. " - apart from
massively reducing the time the enemy has to deal with your missiles.
Lasers - see above.
"It takes much less energy to punch through a plate of steel with a
fragment than it does
to melt it. " - OK, but how wide a hole is a KE weapon ever likely to
produce, given good armour ? I still find it very unlikely to cripple a
well-designed ship.
"If you use the "does it have enough energy to melt the target"
criteria, then every weapon ever used short of a nuke impossibly short
on power" - what about lasers ?
"Either side can launch them as fast as they want. " - which was
exactly my point...
" For a military leader trying to acheive his objectives, originality
takes a back seat
to military effectiveness. " - exactly. My point was the pointlessness
of the criticism.
"To me, the damning thing about your scenario is that there's no
attempt on the part of either side to employ actual tactics. "
Err... that's why I posted it instead of just animating it straight
off. I did only post the inital scenes, I made few references to how
things would unfold.
"The frustrating things to me is...the interesting tactics of space
combat will be entirely intuitive and obvious to future generations. "
- I would hope there is none.
"And today's speculative space warships will look as silly to them as
Land Battleships look to us."
Agree there. Precious few predictions ever come true.
jarrodlem - Pardon the short response, but if I spend all this time
typing, nothing will get done ! Suffice (for now) to say I liked that
scenario a lot. Very nicely described. I'll respond properly when time
permits.
To surmise, I am unsure as to what level of realism may be doable. I
know it may not sound like it but I am TRYING for some level of realism
here. I'm just not at all sure if these high distances/velocites would
work from a narrative point of view - how is the viewer to know which
ship is firing on which opponent ? Would it really make THAT big of a
difference to have the ships closer and slower ?
Logan Kearsley
news:1155755403.3...@h48g2000cwc.googlegroups.com...
>
> "And I will sadly shake my head and be disappointed, just like every
> time I see supposedly "realistic" space battles that show visible
> beams. "
> I thought you might say that. Sorry, but I just don't see how a battle
> without visible beams would be comprehensible to the general audience.
> Imagine a flock of missiles spontaneously combusting - it would look
> ridiculous. I see nothing wrong with making artistic concessions,
> entertainment is not a sin. There is no point in making a
> non-entertaining, non-comprehendable space battle.
What, and you're just going to pander to the lowest common denominator? It
can be plenty entertaining without having to have visible beams, with all
the flashing and exploding going on.
> "The light scattered from these gases and particulates can give a
> visible beam for a short distance before the target. You can get neat
> dynamic effects as the beam flickers into and out of visibility as the
> gas jets intercept it, as debris drifts into its path and flares
> brightly before vaporizing, and so on."
> Although this would indeed look quite spectacular - maybe even more so
> than solid beams - believe me it is much harder than it sounds. I doubt
> it would even be possible with the software I use.
That, on the other hand, is a defensible excuse.
> "We're talking about a chemical warhead which explodes before reaching
> the target. " - OK, what sort of chemical is going to threaten a
> heavily armoured warship 20km away ?
The chemical warhead does not directly threaten the ship- it's a means to
disperse a cloud of shrapnel which threatens the ship. Ball-bearing bus and
all that.
> "It takes much less energy to punch through a plate of steel with a
> fragment than it does
> to melt it. " - OK, but how wide a hole is a KE weapon ever likely to
> produce, given good armour ? I still find it very unlikely to cripple a
> well-designed ship.
>
> "If you use the "does it have enough energy to melt the target"
> criteria, then every weapon ever used short of a nuke impossibly short
> on power" - what about lasers ?
Pulsed lasers, which rely on the mechanical shock produced by rapidly and
repeatedly heating/vaporizing surface material in order to tear the target
apart can do more damage per watt than continuous beam lasers trying to
melt/vaporize a hole in the target.
Mark L. Fergerson
> Here we go again...
>snip to the crash<
> To surmise, I am unsure as to what level of realism may be doable. I
> know it may not sound like it but I am TRYING for some level of realism
> here. I'm just not at all sure if these high distances/velocites would
> work from a narrative point of view - how is the viewer to know which
> ship is firing on which opponent? Would it really make THAT big of a
> difference to have the ships closer and slower?
Closer and slower=easier to kill.
Compare other SFnal visual representations of space battles, and
think about which ones make us groan and why.
Frinst the Star Wars battle scenes are generally guilty of every
impossible cliche imaginable. The through-the-window background battles
during foreground dramatic scenes are much more "realistic", but all you
can see are quite realistic moving dots and flashes of light as weapons
do their damage upon impact or ships explode.
Take the much better new Battlestar Galactica; I haven't seen any
beam weapons used but you have visible smoke trails from missiles and
tracerlike railgun trajectories, not to mention fighters can kill their
engines, turn via RCS and fire without affecting their drift trajectory
(much), and so on. ISTM the scale is severely compressed (too close and
slow) for "dramatic" effect, but that may just be me.
Then you have B5 and Trek's visible beams which are completely
unrealistic (unless as some have claimed the off-axis visible light is a
byproduct unrelated to the damaging effect of the beam) and make a
horrible model for your lasers. You simply cannot tell who's shooting at
whom with lasers without some diffusive medium to show where the beams go.
I can see a tactical display showing _probable_ beam trajectories
after the fact- "This ship's mirror is radiating lots of heat, and that
ship's showing a glowing ablation cloud, so _he_ probably shot _him_."
but other than that you're out of luck.
Now if you can justify setting your battle in a large, diffuse gas or
dust cloud, say from recently-destroyed colonist or supply ships (what
are the combatants fighting about, anyway?) you'll have _some_ realtime
visibility of laser beams assuming they're in visible wavelengths to
start with (or can excite fluorescence in the cloud). It would also
allow for expanding shells from nuke explosions making them more visibly
impressive but possibly somewhat more confusing as the cloud roils.
ISTM the ultimate in realism is realizing where you have to make your
tradeoffs.
Mark L. Fergerson
Rhysy
Here we go again...
"And I will sadly shake my head and be disappointed, just like every
time I see supposedly "realistic" space battles that show visible
beams. "
I thought you might say that. Sorry, but I just don't see how a battle
without visible beams would be comprehensible to the general audience.
Imagine a flock of missiles spontaneously combusting - it would look
ridiculous. I see nothing wrong with making artistic concessions,
entertainment is not a sin. There is no point in making a
non-entertaining, non-comprehendable space battle.
"The light scattered from these gases and particulates can give a
visible beam for a short distance before the target. You can get neat
dynamic effects as the beam flickers into and out of visibility as the
gas jets intercept it, as debris drifts into its path and flares
brightly before vaporizing, and so on."
Although this would indeed look quite spectacular - maybe even more so
than solid beams - believe me it is much harder than it sounds. I doubt
it would even be possible with the software I use.
"Note that the ABL, with a multimegawatt laser, is focused through a
"Change it." - Done.
"We're talking about a chemical warhead which explodes before reaching
the target. " - OK, what sort of chemical is going to threaten a
heavily armoured warship 20km away ?
" Fire defensive missiles? Sure...but they could do the exact same
thing at short
range also. You don't gain anything by waiting around. " - apart from
massively reducing the time the enemy has to deal with your missiles.
Lasers - see above.
"It takes much less energy to punch through a plate of steel with a
fragment than it does
to melt it. " - OK, but how wide a hole is a KE weapon ever likely to
produce, given good armour ? I still find it very unlikely to cripple a
well-designed ship.
"If you use the "does it have enough energy to melt the target"
criteria, then every weapon ever used short of a nuke impossibly short
on power" - what about lasers ?
"Either side can launch them as fast as they want. " - which was
exactly my point...
" For a military leader trying to acheive his objectives, originality
takes a back seat
to military effectiveness. " - exactly. My point was the pointlessness
of the criticism.
"To me, the damning thing about your scenario is that there's no
attempt on the part of either side to employ actual tactics. "
Err... that's why I posted it instead of just animating it straight
off. I did only post the inital scenes, I made few references to how
things would unfold.
"The frustrating things to me is...the interesting tactics of space
combat will be entirely intuitive and obvious to future generations. "
- I would hope there is none.
"And today's speculative space warships will look as silly to them as
Land Battleships look to us."
Agree there. Precious few predictions ever come true.
jarrodlem - Pardon the short response, but if I spend all this time
typing, nothing will get done ! Suffice (for now) to say I liked that
scenario a lot. Very nicely described. I'll respond properly when time
permits.
To surmise, I am unsure as to what level of realism may be doable. I
know it may not sound like it but I am TRYING for some level of realism
here. I'm just not at all sure if these high distances/velocites would
work from a narrative point of view - how is the viewer to know which
ship is firing on which opponent ? Would it really make THAT big of a
IsaacKuo
Rhysy wrote:
>"Except that the missiles are guided. You try to dodge them, they
>follow you. You try to leave the combat zone, they follow you."
>I did originally consider 10m diameter Orion missiles but they never
>made it in. So the battleships may well be capable of dodging or
>leaving. Issac argues that, assuming dodging to be impossible, it won't
>make any difference whether the missiles are fired early, but I
>disagree. Give the missiles an hour to hit their target and the target
>has an hour to hit the missiles - surely more than long enough for any
>defensive system. Give them a minute and the chances of hitting them
>will be much reduced. It doesn't even matter about the individual
>performance of the defensive missiles (if indeed they are missiles),
>enough time allows you as many attempts to hit them as you have mass to
>spare.
If the defense is in the form of missiles, it's really
just a numbers game. The guy with more missiles wins.
Firing early or firing late doesn't really make much
of a difference.
If the defense includes energy weapons (meaning lasers
and possibly particle beams), then things may get more
interesting. However, this also plausibly degenerates
down to a number game--the guy with longer ranged lasers
wins. Firing missiles early or firing late doesn't
really make a difference here either. Either you fire
the missiles early and they get picked off by enemy
lasers, or the missiles get destroyed in their launch
tubes when your ship is destroyed by enemy lasers.
>"And I will sadly shake my head and be disappointed, just like every
>time I see supposedly "realistic" space battles that show visible
>beams. "
>I thought you might say that. Sorry, but I just don't see how a battle
>without visible beams would be comprehensible to the general audience.
It's all a matter of perspective. Movies depict gunfights
all the time, but aside from tracers you can't see bullets
flying through the air. There are some simple cinematic
conventions. The most basic is a first person or over the
shoulder perspective from behind a firing ship. Another
technique used for naval battles is to cut from the
muzzle blasts of the firing ships to the exploding shells
on the target.
>Imagine a flock of missiles spontaneously combusting - it would look
>ridiculous. I see nothing wrong with making artistic concessions,
>entertainment is not a sin. There is no point in making a
>non-entertaining, non-comprehendable space battle.
Imagine seeing anti-aircraft artillery shells just
exploding in mid-air with no visibly obvious source.
Does it look ridiculous? Of course not. That's
exactly how it really looked.
>"A half ton missile impacting at 20 km/s will handlily take it out, no
>questions asked. "
>The whole ship ? How ?
The same way an asteroid impact causes a huge crater.
It causes a huge explosion which pushes parts of the
ship through other parts of the ship (most notably,
little fragments perforate the rest of the ship).
I don't think you really appreciate just how much
impact energy is involved.
>"10,000 ten gram ball bearings at 20 km/s will
>puncture and perforate it and cripple many of its surface emplacements.
>"
>I suppose they might damage your glass laser equipment but I can't see
>them doing much more, never mind puncturing the hull. As you said, the
>momentum of such a small ball is very small, and it's KE isn't that
>impressive either.
Ten gram ball bearins are a bit small; they'd strip off
the outer layers of the hull but in and of themselves
wouldn't necessarily completely destroy the ship. The
explosive shock could cause massive catastrophic damage
if the internal components aren't properly isolated
from the outer layers of the hull.
>"They figure quite prominently in the design of the
>ships you propose."
>Err.. no, they don't. A few guns and Gauss cannons, and that's it.
There are a LOT of guns and gauss cannons! For a
backup weapon not expected to be used, there really
would only be one or two.
>Compare that with the number of missiles available to the Soviets and
>they become insignificant.
Not from the way they look. First off, the proper
comparison is between the number of rounds of each.
A gun can be fired more than once; a missile is a one
shot. The total amount of firepower a gun represents
depends on the number of rounds stored.
Second, a gun has a significant mass and expense
built in to the firing/loading/aiming mechanisms
themselves. In today's warships, the gun represents
a major investment and involves many design complications.
It wouldn't be included at all if it weren't deemed
essential.
>"That they're even included at all is a bit silly. "
>You can never, EVER have enough backup.
Yes, you can. There's a reason why modern warships
typically include ONE gun rather than many. One is
enough; more than one actually diminishes a warship's
capabilities because it consumes a lot of volume
and the extra mass reduces the total number of rounds
held. Given that a single gun already provides a
sufficient rate of fire, any additional guns aren't
a good idea.
>"The drive section isn't vulnerable--it's plausibly the least
>vulnerable part of the entire ship."
>No, it's easily the most vulnerable. If your pusher plate suffers an
>impact, you're not going anywhere. Even weaker would be the gas-filled
>pistons, gas bags and the trapdoor. If any single component is damaged
>then you are, temporarily at least, scuppered.
The pusher plate is more likely to survive an impact
in a functional state than anything else on the ship.
The pusher plate is at least somewhat resistant to
laser damage, and minor physical damage merely puts
holes in the pusher plate. This reduces the amount
of thrust available, but doesn't knock it out.
(I'm assuming that behind the pusher plate the main
hull of the ship is at least modestly armored.)
If you're using pneumatic pistons, these can be
placed within the hull of the ship. The "legs"
exposed on the outside of the ship may be simply
hollow metal rods.
Laser optics are vulnerable to even tiny amounts of
dust (these cause imperfections in reflectivity which
blow up upon firing which starts a runaway effect that
takes out the entire scope). Sensor systems are
vulnerable to any sort of laser fire. Exposed weapon
systems are also vulnerable to laser fire.
>" It's got this sturdy chunk of metal designed to widthstand nuclear
>explosions. " - explosions of a pre-determined yeild at a
>pre-determined distance. A wide margin for error could be built in, but
>any missile impact is going to be lethal to the drive section.
Any missile impact is going to be lethal to anything it
hits; if the missile is substantial it'll be lethal to
the whole ship. I'm thinking mostly about laser fire,
where there's at least a chance of surviving a hit.
>The only
>advantage of hiding behind it would be to use it as a shield to protect
>the rest of the ship, and hope any remaining friendly ships can come to
>your rescue later.
If you can protect equipment behind the pusher plate
and/or other armor, then you can keep on fighting.
In many situations, you don't even really care that
much about losing your thrusters since you're already
cruising toward your intended destination anyway. If
you later need to repair your drive system or abandon
your ship at the destination, then so be it.
>Line of battle tactics - still not sure if I understand this right.
>Sounds like it depends strongly on having some ships out of range,
>which is seems may be almost impossible. Choosing the eventual
>distances used will, I'm afraid, probably be subject to more artistic
>constraints.
Well, that's okay, assuming your goal is to produce
yet another example of non-realistic space battles.
> "We're talking about a chemical warhead which explodes before reaching
> the target. " - OK, what sort of chemical is going to threaten a
> heavily armoured warship 20km away ?
Ah...I see the source of your confusion. You think
we're talking about a chemical weapon which poisons
humans.
No, no, no.
We're talking about a chemical explosive warhead which
uses a chemical reaction to cause an explosion--as
opposed to a nuclear warhead which uses a nuclear
reaction to cause an explosion. This means an explosive
chemical, in the style of gunpowder or TNT or C4.
It has absolutely nothing to do with poisons. Indeed,
many of us assume that military spacecraft won't even
be manned so there's no one to poison.
>" Fire defensive missiles? Sure...but they could do the exact same
>thing at short
>range also. You don't gain anything by waiting around. " - apart from
>massively reducing the time the enemy has to deal with your missiles.
Which isn't a limiting factor for defensive missiles
since they have a practically unlimited rate of fire.
Either they've got enough missiles to stop yours or
they don't.
>"It takes much less energy to punch through a plate of steel with a
>fragment than it does
>to melt it. " - OK, but how wide a hole is a KE weapon ever likely to
>produce, given good armour ? I still find it very unlikely to cripple a
>well-designed ship.
Literally as wide as you want. However, you neither
want just a single big hole nor is that the most likely
result of a big hypervelocity explosion. Most likely,
a big surface explosion is going to propel stuff just
inside the hull away from the explosion, ripping lots of
nasty little holes in the rest of the ship (both directly
and indirectly thanks to causing more fragments to
rip through the ship).
In case you didn't already know, KE weapons are
currently the best armor piercing weapons we have,
capable of defeating the thickest tank armor with
one-hit kills. These tanks feature advanced armor
with better protection than the thickest battleship
armor ever fielded--the only reason they can feature
such thick armor at all is because they concentrate
it entirely along a single narrow assumed threat
axis, and reduce the forward profile to a minimum.
Warships can't do this, and we've given up on the
idea of thick armor on warships.
The KE weapons used to kill tanks don't even go
very fast, in space travel terms.
>"If you use the "does it have enough energy to melt the target"
>criteria, then every weapon ever used short of a nuke impossibly short
>on power" - what about lasers ?
High power lasers do not yet have enough energy to
melt their targets--not by a long shot. What they
do have is enough energy to heat certain types of
target to certain types of failure.
For example, Airborne Laser is meant to cause a
small section of a target missile's hull to fail
by heating to the point where aluminum severely
weakens (not all the way to the melting point).
This is supposed to occur while the missile is
still in its boost phase, so aerodynamic forces
and stresses from rocket thrust will cause the
missile's airframe to buckle. The missile will
then tumble and break up in the atmosphere.
Another example--THEL is meant to take out rockets
and mortar shells by causing their warheads to
prematurely explode. Depending on the type of
warhead, it's possible to heat the entire projectile
until the warhead detonates.
>"The frustrating things to me is...the interesting tactics of space
>combat will be entirely intuitive and obvious to future generations. "
>I would hope there is none.
I'd like to be able to honestly say I hope so as well,
but I can't. As much as I lament war's toll on
humanity both in general and with respect to specific
wars...I'm a hopeless technology geek and I really
get a kick out of military hardware and tactics.
>To surmise, I am unsure as to what level of realism may be doable. I
>know it may not sound like it but I am TRYING for some level of realism
>here. I'm just not at all sure if these high distances/velocites would
>work from a narrative point of view - how is the viewer to know which
>ship is firing on which opponent ? Would it really make THAT big of a
>difference to have the ships closer and slower ?
I have spent a lot of thought on how to go about
depicting realistic space combat. My thoughts
tend to concentrate on depictions of tactical
displays within the warships. Assuming the warships
are manned, the human crews are going to need some
sort of interface telling THEM what's going on in
clear terms. The same tools can be used to show
the audience what's going on.
Isaac Kuo
Jarrod
If you can use some parts from the scenario I threw in: great. That's
what it's there for. Isaac's points seem to make sense, particularly
about the Allied fleet keeping a distance. The only argument I can
retort with is that the Allies have already expended delta-V getting to
Callisto and the Russians are still near home base. They Russians
should have the fuel to run the Allies down if they have the time.
The 40m lasers are a double edged sword. I used the Space Combat
Workbook from Darkmatters (Nyrath's site has the links.) to examine
them. I had to dumb them down pretty severely (1000 nm wavelength
etc.) or they completely dominate the battlefield. I went for a
balance where one side gets pummeled first and the situation looks
grim. Then the tables are turned and the other side gets pummeled.
Jarrod
Nyrath the nearly wise
> Note that unlike some other posters, I am not convinced that a ten gram
> hypervelocity projectile will cause significant damage to the main body
> of an armored warship. Sure, you've got huge heaps of kinetic energy,
> but you've not got very much momentum. Momentum is what keeps things
> going in one direction. The greater your ratio of KE to momentum, the
> more spherical the resulting explosion and the less penetration into
> the interior you will get.
Fascinating! But could you have pity on a physics-challenged
student and go into more details on the issues?
From my imperfect understanding, momentum is mass times
velocity, while kinetic energy is one-half mass times
the square of velocity.
In other words: as projectile velocity rises, the
kinetic energy goes up much faster than the momentum.
Do you have any ballpark estimates relating
KE:momentum ratios and sphericality of resulting explosion?
Nyrath the nearly wise
> The 100km/s figures come from the fact that you're using orion drives.
> Orion drives are capable of higher velocities than chemical rockets or
> solid core nuclear thermal rockets. What's the point of using Orion drives
> if you're not going to use its capabilities? It's like making jet fighters
> which only travel at a hundred miles per hour.
I did some crude estimates that if the invading
Orion fleet was doing a 0.01 g brachistochrone
from Earth to Callisto, the closing velocity
to Callisto would be somewhere between
zero and about 480 km/s, depending upon
whether they bothered to slow down or not.
However, my estimates were based upon
questionable understanding of the
math involved. Just for laughs, I present
it herein:
> Jupiter's orbital velocity is about 13 kilometers per second. When a
> spacecraft form the inner solar system travels to Jupiter, it has to brake
> down from whatever velocity it is traveling at to 13 km/s in order to enter
> orbit around Jupiter (this is the "arrival burn").
>
> It gets complicated since Callisto orbits Jupiter at about 8.2 km/s. My
> naive estimate is that this means the arrival burn will be down to a
> velocity of 21.2 to 4.8 km/s depending upon whether Callisto is currently
> traveling with or against Jupiter's orbital direction.
>
> The rough figures I have say that if the spacecraft lift off from Earth's
> surface and travel into orbit around Jupiter, the delta V required is:
>
> 70 km/s with five and a half years travel time for a Hohmann transfer
> 73 km/s with almost two years travel time for a Mercury-Pluto ellipse
> (don't ask)
> 118 km/s with a one year travel time for a hyperbolic solar escape
> orbit plus 30 km/s (don't ask)
> 1,000 km/s with a 3.5 month travel time for a 0.01 g brachistochrone
> 3,100 km/s with a 36 day travel time for a 0.1 g brachistochrone
> 9,900 km/s with a 12 day travel time for a 1.0 g brachistochrone
>
> Figure on 5 km/s is for Earth lift-off, plus 21 for arrival burn means that
> about 26 km/s is not included in the transit. So with a 0.01g
> brachistochrone, transit is 1000 - 26 = 974 km/s. Half is for acceleration,
> half is for deceleration, therefore the velocity at turnover is 974 / 2 =
> 487 km/s
>
> Bottom line: for a 0.01 g brachistochrone, if the defending force is in
> orbit around Callisto, the relative velocity between the two can be
> anything between zero and 487 kilometers per second. But you'd be better
> advised to get a second opinion.
Luke Campbell
IsaacKuo wrote:
> I think that if it gets to the point that a missile has reached its
> target, it's pretty much game over anyway.
With a BB swarm, not necessarily, as long as the first thing the ship
blasts is the main body of the missile. You can probably survive
several BB hits (although you won't necessarily be happy about it).
> Better to prevent that
> in the first place, either with long range lasers or short range
> defensive missiles.
Well, I won't argue with that!
> For missile defense, I see short range
> missiles/projectiles as being more efficient than lasers. Defensive
> "bullets" don't need to be launched at high velocities, and yet
> they can use the kinetic energy of the incoming against itself.
> Lasers never get this "free energy" boost.
The slower and more numerous the incoming projectiles, the better
lasers will be defensively compared to short range projectiles. Slower
means more time to engage, more numerous means you can run out of
defensive projectiles. Where the break-even point is, I don't know.
> That's really the problem--how do these long range missiles
> survive in the face of extended exposure to long range laser
> fire? Even with an effective range of only, say, 12,000km, it
> would take even a fast 100km/s missile two minutes to
> cross the distance. If each laser can take out one missile
> per second, then a fleet of ten ships could wipe out a wave
> of a thousand fast missiles with laser fire alone.
So my fleet of ten ships launches ten missiles. Each of which carries
130 submunitions which are deployed 13,000 km away. Not looking so
good for the defenders now. Unless, of course, I've got bad
intelligence and your lasers have a range of 14,000 km, in which case
my missiles don't do squat.
I've always leaned towards really large missiles with high ISP drives
carrying lots of guided submunitions with low ISP, high thrust rockets.
Mix 'n match BB canisters with nukes to your heart's content.
> If we consider a simplified scenario where there are no short
> range defenses, then we still have the matter of the target's
> own offensive long range missiles. If both you and the enemy
> have ten thousand missiles, then the enemy can defend
> against your missiles by shooting them down with their
> own missiles. Any missiles that they can take out with
> long range lasers are a bonus.
The part where offensive missile meets defensive missile becomes
interesting. How many do you deploy to counter the defensive missiles
by launching their submunitions? How many defensive missiles
concentrate on the submunitions vs the missiles that still pose a
threat to the main spacecraft?
In the end, I suspect it boils down to whomever has the most missiles.
> So what's the incentive to fire your missiles from outside
> laser range? The enemy will shoot down some or all of
> them with lasers, and then the rest get taken out by the
> enemy's own missiles. The end result is that you've
> expended some missiles while the enemy has expended
> fewer missiles.
What's the incentive to send a spacecraft at all if it is just going to
be shot down by lasers or enemy missiles? Note that my missiles are
pretty much spacecraft in their own right, uncrewed spacecraft that you
don't expect to return, but large with high ISP drives, defensive
capabilities (submunitions, possibly lasers), armor, good sensors and
communications equipment, and so on. Maybe I should call them drones,
or missile busses, or (to borrow from GURPS Transhuman Space)
autonomous kill vehicles.
The main problem now is keeping the cost low enough that you can afford
to not have your missile come back.
> The situation gets even less favorable for the attacker
> if you assume the existence of cheap low Isp defensive
> missiles.
Versus cheap, low ISP submunitions.
> That's why I tend to assume offensive missiles are fired
> from short-medium range and have comparatively low
> Isp. They need to be cheap enough to use en masse
> to brute force their way past cheap defensive missiles.
> This still leaves open the question of how the launching
> ship itself made its way past enemy laser fire, of course.
> I don't think thin skinned warships can plausibly do it,
> but maybe thick skinned "asteroid battleships" could.
> Maybe.
It could be traveling very fast (to give a small dwell time) with a
heavily armored front section (assuming you can keep the front always
oriented toward the lasers, which will not be true if facing multiple
craft) or heavy armor all around. Retract all sensors, comm arrays,
laser telescopes, and so on as you barrel through to close range. Then
pop everything out and let your missiles fly. If the beams only have a
few tens of seconds to burn through heavy armor, reasonable near future
lasers may not perform so well. I'm not talking asteroid thickness
armor here, just several layers of centimeter thickness armor plate.
Pop off a few sacrificial armor "plates" ahead of the craft
(essentially disks of armor a bit wider than the spacecraft's frontal
area) to soak up low ISP defensive rockets in your path.
Either that or just have longer range lasers than the other guys.
Luke
Luke Campbell
IsaacKuo wrote:
> This is the reason why I think the innermost layer of
> short range defenses should be to fire nuclear pulse
> units at relatively low velocity (maybe 1km/s or less).
> It's better to lob a dozen nukes at a BB swarm and
> vaporize the whole lot of them than it is to lose
> the ship.
Oh, I like this idea. A nuclear broom to sweep away the BB's. I'm
taking it.
> The issues of slew rate as well as 1/r^2 and 1/r^4 effects
> on sensors make it so that the best laser to defend your
> ship at point blank range is actually a laser on some other
> warship. This is one reason for spacing out your warships
> far from each other--it makes it easier to support each
> other with defensive laser fire.
Another idea is to launch what I call "mirsles" (mirror missiles) for
lack of a better term. Basically, it is a big focusing mirror on a
missile. Use your own laser to illuminate the mirsle, which bounces
the beam to wherever you need it. Not only can it give you a different
point of view to overcome slew rate limitations, it can greatly
increase the range of your own lasers (you now need to focus to a spot
the size of the mirsle mirror, not a lethally small spot. Use the
mirsle to focus down to dangerous spot size on the enemy).
> This depends upon how thick the armor needs to be. If
> the goal is to use the minimum mass required to protect
> from tiny impact debris, then this is ideal. However,
> once the thickness of the armor gets to be much greater
> than the diameter of the payload, then spacing the armor
> is less attractive due to the increased area being
> protected.
Well, yeah, if you need that much armor. I was just thinking of
defending against fragments and BB's, figuring hundreds of kg at tens
of km/s is hopeless.
Luke
Luke Campbell
Nyrath the nearly wise wrote:
> Fascinating! But could you have pity on a physics-challenged
> student and go into more details on the issues?
To first approximation, consider that the amount of material vaporized
will increase linearly with the kinetic energy. Part of this will be
the projectile, the remainder will have been part of the target. The
new momentum of the vaporized material (assuming it is well mixed) will
be the momentum of the impactor, but the increased mass means the
velocity will decrease by a factor of (impactor's mass)/(total
vaporized mass). If you assume the explosion in the rest frame of the
vaporized material is spherical and expanding at a constant rate (note
that this assumes a constant energy density of the vaporized material,
which is the only assumption consistent with the amount of material
linear in energy and thorough mixing) you can figure out the opening
angle of the cone of debris.
Now you can poke all sorts of holes in this argument, but I figure it
works for a first guess as to the amount of directionality of your
explosion.
> From my imperfect understanding, momentum is mass times
> velocity, while kinetic energy is one-half mass times
> the square of velocity.
>
> In other words: as projectile velocity rises, the
> kinetic energy goes up much faster than the momentum.
Yup, you've got it.
> Do you have any ballpark estimates relating
> KE:momentum ratios and sphericality of resulting explosion?
At 2 km/s, there is no explosion, the impact is entirely non-spherical,
and you can get horrendous penetration (this is the regime of anti-tank
cannon rounds). Guestimating from memory of photos of whipple shields
tested with hypervelocity guns, at 5 km/s, you have an opening angle of
maybe 1:5.
Luke
Nyrath the nearly wise
> The 40m lasers are a double edged sword. I used the Space Combat
> Workbook from Darkmatters (Nyrath's site has the links.) to examine
> them.
The spreadsheet is at
http://darkmatters.web1000.com/dwork.htm
Luke Campbell
Jarrod wrote:
> The 40m lasers are a double edged sword. I used the Space Combat
> Workbook from Darkmatters (Nyrath's site has the links.) to examine
> them. I had to dumb them down pretty severely (1000 nm wavelength
> etc.) or they completely dominate the battlefield.
1000 nm (1 micron) is actually a very reasonable figure for near future
lasers. The state of the art chemical laser (COIL, or chemical oxygen
iodine laser) emits at about a micron. The solid state laser the
military is looking towards to replace chemical lasers also lases at
about 1 micron (these are the various neodymnium lasers, which are also
the lasers that have the highest energy pulses ever generated - over 1
megawatt).
The main difficulty is that 1 micron beams are easily and efficiently
frequency doubled to 500 nm green light. You can also frequency triple
to near UV, but I don't know the efficiency on that. The range
increase for frequency doubling will probably outweigh the 20% losses
or so incurred.
The big issue I have is that a 40 meter mirror is friggin' huge. A ten
meter telescope is a state of the art major observatory with a cost of
over $100 million. Up to a few years ago, there were no telescopes
over 10 meters (I am not sure if there are currently any built that are
over this size, but I know the EU is planning on putting one in Chili).
To tone down the laser, the easist thing to do is reduce the mirror
size.
Luke
Luke Campbell
Rhysy wrote:
> "Except that the missiles are guided. You try to dodge them, they
> follow you. You try to leave the combat zone, they follow you."
> I did originally consider 10m diameter Orion missiles but they never
> made it in.
The delta-V advantage of orion missiles (assuming orion is your best
long range space drive) would argue strongly for using something like
this. Give each one lots of submunitions which it deploys just outside
of laser range.
> Give the missiles an hour to hit their target and the target
> has an hour to hit the missiles - surely more than long enough for any
> defensive system. Give them a minute and the chances of hitting them
> will be much reduced. It doesn't even matter about the individual
> performance of the defensive missiles (if indeed they are missiles),
> enough time allows you as many attempts to hit them as you have mass to
> spare.
Not necesarily. For instance, you can only try to shoot down the
missiles with lasers if they are within laser range. With low delta-V
defensive missiles, you again need to wait until the missiles are
close. In either event, you can't shoot them down when they are far
away. The other option is to shoot them down with your long range
(high delta-V) missiles. But you only have so many long range
missiles, and you can try shooting the incoming missiles down at any
range, so it doesn't really give you any more opportunity to blast the
bad guy missiles.
> "The light scattered from these gases and particulates can give a
> visible beam for a short distance before the target. You can get neat
> dynamic effects as the beam flickers into and out of visibility as the
> gas jets intercept it, as debris drifts into its path and flares
> brightly before vaporizing, and so on."
> Although this would indeed look quite spectacular - maybe even more so
> than solid beams - believe me it is much harder than it sounds. I doubt
> it would even be possible with the software I use.
I know I could do it with the 3d graphics software I use. Just get
some volumetric material and animate it, so it looks like youv'e got
jets of gas streaming out. Maybe add some particle fountains to
simulate the debris that will cross the beam.
> "A half ton missile impacting at 20 km/s will handlily take it out, no
> questions asked. "
> The whole ship ? How ?
By blasting a huge honkin' hole in it. At impacts greater than 5 km/s,
any matter held together by chemcial bonds will shock vaporize, and do
so with considerably more energy per unit mass than you would get from
chemical explosives. 20 km/s will give you 16 times the energy per
unit mass than you have at 5 km/s. So the impact of a half ton missile
will have the explosive effect of somewhere on the order of 25 tons of
TNT. Worse, because of the momentum of the impactor, the blast will be
directed toward the interior of the craft before spreading out and
smashing all the interior structures.
> "That they're even included at all is a bit silly. "
> You can never, EVER have enough backup.
If the backup takes up extra mass that could otherwise be used for more
effective weapons, you can have too much backup.
> "It takes much less energy to punch through a plate of steel with a
> fragment than it does
> to melt it. " - OK, but how wide a hole is a KE weapon ever likely to
> produce, given good armour ? I still find it very unlikely to cripple a
> well-designed ship.
That's how modern ships are crippled. Also tanks, fighter planes,
APCs, and any other peice of military equipment. Breaking things is
always more efficient than burning.
>
> "If you use the "does it have enough energy to melt the target"
> criteria, then every weapon ever used short of a nuke impossibly short
> on power" - what about lasers ?
Pulsed lasers blast, not melt. CW lasers may need to melt (or perhaps
vaporize) part of the target, but not the whole thing! They would burn
a hole to reach a vulnerable spot. You kill a person by shooting their
heart or brain, not by burning their entire body to ashes. You kill a
car by cracking its engine block or shooting out its tires or rupturing
a fuel line or something, not by melting it to slag. the same
principle applies to spacecraft.
Luke
Eivind Kjorstad
> Give the missiles an hour to hit their target and the target
> has an hour to hit the missiles - surely more than long enough for any
> defensive system. Give them a minute and the chances of hitting them
> will be much reduced.
Why ? If you've got 200 defencive missiles, and there are 100 incoming,
you've got 2 chances of hitting each.
This is true regardless of the timeframe being an hour or two minutes.
You are constantly forgetting that there are, in practice, no limits on
the rate of fire of missiles in a space-battle.
> enough time allows you as many attempts to hit them as you have mass to
> spare.
Yes. So it comes down to a numbers-game; defensive-missile times
accuracy-of-defence verses attacking-missiles.
> "A half ton missile impacting at 20 km/s will handlily take it out, no
> questions asked. "
> The whole ship ? How ?
By imparting 20GJ in a split-second, thus causing a massive explosion ?
> "That they're even included at all is a bit silly. "
> You can never, EVER have enough backup.
You most certainly can.
Backup means extra weigth. Which means you can't have more backup
without having *less* of something else.
The moment that "something else" improves your capabilities more than
the backup does, you're better off with "something else". If you install
more backups at that point, you have not only enough backup, but indeed
too *much* backup.
> "It takes much less energy to punch through a plate of steel with a
> fragment than it does to melt it. " - OK, but how wide a hole is a KE
> weapon ever likely to produce, given good armour ? I still find it very
> unlikely to cripple a well-designed ship.
It depends on the velocity, the weigth, and if it's a single big hit or
(more likely) the attacker uses a small charge to spread out before
impacting.
The 10.000 10g ballbearings going at 20km/s is (up to) 10000 2MJ
impacts, which means each impact is equivalent to 500g of TNT.
If your KE-vehicle can somehow reach 40km/s, then each 10g impact is
equivalent of 2kg of TNT.
Eivind Kjørstad
Eivind Kjorstad
> Strangely though, people have also raised issue with the unguided
> weaponary (which only amounts to a few guns anyway - I barely even
> mentioned it in the battle plan). Yet others think that unguided ball
> bearings are going to be devastating weapons !
Nope. People are talking of guided missiles with a small chemical charge
surrounded by lots of BB as the warhead.
> Firstly, unguided weaponary may have two uses : Actually causing damage,
> or causing the opponent to expend resources to avoid it (either
dodging at high
> distances - which I find highly suspect
What's suspect about it ? You'll hardly need to do it at all -- the
enemy will, in 999999 out of a million tries miss by himself, without
you needing to dodge at all.
> Finally, as I've said, I don't find these immensive velocities
> plausible (I would stress that this is not from orbital considerations,
> just from a tactical point of view).
If you're not going to move quickly, why then do you have an orion at
all ? What is unplausible about a ship with perhaps 500km/s of total
deltaV moving at 10km/s or 100km/s ?
> There are missile turrets so that they can be pointed towards the enemy
> and save -albeit slightly- on propellant.
Makes sense. *NOT*.
If the missiles have say 30km/s of deltaV, and you need 3m/s of deltaV
to turn the missiles 180 degrees, then the "savings" amount to 0.01% of
the missiles deltaV. To get these "savings" you propose a turnable
missile-turret, loading-mechanisms for this plus the needed support on
the missile for being "loaded", then wait for the turret to turn, then
launched.
If you invested that extra mass in the missiles themselves you'd get a
lot more extra deltaV for the same mass-budget.
> Issac :
> "In contrast, with two turrets per ship nowhere is safe from being
> targetted. " - depends on ship shape.
It does ? Mention a ship-shape where 2 turrets on the rigth spots cannot
fire in all directions !
> Anyway I wasn't thinking of these very high velocities and distances,
> which don't sound at all practical to me.
Space is big. Orion spaceships can move fast. If that's "unpractical"
for the battle you had imagined, then perhaps the problem is with your
imagination ?
What *would* be completely unreasonable would be to have lasers capable
of killing from 10.000km, missiles capable of killing from a million km
away, with 50km/s of deltaV. All on ships travelling billions of kms
with 100km/s or more of deltaV.
But still insist that battles are fougth at 100km distance, at
walking-speed.
> "With any reasonable spaceship a single hit by a nuke will mean instant
> kill." - the nukes referred to in that context are small, sub-kiloton
> nukes,
Why would you have a 0.1kt nuke when that has more or less identical
size and mass as a 100kt one ?
> Quick check (crossing fingers hoping not to slip up with the
> calculator) : say the spaceship is made of steel for argument's sake.
> The latent heat of fusion is 247 J/g. Let the nuke by 0.1kt (certainly
> doable in a small missile or artillery shell - admittedly it could
> probably be quite a bit higher). That's a total of 4.18*10^11 J
> available, enough to melt 1.692*10^9g, or 1692 tonnes of steel - some
> nasty damage but hardly anything like lethal.
That goes from silly to utterly ridicolous. 99.99999% of all craft that
where disabled in the history of warfare where disabled by an amount of
energy several orders of magnitude away from the energy required to
completely melt them.
By your logic, currently used KE anti-tank rounds would have no effect
on modern tanks -- since they have orders of magnitude too little energy
to completely melt the tank. This fails to match reality....
> And that's ignoring the (substantially greater amount of) heat needed
> to raise the steel's temperature to boiling point,
Yes. Because *completely* melting all metal in a spaceship is not enough
to missionkill it. You need to *evaporate* it to achieve that !
> Whereas even at 100km/s, a speed, as I've said, seems very unlikely
> for combat at any kind of reasonable distance, the KE of the ball
> bearing turns out to be 50 megajoules. Ho hum. It would therefore
> take 494,000 such ball bearings to do the job,
Correct. If "the job" was completely melting the target.
The rest of us are satisfied with reducing the target to shrapnel, a
task which requires orders of magnitude less energy.
> I therefore sumbit that no plausible KE weapon under any remotely
> plausible circumstances has any chance of causing a kill to warship of
> specified design.
I submit that no reasonable person would confuse the task of
mission-killing a vehicle with the task of completely melting, or
completely vaporizing the same vehicle.
> "Which would perhaps make it exciting, except that is *PRECISELY* how
> 99% of the viewers will expect the figth to go, long before its even
> started. D for originality." - There are a great many historial
> examples of battles being won against seemingly overwhelming odds.
Yes. But many many many more examples of battles being LOST against
overwhelming odds.
Furthermore, that wasn't my complaint. My complaint was the utterly
stereotypical "first we lose some forces, and appear to be near-defeat,
then we miracolously return by some clever trick and win."
0.1% of real battles go like that. 99.9% of hollywood-battles go like that.
> You want to argue Julius Ceaser was "unoriginal" for defeating
> numerically superior opponents by using superior armour and
> training... riiiight.
Caesar (not "Ceaser") was not trying to entertain an audience. You've
multiple times defended unrealistic choices by saying it's nessecary to
stray from the realistic in order to improve on entertainment-value.
Now, suddenly, you turn around and claim that though this plotline is
devastatingly boring, it's nessecary because its "realistic", as in, it
has happened (the oposite has also happened, infact far more often...),
therefore it must happen in your story, despite being boring and
predictable.
Go ahead. Make another epic space-battle where:
a) Realism is sacrified on the altar of entertainment.
b) The story *fails* to be entertaining, because it's utterly
predictable, following the path set by hundreds of hollywood-figths.
Leaving you with pretty eye-candy. But without realism. And without an
interesting story or anything resembling a surprise.
Eivind Kjørstad
IsaacKuo
> IsaacKuo wrote:
> > For missile defense, I see short range
> > missiles/projectiles as being more efficient than lasers. Defensive
> > "bullets" don't need to be launched at high velocities, and yet
> > they can use the kinetic energy of the incoming against itself.
> > Lasers never get this "free energy" boost.
> The slower and more numerous the incoming projectiles, the better
> lasers will be defensively compared to short range projectiles. Slower
> means more time to engage, more numerous means you can run out of
> defensive projectiles. Where the break-even point is, I don't know.
Slower, yes. Going slower also eliminates the "free
energy" boost that defensive physical projectiles get.
More numerous, no. Being more numerous makes
both laser defense and projectile defense more difficult.
Laser defenses are challenged because it takes longer
to engage more projectiles. Projectile defenses are
challenged because it takes more ammo to stop more
projectiles.
> > That's really the problem--how do these long range missiles
> > survive in the face of extended exposure to long range laser
> > fire? Even with an effective range of only, say, 12,000km, it
> > would take even a fast 100km/s missile two minutes to
> > cross the distance. If each laser can take out one missile
> > per second, then a fleet of ten ships could wipe out a wave
> > of a thousand fast missiles with laser fire alone.
> So my fleet of ten ships launches ten missiles. Each of which carries
> 130 submunitions which are deployed 13,000 km away. Not looking so
> good for the defenders now. Unless, of course, I've got bad
> intelligence and your lasers have a range of 14,000 km, in which case
> my missiles don't do squat.
That still only leaves maybe a hundred submunitions left
over which need to be dealt with by expending missiles
defensively (whether those missiles are "expensive" offensive
missiles or "cheap" submunitions/defensive missiles or "dumb"
externally guided projectiles or whatever).
> I've always leaned towards really large missiles with high ISP drives
> carrying lots of guided submunitions with low ISP, high thrust rockets.
> Mix 'n match BB canisters with nukes to your heart's content.
I lean toward the same basic approach, except I don't call
the bus vehicles "missiles". I call them "warships", or "fighters".
It's a question of semantics, really. On the one hand, a
"warship" implies something which is expected to return if
it survives. On the other hand, a "missile" implies something
which isn't expected to return.
So should these high Isp bus vehicles be called "warships"
or "missiles"? As I see it, with a nice high Isp drive, it makes
more sense for these bus vehicles to travel alongside the
smart "command" vehicles rather than being carried by them.
(Carrying big heavy expensive "missiles" is an expensive
proposition in and of itself.) Thus, most of the time they act
like "warships", patrolling alongside the command vessels
and only occasionally pulling up to a tender for refueling and
maintenance. It's only when they're sent on a mission that
they may start acting like "missiles"--maybe. Depending on
the tactical situation and the remaining fuel, it could go either
way. Sometimes, it may make most sense to make a
missile-like "suicide run", at the end of which the bus vehicle
is either destroyed or careening out of the solar system.
Sometimes, it may make most sense to maneuver
in a way that might be recoverable.
So, semantic differences aside, what we're really quibbling
over is the best time to deploy the submunitions/cheap missiles.
You're proposing to deploy them just outside enemy laser
range and overwhelming them with sheer numbers. I'm
proposing to somehow survive enemy lasers to deploy
them at short range.
> > If we consider a simplified scenario where there are no short
> > range defenses, then we still have the matter of the target's
> > own offensive long range missiles. If both you and the enemy
> > have ten thousand missiles, then the enemy can defend
> > against your missiles by shooting them down with their
> > own missiles. Any missiles that they can take out with
> > long range lasers are a bonus.
> The part where offensive missile meets defensive missile becomes
> interesting. How many do you deploy to counter the defensive missiles
> by launching their submunitions? How many defensive missiles
> concentrate on the submunitions vs the missiles that still pose a
> threat to the main spacecraft?
> In the end, I suspect it boils down to whomever has the most missiles.
I think modern day practice is to to have two missiles per
threat--so that when one reaches the target there's already
another one on its way. If that threat launches another
threat, then you fire more missiles to deal with that one also.
This points out one advantage to offense which we've so far
ignored. In offense, you don't really care very much about
the possibility of a miss. No big deal. But in defense, the
costs of a miss are so great that you'd rather waste twice
as much ammunition than risk something getting through.
> > So what's the incentive to fire your missiles from outside
> > laser range? The enemy will shoot down some or all of
> > them with lasers, and then the rest get taken out by the
> > enemy's own missiles. The end result is that you've
> > expended some missiles while the enemy has expended
> > fewer missiles.
> What's the incentive to send a spacecraft at all if it is just going to
> be shot down by lasers or enemy missiles?
Good question. Better hope you have better lasers than
the other guy. ;)
> Note that my missiles are
> pretty much spacecraft in their own right, uncrewed spacecraft that you
> don't expect to return, but large with high ISP drives, defensive
> capabilities (submunitions, possibly lasers), armor, good sensors and
> communications equipment, and so on. Maybe I should call them drones,
> or missile busses, or (to borrow from GURPS Transhuman Space)
> autonomous kill vehicles.
> The main problem now is keeping the cost low enough that you can afford
> to not have your missile come back.
I don't think this is really such an issue, as long as the intended
target costs a lot also. Obviously, you'd LIKE to be able to
dispatch expensive enemy equipment with a low solution.
So would the enemy. Unless you're a lot cleverer than the
enemy, you shouldn't be disappointed by rough parity in
expenses.
> > That's why I tend to assume offensive missiles are fired
> > from short-medium range and have comparatively low
> > Isp. They need to be cheap enough to use en masse
> > to brute force their way past cheap defensive missiles.
> > This still leaves open the question of how the launching
> > ship itself made its way past enemy laser fire, of course.
> > I don't think thin skinned warships can plausibly do it,
> > but maybe thick skinned "asteroid battleships" could.
> > Maybe.
> It could be traveling very fast (to give a small dwell time) with a
> heavily armored front section (assuming you can keep the front always
> oriented toward the lasers, which will not be true if facing multiple
> craft) or heavy armor all around. Retract all sensors, comm arrays,
> laser telescopes, and so on as you barrel through to close range. Then
> pop everything out and let your missiles fly. If the beams only have a
> few tens of seconds to burn through heavy armor, reasonable near future
> lasers may not perform so well. I'm not talking asteroid thickness
> armor here, just several layers of centimeter thickness armor plate.
Yes, yes. It's just that I personally don't care for assuming
"near future" lasers, when I don't expect that we'll even have
any interplanetary assets to fight over within that "near future".
> Either that or just have longer range lasers than the other guys.
Isaac Kuo
IsaacKuo
It's worth noting that even with practically spherical explosions,
you can acheive deep penetration with multiple impactors
spaced out in a line. Each impactor blasts out a hole which
the later impactors travel through.
One way to do this is with a "metal storm" like warhead (I like
the "pile gun" concept because it eliminates the mass of the
barrels). Just before impact, the "gun" fires projectiles in a
line with a stupendous rate of fire.
Isaac Kuo
IsaacKuo
Luke Campbell wrote:
>The big issue I have is that a 40 meter mirror is friggin' huge. A ten
>meter telescope is a state of the art major observatory with a cost of
>over $100 million. Up to a few years ago, there were no telescopes
>over 10 meters (I am not sure if there are currently any built that are
>over this size, but I know the EU is planning on putting one in Chili).
>To tone down the laser, the easist thing to do is reduce the mirror
>size.
I also find a 40meter mirror rather large, but not on the
grounds that it would be challenging to build. My issue
with it is that it's too vulnerable to enemy laser fire.
I can't think of a way to protect it in a way that it
could quickly "pop up" to fire. Assuming no clever "pop
up" mechanism is practicable, the mirror is exposed and
vulnerable to enemy fire. All the enemy needs to do is
slightly darken any part of the mirror and your own laser
will do the rest of the job.
I prefer a turret similar to ABL's, where the mirror
diameter is maybe 70% of the turret diameter. The
mirror can thus be protected from enemy fire by
concentric turret "shells" with ~90 degree windows.
To "pop up", the mirror stays still while the shells
rotate to align the windows with where the mirror is
aimed.
Intuitively, I think this would be too bulky and take
too long to open/close on the scale of 60m.
Isaac Kuo
Luke Campbell
> Luke Campbell wrote:
> I also find a 40meter mirror rather large, but not on the
> grounds that it would be challenging to build. My issue
> with it is that it's too vulnerable to enemy laser fire.
>
> I can't think of a way to protect it in a way that it
> could quickly "pop up" to fire. Assuming no clever "pop
> up" mechanism is practicable, the mirror is exposed and
> vulnerable to enemy fire. All the enemy needs to do is
> slightly darken any part of the mirror and your own laser
> will do the rest of the job.
If you have a 40 meter mirror, and only a few tens of megawatts of time
average laser power, slightly darkening the mirror wouldn't do much
other than slightly reducing the beam energy on target.
> I prefer a turret similar to ABL's, where the mirror
> diameter is maybe 70% of the turret diameter. The
> mirror can thus be protected from enemy fire by
> concentric turret "shells" with ~90 degree windows.
> To "pop up", the mirror stays still while the shells
> rotate to align the windows with where the mirror is
> aimed.
Just for kicks, I went and designed a laser beam directing scope. It
is a 3D model, and all the mirrors actually work. Parallel light is
bounced around and reflected out so as to form a beam that can be
focused to a point at any desired distance. Some quick renderings
below
http://panoptesv.com/zoe/wheels/Pics/Scope2.JPG
http://panoptesv.com/zoe/wheels/Pics/Scope3.JPG
http://panoptesv.com/zoe/wheels/Pics/Scope4.JPG
http://panoptesv.com/zoe/wheels/Pics/Scope5.JPG
http://panoptesv.com/zoe/wheels/Pics/Scope6.JPG
http://panoptesv.com/zoe/wheels/Pics/Scope7.JPG
http://panoptesv.com/zoe/wheels/Pics/Scope8.JPG
http://panoptesv.com/zoe/wheels/Pics/Scope9.JPG
http://panoptesv.com/zoe/wheels/Pics/Focus1-f30.JPG
http://panoptesv.com/zoe/wheels/Pics/Focus1-f1E4.JPG
http://panoptesv.com/zoe/wheels/Pics/Scope10.JPG
http://panoptesv.com/zoe/wheels/Pics/Scope11.JPG
http://panoptesv.com/zoe/wheels/Pics/Scope12.JPG
http://panoptesv.com/zoe/wheels/Pics/Scope13.JPG
I also have a partially completed ABL spherical turret version, but am
not really happy with the way it needs an expanding mirror in the beam
path. It is more compact, though.
Note that these renderings were with the beam in atmosphere, not in
space, so you can see the beam. Unfortunately, I couldn't find a way
to do volumetric causitcs, so I had to cheat a bit to make the beam
visible by putting a spotlight at the focus and shining it back at the
scope's primary mirror. The virtual light really is being focused,
though, even though you can't see it (for the two named Focus1-f*.JPG
you can see the light being focused on a screen).
Jarrod
The only plausible justification I can think of for gigantic
battleships is the need to scale up the pusher plates for improved
effective exhaust velocity. (Sorry, Thunderchild has a fatal design
error now.) Any smaller vehicles will automatically have lower
effective exhaust velocities. This suggests keeping the missiles on
the launch platform until the last possible moment. The missiles must
then sprint over a relatively short distance to have any chance of
hitting the target. If the target has sufficient time, its superior
exhaust velocity will trump the missile's superior thrust. If the
missile doesn't have superior thrust in the first place, it has
almost no chance.
Consider this case: The target is a uniform sphere 50m in diameter.
The target is capable of 10 m/s^2 acceleration in any direction. A
projectile is approaching at 20 km/s. The launcher already knows the
target's position and velocity and has aligned the projectile for a
direct center hit. If the starting distance is 1000 km, the target has
50 seconds to accelerate. In that time it can move its center point
12,500 m normal to the projectile's trajectory. It will easily dodge
an unguided projectile. If the starting distance is 44.7 km the
projectile will cut a half-diameter hole in the edge if the target.
Anything closer than this and the projectile always hits. The freshman
physics relationship is:
Position = 1/2 * Acceleration * Time^2.
Adjust the numbers to suit the specific case. This gives some feel for
how effective unguided projectiles will be. The example can also be
generalized to guided projectiles if the starting point is taken as the
last course correction.
It is also possible to describe an area the target may be in given a
certain amount of time. Using the same numbers as above, a canister
uniformly distributes a cloud of projectiles 100 km from the target.
The target can be anywhere within an area of 70,686 square meters at
the time of impact. The target itself is 1,963 square meters in cross
section. Therefore 36 projectiles are needed to guarantee one of them
will hit. (97% of the projectile mass is wasted!) This example can be
extrapolated to ballpark estimate the effectiveness of shrapnel against
battleships or missiles at any range. After having run this
calculation a few times with different parameters I am convinced that
shrapnel is ineffective unless it is being launched in enormous
quantities from a surface installation or orbital stockpile or unless
it is used at extremely close range. There is however another reason
to dislike shrapnel at close range. A cloud of shrapnel just won't
penetrate like a well designed solid of equal mass.
IsaacKuo
Jarrod wrote:
> Random Thoughts:
> The only plausible justification I can think of for gigantic
> battleships is the need to scale up the pusher plates for improved
> effective exhaust velocity. (Sorry, Thunderchild has a fatal design
> error now.)
Another possible reason is to minimize overall costs.
Civilian transport vessels would rather send a payload
in one or two huge vehicles propelled by big pulse
units rather than a dozen small vehicles. The economies
of large vehicles is what led to the development of
supertankers. Military vehicles could adapt from
those principles applied to civilian transports.
To minimize overall costs per kg of payload, you might
want to use very high impulse pulse units with a
medium sized nuke and a much larger block of inert
thermal propellant. This produces a lot of thrust but
has a lower Isp than an Orion drive's theoretical maximum.
This can save you fuel costs by producing more impulse
per nuke, but not if you go too far with it and lose all your
gains due to extra dead mass. You want the mass ratio
to be close to the 4.92 optimum (3.92 parts fuel vs 1 part
ship dry weight).
For example, you might start off with a base design of a
high Isp Orion drive with a 10,000sec specific impulse.
In order to optimize costs, you might pad out the pulse
units with cheap inert material which brings the Isp down
to 2,000sec. Roughly speaking, this increases the
amount of impulse generated by each pulse unit five-fold.
That means the pusher plate is going to have to
widthstand five times as much of a shove as with the
baseline design!
Isaac Kuo
Nyrath the nearly wise
> Just for kicks, I went and designed a laser beam directing scope. It
> is a 3D model, and all the mirrors actually work. Parallel light is
> bounced around and reflected out so as to form a beam that can be
> focused to a point at any desired distance. Some quick renderings
> below
> http://panoptesv.com/zoe/wheels/Pics/Scope2.JPG
> http://panoptesv.com/zoe/wheels/Pics/Scope3.JPG
> http://panoptesv.com/zoe/wheels/Pics/Scope4.JPG
> http://panoptesv.com/zoe/wheels/Pics/Scope5.JPG
> http://panoptesv.com/zoe/wheels/Pics/Scope6.JPG
> http://panoptesv.com/zoe/wheels/Pics/Scope7.JPG
> http://panoptesv.com/zoe/wheels/Pics/Scope8.JPG
> http://panoptesv.com/zoe/wheels/Pics/Scope9.JPG
> http://panoptesv.com/zoe/wheels/Pics/Focus1-f30.JPG
> http://panoptesv.com/zoe/wheels/Pics/Focus1-f1E4.JPG
> http://panoptesv.com/zoe/wheels/Pics/Scope10.JPG
> http://panoptesv.com/zoe/wheels/Pics/Scope11.JPG
> http://panoptesv.com/zoe/wheels/Pics/Scope12.JPG
> http://panoptesv.com/zoe/wheels/Pics/Scope13.JPG
Those are excellent!
Nyrath the nearly wise
> Rhysy wrote:
>> "The light scattered from these gases and particulates can give a
>> visible beam for a short distance before the target. You can get neat
>> dynamic effects as the beam flickers into and out of visibility as the
>> gas jets intercept it, as debris drifts into its path and flares
>> brightly before vaporizing, and so on."
>> Although this would indeed look quite spectacular - maybe even more so
>> than solid beams - believe me it is much harder than it sounds. I doubt
>> it would even be possible with the software I use.
>
> I know I could do it with the 3d graphics software I use. Just get
> some volumetric material and animate it, so it looks like youv'e got
> jets of gas streaming out. Maybe add some particle fountains to
> simulate the debris that will cross the beam.
Just for the record Rhysy is using Blender, which
is a surprisingly powerful package, but with a few
annoying limits.
Rhysy
mistake, I am not familar with the Groups thing), replies won't be in
any particular order either.
"What, and you're just going to pander to the lowest common
denominator?"
Oh my yes ! And sound effects too (realism zealots can always press the
mute button, after all).
"The chemical warhead does not directly threaten the ship- it's a means
to
disperse a cloud of shrapnel which threatens the ship. "
Ah, thanks.
"Pulsed lasers, which rely on the mechanical shock produced by rapidly
and
repeatedly heating/vaporizing surface material in order to tear the
target
apart can do more damage per watt than continuous beam lasers trying to
melt/vaporize a hole in the target. "
Fair enough.
"Closer and slower=easier to kill."
Which is an advantage as well as a disadvantage.
" Now if you can justify setting your battle in a large, diffuse gas or
dust cloud..."
As nyrath says, volumetric effects are not possible in Blender (without
clever tricks that seriously slow things down). This is a shame because
the idea is awesome - a fight near a comet could look pretty
impressive. On the other hand I'd then probably end up dumping realsim
altogether and go for cool-looking explosions. Still, I really don't
see having beams visible as a big deal. May as well make something look
pretty.
" The guy with more missiles wins. Firing early or firing late doesn't
really make much of a difference. "
Well, this is assuming someone has a truly decisive advantage in
missiles. If they are about equal, both sides will entirely destroy
each others missiles without inflicting damage on their opponents. Or
if they have defensive guns/lasers they at least get a very long time
to accurately target and destroy the incoming missiles with minimum
losses to themselves. Moreover for there to be any chance of success,
each side is going to have to expend ALL (or nearly so) of its missiles
at once and hope some make it through. Firing any less - assuming
approximately equal numbers - guarantees success for the opponents. I
think the defense systems will be more important though, especially for
lasers, as at very long range they'll get all the time they need to
shoot the missiles.
However, if they are very much closer, they may saturate the enemy
defensive systems without even needing to fire everything at once,
since it takes a finite amount of time for any system to work. Their
missiles become far more effective, and it comes down to a contest of
missile speed, destructive power, accuracy and reliability. Lasers may
throw a spanner in the works if they can truly target at very large
distances, since they may target the ship directly and still have time
to deal with the missiles. But that depends on the range and time
needed to cripple the ships/missiles.
"The same way an asteroid impact causes a huge crater. It causes a huge
explosion which pushes parts of the ship through other parts of the
ship (most notably,
little fragments perforate the rest of the ship). "
An asteroid impacts the ground, which is solid for thousands of miles.
A spaceship is much thinner, more like a wall. No matter how fast you
through a small object at a wall, it isn't going to break the whole
wall, just punch a hole.
"There are a LOT of guns and gauss cannons! For a backup weapon not
expected to be used, there really would only be one or two. "
There are 12 guns and 4 Gauss cannons. It's only prudent to ensure all
weapons systems have no blind spots. The Gauss cannons are not backup
weapons. Compare with the missile turrets at 32 each per volley.
"A gun can be fired more than once; a missile is a one shot. "
Missile turrets can be reloaded just like a gun.
"Yes, you can."
Well yes, okay you CAN, but only if you make the bizzare decision to
have it take up a significant proportion of the mass.
"Second, a gun has a significant mass and expense built in to the
firing/loading/aiming mechanisms themselves. In today's warships, the
gun represents a major investment and involves many design
complications. It wouldn't be included at all if it weren't deemed
essential. "
The 100mm guns aren't big enough to take up anywhere near a significant
mass, or their rounds for that matter.
"The pusher plate is more likely to survive an impact in a functional
state than anything else on the ship. "
Not according to George Dyson's book, which clearly states that they
were very worried about dud bombs where the chain reaction didn't
occur. Bomb sharpnel was viewed as potentially lethal to the plate.
"If you're using pneumatic pistons, these can be placed within the hull
of the ship. The "legs" exposed on the outside of the ship may be
simply hollow metal rods. "
Not quite sure what you mean here.
"In many situations, you don't even really care that much about losing
your thrusters since you're already cruising toward your intended
destination anyway. If
you later need to repair your drive system or abandon your ship at the
destination, then so be it. "
Possibly, it depends on whether you need to maneuver for whatever
tactics are being used or not. If your main drive is killed, you have
to hope someone wherever it is you're going will come rescue you, or
you'll just keep going. Though you can keep fighting without a plate,
you'd better hope you win the battle, or you're stranded with a mob of
angry enemies surrounding you.
"Well, that's okay, assuming your goal is to produce yet another
example of non-realistic space battles."
I choose to read that as "Yes, I confirm that a line of battle relies
on long distances between ships."
"My thoughts tend to concentrate on depictions of tactical displays
within the warships."
I quite like that idea. Two problems here - it might look strange to
show the internal display without showing people (lack of ability on my
part), and I might be tempted to take the Star Trek TNG approach to
battles and just show a flash on a screen when a ship is meant to be
exploding... I would prefer to go for an entirely space-based camera.
"The big issue I have is that a 40 meter mirror is friggin' huge. A
ten meter telescope is a state of the art major observatory with a cost
of over $100 million. "
As I said the 40m laser is replaceable. There are (or at least were,
haven't heard much for a while) plans for a segmented 60m mirror,
though I suppose it would be better there to just treat each segment as
a seperate mirror.
"The only plausible justification I can think of for gigantic
battleships is the need to scale up the pusher plates for improved
effective exhaust velocity. "
Larger ships could also carry more weapons and more armour. Also -
skating on perilously thin ice - is the pusher size going to make much
difference when the nuclear explosion can be directed ?
IsaacKuo
Rhysy wrote:
> Since posts seem to occur in somewhat irregular order (pardon my
> mistake, I am not familar with the Groups thing), replies won't be in
> any particular order either.
The usual thing on USENET is to reply to individual posts
individually, and to attritube quotations. You may notice
that there's a certain standard way this is done, using
"> " marks. With Google Groups, it's easy to quote replies
in the standard way. You just click on "show options" and
hit the "reply" link.
Make sure to delete excess lines that aren't relevant to
your reply. Leave just enough to establish the context.
> "What, and you're just going to pander to the lowest common
> denominator?"
> Oh my yes ! And sound effects too (realism zealots can always press the
> mute button, after all).
Sound is something which typically isn't depicted in
a "realistic" manner regardless of genre. For example,
a common cinematic technique is to show a couple
characters from a significant distance. The audience
can hear them talking to each other even though realistically
they'd be hard to hear (if they could be heard over the
background noise at all). Similarly, it's common to show
bomb explosions or gun blasts from a distance and hear
the explosion the same instant it's seen. In the real world,
there's a time delay between when you see the flash and
when you hear the boom.
Essentially, the general convention is that the sound you
hear is what you'd hear if you were at the focus of
attention, rather than if you were at the location of the
camera. Thus, you should hear an explosion if the
camera is focused on the ship which is exploding; you'd
hear the humm of the reactor and the cracks of pulse
laser discharges if the camera is focused on a ship
firing its lasers.
However, if you're looking at a first person view of a
fire director or an "over the shoulder" shot, then you
wouldn't hear the explosion of the target. Instead,
you'd hear what the guy behind the firing sight would
hear, or what someone on board the firing ship would
hear.
This may seem a bit confusing, but it conforms to
audience expectations.
> "The same way an asteroid impact causes a huge crater. It causes a huge
> explosion which pushes parts of the ship through other parts of the
> ship (most notably,
> little fragments perforate the rest of the ship). "
> An asteroid impacts the ground, which is solid for thousands of miles.
> A spaceship is much thinner, more like a wall. No matter how fast you
> through a small object at a wall, it isn't going to break the whole
> wall, just punch a hole.
That's completely wrong. When a small object hits a wall with
greater areal density than it, the result is essentially a spherical
explosion centered just inside the wall's outer surface.
Your ships are large enough so that any hypervelocity impact
with any incoming missile is guaranteed to blow up in a spherical
explosion centered just inside the impact point, rather than
blowing through.
> "There are a LOT of guns and gauss cannons! For a backup weapon not
> expected to be used, there really would only be one or two. "
> There are 12 guns and 4 Gauss cannons. It's only prudent to ensure all
> weapons systems have no blind spots. The Gauss cannons are not backup
> weapons. Compare with the missile turrets at 32 each per volley.
You only need two turrets to have no blind spots. Even one will
suffice if you can roll the entire ship quickly enough.
> "Yes, you can."
> Well yes, okay you CAN, but only if you make the bizzare decision to
> have it take up a significant proportion of the mass.
The sheer number of guns and gauss cannons you've littered
the ships with will take up a significant proportion of the mass.
You may not understand just how heavy large calibre guns
and their supporting systems are compared to missile tubes.
Guns need to handle harsh recoil shocks, and need heavy
precision actuators and turret mechanisms to slew them around.
A missile tube only needs to be strong enough to survive a
low pressure gas puff to eject the missile. Unlike modern
naval vertical launch, these gas puffs don't even need to be
powerful enough to overcome 1gee.
> "The pusher plate is more likely to survive an impact in a functional
> state than anything else on the ship. "
> Not according to George Dyson's book, which clearly states that they
> were very worried about dud bombs where the chain reaction didn't
> occur. Bomb sharpnel was viewed as potentially lethal to the plate.
That's talking about a delicate small scale civilian design
proposal with an unarmored hull behind the pusher plate.
Any hole in the pusher plate is a complete failure because
then the ship itself would get destroyed.
You're considering a massive military vehicle with thick
hull plating behind the pusher plate. A few holes here
and there--even pretty big ones--means a reduction in
capability but the sturdy ship behind the plate will survive.
Indeed, with the huge ships you're proposing, I question
whether the pusher plates are even necessary.
> "If you're using pneumatic pistons, these can be placed within the hull
> of the ship. The "legs" exposed on the outside of the ship may be
> simply hollow metal rods. "
> Not quite sure what you mean here.
I mean that the pneumatic pistons can be placed within
the hull of the ship. These are attached to metal rods
which extend through the surface of the hull to the outside.
Those rods extend outside the ship all the way to the
pusher plate.
> "Well, that's okay, assuming your goal is to produce yet another
> example of non-realistic space battles."
> I choose to read that as "Yes, I confirm that a line of battle relies
> on long distances between ships."
You can read it any way you want. You'll be wrong, but
feel free to do so anyway.
If you actually care about what I mean, it's simply this:
REALISM relies on long distances and high velocities
between the opposing forces.
If you want to produce an unrealistic space battle, then
anything you feel like is okay. It doesn't matter. Make
space fighters fly around like WWII fighters if you want,
shooting visible unguided blaster beams at each other
and blowing up Death Stars with proton torpedoes.
Knock yourself out.
Isaac Kuo
Jarrod
> Larger ships could also carry more weapons and more armour. Also -
> skating on perilously thin ice - is the pusher size going to make much
> difference when the nuclear explosion can be directed ?
I expect more weapons and armor would be better carried on multiple
small vehicles rather than a few big ones if the rocket performance of
those vehicles is independent of size. Since you have already
committed to having large battleships I think it makes the most sense
to assume the missiles cannot match battleship rocket performance over
any great distance. They are restricted to high thrust sprints. This
already conforms to your battleplan as I interpreted it.
My understanding of the variables that contribute to Orion effective
specific impulse is incomplete and slated for improvement. However I
think it can be said conclusively that increasing the plate diameter is
the number one way to improve rocket performance. The ability to focus
the blast onto the pusher plate is finite and never enough to justify a
plate diameter smaller than the hull diameter.
IsaacKuo
Jarrod wrote:
> My understanding of the variables that contribute to Orion effective
> specific impulse is incomplete and slated for improvement. However I
> think it can be said conclusively that increasing the plate diameter is
> the number one way to improve rocket performance. The ability to focus
> the blast onto the pusher plate is finite and never enough to justify a
> plate diameter smaller than the hull diameter.
Yes, although of course the converse may be a great idea in
many cases (a pusher diameter larger than the hull diameter).
The extreme case is with a large "Medusa" type sail in front
of the main ship. This could acheive higher specific impulse
and/or higher efficiency. A huge mag-orion sail could acheive
Medusa-like performance without such a huge unweildy sail.
On a military vehicle, I think mag-orion is the more viable
concept. When outside of enemy weapons range, the high
performance magsail may be deployed. But the sail must
be reeled in and stowed before engaging the enemy. At
that point, the pulse units could still be used for tactical
maneuvers by detonating them at shorter distances (pushing
a sturdy physical pusher plate and/or the hull directly).
Still...if you scale up a space warship to huge proportions,
you could acheive medusa-like performance with a normal
pusher plate.
The traditional Orion shaped charge ideally blasts half of
the gas straight forward and half of the gas straight backward.
This results in a theoretical ideal of 100% efficiency, when
the gas traveling forward perfectly bounces off the pusher
plate to end up moving straight backward. Thus, all of the
exhaust gas ends up moving straight back. In the case
where the ship is currently moving at roughly the exhaust
velocity, all kinetic energy is transfered to the ship and no
kinetic energy is wasted on the exhaust.
Sounds great, right? The problem, of course, is that the
theoretical ideal can't be acheived. In particular, it's not
so straightforward to make an efficient shaped charge
that blasts in two opposite directions with a nuke. With
chemical explosives, it's easy--just shape the explosive
like a disc. Geometry does the rest. But an efficient
fission-fusion-fission nuke isn't shaped anything like a
disc. It's more of an elongated shape. It'd be easier to
make an elongated shaped charge where most of the
products expand outward in a ring.
With an elongated shaped charge and products expanding
outward in a ring, the ideal pusher plate design would be
a huge ring with a roughly 45 degree "angle of attack".
We're talking about some serious tension hoop stresses,
of course--the "outward" forces being equal to the "forward"
forces. But if you scale up the spacecraft enough, even this
pusher plate would be a familiar looking rocket nozzle
cone on the end.
Isaac Kuo
Rhysy
> individually, and to attritube quotations.
OK, thanks !
> > "What, and you're just going to pander to the lowest common
> > denominator?"
> > Oh my yes ! And sound effects too (realism zealots can always press the
> > mute button, after all).
> Sound is something which typically isn't depicted in
> a "realistic" manner regardless of genre.
I wasn't sure if it would be worth having delayed sound or no, I think
I'll just try it and see what works best.
> That's completely wrong. When a small object hits a wall with
> greater areal density than it, the result is essentially a spherical
> explosion centered just inside the wall's outer surface.
Makes sense. What happens if the wall has some natural line of weakness
like a fracture ? If the point of KE weapons is to smash through, will
that not prevent the explosion from continuing outwards ? Also,
presumably the explosion cannot be completely spherical or momentum
would not be conserved. I would expect much of it to be in a tightly
focused beam where it would cause havoc internally but only within a
limited range, rather than spreading to the entire ship (as per Ken
Burnside's quote on nyrath's site).
> You only need two turrets to have no blind spots. Even one will
> suffice if you can roll the entire ship quickly enough.
Again depends on the shape of the ship. If you can spare the mass, you
may as well ensure all weapons systems can fire from any angle without
moving the whole ship (which costs propellant).
> The sheer number of guns and gauss cannons you've littered
> the ships with will take up a significant proportion of the mass.
> You may not understand just how heavy large calibre guns
> and their supporting systems are compared to missile tubes.
The Gustav gun, apparently the largest gun ever, massed just 1300
tonnes. Even this is not significant when the mass of the ship is up to
1,000,000 tonnes, and the guns here are nowhere near as large.
Wikipedia lists the mass of a French 100mm gun at just 22 tonnes.
Granted, the Gauss cannons probably would have a significant mass, but
the small guns won't.
> You're considering a massive military vehicle with thick
> hull plating behind the pusher plate. A few holes here
> and there--even pretty big ones--means a reduction in
> capability but the sturdy ship behind the plate will survive.
Maybe. The pusher was chosen to be circular to avoid shock waves from
the impact of the explosion from ripping it apart. Start punching holes
in it and the consequences may be unpleasant.
> I mean that the pneumatic pistons can be placed within
> the hull of the ship. These are attached to metal rods
> which extend through the surface of the hull to the outside.
> Those rods extend outside the ship all the way to the
> pusher plate.
OK, but I don't see this making the drive mechanism any stronger.
Damage a rod and the mechanism is still inoperable, though you may be
able to repair it en-route.
> You can read it any way you want. You'll be wrong, but
> feel free to do so anyway.
You can choose to ignore the question if you like. It won't achieve
anything, but feel free...
> If you want to produce an unrealistic space battle, then
> anything you feel like is okay. It doesn't matter. Make
> space fighters fly around like WWII fighters if you want,
> shooting visible unguided blaster beams at each other
> and blowing up Death Stars with proton torpedoes.
> Knock yourself out.
Hmm, this gives the impression it's either total realism or none. To my
mind there is a whole spectrum of possibilities, from the lowest of the
low (Battlefield Earth) to near-perfection (top of my head, Apollo 13
?). Respectfully, I think trying to aim for total realism is as
pointless as a complete fantasy - you'd need to design the complete
workings of the spaceships, compute their exact orbits, invent detailed
yet intrinsically unreliable future histories (politics may sometimes
overrule even the most scientifically logical decisions), compute the
exact effects from every weapon, work out what course of action the
crew is likely to take based on their training, experience and orders,
etc. etc. In my humble opinion, total realism is a laudable goal but
completely inachievable. Far more worthwhile to spend less time
thinking and more time doing. If making artistic concessions like
visible laser beams gets a wider audience whilst bringing across the
essential point - laser weapons are rather nifty things - then so be
it.
I will post a revised battle plan soon.
IsaacKuo
Rhysy wrote:
>>Sound is something which typically isn't depicted in
>>a "realistic" manner regardless of genre.
>I wasn't sure if it would be worth having delayed sound or no, I think
>I'll just try it and see what works best.
I'm going to give you the benefit of the doubt and
assume that by "delayed sound", you mean that a
camera floating in space would "hear" a nearby
explosion when gases from it physically hit it.
Whether there's delayed sound due to this effect,
or a delayed sound in a more traditional setting
on Earth, it points out to the viewer that there's
an actual camera here. The camera is no longer
simply a device to record the scene, it becomes
part of the scene itself. This can be a purposeful
effect, for that "gritty realistic look" often
associated with "shakey-cam".
However, for depicting a space battle, I think it's
usually an undesirable effect. It begs the question,
why is there this camera floating in the middle of
nowhere?
>>That's completely wrong. When a small object hits a wall with
>>greater areal density than it, the result is essentially a spherical
>>explosion centered just inside the wall's outer surface.
>Makes sense. What happens if the wall has some natural line of weakness
>like a fracture ? If the point of KE weapons is to smash through, will
>that not prevent the explosion from continuing outwards ?
No, it has no effect. The explosion is not a pressure wave
that requires some medium to travel through. The explosion
is a collection of bits of stuff which are traveling outward
from the center.
>Also,
>presumably the explosion cannot be completely spherical or momentum
>would not be conserved.
This is where the relative mass of the incoming projectile
versus the stuff it hits comes into play. If the projectile
is very light in comparison to the stuff it hits, then
the explosion is essentially spherical.
The thing is, the definition of "stuff it hits" changes
from moment to moment. At first, the projectile just
hits a tiny bit of the outer hull. Assuming the projectile
is relatively massive compared to the thin outer hull,
thin this will mostly "punch through", and the resulting
fragments will be spreading in a narrow cone. However,
as this cone of fragments collides with the next layer of
stuff, it's hitting more and more stuff over a wider and
wider area. The proportion of mass between the original
projectile and the stuff it has hit becomes smaller and
smaller as it goes along. This makes the cone of destruction
wider and wider, in a blooming trumpet shape.
Unless the missile is very massive compared to the
ship, this blooming trumpet will stop somewhere within
the hull, having expanded to the point that the fragments
are spreading outward more or less equally in all directions.
At this point, the remaining destruction can be seen as
a roughly spherical explosion of fragments expanding
outward.
>I would expect much of it to be in a tightly
>focused beam where it would cause havoc internally but only within a
>limited range, rather than spreading to the entire ship (as per Ken
>Burnside's quote on nyrath's site).
This depends on the impact energy involved.
Usually, armor is designed to try and enhance the
"trumpet" effect rather than reduce it. This spreads
the impact over a larger area of armor plate, while
reducing total thickness of plate penetrated. The
attacker might try to counter this effect by designing
a terminal warhead that spreads out fragments in a
long line. Thus, successive impactors drill through
a narrow path of destruction with repeated spherical
blasts.
However, if the impactor has so much kinetic energy
that the impact explosion seriously threatens the
entire ship, then there's no need for that. The target
is doomed.
>>You only need two turrets to have no blind spots. Even one will
>>suffice if you can roll the entire ship quickly enough.
>Again depends on the shape of the ship. If you can spare the mass, you
>may as well ensure all weapons systems can fire from any angle without
>moving the whole ship (which costs propellant).
As I noted, you only need two turrets for total
coverage.
Rolling a ship doesn't necessarily cost propellant. You
can use a flywheel or some other rotating component to
accomplish this. Whether this is worth the bother
depends on the overall design of the ship.
>>The sheer number of guns and gauss cannons you've littered
>>the ships with will take up a significant proportion of the mass.
>>You may not understand just how heavy large calibre guns
>>and their supporting systems are compared to missile tubes.
>The Gustav gun, apparently the largest gun ever, massed just 1300
>tonnes. Even this is not significant when the mass of the ship is up to
>1,000,000 tonnes, and the guns here are nowhere near as large.
>Wikipedia lists the mass of a French 100mm gun at just 22 tonnes.
>Granted, the Gauss cannons probably would have a significant mass, but
>the small guns won't.
A million tonnes! Wow, I didn't realize how massive you
were intending these behemoths. Okay, the 100mm guns aren't
so big for that sort of beast. Still, I don't see a
reason to have more than two of them. The French turret
you reference has an absurdly low rate of fire for any
sort of point defense on your battleships. You'd do
better with two heavier guns capable of a high rate
of fire than a bunch of single shot turrets (a single
shot is all they'd be able to get in before the
missiles/fragments impact).
For last ditch point defense, I tend to favor a larger
caliber "gun" with a stack of nukes. These nukes can
be launched one after another at an incredibly high
rate, to provide a practically continuous "kill zone"
that vaporizes incoming missiles/fragments. Think of
what happens in Missile Command when you only have one
city left to defend--except a thousand times faster.
The stack of projectiles makes the "barrels" longer and
heavier, and the incredible recoil increases the turret
mass a lot, compared to a traditional "slow firing" gun.
A 100mm form factor is a bit of a tight squeeze for
nukes, and you want medium sized nukes for your last
ditch defense anyway. More to the point, you want
efficient medium sized nukes for your Orion drive,
and it makes sense to use those for your last ditch
defense.
>>You're considering a massive military vehicle with thick
>>hull plating behind the pusher plate. A few holes here
>>and there--even pretty big ones--means a reduction in
>>capability but the sturdy ship behind the plate will survive.
>Maybe. The pusher was chosen to be circular to avoid shock waves from
>the impact of the explosion from ripping it apart. Start punching holes
>in it and the consequences may be unpleasant.
Relatively small holes won't result in any ripping.
Bigger holes could excessively unbalance the thrust,
which might cause problems with the suspension
system.
>>I mean that the pneumatic pistons can be placed within
>>the hull of the ship. These are attached to metal rods
>>which extend through the surface of the hull to the outside.
>>Those rods extend outside the ship all the way to the
>>pusher plate.
>OK, but I don't see this making the drive mechanism any stronger.
>Damage a rod and the mechanism is still inoperable, though you may be
>able to repair it en-route.
A pneumatic piston is useless after any sort of leak.
A hollow tube rod with some holes in it is merely a
bit weaker.
>>If you want to produce an unrealistic space battle, then
>>anything you feel like is okay. It doesn't matter. Make
>>space fighters fly around like WWII fighters if you want,
>>shooting visible unguided blaster beams at each other
>>and blowing up Death Stars with proton torpedoes.
>>Knock yourself out.
>Hmm, this gives the impression it's either total realism or none. To my
>mind there is a whole spectrum of possibilities, from the lowest of the
>low (Battlefield Earth) to near-perfection (top of my head, Apollo 13
>?). Respectfully, I think trying to aim for total realism is as
>pointless as a complete fantasy - you'd need to design the complete
>workings of the spaceships, compute their exact orbits, invent detailed
>yet intrinsically unreliable future histories (politics may sometimes
>overrule even the most scientifically logical decisions), compute the
>exact effects from every weapon, work out what course of action the
>crew is likely to take based on their training, experience and orders,
>etc. etc.
Hmm...have you ever seen a cartoon where someone is trying
to explain why a completely faithful movie version of
The Lord of the Rings is impossible? And in the final
frame, the nerdy Tolkien fanboy is drooling?
That's me right now. ;)
Seriously, I've been obsessing off and on for decades about
how to realistically depict space combat. I long ago came
to the conclusion that you DID have to design the complete
workings of spaceships, their orbital motions, and
political motivations. You also needed to take into account
the inevitable flawed theories and tactics, as well as the
reactions to wartime experience. Almost all military
hardware and tactics ever used were designed to win "the
last war" and proved less than entirely suited for what
they actually got used for.
Space combat does not take place in a vacuum!
Isaac Kuo
IsaacKuo
IsaacKuo wrote:
> Jarrod wrote:
> > My understanding of the variables that contribute to Orion effective
> > specific impulse is incomplete and slated for improvement. However I
> > think it can be said conclusively that increasing the plate diameter is
> > the number one way to improve rocket performance. The ability to focus
> > the blast onto the pusher plate is finite and never enough to justify a
> > plate diameter smaller than the hull diameter.
[...stuff about Medusa, mag-orion, and shaped charge nukes snipped...]
I just had a bizarre epiphany, that deserves splitting off into a new
thread. Basically, I've realized that you might actually want a large
vehicle in order to DECREASE specific impulse, rather than increase it.
Essentially at issue is that energy costs for many interplanetary
trips is minimized with low Isp, but mag-orion is only efficient at
high
Isp due to the requirement for blast products to be ionized.
This takes a lot of my thoughts about space combat and turns them
on it head...
After I've sorted out these thoughts in an article, I post it in a new
thread.
Isaac Kuo
Mark L. Fergerson
> Rhysy wrote:
>>>Sound is something which typically isn't depicted in
>>>a "realistic" manner regardless of genre.
>>I wasn't sure if it would be worth having delayed sound or no, I think
>>I'll just try it and see what works best.
> I'm going to give you the benefit of the doubt and
> assume that by "delayed sound", you mean that a
> camera floating in space would "hear" a nearby
> explosion when gases from it physically hit it.
BG does this, off and on; fighters get bumped sideways by expanding
clouds from recent explosions with audible thumps.
> Whether there's delayed sound due to this effect,
> or a delayed sound in a more traditional setting
> on Earth, it points out to the viewer that there's
> an actual camera here. The camera is no longer
> simply a device to record the scene, it becomes
> part of the scene itself. This can be a purposeful
> effect, for that "gritty realistic look" often
> associated with "shakey-cam".
BG used to do exactly this, with sloppy zoom and everything,
apparently simulating a nervous camera operator.
> However, for depicting a space battle, I think it's
> usually an undesirable effect. It begs the question,
> why is there this camera floating in the middle of
> nowhere?
BG now apparently does this only from one ship or another's POV, no
more isolated "shakey-cam".
>>>That's completely wrong. When a small object hits a wall with
>>>greater areal density than it, the result is essentially a spherical
>>>explosion centered just inside the wall's outer surface.
>>Makes sense. What happens if the wall has some natural line of weakness
>>like a fracture ? If the point of KE weapons is to smash through, will
>>that not prevent the explosion from continuing outwards ?
> No, it has no effect. The explosion is not a pressure wave
> that requires some medium to travel through. The explosion
> is a collection of bits of stuff which are traveling outward
> from the center.
AIUI for armor plate suffering an impact at fairly high velocity it
doesn't matter if there are cracks/seams or not; they're more or less
welded solid by the shockwave propagating through the armor, and it
shatters as a unit.
>>>You're considering a massive military vehicle with thick
>>>hull plating behind the pusher plate. A few holes here
>>>and there--even pretty big ones--means a reduction in
>>>capability but the sturdy ship behind the plate will survive.
>>Maybe. The pusher was chosen to be circular to avoid shock waves from
>>the impact of the explosion from ripping it apart. Start punching holes
>>in it and the consequences may be unpleasant.
> Relatively small holes won't result in any ripping.
> Bigger holes could excessively unbalance the thrust,
> which might cause problems with the suspension
> system.
Um, you guys do recognize that holes mean hot plasma blowing through
them, not to mention the raditaion hazard?
>>>If you want to produce an unrealistic space battle, then
>>>anything you feel like is okay. It doesn't matter. Make
>>>space fighters fly around like WWII fighters if you want,
>>>shooting visible unguided blaster beams at each other
>>>and blowing up Death Stars with proton torpedoes.
>>>Knock yourself out.
>>Hmm, this gives the impression it's either total realism or none. To my
>>mind there is a whole spectrum of possibilities, from the lowest of the
>>low (Battlefield Earth) to near-perfection (top of my head, Apollo 13
>>?). Respectfully, I think trying to aim for total realism is as
>>pointless as a complete fantasy - you'd need to design the complete
>>workings of the spaceships, compute their exact orbits, invent detailed
>>yet intrinsically unreliable future histories (politics may sometimes
>>overrule even the most scientifically logical decisions), compute the
>>exact effects from every weapon, work out what course of action the
>>crew is likely to take based on their training, experience and orders,
>>etc. etc.
AHEM(new battlestar galactica)AHEM!
> Hmm...have you ever seen a cartoon where someone is trying
> to explain why a completely faithful movie version of
> The Lord of the Rings is impossible? And in the final
> frame, the nerdy Tolkien fanboy is drooling?
>
> That's me right now. ;)
>
> Seriously, I've been obsessing off and on for decades about
> how to realistically depict space combat. I long ago came
> to the conclusion that you DID have to design the complete
> workings of spaceships, their orbital motions, and
> political motivations. You also needed to take into account
> the inevitable flawed theories and tactics, as well as the
> reactions to wartime experience. Almost all military
> hardware and tactics ever used were designed to win "the
> last war" and proved less than entirely suited for what
> they actually got used for.
Does nobody but me ever watch the new BG??? They do this kind of
thing (both sides realize they're not really equipped for what the
enemy's throwing at them, adapt what they have and invent new tactics,
etc.) nearly every episode.
> Space combat does not take place in a vacuum!
That line's a keeper!
Mark L. Fergerson
Logan Kearsley
news:50vFg.7344$Mz3.2422@fed1read07...
>
> > Seriously, I've been obsessing off and on for decades about
> > how to realistically depict space combat. I long ago came
> > to the conclusion that you DID have to design the complete
> > workings of spaceships, their orbital motions, and
> > political motivations. You also needed to take into account
> > the inevitable flawed theories and tactics, as well as the
> > reactions to wartime experience. Almost all military
> > hardware and tactics ever used were designed to win "the
> > last war" and proved less than entirely suited for what
> > they actually got used for.
>
> Does nobody but me ever watch the new BG??? They do this kind of
> thing (both sides realize they're not really equipped for what the
> enemy's throwing at them, adapt what they have and invent new tactics,
> etc.) nearly every episode.
The only problem is that the ships themselves often don't seem very
realistic; but I agree, taking the ship designs as a given, BG is the most
realistic portrayal of space I've ever seen.
-l.
------------------------------------
My inbox is a sacred shrine, none shall enter that are not worthy.
Wayne Throop
::: win "the last war" and proved less than entirely suited for what
::: they actually got used for.
:: Does nobody but me ever watch the new BG??? They do this kind of
:: thing (both sides realize they're not really equipped for what the
:: enemy's throwing at them, adapt what they have and invent new
:: tactics, etc.) nearly every episode.
: "Logan Kearsley" <chrono...@verizon.net>
: The only problem is that the ships themselves often don't seem very
: realistic; but I agree, taking the ship designs as a given, BG is the most
: realistic portrayal of space I've ever seen.
The "plan only survives until contact with the enemy" thing doesn't
seem a "portrayal of space" issue at all. What is it about *space*
that they portray realistically? Most of the episodes I've skimmed
had people walking around in 1-g corridors most of the time, and
small craft designed in the usual "fighters with airfoils" style.
So... can be you be a bit more specific, and state, oh, five
specific things they did a good job of, that are space-related?
Perhaps suggest specific episodes?
( This is not to say I didn't find it a vast, VAST improvement
over the older Cattlecar Galactica series... just that most of
the improvements didn't seem space-related to me. )
Wayne Throop thr...@sheol.org http://sheol.org/throopw
Logan Kearsley
news:11559...@sheol.org...
> ::: Almost all military hardware and tactics ever used were designed to
> ::: win "the last war" and proved less than entirely suited for what
> ::: they actually got used for.
>
> :: Does nobody but me ever watch the new BG??? They do this kind of
> :: thing (both sides realize they're not really equipped for what the
> :: enemy's throwing at them, adapt what they have and invent new
> :: tactics, etc.) nearly every episode.
>
> : "Logan Kearsley" <chrono...@verizon.net>
> : The only problem is that the ships themselves often don't seem very
> : realistic; but I agree, taking the ship designs as a given, BG is the
most
> : realistic portrayal of space I've ever seen.
>
> The "plan only survives until contact with the enemy" thing doesn't
> seem a "portrayal of space" issue at all. What is it about *space*
> that they portray realistically? Most of the episodes I've skimmed
> had people walking around in 1-g corridors most of the time, and
> small craft designed in the usual "fighters with airfoils" style.
I should have been more specific- it provides an unusually realistic
portrayal of space combat, not necessarily sace in general. The whole
plan-enemy thing is a big part of it.
As far as ship designs, I'm not too hard on the Vipers, since they are
supposed to be able to fly in an atmosphere, but the cylon fighters
definitely look like they were designed for aesthetics alone. And of course
one can debate for some time about the actual merits of small fighter
engagements and enormous carrier battleships. Hence my qualifier, "taking
the ship designs as a given...."
> So... can be you be a bit more specific, and state, oh, five
> specific things they did a good job of, that are space-related?
> Perhaps suggest specific episodes?
The most obvious things are that they have inertia and Vipers maneuver like
rockets, not like planes. That and not having visible laser beams in space
alone makes it far ahead of just about everything else I've seen. Apart from
the fact that they seem to lack anything near large enough fuel tanks, the
Vipers also at least appear to me to be far more utilitarian than most SFnal
fighters- not that I've done any significant analysis here, I'm just saying
things look to me far more realistic than any other SF show has ever
managed.
IsaacKuo
Mark L. Fergerson wrote:
> IsaacKuo wrote:
> > Whether there's delayed sound due to this effect,
> > or a delayed sound in a more traditional setting
> > on Earth, it points out to the viewer that there's
> > an actual camera here. The camera is no longer
> > simply a device to record the scene, it becomes
> > part of the scene itself. This can be a purposeful
> > effect, for that "gritty realistic look" often
> > associated with "shakey-cam".
> BG used to do exactly this, with sloppy zoom and everything,
> apparently simulating a nervous camera operator.
(Moore's) Battlestar Galactica was particularly
overenthusiastic with shakey-cam in the pilot
miniseries. He toned it down, but it's still one of
those things which I imagine future viewers will
see as a dated fad.
> >>>You're considering a massive military vehicle with thick
> >>>hull plating behind the pusher plate. A few holes here
> >>>and there--even pretty big ones--means a reduction in
> >>>capability but the sturdy ship behind the plate will survive.
[...]
> > Relatively small holes won't result in any ripping.
> > Bigger holes could excessively unbalance the thrust,
> > which might cause problems with the suspension
> > system.
> Um, you guys do recognize that holes mean hot plasma blowing through
> them, not to mention the raditaion hazard?
The military ship designs in question have rather thick hull
plating all around--thick enough for radiation protection and
thick enough for the hot plasma. I'm actually skeptical that
the pusher plates are necessary at all.
> Does nobody but me ever watch the new BG??? They do this kind of
> thing (both sides realize they're not really equipped for what the
> enemy's throwing at them, adapt what they have and invent new tactics,
> etc.) nearly every episode.
I really like (Moore's) BSG. They at least have a half
decent excuse for fighting at point blank knife-fight ranges.
It's good old jump drive--what's the point in firing long
range missiles at an enemy when he's just going to jump
away to escape? Well...long range lasers would still work,
but we're talking about practically alien civilizations--maybe
they simply never developed high power laser technology
like we have.
However, BSG features cheap FTL and artificial gravity...two
things which MIGHT be possible in reality, but it'd be awfully
convenient.
Isaac Kuo
IsaacKuo
Logan Kearsley wrote:
> As far as ship designs, I'm not too hard on the Vipers, since they are
> supposed to be able to fly in an atmosphere, but the cylon fighters
> definitely look like they were designed for aesthetics alone.
Cylon fighters can fly in an atmosphere also. In the second season,
formations of cylon raiders are shown flying in a breathable
atmosphere.
Isaac Kuo
Jens Egon Nyborg
> I can see a tactical display showing _probable_ beam trajectories
> after the fact- "This ship's mirror is radiating lots of heat, and that
> ship's showing a glowing ablation cloud, so _he_ probably shot _him_."
> but other than that you're out of luck.
Wouldn't the electronics feeding the laser give off a characteristic
signal in operation? If they were in faraday cage the laser would be
shielded too, right?
Rhysy
> assume that by "delayed sound", you mean that a
> camera floating in space would "hear" a nearby
> explosion when gases from it physically hit it.
I was thinking there would be no chance any real sound could be
recorded, but that maybe if for some strange reason you COULD hear in
space, the speed of sound would still be much lower than light. Might
help add believability - anyone who's watched a distant fireworks
display will know the effects of relatively slow sound speed - on the
other hand it might only serve to make people question things further
than usual. If there's typical movie-style instant sounds, people may
think, "Ah, he's gone the same way as everyone else and added
entertaining sound effects." If I add delayed sounds, people may think,
"What's the point in that ? There isn't any sound in space, so if you
must have it, why give it a delay ?" So I don't know... trial and error
seems like the best approach. It may turn out it just looks irritating
to have apparently out-of-synch sounds.
> However, for depicting a space battle, I think it's
> usually an undesirable effect. It begs the question,
> why is there this camera floating in the middle of
> nowhere?
Ah, this is hardcore realism. :) I think having a camera apparently
feeling the effects of the explosions serves to give the viewer a sense
of "being there", as if they were present in some vessel which happened
to be at the camera's viewpoint. The fact that views from other
directions may indicate there is no camera at that position doesn't
really detract from this, I think. The viewer understands that all
cameras, in any movie, are there not because they actually might be,
but ony because they would need to be to create the movie.
> The thing is, the definition of "stuff it hits" changes
> from moment to moment. At first, the projectile just
> hits a tiny bit of the outer hull. Assuming the projectile
> is relatively massive compared to the thin outer hull,
> thin this will mostly "punch through", and the resulting
> fragments will be spreading in a narrow cone. However,
> as this cone of fragments collides with the next layer of
> stuff, it's hitting more and more stuff over a wider and
> wider area. The proportion of mass between the original
> projectile and the stuff it has hit becomes smaller and
> smaller as it goes along. This makes the cone of destruction
> wider and wider, in a blooming trumpet shape.
That's a great explanation - thank you very much.
> Usually, armor is designed to try and enhance the
> "trumpet" effect rather than reduce it. This spreads
> the impact over a larger area of armor plate, while
> reducing total thickness of plate penetrated.
Is there any way in which to confine the explosion, rather than
disperse it ? It seems preferable, if possible, to confine the
explosion to as small a cone as possible so that the threat to the ship
as whole would be reduced (but with total destruction within that
cone). Perhaps some kind of reactive armour that vapourizes the
impactor fragments or some other armour design ? How about making it as
a series of brittle, widely-seperated layers ?
> Rolling a ship doesn't necessarily cost propellant. You
> can use a flywheel or some other rotating component to
> accomplish this. Whether this is worth the bother
> depends on the overall design of the ship.
That was in the back of my wind when deciding the Allies might have
spherical ships. A while back on nuclearspace.com forums someone had
the interesting idea of a perfectly spherical Orion with pusher
mechanism mounted so that it could swivel independently, saving
propellant needed to turn the ship for changing its direction with
pulse units. I ended up not using that idea, it would be difficult to
use for a warship anyway. I think it would probably be simpler just to
use rockets. The Soviet crew is no doubt already complaining at their
cramped conditions, what with all the missile storage and whatnot. They
won't be too happy about an enormous flywheel taking up yet more
precious space.
> A million tonnes! Wow, I didn't realize how massive you
> were intending these behemoths.
I figured that with all the powerful weapons available any space combat
vessel would need LOTS of armour. Given the 70-odd years of Orion-drive
exploration of the solar system in the scenario, most of the raw
materials could be mined from asteroids - no need for massive ground
launches from Earth. Whether or not you really could operate such vast
brutes is another matter - a million tonnes borders on the "Super
Orions", which I view as more speculative. Still, several hundred
thousand tonnes seems at least possible. I completely accept that the
rather small pusher plates may be a bit of a bungle - I'll have to put
that down to unknown advances in nuclear weapons technology.
As a quick check, approximating the Soviet ship as an 80m diameter,
300m length cylinder, 1m of solid steel armour would mass about 580,000
tonnes. Approximating the Allies as a 200m diameter sphere, 1m of steel
masses about 967,000 tonnes (could be reduced by putting more armour
around the habitat rings and less on the spherical sections). Although
just what 1m of steel (or whatever material works best) armour, solid
or otherwise, can handle I have to admit is a mystery to me. But if it
can't deal with 10g ball bearings I'll be awfully disappointed ! Any
chance at all it could handle larger hypervelocity projectiles ?
> The French turret
> you reference has an absurdly low rate of fire for any
> sort of point defense on your battleships. You'd do
> better with two heavier guns capable of a high rate
> of fire than a bunch of single shot turrets (a single
> shot is all they'd be able to get in before the
> missiles/fragments impact).
>From most angles about 6 guns are visible so at the listed rate of
fire, you could get 468 rounds/min or about 8 per second total. If
that's not enough, the gun need not be a carbon-copy of the real-life
gun, perhaps some improvements are possible.
I really should have remembered that Metal Storm weapon, though perhaps
the smaller machine guns could be variants of this.
> For last ditch point defense, I tend to favor a larger
> caliber "gun" with a stack of nukes. These nukes can
> be launched one after another at an incredibly high
> rate, to provide a practically continuous "kill zone"
> that vaporizes incoming missiles/fragments. Think of
> what happens in Missile Command when you only have one
> city left to defend--except a thousand times faster.
> The stack of projectiles makes the "barrels" longer and
> heavier, and the incredible recoil increases the turret
> mass a lot, compared to a traditional "slow firing" gun.
I like it. Perhaps the Gauss cannons, with there much larger barrels,
could serve this role as well as the guns. As you say, the guns are a
bit on the small side for nukes (just about possible ?) but the cannons
ought to handle this easily. With 4 of them they could deal with
multiple attacks from different directions simultaneously, fighting to
the bitter end if necessary.
> Relatively small holes won't result in any ripping.
> Bigger holes could excessively unbalance the thrust,
> which might cause problems with the suspension
> system.
Holes would also depressurize the gas bags so you'd get the pusher
slamming in to the intermediate platform and doing very nasty things to
the shock absorbers.
> A pneumatic piston is useless after any sort of leak.
> A hollow tube rod with some holes in it is merely a
> bit weaker.
Ah, now I understand ! Thank you ! (I was confusing the tubes, which I
thought you meant were to be filled with gas, with the pistons
themselves) Yes, you are quite right, that system would be much better
than having external pistons.
> Hmm...have you ever seen a cartoon where someone is trying
> to explain why a completely faithful movie version of
> The Lord of the Rings is impossible? And in the final
> frame, the nerdy Tolkien fanboy is drooling?
>
> That's me right now. ;)
I'm afraid I haven't seen that.
> Seriously, I've been obsessing off and on for decades about
> how to realistically depict space combat. I long ago came
> to the conclusion that you DID have to design the complete
> workings of spaceships, their orbital motions, and
> political motivations. You also needed to take into account
> the inevitable flawed theories and tactics, as well as the
> reactions to wartime experience. Almost all military
> hardware and tactics ever used were designed to win "the
> last war" and proved less than entirely suited for what
> they actually got used for.
>
> Space combat does not take place in a vacuum!
For sure, a well-edited, realistic depiction of a space battle with
everything thought through carefully would make for a hell of a movie,
even without the cliche sound effects or eye-candy permanently visible
lasers. It would be great to see the ship interiors, curved for
artifical gravity, and see the damage from the inside as well as the
outside. To even get reasonable plausibility would be an epic - but
worthwhile - task, just not one I feel remotely equipped to do. Mine
can only ever be a qualitative approximation, with any numerical
details kept as vague as possible.
I am slowly coming round to the consensus view of long-distance battles
(the use of nukes as sort of defensive shield being a dramatic clincher
for me - it's hard to ignore such an audacious concept). I will rethink
my re-thought battle plan and at the very least put much greater
emphasis on the long-range battle.
Wayne Throop
: [.. re, BSG ..] I'm just saying things look to me far more realistic
: than any other SF show has ever managed.
Hm. I must have skimmed over and/or missed any space battle scenes.
All in all, the general plotlines aren't my cup of tea, so I wasn't
motivated to follow it closely.
I know I'm nagging a bit, but ... could you compare/contrast it with
the Babylon 5 "starfury" battles? Especially the early ones before they
went all bank-and-swoopy in the last two seasons. And ignoring any faux
pas like the starfury-hovering-outside-the-observation-deck-with-
exhaust-pointing-in-the-wring-direction scene.
Specifically... do they show flipover at midflight, instead of heading
in nose-first with motors firing (something B5 wasn't all that good at).
And maybe comebody could suggest a specific episode for me to try to catch?
IsaacKuo
Wayne Throop wrote:
> I know I'm nagging a bit, but ... could you compare/contrast it with
> the Babylon 5 "starfury" battles? Especially the early ones before they
> went all bank-and-swoopy in the last two seasons. And ignoring any faux
> pas like the starfury-hovering-outside-the-observation-deck-with-
> exhaust-pointing-in-the-wring-direction scene.
> Specifically... do they show flipover at midflight, instead of heading
> in nose-first with motors firing (something B5 wasn't all that good at).
Moore's BSG is comparatively good about avoiding "airplane-itis";
noticeably better than B5 ever was. I suspect it's because in B5
everything had to be more or less manually animated whereas in
BSG I think a lot of times they just toss out the fighters in a
particle
sim. Most of the time, it looks like the fighters are virtually thrown
out there with random vectors and rotational momentum like a
handful of nails thrown in the air.
There tends to not be a whole lot of complex maneuvering around.
Usually, opposing groups kind of tumble through each other, with
attitude rotations to point the guns in the right direction but not
much animation effort put into major thrust maneuvers. Major
maneuvering is mostly limited to repeated passes with 180 turns
after each pass to go at it again. Whether or not this is "realistic"
is a matter of debate, I suppose. Note that with thrusters fixed
straight rearward and guns fixed straight forward, there aren't
a whole lot of interesting maneuvering options open to the
animators.
> And maybe comebody could suggest a specific episode for me to try to catch?
I think, pretty much any episode with viper combat other than
"Scar", which featured a very stereotypical "airplane-ish" plot
and suffered a bit from "airplane-itis" (not to the extent of B5).
Episode 211, Ressurection Ship pt1, starts off with a lot of
viper combat maneuvering.
Isaac Kuo