Force fields?
Jim Meritt
"Force fields" are used extensively in science fiction. What is the reality of
the situation? I'm wondering specifically about non-material influence of
electromagnetic radiation (lasers,....)
Thanks for any information!
Jim
--
James W. Meritt
The opinions expressed above are my own. The facts simply
are and belong to none.
Nyrath the nearly wise
Thus spoke Jim Meritt (mer...@wangfed.com):
> "Force fields" are used extensively in science fiction. What is the
> reality of
> the situation? I'm wondering specifically about non-material influence of
> electromagnetic radiation (lasers,....)
I'm interested in that as well. However, as far as I know, there
ain't no such animal as an anti-laser force field.
Offhand it would seem that such a field have to contain as much
energy (if not more) as the laser beam it was intended to
neutralize *all along any hypothetical path of said beam*.
That is, if (for instance) the beam had an area of one square
centimeter, the field would require an equal neutralizing
energy over every one square centimeter of surface area
the field has.
I could be wrong, of course.
I have a vague feeling that a field that changed the path
of the beam would take far less energy. A "mirror" field.
Somebody who actually has a background in physics should jump
in at this point. Max? Dr. Landis?
There was some discussion of anti-projectile force fields
here last month or so. Check with DejaNews.
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Tommy the Terrorist
In article <5pja51$b...@elf.wang.com> Jim Meritt, mer...@wangfed.com
writes:
>"Force fields" are used extensively in science fiction. What is the reality of
>the situation? I'm wondering specifically about non-material influence of
>electromagnetic radiation (lasers,....)
There is actually a device in semi-common use in molecular biology that
involves using two laser beams to position a cell within a fluid, in
three dimensions. I'll admit I haven't the faintest clue as to how it
works, except "it must use light pressure ... somehow..."
Anyway, given this rather unimpressive slice of my knowledge, it seems
conceivable in principle that a computer-operated system could isolate
each speck entering or exiting an area, briefly apply such a set of laser
beams, and thereby affect its motion, as if an invisible barrier were
present. I don't think a macroscopically significant force could be
applied without frying a person trying to pass, but such a system could
do some semi-impressive things, like maintaining patterns of differently
colored India ink in a pool of water, or smoke in air (with IR lasers you
wouldn't even see the beams). Hmm... *conceivably* you could even make
the classic "hologram tank" that way, by having differently-colored dust
particles, and the laser either segregates them into tight clumps in an
area, or spreads them out, depending on whether that color is to be shown
there (sort of like a cuttlefish, but in three dimensions). Come to
think of it, I suppose the original data for the laser beam directions
could actually COME from a hologram, though it might be an inefficient
way to do it, since it's not really just projecting according to hologram
intensities, but interpreting them in terms of what to do with a million
little particles. Maybe if you vary the THICKNESS of the beam according
to hologram-coded intensity?
Meanwhile, the laser "force field" would exert *some* amount of light
pressure, I suppose - if the light were carefully selected to be a poorly
absorbed wavelength it might be perceptible in itself - but of course
having your hand fried and boiling water spewing out of charred surface
tissue also exerts some impetus backwards, both physical and
psychological... the effect could be *exquisitely* precise, where a
person encounters a visible barrier (from laser-trapped particles
suspended in the air and lit), and only those precise portions of their
skin which actually touch the barrier are seared by a stronger beam.
Such a thing would not literally be a force field but simply a "line of
death", but it could be publicly referred to as "force field" as a PR
measure. And in a WAY it would be true - it would FORCE you to turn back
...
Dan M.
> > reality of
> > the situation? I'm wondering specifically about non-material influence of
> > electromagnetic radiation (lasers,....)
>
> ain't no such animal as an anti-laser force field.
>
> Offhand it would seem that such a field have to contain as much
> energy (if not more) as the laser beam it was intended to
> neutralize *all along any hypothetical path of said beam*.
> That is, if (for instance) the beam had an area of one square
> centimeter, the field would require an equal neutralizing
> energy over every one square centimeter of surface area
> the field has.
>
> I could be wrong, of course.
>
> I have a vague feeling that a field that changed the path
> of the beam would take far less energy. A "mirror" field.
>
> Somebody who actually has a background in physics should jump
> in at this point. Max? Dr. Landis?
Force fields clearly exist if you take the general meaning of fields
that can exert force. Electromagnetic fields are a good example of
this. The electromagnetic force field causes a motor to turn. The
earth's magnetic field is a force field, it exerts a force on compasses.
The fields in sci-fi movies have wondrous properties that we see no way
to develop. Fields that will exert strong forces on uncharged objects,
but will not damage those objects. The example of laser pressure is
reasonable for moving an individual atom around (maybe even molecules),
but I would not like to have two strong lasers aimed at me. It is clear
that in large groups of atoms and molecules, heat will result, not just
uniform pressure.
So, force fields do exist, and are pretty mundane. The applications in
sci-fi result in the characteristics of the fields coming from a
screenwriter and not from a development team working in a lab.
Dan M.
Gregory Loren Hansen
In article <5pja51$b...@elf.wang.com>, Jim Meritt <mer...@wangfed.com> wrote:
>"Force fields" are used extensively in science fiction. What is the reality of
>the situation? I'm wondering specifically about non-material influence of
>electromagnetic radiation (lasers,....)
>
You seem like you enjoy science fiction and space battles, so I'm going to
go in from that angle.
There is a laser "force field" of a sort -- air! Low-powered lasers are
relatively unaffected and can shine for miles with little loss. (Unless
it's foggy or dusty or something.) When the power goes up, the beam heats
the air which changed the index of refraction, which causes the beam to
diverge and heat a wider path of air. This is called ballooning, if I
recall right. When the power goes way up, the laser ionizes the air which
then becomes very good at absorbing laser light.
If you're on land, a smoke pot will give you pretty good protection
against lasers. If you're in space maybe you can set up some kind of
smoke dispenser. That's about the best laser "force field" I can think
of. But lasers really do make lousy weapons in the first place. A shiny
surface can reflect better than 90% of the laser energy. When the laser
vaporizes armor, that metal vapor itself absorbs laser light and helps to
protect the target. For that reason, lasers in the SDI program that were
intended to shoot at ICBMs were pulsed lasers, to flash a spot and give
some time for the vapor to clear before flashing it again. Ablative armor
is a material that absorbs lots of heat as it vaporizes, and could be very
effective against the short (seconds long) burst from a laser weapon. And
a laser suffers in the first place from having to vaporize armor before it
does any damage, while kinetic weapons have a lot of momentum that can
blast through armor without having to vaporize it, as an 8mm bullet
might blast clean through 3/8" steel plate leaving a jagged exit hole
where the metal was pushed aside, not vaporized. (I use that example
because I've done it, pretty cool.)
For general force-field interest, a magnetic field acts as "active"
shielding against charged particles. For example look at the
magnetosphere of the earth. The solar wind hits the magnetic field,
positive charges curve one way and negative charges curve the other way,
the result is a current sheet that pretty much keeps the solar wind away
except at the poles, which still act as magnetic reflectors because the
field lines are coming together. A look at the northern lights will tell
you it's not 100% efficient, but I've seen it proposed as radiation
protection from solar flares on long space trips.
If you want to go back to science fiction. a magnetic field will do much
to stop charged-particle or plasma weapons for the same reason it stops
the solar wind. Conductive projectiles might be slowed considerably by
magnetic damping, depending on the strength of the field, speed and
momentum of the projectiles. But I've seen proposals of using plastic
pellets for space-borne kinetic weapons because they're lighter and can go
faster, carrying more energy to the target and don't suffer from air
friction. That would be acheived in a rail gun by having the projectile
backed by a "fuse" of conductive material that vaporizes into a plasma
with essentially zero resistance, but I don't know how to make it work in
a coil gun unless you gave it an aluminum sabot or something. And
remember that gunpowder fires just fine in a vacuum; electromagnetic
weapons shouldn't be used unless they offer a clear advantage. I don't
know how useful that would be in light of the momentum argument for
kinetic weapons, I suppose it varies on a case-by-case basis. But plastic
projectiles wouldn't be slowed by magnetic fields.
The preferred method of dealing with projectiles, rather than shooting the
enemy first, is point-defense, aiming to shoot the projectile before you
have to rely on close defenses like force fields or, in the case of guided
weapons, jamming, flares, and chaff. (The U.S. Navy has this kind of
layered defense; if warplanes miss the target, and point defense doesn't
nail the missiles, they rely on the others plus maneuvoring.) For
reference, the Phalanx system can shoot down birds and fragments of
destroyed missiles a mile away, and it did until the resolution was turned
down to stop wasting ammo. In a space battle, the enemy might use
"stealth" projectiles or active jamming to protect the projectiles until
they hit the target (not to mention protecting themselves from your
radar-guided weapons).
Anyway, you could make up anything you want for science fiction, but I've
stayed strictly with what we know about today. I hope that gives you
something to play with.
--
Remember to floss between your toes every time you bathe!
Peter Clair Martin
Jim Meritt wrote:
>
> "Force fields" are used extensively in science fiction. What is the reality of
> the situation? I'm wondering specifically about non-material influence of
> electromagnetic radiation (lasers,....)
>
> Thanks for any information!
>
> --
> James W. Meritt
> The opinions expressed above are my own. The facts simply
> are and belong to none.
How about suspending reflective/ablative particles in a electromagnetic
field. The field simply holds the particles in place and they reflect
the energy attack. Won't help much against physical objects.
pcm
"It is hard to hate what you strive to understand."
David Mitchell
Nyrath the nearly wise <nyr...@clark.net> wrote in article
<5pjrfm$e...@clarknet.clark.net>...
> Thus spoke Jim Meritt (mer...@wangfed.com):
> > "Force fields" are used extensively in science fiction. What is the
> > reality of
> > the situation? I'm wondering specifically about non-material influence
of
> > electromagnetic radiation (lasers,....)
>
> Offhand it would seem that such a field have to contain as much
> energy (if not more) as the laser beam it was intended to
> neutralize *all along any hypothetical path of said beam*.
> That is, if (for instance) the beam had an area of one square
> centimeter, the field would require an equal neutralizing
> energy over every one square centimeter of surface area
> the field has.
>
there are a couple of ways to create a field that would stop projectiles or
lasers. The simplest would be to create a physical barrier. smoke would
be ideal for lasers [weak lasers] since you only have to obscure the laser
in order to block it...
the problem with science fiction force fields is that if you are letting
the visible spectrum in [so you can see out] you must take special
precautions to block a laser beam. Fortunately we know that it is possible
to do so, [eg. one way mirrors, photo gray lenses...]
Basicaly, when we are attacked you need to do one of a couple of things to
reduce injury:
1. block the attack [eg. erect a wall between you that will absorb the
attack...]
2. redirect the attack [eg. mirrors, wormholes, judo...]
3. obscure the target [eg. smoke screens, hide behind bushes, holographic
barrier...]
Here's an idea: From my vague understanding of plasma physics, if you were
to take a "plasma" and place it in an electro-magnetic field it would
create a heat/pressure shield that would stabilize the heat/pressure as
long as the field is maintained... probably would take a lot of power, and
I don't really understand the mechanics behind the ideas too well. As near
as I can tell this is the technology the aliens had in independence day...
A holographic shield could use a camera to capture the image behind you &
project the image in front of you... but this would not stop a bullet.
Any other ideas (eg. wormholes) are moving into pet theories of mine, that
are completely theoretical and probably not worth mentioning now. How
about a psi shield that would persuade someone not to shoot at you in the
first place?
Hope some of this sparks meaningful (non penis related) discussion.
--
David Mitchell
http://www.jersey.net/~mitchell
mitc...@jersey.net
Nyrath the nearly wise
Thus spoke David Mitchell (mitc...@jersey.net):
> there are a couple of ways to create a field that would stop projectiles or
> lasers. The simplest would be to create a physical barrier. smoke would
> be ideal for lasers [weak lasers] since you only have to obscure the laser
> in order to block it...
There was a game by GDW called Space Cruiser (or something like that)
which had the ships encased in strong magnetic fields which held
clouds of metallic dust as an anti-laser defense.
Fred McGalliard
Actually, some nonlinear optical materials might be described as laser
shields. I think there is a group that pass low intensity beams without
much effect, but high intensity beams darken the material rapidly. Sort
of like the sun sensitive sun glasses. Course this is not a free space
shield, but it is still a shield?
Erik Max Francis
Peter Clair Martin wrote:
> How about suspending reflective/ablative particles in a electromagnetic
> field. The field simply holds the particles in place and they reflect
> the energy attack. Won't help much against physical objects.
And why bother expending the energy do this? Why not just put the
reflective/ablative material on the ship itself? And then you're back to
armor, not shields.
--
Erik Max Francis, &tSftDotIotE / email / m...@alcyone.com
Alcyone Systems / web / http://www.alcyone.com/max/
San Jose, California, United States / icbm / 37 20 07 N 121 53 38 W
\
"All the gods are dead / except the god of war."
/ Eldridge Cleaver
Nyrath the nearly wise
Thus spoke Fred McGalliard (frederick.b...@boeing.com):
> Actually, some nonlinear optical materials might be described as laser
> shields.
I vaguely remember reading an ancient Scientific American article
about some nonlinear optical material that would act like
a mirror normal (i.e., at 90 degrees) to the incoming laser beam,
regardless of the angle.
No matter at what angle you shot at the stuff, it would return
the beam right back at you.
Of course, if the frequency of the beam was outside of the
frequency range the material can handle, you're out of luck.
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| Nyrath the nearly wise nyr...@clark.net |
+---_---+---------------------[ SURREAL SAGE SEZ: ]--------------------------+
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Michael D. Painter
Toss a ball into the corner of the room and it will come back parallel to
it's entry path. That works with any three plane surfaces and is the way
many highway reflectors work.
Under the right conditions firing a 45 cal pistol at something shiny about
100 yards away has the same effect......
Luckily, the surfaces were not really that close to right angles.
Nyrath the nearly wise <nyr...@clark.net> wrote in article
<5q2d4m$h...@clarknet.clark.net>...
Jeffrey O'Callaghan
On Wed, 09 Jul 1997 23:43:39 GMT, jeff...@idt.net (Jeffrey
O'Callaghan) wrote:
>Chapter Eight of the Shadows file describes one possible way a "Force
>Field" consisting of magnetism can have a practical use. It is part
>of a serious theory that describes our universe in respect to four
>spacial dimensions plus time. For your convince a copy Chapter Eight
>Dimensional Technology is attached to this post. The entire file can
>be found at http://idt.net/~jeffocal/shadows.htm
My sincere apologizes to any who may have had trouble accessing the
Shadows web site at http://idt.net/~jeffocal/shadows.htm My
provider has been having technical difficulites with his pope email
and web servers. Please try again at a latter date.
Thank you
Jeff
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Tom Potter
Michael D. Painter <mpai...@maxinet.com> wrote in article
<01bc8d5e$3af4df60$5ace77cc@mpainter>...
> Toss a ball into the corner of the room and it will come back parallel to
> it's entry path. That works with any three plane surfaces and is the way
> many highway reflectors work.
>
> Under the right conditions firing a 45 cal pistol at something shiny
about
> 100 yards away has the same effect......
I see that some high school boy in Texas also
verified this experiment when he inadvertently
fired a 22 caliber toward khaki.
The strange thing is, he got back a 30 caliber
at right angles. Maybe there was a space/time warp.
Tom Potter http://pobox.com/~tdp
Jim Meritt
In article <01bc8aeb$ad210020$6a05...@mitchell.jersey.net>,
mitc...@jersey.net says...
>there are a couple of ways to create a field that would stop projectiles or
>lasers. The simplest would be to create a physical barrier. smoke would
>be ideal for lasers [weak lasers] since you only have to obscure the laser
>in order to block it...
Water washdown system on USN ships is suppose to do this (spray water around
the ship (which has access to a LOT of water) to obscure the beam).
Nyrath the nearly wise
Thus spoke Michael D. Painter (mpai...@maxinet.com):
> Toss a ball into the corner of the room and it will come back parallel to
> it's entry path. That works with any three plane surfaces and is the way
> many highway reflectors work.
yes, I remember the laser reflector array left on the moon by
one of the Apollo missions. It was a bunch of angle prisms like
you describe.
The thought of a spaceship coated with angle prisms like a bad
case of diamond acne is amusing, but it might work.
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| /_\ | There is no sin greater than ignorance -- Rudyard Kipling |
| <(*)> | |
Jim Meritt
In article <01bc8d5e$3af4df60$5ace77cc@mpainter>, mpai...@maxinet.com
says...
>Toss a ball into the corner of the room and it will come back parallel to
>it's entry path. That works with any three plane surfaces and is the way
>many highway reflectors work.
Right angle reflectors. A simple 2-D version is available most places
clothes are sold. A fancier array is sitting on the surface of the moon,
delivered by an Apollo team, used for precision range estimates.
Unfortunately, while this is clever it is material and not what I'm looking
for. Oh well...
Fred McGalliard
I saw an application of mercury as a heat sink in a space craft that
would have interesting application as a laser shield. The mercury was
sprayed as a fine sheet, used to dump heat over a wide area, then
recollected and circulated. Because the movement of the shield is not
dependant on the movement of the vehicle, even a very high power laser
could not penetrate. A pulsed laser would produce an explosion in the
mercury (or other fluid), and that would have some effect on the ship,
but would be a lot easier to handle than a direct exposure.
Beth and Richard Treitel
To my surprise and delight, nyr...@clark.net (Nyrath the nearly wise)
wrote:
> The thought of a spaceship coated with angle prisms like a bad
>case of diamond acne is amusing, but it might work.
Only if the enemy obligingly confined their weapon designers to using
wavelengths that your prisms could refract through the correct angle.
- Richard
------
A sufficiently incompetent ScF author is indistinguishable from magic.
see also:
What is (and isn't) ScF? ==> http://www.wco.com/~treitel/sf.html
Leonard Erickson
Fred McGalliard <frederick.b...@boeing.com> writes:
> Actually, some nonlinear optical materials might be described as laser
> shields. I think there is a group that pass low intensity beams without
> much effect, but high intensity beams darken the material rapidly. Sort
> of like the sun sensitive sun glasses. Course this is not a free space
> shield, but it is still a shield?
By turning dark it absorbs the laser energy. Which means that it gets
destroyed by the first pulse.
Weapons grade laser pulses contain *enormous* amounts of energy. The
small amounts absorbed by a reflectve surface are enough to vaporise a
good chunk of it. And it does so *explosively*. Which ruins the
reflectivity as well as transmitting a lot of shock energy to the
supporting structures.
--
Leonard Erickson (aka Shadow)
sha...@krypton.rain.com <--preferred
leo...@qiclab.scn.rain.com <--last resort
Nyrath the nearly wise
Thus spoke Leonard Erickson (sha...@krypton.rain.com):
> Weapons grade laser pulses contain *enormous* amounts of energy. The
> small amounts absorbed by a reflectve surface are enough to vaporise a
> good chunk of it. And it does so *explosively*. Which ruins the
> reflectivity as well as transmitting a lot of shock energy to the
> supporting structures.
More than that, I was under the impression that there is
more or less no such thing as a "mirror" for x-rays and gamma rays.
Gregory Loren Hansen
In article <970716.224553...@krypton.rain.com>,
Leonard Erickson <sha...@krypton.rain.com> wrote:
>Fred McGalliard <frederick.b...@boeing.com> writes:
>
>> Actually, some nonlinear optical materials might be described as laser
>> shields. I think there is a group that pass low intensity beams without
>> much effect, but high intensity beams darken the material rapidly. Sort
>> of like the sun sensitive sun glasses. Course this is not a free space
>> shield, but it is still a shield?
>
>By turning dark it absorbs the laser energy. Which means that it gets
>destroyed by the first pulse.
>
>small amounts absorbed by a reflectve surface are enough to vaporise a
>good chunk of it. And it does so *explosively*. Which ruins the
>reflectivity as well as transmitting a lot of shock energy to the
>supporting structures.
Well, weapons grade laser pulses of science fiction contain enormous
amounts of energy, vaporizes armor explosively, and transmits a lot of
shock energy to supporting structures.
The current state of the art in laser weapons was reached through SDI.
And those lasers weren't expected to cut missiles in half or anything so
dramatic. They were expected to weaken the structure of the missiles
enough that they'd be destroyed on reentry. And critics of SDI have
pointed out that it would be relatively cheap to protect the missiles with
reflective or ablative coatings, although that would slow them down a bit,
or by spinning them so the laser weapons couldn't shine on one spot long
enough to do significant damage. The lasers of SDI were pulsed lasers
because vaporized metal from the target absorbs laser energy, and they
wanted to give the vapor a chance to clear before the next shot. And an
ICBM isn't exactly armored as a warship would be. If you want explosive
vaporization that transmits shocks to the structure, you'll pretty much
have to get it in the first pulse before the vapor gets a chance to leave
the hole you've made. We're talking about some pretty high power here,
higher than the SDI program has been able to reach. I think the move
toward "brilliant pebbles" suggests the SDIO recognized the problems with
laser weapons.
Some numbers and comparisons with other weapons would be in order here.
Like, my rifle can blast clean through 3/8" plate steel leaving about a
one centimeter hole. What is the skin depth of steel, how much energy
would be required to vaporize that much steel, what time frame do we need
for the pulse, what shock would be transmitted, and how does that shock
compare to an 8mm bullet going about 3000 feet per second? Unfortunately
some of the physics escapes me, and the library is closed so I can't get
any data.
But one thing seems certain, and that is lasers shouldn't even be
considered as weapons unless they offer a clear advantage over
conventional weapons. There's no reason I can think of not to mount a
machine gun on a space ship. Firing armor-peircing ammunition, it could
easily go through a half inch of steel. Bigger guns, like .50-cal
or 20mm, can go through much more. They can fire reliably for a long
time, they're not very big, they need very little power while lasers would
need huge amounts of power that must come from somewhere on board the
ship. Bullets don't suffer from beam spreading, reflective coatings, only
minimally from ablative coatings, they're not affected at all by smoke or
metal vapor. If recoil is a problem, resurrect the gyrojet. Use guided
missiles.
Lasers really do compare poorly as anti-ship weapons. By the time the
technology can make them formidable, I suspect there'll be better
altnernatives.
Erik Max Francis
Jeffrey O'Callaghan wrote:
> Chapter Eight of the Shadows file describes one possible way a "Force
> Field" consisting of magnetism can have a practical use.
Well, if you're a crank, perhaps.
me...@cars3.uchicago.edu
In article <5qq8f0$g...@clarknet.clark.net>, nyr...@clark.net (Nyrath the nearly wise) writes:
>Thus spoke Leonard Erickson (sha...@krypton.rain.com):
>> small amounts absorbed by a reflectve surface are enough to vaporise a
>> good chunk of it. And it does so *explosively*. Which ruins the
>> reflectivity as well as transmitting a lot of shock energy to the
>> supporting structures.
>
>more or less no such thing as a "mirror" for x-rays and gamma rays.
>
1) No, laser pulses do not contain enormous amounts of energy. The
biggest lasers which can still be moved around (with difficulty)
deliver something of the order of kilojoule per pulse. With rather
low rep rate, too. Now the energy of a rifle bullet is also of the
order of a kilojoul. So, a standard assult rifle delivers about as
much per pulse as a very big laser, at a way higher rep rate.
2) Currently there are no X-ray lasers beyond demonstration stage and
no gamma lasers whatsoever.
Mati Meron | "When you argue with a fool,
me...@cars.uchicago.edu | chances are he is doing just the same"
Gregory Loren Hansen
In article <EDL2n...@midway.uchicago.edu>, <me...@cars3.uchicago.edu> wrote:
>In article <5qq8f0$g...@clarknet.clark.net>, nyr...@clark.net (Nyrath the nearly wise) writes:
>>Thus spoke Leonard Erickson (sha...@krypton.rain.com):
>>> Weapons grade laser pulses contain *enormous* amounts of energy. The
>>> small amounts absorbed by a reflectve surface are enough to vaporise a
>>> good chunk of it. And it does so *explosively*. Which ruins the
>>> reflectivity as well as transmitting a lot of shock energy to the
>>> supporting structures.
>>
>>More than that, I was under the impression that there is
>>more or less no such thing as a "mirror" for x-rays and gamma rays.
>>
>However, just to put things in perspective:
>
>1) No, laser pulses do not contain enormous amounts of energy. The
>biggest lasers which can still be moved around (with difficulty)
>deliver something of the order of kilojoule per pulse. With rather
>low rep rate, too. Now the energy of a rifle bullet is also of the
>order of a kilojoul. So, a standard assult rifle delivers about as
>much per pulse as a very big laser, at a way higher rep rate.
A bullet has much better penetration, too. It doesn't have to vaporize
material to damage things, it just has to move material out of the way.
An 8mm Mauser cartridge doesn't even have enough energy to vaporize the
lead in the bullet. But it has enough momentum to make lead-and-copper
lined craters in 1/2" plate steel.
Now how about a barely-moveable gun? Like, oh, say 30mm gatling gun?
Tank with 120mm cannon? The penetration of a 120mm "pulse" is measured in
feet of steel.
me...@cars3.uchicago.edu
In article <5qrp5n$p4u$1...@dismay.ucs.indiana.edu>, glha...@copper.ucs.indiana.edu (Gregory Loren Hansen) writes:
>In article <EDL2n...@midway.uchicago.edu>, <me...@cars3.uchicago.edu> wrote:
>>In article <5qq8f0$g...@clarknet.clark.net>, nyr...@clark.net (Nyrath the nearly wise) writes:
>>>Thus spoke Leonard Erickson (sha...@krypton.rain.com):
>>>> Weapons grade laser pulses contain *enormous* amounts of energy. The
>>>> small amounts absorbed by a reflectve surface are enough to vaporise a
>>>> good chunk of it. And it does so *explosively*. Which ruins the
>>>> reflectivity as well as transmitting a lot of shock energy to the
>>>> supporting structures.
>>>
>>>More than that, I was under the impression that there is
>>>more or less no such thing as a "mirror" for x-rays and gamma rays.
>>>
>>However, just to put things in perspective:
>>
>>1) No, laser pulses do not contain enormous amounts of energy. The
>>biggest lasers which can still be moved around (with difficulty)
>>deliver something of the order of kilojoule per pulse. With rather
>>low rep rate, too. Now the energy of a rifle bullet is also of the
>>order of a kilojoul. So, a standard assult rifle delivers about as
>>much per pulse as a very big laser, at a way higher rep rate.
>
>A bullet has much better penetration, too. It doesn't have to vaporize
>material to damage things, it just has to move material out of the way.
>An 8mm Mauser cartridge doesn't even have enough energy to vaporize the
>lead in the bullet. But it has enough momentum to make lead-and-copper
>lined craters in 1/2" plate steel.
>
that anybody can operate.
>Now how about a barely-moveable gun? Like, oh, say 30mm gatling gun?
>Tank with 120mm cannon? The penetration of a 120mm "pulse" is measured in
>feet of steel.
I think that a tungsten or depleted uranium sabot, fired from a 120mm
gun, can penetrate up to 400 mm steel. So much for lasers.
Michael J. Ramsey
On Sat, 19 Jul 1997 20:38:13 GMT, me...@cars3.uchicago.edu wrote:
[snip]
>However, just to put things in perspective:
>
>1) No, laser pulses do not contain enormous amounts of energy. The
>biggest lasers which can still be moved around (with difficulty)
>deliver something of the order of kilojoule per pulse. With rather
>low rep rate, too. Now the energy of a rifle bullet is also of the
>order of a kilojoul. So, a standard assult rifle delivers about as
>much per pulse as a very big laser, at a way higher rep rate.
The U.S Air Force is building the Airborne Laser Weapons system (ABL)
which will be able to shoot down theater ballistic missiles (and
really, anything else stupid enough to get in its way).
"... the flight-weighted ABL module will be similar in
performance and power levels to the multi-hundred-kilowatt-class
prototype, chemical oxygen iodine laser Baseline Demonstration
Laser module, demonstrated by TRW in August 1996. That laser was
invented at Air Force Phillips Laboratory in 1977."
-- From the ABL's home page.
One watt = 1 Joule/second. So a multi-hundred-kilowatt laser is
100*1000 = 100,000 Joules/second times some integer less than 10.
Given that it is a chemical laser, it is all in a single shot.
"For the operational ABL system, several modules will be linked
together in series to achieve ABL's required megawatt-class power
level."
-- From the ABL's home page.
Ouch! You fire one at the ocean and you will get hydrogen and oxygen
in a 2:1 ratio.
[snip]
--Best regards,
--Mike Ramsey
me...@cars3.uchicago.edu
In article <33d18878...@news.bellatlantic.net>, mjra...@bellatlantic.net (Michael J. Ramsey) writes:
>On Sat, 19 Jul 1997 20:38:13 GMT, me...@cars3.uchicago.edu wrote:
>
>[snip]
>>However, just to put things in perspective:
>>
>>1) No, laser pulses do not contain enormous amounts of energy. The
>>biggest lasers which can still be moved around (with difficulty)
>>deliver something of the order of kilojoule per pulse. With rather
>>low rep rate, too. Now the energy of a rifle bullet is also of the
>>order of a kilojoul. So, a standard assult rifle delivers about as
>>much per pulse as a very big laser, at a way higher rep rate.
>
>The U.S Air Force is building the Airborne Laser Weapons system (ABL)
>which will be able to shoot down theater ballistic missiles (and
>really, anything else stupid enough to get in its way).
>
for the military than they do otherwise. There is no laser in
existance that can do much good as a weapon.
>"... the flight-weighted ABL module will be similar in
>performance and power levels to the multi-hundred-kilowatt-class
>prototype, chemical oxygen iodine laser Baseline Demonstration
>Laser module, demonstrated by TRW in August 1996. That laser was
>invented at Air Force Phillips Laboratory in 1977."
> -- From the ABL's home page.
>
>One watt = 1 Joule/second. So a multi-hundred-kilowatt laser is
>100*1000 = 100,000 Joules/second times some integer less than 10.
>Given that it is a chemical laser, it is all in a single shot.
>
No. There are multi Megawatt lasers in existance. These take a
kilojoule or so and emit it within couple hundred nanoseconds. The
energy delivered is still a kilojoule. The high power results from
the pulse being so compressed in time but in terms of damage to the
target, it is mostly the energy that counts.
Tommy the Terrorist
In article <5qr2ot$frt$1...@dismay.ucs.indiana.edu> Gregory Loren Hansen,
glha...@copper.ucs.indiana.edu writes:
>The current state of the art in laser weapons was reached through SDI.
>And those lasers weren't expected to cut missiles in half or anything so
>dramatic. They were expected to weaken the structure of the missiles
>enough that they'd be destroyed on reentry. And critics of SDI have
>pointed out that it would be relatively cheap to protect the missiles with
>reflective or ablative coatings, although that would slow them down a bit,
Don't be ridiculous. The purpose of these lasers has nothing to do with
missiles - it doesn't make any sense. What they are is assassination
weapons, just as predicted in "Real Genius" back in 1985 or so [this is
no coincidence; some people in the know were apparently consulted for the
movie...]. You have someone sitting in an office making a secure
encrypted connection with a spy/reflector satellite, who is the ONLY
PERSON ON EARTH who knows where the beam is directed by the satellite
system. I've made some other posts (you can Dejanews me & look for
"laser") in which I've quoted text from the site that had the laser and
reflectors working in 1991, the AF 2025 report
(http://www.au.af.mil/au/2025/, an Air Force University report apparently
sanctioned by high brass as a reasonable prediction of possible futures
in 2025 A.D.) in which soldiers have implanted microchips that allow them
to access global weapon systems, and persons misusing the security are
eliminated by a "Zap Attack" (lasers target the offending chip from
space), and most interestingly, one report just recently of someone in
1991 who described being hit by some kind of intense light beam from the
sky while driving his car, though his description of what he thought it
was didn't make much sense.
The laser described at http://wmsr.helstf-www.army.mil/ is somewhere in
the near IR, suggesting it could be invisible or nearly so. Used to
start fires, explode fuel tanks in airplanes, crash cars, explode
refineries, and so forth, this is a potent weapon. Used to stop missiles
it's silly - what use is the one beam, even if there's no reflective
shielding and no chaff to worry about?
Gregory Loren Hansen
In article <5qt3l9$k...@snews2.zippo.com>,
Tommy the Terrorist <may...@super.zippo.com> wrote:
>In article <5qr2ot$frt$1...@dismay.ucs.indiana.edu> Gregory Loren Hansen,
>glha...@copper.ucs.indiana.edu writes:
>
>>The current state of the art in laser weapons was reached through SDI.
>>And those lasers weren't expected to cut missiles in half or anything so
>>dramatic. They were expected to weaken the structure of the missiles
>>enough that they'd be destroyed on reentry. And critics of SDI have
>>pointed out that it would be relatively cheap to protect the missiles with
>>reflective or ablative coatings, although that would slow them down a bit,
>
>Don't be ridiculous. The purpose of these lasers has nothing to do with
>missiles - it doesn't make any sense. What they are is assassination
>weapons, just as predicted in "Real Genius" back in 1985 or so [this is
Um... okay. I'm glad you're here to set me straight.
Gregory Loren Hansen
In article <EDL2n...@midway.uchicago.edu>, <me...@cars3.uchicago.edu> wrote:
>In article <5qq8f0$g...@clarknet.clark.net>, nyr...@clark.net (Nyrath the nearly wise) writes:
>>Thus spoke Leonard Erickson (sha...@krypton.rain.com):
>>> Weapons grade laser pulses contain *enormous* amounts of energy. The
>>> small amounts absorbed by a reflectve surface are enough to vaporise a
>>> good chunk of it. And it does so *explosively*. Which ruins the
>>> reflectivity as well as transmitting a lot of shock energy to the
>>> supporting structures.
>>
>>More than that, I was under the impression that there is
>>more or less no such thing as a "mirror" for x-rays and gamma rays.
>>
>
>1) No, laser pulses do not contain enormous amounts of energy. The
>biggest lasers which can still be moved around (with difficulty)
>deliver something of the order of kilojoule per pulse. With rather
>low rep rate, too. Now the energy of a rifle bullet is also of the
>order of a kilojoul. So, a standard assult rifle delivers about as
>much per pulse as a very big laser, at a way higher rep rate.
Okay, I tried getting some numbers. Understand that I reserve the
possibility that my calculations are wrong. I knew lasers would be pretty
bad. But if my calculations are right, they're totally dismal.
THEORY
I was working with visible light, which has a skin depth of about
1e-8 meters in metal, and assuming no reflection. The power transmitted
is P=P0*exp(-x/d) where P0 is the power at the surface and d is the skin
depth, x is the distance inside the medium. P=de/dt, where e is energy
density, and that's the form I used.
e(x) = e0 exp(-x/d) (1)
Assume the pulse time is approximately zero, otherwise performance
will degrade due to conduction, radiation, ablation, and absorption by
ablated material.
The energy required to vaporize a peice of metal is the specific heat of
the solid times the change in temperature to melt it, plus the heat
absorbed to melt it, plus the specific heat of the liquid times the change
in temperature to boiling point, plus the heat required to boil it, plus
the specific heat of the vapor times the change in temperature of the
vapor, all of that times the mass of the material. I just called that big
function "F".
dE = F dm
dm is the density D times the area A times the distance dx. dE is is the
energy density e times the distance dx. Or
F D A dx = e0 A exp(-x/d) dx
F D = e0 exp(-x/d) (2)
where e0 is the energy density at the surface. The energy required is
found by integration,
E = A [integrate] e0 exp(-x/d) dx
For the energy expended I suppose the integral should be taken from zero
to infinity, but I just took it from zero to x_max, where x_max is found
from equation (2) where F is just high enough to vaporize the metal with
no heating of the metal vapor. (You can choose x_max and solve for e0, or
choose e0 and solve for x_max). So it's just the energy of the plug of
metal vapor that is lost. The solution to the integral is
E = A e0 d ( 1 - exp(-x/d) )
If you like, you can plug equation (2) into this one to find a total E
given x_max, or an x_max given a total E. Anyway, having gotten this far
you can go back to equation (1) to find energy density as a function of
distance, then plug into equation (2) to find temperature as a function of
distance. Recognizing the average velocity of an ideal gas is
v = sqrt( 3 k T / m )
where k is Boltzmann's constant, T is the temperature of the gas, and m is
the mass of a molecule, you can solve equation (2) for the final
temperature and find the differential contribution to momentum
dp = v(x) dm
and integrate to find the total momentum transfer of the expanding gas, or
the "shock" that's transmitted to the structure.
RESULTS
So much for theory. If there's a mistake, it's probably in there. Now
for the numbers. To compare with an 8mm Mauser cartridge (which I chose
because I have a rifle that shoots it and I know it can blast through 3/8"
plate steel) I chose a diameter of one centimeter, depth of one
centimeter, in iron. And I spent a long time looking through the accursed
CRC handbook to get the data I needed, and needed to use the
Clausius-Clapyeron equation to get the latent heat of vaporization. For
the benefit of those who want to check my results, I was using
iron:
specific gravity 7.86
melting point 1535C
boiling point 2750C
specific heat (solid) 0.106 cal/g-K
specific heat (liquid) 0.052 cal/g-K
heat of fusion 65 cal/g
heat of vaporization 300 cal/g
Calculated from Clausius-Clapyeron equation
with T=2093K at 1e-3 atm, T=1594K at 1e-6atm,
and assuming change in volume is the volume
of an ideal gas at T=2093K and P=1e-3atm
And my answer for e0 (in calories per cubic centimeter) was proportional
to exp(1000000). My calculator doesn't go that high. The energy turned
out to be (.005 calories)*exp(1000000). I didn't even try to find the
momentum transfer.
Next I tried plugging in a kilojoule of energy and got a penetration of
.000006 centimeters. I didn't bother trying to find momentum transfer,
partly because it was disheartening to see that little material ablated,
and partly because it's a big nasty equation that I could only integrate
numerically, and I've run out of steam.
For anyone who wants to carry it through, solve the thermodynamic function
F for the final temperature, plug that into the velocity equation,
multiply by dm=D*A*dx. You'll get an equation of the form
dp = g*sqrt(h*exp(-x/d) + k)
where g, h, and k represent "stuff". I'd solve it by turning it into the
form
dp = g*sqrt(k)*sqrt(h*k*exp(-x/d) + 1)
then set y=h*k*exp(-x/d) and Taylor-expand, then integrate. If you have a
better way, let me know.
DISCUSSION
The reason for the abysmal performance of the laser is my assumption that
all the damage must be done in one shot. Since the skin depth is so low,
you don't get much penetration without bringing the surface vapor to
obnoxious temperatures, and that costs energy. I was also working with a
centimeter diameter hole. Industrial cutting lasers spend a much longer
time to cut metal, so they don't have to blast a chunk out in a single
pulse. And they also cut a hole with a much smaller diameter. But this
approach wouldn't be suitable as a weapon unless you can count on the
enemy to stay still while you vape away his armor.
An improvement might be the pulsed laser concept that the SDIO was working
on. That is, pulse the target, wait for the metal to clear, then pulse it
again. If the metal vapor clears fast enough and the pulses are close
together, even on a moving target the holes you're cutting might overlap
and you'd get much better penetration. Although you still don't get much
of a shock transmitted to the structure. BUT... that's a much more
complicated analysis, and I just don't have the energy to explore it right
now.
Gregory Loren Hansen
In article <5qu1j7$np2$1...@dismay.ucs.indiana.edu>,
Gregory Loren Hansen <glha...@copper.ucs.indiana.edu> wrote:
>Next I tried plugging in a kilojoule of energy and got a penetration of
>.000006 centimeters. I didn't bother trying to find momentum transfer,
>partly because it was disheartening to see that little material ablated,
>and partly because it's a big nasty equation that I could only integrate
>numerically, and I've run out of steam.
>
>For anyone who wants to carry it through, solve the thermodynamic function
>F for the final temperature, plug that into the velocity equation,
>multiply by dm=D*A*dx. You'll get an equation of the form
>
> dp = g*sqrt(h*exp(-x/d) + k)
>
>where g, h, and k represent "stuff". I'd solve it by turning it into the
>form
>
> dp = g*sqrt(k)*sqrt(h*k*exp(-x/d) + 1)
>
>then set y=h*k*exp(-x/d) and Taylor-expand, then integrate. If you have a
>better way, let me know.
Okay, I worked out the momentum transfer in a very approximate way. Can't
do the Taylor expansion because you get an expression like sqrt(y-1)
rather than sqrt(y+1). But y is much bigger than 1 for most of the valid
range of integration, so it dominates. Drop the 1. For iron I get a
relation like
p = (5.86e-9) sqrt(E)
E in calories, p in kg-m/s. Which means the momentum transfer is
surprisingly small. I worked it out because I thought it would be a
curious state of affairs if the ablative shock from a laser gun did more
damage than the vaporization. But my numbers don't support that thought.
me...@cars3.uchicago.edu
In article <5qubjn$reo$1...@dismay.ucs.indiana.edu>, glha...@copper.ucs.indiana.edu (Gregory Loren Hansen) writes:
>
>Okay, I worked out the momentum transfer in a very approximate way. Can't
>do the Taylor expansion because you get an expression like sqrt(y-1)
>rather than sqrt(y+1). But y is much bigger than 1 for most of the valid
>range of integration, so it dominates. Drop the 1. For iron I get a
>relation like
>
> p = (5.86e-9) sqrt(E)
>
>E in calories, p in kg-m/s. Which means the momentum transfer is
>surprisingly small. I worked it out because I thought it would be a
>curious state of affairs if the ablative shock from a laser gun did more
>damage than the vaporization. But my numbers don't support that thought.
>
either in idealized "most efficient case" but what kills it in reality
is that so little mass gets vaporized. The laser yields and
"overkill", heating up a miniscule quantity of matter to a very high
temperature instead of maximizing the volume being vaporized. And
this cannot be helped.
Gregory Loren Hansen
I've been having second thoughts about my numbers. I haven't found a
mistake (doesn't mean there aren't any, I just haven't found them), they
just seem much smaller than even I expected. By my calculations, a
megajoule pulse will burn a centimeter diameter hole down, oh, what was
it, I think .0002 centimeters. That won't even get through a sheet of
kitchen foil. But if I do a straight energy analysis and vaporize the
metal but don't heat the vapor any further, a megajoule can burn a 30
centimeter deep hole! I expected a difference, but not five orders of
magnitude.
Undoubtedly better performance would be had with a thousand kilojoule
pulses rather than a single megajoule pulse, if there's enough time
between pulses for the metal vapor to clear. But I have no idea what kind
of time frame that is. Maybe ten thousand pulses of a hundred joules each
would more closely approach the foot-deep ideal hole. But this isn't a
machine shop and we can't spend ten minutes to blast away at a single
spot on a target. I'd have to teach myself new physics before I could
look at that problem.
me...@cars3.uchicago.edu
mentioned. There is a hell of a lot of energy but it is being
absorbed within a very thin layer. So it turns it into a hot plasma
but the rest stays intact. There are two factors which may deepen the
hole a bit. One is an energy transfer from the plasma to the metal.
However, the plasma is free to expand (and coool) in one direction and
it'll doo it, very fast. The other, well, at sufficiently high power
density you can fully ionize everything within the layer being hit, at
which point it'll turn pretty transparent, allowing the light
penetrating deeper. I doubt that we get to such density, though.
Brian Trosko
Michael J. Ramsey <mjra...@bellatlantic.net> wrote:
: One watt = 1 Joule/second. So a multi-hundred-kilowatt laser is
: 100*1000 = 100,000 Joules/second times some integer less than 10.
: Given that it is a chemical laser, it is all in a single shot.
You're overlooking the fact that the duration of a single pulse is far
less than one second.
Timeout
Gregory Loren Hansen wrote:
<snipped>
> But one thing seems certain, and that is lasers shouldn't even be
> considered as weapons unless they offer a clear advantage over
> conventional weapons. There's no reason I can think of not to mount a
>
> machine gun on a space ship.
Other than a fuel source. Guns require gun powder and oxygen, which is
lacking in space. (Ammo could be designed to mute this argument, but
the problem remains that you would have potentially explosive materials
on board that only require a spark to ignite) Don't forget that you can
run out of ammo (like photon torpedoes) while you will not run out of
laser.So I quess we can add safety to the list.
> Firing armor-peircing ammunition, it could
> easily go through a half inch of steel. Bigger guns, like .50-cal
> or 20mm, can go through much more.
But if you have a two foot piece of steel, it will not penetrate but
deflect (possibly back at the attacker). A laser on a continuous output
could damage the armour. If stationary, given time the laser (the
smaller the diameter of the beam the better) would completely penetrate
the thick hull while the guns would be out of ammo.How many times would
you have to shoot an elephant with a B B gun to kill it? You probably
would never kill it.
> They can fire reliably for a long
> time, they're not very big, they need very little power while lasers
> would
> need huge amounts of power that must come from somewhere on board the
> ship. Bullets don't suffer from beam spreading, reflective coatings,
> only
> minimally from ablative coatings, they're not affected at all by smoke
> or
> metal vapor.
Don't forget that the speed of the bullets and missles are extremely
slow. Even at 30,000 feet per second, a laser will travel at 186,000
miles per second. Given ships in ST that are traveling at more than
30,000 feet per second then guns would be useless because the bullet
would never reach the target. In fact, the bullet would be an obstical
in the path of the attacking ship.But you still have the problem of
limited ammo that is potentially explosive.
> If recoil is a problem, resurrect the gyrojet. Use guided
> missiles.
And how big would this gyro be for a portable weapon. Large enough to
make it nonportable. So you add more space, more weight, which means
less ammo. As far a using lasers as a weapon on earth, if you hit the
fuel tank (and we know that targeting laser can continuously shoot) then
a jet could be exploded by its own fuel. The laser does not even have
to be visible.
There are advantages and disadvantages to both.
> Lasers really do compare poorly as anti-ship weapons. By the time the
>
> technology can make them formidable, I suspect there'll be better
> altnernatives.
>
Like phasers.
Gregory Loren Hansen
Just to carry on about this a little more, I did the "easy" pulse
analysis. That is, I found the penetration for a single pulse and
multiplied that. For a centimeter diameter hole in iron, a single
megajoule pulse will get you .000017cm. A thousand kilojoule pulses will
get you .011cm, a significant improvement! Ten thousand pulses of a
hundred joules each will get you .085cm, and 50,000 pulses of 20 joules
each will get you .35cm. You can see where these gains are coming from if
you take your energy, divide by n, and multiply the depth by n.
x_max = n d ln(50 E / n)
E in joules, d is skin depth in centimeters. Another way to write that is
x_max = n d ln(50 E) - n d ln(n)
So you're multiplying by n and subtracting the log of n. So x_max
increases as n increases. You'll also note it goes with the log of E,
which mean increasing E a lot won't increase the depth very much. It's
also proportional to the skin depth. A longer wavelength has a longer
skin depth, but it also reflected more strongly. I haven't checked it,
but I'm sure there must be some optimum wavelength for a given target.
(A different wavelength would change the "50", that number represents a
bunch of parameters multiplied together, including d.) The general method
can be used for particle beams, too, if you keep in mind that the "skin
depth" of a particle depends on its energy, and the total energy of the
beam is the energy of a particle times the number of particles. I haven't
looked at that one, either. Or at x-rays or gamma rays, they start acting
quantum so the simple classical skin depth calculation doesn't work.
The other concern is residual heat. If you vaporize some metal, there's
going to be some heat left over to "kick start" the next pulse, right?
Turns out you don't have to worry about than until you get into ten
million pulses (multiply E/n by 1.2). But it's hard to believe that a
useful weapon would get off ten million pulses in less than a second,
allowing enough time for metal vapor to clear between each pulse. Still,
allowing for residual heat, I was able to get about 30cm deep with 18
million pulses. So that does make me feel a little better about the
numbers I'm coming up with. It's consistent with laser cutters in a
machine shop that can take as long as needed to cut out complicated
patterns in sheet metal. (The laser cutter would get deeper than 30cm
with a megajoule, since they're also burning pinprick-sized holes rather
than centimeter diameter holes.)
Anyway, I hope someone finds all of that edifying.
me...@cars3.uchicago.edu
In article <5r13ae$6e9$1...@dismay.ucs.indiana.edu>, glha...@copper.ucs.indiana.edu (Gregory Loren Hansen) writes:
>
>Just to carry on about this a little more, I did the "easy" pulse
>analysis. That is, I found the penetration for a single pulse and
>multiplied that. For a centimeter diameter hole in iron, a single
>megajoule pulse will get you .000017cm. A thousand kilojoule pulses will
>get you .011cm, a significant improvement! Ten thousand pulses of a
>hundred joules each will get you .085cm, and 50,000 pulses of 20 joules
>each will get you .35cm. You can see where these gains are coming from if
>you take your energy, divide by n, and multiply the depth by n.
>
> x_max = n d ln(50 E / n)
>
>E in joules, d is skin depth in centimeters. Another way to write that is
>
> x_max = n d ln(50 E) - n d ln(n)
>
>So you're multiplying by n and subtracting the log of n.
Something is not quite so here, since it would indicate an infinite
depth when you go to a CW limit.
>Or at x-rays or gamma rays, they start acting
>quantum so the simple classical skin depth calculation doesn't work.
Oh, you still have exponential decay of intensity, on penetration.
You Need QM to calculate the absorption coefficient but once you've
done it you can just use it and forget about QM.
>
>The other concern is residual heat. If you vaporize some metal, there's
>going to be some heat left over to "kick start" the next pulse, right?
>Turns out you don't have to worry about than until you get into ten
>million pulses (multiply E/n by 1.2). But it's hard to believe that a
>useful weapon would get off ten million pulses in less than a second,
>allowing enough time for metal vapor to clear between each pulse. Still,
>allowing for residual heat, I was able to get about 30cm deep with 18
>million pulses. So that does make me feel a little better about the
>numbers I'm coming up with. It's consistent with laser cutters in a
>machine shop that can take as long as needed to cut out complicated
>patterns in sheet metal. (The laser cutter would get deeper than 30cm
>with a megajoule, since they're also burning pinprick-sized holes rather
>than centimeter diameter holes.)
>
Something very important that's worth mentioning here. Your machine
shop cutters, or surgical lasers, focus the beam and, since the beam
is coherent, it can be focused to extremely small size. Thus you get
hellish local power densities even though the integrated power may not
be very high.
So, somebody may ask, why not do it with weapons, too. Well, there is
a little problem called "diffraction limit". Assuming everything else
is perfect, the smallest possible size of the focal spot is of the
order of
D_f = distance*wavelength/aperture
where the distance is the distance from the source to target, of
course, and the "aperture" is the source aperture. Now, surgical and
machining lasers operate with distances of between few mm to few cm.
Over such distances you can focus pretty much to a wavelength size.
On the other hand, in anti-missile applications the distances are
measured in hundreds of kilometers and more, while maximal practical
apertures are of teh order of a meter or so. Thus, your focal spot
isn't that small anymore. Now, since the power density is inversely
proportional to the square of the size of the focal spot ...
>Anyway, I hope someone finds all of that edifying.
>
I would hope that it should provide a bit of reality check.
Beth and Richard Treitel
To my surprise and delight, nyr...@clark.net (Nyrath the nearly wise)
wrote:
>More than that, I was under the impression that there is
>more or less no such thing as a "mirror" for x-rays and gamma rays.
I had the feeling that a suitable crystal could reflect X-rays if the
angle of incidence was low enough -- but certainly not at 90 degrees.
Not sure what percentage might get reflected.
me...@cars3.uchicago.edu
In article <33D401F3...@mycomputer.com>, Timeout <isa...@mycomputer.com> writes:
>Gregory Loren Hansen wrote:
>
><snipped>
>
>> But one thing seems certain, and that is lasers shouldn't even be
>> considered as weapons unless they offer a clear advantage over
>> conventional weapons. There's no reason I can think of not to mount a
>>
>> machine gun on a space ship.
>
>Other than a fuel source. Guns require gun powder and oxygen, which is
>lacking in space.
This is wrong. The powder contains its own oxygen, internally, it
doesn't rely on atmospheric oxygen. Thus it can work in spece equally
well.
>(Ammo could be designed to mute this argument, but the problem remains
>that you would have potentially explosive materials on board that only
>require a spark to ignite).
This is a problem that military ships have lived with, for centuries.
A nuisance, but can be dealt with.
>Don't forget that you can run out of ammo (like photon torpedoes) while
>you will not run out of laser.
But of course you can. Laser runs on power, not on magical spells.
And it is not terribly efficient, for each joule delivered to target
you've to put in 10-100 joules. So, in fact, it is just the opposite
of what you said. The rate of fire you can maintain with lasers
is limited by the power available on board, standard ammo isn't.
>> Firing armor-peircing ammunition, it could
>> easily go through a half inch of steel. Bigger guns, like .50-cal
>> or 20mm, can go through much more.
>
>But if you have a two foot piece of steel, it will not penetrate but
>deflect (possibly back at the attacker). A laser on a continuous output
>could damage the armour.
I guess you haven't seen the numbers on this.
>If stationary, given time the laser (the smaller the diameter of the
>beam the better) would completely penetrate the thick hull while the
>guns would be out of ammo.
Thge time you're talking about is in the order of days or months. No
sensibel weapon is designed based on the assumption that your opponent
will stand still as long as needed.
me...@cars3.uchicago.edu
In article <33d7cd4b...@news.wco.com>, tre...@wco.com (Beth and Richard Treitel) writes:
>To my surprise and delight, nyr...@clark.net (Nyrath the nearly wise)
>wrote:
>
>>More than that, I was under the impression that there is
>>more or less no such thing as a "mirror" for x-rays and gamma rays.
>
>I had the feeling that a suitable crystal could reflect X-rays if the
>angle of incidence was low enough -- but certainly not at 90 degrees.
>Not sure what percentage might get reflected.
It could, even at 90 degrees. But only X-rays at specific wavelength.
Such crystals are routinely used as monochromators. They reflect a
specific wavelength, absorbing all the rest.
Beyond this, there are mirrors for X-rays, but they only work at
grazing incidence (small angle). To reflect X-rays with energies up
to, say, 20 keV, the angle of incidence must be below 4 miliradians
(about 0.2 degrees). If you want to double the energy range, the
angle is halved.
Charles Frederick Goodin
In article <33D401F3...@mycomputer.com>,
Timeout <isa...@mycomputer.com> wrote:
>
>Don't forget that the speed of the bullets and missles are extremely
>slow. Even at 30,000 feet per second, a laser will travel at 186,000
>miles per second. Given ships in ST that are traveling at more than
>30,000 feet per second then guns would be useless because the bullet
>would never reach the target. In fact, the bullet would be an obstical
>in the path of the attacking ship.But you still have the problem of
>limited ammo that is potentially explosive.
That's a joke, right? It's not like the speed of a bullet is a constant,
like c. If you fire a bullet (travelling 30 000 fps) out of a ship
(travelling 3 000 000 fps), you now have a bullet travelling 3 030 000
fps, which is faster than the ship. In fact, who needs guns? Just drive
across your oppenents path and drop a bunch of gravel, and when she drives
into it at 3 000 000 fps, she's in big trouble.
chuk
Tenhawk
gravel/bullets would turn a ship into swiss cheese... with the nav
shields the debris becomes a minor entry in the computer log.
Erik Max Francis
Charles Frederick Goodin wrote:
> That's a joke, right? It's not like the speed of a bullet is a
> constant,
> like c. If you fire a bullet (travelling 30 000 fps) out of a ship
> (travelling 3 000 000 fps), you now have a bullet travelling 3 030 000
> fps, which is faster than the ship. In fact, who needs guns? Just
> drive
> across your oppenents path and drop a bunch of gravel, and when she
> drives
> into it at 3 000 000 fps, she's in big trouble.
The problem is in the delivery. To get your ship up to that speed, you
have to 1. accelerate over a good distance, and 2. fire your engines the
whole way. This not only makes you on obvious target, but also means that
delivering the weapon to the target is going to be problematic, because
they'll see you coming a long way away.
Kinetic weapons are still going to be the way to go, but with their own
kinetic energy, not the ship's.
--
Erik Max Francis, &tSftDotIotE / email / m...@alcyone.com
Alcyone Systems / web / http://www.alcyone.com/max/
San Jose, California, United States / icbm / 37 20 07 N 121 53 38 W
\
"Love is not love which alters / when it alternation finds."
/ William Shakespeare, _Sonnets_, 116
Gregory Loren Hansen
In article <33d7cd4b...@news.wco.com>,
Beth and Richard Treitel <tre...@wco.com> wrote:
>To my surprise and delight, nyr...@clark.net (Nyrath the nearly wise)
>wrote:
>
>>More than that, I was under the impression that there is
>>more or less no such thing as a "mirror" for x-rays and gamma rays.
>
>I had the feeling that a suitable crystal could reflect X-rays if the
>angle of incidence was low enough -- but certainly not at 90 degrees.
>Not sure what percentage might get reflected.
Something my physics teacher taught me is that anything can reflect
anything if the angle of incidence is low enough. Then in class (instead
of paying attention) I discovered even the newspaper can reflect if the
angle is shallow enough.
But I don't know of anything that can reflect X-rays at 90 degrees.
Gregory Loren Hansen
In article <EDp7K...@midway.uchicago.edu>, <me...@cars3.uchicago.edu> wrote:
>In article <5r13ae$6e9$1...@dismay.ucs.indiana.edu>, glha...@copper.ucs.indiana.edu (Gregory Loren Hansen) writes:
>>
>>Just to carry on about this a little more, I did the "easy" pulse
>>analysis. That is, I found the penetration for a single pulse and
>>multiplied that. For a centimeter diameter hole in iron, a single
>>megajoule pulse will get you .000017cm. A thousand kilojoule pulses will
>>get you .011cm, a significant improvement! Ten thousand pulses of a
>>hundred joules each will get you .085cm, and 50,000 pulses of 20 joules
>>each will get you .35cm. You can see where these gains are coming from if
>>you take your energy, divide by n, and multiply the depth by n.
>>
>> x_max = n d ln(50 E / n)
>>
>>E in joules, d is skin depth in centimeters. Another way to write that is
>>
>> x_max = n d ln(50 E) - n d ln(n)
>>
>>So you're multiplying by n and subtracting the log of n.
>
>Something is not quite so here, since it would indicate an infinite
>depth when you go to a CW limit.
Take the derivative.
dx/dn = d ln(50E) - d ln(n) - d = 0
n(max) = 50 E exp(-1)
If n is too large, ln(50E/n) = 0 and the pulse evidently isn't strong
enough to vaporize anything.
>Something very important that's worth mentioning here. Your machine
>shop cutters, or surgical lasers, focus the beam and, since the beam
>is coherent, it can be focused to extremely small size. Thus you get
>hellish local power densities even though the integrated power may not
>be very high.
>
>So, somebody may ask, why not do it with weapons, too. Well, there is
>a little problem called "diffraction limit". Assuming everything else
>is perfect, the smallest possible size of the focal spot is of the
>order of
>
> D_f = distance*wavelength/aperture
>
>where the distance is the distance from the source to target, of
>course, and the "aperture" is the source aperture. Now, surgical and
>machining lasers operate with distances of between few mm to few cm.
>Over such distances you can focus pretty much to a wavelength size.
>On the other hand, in anti-missile applications the distances are
>measured in hundreds of kilometers and more, while maximal practical
>apertures are of teh order of a meter or so. Thus, your focal spot
>isn't that small anymore. Now, since the power density is inversely
>proportional to the square of the size of the focal spot ...
Hadn't thought of that, good technical point. My original reason for
using a centimeter diameter hole was to compare it to a weapon I knew.
But also because you'd expect an effective weapon to take a pretty big
chunk out of the target. If I got hit by a megajoule pinprick I'm sure it
would hurt like hell, but then I'd return fire with a slugthrower. (Since
I'm on the subject, I have no idea what the skin depth is for a human
body. But aluminum foil might make pretty good armor.)
Gregory Loren Hansen
>
><snipped>
>
>> But one thing seems certain, and that is lasers shouldn't even be
>> considered as weapons unless they offer a clear advantage over
>> conventional weapons. There's no reason I can think of not to mount a
>>
>> machine gun on a space ship.
>
>Other than a fuel source. Guns require gun powder and oxygen, which is
The oxygen is tied up in the nitrocellulose. The ammo can fire just fine
underwater or in a vacuum. In fact, there is no way atmospheric oxygen
could get to the powder fast enough to fire a bullet, and the air inside
the casing doesn't provide enough.
>the problem remains that you would have potentially explosive materials
>on board that only require a spark to ignite) Don't forget that you can
>run out of ammo (like photon torpedoes) while you will not run out of
>laser.So I quess we can add safety to the list.
Nevertheless, the U.S. Navy seems to make pretty good use of their ammo.
Usually the battle is over before you run out of ammo, even in the monster
naval battles of World War II.
>> Firing armor-peircing ammunition, it could
>> easily go through a half inch of steel. Bigger guns, like .50-cal
>> or 20mm, can go through much more.
>
>But if you have a two foot piece of steel, it will not penetrate but
>deflect (possibly back at the attacker).
Depends on how big your gun is! How do you think navies expect to sink
aircraft carriers? And no, it won't deflect. It'll squash, making a lead
and copper lined divet. Pistol bullets deflect, but machine guns don't
use pistol ammo. At higher speeds the bullets sort of explode on impact,
taking peices of armor with it in a shower of incandesent metal.
>A laser on a continuous output
>could damage the armour. If stationary, given time the laser (the
>smaller the diameter of the beam the better) would completely penetrate
>the thick hull while the guns would be out of ammo.
Hello? We're talking about weapons, here! Your target won't be
stationary, you won't have the time. And I doubt you'd have a two foot
peice of steel because you'd have to move that two-foot thick armor with
you wherever you go. Weight is a bad thing in a spaceship. Besides,
they'd probably use a composite armor like the Chobam armor that the
Abrams tank has.
A 30mm gatling gun firing depleted uranium bullets at 6000 rounds per
minute would get through the armor a hell of a lot quicker. But I would
tend to favor something with a little more firepower for that job.
>> They can fire reliably for a long
>> time, they're not very big, they need very little power while lasers
>> would
>> need huge amounts of power that must come from somewhere on board the
>> ship. Bullets don't suffer from beam spreading, reflective coatings,
>> only
>> minimally from ablative coatings, they're not affected at all by smoke
>> or
>> metal vapor.
>
>Don't forget that the speed of the bullets and missles are extremely
>slow. Even at 30,000 feet per second, a laser will travel at 186,000
>miles per second. Given ships in ST that are traveling at more than
>30,000 feet per second then guns would be useless because the bullet
>would never reach the target. In fact, the bullet would be an obstical
If we're talking about Star Trek technology, then lasers are still useless
as weapons because the ships are so well shielded and armored. Bullets
become useless weapons to Star Trek ships, too.
But this thread started when someone wanted a realistic way to shield
lasers. So I was going under the assumption of currently realistic
technology, not technology we may or may not see in 400 years. And by
current technology, armor on space ships must be pretty thin, we don't
have terajoule gamma ray lasers, and spaceships don't accelerate at 5000G.
>> If recoil is a problem, resurrect the gyrojet. Use guided
>> missiles.
>
>And how big would this gyro be for a portable weapon. Large enough to
>make it nonportable. So you add more space, more weight, which means
About the size of a 12-gauge shotgun shell. How big is the nuclear power
plant and the cooling system for your laser? The most powerful lasers in
the world are BIG with a capital "ig". Some can be transported with
difficulty, some take up a large room and never leave. They all require
huge amounts of power that Geordi might be able to deliver in a hand-held
package but we can't. For all that, as weapons they're not as effective
as an M-16 with 20 rounds in the mag.
>less ammo. As far a using lasers as a weapon on earth, if you hit the
>fuel tank (and we know that targeting laser can continuously shoot) then
>a jet could be exploded by its own fuel. The laser does not even have
>to be visible.
The laser can continuously shoot, and the pilot can do barrel rolls.
Maneuvor is the first (but not the only) line of defense for a warplane.
>There are advantages and disadvantages to both.
That makes it sound like it's merely a matter of taste whether you want to
arm your F-16 with lasers or Sidewinders.
>> Lasers really do compare poorly as anti-ship weapons. By the time the
>>
>> technology can make them formidable, I suspect there'll be better
>> altnernatives.
>
>Like phasers.
Yep.
me...@cars3.uchicago.edu
In article <5r3t3q$hbb$1...@dismay.ucs.indiana.edu>, glha...@copper.ucs.indiana.edu (Gregory Loren Hansen) writes:
>
>Hadn't thought of that, good technical point. My original reason for
>using a centimeter diameter hole was to compare it to a weapon I knew.
And in this comparison the laser loses, badly.
>But also because you'd expect an effective weapon to take a pretty big
>chunk out of the target. If I got hit by a megajoule pinprick I'm sure it
>would hurt like hell, but then I'd return fire with a slugthrower. (Since
>I'm on the subject, I have no idea what the skin depth is for a human
>body. But aluminum foil might make pretty good armor.)
>--
Hey, maybe those guys who wear aluminum lined caps know something?-)
On second thought, probably not. Their protect their head which in
their case is the least critical area.
Nyrath the nearly wise
Thus spoke Timeout (isa...@mycomputer.com):
> Don't forget that you can
> run out of ammo (like photon torpedoes) while you will not run out of
> laser.
Why won't you run out of laser? As far as I know, lasers require
energy, and currenly there are no high amperage, ship portable,
inexahustable energy sources.
You are inevitably going to run out of fuel for your powerplant
*sometime*.
> But if you have a two foot piece of steel, it will not penetrate but
> deflect (possibly back at the attacker). A laser on a continuous output
> could damage the armour. If stationary, given time the laser (the
> smaller the diameter of the beam the better) would completely penetrate
> the thick hull while the guns would be out of ammo.
I guess you never heard about the self-defeating effects of the
cloud of armor vapor produced by the action of a laser on the target.
Physical shells work better in this case.
Also, target ships under fire seldom willingly make sitting
ducks of themselves. A shell hits and does damage. Start playing
a laser on the ship and it will tend to initiate evasive maneuvers.
> > If recoil is a problem, resurrect the gyrojet. Use guided
> > missiles.
>
> And how big would this gyro be for a portable weapon. Large enough to
> make it nonportable.
Forgive me, but I get the distinct impression that you are unfamiliar
with the term "Gyrojet". The MPC Gyrojet was a prototype military
sidearm produced several decades ago. It actually shot rocket
bullets. Practially no recoil. The firing mechanism was so simple
that it was almost jam-proof. There was a fixed firing pin at the
base of the chamber. A hammer hit the nose of the bullet, and
forced it onto the firing pin. As the rocket flew out, it would
cock the hammer. The rocket bullet had four nozzles, angled so
as to spin the bullet gyroscopically for stability.
It never caught on for a variety of reasons, mostly to do with
the high cost of each round.
As Larry Niven put it, a Gyrojet is an almost irrestistable
item for any Buck Rogers fan.
> > Lasers really do compare poorly as anti-ship weapons. By the time the
> > technology can make them formidable, I suspect there'll be better
> > altnernatives.
>
> Like phasers.
Or like cybernetic voodoo dolls of the enemy ship you
stick with electronic pins to kill it.
"Phaser" is a null-content word. Speculation about them is
futile, since the only thing we know about them is that they
look like a pretty teal beam and they make things vaporize.
Lets stick to things we can get accurate figures on, if you
please. <grin>
* A B S I T * I N V I D I A * V E R B O ** I D E M * S O N A N S *
+----------------------------------------------------------------------------+
| WINCHELL CHUNG http://www.clark.net/pub/nyrath/home.html |
| Nyrath the nearly wise nyr...@clark.net |
+---_---+---------------------[ SURREAL SAGE SEZ: ]--------------------------+
| /_\ | Right theory, wrong universe |
| <(*)> | |
|/_/|\_\| |
| //|\\ | |
+///|\\\+--------------------------------------------------------------------+
Edward Green
Timeout <isa...@mycomputer.com> wrote:
>Gregory Loren Hansen wrote:
>
><snipped>
>
>> But one thing seems certain, and that is lasers shouldn't even be
>> considered as weapons unless they offer a clear advantage over
>> conventional weapons. There's no reason I can think of not to mount a
>> machine gun on a space ship.
Other than recoil, that is. It might be a trifle hard to stabilize
your space ship under the sporadic impulses of a machine gun.
>Other than a fuel source. Guns require gun powder and oxygen, which is
>lacking in space. (Ammo could be designed to mute this argument
I've wondered about this myself. Is there any reason a conventional
..45 would not fire in space? Oxygen is not necessary. It could be
however that exposing conventional shells to vacuum would cause
deterioration of the charge. I wonder if work has been done in this
important area of extending human slaughter to space?
Jeff Sullivan
Edward Green wrote:
>
> Timeout <isa...@mycomputer.com> wrote:
>
> I've wondered about this myself. Is there any reason a conventional
> ..45 would not fire in space? Oxygen is not necessary. It could be
> however that exposing conventional shells to vacuum would cause
> deterioration of the charge. I wonder if work has been done in this
> important area of extending human slaughter to space?
Unless the rounds are sealed against vacuum you would probably get
outgassing
from propelant - not good.
The range of operating environments is much more extreme, requring
design to
cope with the much larger differences in temperature (and thus
expansion)
between components. Even simple cold can turn some metals brittle.
Need to prevent vacuum welding of components.
Need to engineer lubricants that don't evaporate in a vacuum.
Need to cope if space-cold weapons are brought into a humid
environment. Freezing condensation can lead to corrosion, or even
obstruct barrels.
I'm sure there are many more gottchas waiting out there.
--
Jeff Sullivan <je...@division.co.uk> Division Ltd, 19 Apex Court,
Tel: +44 (0) 1454 615554. Woodlands , Almondsbury,
Fax: +44 (0) 1454 615532. Bristol BS12 4JT UK.
Charles Frederick Goodin
me...@cars3.uchicago.edu
In article <5r4sa0$s...@panix2.panix.com>, e...@panix.com (Edward Green) writes:
>Timeout <isa...@mycomputer.com> wrote:
>
>>Gregory Loren Hansen wrote:
>>
>><snipped>
>>
>>> But one thing seems certain, and that is lasers shouldn't even be
>>> considered as weapons unless they offer a clear advantage over
>>> conventional weapons. There's no reason I can think of not to mount a
>>> machine gun on a space ship.
>
>Other than recoil, that is. It might be a trifle hard to stabilize
>your space ship under the sporadic impulses of a machine gun.
>
>>Other than a fuel source. Guns require gun powder and oxygen, which is
>>lacking in space. (Ammo could be designed to mute this argument
>
>I've wondered about this myself. Is there any reason a conventional
>..45 would not fire in space? Oxygen is not necessary. It could be
>however that exposing conventional shells to vacuum would cause
>deterioration of the charge. I wonder if work has been done in this
>important area of extending human slaughter to space?
>
Any conventional weapon will fire in space. And I doubt that exposure
to vacuum will cause any significant deterioration. Even if so, it is
a trifling problem to seal the charge adequately.
Tenhawk
components from the pressure change... I cant think of a situation in
which it would happen though...
Gregory Loren Hansen
In article <5r4sa0$s...@panix2.panix.com>, Edward Green <e...@panix.com> wrote:
>Timeout <isa...@mycomputer.com> wrote:
>
>>Gregory Loren Hansen wrote:
>>
>><snipped>
>>
>>> But one thing seems certain, and that is lasers shouldn't even be
>>> considered as weapons unless they offer a clear advantage over
>>> conventional weapons. There's no reason I can think of not to mount a
>>> machine gun on a space ship.
>
>Other than recoil, that is. It might be a trifle hard to stabilize
>your space ship under the sporadic impulses of a machine gun.
Yeah, well, if machine guns made good rocket engines, the space shuttle
would use machine guns instead of LOX engines. I was just assuming if you
had the technology to, say, project firepower to one of the moons of
Jupiter, then maneuvoring engines could be build to compensate. Or else
you'd use little rockets instead. Or really small bullets that go really
fast.
Actually, I just liked the whole thought of watching a space movie with
space fighters zipping around shooting at each other with machine guns.
And you'd hear the explosions, too. And the smoke would drift up.
>>Other than a fuel source. Guns require gun powder and oxygen, which is
>>lacking in space. (Ammo could be designed to mute this argument
>
>I've wondered about this myself. Is there any reason a conventional
>..45 would not fire in space? Oxygen is not necessary. It could be
>however that exposing conventional shells to vacuum would cause
>deterioration of the charge. I wonder if work has been done in this
>important area of extending human slaughter to space?
I suspect that wouldn't be a problem because I've never heard of gunpowder
evaporating in a normal atmosphere. And the casings are airtight anyway.
Even if there's a leak from overpressure, it would be pretty slow. But I
guess I really don't know.
Some practical problems you will have is designing hand guns so they can
be operated by a guy in a space suit, and finding non-liquid lubricants
like graphite or a teflon coating.
Shawn
In article <33d7cd4b...@news.wco.com>,
Beth and Richard Treitel <tre...@wco.com> wrote:
>To my surprise and delight, nyr...@clark.net (Nyrath the nearly wise)
>wrote:
>
>>More than that, I was under the impression that there is
>>more or less no such thing as a "mirror" for x-rays and gamma rays.
>
>I had the feeling that a suitable crystal could reflect X-rays if the
>angle of incidence was low enough -- but certainly not at 90 degrees.
I'm no expert, but diamond is pretty good at ssplitting up an x-ray. If
you had small enough diamonds with just the right cuts, you might be able
to redirect them, but I doubt you would get 90 degree reflection.
>Not sure what percentage might get reflected.
I'm not sure either 8).
>
>- Richard
Just Me,
*SF
THS
On Mon, 21 Jul 1997 20:42:27 -0400, Timeout <isa...@mycomputer.com> wrote:
>> conventional weapons. There's no reason I can think of not to mount a
>> machine gun on a space ship.
>
>Other than a fuel source. Guns require gun powder and oxygen, which is
>lacking in space. (Ammo could be designed to mute this argument, but
>the problem remains that you would have potentially explosive materials
>on board that only require a spark to ignite) Don't forget that you can
>run out of ammo (like photon torpedoes) while you will not run out of
>laser.So I quess we can add safety to the list.
Lasers require energy as "fuel" (a lot, in a short time) and you could well
run out of that!
>deflect (possibly back at the attacker). A laser on a continuous output
>could damage the armour. If stationary, given time the laser (the
>smaller the diameter of the beam the better) would completely penetrate
>the thick hull while the guns would be out of ammo.How many times would
the stationary assumption seems very unlikely to me. The target is likely
to be defended, you can't just stay in front of it and burn happily away.
>would never reach the target. In fact, the bullet would be an obstical
>in the path of the attacking ship.
No, unless the attacker is accelerating.
>But you still have the problem of
>limited ammo that is potentially explosive.
C'mon, that doesn't stop todays warships, fighter planes etc. form carrying
ammo, does it?
Of course, bullets have the disadvantage of the recoil. For this reason,
and of course for greater destructive power, rockets would be the weapon of
choice, just as they are now!
--
Thomas Scheider - Remove "NOSPAM." for e-mail
http://unet.univie.ac.at/~a9007122
"42"
Gregory Loren Hansen
In article <5r5mn4$7v9$1...@morgoth.sfu.ca>,
Charles Frederick Goodin <goo...@sfu.ca> wrote:
>In article <33D60A...@division.co.uk>,
>Jeff Sullivan <je...@division.co.uk> wrote:
>>
>>Need to prevent vacuum welding of components.
>
>What's vacuum welding?
>
>
It's really cool. Polish up two peices of metal in a vacuum, stick them
together, and they stay together as if they were a single peice!
If you break something on earth and put the peices back together, the
surfaces have a layer of air and vapor that keeps the molecules of the two
halves from making direct contact. When that layer isn't there, as soon
as the peices come together they bind as if they've always been together.
Brian Trosko
Timeout <isa...@mycomputer.com> wrote:
: Other than a fuel source. Guns require gun powder and oxygen, which is
...provided by the gunpowder. Any current firearm'll fire in a vaccuum
just fine.
: > Firing armor-peircing ammunition, it could
: > easily go through a half inch of steel. Bigger guns, like .50-cal
: > or 20mm, can go through much more.
: But if you have a two foot piece of steel, it will not penetrate but
: deflect (possibly back at the attacker).
Er...hardly, any even then only in Hollywood movies. Deflect? Yes,
depending on the angles. Smear itself across the metal? Probably.
Deflect right back at the firer?
That's about as likely as all the atoms in my body suddenly deciding
they'd rather be on Mars.
: the thick hull while the guns would be out of ammo.How many times would
: you have to shoot an elephant with a B B gun to kill it? You probably
: would never kill it.
If the BBs are moving at an appreciable percentage of c, just one. WHen
you're dealing with very big velocities, small chucks of lead can be
obscenely lethal.
: miles per second. Given ships in ST that are traveling at more than
: 30,000 feet per second then guns would be useless because the bullet
: would never reach the target. In fact, the bullet would be an obstical
: in the path of the attacking ship.
What are you talking about? If you're in a ship going 30,000fps and you
fire a bullet that has a muzzle velocity of 3,000fps then the bullet is
going 33,000fps.
: And how big would this gyro be for a portable weapon. Large enough to
: make it nonportable.
Er...no again. The Gyrojet pistol came out back in the 60s. Fired small,
spin-stabilized rockets. Quite portable. It was a handgun, after all.
Isaac Kuo
In article <5r78pl$6...@nntp02.primenet.com>,
Brian Trosko <btr...@primenet.com> wrote:
>Timeout <isa...@mycomputer.com> wrote:
>: the thick hull while the guns would be out of ammo.How many times would
>: you have to shoot an elephant with a B B gun to kill it? You probably
>: would never kill it.
>If the BBs are moving at an appreciable percentage of c, just one. WHen
>you're dealing with very big velocities, small chucks of lead can be
>obscenely lethal.
While this is true, acheiving an appreciable percentage of c is really
really difficult with any sort of solid projectile. Anything
you use to accelerate a projectile will not be 100% efficient and
some percentage of the energy pumped into it will be dumped as heat
into the projectile itself. Given the incredible amount of energy
involved, this will melt/vaporize the projectile unless:
1. The acceleration method is unbelievably efficient.
2. The projectile is mostly a heat sink which gets vaporized off,
leaving a tiny solid projectile. Depending on how unbelievably
efficient the acceleration method is, this may or may not be
practical.
or
3. The projectile is accelerated slowly enough so that it can radiate
away excess heat. This means accelerating over long distances
(light seconds or light minutes in length) with laser propulsion
or RPB propulsion.
IMO, option 3 is the only reasonable possibility, and although it's
very big/expensive, it uses resources which will likely be developed
for non-military purposes anyway. In action, it's hardly anything
like a "gun", of course.
Normal "guns" with muzzle velocities around 1km/s are easy, 10km/s
are plausible, but 100km/s is really pushing it (keeping the barrel
length down to 100km long or so, that is).
>: miles per second. Given ships in ST that are traveling at more than
>: 30,000 feet per second then guns would be useless because the bullet
>: would never reach the target. In fact, the bullet would be an obstical
>: in the path of the attacking ship.
>What are you talking about? If you're in a ship going 30,000fps and you
>fire a bullet that has a muzzle velocity of 3,000fps then the bullet is
>going 33,000fps.
Obviously he either doesn't understand physics or thinks there's a
thick atmosphere in space.
In a situation where projectile delta-V capability + muzzle velocity
is much less than target delta-V capability (which would be the case
if the targets have expensive/massy high Isp rockets unavailable to
missiles), the only way to use the projectiles offensively is to
"sling" them at the target by maneuvering the firing platform on an
approximate intercept course (possibly maneuvering away after firing
the salvo to avoid return fire).
I have a good intuitive feel for this situation from playing the
Amiga version of SpaceWar many years (it features amazingly slow
muzzle velocity torps).
--
_____ Isaac Kuo k...@bit.csc.lsu.edu http://www.csc.lsu.edu/~kuo
__|_>o<_|__
/___________\ "Mari-san... Yokatta...
\=\>-----</=/ ...Yokatta go-buji de..." - Karigari Hiroshi
Timeout
Gregory Loren Hansen wrote:
> I There's no reason I can think of not to mount a machine gun on a
> space ship.
>
> The oxygen is tied up in the nitrocellulose. The ammo can fire just
> fine
> underwater or in a vacuum. In fact, there is no way atmospheric
> oxygen
> could get to the powder fast enough to fire a bullet, and the air
> inside
> the casing doesn't provide enough.
In conventional weapons, all the gunpowder is not burned, the unburned
gunpowder and the little pieces of the bullet would cause the ship (when
traveling at high speeds like in ST) to be destroyed by the debris.
> >the problem remains that you would have potentially explosive
> materials
> >on board that only require a spark to ignite) Don't forget that you
> can
> >run out of ammo (like photon torpedoes) while you will not run out of
>
> >laser.So I quess we can add safety to the list.
>
> Nevertheless, the U.S. Navy seems to make pretty good use of their
> ammo.
> Usually the battle is over before you run out of ammo, even in the
> monster
> naval battles of World War II.
But when you are on a five year mission like the TOS then you will
probably run out of ammo unless you get resupplied.
> >> Firing armor-peircing ammunition, it could
> >> easily go through a half inch of steel. Bigger guns, like .50-cal
> >> or 20mm, can go through much more.
> >
> >But if you have a two foot piece of steel, it will not penetrate but
> >deflect (possibly back at the attacker).
>
> Depends on how big your gun is!
I agree.
> How do you think navies expect to sink
> aircraft carriers? And no, it won't deflect. It'll squash, making a
> lead
> and copper lined divet. Pistol bullets deflect, but machine guns
> don't
> use pistol ammo.
Machine guns are still useless against hardened bunkers. At some point
the bullet will not penetrate because you just can't get enough force
into the bullet to penetrate.
> At higher speeds the bullets sort of explode on impact,
> taking peices of armor with it in a shower of incandesent metal.
And how effective were these bullets against a bunker...not very.
> >A laser on a continuous output
> >could damage the armour. If stationary, given time the laser (the
> >smaller the diameter of the beam the better) would completely
> penetrate
> >the thick hull while the guns would be out of ammo.
>
> Hello? We're talking about weapons, here! Your target won't be
> stationary, you won't have the time.
A bunker is stationary, even underground bunkers. The SR71 couldn't be
hit with conventional weapons because of its extreme speed. A laser
could have brought it down.
> And I doubt you'd have a two foot
> peice of steel because you'd have to move that two-foot thick armor
> with
> you wherever you go.
Army tanks.
> Weight is a bad thing in a spaceship. Besides,
> they'd probably use a composite armor like the Chobam armor that the
> Abrams tank has.
> A 30mm gatling gun firing depleted uranium bullets at 6000 rounds per
> minute would get through the armor a hell of a lot quicker.
Yes, it would, but if traveling at extremely high velocities in space,
then the bullet would take time to get to the ship. Enough time to make
the bullet miss, unlike a laser that would get there almost
instantly.And how much does each one of the 30mm bullets weight...over a
pound maybe two. So 6000 rounds would be 3-6 tons for 60 second for
weapons fire. Additionally, the barrel would melt before it could fire
60 seconds. Seeing how you would want more than one forward mounted
gun, then you would have to have even more ammo. Considering you would
probably want at least enough ammo for 2 minutes of battle, and
> But I would
> tend to favor something with a little more firepower for that job.
I would also.
> But this thread started when someone wanted a realistic way to shield
> lasers.
Sorry about that, I didn't get the first post...either it was posted to
another group first, or my sorting dropped it. But the way to shield
against lasers is to disperse the beam to a level that is not harmful.
> So I was going under the assumption of currently realistic
> technology, not technology we may or may not see in 400 years. And by
>
> current technology, armor on space ships must be pretty thin, we don't
>
> have terajoule gamma ray lasers, and spaceships don't accelerate at
> 5000G.
>
But the space shuttle does travel at 24,000 mph. But I don't think
it(or anything currently in space) would withstand much weapons fire, no
matter what size.
> >> If recoil is a problem, resurrect the gyrojet. Use guided
> >> missiles.
> >
> >And how big would this gyro be for a portable weapon. Large enough
> to
> >make it nonportable. So you add more space, more weight, which means
>
> About the size of a 12-gauge shotgun shell.
A gyro the size of a 12 gauge shotgun shell will eliminate the recoil of
the 30mm gatlin gun on the A10. The govt needs some of those. Since
the documentories say that the recoil slows the ship down. Those guns
can't be mounted on helicopter because of the recoil. You also have to
remember that a gyro will keep a weapon pointing level, so if you
install a gyro, then you wouldn't be able to tilt the gun. As you tilt
the gun(gyro) it would cause an opposing force which would knock your
aim off.I've never heard of a gyro preventing a gun from kicking
anyway. I haven't seen any of the professional shooters for Browning,
Ruger, S&W, nor any of the other using them.
> How big is the nuclear power
> plant and the cooling system for your laser?
It could be smaller because you would be able to use the coldness of
space to cool the laser. Nuclear power is very inefficient. A nuclear
power plant is a big steam turbine. It uses nuclear power to heat water
to create steam to turn a turbine to generate electricity. A coal
generating plant does the same thing, but it uses coal as the heat
source instead of nuclear power. The actual power generation is the
same.
> The most powerful lasers in
> the world are BIG with a capital "ig".
Some of the biggest guns are big. 18 inch guns require an entire ship
to carry them. How many people carry guns bigger than 50 cal. and if
they carry the weapon how much ammo can they carry. I agree that
current lasers are not a good weapon, but I don't believe modern bullets
and weapons would be effective in space once we are able to move
confidently (meaning like driving a car).
> Some can be transported with
> difficulty, some take up a large room and never leave. They all
> require
> huge amounts of power that Geordi might be able to deliver in a
> hand-held
> package but we can't.
We can't, but you could carry a laser with slightly more power than a
laser aiming device and blind the enemy from a very long distance. That
could be hand held. A bigger weapon the size of a chain machine gun
which has a portable generator could be somewhat effective (it could be
used instead of a flame thrower to start fires in a camp , or explode
fuel and weapons depos, and at much greater distances).
> For all that, as weapons they're not as effective
> as an M-16 with 20 rounds in the mag.
A laser would be more effective at the range of 8 miles. The laser
could still blind the person with the M-16. A person will use the
tactics that work for that particular weapon.
> >less ammo. As far a using lasers as a weapon on earth, if you hit
> the
> >fuel tank (and we know that targeting laser can continuously shoot)
> then
> >a jet could be exploded by its own fuel. The laser does not even
> have
> >to be visible.
>
> The laser can continuously shoot, and the pilot can do barrel rolls.
> Maneuvor is the first (but not the only) line of defense for a
> warplane.
A laser travels at the speed of light, and if invisible, the pilot
wouldn't know they were under attack. They would have no reason to
maneuver. Even if the pilot did maneuver, a pilot, no matter how good,
can't dodge a beam of light.
> >There are advantages and disadvantages to both.
>
> That makes it sound like it's merely a matter of taste whether you
> want to
> arm your F-16 with lasers or Sidewinders.
You can't tell me that the turbines on the jet couldn't produce enough
energy to power a good size laser. A laser doesn't have a self destruct
button, or a reasonable safety. Once you fire it, if you miss, you
could destroy someone or something 100 miles away in less than a
fraction of a second. That would be bad news for any government.
Timeout
Nyrath the nearly wise wrote:
> Thus spoke Timeout (isa...@mycomputer.com):
> > Don't forget that you can
> > run out of ammo (like photon torpedoes) while you will not run out
> of
> > laser.
>
> Why won't you run out of laser? As far as I know, lasers require
> energy, and currenly there are no high amperage, ship portable,
> inexahustable energy sources.
> You are inevitably going to run out of fuel for your powerplant
> *sometime*.
>
But not before you run out of ammo. And if you have a way of refueling,
like the E-D does while in flight, then you don't have that problem.
> > But if you have a two foot piece of steel, it will not penetrate but
>
> > deflect (possibly back at the attacker). A laser on a continuous
> output
> > could damage the armour. If stationary, given time the laser (the
> > smaller the diameter of the beam the better) would completely
> penetrate
> > the thick hull while the guns would be out of ammo.
>
> I guess you never heard about the self-defeating effects of the
> cloud of armor vapor produced by the action of a laser on the target.
> Physical shells work better in this case.
A physical bullet would have no effect other than making a sound. BTW,
the govt is to have a laser mounted in a 747 that will be capable of
shooting down a SCUD sided missle at 250 miles.( Popular Science Nov
1996.) "tests, conducted at White Sands Missile Range, N.M.,
demonstrated that TRW's Nautilus laser air defense weapon could acquire
a target and hold a laser beam on it long enough to penetrate a heavy
steel casing and explode the warhead, according to a Ballistic Missile
Defense Organization official." is quoted from Aviation Week & Space
Technology the Mar 25, 1996 issue.(it is a megawatt laser) "The
destruction of the warhead took "only a few seconds, Nautilus could then
be refocused on a new
target in less than a second. Retargeting requires only the fast, quite
small movement of a mirror, a company official said" is another quote.
And another quote "If a missile is fired at a range of 20 mi., the laser
can disable its sensor at 12 mi. or more. If the target is an unguided
missile, it can be destroyed by the laser at 3 mi. or more"
I think that is enough evidence.
> Also, target ships under fire seldom willingly make sitting
> ducks of themselves. A shell hits and does damage. Start playing
> a laser on the ship and it will tend to initiate evasive maneuvers.
>
> > > If recoil is a problem, resurrect the gyrojet. Use guided
> > > missiles.
> >
> > And how big would this gyro be for a portable weapon. Large enough
> to
> > make it nonportable.
>
> Forgive me, but I get the distinct impression that you are unfamiliar
>
> with the term "Gyrojet".
You are correct.
> The MPC Gyrojet was a prototype military
> sidearm produced several decades ago. It actually shot rocket
> bullets. Practially no recoil.
The main word is "rocket" bullet. It is not "just" a bullet.
> The firing mechanism was so simple
> that it was almost jam-proof.
What was the result when the bullet did jam. Probably did a lot more
damage than a regular bullet to the shooter.
> There was a fixed firing pin at the
> base of the chamber. A hammer hit the nose of the bullet, and
> forced it onto the firing pin. As the rocket flew out, it would
> cock the hammer.
As the "Rocket" flew out. It is a rocket, not a bullet.
> > > Lasers really do compare poorly as anti-ship weapons. By the time
> the
> > > technology can make them formidable, I suspect there'll be better
> > > altnernatives.
> >
I think the above reference counters that argument.
> > Like phasers.
>
> Or like cybernetic voodoo dolls of the enemy ship you
> stick with electronic pins to kill it.
Never saw that in ST before. Which episode was that ? <grin>
> "Phaser" is a null-content word. Speculation about them is
> futile, since the only thing we know about them is that they
> look like a pretty teal beam and they make things vaporize.
I find phasers applicable in the ST: tech newsgroup, maybe your post is
inappropriate. <grinning back at you>
> Lets stick to things we can get accurate figures on, if you
> please. <grin>
Look above for the accurate figures.
CFB1
Charles Frederick Goodin wrote:
>
> In article <33D60A...@division.co.uk>,
> Jeff Sullivan <je...@division.co.uk> wrote:
> >
> >Need to prevent vacuum welding of components.
>
> What's vacuum welding?
>
> chuk
When you use standard earth lubricants, they boil away in vacuum. What
happens next is that the moving components seize up(like not having oil
in your car's engine), acting like they are welded together.
--
From Bad Carl's Cavern.
Virus Scan Complete. Windows detected. Delete?(Y/N)
Timeout
Charles Frederick Goodin wrote:
> >Don't forget that the speed of the bullets and missles are extremely
> >slow. Even at 30,000 feet per second, a laser will travel at 186,000
>
> >miles per second. Given ships in ST that are traveling at more than
> >30,000 feet per second then guns would be useless because the bullet
>
> >would never reach the target. In fact, the bullet would be an
> obstical
> >in the path of the attacking ship.But you still have the problem of
> >limited ammo that is potentially explosive.
>
> That's a joke, right? It's not like the speed of a bullet is a
> constant,
> like c. If you fire a bullet (travelling 30 000 fps) out of a ship
> (travelling 3 000 000 fps), you now have a bullet travelling 3 030 000
>
> fps, which is faster than the ship. In fact, who needs guns? Just
> drive
> across your oppenents path and drop a bunch of gravel, and when she
> drives
> into it at 3 000 000 fps, she's in big trouble.
>
> chuk
No, joke. You do not add the speed of objects the way you are doing
near the speed of light. In space, there is space dust which would
completely destroy the unprotected bullet quickly. The gravitational
pull on bigger objects would deviate the bullets path, although slightly
over a couple of hundred yards, dramatically over 100's of miles. Going
back to your example of 3,000,000 fps and 30,000 fps, the projectile is
only 1 percent of the ships speed. If both ships were traveling at
3,000,000 fps and were one second apart then the bullet would take 10
seconds to reach the ship in front (assuming that the bullet didn't get
destroyed first). 10 seconds is plenty of time to react because the
ship would only have to alter the course only slightly. On the other
hand, the laser would hit the ship before the pilot would have time to
react. To destroy the bullet, all the ship in front would have to do is
list out salt or dust. NASA showed a panel on one of the satelites that
was hit by a grain of sand. It put a dent in the aluminum panel about a
half inch deep (from a grain of sand). The bullets could easily be
destroyed before reaching targets (at least in the ST universe).
Gregory Loren Hansen
In article <33D7FD9C...@mycomputer.com>,
Timeout <isa...@mycomputer.com> wrote:
>Gregory Loren Hansen wrote:
>
>> I There's no reason I can think of not to mount a machine gun on a
>> space ship.
>>
>> The oxygen is tied up in the nitrocellulose. The ammo can fire just
>> fine
>> underwater or in a vacuum. In fact, there is no way atmospheric
>> oxygen
>> could get to the powder fast enough to fire a bullet, and the air
>> inside
>> the casing doesn't provide enough.
>
>In conventional weapons, all the gunpowder is not burned, the unburned
>gunpowder and the little pieces of the bullet would cause the ship (when
>traveling at high speeds like in ST) to be destroyed by the debris.
You're confusing speed and acceleration. You really need to find the
speed on intercept and not just take the speed of the ship relative to
whatever point of reference you're using.
Anyway, it'd be hitting dust. Micrometeorites are a bigger problem
because some of them are coming at you, not trying to get away.
>> >the problem remains that you would have potentially explosive
>> materials
>> >on board that only require a spark to ignite) Don't forget that you
>> can
>> >run out of ammo (like photon torpedoes) while you will not run out of
>>
>> >laser.So I quess we can add safety to the list.
>>
>> Nevertheless, the U.S. Navy seems to make pretty good use of their
>> ammo.
>> Usually the battle is over before you run out of ammo, even in the
>> monster
>> naval battles of World War II.
>
>But when you are on a five year mission like the TOS then you will
>probably run out of ammo unless you get resupplied.
We're not. If we were on a five year mission we'd have something better
than lasers to shoot things with.
>> How do you think navies expect to sink
>> aircraft carriers? And no, it won't deflect. It'll squash, making a
>> lead
>> and copper lined divet. Pistol bullets deflect, but machine guns
>> don't
>> use pistol ammo.
>
>Machine guns are still useless against hardened bunkers. At some point
>the bullet will not penetrate because you just can't get enough force
>into the bullet to penetrate.
Well, if you're trying to destroy a hardened bunker, I'd suggest a LAW,
AT-4, a flamethrower and a few guys with grenades, a tank, artillery...
the possibilities are endless, but the doctrine for hitting hardened
bunkers has been pretty well worked out.
On the other hand, if I was in that hardened bunker and some guy with a
laser was trying to burn his way in, I'd shoot him.
>> Hello? We're talking about weapons, here! Your target won't be
>> stationary, you won't have the time.
>
>A bunker is stationary, even underground bunkers.
For underground bunkers, it's hard to beat a large artillery barrel packed
with high explosives, dropped from a great height by an airplane with a
guidance system. It'll penetrate tens of feet of dirt before it explodes.
The war will be over by the time a laser gets there.
>The SR71 couldn't be
>hit with conventional weapons because of its extreme speed. A laser
>could have brought it down.
What laser?
Besides, I've been assuming we're using lasers in space. Using lasers in
an atmosphere has its own problems, like divergence caused by heating of
the air, even ionizing the air making it a blackbody absorber. Not to
mention the mundane problems like clouds.
>> And I doubt you'd have a two foot
>> peice of steel because you'd have to move that two-foot thick armor
>> with
>> you wherever you go.
>
>Army tanks.
If I was the guy in the tank and someone was trying to burn his way in
with a laser, the smoke dispensers would already have discharged.
They're supposed to obscure laser targeting systems, but they'd work fine
against laser weapons, too. When I run out of smoke, I'd shoot him. Or
just ignore him. It's not like he's going to do anything to a tank with
any laser he can carry, or pack in a truck, or build a building around.
I'd be more concerned about some yahoo in the bushes ready to shoot a
rocket at me as soon as the thin armor is exposed.
>> Weight is a bad thing in a spaceship. Besides,
>> they'd probably use a composite armor like the Chobam armor that the
>> Abrams tank has.
>> A 30mm gatling gun firing depleted uranium bullets at 6000 rounds per
>> minute would get through the armor a hell of a lot quicker.
>
>Yes, it would, but if traveling at extremely high velocities in space,
>then the bullet would take time to get to the ship. Enough time to make
>the bullet miss,
What kind of spaceship are you driving? A 20mm gatling gun is part of the
Phalanx system that (among other things) protects U.S. warships. It can
shoot down planes a mile away that can pull 8 G's. You're not going to do
better than that without passing out, the pilots only do that with
training, conditioning, and a flight suit.
If it was merely velocity that you're worried about, compensating for that
is an old trick. The Abrams tank does that, plus accounting for air
density, wind speed, range, and barrel warpage.
>unlike a laser that would get there almost
>instantly.
And do what? Make a puff of smoke on the hull? That's the primary
finding in my calculations, that lasers are just too darn weak to be used
as a weapon.
>And how much does each one of the 30mm bullets weight...over a
>pound maybe two. So 6000 rounds would be 3-6 tons for 60 second for
>weapons fire. Additionally, the barrel would melt before it could fire
>60 seconds. Seeing how you would want more than one forward mounted
>gun, then you would have to have even more ammo. Considering you would
>probably want at least enough ammo for 2 minutes of battle, and
Firstly, it wouldn't take two minutes worth of firing to shred a
spaceship. Secondly, that was a fer instance. You could mount a .50-cal
machine gun if you want. You could install a coil gun or a rail gun. The
best performance I know of for a rail gun is shooting a 4 pound projectile
14 miles per second, and an idea I've seen for application is to shoot
plastic pellets out of a rail gun because they're light and minimize
recoil but still carry all the energy to the target. You could
install pretty much any conventional weapon and it would be more effective
than any laser you'll be able to find. You could install a guided missile
launcher and a reloader; 40 missiles could destroy up to 40 enemy ships
and that's an unrealistically good kill ratio. Even a neutral particle
beam might have more effect if the particles penetrate a centimeter on
average. But I wouldn't go with a charged particle beam because they're
too easy to deflect with a magnetic field.
>Sorry about that, I didn't get the first post...either it was posted to
>another group first, or my sorting dropped it. But the way to shield
>against lasers is to disperse the beam to a level that is not harmful.
Smoke, water vapor, mirrored surfaces, ablative armor. Turns out, though,
with a terajoule laser pulse penetrating about .00004 centimeters of iron,
there's no reason to bother. The lasers in the SDI program were pulsed
lasers, with time between each pulse for the metal vapor to clear. That
gives considerably better penetration, but they were still expected to
destroy missiles by weaking them enough that they'd crumple when they
reenter the atmosphere. It's not like they were supposed to cut the
missiles in half. Critics of SDI claim that it would be cheaper to
protect the missiles than it would be to build the weapons. Spinning was
one proposed defense, because that wouldn't let you keep the beam on one
spot long enough to do any real damage. The SDIO seemed to have dropped
lasers and moved on to "brilliant pebbles", which are guided projectiles.
For our purposes, that suggests the SDIO found out lasers wouldn't make
very good weapons even in space against thinly armored targets that move
predictably.
>> So I was going under the assumption of currently realistic
>> technology, not technology we may or may not see in 400 years. And by
>>
>> current technology, armor on space ships must be pretty thin, we don't
>>
>> have terajoule gamma ray lasers, and spaceships don't accelerate at
>> 5000G.
>>
>
>But the space shuttle does travel at 24,000 mph.
It gets there by accelerating for a long time at several Gs.
>But I don't think
>it(or anything currently in space) would withstand much weapons fire, no
>matter what size.
Right. Our space vehicles can withstand micrometeorites and the stresses
of launch and reentry (which aren't trivial). But aren't much good
against anything people are likely to call a weapon. In science fiction
we can extrapolate to space warships with armor. But unless you want to
just start making up things like warp engines, there's still some very
real limitations we have to be aware of. And when you start making things
up, you may as well make up a new armor that bullets can't penetrate and
I can make up a new heat superconductor that spreads out laser energy so
quickly you can't heat up a single spot enough to damage it. But if
that's the case, science is always at a disadvantage because the human
imagination can bound away faster than technology can follow.
>> >> If recoil is a problem, resurrect the gyrojet. Use guided
>> >> missiles.
>> >
>> >And how big would this gyro be for a portable weapon. Large enough
>> to
>> >make it nonportable. So you add more space, more weight, which means
>>
>> About the size of a 12-gauge shotgun shell.
>
>A gyro the size of a 12 gauge shotgun shell will eliminate the recoil of
>the 30mm gatlin gun on the A10. The govt needs some of those. Since
>the documentories say that the recoil slows the ship down. Those guns
>can't be mounted on helicopter because of the recoil. You also have to
>remember that a gyro will keep a weapon pointing level, so if you
>install a gyro, then you wouldn't be able to tilt the gun. As you tilt
>the gun(gyro) it would cause an opposing force which would knock your
>aim off.I've never heard of a gyro preventing a gun from kicking
>anyway. I haven't seen any of the professional shooters for Browning,
>Ruger, S&W, nor any of the other using them.
Hmm, I think you misunderstand. A gyrojet is a weapon developed some time
ago. It's a rocket-propelled bullet. It has four nozzles that are angled
to spin-stablize the bullet. It has very little recoil, and it also needs
about ten feet before it can get up to lethal speeds. It never caught on
for various reasons including cost and the fact that it really didn't
improve on the .45 auto or the traditional combat rifle.
>> How big is the nuclear power
>> plant and the cooling system for your laser?
>
>It could be smaller because you would be able to use the coldness of
>space to cool the laser.
Depends on how the laser is constructed. You may have to cool internal
parts that can't be exposed to the vacuum, or you might need a water
jacket or something if the heat can't flow from inside to outside quickly
enough.
>Nuclear power is very inefficient. A nuclear
>power plant is a big steam turbine. It uses nuclear power to heat water
>to create steam to turn a turbine to generate electricity. A coal
>generating plant does the same thing, but it uses coal as the heat
>source instead of nuclear power. The actual power generation is the
>same.
A nuclear power plant is as efficient as any other steam engine. But it
has the highest energy density we can control, that's why so many
submarines and aircraft carriers use them. If you're going to be shooting
lasers in space, then nuclear is the only way I know of to go. But space
reactors are less efficient because they're gas-cooled. I did see a
sketch of a space reactor that uses a spinning chamber to seperate steam
from water (since you can't rely on gravity to do it for you). That would
be more efficient because you get a phase change, but I don't know if it
was ever built.
>> The most powerful lasers in
>
>> the world are BIG with a capital "ig".
>
>Some of the biggest guns are big. 18 inch guns require an entire ship
>to carry them.
But the difference is the 16 inch guns can put a slug through several feet
of steel, or make a crater fifty feet wide. (I think only the Yamato had
18 inch guns, and that was sunk during WWII.) And they can keep on firing
without needing twice the ship's weight in power plant.
>How many people carry guns bigger than 50 cal. and if
>they carry the weapon how much ammo can they carry.
Soldiers often carry anti-tank rockets and grenade launchers. They
usually don't carry .50 cal (although some snipers do), but a rifleman has
about a hundred rounds easily at hand and more tucked away, plus
hand grenades. The machine gunner carries about 400 rounds and has more
ammo distributed throughout the squad. The APC has a .50 cal and a Dragon
anti-tank rocket. They might have Stingers. The modern combat squad
carries a lot of firepower. No high-energy laser facility on Earth can
match it, or the mobility, or the ruggedness.
>I agree that
>current lasers are not a good weapon, but I don't believe modern bullets
>and weapons would be effective in space once we are able to move
>confidently (meaning like driving a car).
Depends on what you mean by "move confidently". Modern bullets and
weapons can shoot down airplanes that can turn so fast the pilot blacks
out.
>We can't, but you could carry a laser with slightly more power than a
>laser aiming device and blind the enemy from a very long distance. That
>could be hand held.
That is an option being explored by the military. It may have been
rejected for ethical reasons, I'm not sure. (Strangely enough,
intentionally maiming a soldier for life is considered unethical, but
killing him outright isn't.)
>A bigger weapon the size of a chain machine gun
>which has a portable generator could be somewhat effective (it could be
>used instead of a flame thrower to start fires in a camp , or explode
>fuel and weapons depos, and at much greater distances).
I don't know the status of any research like that. But I think you'd need
some compelling reasons to use a laser instead of a mortar with incendiary
shells.
>> For all that, as weapons they're not as effective
>> as an M-16 with 20 rounds in the mag.
>
>A laser would be more effective at the range of 8 miles. The laser
Actually, I'm not so sure about that. Besides the mere fact that you
won't see a target 8 miles away due to hills, trees, camouflage, etc. On
the clearest of days you may still have too much absorption and divergence
of the beam to be effective at 8 miles, and military minds never assume
they'll be working with ideal conditions.
>> The laser can continuously shoot, and the pilot can do barrel rolls.
>> Maneuvor is the first (but not the only) line of defense for a
>> warplane.
>
>A laser travels at the speed of light, and if invisible, the pilot
>wouldn't know they were under attack. They would have no reason to
>maneuver. Even if the pilot did maneuver, a pilot, no matter how good,
>can't dodge a beam of light.
If the laser is powerful enough to burn into fuel tanks, I suspect it
would have the same special effects as a flash of lightning. Or a sensor
could look for scattered light. And you'd need a beam shining in exactly
the same spot for a long time, which you probably can't do even if the
pilot isn't trying to dodge because the plane would be wiggling from
turbulence, the hand twitching at the stick, etc. Or from density
fluctuations in air, the same mechanism that makes the stars twinkle. In
any case, if it's a problem it wouldn't be much trouble to install
temperature sensors on the plane, or ablative armor on the tanks. Or to
locate the person shooting the beam and send a missile his way.
What you describe might be possible some day. But the fact that it's not
currently being used means there are better ways to do the same thing.
>> >There are advantages and disadvantages to both.
>>
>> That makes it sound like it's merely a matter of taste whether you
>> want to
>> arm your F-16 with lasers or Sidewinders.
>
>You can't tell me that the turbines on the jet couldn't produce enough
>energy to power a good size laser. A laser doesn't have a self destruct
>button, or a reasonable safety. Once you fire it, if you miss, you
>could destroy someone or something 100 miles away in less than a
>fraction of a second. That would be bad news for any government.
No, the turbines on a jet couldn't produce enough energy to power a laser
that would accidently destroy something 100 miles away in less than a
fraction of a second. They certainly produce enough energy to power, say,
a CO2 cutting laser, the kind used in manufacturing. But laser
manufacturing is a very different environment. Nobody on earth has the
technology to make the scenario you described.
Gregory Loren Hansen
In article <33D80B72...@mycomputer.com>,
Timeout <isa...@mycomputer.com> wrote:
>A physical bullet would have no effect other than making a sound. BTW,
>the govt is to have a laser mounted in a 747 that will be capable of
>shooting down a SCUD sided missle at 250 miles.( Popular Science Nov
>1996.) "tests, conducted at White Sands Missile Range, N.M.,
>demonstrated that TRW's Nautilus laser air defense weapon could acquire
>a target and hold a laser beam on it long enough to penetrate a heavy
>steel casing and explode the warhead, according to a Ballistic Missile
>Defense Organization official." is quoted from Aviation Week & Space
>Technology the Mar 25, 1996 issue.(it is a megawatt laser) "The
>destruction of the warhead took "only a few seconds, Nautilus could then
>be refocused on a new
>target in less than a second. Retargeting requires only the fast, quite
>small movement of a mirror, a company official said" is another quote.
>And another quote "If a missile is fired at a range of 20 mi., the laser
>can disable its sensor at 12 mi. or more. If the target is an unguided
>missile, it can be destroyed by the laser at 3 mi. or more"
Now that is pretty cool. I'll have to look that one up.
>I think that is enough evidence.
Depends on what you're going to use it for. It's a lot easier to destroy
a SCUD than many other targets.
Gregory Loren Hansen
In article <33D7EC49...@mycomputer.com>,
Timeout <isa...@mycomputer.com> wrote:
> No, joke. You do not add the speed of objects the way you are doing
>near the speed of light. In space, there is space dust which would
>completely destroy the unprotected bullet quickly.
You underestimate the vacuum of space. If satellites usually stay intact
for decades, I don't expect a bullet to be destroyed in a few seconds.
>The gravitational
>pull on bigger objects would deviate the bullets path, although slightly
>over a couple of hundred yards, dramatically over 100's of miles.
Easily corrected for by a computer.
>Going
>back to your example of 3,000,000 fps and 30,000 fps, the projectile is
>only 1 percent of the ships speed. If both ships were traveling at
>3,000,000 fps
Are they going toward each other, in the same direction, or non-parallel?
That's a very important point.
>and were one second apart then the bullet would take 10
>seconds to reach the ship in front (assuming that the bullet didn't get
>destroyed first).
If they stay one second apart, they must be going in the same direction.
>10 seconds is plenty of time to react because the
>ship would only have to alter the course only slightly.
But what engine would the ship have to it can change course so quickly?
High-thrust engines will get you to orbit and then you're ballistic. Ion
engines and other high-energy engines have a high specific impulse but
very low thrust. Maybe you could have some chemical maneuver rockets or
something.
>On the other
>hand, the laser would hit the ship before the pilot would have time to
>react. To destroy the bullet, all the ship in front would have to do is
>list out salt or dust.
That would have about as much effect on the bullet as a sandstorm, but
without the wind and probably a lower sand density.
But if the two ships were approaching each other at 3,000,000 fps, dumping
sand on an intersect course would be a fine way to destroy the other ship!
>NASA showed a panel on one of the satelites that
>was hit by a grain of sand. It put a dent in the aluminum panel about a
>half inch deep (from a grain of sand). The bullets could easily be
>destroyed before reaching targets (at least in the ST universe).
Well, that was _a_ dent in _a_ panel on _a_ satellite that may have been
in orbit for ten years. Sometimes that sort of thing happens. But if
space were as dense as you seem to think, we'd have a real problem with
keeping communication satellites, weather satellites, and spy satellites
intact, and with putting men on the moon or rovers onto Mars.
To destroy the bullet before it reaches the target, you'd have to shoot
it.
Isaac Kuo
>> >Don't forget that the speed of the bullets and missles are extremely
>> >slow. Even at 30,000 feet per second, a laser will travel at 186,000
>> >miles per second. Given ships in ST that are traveling at more than
>> >30,000 feet per second then guns would be useless because the bullet
>> >would never reach the target. In fact, the bullet would be an
>> obstical
>> >in the path of the attacking ship.But you still have the problem of
>> >limited ammo that is potentially explosive.
>> That's a joke, right? It's not like the speed of a bullet is a
>> constant,
>> like c. If you fire a bullet (travelling 30 000 fps) out of a ship
>> (travelling 3 000 000 fps), you now have a bullet travelling 3 030 000
>> fps, which is faster than the ship.
This is true...
>>In fact, who needs guns? Just
>> drive
>> across your oppenents path and drop a bunch of gravel, and when she
>> drives
>> into it at 3 000 000 fps, she's in big trouble.
But this is at best misleading, at worst, wrong. If you "drop a bunch
of gravel", when moving at 10km/s, the gravel will merrily travel
alongside you until you maneuver in some way. There isn't any
atmosphere to slow the gravel down.
If you are indeed on an intercept course with the target, "dropping
gravel" could hit the target--but so will you if you don't maneuver
off the intercept course. This assumes the target blithely doesn't
maneuver, of course.
> No, joke. You do not add the speed of objects the way you are doing
>near the speed of light.
3,000,000 fps is nowhere near the speed of light.
>In space, there is space dust which would
>completely destroy the unprotected bullet quickly.
No there isn't. Not at these speeds, by any stretch of the imagination.
>The gravitational
>pull on bigger objects would deviate the bullets path, although slightly
>over a couple of hundred yards, dramatically over 100's of miles.
Gravitational pull is something which can be calculated and accounted
for. Every gunnery fire control system in the world from .22 rifle
open sights to Iowa class battleship fire control necessarily takes
it into account to some extent. With repeated salvos, an Iowa can
literally put a shell right on top of a target 40 miles away, even
with the much greater variabilities of wind.
>Going
>back to your example of 3,000,000 fps and 30,000 fps, the projectile is
>only 1 percent of the ships speed. If both ships were traveling at
>3,000,000 fps and were one second apart then the bullet would take 10
>seconds to reach the ship in front (assuming that the bullet didn't get
>destroyed first).
Why assume they are 3,000,000 feet apart, moving in the same direction
and speed? These two ships aren't interested in engaging each other?
My, how peaceful!
A more aggressive situation is that they are "1 second apart",
meaning that they are on an intercept course and will hit each
other 1 second from now (if neither ship maneuvers). Any
bullets fired will intercept the target slightly sooner than
1 second from now.
>10 seconds is plenty of time to react because the
>ship would only have to alter the course only slightly.
You simply don't understand the maneuvering works in space if
you think in terms of "altering course". In space, there is
no atmosphere or ocean or road to push wings or hulls or wheels
against. You can't just alter your course by rotating your
vessel. You have to use rockets or external means to accelerate
to change course.
>On the other hand, the laser would hit the ship before the pilot
>would have time to react.
Or the laser could miss, depending on if the laser was aimed well
and/or the target maneuvered since the laser was fired.
At any rate, this is more true today than it would be in space,
because today's soldiers and weapons fight at ranges where the
time delay for lasers is practically zero. In contrast to lasers,
missiles can take _minutes_ to reach their targets, today.
However, despite this obvious advantage lasers have, they aren't
used directly as weapons today. Puzzling, isn't it? (sarcasm)
>To destroy the bullet, all the ship in front would have to do is
>list out salt or dust.
Easier said than done. The salt/dust would drift alongside the
ship. There's no such thing as the "ship in front".
We have the concept of destroying incoming projectiles today;
it's called CIWS. Some of the better systems do a marvelous
job of chewing up an incoming missile--into lots of bits of
debris which still hit and severely damage the target ship
(but hey, it would have been a lot worse if the missile hit
intact, and thus detonated its warhead within the ship).
In space, a CIWS would have a similar effect, except that there
isn't any atmosphere to slow down the remaining bits of debris.
Basically, it isn't worth the effort. You need to intercept
the incoming projectiles at a distance.
>NASA showed a panel on one of the satelites that
>was hit by a grain of sand. It put a dent in the aluminum panel about a
>half inch deep (from a grain of sand). The bullets could easily be
>destroyed before reaching targets (at least in the ST universe).
Actually, they couldn't, if the bullets were made of "solid duranium".
As we all know, security doors made of solid duranium take hours of
phaser fire to melt through. (sarcasm again)
Isaac Kuo
>> I There's no reason I can think of not to mount a machine gun on a
>> space ship.
>In conventional weapons, all the gunpowder is not burned, the unburned
>gunpowder and the little pieces of the bullet would cause the ship (when
>traveling at high speeds like in ST) to be destroyed by the debris.
No they wouldn't. First off, the unburned bits of gunpowder will be
moving away from the ship. There isn't any atmosphere to slow the
bits of gunpowder down so that they would hit the ship, and even if
there were, the atmosphere itself would be impacting the ship with
a lot more energy (for instance, when travelling through a typical
ST nebula).
>> Nevertheless, the U.S. Navy seems to make pretty good use of their
>> ammo.
>> Usually the battle is over before you run out of ammo, even in the
>> monster
>> naval battles of World War II.
>But when you are on a five year mission like the TOS then you will
>probably run out of ammo unless you get resupplied.
There was nothing about TOS's five year mission which said anything
about not being resupplied. Indeed, they spent a lot of time back
in Federation space.
As for ammunition, I think you could count the number of times the
old Enterprise fired its phasers on your fingers in those 5 years.
They weren't on a military campaign.
>> Hello? We're talking about weapons, here! Your target won't be
>> stationary, you won't have the time.
>A bunker is stationary, even underground bunkers. The SR71 couldn't be
>hit with conventional weapons because of its extreme speed. A laser
>could have brought it down.
Actually, the SR71 couldn't be taken down with earlier weapons
because of its high altitude. The high speed was necessary to
fly so high up in the rarefied atmosphere.
No laser in existence today could take an SR71 down, but
conventional weapons designed to intercept the threat of
the Valkerie bombers could. (The development of the Mig-25
and its long range missiles nullified the advantage the
Valkerie would have given, so the program was shelved.)
>> And I doubt you'd have a two foot
>> peice of steel because you'd have to move that two-foot thick armor
>> with
>> you wherever you go.
>Army tanks.
No army tank has two feet of steel, because that's too heavy even
for a heavy main battle tank. The best protected main battle tanks
have about 2 feet thick of composite armor, but this weighs _less_
than 2 feet of steel (in a sense, composite armor trades of volume
for mass).
>> How big is the nuclear power
>> plant and the cooling system for your laser?
>It could be smaller because you would be able to use the coldness of
>space to cool the laser.
Man, you really don't know anything about the problem of heat
rejection in space. Space, being practically a vacuum, has
_no_ ability to absorb heat by conduction. You're left with
heat rejection by radiation, and this is a lot tougher than
heat rejection in an atmosphere.
>Nuclear power is very inefficient.
Compared to what?
>A nuclear power plant is a big steam turbine.
Not necessarily. In most terrestrial applications, a steam
turbine is used because it is very _efficient_. However,
turbines are relatively high maintanaince and somewhat heavy
compared to the alternatives.
In space applications, especially unmanned, low maintanaince
low mass systems are desirable.
Nyrath the nearly wise
> Charles Frederick Goodin wrote:
> >
> > In article <33D60A...@division.co.uk>,
> > Jeff Sullivan <je...@division.co.uk> wrote:
> > >
> > >Need to prevent vacuum welding of components.
> >
> > What's vacuum welding?
IIRC, closely fitting pieces of metal tend to "weld" themselves
together in vaccum. This doesn't happen on Earth because the
pieces of metal are protected by a layer of molecules provided
by the atmosphere. No atmosphere - no protection.
If the metallic surfaces are machined sufficiently flat,
they will weld even in an atmosphere. I've heard of
"Foucault cubes" that will weld into one piece of metal
if you press their flat faces in contact.
Brian Trosko
Timeout <isa...@mycomputer.com> wrote:
: In conventional weapons, all the gunpowder is not burned, the unburned
: gunpowder and the little pieces of the bullet would cause the ship (when
: traveling at high speeds like in ST) to be destroyed by the debris.
Again, no. If the ship's going 30,000fps and fires a bullet at 3,000fps,
then the bullet is traveling at 3,000fps relative to that ship. If bits
of debris leave the barrel, they're going to be traveling at less than
3,000fps relative to that ship. How's that going to destroy that ship?
: Machine guns are still useless against hardened bunkers. At some point
: the bullet will not penetrate because you just can't get enough force
: into the bullet to penetrate.
Then you use a bigger bullet.
: space to cool the laser.
Radiative cooling is very inefficient. To use the vaccuum of space to
cool the laser, you're going to need a very large radiator surface.
: You can't tell me that the turbines on the jet couldn't produce enough
: energy to power a good size laser.
They don't. A good-size laser would be something on the order of
megawatts. A modern destroyer has enough generating capacity to devote 6
megawatts of power just to the radars; it could handle that sort of load.
But an F-16? No way. The Anti-Ballistic Missile laser currently being
developed flies on a 747, but that's a chemical laser and isn't pumped by
on-board power.
Gregory Loren Hansen
In article <33D979DC...@mycomputer.com>,
Timeout <isa...@mycomputer.com> wrote:
>Isaac Kuo wrote:
Don't mind me. I just like to talk about spaceships.
>> >> That's a joke, right? It's not like the speed of a bullet is a
>> >> constant,
>> >> like c. If you fire a bullet (travelling 30 000 fps) out of a ship
>>
>> >> (travelling 3 000 000 fps), you now have a bullet travelling 3 030
>> 000
>> >> fps, which is faster than the ship.
>>
>> This is true...
>
>Not entirely...if you are traveling at 99% the speed of light and shoot
>a projectile at 10% the speed of light, it does not exceed the speed of
>light.
But if you fired the projectile, then it's going 10% the speed of light
relative to you. And if you're following (or being followed by) another
ship with the same velocity you have, it's going 10% the speed of light
relative to the target.
>> 3,000,000 fps is nowhere near the speed of light.
>>
>> >In space, there is space dust which would
>> >completely destroy the unprotected bullet quickly.
>>
>> No there isn't. Not at these speeds, by any stretch of the
>> imagination.
>>
>
>There is plenty of space junk around the Earth, and some of the junk has
>left the confines of earth. And none of the asteroid leave any debris
>behind either do they. Lots of debris in space.
But the debris density is low enough that we can send men up in orbit with
a reasonable chance that the shuttle and the men won't be punched up with
millions of holes. Space dust *could* destroy the bullet, but don't bet
your life on it.
>Granted it is easy on earth where you have almost all the variable
>factors, but in space, you would have to calculate the gravitational
>pull of all objects in the area. Another ship, another planet,
>everything. These calculations would have to be done on a continuous
>basis making minor adjustments between each shot. And at 3,000,000 fps
>(2,045,455 mph) That is about half way from Earth to Mars in one hour to
>give a real comparison. There are several objects that could divert a
>bullets by gravitational forces.
Easily done with machines you can get at Best Buy (except they wouldn't
meet milspecs). The positions of the planets and moons are well known,
and we can neglect spaceships as having negligible influence. In fact,
you can neglect everything except the planet and moons you're closest to.
And you wouldn't want just a passive firing system. You'd want feedback,
like the Phalanx system which tracks target and bullets by radar and makes
corrections until the two come together. The relative velocities are
easily accounted for (but if they're both going 3,000,000 fps in the same
direction there's nothing to account).
>> You simply don't understand the maneuvering works in space if
>> you think in terms of "altering course". In space, there is
>> no atmosphere or ocean or road to push wings or hulls or wheels
>> against. You can't just alter your course by rotating your
>> vessel. You have to use rockets or external means to accelerate
>> to change course.
>
>If a ship can travel 3,000,000 fps (which the space shuttle travels at
>35,200fps for comparison) then altering the course would be easily
>accomplished. The thrusters would be superior, everything would be
>superior.
Funny thing about spaceship engines is that high thrust means very low
duration, long duration and high energies mean low thrust. High thrust
engines include the hydrogen-oxygen engines on the space shuttle, kerosene
and oxygen, and other chemical thrusters. Although none are in use, you
could also include nuclear-thermal engines which would heat hydrogen by
passing it through a fission reactor, although the performance advantage
of that is because of the low weight of hydrogen, not because the reactor
can give higher temperatures (the nuclear temperature would actually be
lower). The engines you want for long-range travel, the ion engines,
electromagnetic engines, fusion, solar sails, photon drive, can bring you
up to really good speeds because they can keep on firing for a long time.
An acceleration of a meter per second per second for a month can get you
nearly to 1% of the speed of light. Ion engines and a few plasma-type
engines are used for station keeping in satellites because they can fire
for a long time without being refueled, and because satellites are in
no hurry.
There's a few engines that could combine high thrust and high specific
impulse. One of them (my favorite) is the Orion drive. Basically, the
ship has a big shield in the back, and it throws nuclear bombs behind it.
This idea was tested with a small model and bombs of high explosives.
This has the added benefit that each blast can pump x-ray lasers (although
the lasers are vaporized in the process and must be replaced after each
shot). This scheme has been banned by treaty.
Nuclear-pumped x-ray lasers are another interesting device. Surround a
nuclear bomb by a hundred lasing rods. Point each one at a different
target, then explode the bomb. Each rod will shoot an intense x-ray burst
before it vaporizes. That was a scheme proposed for SDI, each burst
doing enough damage to an ICBM that it would be destroyed on reentry. The
concept has been successfully tested in at least one underground blast.
But the subsequent ban on nuclear testing hindered further development and
the project was dropped, probably for political reasons.
Another, that I've seen described by Forward, although I don't know if
he's the one who thought of it, shoots out methane or hydrogen behind the
ship. And it shoots a stream of antimatter into the propellant cloud,
which reacts in the expected way. The resulting high-temperature plasma
is contained in a magnetic nozzle, and the reaction happens outside of the
confines of the ship, which is protected by a heat shield that can also
double as the heater for a power plant. By keeping the reaction outside
of the ship, the temperature of the propellant can go much higher without
melting the engine, and your specific impulse goes up accordingly. This
scheme suffers mostly from the high cost of producing antimatter, and
probably from the strength of the magnet.
An interesting observation made by an author whose name I forget is that
the better a device is as an engine for a spaceship, the better it also is
as a weapon.
Even with low-thrust main engines, a ship could have chemical rockets for
evasion. They'd be no more effective than the aerobatics of a fighter
plane and harder to sustain, but a moving target is still harder to hit.
>> However, despite this obvious advantage lasers have, they aren't
>> used directly as weapons today. Puzzling, isn't it? (sarcasm)
>
>Actually, it is not puzzling. A laser can travel 186,000 miles per
>second. If you do miss you target, there is no fail safe. There is no
>self-destruct like on a missle. The is no limited range like with
>bullets. This could be a scenario if they used lasers as offensive
>weapons. You shoot at a hostile jet on the horizon, for some reason you
>miss, and 3,000 miles away an international commuter plane is
>destroyed. That is a reason for not using lasers as offensive weapons.
And that is the reason lasers are not being used today as offensive
weapons?
>> >To destroy the bullet, all the ship in front would have to do is
>> >list out salt or dust.
>>
>> Easier said than done. The salt/dust would drift alongside the
>> ship. There's no such thing as the "ship in front".
>
>Not if you place the dust or salt in a persurized compartment. The
>decompression would cause the salt/dust to be blown away from the ship.
Right. Although blowout speeds would be a small fraction of the bullet
speed. You could also use something like sand-filled claymore mines, but
I'm not sure if that would be worthwhile.
The best defense against any weapon is to foil the targeting system, not
the weapon itself. This can be done with stealth technology, flares and
chaff, electronic warfare, even smoke to obscure you from visual
targeting.
Timeout
Gregory Loren Hansen wrote:
> >But when you are on a five year mission like the TOS then you will
> >probably run out of ammo unless you get resupplied.
>
> We're not. If we were on a five year mission we'd have something
> better
> than lasers to shoot things with.
Like that atom laser that doesn't suffer from beam disfusion. But the
laser would be better than bullets. That is my point which you just
supported.
> >Machine guns are still useless against hardened bunkers. At some
> point
> >the bullet will not penetrate because you just can't get enough force
>
> >into the bullet to penetrate.
>
> Well, if you're trying to destroy a hardened bunker, I'd suggest a
> LAW,
> AT-4, a flamethrower and a few guys with grenades, a tank,
> artillery...
> the possibilities are endless, but the doctrine for hitting hardened
> bunkers has been pretty well worked out.
Again, you support my side because a laser would do better than bullets.
> On the other hand, if I was in that hardened bunker and some guy with
> a
> laser was trying to burn his way in, I'd shoot him.
Good luck since the laser can do it at a 250 mile range. The govt will
have one in a Boing 747 in a few years that can shoot down a missle at
250 a range of 250 miles, research has already proved missles can be
completely destroyed at ranges over 3 miles by lasers, so again I say.
Good luck at shooting the person aiming the weapon.
> For underground bunkers, it's hard to beat a large artillery barrel
> packed
> with high explosives, dropped from a great height by an airplane with
> a
> guidance system. It'll penetrate tens of feet of dirt before it
> explodes.
> The war will be over by the time a laser gets there.
And again this is support for a laser and against bullets.
> Besides, I've been assuming we're using lasers in space. Using lasers
> in
> an atmosphere has its own problems, like divergence caused by heating
> of
> the air, even ionizing the air making it a blackbody absorber. Not to
>
> mention the mundane problems like clouds.
But the govt. and researchers have done research with lasers that have
disabled missles at a 7 mile range and destroyed them at ranges of 3
miles. And will have one mounted in a 747 that will destroy missles at
ranges of 250 miles. Appears they have soleved some of the problems or
worked around them.Additionally, they have been doing research on atom
lasers that do not have the problems of divergence.
> >> And I doubt you'd have a two foot peice of steel because you'd
> have to move that >> two-foot thick armor with you wherever you go.
> >Army tanks.
> If I was the guy in the tank and someone was trying to burn his way in
>
> with a laser, the smoke dispensers would already have discharged.
Disable the tracks and the sensors, then they are sitting ducks. And
when did smoke prevent laser tarketing systems from working. They
don't, and surely wouldn't have any or at most negligible effect on a
laser in the megawatt range.
> They're supposed to obscure laser targeting systems, but they'd work
> fine
> against laser weapons, too.
Laser targeting systems are not in the megawatt range like the laser
weapons.
> When I run out of smoke, I'd shoot him. Or just ignore him. It's not
> like he's going to do anything to a tank with any laser he can carry,
> or pack in a truck,
Wrong. Artlicles on the research of lasers statethat the govt will
have lasers that can destroy missles at a 3 mile range on a truck making
them highly mobile. Not hand held by any means.
> >> Weight is a bad thing in a spaceship. Besides, they'd probably
> use a composite >> armor like the Chobam armor that the Abrams tank
> has. A 30mm gatling gun firing >> depleted uranium bullets at 6000
> rounds per minute would get through the armor a >> hell of a lot
> quicker.
> >Yes, it would, but if traveling at extremely high velocities in
> space,
> >then the bullet would take time to get to the ship. Enough time to
> make
> >the bullet miss,
> What kind of spaceship are you driving? A 20mm gatling gun is part of
> the
> Phalanx system that (among other things) protects U.S. warships. It
> can
> shoot down planes a mile away that can pull 8 G's. You're not going
> to do
> better than that without passing out, the pilots only do that with
> training, conditioning, and a flight suit.
And you ommitted the part about the weight of each of the bullets (over
a pound) so it would take over 3 tons of ammo to fire for only 1 minute
and that is only 1 gun and it is also too big for a single person to
carry also.
> If it was merely velocity that you're worried about, compensating for
> that is an old trick. The Abrams tank does that, plus accounting for
> air density, wind speed, range, and barrel warpage.
Except if you are directly behind the running vessel. More like a dog
fight with jets, not slow tanks.
> >unlike a laser that would get there almost instantly.
> And do what? Make a puff of smoke on the hull? That's the primary
> finding in my calculations, that lasers are just too darn weak to be
> used
> as a weapon.
Then do recalculations. And do some research, because you are wrong.
> >And how much does each one of the 30mm bullets weight...over a
> >pound maybe two. So 6000 rounds would be 3-6 tons for 60 second for
> >weapons fire. Additionally, the barrel would melt before it could
> fire
> >60 seconds. Seeing how you would want more than one forward mounted
> >gun, then you would have to have even more ammo. Considering you
> would
> >probably want at least enough ammo for 2 minutes of battle, and
>
> Firstly, it wouldn't take two minutes worth of firing to shred a
> spaceship. Secondly, that was a fer instance. You could mount a
> .50-cal machine gun if you want. You could install a coil gun or a
> rail gun. The best performance I know of for a rail gun is shooting a
> 4 pound projectile 14 miles per second,
4 pounds per round. In a dog fight (or chase) traveling at 3 million
fps a bullet traveling a 4 miles per second (21,120 fps) would take
142.05 seconds to reach the target. Enough time for the ship in being
chased to move out of the way. If a laser was used instead of the
bullet, it would give the ship only 0.00305 seconds to move out of the
way. Big difference.
> and an idea I've seen for application is to shoot plastic pellets out
> of a rail gun because they're light and minimize recoil but still
> carry all the energy to the target.
It doesn't matter what you shoot, it is too slow.
> You could install pretty much any conventional weapon and it would be
> more effective
> than any laser you'll be able to find.
That you can find. I have already disproved this with published
articles. New Scientist in the Oct 26, 1996 issues states that lasers
will be common placed weapons on the battle field over the next 30
years. But what does the govt know.<grin> In the year 2000, the US Air
Force will put a laser on a Boeing 747 that will destroy a Scud-type
missle at ranges of 250 miles. Reference, Popular Science Nov 1996 in
an article called the BIG ZAPPER.
> >Sorry about that, I didn't get the first post...either it was posted
> to
> >another group first, or my sorting dropped it. But the way to shield
>
> >against lasers is to disperse the beam to a level that is not
> harmful.
> Smoke, water vapor, mirrored surfaces, ablative armor. Turns out,
> though,
> with a terajoule laser pulse penetrating about .00004 centimeters of
> iron,
> there's no reason to bother. The lasers in the SDI program were
> pulsed
> lasers, with time between each pulse for the metal vapor to clear.
Old news. The SDI project was at least a decade ago.
> Hmm, I think you misunderstand. A gyrojet is a weapon developed some
> time ago. It's a rocket-propelled bullet. It has four nozzles that
> are angled to spin-stablize the bullet. It has very little recoil,
> and it also needs about ten feet before it can get up to lethal
> speeds. It never caught on for various reasons including cost and the
> fact that it really didn't improve on the .45 auto or the traditional
> combat rifle.
I understood perfectly. Iit was not a gyro that prevented the kickback
of firing a weapon as stated (in a misleading way). It is a rocket that
had little or no recoil. Rockets are not bullets. That was my point.
> >> How big is the nuclear power plant and the cooling system for your
> laser?
> >It could be smaller because you would be able to use the coldness of
> >space to cool the laser.
>
> Depends on how the laser is constructed. You may have to cool
> internal parts that can't be exposed to the vacuum, or you might need
> a water jacket or something if the heat can't flow from inside to
> outside quickly enough.
A laser can use chemical means which do not require cooling also. And
recently, a laser was constructed that will operate in a 147 degree F
room. No cooling required.
> >Nuclear power is very inefficient. A nuclear power plant is a big
> steam turbine. It >uses nuclear power to heat water to create steam
> to turn a turbine to generate >electricity. A coal generating plant
> does the same thing, but it uses coal as the heat
> >source instead of nuclear power. The actual power generation is the
> same.
>
> A nuclear power plant is as efficient as any other steam engine. But
> it
> has the highest energy density we can control, that's why so many
> submarines and aircraft carriers use them.
You agree with me then.
> >Some of the biggest guns are big. 18 inch guns require an entire
> ship
> >to carry them.
> But the difference is the 16 inch guns can put a slug through several
> feet
> of steel, or make a crater fifty feet wide. (I think only the Yamato
> had
> 18 inch guns, and that was sunk during WWII.) And they can keep on
> firing
> without needing twice the ship's weight in power plant.
No, but it needs twice the ships weight in shells and explosives that
will eventually be used up. And how much does the actual gun weight ?
Several tons. How much does each 16" shell weight...at least 50 or
maybe 100 pounds if not more. And the recoil in space would be
tremendous.
> >I agree that current lasers are not a good weapon, but I don't
> believe modern bullets
> >and weapons would be effective in space once we are able to move
> >confidently (meaning like driving a car).
>
> Depends on what you mean by "move confidently".
Meaning we have spacecraft that we drive in space like we drive cars on
Earth.
> Modern bullets and weapons can shoot down airplanes that can turn so
> fast the pilot blacks out.
Vehicles that would allow confident space travel (see above) would be
too fast for current weapons. They would travel faster than the speed
of the bullet and be maneuverable and safe, otherwise people would not
have confidence in them.
> >We can't, but you could carry a laser with slightly more power than a
>
> >laser aiming device and blind the enemy from a very long distance.
> That
> >could be hand held.
> That is an option being explored by the military. It may have been
> rejected for ethical reasons, I'm not sure. (Strangely enough,
> intentionally maiming a soldier for life is considered unethical, but
> killing him outright isn't.)
Actually, they are working on banning that use of a laser.
> >A bigger weapon the size of a chain machine gun
> >which has a portable generator could be somewhat effective (it could
> be
> >used instead of a flame thrower to start fires in a camp , or explode
>
> >fuel and weapons depos, and at much greater distances).
> I don't know the status of any research like that. But I think you'd
> need some compelling reasons to use a laser instead of a mortar with
> incendiary shells.
You could shoot the laser from inside a bunker, unlike a mortar.
<snipped>
Your previous arguements I again refer to the articles mentioned above.
> No, the turbines on a jet couldn't produce enough energy to power a
> laser that would accidently destroy something 100 miles away in less
> than a fraction of a second.
A 25,000 hp turbine can produce enough electricity to power a city. A
laser takes less energy.
> Nobody on earth has the technology to make the scenario you described.
Read the articles because the US Air Force is about to get a fleet of
them within the next 5 years.
Timeout
Isaac Kuo wrote:
> >But when you are on a five year mission like the TOS then you will
> >probably run out of ammo unless you get resupplied.
> As for ammunition, I think you could count the number of times the
> old Enterprise fired its phasers on your fingers in those 5 years.
> They weren't on a military campaign.
But what about TNG and DS9, much phaser fire there which would
completely use the bullet supply. And they weren't on a military mission
either.
> Actually, the SR71 couldn't be taken down with earlier weapons
> because of its high altitude. The high speed was necessary to
> fly so high up in the rarefied atmosphere.
I refer you to the Nov 1996 issue of Popular Science the "Big zapper"
article. It is capable of shooting down missles at a range of 250
miles. The Air Force in the ABL (Airborne Laser) project will have
modified 747's armed with the lasers within 5 years.
> >Nuclear power is very inefficient.
>
> Compared to what?
Compared to solar panels that convert directly to energy. A one step
process, unlike nuclear power that require the heating of water to make
steam to turn a turbine that makes electricity.
> >A nuclear power plant is a big steam turbine.
>
> Not necessarily.
Yes necessarily. That is the way nuclear power plants work. The
nuclear part is used to heat water to create steam. That is all the
nuclear part does.
> In most terrestrial applications, a steam
> turbine is used because it is very _efficient_.
And in what application is nuclear energy used to create electricity
directly. It isn't. Nuclear creates less airborn pollution than other
fuel sources, that is why nuclear is used.
> However,turbines are relatively high maintanaince and somewhat heavy
> compared to the alternatives.
What alternatives?Hydro dams use turbines.
Nuclear power plants use turbines.
Coal power plants use turbines.
Fuel power plants use turbines.
The turbine spins a shaft connected to a generator.
Wind power us basically the same thing...the propellers are the turbine
blades.
What alternatives are you talking about ?
> In space applications, especially unmanned, low maintanaince
> low mass systems are desirable.
Are you talking about solar cells, or liquid oxygen. In space they use
batteries for power and solar panels to help maintain the battery
charge. Which support my first statement about nuclear power being
innefficient.
Timeout
Gregory Loren Hansen wrote:
<snipped>
> Depends on what you're going to use it for. It's a lot easier to
> destroy
> a SCUD than many other targets.
But you do see that lasers are weapons.
I had to use sources to convince people that lasers aren't just wimppy
weapons. They are real weapons. All weapons have a particular area it
is designed for...currently, lasers are to be used as defensive weapons
agains missle attacks. Not offensive. Enjoy the reading.
Gregory Loren Hansen
I found the article Timeout referenced. "TRW Laser Destroys Russian
Rockets" in _Aviation Week & Space Technology_, March 25, 1996, page 58.
They used a prototype laser to destroy two Russian-designed artillery
rockets at White Sands Missile Range, N.M. The system seems to have the
precision to hold a two foot wide laser beam at the head of a rocket for a
long enough time to burn through the casing and hit the explosives. The
article has a picture of a missile in profile with a spot at the nose, so
it was a moving target, too. Definitely very cool. But there's a few
things to keep in mind.
1) It doesn't exist. What was tested is a prototype. It still requires
several hundred million dollars for research and development, and about
two years, to turn it into a weapons system. Nobody seemed willing to
pick up the tab.
2) It's short range. According to the article, if a missile is fired at
20 miles the laser can disable its sensor at 12 miles (it takes eight
miles to acquire the target?). If the target is an unguided missile it
can be destroyed at 3 miles. Targets envisioned inlude terrain-hugging
cruise missiles, anti-radiation missiles, unmanned aerial vehicles, and
attack helicopters. No mention manned fighter planes. Uses include
defending a town from terrorists' rockets or destroying missiles that leak
through the long-range defense systems, or batteries of four to six to
defend troop concentrations. It looks like it won't be destroying targets
at 250 miles or accidently killing civillians a thousand miles away. No
mention of its performance in inclement weather or smoke, except that the
prototype was operated at less than full power to simulate a tactical
weapon.
3) The article says the laser burned through a "heavy steel casing" in
"only a few seconds". But how heavy is "heavy"? Half-inch of steel?
1/8 inch? How long is "a few seconds"? Two seconds? Twenty? TRW isn't
giving out details.
4) It's a megawatt-class deuterium fluoride "MidInfrared Advanced
Chemical Laser". I mentioned earlier maybe there's a trade-off between
skin depth and the energy that reflects from the target, and midinfrared
may be the optimum. Or it could have the best transmission through smoke
and dust, or else it was just the best they can do with the technology
they had. The article doesn't say. Also it's chemically-pumped, not
electrical, so it still uses up ammo. Thousands of dollars worth per
shot. They think it could be installed in a Bradley Fighting Vehicle with
ammo to destroy fifty missiles, the fighting vehicles could be deployed
near threatened towns or forward fighting areas.
I also wondered about adding a laser vehicle to a typical armored or
mechanized platoon. It could tag along behind the tanks and APCs to
destroy missiles fired by yahoos in the bushes at the vulnerable flanks
and rear of the armor, or protect them from bombardment by artillery. Or
it also might have anti-personell uses. It only has fifty shots, but if
each shot is "a few seconds" long I wonder how useful that would be in
sweeping the underbrush.
5) Why a laser? It eliminates development costs of a missile seeker,
engine, and missile design. But I know mortar shells exist that can seek
and destroy metal targets. I wonder if sensor and guidance technology
could be put into something the size of a mortar or grenade to give a much
higher ammunition density than fifty shots from an armored vehicle.
Imagine an automatic grenade launcher firing miniature Patriot-style
projectiles. Or even a radar-controlled minigun, like a miniature Phalanx
system. But that's a sheer flight of fancy on my part.
6) The designers believe it could intercept and destroy falling bombs,
but that concept is not being developed. I think that's a good idea, but
I suppose I wouldn't develop it, either, considering NATO forces always
seem to have air superiority when they go to war.
Overall it destroys unprotected moving targets at short range, it still
needs work, but it's very cool.
Brian Trosko
Timeout <isa...@mycomputer.com> wrote:
: Like that atom laser that doesn't suffer from beam disfusion.
All lasers suffer from diffraction. It's a function of lens diameter and
distance. There's no way around it, short of a complete rewrite of the
laws of physics.
: > the possibilities are endless, but the doctrine for hitting hardened
: > bunkers has been pretty well worked out.
: Again, you support my side because a laser would do better than bullets.
I don't see how. How's a laser going to destroy a hardened bunker?
: But the govt. and researchers have done research with lasers that have
: disabled missles at a 7 mile range and destroyed them at ranges of 3
: miles. And will have one mounted in a 747 that will destroy missles at
: ranges of 250 miles. Appears they have soleved some of the problems or
: worked around them.
You *do* know why it's carried on a 747, right? Reason number one, it's a
*big* laser. The second reason is to get the beam above most of the
atmosphere, so that it will actually *work*. So, it's too big to put on a
land-based mobile platform, and even if you did, there's too much air down
there for the laser to do anything but make a pretty lightshow as it
wastes 90% of its energy ionizing a path through the atmosphere.
You *do* know what sort of laser it is, right? It's a COIL, which stands
for Chemical Oxygen-Iodine Laser. In other words, it's chemically pumped,
and uses a chemical reaction between atomic oxygen and iodine to generate
the energy for the beam. Oxygen and iodine are both somewhat...reactive.
You've got to be very careful storing, transporting, and transferring
them, unlike nice, safe, relatively inert nitrocellulose. *And*, the
products of that chemical reaction are also fairly toxic, so you've got
to deal with those, too.
And for all that, this 747 based megadeath laser system you're touting
carried enough reactants on board for a total of 8 shots. If everything
works, it'll destroy 8 missiles before it has to land and refuel, which
takes quite a while.
By contrast, a modern Arleigh Burke-class guided missile destroyer can
carry upwards of 96 SM2s. That's 96 missiles it can shoot down.
But the laser's cooler, so to you, it's better.
: Additionally, they have been doing research on atom
: lasers that do not have the problems of divergence.
Bullshit. Gimme a reference.
: Disable the tracks and the sensors, then they are sitting ducks. And
: when did smoke prevent laser tarketing systems from working.
Targeting lasers are low power infrared lasers. Smoke poppers on modern
battle tanks pop smoke that are opaque to infrared. With the prevalence
of thermographic sights, why would we even bother to mount smoke grenades
on the things if everyone and their sister could just switch over to
infrared and see the tank through the smoke?
: They
: don't, and surely wouldn't have any or at most negligible effect on a
: laser in the megawatt range.
The *atmosphere* is going to have an extremely detrimental effect on a
laser in the megawatt range.
: Laser targeting systems are not in the megawatt range like the laser
: weapons.
There are no laser weapons intended for use against ground targets.
: Wrong. Artlicles on the research of lasers statethat the govt will
: have lasers that can destroy missles at a 3 mile range on a truck making
: them highly mobile.
"Will have." As in, "Eventually." No such programs are even as far along
as that 747 you were talking about, and that's still several years from
deployment, if it ever gets finished.
And a missile isn't armored by the equivalent of 1200mm of rolled
homogenous steel. Tanks are. Modern tanks also are armoed with ceramic
composites that are easily able to handle the tremendous pressures and
temperatures associated with the impact of a HEAT warhead; a laser would
be pie compared to that.
: And you ommitted the part about the weight of each of the bullets (over
And you're consistently omitting the part about the weight of the
reactants necessary to generate the beam. We're *decades* away from being
able to squeeze and electrically-pumped multimegawatt laser into a 747.
Seen NOVA? It's several *acres*.
: Then do recalculations. And do some research, because you are wrong.
You sound like you've already done the calculations. Have you? Why not
provide them?
: It doesn't matter what you shoot, it is too slow.
Light's pretty slow, all things considered. Let's say you're in earth
orbit, and your target's out by Mars. When you fire, he's got plenty of
time to get out of the way.
: missle at ranges of 250 miles. Reference, Popular Science Nov 1996 in
: an article called the BIG ZAPPER.
Try Aviation Week & Space Technology. I won't denigrate Popular Science
other than to say that it often gets too caught up in the "Gee Whiz"
factor to actually discuss real limitations.
: Old news. The SDI project was at least a decade ago.
But any weapon laser is *still* going to be pulsed.
: I understood perfectly. Iit was not a gyro that prevented the kickback
: of firing a weapon as stated (in a misleading way). It is a rocket that
: had little or no recoil. Rockets are not bullets. That was my point.
A bullet is something that comes out of the barrel of a gun. The gyroget
gun was a *gun*. The gyrojet projectiles were *bullets*.
: A laser can use chemical means which do not require cooling also.
I'm not aware of any chemical lasers that don't rely on exothermic
reactions. Can you name one?
: And
: recently, a laser was constructed that will operate in a 147 degree F
: room. No cooling required.
I've got a laser that operates in an 80 degree room; it's in my CD player.
Doesn't mean I can use it to shoot down missiles at a range of 250 miles.
: > Depends on what you mean by "move confidently".
: Meaning we have spacecraft that we drive in space like we drive cars on
: Earth.
Oh, you're talking about the *movies*. I'm sorry; I thought we were
discussing reality, and not a Star Trek episode.
: too fast for current weapons. They would travel faster than the speed
: of the bullet and be maneuverable and safe, otherwise people would not
: have confidence in them.
The only way you're going to have a spacecraft pull more than 9gs for any
appreciable length of time and *not* have everyone on board black out is
to use those magical Inertial Dampeners(tm).
: You could shoot the laser from inside a bunker, unlike a mortar.
And a mortar can be used for indirect fire, unlike a laser. A mortar
shell can kill everyone within 15 meters of the impact point, and wound
everyone out to 30, unlike a laser.
: A 25,000 hp turbine can produce enough electricity to power a city.
What are you smoking? The M-1 has 1,500hp gas-powered turbine. 20 M-1s
could power a city? Which one?
: > Nobody on earth has the technology to make the scenario you described.
: Read the articles because the US Air Force is about to get a fleet of
: them within the next 5 years.
I have read the articles. Not the ones in Popular Science, but I suggest
you're overly optimistic.
Brian "Reroute the plasma flux through the alluvial dampers before the
tetrion particles damage Stellar Cartography, my *ass*" Trosko
John D. Gwinner
Timeout <isa...@mycomputer.com> wrote in article
<33DA3BE4...@mycomputer.com>...
> > >Nuclear power is very inefficient.
> >
> > Compared to what?
>
> Compared to solar panels that convert directly to energy. A one step
> process, unlike nuclear power that require the heating of water to make
> steam to turn a turbine that makes electricity.
It may be one step, but compare the efficiencies of that step. I think
you'll be surprised. Using the same logic, plants can walk faster than
humans, because they get their food in one step, instead of having to kill
it, eat it, and digest it.
> Are you talking about solar cells, or liquid oxygen. In space they use
> batteries for power and solar panels to help maintain the battery
> charge. Which support my first statement about nuclear power being
> innefficient.
Quote some numbers.
== John ==
William Baird
In article <5rdm1u$8gh$1...@dismay.ucs.indiana.edu>,
Gregory Loren Hansen <glha...@copper.ucs.indiana.edu> wrote:
>
>I found the article Timeout referenced. "TRW Laser Destroys Russian
>Rockets" in _Aviation Week & Space Technology_, March 25, 1996, page 58.
>They used a prototype laser to destroy two Russian-designed artillery
>rockets at White Sands Missile Range, N.M. The system seems to have the
>precision to hold a two foot wide laser beam at the head of a rocket for a
>long enough time to burn through the casing and hit the explosives. The
>article has a picture of a missile in profile with a spot at the nose, so
>it was a moving target, too. Definitely very cool. But there's a few
>things to keep in mind.
>
>1) It doesn't exist. What was tested is a prototype. It still requires
>several hundred million dollars for research and development, and about
>two years, to turn it into a weapons system. Nobody seemed willing to
>pick up the tab.
Being further worked on. IIRC, it's called Nautilus and is being jointly
funded by the US and Isreal after the Katyusha attacks in northern Isreal.
Tehre are other laser systems that have been developed/are being
developed. The ABL/YAL-1 (Airborne Laser) is another. It's intended to
shoot down ballistic missiles in the boost phase. It uses a
<blank>-iodine laser inside a Boeing 747 airframe. re:
http://www.boeing.com/airborne.laser/AirborneLaser.html. Also of interest
would be the http://www.trw.com/seg/sats/THEL.html TRW site. They also
worked on MIRACL at White Sands, which, supposedly can blind sats/kill.
The ABL is supposedly capable of sat kills as well.
>Overall it destroys unprotected moving targets at short range, it still
>needs work, but it's very cool.
Yah...:) Warfare is getting into the SF...we'll have to see what SF comes
up with in response.
Will
--
Will Baird email: wba...@acca.nmsu.edu http://essex.nmsu.edu/~scomputi/
Phantoms! Whenever I think I fully understand mankind's purpose on earth...
suddenly I see phantoms dancing in the shadows...[saying] pointly as words,
"What you know is nothing little man; what you have to learn, immense." - CD
Uncle Al
Gregory Loren Hansen wrote:
>
> I found the article Timeout referenced. "TRW Laser Destroys Russian
> Rockets" in _Aviation Week & Space Technology_, March 25, 1996, page 58.
> They used a prototype laser to destroy two Russian-designed artillery
> rockets at White Sands Missile Range, N.M. The system seems to have the
> precision to hold a two foot wide laser beam at the head of a rocket for a
> long enough time to burn through the casing and hit the explosives. The
> article has a picture of a missile in profile with a spot at the nose, so
> it was a moving target, too. Definitely very cool. But there's a few
> things to keep in mind.
[snip]
> 4) It's a megawatt-class deuterium fluoride "MidInfrared Advanced
> Chemical Laser".
Wouldn't it be more effective - and cheaper - to load a few B-52s with dollar
bills to simulate the belligerents as Welfare recipients, new NATO members, or
inverse vistors to the Clinton White House Lincoln bedroom? Uncle Al suggests a
low altitude air burst.
Has somebody called the EPA about the, ah, effluent?
--
Alan "Uncle Al" Schwartz
Uncl...@ix.netcom.com ("zero" before @)
unc...@uvic.ca (to 30 July, cAsE-sensitive!)
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Robert R. Tucci
In article <5rdm1u$8gh$1...@dismay.ucs.indiana.edu>,
glha...@copper.ucs.indiana.edu (Gregory Loren Hansen) wrote:
> I found the article Timeout referenced. "TRW Laser Destroys Russian
> Rockets" in _Aviation Week & Space Technology_, March 25, 1996, page 58.
> Blah Blah Blah
> Overall it destroys unprotected moving targets at short range, it still
> needs work, but it's very cool.
Yeah, real cool.
Was the missile painted black by any chance? Cause my missiles would be
chromium plated.
Bob Tucci
Isaac Kuo
>> >> constant,
>> >> like c. If you fire a bullet (travelling 30 000 fps) out of a ship
>> >> (travelling 3 000 000 fps), you now have a bullet travelling 3 030
>> 000
>> >> fps, which is faster than the ship.
>> This is true...
>Not entirely...if you are traveling at 99% the speed of light and shoot
>a projectile at 10% the speed of light, it does not exceed the speed of
>light.
So? 3,000,000 fps is nowhere near 99% of the speed of light.
Of course, if you were moving at 99% the speed of light and shoot
a projectile in the same direction at 10% the speed of light,
it will indeed be moving faster than you.
>> >In space, there is space dust which would
>> >completely destroy the unprotected bullet quickly.
>> No there isn't. Not at these speeds, by any stretch of the
>> imagination.
>There is plenty of space junk around the Earth, and some of the junk has
>left the confines of earth. And none of the asteroid leave any debris
>behind either do they. Lots of debris in space.
Yes, there's plenty of space junk around Earth. No, it would not
destroy an unprotected bullet quickly. You're simply wrong.
>> >The gravitational
>> >pull on bigger objects would deviate the bullets path, although
>> slightly
>> >over a couple of hundred yards, dramatically over 100's of miles.
>> Gravitational pull is something which can be calculated and accounted
>> for. Every gunnery fire control system in the world from .22 rifle
>> open sights to Iowa class battleship fire control necessarily takes
>> it into account to some extent. With repeated salvos, an Iowa can
>> literally put a shell right on top of a target 40 miles away, even
>> with the much greater variabilities of wind.
>Granted it is easy on earth where you have almost all the variable
>factors, but in space, you would have to calculate the gravitational
>pull of all objects in the area.
No you don't, any more than you have to calculate the gravitational
pull of all the objects in the area when shooting a gun on Earth.
Advanced fire control takes into account Earth's oblateness and
rotation, but doesn't bother taking into account nearby mountain
ranges. Why? Because the force of gravity from a mountain range
is insignificant.
In practice, given the capabilities of _today's_ computers, the
only reason we don't calculate the effects of all the other planets
is that their effect is insignificant.
Try plugging in some real numbers.
>Another ship, another planet,
>everything. These calculations would have to be done on a continuous
>basis making minor adjustments between each shot. And at 3,000,000 fps
>(2,045,455 mph) That is about half way from Earth to Mars in one hour to
>give a real comparison.
Actually, at closest approach, Mars is about 75,000,000 km away
from Earth. That's over 20 hours at 3,000,000 fps, so you're
off by an order of magnitude.
All of which is irrelevant to how difficult the calculations are.
The speed of the firing vessel and the target doesn't really
have an effect on the difficulty of the calculations.
>> >Going
>> >back to your example of 3,000,000 fps and 30,000 fps, the projectile
>> is
>> >only 1 percent of the ships speed. If both ships were traveling at
>> >3,000,000 fps and were one second apart then the bullet would take 10
>> >seconds to reach the ship in front (assuming that the bullet didn't
>> get
>> >destroyed first).
>> Why assume they are 3,000,000 feet apart, moving in the same direction
>> and speed? These two ships aren't interested in engaging each other?
>> My, how peaceful!
>No, it is a dogfight situation like in SW. Pretty peaceful I must
>admit.
SW as in Star Wars? Those situations are extremely fanciful, and
don't even vaguely represent a plausible situation in space combat.
Of course, this is because they based the motion of their fighters
on WWII aerial fighter footage.
Realistic space maneuvers are entirely different from what you see
in Star Wars or Trek, or even most of Babylon 5. In a situation
with vehicles having high thrust delta-v capabilities greatly
outweighing projectile delta-v capabilities (which is what we're
discussing here), maneuvers become a close range ballet where
both sides maneuver into an intercept course, fire salvos, and
then attempt to avoid the opposing salvos.
The "distance" one would fire salvos at would depend upon how
much time the target needs to avoid the salvos. Ideally,
a salvo is fired when the intercept course would imply a
collision in less time than that.
>> A more aggressive situation is that they are "1 second apart",
>> meaning that they are on an intercept course and will hit each
>> other 1 second from now (if neither ship maneuvers). Any
>> bullets fired will intercept the target slightly sooner than
>> 1 second from now.
>That is a different scenario which would probably destroy both ships.
Combat in the real world is sometimes like that. In a modern
aerial dogfight where both fighters have detected each other,
each fighter has two options: 1) Turn toward the enemy and
take a shot, or 2) Turn away from the enemy and get shot.
Both pilots naturally pick option 1, and unless
ECM/countermeasures foil one side's missiles, the result is
two planes destroyed.
>> >10 seconds is plenty of time to react because the
>> >ship would only have to alter the course only slightly.
>> You simply don't understand the maneuvering works in space if
>> you think in terms of "altering course". In space, there is
>> no atmosphere or ocean or road to push wings or hulls or wheels
>> against. You can't just alter your course by rotating your
>> vessel. You have to use rockets or external means to accelerate
>> to change course.
>If a ship can travel 3,000,000 fps (which the space shuttle travels at
>35,200fps for comparison) then altering the course would be easily
>accomplished. The thrusters would be superior, everything would be
>superior.
Wrong. If a ship can travel at 3,000,000 fps, that simply means
that it has a high delta-v capability. Since you apparently
don't already know it, high delta-v rockets tend to be low
thrust, even the really high power rockets.
High thrust and high Isp don't mix. The sort of rockets which
could reach 1000km/s with reasonable propellant/payload ratios
would be very low thrust (but high power) anti-matter or fusion
powered rockets.
>> At any rate, this is more true today than it would be in space,
>> because today's soldiers and weapons fight at ranges where the
>> time delay for lasers is practically zero. In contrast to lasers,
>> missiles can take _minutes_ to reach their targets, today.
>> However, despite this obvious advantage lasers have, they aren't
>> used directly as weapons today. Puzzling, isn't it? (sarcasm)
>Actually, it is not puzzling. A laser can travel 186,000 miles per
>second. If you do miss you target, there is no fail safe. There is no
>self-destruct like on a missle.
This is just stupid. There is no self destruct on most missiles,
and there's certainly no self destruct on a bullet.
>The is no limited range like with bullets.
And this is even more stupid. First off, here on Earth, which
is curved, artillery shells actually have _more_ range than a
ground or ship based laser could have.
Secondly, lasers do have a limited range, beyond the obvious one
dictated by the horizon. There are lots of problems trying to
get high power lasers to get through the atmosphere.
>This could be a scenario if they used lasers as offensive
>weapons. You shoot at a hostile jet on the horizon, for some reason you
>miss, and 3,000 miles away an international commuter plane is
>destroyed. That is a reason for not using lasers as offensive weapons.
No it isn't.
>> >To destroy the bullet, all the ship in front would have to do is
>> >list out salt or dust.
>> Easier said than done. The salt/dust would drift alongside the
>> ship. There's no such thing as the "ship in front".
>Not if you place the dust or salt in a persurized compartment. The
>decompression would cause the salt/dust to be blown away from the ship.
Not very fast and thus not very far in the amount of time involved.
You'd be lucky to get 50m/s out of the power from compressed gas.
A cloud of dust 500m or so from the ship isn't going to protect
it from anything (other than a laser, perhaps, since they don't
have much penetration capability).
>> We have the concept of destroying incoming projectiles today;
>> it's called CIWS. Some of the better systems do a marvelous
>> job of chewing up an incoming missile--into lots of bits of
>> debris which still hit and severely damage the target ship
>> (but hey, it would have been a lot worse if the missile hit
>> intact, and thus detonated its warhead within the ship).
>Researches have successfully used lasers to destroy incoming missles. I
>have referenced them before.
There is no sign of any such lasers being fielded by any military.
The USAF's research 747 laser is really quite laughable. After
the initial embarassing tests where the laser failed in front of
the brass and the press, they learned to _not_ announce test
firings beforehand. It's the only laser I've ever heard of which
has even come close to destroying a flying target, but it took
them so long to rig up a situation where it could do so, it only
barely qualifies as a success.
Nyrath the nearly wise
Thus spoke Timeout (isa...@mycomputer.com):
> But not before you run out of ammo. And if you have a way of refueling,
> like the E-D does while in flight, then you don't have that problem.
Oh, we're talking Star Trek, are we? (I'm reading this
in rec.arts.sf.science).
In that case, your replicators can make just as many bullets
as the ship can make phaser bolts. So you won't run out of *either*.
> A physical bullet would have no effect other than making a sound. BTW,
> the govt is to have a laser mounted in a 747 that will be capable of
> shooting down a SCUD sided missle at 250 miles.
> I think that is enough evidence.
Oh, come now. A SCUD is a flying tinfoil can. If it had any
armor on it, it wouldn't get off the ground.
> > The MPC Gyrojet was a prototype military
> > sidearm produced several decades ago. It actually shot rocket
> > bullets. Practially no recoil.
>
> The main word is "rocket" bullet. It is not "just" a bullet.
*sigh* The discussion is on the relative merits of energy
weapons vs projectile weapons. No, a gyrojet round is not
"just" a bullet, but it is of similar complexity, and does
its damage in exactly the same way. The only difference
is the lack of recoil
> > The firing mechanism was so simple
> > that it was almost jam-proof.
>
> What was the result when the bullet did jam. Probably did a lot more
> damage than a regular bullet to the shooter.
Naw, it would just blow the hammer off. The gyrojet looked
like a toy, since the body was little more than pressed metal.
The *barrel* on the other hand, was an exotic alloy, to
handle the rocket.
The hammer was in front of the trigger finger, instead of
in the back like most weapons.
> > > Like phasers.
> >
> > Or like cybernetic voodoo dolls of the enemy ship you
> > stick with electronic pins to kill it.
>
> Never saw that in ST before. Which episode was that ? <grin>
>
> > "Phaser" is a null-content word. Speculation about them is
> > futile, since the only thing we know about them is that they
> > look like a pretty teal beam and they make things vaporize.
>
> I find phasers applicable in the ST: tech newsgroup, maybe your post is
> inappropriate. <grinning back at you>
Like I said, I'm reading this in rec.arts.sf.science.
You should trim the newsgroups, removing that and sci.physics.
Like I said, the problem with speculating about phasers is
the lack of data. Not only has there been no explaination
of their operating principle, but they don't even act
constently from episode to episode.
A person hit is somehow selectively vaporized, with his
cloths evaporating with him but not the chair he was sitting
in. Or the floor.
Not to mention the fact that it would take the energy of
a tactical nuclear detonation to generate enough energy to
poof somebody like that. Or if it was some kind of matter
consuming chain reaction, not only would it generate enough
heat and radiation to slag the entire room, but it would
have no particular reason to stop with the person and
his clothes.
* A B S I T * I N V I D I A * V E R B O ** I D E M * S O N A N S *
+----------------------------------------------------------------------------+
| WINCHELL CHUNG http://www.clark.net/pub/nyrath/home.html |
| Nyrath the nearly wise nyr...@clark.net |
+---_---+---------------------[ SURREAL SAGE SEZ: ]--------------------------+
| /_\ | F = ma, and all the rest is magic |
| <(*)> | |
|/_/|\_\| |
| //|\\ | |
+///|\\\+--------------------------------------------------------------------+
Gregory Loren Hansen
In article <33DA3D56...@mycomputer.com>,
Oh yes, I agree that lasers can be weapons. (Sorry, I have to take issue
with that point. They *can* be real weapons with further development.)
I have some serious problems with a laser burning through two feet of
steel on a tank before the tank crew does something about it. But like
you said, the weapon must fit the job.
I'm sure I will enjoy the reading. Thanks. Do you have any more to
recommend?
Gregory Loren Hansen
In article <tucci-26079...@204.215.129.54>,
I don't know! The picture was kind of vague, like an object against a
brighter sky.
The article didn't mention ways to defend the missiles.
Gregory Loren Hansen
In article <33DA3777...@mycomputer.com>,
Timeout <isa...@mycomputer.com> wrote:
>Gregory Loren Hansen wrote:
>
>> >But when you are on a five year mission like the TOS then you will
>> >probably run out of ammo unless you get resupplied.
>>
>> We're not. If we were on a five year mission we'd have something
>> better
>> than lasers to shoot things with.
>
>Like that atom laser that doesn't suffer from beam disfusion.
Atom laser?
>But the laser would be better than bullets. That is my point which you
>just supported.
I did?
>> >Machine guns are still useless against hardened bunkers. At some
>> point
>> >the bullet will not penetrate because you just can't get enough force
>>
>> >into the bullet to penetrate.
>>
>> Well, if you're trying to destroy a hardened bunker, I'd suggest a
>> LAW,
>> AT-4, a flamethrower and a few guys with grenades, a tank,
>> artillery...
>> the possibilities are endless, but the doctrine for hitting hardened
>> bunkers has been pretty well worked out.
>
>Again, you support my side because a laser would do better than bullets.
But a laser wouldn't do squat against a bunker. It wouldn't do anything
at all.
Turns out (I just read this) a 30mm gun can turn a bunker into a pile of
sand pretty quickly.
>> On the other hand, if I was in that hardened bunker and some guy with
>> a
>> laser was trying to burn his way in, I'd shoot him.
>
>Good luck since the laser can do it at a 250 mile range.
No, it can't. Getting through a few tenths of an inch of steel in a
missile and getting through two feet of concrete are two entirely
different problems. Besides, you won't even be able to see my bunker at a
thousand yards. If you could, I'd worry more about artillery.
>The govt will
>have one in a Boing 747 in a few years that can shoot down a missle at
>250 a range of 250 miles, research has already proved missles can be
It would be interesting to see if that laser ever gets into service.
You're counting on a weapon that doesn't exist yet, and when it does exist
it will hit thinly armored non-maneuverable targets. That's useful, don't
get me wrong. But it won't replace a machine gun.
>completely destroyed at ranges over 3 miles by lasers, so again I say.
>Good luck at shooting the person aiming the weapon.
Three miles is considered short-range as far as missile defenses go.
>> For underground bunkers, it's hard to beat a large artillery barrel
>> packed
>> with high explosives, dropped from a great height by an airplane with
>> a
>> guidance system. It'll penetrate tens of feet of dirt before it
>> explodes.
>> The war will be over by the time a laser gets there.
>
>And again this is support for a laser and against bullets.
How is that? The laser would be ineffective.
>> Besides, I've been assuming we're using lasers in space. Using lasers
>> in
>> an atmosphere has its own problems, like divergence caused by heating
>> of
>> the air, even ionizing the air making it a blackbody absorber. Not to
>>
>> mention the mundane problems like clouds.
>
>But the govt. and researchers have done research with lasers that have
>disabled missles at a 7 mile range and destroyed them at ranges of 3
>miles. And will have one mounted in a 747 that will destroy missles at
>ranges of 250 miles. Appears they have soleved some of the problems or
>worked around them.
Yep, I read that article about the Nautilus laser. Very interesting.
Where did you read about the other one in the Boeing?
>Additionally, they have been doing research on atom
>lasers that do not have the problems of divergence.
I've never heard of those.
>> >> And I doubt you'd have a two foot peice of steel because you'd
>> have to move that >> two-foot thick armor with you wherever you go.
>> >Army tanks.
>> If I was the guy in the tank and someone was trying to burn his way in
>>
>> with a laser, the smoke dispensers would already have discharged.
>
>Disable the tracks and the sensors, then they are sitting ducks. And
Yeah, well, the tracks are a lot thicker than a missile casing. The
sensors are a good target. The crew still has eyes (the eyes might be
another good target).
>when did smoke prevent laser tarketing systems from working. They
>don't,
Tell that to the crew of an Abrams. Look at a picture of one, what do you
think those little tubes on the turret are? Those are smoke dispensors.
They fire automatically when the tank is painted with a laser. And the
driver also moves, trying to avoid anything that might be currently
unguided but still aimed at wherever they were.
>and surely wouldn't have any or at most negligible effect on a
>laser in the megawatt range.
Why do you think that? The laser would use up a lot of energy heating up
smoke particles.
>> When I run out of smoke, I'd shoot him. Or just ignore him. It's not
>> like he's going to do anything to a tank with any laser he can carry,
>> or pack in a truck,
>
>Wrong. Artlicles on the research of lasers statethat the govt will
>have lasers that can destroy missles at a 3 mile range on a truck making
>them highly mobile. Not hand held by any means.
The article I read said that the U.S. and Israel have not been
enthusiastic about funding a program that could lead to lasers on a truck
that can destroy missiles at a 3 mile range. With ammo for 50 shots. And
if you can hit the target, destroying a missile is a lot easier than
destroying a tank. A rifle can destroy a missile, if it hits. Iraqi
soldiers have managed to destroy a few Tomahawks by shooting them as they
careened down the streets. The advantage of the laser is in hitting the
target. But if all you want is firepower for ranges under a mile, you're
better off with a machine gun.
>> What kind of spaceship are you driving? A 20mm gatling gun is part of
>> the
>> Phalanx system that (among other things) protects U.S. warships. It
>> can
>> shoot down planes a mile away that can pull 8 G's. You're not going
>> to do
>> better than that without passing out, the pilots only do that with
>> training, conditioning, and a flight suit.
>
>And you ommitted the part about the weight of each of the bullets (over
>a pound) so it would take over 3 tons of ammo to fire for only 1 minute
>and that is only 1 gun and it is also too big for a single person to
>carry also.
Well, let's see, if it's ship-mounted a single person doesn't have to
carry it. The Phalanx doesn't need to fire for a full minute. You could
install something smaller like a minigun, something that shoots faster
projectiles like a rail gun. I was using the Phalanx as an example
because it's real and it exists, it's radar-guided and computer
controlled, it uses a feedback system to track targets, it shoots down
missiles and planes, and it's been proven effective. Amazingly effective.
So effective that it will destroy a missile and then start working on
individual fragments of a missile unless you turn the resolution down a
bit. These are all desireable qualities that can be used with any weapon
system.
You neglected to mention nobody is funding the Nautilus laser, or that
it's only got fifty shots.
>> If it was merely velocity that you're worried about, compensating for
>> that is an old trick. The Abrams tank does that, plus accounting for
>> air density, wind speed, range, and barrel warpage.
>
>Except if you are directly behind the running vessel. More like a dog
>fight with jets, not slow tanks.
If you're directly behind, then what's to correct? Just shoot straight
forward.
>> Firstly, it wouldn't take two minutes worth of firing to shred a
>> spaceship. Secondly, that was a fer instance. You could mount a
>> .50-cal machine gun if you want. You could install a coil gun or a
>> rail gun. The best performance I know of for a rail gun is shooting a
>> 4 pound projectile 14 miles per second,
>
>4 pounds per round.
Come on, did I say we'd be using 4 pound projectiles? This was research
for an Earth-to-orbit project, they wanted to put useful things into
space. Use a little imagination, try firing 1/4 pound projectiles and see
how fast they can go.
>In a dog fight (or chase) traveling at 3 million
>fps a bullet traveling a 4 miles per second (21,120 fps) would take
>142.05 seconds to reach the target. Enough time for the ship in being
>chased to move out of the way. If a laser was used instead of the
>bullet, it would give the ship only 0.00305 seconds to move out of the
>way. Big difference.
You're engaging a ship at a range of 568 miles? I wonder how effective
your laser would be, with beam divergence. Or the possibility of
reflective or ablative armor, laser-resistant armor, smoke. How long do
you have to keep the beam on the same spot before you burn through? The
Nautilus had to hold it there for "a few seconds" at a range of three
miles. I think I'd prefer a guided missile.
>> and an idea I've seen for application is to shoot plastic pellets out
>> of a rail gun because they're light and minimize recoil but still
>> carry all the energy to the target.
>
>It doesn't matter what you shoot, it is too slow.
That depends on the range, how quickly the target can move, when the
target can detect the fire, how well you can compensate for target
movement.
>> You could install pretty much any conventional weapon and it would be
>> more effective
>> than any laser you'll be able to find.
>
>That you can find. I have already disproved this with published
>articles. New Scientist in the Oct 26, 1996 issues states that lasers
>will be common placed weapons on the battle field over the next 30
>years. But what does the govt know.<grin> In the year 2000, the US Air
>Force will put a laser on a Boeing 747 that will destroy a Scud-type
>missle at ranges of 250 miles. Reference, Popular Science Nov 1996 in
>an article called the BIG ZAPPER.
I'll look those up. I liked the Aviation Week article.
>> Hmm, I think you misunderstand. A gyrojet is a weapon developed some
>> time ago. It's a rocket-propelled bullet. It has four nozzles that
>> are angled to spin-stablize the bullet. It has very little recoil,
>> and it also needs about ten feet before it can get up to lethal
>> speeds. It never caught on for various reasons including cost and the
>> fact that it really didn't improve on the .45 auto or the traditional
>> combat rifle.
>
>I understood perfectly. Iit was not a gyro that prevented the kickback
>of firing a weapon as stated (in a misleading way). It is a rocket that
>had little or no recoil. Rockets are not bullets. That was my point.
I don't understand. What does that have to do with lasers?
>A laser can use chemical means which do not require cooling also. And
>recently, a laser was constructed that will operate in a 147 degree F
>room. No cooling required.
Chemical lasers lose the "no ammo" advantage on a five year mission.
>> >Nuclear power is very inefficient. A nuclear power plant is a big
>> steam turbine. It >uses nuclear power to heat water to create steam
>> to turn a turbine to generate >electricity. A coal generating plant
>> does the same thing, but it uses coal as the heat
>> >source instead of nuclear power. The actual power generation is the
>> same.
>>
>> A nuclear power plant is as efficient as any other steam engine. But
>> it
>> has the highest energy density we can control, that's why so many
>> submarines and aircraft carriers use them.
>
>You agree with me then.
I don't know. Which part did I agree with?
>> >Some of the biggest guns are big. 18 inch guns require an entire
>> ship
>> >to carry them.
>> But the difference is the 16 inch guns can put a slug through several
>> feet
>> of steel, or make a crater fifty feet wide. (I think only the Yamato
>> had
>> 18 inch guns, and that was sunk during WWII.) And they can keep on
>> firing
>> without needing twice the ship's weight in power plant.
>
>No, but it needs twice the ships weight in shells and explosives that
>will eventually be used up. And how much does the actual gun weight ?
>Several tons. How much does each 16" shell weight...at least 50 or
>maybe 100 pounds if not more. And the recoil in space would be
>tremendous.
The shells weigh as much as a Volkswagon. I agree they wouldn't be a good
choice in space. But we seem to be jumping from space to vehicles to
soldiers to stationary bunkers freely as it fits the argument.
>> >I agree that current lasers are not a good weapon, but I don't
>> believe modern bullets
>> >and weapons would be effective in space once we are able to move
>> >confidently (meaning like driving a car).
>>
>> Depends on what you mean by "move confidently".
>
>Meaning we have spacecraft that we drive in space like we drive cars on
>Earth.
>
>> Modern bullets and weapons can shoot down airplanes that can turn so
>> fast the pilot blacks out.
>
>Vehicles that would allow confident space travel (see above) would be
>too fast for current weapons. They would travel faster than the speed
>of the bullet and be maneuverable and safe, otherwise people would not
>have confidence in them.
Traveling fast doesn't mean anything. When you're evading something,
acceleration is everything. That's why I mentioned planes that corner at
8G, rather than planes that travel at Mach 3.
>> >A bigger weapon the size of a chain machine gun
>> >which has a portable generator could be somewhat effective (it could
>> be
>> >used instead of a flame thrower to start fires in a camp , or explode
>>
>> >fuel and weapons depos, and at much greater distances).
>> I don't know the status of any research like that. But I think you'd
>> need some compelling reasons to use a laser instead of a mortar with
>> incendiary shells.
>
>You could shoot the laser from inside a bunker, unlike a mortar.
And you can shoot a mortar from behind a hill. I assumed you were talking
about man-portable weapons since you were talking about starting fires in
an enemy camp. That's usually a job for airstrikes, or indirect fire like
artillery. Because the enemy is not going to put their camp in sight of
yours.
Jim Carr
glha...@copper.ucs.indiana.edu (Gregory Loren Hansen) writes:
>
>I found the article Timeout referenced. "TRW Laser Destroys Russian
>Rockets" in _Aviation Week & Space Technology_, March 25, 1996, page 58.
>rockets at White Sands Missile Range, N.M.
The only question relevant to such systems is whether it is more
expensive or difficulty to protect the rocket than build the
operational system, given that the rocket builder knows that the
defensive system exists, leaving out the question of how well
it operates in battlefield -- or even field -- conditions.
The air over a nice, warm ocean during a storm is somewhat different
than it is over the NM desert.
--
James A. Carr <j...@scri.fsu.edu> | Commercial e-mail is _NOT_
http://www.scri.fsu.edu/~jac/ | desired to this or any address
Supercomputer Computations Res. Inst. | that resolves to my account
Florida State, Tallahassee FL 32306 | for any reason at any time.
Gregory Loren Hansen
In article <33DA3BE4...@mycomputer.com>,
>> >Nuclear power is very inefficient.
>>
>> Compared to what?
>
>Compared to solar panels that convert directly to energy. A one step
>process, unlike nuclear power that require the heating of water to make
>steam to turn a turbine that makes electricity.
Actually, I read somewhere that it takes more energy to make a solar panel
than you'd get out of the lifetime of its use. Maybe that's no longer
true, or maybe it was only true in certain applications, I forget the
context. But I'm pretty sure solar panel efficiency is still below 30%.
Modern power plants do better than that.
>
>> >A nuclear power plant is a big steam turbine.
>>
>> Not necessarily.
>
>Yes necessarily. That is the way nuclear power plants work. The
>nuclear part is used to heat water to create steam. That is all the
>nuclear part does.
He may have been refering to nuclear batteries or RTGs. For a nuclear
battery, think of a solar cell except with a chunk of nuclear material
taking the place of solar radiation. An RTG is a radioisotope
thermoelectric generator. It's a chunk of radioactive material that stays
hot by nuclear decay, and power is generated by thermopiles as the heat
flows from inside to outside. Both deliver low power but are extremely
rugged, low-maintenance, and long-lived.
Doug Berry
>In article <5rdm1u$8gh$1...@dismay.ucs.indiana.edu>,
>glha...@copper.ucs.indiana.edu (Gregory Loren Hansen) wrote:
>
>> I found the article Timeout referenced. "TRW Laser Destroys Russian
>> Rockets" in _Aviation Week & Space Technology_, March 25, 1996, page 58.
>> Blah Blah Blah
>> Overall it destroys unprotected moving targets at short range, it still
>> needs work, but it's very cool.
>
>Yeah, real cool.
>Was the missile painted black by any chance? Cause my missiles would be
>chromium plated.
Making them that much easier to spot prior to launch and be destroyed
on the ground.
We paint things green for a reason, y'know...
--
+------------------------------------------+
| Doug Berry dbe...@nospam.hooked.net |
| http://www.hooked.net/~dberry/index.html |
| (remove "nospam" to reply by mail) |
|------------------------------------------|
| "I cannot imagine any condition which |
| would cause a ship to founder." |
| -Captain Edward Smith, S.S. Titanic |
+------------------------------------------+
Isaac Kuo
>> >Nuclear power is very inefficient.
>> Compared to what?
>Compared to solar panels that convert directly to energy. A one step
>process, unlike nuclear power that require the heating of water to make
>steam to turn a turbine that makes electricity.
So far we haven't made very efficient photo-electric panels. The
most efficient solar power generators today are ones which heat up
a fluid which runs a turbine.
>> >A nuclear power plant is a big steam turbine.
>> Not necessarily.
>Yes necessarily. That is the way nuclear power plants work. The
>nuclear part is used to heat water to create steam. That is all the
>nuclear part does.
Wrong. Thermoelectric generation is the most favored way of
getting electrical power from a space nuclear power plant in
the foreseeable future. Look at any references and/or conference
proceedings on space nuclear power to see what the SP-100 is
like. (This is not an RTG, but a fission reactor designed for
space use.)
Compared to a turbine, thermoelectric generation is simpler, more
damage resistant (important for near term space applications because
of micrometeorites), and requires much less maintainance.
Another possibility is magnetohydrodynamic electric generation,
which is simple and can have a very high power/weight ratio.
However, electrical energy isn't the only sort of energy you might
want to get from a nuclear reactor. Most notably, one main use
for the reactor is to power a rocket, which it can do by directly
heating the propellant.
--
_____ Isaac Kuo k...@bit.csc.lsu.edu http://www.csc.lsu.edu/~kuo
__|_)o(_|__
/___________\ "Mari-san... Yokatta...
\=\)-----(/=/ ...Yokatta go-buji de..." - Karigari Hiroshi
Robert R. Tucci
> >Yeah, real cool.
> >Was the missile painted black by any chance? Cause my missiles would be
> >chromium plated.
>
> Making them that much easier to spot prior to launch and be destroyed
> on the ground.
>
> We paint things green for a reason, y'know...
Duhh...So I cover the missile with a $1 green tarp when it's on the
ground. It pierces the tarp when I shoot it. Its shinny silver color is
seen once it is fired, making it easier to detect, but the flame coming
out its end gives it away anyway.
Or instead of making my missile chromium plated, I make it spew off gas
from its tip, shrouding it in smoke which dissipates most of the laser
energy before it reaches the missile.
Or I cover the missile with some special ceramic material that dissipates
heat very quickly, like the material used to make the tiles of the space
shuttle.
Or I just wait until a humid day to shoot it.
The ways of counteracting a laser weapon are endless and very cheap. It's
a silly weapon.
Bob Tucci
au...@imap2.asu.edu
: The ways of counteracting a laser weapon are endless and very cheap. It's
: a silly weapon.
And according to some people on rec.aviation.military radars are
pointless as well, because an anti-readiation missile will just blow
them up or they will get "jammed".
And yet they still are getting built and used :-)
regards,
-------------------------------------------------------------------
Steven j Forsberg at au...@imap2.asu.edu Wizard 87-01
Tenhawk
Doug Berry wrote:
>
> On Sat, 26 Jul 1997 19:55:04 -0800, tu...@ar-tiste.com (Robert R.
> Tucci) wrote:
>
> >In article <5rdm1u$8gh$1...@dismay.ucs.indiana.edu>,
> >glha...@copper.ucs.indiana.edu (Gregory Loren Hansen) wrote:
> >
> >> I found the article Timeout referenced. "TRW Laser Destroys Russian
> >> Rockets" in _Aviation Week & Space Technology_, March 25, 1996, page 58.
> >> Blah Blah Blah
> >> Overall it destroys unprotected moving targets at short range, it still
> >> needs work, but it's very cool.
> >
> >Was the missile painted black by any chance? Cause my missiles would be
> >chromium plated.
>
> Making them that much easier to spot prior to launch and be destroyed
> on the ground.
>
> We paint things green for a reason, y'know...
>
help? I dont think that chrome reflects IR and near IR light... and
isn't that what most low power lasers are? and if it doesn't reflect IR
then is it likly to reflect X-Ray and gamma radiation which high powered
lasers ar composed of?
Robert R. Tucci
> >Yeah, real cool.
> >Was the missile painted black by any chance? Cause my missiles would be
> >chromium plated.
>
> Making them that much easier to spot prior to launch and be destroyed
> on the ground.
>
> We paint things green for a reason, y'know...
Duhh...So I cover the missile with a $1 green tarp when it's on the
ground. It pierces the tarp when I shoot it. Its shinny silver color is
seen once it is fired, making it easier to detect, but the flame coming
out its end gives it away anyway.
Or instead of making my missile chromium plated, I make it spew off gas
from its tip, shrouding it in smoke which dissipates most of the laser
energy before it reaches the missile.
Or I cover the missile with some special ceramic material that dissipates
heat very quickly, like the material used to make the tiles of the space
shuttle.
Or I just wait until a humid day to shoot it.
The ways of counteracting a laser weapon are endless and very cheap. It's
a silly weapon.
Bob Tucci
www.ar-tiste.com
Brian Trosko
: ground. It pierces the tarp when I shoot it. Its shinny silver color is
: seen once it is fired, making it easier to detect, but the flame coming
: out its end gives it away anyway.
Have you ever *looked* at a high-energy mirror? It's not just a thin
layer of chrome on top of sheet metal. If you're going to build a mirror
to reflect a high-energy laser, it's got to be very reflective indeed,
because if it absorbs even a small percentage of the incoming energy, it's
toast.
These mirrors are so reflective they're ground in clean rooms, because
even a little dust on the surface renders it nonreflective enough to cause
problems.
So you're going to coat your missile with one of these? And then you're
going to fly it through atmosphere, where it'll squish bugs like a MACH-6
car windshield? And you *still* expect it to reflect a high-energy laser
beam.
That's a bit...optimistic.
: Or instead of making my missile chromium plated, I make it spew off gas
: from its tip, shrouding it in smoke which dissipates most of the laser
: energy before it reaches the missile.
You're firing a supersonic ballistic missile; those have got to be some
pretty hefty smoke generators. You *will* pack enough smoke on board to
last through the entire boost phase, right?
And if you're *not* firing a supersonic ballistic missile, if we're
talking about ASMs or such like, keep in mind your missile isn't that big.
Add that smoke generator, and you complicate your design and reduce your
warhead, your range, and your effectiveness.
: Or I cover the missile with some special ceramic material that dissipates
: heat very quickly, like the material used to make the tiles of the space
: shuttle.
Which won't do much about a laser delivering a megajoule of energy to that
nice ceramic surface. If I set off a stick of dynamite under the shuttle,
those ceramic tiles aren't going to be much good for heat dissipation
henceforth.
: Or I just wait until a humid day to shoot it.
Which won't do much good because for most of its flight path the missile
is above atmosphere.
: The ways of counteracting a laser weapon are endless and very cheap. It's
: a silly weapon.
The ways you've come up with of counteracting a high-energy laser are
either design compromises or likely to be quite ineffective.
Ari Rabkin
In article <33D979DC...@mycomputer.com>, Timeout
<isa...@mycomputer.com> wrote:
> Isaac Kuo wrote:
>
> > >> That's a joke, right? It's not like the speed of a bullet is a
> > >> constant,
> > >> like c. If you fire a bullet (travelling 30 000 fps) out of a ship
> >
> > >> (travelling 3 000 000 fps), you now have a bullet travelling 3 030
> > 000
> > >> fps, which is faster than the ship.
> >
> > This is true...
>
> Not entirely...if you are traveling at 99% the speed of light and shoot
> a projectile at 10% the speed of light, it does not exceed the speed of
> light.
No, but it gets more massive, so its momentum still goes up.
> > >In space, there is space dust which would
> > >completely destroy the unprotected bullet quickly.
> >
> > No there isn't. Not at these speeds, by any stretch of the
> > imagination.
> >
>
> There is plenty of space junk around the Earth, and some of the junk has
> left the confines of earth. And none of the asteroid leave any debris
> behind either do they. Lots of debris in space.
Not as much as you might think. The shuttle goes up reularly, and space
junk has yet to have harmful effects.
> > >The gravitational
> > >pull on bigger objects would deviate the bullets path, although
> > slightly
> > >over a couple of hundred yards, dramatically over 100's of miles.
> >
> > Gravitational pull is something which can be calculated and accounted
> > for. Every gunnery fire control system in the world from .22 rifle
> > open sights to Iowa class battleship fire control necessarily takes
> > it into account to some extent. With repeated salvos, an Iowa can
> > literally put a shell right on top of a target 40 miles away, even
> > with the much greater variabilities of wind.
>
> Granted it is easy on earth where you have almost all the variable
> factors, but in space, you would have to calculate the gravitational
> pull of all objects in the area. Another ship, another planet,
> everything. These calculations would have to be done on a continuous
> basis making minor adjustments between each shot. And at 3,000,000 fps
> (2,045,455 mph) That is about half way from Earth to Mars in one hour to
> give a real comparison. There are several objects that could divert a
> bullets by gravitational forces.
Very easy to calculate out. Planets, asteroids and moons are predictible,
and nothing has noticible mass.
[snip]
> > >10 seconds is plenty of time to react because the
> > >ship would only have to alter the course only slightly.
> >
> > You simply don't understand the maneuvering works in space if
> > you think in terms of "altering course". In space, there is
> > no atmosphere or ocean or road to push wings or hulls or wheels
> > against. You can't just alter your course by rotating your
> > vessel. You have to use rockets or external means to accelerate
> > to change course.
>
> If a ship can travel 3,000,000 fps (which the space shuttle travels at
> 35,200fps for comparison) then altering the course would be easily
> accomplished. The thrusters would be superior, everything would be
> superior.
Ahh, a handwave! Remember that the 'everything will be superior'
argument cuts both ways, bullets will also be superior.
> > >On the other hand, the laser would hit the ship before the pilot
> > >would have time to react.
> >
> > Or the laser could miss, depending on if the laser was aimed well
> > and/or the target maneuvered since the laser was fired.
>
> As you mentioned earlier, 3 million fps is much slower than the speed of
> light (982 million fps). So the pilot would have to react and the ship
> would have to move out of the way in 0.0000000035 seconds due to the
> speed of a laser. Simply not possible.
True, but how much damage do lasers do compared to bullets/APFSDS shells
(a kind of kinetic-kill tank shell)
> > At any rate, this is more true today than it would be in space,
> > because today's soldiers and weapons fight at ranges where the
> > time delay for lasers is practically zero. In contrast to lasers,
> > missiles can take _minutes_ to reach their targets, today.
> >
> > However, despite this obvious advantage lasers have, they aren't
> > used directly as weapons today. Puzzling, isn't it? (sarcasm)
>
> Actually, it is not puzzling. A laser can travel 186,000 miles per
> second. If you do miss you target, there is no fail safe. There is no
> self-destruct like on a missle. The is no limited range like with
> bullets.
Wrong, they are not over-the-horizon, unlike missiles and large (16inch) guns.
> This could be a scenario if they used lasers as offensive
> weapons. You shoot at a hostile jet on the horizon, for some reason you
> miss, and 3,000 miles away an international commuter plane is
> destroyed. That is a reason for not using lasers as offensive weapons.
Aside from the fact that they have a horizon-limited range, do little
damage, and are more expensive.
> > >To destroy the bullet, all the ship in front would have to do is
> > >list out salt or dust.
> >
> > Easier said than done. The salt/dust would drift alongside the
> > ship. There's no such thing as the "ship in front".
>
> Not if you place the dust or salt in a persurized compartment. The
> decompression would cause the salt/dust to be blown away from the ship.
A heavy DU rod will go right through dust! (that momentum does not
just dissapear)
> > We have the concept of destroying incoming projectiles today;
> > it's called CIWS. Some of the better systems do a marvelous
> > job of chewing up an incoming missile--into lots of bits of
> > debris which still hit and severely damage the target ship
> > (but hey, it would have been a lot worse if the missile hit
> > intact, and thus detonated its warhead within the ship).
>
> Researches have successfully used lasers to destroy incoming missles. I
> have referenced them before.
Missiles are easy targets. All you have to do is weaken them too much to
re-enter sucsessfully or miss their targets.
--
Ari Rabkin
arir...@geocities.com
Alan D Kohler
In article <33DBD2...@cancom.net>, ten...@cancom.net says...
>
>Doug Berry wrote:
>>
>> On Sat, 26 Jul 1997 19:55:04 -0800, tu...@ar-tiste.com (Robert R.
>> Tucci) wrote:
>>
>> >In article <5rdm1u$8gh$1...@dismay.ucs.indiana.edu>,
>> >glha...@copper.ucs.indiana.edu (Gregory Loren Hansen) wrote:
>> >
>> >> I found the article Timeout referenced. "TRW Laser Destroys Russian
>> >> Rockets" in _Aviation Week & Space Technology_, March 25, 1996, page 58.
>> >> Blah Blah Blah
>> >> Overall it destroys unprotected moving targets at short range, it still
>> >> needs work, but it's very cool.
>> >
>> >Was the missile painted black by any chance? Cause my missiles would be
>> >chromium plated.
>Chromium? i'm not sure about this but would a chrome platting actually
>help? I dont think that chrome reflects IR and near IR light... and
>isn't that what most low power lasers are? and if it doesn't reflect IR
>then is it likly to reflect X-Ray and gamma radiation which high powered
>lasers ar composed of?
Not yet, they don't. They both are pretty much pipe dreams. Recently, some
researchers found exidence that xenon-droplets may someday be used in x-ray
lasers. Gamma ray lasers probably aren't in our immediate future.
--
SPAM FILTER NOTICE - REMOVE "REMOVE2REPLY" to reply by email.
Alan D Kohler hwk...@REMOVE2REPLYpoky.srv.net
"I can picture in my mind a world without war, a world without hate. And
I can picture us attacking that world because they'd never expect it."
Jack Handly, Deep Thoughts
Isaac Kuo
In article <33DA3BE4...@mycomputer.com>,
>> >But when you are on a five year mission like the TOS then you will
>> >probably run out of ammo unless you get resupplied.
>> As for ammunition, I think you could count the number of times the
>> old Enterprise fired its phasers on your fingers in those 5 years.
>> They weren't on a military campaign.
>But what about TNG and DS9, much phaser fire there which would
>completely use the bullet supply. And they weren't on a military mission
>either.
Huh? When? They weren't on five years missions, at any rate.
>> Actually, the SR71 couldn't be taken down with earlier weapons
>> because of its high altitude. The high speed was necessary to
>> fly so high up in the rarefied atmosphere.
>I refer you to the Nov 1996 issue of Popular Science the "Big zapper"
>article. It is capable of shooting down missles at a range of 250
>miles. The Air Force in the ABL (Airborne Laser) project will have
>modified 747's armed with the lasers within 5 years.
Popular Science has been and remains an exceedingly dubious source
of technical information. They've had cover stories on magnetic
perpetual motion devices, you know...
>> In most terrestrial applications, a steam
>> turbine is used because it is very _efficient_.
>And in what application is nuclear energy used to create electricity
>directly. It isn't.
There is one speculative way to generate electricity directly from
a hypothetical fusion rocket (it involves setting up two spherical
shells of wireframe at the distances from the reaction point at
the radii which protons and electrons can penetrate the magnetic
bottle).
Less speculative is thermoelectric generation, which coverts
differences in temperature into electricity with solid state
thermocouples. _Every_ reference I've ever seen of space
nuclear power research studies this possibility.
>Nuclear creates less airborn pollution than other
>fuel sources, that is why nuclear is used.
No, this isn't. In most current applications, nuclear power is
used because it provides absolutely unparalleled energy densities.
That means a nuclear submarine can truly travel underwater for
an extended period of time, and a nuclear aircraft carrier can
devote more of its capacity to aircraft supplies.
Nuclear power plants have been advocated for many reasons, of
which airborn pollution is only one. If airborn pollution
were the only reason, we'd all be using a lot of solar and wind
power.
>> In space applications, especially unmanned, low maintanaince
>> low mass systems are desirable.
>Are you talking about solar cells, or liquid oxygen. In space they use
>batteries for power and solar panels to help maintain the battery
>charge. Which support my first statement about nuclear power being
>innefficient.
Actually, solar panels are used for most applications because
current applications are low power, and nuclear power is very
expensive (at these power levels, RTGs rather than fission
reactors are appropriate). The mass of the batteries is actually
a seriously annoying factor--satellite designers would love to
eliminate them altogether, because the only time they're needed
is in the small fraction of the time the Earth or Moon gets in
the way of the Sun.
Interplanetary probes to outer planets can't rely on solar power,
so RTGs look favorable. Galileo has "the mother of all RTGs",
more powerful and massy than all previous space RTGs combined.
This includes the RTGs which powered the Viking landers.
Isaac Kuo
>Chromium? i'm not sure about this but would a chrome platting actually
>help? I dont think that chrome reflects IR and near IR light... and
>isn't that what most low power lasers are? and if it doesn't reflect IR
>then is it likly to reflect X-Ray and gamma radiation which high powered
>lasers ar composed of?
What makes you think high powered lasers are composed of X-ray or
gamma radiation? With our current knowledge of physics, the only
plausible way to generate X-ray lasers is either nuclear pumped
(a lot more dubious than initially hoped for), or pump it with
an even more powerful conventional laser (which is what SDI research
on them used). Given the orders of magnitude less powerful and
focussed the pumped laser is compared to the resulting one, the
latter possibility seems pointless.
There isn't any plausible way to make a gamma ray laser.