Non-stealthy rockets
James Nicoll
is virtually impossible in space:
http://www.projectrho.com/rocket/rocket3w.html
This appears to be a well-kept secret in the SF world, as
indicated by the book I am currently work-avoiding, which features
a secret asteroid base only located by intelligence work,
Are there any recent SF books that take the impossibility
of stealth in space into account?
--
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http://www.cafepress.com/jdnicoll (For all your "The problem with
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il...@rcn.com
technology". One is "cryoarithmetic engine" -- a quantum computer
which bleeds off heat into parallel universe, and gets colder as it
runs. Sufficient number of cryoarithmetic engines absorb all excess
heat of a spaceship, making it invisible in IR.
Another solution is directing all heat output of a spaceship into IR
bands which are absorbed by water vapor. This does not hide it from
another spacecraft, but makes it effectively invisible from the
surface of an inhabited planet. Neither trick works well if the
spaceship is under power.
Now that I think of it, there is little effective stealth in Reynolds'
Revelation Space books. (Imperfect) radar stealth not fundamentally
different from what we already have, plus above tricks to hide
infrared emissions. In general, a determined enough foe with
sufficient resources will always find you eventually. In RS universe
stealth mainly benefits someone who is also stronger in other ways.
David E. Siegel
> As we all know, without magical technology stealth
> is virtually impossible in space:
>
> http://www.projectrho.com/rocket/rocket3w.html
>
> This appears to be a well-kept secret in the SF world, as
> indicated by the book I am currently work-avoiding, which features
> a secret asteroid base only located by intelligence work,
given a base which is entirely sub-surface execpt for concealed
access, and given a sufficiently dense asteroid belt (particularly if
it is within the liquid-water zone of its star) finding the base by IR
detection would be a non-trivial excersize. ships which travel to it
ought to be easier to trace, of course.
-DES
tphile
There's Kobold the home of Pak Brennan in Larry Nivens Protector.
he did a pretty good jobe keeping that stealthed.
and there is The Purloined Letter method, Hide it in plain sight
disguised
as something else.
tphile
David DeLaney
>On Jan 18, 3:16 pm, "David E. Siegel" <sie...@acm.org> wrote:
>> jdnic...@panix.com (James Nicoll) wrote:
>> > As we all know, without magical technology stealth
>> > is virtually impossible in space:
>>
>> >http://www.projectrho.com/rocket/rocket3w.html
>>
>> > This appears to be a well-kept secret in the SF world, as
>> > indicated by the book I am currently work-avoiding, which features
>> > a secret asteroid base only located by intelligence work,
>>
>> Given a sufficiently large asteroid (to serve as a heat-sink), and
>> given a base which is entirely sub-surface execpt for concealed
>> access, and given a sufficiently dense asteroid belt (particularly if
>> it is within the liquid-water zone of its star) finding the base by IR
>> detection would be a non-trivial excersize. ships which travel to it
>> ought to be easier to trace, of course.
>
>he did a pretty good jobe keeping that stealthed.
>and there is The Purloined Letter method, Hide it in plain sight
>disguised as something else.
And, going back to NONrecent books (since James is probably already thinking
of this), the Lensman series had a plot point early on about making a ship
as undetectable as possible, given that the usual output of the thrusters
was wildly visible in every direction for quite a ways and that they had
somewhat sophisticated methods for detecting electrical noise too.
Dave
--
\/David DeLaney posting from d...@vic.com "It's not the pot that grows the flower
It's not the clock that slows the hour The definition's plain for anyone to see
Love is all it takes to make a family" - R&P. VISUALIZE HAPPYNET VRbeable<BLINK>
http://www.vic.com/~dbd/ - net.legends FAQ & Magic / I WUV you in all CAPS! --K.
David E. Siegel
True enough, but I don't think that is the kind of more or less
realistic description of ships in space that I think James was looking
for. Whatever you can call the lensman books, "realistic based on
current physics SF" does not seem to fit.
-DES
James Nicoll
wars.
James Nicoll
I am puzzled how "Non-stealthy rockets" as a subject line
and a link to a discussion about how impossible stealth is in
space is leading to a discussion of stealthy rockets in space.
I'm looking for settings where rockets are not stealthy and
this matters to the plot.
William December Starr
jdni...@panix.com (James Nicoll) said:
> I'm looking for settings where rockets are not stealthy and this
> matters to the plot.
It's how the Brennan-monster spotted the Pak Protector fleet, iirc.
--
William December Starr <wds...@panix.com>
Dan Blum
> I am puzzled how "Non-stealthy rockets" as a subject line
> and a link to a discussion about how impossible stealth is in
> space is leading to a discussion of stealthy rockets in space.
> I'm looking for settings where rockets are not stealthy and
> this matters to the plot.
There's Dave Duncan's _Hero!_, although it doesn't involve rockets as such.
--
_______________________________________________________________________
Dan Blum to...@panix.com
"I wouldn't have believed it myself if I hadn't just made it up."
William December Starr
jdni...@panix.com (James Nicoll) said:
> In article
> <ccbc37d1-5133-4265...@e25g2000prg.googlegroups.com>,
> David E. Siegel <sie...@acm.org> wrote:
>
>>> ...the book I am currently work-avoiding, which features a
>>> secret asteroid base only located by intelligence work,
>>
>> Given a sufficiently large asteroid (to serve as a heat-sink),
>> and given a base which is entirely sub-surface execpt for
>> concealed access, and given a sufficiently dense asteroid belt
>> (particularly if it is within the liquid-water zone of its
>> star) finding the base by IR detection would be a non-trivial
>> excersize. ships which travel to it ought to be easier to
>> trace, of course.
>
> Trivially easy, for the sort of civilization that can fight
> space wars.
What if most/all travel to and from it was purely ballistic?
Launch yourself on course from a long distance away (whatever
'long' means in your context), glide unpowered, and then use a
single or series of chemical explosions, mostly contained within a
"gun barrel," to shoot reaction mass ahead of you to brake at your
destination. And launch away from your Sekrit Asteroid Base via,
um, a big rubber-band powered trebuchet, yeah, that's the ticket...
Damien Sullivan
>Now that I think of it, there is little effective stealth in Reynolds'
>Revelation Space books. (Imperfect) radar stealth not fundamentally
There was a bit about tweaking the neutrino emissions of Conjoiner
drives (which were somewhat stealthy otherwise due to extreme focus, I
think) to make them less visible to the Inhibitors.
There's rather effective alien stealth, but not stealthy ships, more
like aliens who hide out somewhere. Revelation Space is kind of all
about a few aliens trying to act stealthily on the world.
-xx- Damien X-)
Ken from Chicago
"James Nicoll" <jdni...@panix.com> wrote in message
news:fmqv5t$1h0$1...@reader2.panix.com...
Heat shielded ballistic jet-black missiles would be fairly
stealthy--especially if early in the launch phase they bled out excess heat
into open space using heat radiating fins.
-- Ken from Chicago (not getting caught by insulating space vacuum again)
Ken from Chicago
Non-stealthy rockets are easy. Heat signatures stand out like beacons.
The CHALLENGE is stealthy rockets--in space.
Natch the heat shielded rockets go ballistic close to the target.
-- Ken from Chicago
Ken from Chicago
"William December Starr" <wds...@panix.com> wrote in message
news:fmrvqh$jc9$1...@panix2.panix.com...
The Pak were looking for stuff to make them go?
-- Ken from Chicago
James Nicoll
>
>The CHALLENGE is stealthy rockets--in space.
>
>Natch the heat shielded rockets go ballistic close to the target.
>
system (Even the shuttle's attitude rockets can be seen from the asteroid
belt).
James Nicoll
This is discussed (aside from the trebuchet) in the link
I gave.
James Nicoll
Ken Burnside has listed the usual responses to the impossibility
of stealth in space thusly:
1) "Space is dark. You're nuts!"
2) "OK, there's no horizon, but the signatures can't be that bright?"
3) "OK, the drive is that bright, but what if it's off?"
4) "But it's not possible to scan the entire sky quickly!"
5) "OK, so the reactors are that bright, what if you direct them somewhere
else..."
6) "What if I build a sunshade?"
7) "OK, so if I can't avoid being detected by thermal output, I'll make
decoys..."
8) "Arrgh. You guys suck all the fun out of life! It's a GAME, dammit!"
GSV Three Minds in a Can
James Nicoll <jdni...@panix.com> said
> From the page I linked to:
>
> Ken Burnside has listed the usual responses to the impossibility
>of stealth in space thusly:
>
>1) "Space is dark. You're nuts!"
>
>2) "OK, there's no horizon, but the signatures can't be that bright?"
>
>3) "OK, the drive is that bright, but what if it's off?"
>
>4) "But it's not possible to scan the entire sky quickly!"
>
>5) "OK, so the reactors are that bright, what if you direct them somewhere
>else..."
>
>6) "What if I build a sunshade?"
>
>7) "OK, so if I can't avoid being detected by thermal output, I'll make
>decoys..."
>
>8) "Arrgh. You guys suck all the fun out of life! It's a GAME, dammit!"
Just arrange to arrive at 0.999999c or whatever .. Ok, so they can see
you coming. They'll get several mS warning even ..
--
GSV Three Minds in a Can
10,414 Km walked. 2,032 Km PROWs surveyed. 36.9% complete.
Ken from Chicago
Right, there's line of sight across the solar system.
So you launch from the dark side of Earth.
Er wait, far side, far side of Earth.
-- Ken from Chicago
James Nicoll
1: You can't reach those speeds with plausible technology.
2: It will take time to reach those speeds even with implausible
technology and if the ImpTech includes anything like a rocket, it will
be visible for light-years in the boost phase.
Ken from Chicago
Geeks go gaga over the details.
Stealth space shield: hollow meteoroid.
-- Ken from Chicago
James Nicoll
>
>So you launch from the dark side of Earth.
>
>Er wait, far side, far side of Earth.
>
>-- Ken from Chicago
>
David Johnston
Nicoll) wrote:
> As we all know, without magical technology stealth
>is virtually impossible in space:
>
>http://www.projectrho.com/rocket/rocket3w.html
>
> This appears to be a well-kept secret in the SF world, as
>indicated by the book I am currently work-avoiding, which features
>a secret asteroid base only located by intelligence work,
>
> Are there any recent SF books that take the impossibility
>of stealth in space into account?
I don't see how they could. There are many SF stories in which people
detect incoming spacecraft. But only way to make a big deal out of
the impossibility of stealth in space is to have them try to be
stealthy and fail, which would make them idiots when everyone would
know it is impossible.
James Nicoll
Not writing books whose plots depend on stealth would be a
good start. In the course of my reading, I run across lots of books,
even ones by supposed hard SF writers, that assume that there would
be something difficult about finding a ship in solar space.
It does occur to me that there's one class of person which
SF accepts as the kind of person who might propose an impossible
program and then insist that mere physical plausibility not be
considered. Maybe the stealth space craft could be some sort of
badly thought-out boonboggle whose main purpose is to send funds
through one well-placed politician's home riding?
Space fighters (also a terrible idea) could be justified
as a means of isolating officers who could otherwise have
safely been sequestered from people with a functioning risk
assessment ability by sending the officers to be cavalry or
paratroopers.
philos...@yahoo.com
Cherryh uses something like this in the short "The Tin Man and Betty
B." During a nasty interstellar war, one side had powered up a long
thick piece of metal and pointed it in such a way that it would
eventually intersect with a space station. And the Pride of Chanur
was quite fond of riding their wavefront down to the station so that
they got there at the same time as the information that they had
appeared in the system.
Rebecca
Ken from Chicago
You misspelled "decoys".
-- Ken from Chicago
Robert Sneddon
<jdni...@panix.com> writes
> I'm looking for settings where rockets are not stealthy and
>this matters to the plot.
The R-bombers in Stross' "Iron Sunrise". They're not stealthy but it
doesn't matter because they're coming at you at .95c. By the time you
spot them it's too late to do anything about them.
--
To reply, my gmail address is nojay1 Robert Sneddon
Damien Sullivan
>Stealth space shield: hollow meteoroid.
Perfect unless you want to go to it, leave it, move it, or use lots of
energy internally.
-xx- Damien X-)
Ken from Chicago
"Damien Sullivan" <pho...@ofb.net> wrote in message
news:fmuu5t$fbs$1...@naig.caltech.edu...
You plot the ballistic course very carefully BEFORE lunch.
-- Ken from Chicago
James Gassaway
--
"Reading by the light of a lost Christmas day
It begins...."
Ken from Chicago
"James Gassaway" <dtr...@sonic.net> wrote in message
news:4793177c$0$36383$742e...@news.sonic.net...
Wait an hour then swim-er launch.
-- Ken from Chicago
James Nicoll
Robert Sneddon <fr...@nospam.demon.co.uk> wrote:
>In message <fmrv6e$njl$1...@reader2.panix.com>, James Nicoll
><jdni...@panix.com> writes
>
>> I'm looking for settings where rockets are not stealthy and
>>this matters to the plot.
>
> The R-bombers in Stross' "Iron Sunrise". They're not stealthy but it
>doesn't matter because they're coming at you at .95c. By the time you
>spot them it's too late to do anything about them.
As I recall, they -were- stealthy. I distinctly remember complaining
about that to Charles Stross.
In a universe with FTL, r-bombs are vulnerable to kinetic
anti-missiles placed in their path by real starships.
Sea Wasp
>
> Wait an hour then swim-er launch.
You're missing the point, Ken.
When you fire your rockets to MOVE the bloody asteroid into your
chosen ballistic course, everyone will see it.
Everyone will already know which asteroid you're at, because they
will have seen the rocket that took your work force there.
Once your rockets stop firing, everyone will know the exact orbit
your asteroid is ON, and therefore can watch it and see anything you
do there.
The point is that it's almost IMPOSSIBLE to be stealthy in space. If
you leave the planet, everyone will know where you go. When you leave
that place, they'll know. You can't hide your progress because people
can FOLLOW you -- without even having to be anywhere near you.
--
Sea Wasp
/^\
;;;
Live Journal: http://seawasp.livejournal.com
Ken from Chicago
"Sea Wasp" <seawasp...@sgeObviousinc.com> wrote in message
news:479363F2...@sgeObviousinc.com...
You DON'T launch the asteroid NEAR the target. You launch it far away, at
least several AUs, preferably doing some gravity assists around other
planets to reinforce the idea it's merely a meteor randomly flying thru
space. That's the point of carefully plotting the ballistic path beforehand.
When you DO get near the target EITHER the meteor hits or you do a virtually
point-blank firing of the missile at the target. So what if they can see you
then because it's too late to enact countermeasures.
-- Ken from Chicago
Sea Wasp
> You DON'T launch the asteroid NEAR the target. You launch it far away, at
> least several AUs, preferably doing some gravity assists around other
> planets to reinforce the idea it's merely a meteor randomly flying thru
> space. That's the point of carefully plotting the ballistic path beforehand.
>
As I said, You Are Missing The Point.
How do you GET to that asteroid several AUs away? Why... you travel
there, BY ROCKET! So we know you went there, and can watch you.
If I'm watching even NEAR that area, I can EASILY see you firing
rockets several AU away. And even if I can't I can EASILY see the
sudden shift of your asteroid's orbit.
YOU CANNOT BE STEALTHY IN SPACE. You can't even drift quietly and
hide for very long, because there will be heat radiated from your ship.
To be stealthy, you pretty much need MagicTech.
James Nicoll
>news:479363F2...@sgeObviousinc.com...
>> Ken from Chicago wrote:
>>
>>>
>>> Wait an hour then swim-er launch.
>>
>> You're missing the point, Ken.
>>
>> When you fire your rockets to MOVE the bloody asteroid into your chosen
>> ballistic course, everyone will see it.
>>
>> Everyone will already know which asteroid you're at, because they will
>> have seen the rocket that took your work force there.
>>
>> Once your rockets stop firing, everyone will know the exact orbit your
>> asteroid is ON, and therefore can watch it and see anything you do there.
>>
>> The point is that it's almost IMPOSSIBLE to be stealthy in space. If you
>> leave the planet, everyone will know where you go. When you leave that
>> place, they'll know. You can't hide your progress because people can
>> FOLLOW you -- without even having to be anywhere near you.
>>
>least several AUs, preferably doing some gravity assists around other
>planets to reinforce the idea it's merely a meteor randomly flying thru
>space. That's the point of carefully plotting the ballistic path beforehand.
>
to off-the-shelf technology out past Pluto. A rocket able to move a decent
sized asteroid is going to have much larger engines than the shuttle and
the people looking for it will have better detection technology.
Let's assume for the moment the rock is a 100 meter cube made
of material the dentisty of water (about one million tonnes), that it
is one of those rocks that can be steered into an Earth-impacting
orbit for almost no delta vee (Let's say 500 m/s) and to conserve
energy use in the hopes of avoiding detection, the ISP of the rocket
has been chosen to maximize efficiency in terms of energy (About
360 m/s, which will give us a mass ratio of about 4).
Shilling gives this as rule of thumb about detection ranges:
Rd = ( 17.8E6 * sqrt( Ms*As*Isp*(1-Nd)*(1-Ns) ) ) * (sqrt(0.04 * p))
Rd = maximum detection range (kilometers)
Ms = bogey spacecraft mass (tons)
As = bogey spacecraft acceleration (G)
Isp = bogey drive specific impulse (seconds)
Nd = bogey drive efficiency (0.0 to 1.0)
Ns = bogey "stealth efficiency", i.e. fraction of waste energy which
can be magically shielded from enemy detectors. (0.0 to 1.0)
p = 3.141593...
So lets plug in numbers:
Ms = One million tonnes
As = .1 m/s/s
Isp = 36
Nd = 0.95
Ns = 0
I get a value for Rd of about 18 AU.
If our cunning masterminds do their burn at 20 AU, say, a
minimum energy orbit will take about 17 years to reach 1 AU. That's
a long time for astronomers not to spot an incoming rock.
Ken from Chicago
"Sea Wasp" <seawasp...@sgeObviousinc.com> wrote in message
Or your opponent has sensors with ludiculously long ranges. Otherwise you
attack from outside their sensor range.
-- Ken from Chicago
Bill Snyder
Then we'll use RoboRockets[TM].
--
Bill Snyder [This space unintentionally left blank.]
James Nicoll
What range do you expect rockets to be visible from and why?
Ken from Chicago
Said sensors can work around intervening moon or planet?
The point of using a meteor is hide in plain sight.
Even better, hide in a meteor SHOWER--from outside your opponent's sensor
range.
Even if inside the range, mask the launch as a nonmilitary flight. As
FIREFOX put it, "Operation Harmless:", "We're all friendly scientists here."
-- Ken from Chicago
James Nicoll
Ken from Chicago <kwicker1...@comcast.net> wrote:
>
>"James Nicoll" <jdni...@panix.com> wrote in message
>news:fmvpu5$aru$1...@reader2.panix.com...
snip context
>Said sensors can work around intervening moon or planet?
Said bodies only block line of sight in a limited part
of the sky.
snip math
>
>The point of using a meteor is hide in plain sight.
You do know that meteors are only meteors once they've
entered the atmosphere, right?
>Even better, hide in a meteor SHOWER--from outside your opponent's sensor
>range.
You remember that the range in question for current day technology
is tens of AU and that the atmosphere does not extend tens of AU?
If you mean a cluster of asteroids, astronomers will notice
when one of the rocks suddenly starts producing gigawatts or more of
waste heat and a great big plume of extremely hot reaction material.
>Even if inside the range, mask the launch as a nonmilitary flight. As
>FIREFOX put it, "Operation Harmless:", "We're all friendly scientists here."
The part where the asteroid's orbit is altered to hit some
target will be seen as hostile, I think.
Ken from Chicago
Okay, I get it now, having read your link that sufficiently large enough
rocket blasts could be detected using current off-the-shelf technology--from
Alpha Centauri.
That said, knowing where the secret asteroid base is:
1) Do the launch BEHIND Earth, the Moon and if possible Mars, or from behind
Jupiter and / or the other Jovian planets if we're attack from "outside" the
Asteroid belt.
2) Cloak the launch with OTHER commercial flights to the Moon, Mars, etc.
3) Transfer the missile into his hollow meteor shell and launch from a
orbit, from a space cannon, so it retains the energy from launch.
4) Said missile is launched AWAY from the asteroid base either toward Venus
or Mercury to do a slingshot so it's coming at the base--WITH THE FRELLING
SUN behind it. Detect THAT, asteroid base! (Besides the same tactic worked
on Earth for millennia.) Natch, if attacking from outside the belt inward,
you don't have the Sun behind it, unless you have the slingshot path go
sunward then back out at the base or maybe having Jupiter behind it to
obscure the sensors.
5) The disguised missile is programmed to launch at a certain time,
coinciding with being within range of the asteroid base and fires ...
breaking up the meteor shell into smaller IGNITED pieces aka decoys while
the missile's main engine fires launching the missile at pert near
point-blank range.
Even better to use multiple missiles in a meteor shower.
-- Stealthy Ken from Chicago
Jack Tingle
> Okay, I get it now, having read your link that sufficiently large enough
> rocket blasts could be detected using current off-the-shelf technology--from
> Alpha Centauri.
>
> That said, knowing where the secret asteroid base is:
> 1) Do the launch BEHIND Earth, the Moon and if possible Mars, or from behind
> Jupiter and / or the other Jovian planets if we're attack from "outside" the
> Asteroid belt.
> 2) Cloak the launch with OTHER commercial flights to the Moon, Mars, etc.
> 3) Transfer the missile into his hollow meteor shell and launch from a
> orbit, from a space cannon, so it retains the energy from launch.
> 4) Said missile is launched AWAY from the asteroid base either toward Venus
> or Mercury to do a slingshot so it's coming at the base--WITH THE FRELLING
> SUN behind it. Detect THAT, asteroid base! (Besides the same tactic worked
> on Earth for millennia.) Natch, if attacking from outside the belt inward,
> you don't have the Sun behind it, unless you have the slingshot path go
> sunward then back out at the base or maybe having Jupiter behind it to
> obscure the sensors.
> 5) The disguised missile is programmed to launch at a certain time,
> coinciding with being within range of the asteroid base and fires ...
> breaking up the meteor shell into smaller IGNITED pieces aka decoys while
> the missile's main engine fires launching the missile at pert near
> point-blank range.
>
> Even better to use multiple missiles in a meteor shower.
All well and good, and all tactics that have been used successfully in
other forms in warfare for millenia. Alas, they're not "stealth" in the
modern aerospace/naval sense*. "Stealth" in the military sense has come
to mean reducing your signature below the other team's ability to
detect. The tactics you describe would be considered hiding, or traffic
deception, or misdirection, or countermeasures, or "coming out of the sun".
Which brings up a minor question, "Is a ghillie suit 'stealth'?" It
might qualify, and if it does, it might just be the very first example
in modern warfare.
Regards,
Jack Tingle
*Some might be inside the common definition. Wiktionary: "the attribute
or characteristic of acting in secrecy, or in such a way that the
actions are unnoticed or difficult to detect by others"
James Gassaway
the same solar system or are launches from a neighboring system to be taken
in to account?
Second, are comets/meteors considered "stealthy"? Because we're not even
sure we're going to know of all the near-Earth planet killers after a decade
long project specifically _to_ find them.
Third, we do not currently have full time-full sky (360 by 360) observation.
I don't know if we even the enough equipment/observatories for it to be
physically possible. Are we assuming in this thought excercise full
time-full sky observation? And how much resources does it take to maintain
that, let alone build it?
Robert Sneddon
<jdni...@panix.com> writes
>> The R-bombers in Stross' "Iron Sunrise". They're not stealthy but it
>>doesn't matter because they're coming at you at .95c. By the time you
>>spot them it's too late to do anything about them.
> In a universe with FTL, r-bombs are vulnerable to kinetic
>anti-missiles placed in their path by real starships.
The R-bombers were manoeuvering to avoid being tracked, so the FTL
starships would have to spot them over a distance of light-months,
extrapolate their tracks and then drop homing anti-missiles in front of
them for a close intercept, say within a few kilometres, and in
interstellar terms that's incredible. Anything more than a few km out
and the R-bombers would be past the deployment point before the
anti-missiles could acquire their targets and get up to speed to make
contact. In a tail-chase the missiles lose unless they can get up to
.96C in a real hurry, in which case they are running up from behind into
the R-bomber's engine flare. See the results of the first human/Kzin
interaction for what happens next.
James Nicoll
James Gassaway <dtr...@sonic.net> wrote:
>A few items/questions, if I may. First, are we assuming launch from within
>the same solar system or are launches from a neighboring system to be taken
>in to account?
>
>Second, are comets/meteors considered "stealthy"? Because we're not even
>sure we're going to know of all the near-Earth planet killers after a decade
>long project specifically _to_ find them.
>
still relatively small and they don't come with convenient gigawatt
flares. C&C with how closely we keep an eye on space near Earth,
where objects in orbit as small as a bolt at tracked.
James Nicoll
Robert Sneddon <fr...@nospam.demon.co.uk> wrote:
>In message <fmvn6a$ppm$1...@reader2.panix.com>, James Nicoll
><jdni...@panix.com> writes
>>In article <Gft2VWNi...@nospam.demon.co.uk>,
>>Robert Sneddon <fr...@nospam.demon.co.uk> wrote:
>
>>> The R-bombers in Stross' "Iron Sunrise". They're not stealthy but it
>>>doesn't matter because they're coming at you at .95c. By the time you
>>>spot them it's too late to do anything about them.
>
>> In a universe with FTL, r-bombs are vulnerable to kinetic
>>anti-missiles placed in their path by real starships.
>
> The R-bombers were manoeuvering to avoid being tracked, so the FTL
>starships would have to spot them over a distance of light-months,
>extrapolate their tracks and then drop homing anti-missiles in front of
>them for a close intercept, say within a few kilometres, and in
>interstellar terms that's incredible. Anything more than a few km out
>and the R-bombers would be past the deployment point before the
>anti-missiles could acquire their targets and get up to speed to make
>contact. In a tail-chase the missiles lose unless they can get up to
>.96C in a real hurry, in which case they are running up from behind into
>the R-bomber's engine flare. See the results of the first human/Kzin
>interaction for what happens next.
Every time they manuever, they signal where they are
and where they are going. The other side is _not_ limited to
sublight speeds so this isn't a tail-chase.
Moriarty
> In article <slrnfp2bgr.d4s....@gatekeeper.vic.com>,
> this matters to the plot.
Iain M Banks "The Algebraist" where the near light speed punitive
force has to travel to the system in question constantly at risk of
being ambushed.
-Moriarty
James Gassaway
> In article <479399f8$0$36337$742e...@news.sonic.net>,
> James Gassaway <dtr...@sonic.net> wrote:
>> A few items/questions, if I may. First, are we assuming launch from
>> within the same solar system or are launches from a neighboring
>> system to be taken in to account?
>>
>> Second, are comets/meteors considered "stealthy"? Because we're not
>> even sure we're going to know of all the near-Earth planet killers
>> after a decade long project specifically _to_ find them.
>>
> True but the effort to find potential Earth-impacters is
> still relatively small and they don't come with convenient gigawatt
> flares. C&C with how closely we keep an eye on space near Earth,
> where objects in orbit as small as a bolt at tracked.
Even then my understanding is that is done more by calculating the orbits of
everything supplemented with intermittent active sensor uses (bouncing a
radar signal off them). They're not maintaining a constant visual (or other
passive sensor) contact with every bit of orbital junk.
Hell, quasars, pulsars and the like have outputs beyond most people's
comprehension but for us to even notice one's existence requires us to be
lucky enough to have something pointed in the right direction at the right
point in time.
David Johnston
Nicoll) wrote:
>
> Not writing books whose plots depend on stealth would be a
>good start. In the course of my reading, I run across lots of books,
>even ones by supposed hard SF writers, that assume that there would
>be something difficult about finding a ship in solar space.
Yeah. A realistic depiction of solar space is kind of boring, and if
you aren't going to be realistic, why keep the lightspeed limit?
>
> It does occur to me that there's one class of person which
>SF accepts as the kind of person who might propose an impossible
>program and then insist that mere physical plausibility not be
>considered. Maybe the stealth space craft could be some sort of
>badly thought-out boonboggle whose main purpose is to send funds
>through one well-placed politician's home riding?
I can see them wasting money on trying to invent stealth but the
result would be another Habbakuk. They'd never actually build it,
they'd just waste a lot of money trying to overcome the insuperable
difficulties in theory.
>
> Space fighters (also a terrible idea) could be justified
>as a means of isolating officers who could otherwise have
>safely been sequestered from people with a functioning risk
>assessment ability by sending the officers to be cavalry or
>paratroopers.
Single man space warcraft have things to recommend them. But they
probably wouldn't be tiny space "planes" where the lifesupport
requirements of even a single occupant would be a significant portion
of the craft's space. Instead they'd be one guy riding herd on the
computer of a vessel big enough that they don't lose much
functionality from the human occupant but small enough that they could
still be effectively maintained by a mothership. Maybe about the size
of a PT Boat, but with only one crewmember.
>
>
>
Damien Sullivan
>> The R-bombers were manoeuvering to avoid being tracked, so the FTL
>>starships would have to spot them over a distance of light-months,
> Every time they manuever, they signal where they are
>and where they are going. The other side is _not_ limited to
That's no always true. A low-EM mass driver, or better yet compressed
gas thrusters, should be undetectable. Hell, even space shuttle main
engines could work -- I'm assuming this is lateral maneuvering after the
initial acceleration, so it's still happening light-years away. Hard to
detect and probably low precision even if detected. And with
light-years, even the low delta-vee of compressed gas adds up to a large
deviation.
Which is the real problem; the bombers are trying to hit a target, which
limits how much trajectory altering they can do between launch and
target. So the target at least knows in what direction to squint. But
you've got the area of a planet to defend.
-xx- Damien X-)
Damien Sullivan
>A few items/questions, if I may. First, are we assuming launch from within
>the same solar system or are launches from a neighboring system to be taken
>in to account?
I usually assume same-system.
>Third, we do not currently have full time-full sky (360 by 360) observation.
>I don't know if we even the enough equipment/observatories for it to be
>physically possible. Are we assuming in this thought excercise full
>time-full sky observation? And how much resources does it take to maintain
>that, let alone build it?
http://www.projectrho.com/rocket/rocket3w.html#nostealth
Talks early on about it taking a modern instrument 4 hours to do a full
sky survey with a wide angle lens. Using the numbers, looks like 480
cameras to get overlapping full coverage of the sky.
Another approach is to dedicate a telescope to full-time tracking
every known ship, and every asteroid or larger body in the system where
someone might be hiding to make a ship (a ridiculous idea with modern
industrial limitations, but standard SF.) Thousands of telescopes for
the asteroids; still seems affordable. As for ships, well, I think
they'd be more expensive than the sensors tracking them...
As for quasars, they're really far away. Pulsars too, and they don't
always pulse at us.
-xx- Damien X-)
Damien Sullivan
>Or your opponent has sensors with ludiculously long ranges. Otherwise you
>attack from outside their sensor range.
These arguments often suffer from a lack of context, e.g. who's
attacking what, where?
The most realistic space scenario is humans and their machines in our
solar system, within the next century or two. Given this, I think a lot
of your proposals fall apart.
As for launch from 20 AU away... your asteroid will take a long time to get
anywhere from there. Unless you use bigger engines, but that makes them
more detectable. "Distance cancels out of the math on that one." A
stealthy attack that takes years[1] to hit isn't useful in most contexts
we usually think of.
[1] 3e9 kilometers, speed no more than 30 km/s (Uranus is 20 AU out,
orbital velocity of 7 km/s), time 1e8 seconds == 3 years.
-xx- Damien X-)
Damien Sullivan
>Said sensors can work around intervening moon or planet?
Again, what's the scenario? Easy enough to put sensors through the
solar system.
>Even better, hide in a meteor SHOWER--from outside your opponent's sensor
>range.
How?
A meteor shower comes from the debris trail of a comet,
hitting Earth's atmosphere. You have to accelerate to the trail,
and decelerate there, without being noticed. Then wait and not be
noticed, although it's not clear there'd be anything there big enough to
hide you.
-xx- Damien X-)
Bill Snyder
Googling suggest most particles range from dust-speck up to raisin
size; and that the summed particle-volume of the entire shower is
probably a good deal less than that of any ship with the delta-vee to
try to hide in one and the endurance to stay there for a reasonable
span of time.
Wayne Throop
: You plot the ballistic course very carefully BEFORE lunch.
Astronavigators do more before lunch than ordinary navigators
do all week?
Wayne Throop thr...@sheol.org http://sheol.org/throopw
Nyrath the nearly wise
> http://www.projectrho.com/rocket/rocket3w.html
>
> This appears to be a well-kept secret in the SF world, as
> indicated by the book I am currently work-avoiding, which features
> a secret asteroid base only located by intelligence work,
>
> of stealth in space into account?
I don't' know about "recent", but in NIGHTRIDER by David Mace (1985)
there is an experimental gravity drive that is used for
stealth purposes.
The idea is that whenever a spacecraft changes its trajectory
with rocket propulsion, you can see it all over the solar system,
and can therefore calculate where it will be at any point in the
future. You keep a telescope on its calculated position, and
can easily spot any future trajectory changes. (In the novel,
the heat of the habitat module cannot be detected for some
unexplained reason.)
So one nation's military seeks an advantage with an undetectable
gravity drive. Since it has no exhaust, it is undetectable.
(The author doesn't explain why its waste heat nor the waste heat
of the power plant can be detected, but I digress.)
So the sneaky rocket can use its conventional rocket propulsion,
have the enemy calculate its future trajectory, then at some point
fool the enemy by making an invisible course change and achieving
strategic surprise.
William December Starr
jdni...@panix.com (James Nicoll) said:
> This is discussed (aside from the trebuchet) in the link I gave.
Mmph. Not entirely; the article[*1] seems to focus on space
warfare, assuming two things: actively crewed ships and the desire
to manuever into (or avoid) battle configurations.
*1: <http://www.projectrho.com/rocket/rocket3w.html>
If you just want to send, say, one person to the top secret asteroid
base where you store your basball card collection or nova bomb
research data or whatever, and you can spend a month or three
getting him there, the situation shifts a bit in your favor. And
much more so if you aren't even sending a living being (life-support
heat signature? what life-support?), or, come to think of it, if
you've got some sort of coldsleep/suspended-animation technology.
I don't make the foolish claim that this _removes_ any of the hurdles
that the article discusses; just that it lowers them somewhat.
--
William December Starr <wds...@panix.com>
William December Starr
pho...@ofb.net (Damien Sullivan) said:
> As for launch from 20 AU away... your asteroid will take a long
> time to get anywhere from there. Unless you use bigger engines,
> but that makes them more detectable. "Distance cancels out of the
> math on that one." A stealthy attack that takes years[1] to hit
> isn't useful in most contexts we usually think of.
Could work as a final-strike component of a Mutually Assured
Destruction scheme, though. As seen, at much larger scale, as
a plot element in Stross' IRON SUNRISE.
dwight...@gmail.com
> On Sat, 19 Jan 2008 21:16:12 +0000 (UTC), jdnic...@panix.com (James
Well, no, all you've got to do is change the solid angle out of which
you radiate waste heat. Narrow it down to half a degree, and it's
going to take a big, expensive network to detect your ship, or your
pod or whatever. With the right assumptions about technology, cost,
etc, it becomes very hard to find a such a stealthed ship. Change the
assumptions, and it becomes ludicrously easy.
Neither situation is forbidden by physical law.
DougL
> jdnic...@panix.com (James Nicoll) wrote:
> >Robert Sneddon <f...@nospam.demon.co.uk> wrote:
> >> The R-bombers were manoeuvering to avoid being tracked, so the FTL
> >>starships would have to spot them over a distance of light-months,
> > Every time they manuever, they signal where they are
> >and where they are going. The other side is _not_ limited to
>
> That's no always true. A low-EM mass driver, or better yet compressed
> gas thrusters, should be undetectable. Hell, even space shuttle main
> engines could work -- I'm assuming this is lateral maneuvering after the
> initial acceleration, so it's still happening light-years away. Hard to
> detect and probably low precision even if detected. And with
> light-years, even the low delta-vee of compressed gas adds up to a large
> deviation.
I know where you started, I know almost exactly where you are headed
and how fast, I can move FTL so as to spot your wake (which is VERY
noticable travelling through the interstellar medium at that speed), I
can get in front of you and drop sand or expel gas, you either burn
HARD to dodge the sand, or you blow up. If you burn hard I try again
till you are out of fuel.
Worse, YOU DON'T KNOW YOU NEED TO DODGE! I'm stealthier than you are
(only one of us is ramming magnetic fields and gas at 95% of c), and
you have all the trouble spotting my fire in time to dodge that I have
spotting your ship in the first place, except you don't know when and
where to look. Ergo you must either dodge CONSTANTLY or don't bother
to do so at all.
> Which is the real problem; the bombers are trying to hit a target, which
> limits how much trajectory altering they can do between launch and
> target. So the target at least knows in what direction to squint. But
> you've got the area of a planet to defend.
And a relatively low density gas cloud will convert your weapon into
exploding vapor.
DougL
DougL
The right assumptions being to ignore the second law of
thermodynamics.
Energy you can radiate into such a small area is pretty well by
definition usable energy.
There's an extensive discussion in the link (assuming it's the usual
one used in these discussions) of the problems of limiting the area
you radiate into.
This is like Brin's "Cooling Laser".
> Neither situation is forbidden by physical law.
Actually one pretty well is. With anything less than roughly 99.96% of
maximum possible efficiency heat pumps you CAN'T send your waste heat
in such a narrow cone, with such near perfect pumps you're mearly
"wasting" effectively all your power on the heat pumps to cool the
back sides of your radiators....
Note that your crew counts as an inefficiency by this standard.
Then we'll discuss the likelihood that such large radiators as will be
needed will occlude stars with some regularity...
DougL
Damien Sullivan
>I know where you started, I know almost exactly where you are headed
>and how fast, I can move FTL so as to spot your wake (which is VERY
>noticable travelling through the interstellar medium at that speed), I
Oh, forgot we were dealing with Iron Sunrise, so defenders had FTL.
-xx- Damien X-)
Damien Sullivan
>Mmph. Not entirely; the article[*1] seems to focus on space
>warfare, assuming two things: actively crewed ships and the desire
>to manuever into (or avoid) battle configurations.
>
> *1: <http://www.projectrho.com/rocket/rocket3w.html>
Yeah, the site is a bit of a compromise between reality and science
fiction. Elsewhere they talk about how missiles and heavy automation
are probably the way to go, but humans don't want to read about missile
volleys. And maybe we will reach space before we get full AI, so
intelligent monkeys need to be shipped around at some point.
-xx- Damien X-)
James Nicoll
Nyrath the nearly wise <nyr...@projectrho.com.INVALID> wrote:
>James Nicoll wrote:
>> http://www.projectrho.com/rocket/rocket3w.html
>>
>> This appears to be a well-kept secret in the SF world, as
>> indicated by the book I am currently work-avoiding, which features
>> a secret asteroid base only located by intelligence work,
>>
>> Are there any recent SF books that take the impossibility
>> of stealth in space into account?
>
> I don't' know about "recent", but in NIGHTRIDER by David Mace (1985)
> there is an experimental gravity drive that is used for
> stealth purposes.
>
Joseph Nebus
Maybe the solution is to start writing the novels that the
missiles want to read?
--
Joseph Nebus
------------------------------------------------------------------------------
dwight...@gmail.com
Er, you do know that 'solid angle' and 'area' are different, yes?
There's other things wrong there, but we can start with that.
David E. Siegel
> A few items/questions, if I may. First, are we assuming launch from within
> the same solar system or are launches from a neighboring system to be taken
> in to account?
>
> Second, are comets/meteors considered "stealthy"? Because we're not even
> sure we're going to know of all the near-Earth planet killers after a decade
> long project specifically _to_ find them.
>
very likley be, they would be much easier to find.
> Third, we do not currently have full time-full sky (360 by 360) observation.
> I don't know if we even the enough equipment/observatories for it to be
> physically possible. Are we assuming in this thought excercise full
> time-full sky observation? And how much resources does it take to maintain
> that, let alone build it?
>
Given a permanent in-vacuum presence, a continuous 360 x 360 IR scan
is fairly cheap, even with today's hardware. (computers call to human
attention any signal that falls outside their programed parameters for
"ordinary") Add in the amount of tech improvement needed for even
interplanetary conflict to be likely, and it probably costs no more in
relative terms than the sonar installation on a modern naval vessel.
-DES
dwight...@gmail.com
I've looked at the Project Rho site, and this seems to make no sense:
<blockquote>And if you try to focus the emissions into some very
narrow cone you know to be safe, you run into the problem that the
radiator area for a given power is inversely proportional to the
fraction of the sky illuminated. With proportionate increase in both
the heat leakage through the back surfaces, and the signature to
active or semi-active (reflected sunlight) sensors.</blockquote>
Take a sphere of radius R at a temperature of 1000 degrees. By the
simple fourth power law, it's radiating about 5600 W/m^2. So it's
total radiated power is 4piR^2*5600 watts, and each square meter
subtends a solid angle proportional to 1/(4piR^2). Now take a sphere
of radius 2R, it's radiating four times as much, yet each square meter
subtends only one fourth the solid angle, while still having the same
radiating power as before.
So has referenced by the site, this 'fact' is simply wrong, or rather,
misapplied.
To get a narrow cone, all you need do is put the radiator (make it
cylindrical) in a right-angled cone; extend the cone past the
radiator, and cap it with a semi-parabolic mirror.
Is the rest of the Project Rho site like this?
cryptoguy
>
> - Show quoted text -
What if your rocket doesn't have a hot exhaust? I'm thinking
of things like a child's water rocket, where compressed air
expels water - since the gas is expanding, its actually COLDER
than the environment....
Even pure compressed air rockets can have useful thrust -
Evel Kneviel (sp?) Snake River rocket cycle was a compressed
air rocket.
Even if the initial velocity was given by a conventional hot
exhaust rocket, using a cold exhaust system for manuvering
could make the system much more stealthy.
Peter Trei
Aaron Denney
> Third, we do not currently have full time-full sky (360 by 360) observation.
360 by 180. But that's an artifact of a not necessarily good coordinate
system. Say, rather, 4 pi steradian.
> I don't know if we even the enough equipment/observatories for it to be
> physically possible. Are we assuming in this thought excercise full
> time-full sky observation? And how much resources does it take to maintain
> that, let alone build it?
It's pretty easily doable, if we thought it necessary.
--
Aaron Denney
-><-
dwight...@gmail.com
Sure. Or a mass driver using extremely cold blocks of propellant.
The issue of stealth/nonstealth is not an issue of fundamental
physics, or even of technological constraints, really. It's one of
economics.
DougL
Even without that the intercept problem is utterly trivial compared to
the problem of accelerating the projectile in the first place. If you
can accelerate to 95% c then I can hit you with some trivial fraction
of the same mass accelerated to 5% c in the opposite direction.
Everything that makes you hard to hit applies, but an order of
magnitude or so worse, for you being able to see my shot and dodge or
block it.
Any tech that can throw relativistic rocks can counter them with such
east that it makes throwing them in the first place a phenomenal waste
of effort.
It's the high tech equivelent of claiming that we could make a REALLY
REALLY good Atlatl if we wanted to and could then beat the Aztecs with
ease. Um, yeh. I don't think that's going to strike terror into the
hearts of any modern power though.
DougL
DougL
Yes, what I don't see is how this is relevant. You need BIG radiators
and baffles to radiate to a small solid angle while remaining
consistent with actual physics and keeping your radiator at an even
vaguely plausible temperature (and hotter radiators are automatically
wasteful since you need to pump the heat into the hot radiator).
Radiation to a small solid angle reduces the entropy of what you are
radiating. You are throwing away more and more usable energy to get
rid of smaller and smaller amounts of entropy, this is a losing
proposition.
DougL
DougL
No. That won't work. You've creating a black body cavity and radiate
to at least 1 Pi steradians. The reflector is simply part of the (new)
cavity.
> Is the rest of the Project Rho site like this?
You mean knows more than you do?
Probably.
DougL
dwight...@gmail.com
You really don't get it, do you? Do you always have this much problem
following an argument?
If you don't understand the argument, just say so, and ask questions.
Rephrasing what was originally said and to what I responded is _not_
a reply.
James Gassaway
> On 2008-01-20, James Gassaway <dtr...@sonic.net> wrote:
>> Third, we do not currently have full time-full sky (360 by 360)
>> observation.
>
> 360 by 180. But that's an artifact of a not necessarily good
> coordinate system. Say, rather, 4 pi steradian.
You're assuming that no space-based attack can ever come from the sunlight
side of the planet?
>
>> I don't know if we even the enough equipment/observatories for it to
>> be physically possible. Are we assuming in this thought excercise
>> full time-full sky observation? And how much resources does it take
>> to maintain that, let alone build it?
>
> It's pretty easily doable, if we thought it necessary.
--
"Reading by the light of a lost Christmas day
It begins...."
James Gassaway
course changes/corrections (and therefore emissions) below the threshold of
the program's "notify a human"?
Aaron Denney
> Aaron Denney wrote:
>> On 2008-01-20, James Gassaway <dtr...@sonic.net> wrote:
>>> Third, we do not currently have full time-full sky (360 by 360)
>>> observation.
>>
>> 360 by 180. But that's an artifact of a not necessarily good
>> coordinate system. Say, rather, 4 pi steradian.
>
> You're assuming that no space-based attack can ever come from the sunlight
> side of the planet?
No, I'm assuming that longitude ranges from -180 to 180, and latitude
from -90 to 90. 360 x 180. This coordinate system isn't great because
a "square degree" near the pole is quite different than one near the
equator.
Damien Sullivan
>My first thought here is could a spacecraft trying to be stealthy keep its
>course changes/corrections (and therefore emissions) below the threshold of
>the program's "notify a human"?
Only by being very very slow, I'd think. Basically if the computer
notices anything that isn't a known asteroid or a ship following a filed
flight plan, it notifies a human.
-xx- Damien X-)
David E. Siegel
<snip>
> I've looked at the Project Rho site, and this seems to make no sense:
>
> <blockquote>And if you try to focus the emissions into some very
> narrow cone you know to be safe, you run into the problem that the
> radiator area for a given power is inversely proportional to the
> fraction of the sky illuminated. With proportionate increase in both
> the heat leakage through the back surfaces, and the signature to
> active or semi-active (reflected sunlight) sensors.</blockquote>
>
> Take a sphere of radius R at a temperature of 1000 degrees. By the
> simple fourth power law, it's radiating about 5600 W/m^2. So it's
> total radiated power is 4piR^2*5600 watts, and each square meter
> subtends a solid angle proportional to 1/(4piR^2). Now take a sphere
> of radius 2R, it's radiating four times as much, yet each square meter
> subtends only one fourth the solid angle, while still having the same
> radiating power as before.
>
> So has referenced by the site, this 'fact' is simply wrong, or rather,
> misapplied.
>
> To get a narrow cone, all you need do is put the radiator (make it
> cylindrical) in a right-angled cone; extend the cone past the
> radiator, and cap it with a semi-parabolic mirror.
>
> Is the rest of the Project Rho site like this?-
I believe that you have misunderstood. What I take the site to be
saying is: "If you have W waits to radiate away (too cool your ship/
base/whatever) and you want those radiations to go into ONLY a
relatively narrow cone, for a given radiator power, the required
radiator area is in inversely proportional to the size of the cone.
To put it another way: W = Ra * Rp * Sa where:
W = the wattage to be radiated away;
Ra = the Radiator area (the area of the actual radiator surface);
Rp = the radiator power (energy radiated per unit area; this is
proportional to radiator temperature);
Sa = the solid angle into which radiation is allowed. Call this 1 if
radiation is to the whole sky, and some fraction less than 1 if it is
to be restricted.
The more you restrict Sa, the more you must increase Ra or Rp or both
to deal with W, which presumable is fixed by the size of your ship[/
base and the equipment/powers sources/drive it contains. Increasing Ra
increases the physical size of the structure, and the chance of
detection through occlusion -- it also probably increases the cost.
Increasing Rp increases the strength of the signal within the "unsafe
cone", increases the chance of leaks to unwanted parts of the sky, and
is limited by your technology in any case -- if by nothing else, by
the melting point of the radiator itself.
-DES
Damien Sullivan
>Even without that the intercept problem is utterly trivial compared to
>the problem of accelerating the projectile in the first place. If you
>can accelerate to 95% c then I can hit you with some trivial fraction
>of the same mass accelerated to 5% c in the opposite direction.
I don't think it's that easy.
Let's be specific. The R-bombers accelerate a couple of light years
away. This is visible for light-years, everyone knows they're coming,
roughly how fast, and maybe even which planet in the solar system
they're aiming at. But they're not that big, when they're done
accelerating they run cold, and they can use cold jets to stealthily
dodge laterally, or even add small amounts of imprecision to their
direct velocity.
Their target is a planet. Big, visible, and on a known trajectory.
Unless we invoke Paul Birch planets don't dodge. If it, or even most of
its fragments, hit the planet thenm it delivers its 'payload' of kinetic
energy.
Your target is a cold R-bomber, possibly less than 100 meters in radius,
stealthed against radar and not emitting much heat (AI crew), coming in
at near lightspeed anywhere within a 6000 kilometer radius (I'm using
the size of Earth.) Diverting this or blocking it early enough so that
fragments miss the planet doesn't seem that trivial to me. It can still
do cold random dodges as it draws near, and emit low-mass films ahead of
it to pre-react with low-density clouds you might have strewn in its
path.
>Everything that makes you hard to hit applies, but an order of
>magnitude or so worse, for you being able to see my shot and dodge or
>block it.
Don't need to dodge specific shots, just avoid being on a predictable
trajectory. And the R-bomber has to block a 100 meter radius area, you
have to block a 6000 kilometer raidus area.
-xx- Damien X-)
David E. Siegel
source of IR signal, and the sources produced by any practical
thrusters within the same solar system (certainly within the inner
system) or indeed by the signal from a powered (particularly if
carrying human life support) object NOT under any thrust, that a
reasonably well designed software package is not likely to have many
if any false negatives. For thrust alone, if you are willing to spend
decades getting in place, and if your craft is not otherwise powered
at all (which rules out human-life conditions aboard) then maybe such
a system could be evaded. The longer you are willing to spend getting
somewhere, the lower thrust can be used, and the longer it takes to be
detected -- but then you *need* a longer detection-free period.
-DES
David Johnston
Sullivan) wrote:
>DougL <lamper...@gmail.com> wrote:
>>On Jan 21, 1:02 am, phoe...@ofb.net (Damien Sullivan) wrote:
>
>>Even without that the intercept problem is utterly trivial compared to
>>the problem of accelerating the projectile in the first place. If you
>>can accelerate to 95% c then I can hit you with some trivial fraction
>>of the same mass accelerated to 5% c in the opposite direction.
>
>I don't think it's that easy.
>
>Let's be specific. The R-bombers accelerate a couple of light years
>away. This is visible for light-years, everyone knows they're coming,
>roughly how fast, and maybe even which planet in the solar system
>they're aiming at. But they're not that big, when they're done
>accelerating they run cold, and they can use cold jets to stealthily
>dodge laterally, or even add small amounts of imprecision to their
>direct velocity.
Won't they experience significant amounts of friction at that speed?
dwight...@gmail.com
I'm talking about something a little different. Say you have a
uniform sphere out in space with a surface area of eight square meters
and a temperature of 1000 K. Take three infinite perfectly reflecting
planes that are mutually perpendicular and put the sphere at the exact
center so that it is divided into eight equal parts. By symmetry, this
does not affect the radiative output of the initial sphere in the
slightest; whereas photons were initially coming in from one
direction, they can now be taken as bouncing off the mirror. This is
a little bit hard for me to explain, but I hope you get the picture,
and the idea that nothing physical has changed. So each octant has an
area of one square meter, is at a temperature of 1000 degrees, and is
radiating about 5600 watts to one eighth of the sky. Now double the
radius of the sphere, which quadruples the area, and subdivide each
octant into four equal pieces; you can get them all by inserting three
more 'planes', more or less, again extending towards infinity. Note
that you now have 32 'triangles' instead of eight, each radiating 5600
watts, (which makes sense), but now each triangle is only radiating
towards 1/32 of the sky. Since the mirrors are perfectly reflecting,
take away 31 of the other pieces; voila! the same amount energy being
lost to a diminished piece of the sky.
Note that this does not violate any of the laws of thermodynamics,
btw. Here's the trick: we can make the angle as small as we like,
provided that the area we radiate to becomes correspondingly larger.
If we want to cut our angle subtended by a factor of one hundred, we
can get away with this, provided the area we 'radiate through' is one
hundred times larger. This is nice, because that means that the
radiator does not have to grow in size, only the optical arrangement.
And the optics are much lighter, and much cheaper than the radiator
itself.
I wish I was in front of a blackboard so I could draw the diagrams,
but I think this might suffice for the argument. The basic idea for
these types of arguments is to think about what the various pieces of
the setup 'know'. As long as you follow that principle, and don't
make any assumptions that increase the information available to those
pieces that violate the laws of physics, you're usually on pretty
solid ground. In this case, we use the idea that in the original
division into eight pieces by the mirrors that each segment does not
'know' whether a photon is coming in from another segment, as opposed
to being reflected back into it.
James Gassaway
Ah, I was thinking two circles at right angles to each other. 360 degree
circle "horizontal" by 360 degree "vertical".
Joseph Nebus
I think you can avoid that inconvenience of wildly different
`square degree' areas, at least, by using as your coordinate system the
sine of the latitude and then the longitude in radians, although this
doesn't do anything to avoid the odd effects that being near a pole will
have on coordinates. Also I've never been able to figure out what if
any name that projection has.
--
Joseph Nebus
------------------------------------------------------------------------------
Plus, whoever heard of watching the skies [1, -1]x[0, 2\pi)
anyway?
David E. Siegel
>
> > To put it another way: W = Ra * Rp * Sa where:
>
> > W = the wattage to be radiated away;
> > Ra = the Radiator area (the area of the actual radiator surface);
> > Rp = the radiator power (energy radiated per unit area; this is
> > proportional to radiator temperature);
> > Sa = the solid angle into which radiation is allowed. Call this 1 if
> > radiation is to the whole sky, and some fraction less than 1 if it is
> > to be restricted.
>
> > The more you restrict Sa, the more you must increase Ra or Rp or both
> > base and the equipment/power sources/drive it contains. Increasing Ra
Note that when you doubled the radius of the sphere above, you
increased the dimensions of the parts of the planes that actually
intersect the sphere from 0.797+ meters to 1.595+ meters thereby
multiplying their area by a factor of 4. Note that any actual,
physical radiators in the system do NOT have infinite areas (nor are
they perfect reflectors). If you wish to construct a physical system
that radiates to only a limited part of the sky, as you reduce that
area you must increase either the physical area of the radiators, or
the amount of energy radiated per unit area (and thus the
temperature), or both, if the total energy to be radiated stays
constant. note also that when you say "whereas photons were initially
coming in from one direction, they can now be taken as bouncing off
the mirror" bouncing off the mirror is NOT free, it raises the
temperature of the mirror in any physical system. This is at the
expense of actual cooling, if the same photon must be radiated more
than once by the system.
You say above that: "If we want to cut our angle subtended by a factor
of one hundred, we can get away with this, provided the area we
'radiate through' is one hundred times larger." Exactly! Increasing
radiator area is a significant burden to the "stealth" ship, and is
precisely what was meant by the site in saying that "you run into the
problem that the radiator area for a given power is inversely
proportional to the fraction of the sky illuminated." that is, as the
part of the sky to which radiation is confined shrinks, the radiator
area must grow, all else being held constant. You have just gone to a
lot of trouble to confirm that the original quote, which you said
"seems to make no sense" is in fact correct.
When you say that "the radiator does not have to grow in size, only
the optical arrangement." do you mean that the "optical arrangement"
includes your perfect plane mirrors extending to infinity? Any
physical realization or approximation of such a system is going to
have non-trivial costs and effects, and if you don't extend those
reflecting planes to infinity, some of the emissions will escape
beyond your desired sector of sky.
-DES
dwight...@gmail.com
I don't think we're communicating very well here - putting in the
perfect reflectors _does_not_change_ what the system would see absent
the reflectors. The reflectors are perfect and they do not absorb any
photons.
That's the point of putting them in.
> You say above that: "If we want to cut our angle subtended by a factor
> of one hundred, we can get away with this, provided the area we
> 'radiate through' is one hundred times larger." Exactly! Increasing
> radiator area is a significant burden to the "stealth" ship, and is
No, it is not the radiator itself whose area you must increase, though
that is one (extremely inefficient) way to get the increased area.
The statement in the Project Rho page seems to think that the only way
to do this is to build a physical radiator with 100x the area, and
then put it in a perfectly reflective cavity that has a small
opening. What you can also do is 'unfold' the area so that it is all
'pointing at' the same direction. This is entirely consist with basic
thermo; what would be inconsistent would be to have the same amount of
energy emitted by the radiator going through a smaller area than the
total surface of the radiator. _That_ is definitely impossible.
> precisely what was meant by the site in saying that "you run into the
> problem that the radiator area for a given power is inversely
> proportional to the fraction of the sky illuminated." that is, as the
> part of the sky to which radiation is confined shrinks, the radiator
> area must grow, all else being held constant. You have just gone to a
> lot of trouble to confirm that the original quote, which you said
> "seems to make no sense" is in fact correct.
Again, no. It's more complicated than that. If you don't understand
the argument by symmetry, please ask what you need clarified, or what
seems counterintuitive. Meanwhile, here's a sloppier way: Imagine a
spherical radiator centered at the focus of a paraboloid. Most of the
flux will end up going in the same direction, yes? The problem is,
this only works in the ideal case where the radiator is a point. So
that a) the rays of emission are not perfectly parallel, and b) the
radiator intercepts some proportion of the emissions. This is much
worse, in fact, this is what is being alluded to in the quote from
Project Rho - a radiator that emits and then reabsorbs it's own flux
really isn't radiating, is it? But what we can do is approach that
limit by making the dimensions of the paraboloid large with respect to
the dimensions of the radiator; if the radiator is one centimeter
across and the paraboloid through the focus is one thousand meters,
then we approach the ideal situation (modulo other considerations like
the diffraction limit), and we can make the beam as parallel as we
like, i.e., the cone of emission can be as narrow as we wish.
Note that the radiator has not increased in area, only the
paraboloid.
> When you say that "the radiator does not have to grow in size, only
> the optical arrangement." do you mean that the "optical arrangement"
> includes your perfect plane mirrors extending to infinity? Any
> physical realization or approximation of such a system is going to
> have non-trivial costs and effects, and if you don't extend those
> reflecting planes to infinity, some of the emissions will escape
> beyond your desired sector of sky.
>
> -DES
The infinite reflectors were only used to invoke the symmetry
argument. I think I've explained what I meant by the optical
arrangement above when talking about paraboloids. Note, again, that
the area of the plane through which the roughly parallel lines of
emissions pass must be at least as large as the area of the radiator,
otherwise the second law is violated. This is what holds true of any
example, and this was (I'm guessing, what the original poster
mistakenly was thinking of.
But back to the discussion of stealth, it is clear that the radiator
does not have to grow in size and mass (though frankly, the latter is
really just a technological argument, and shouldn't have counted
against the original idea . . . this is science fiction, after all,
albeit supposedly hard sf) Only the optical apparatus. And since the
'optical apparatus' is mostly mirror, the mass considerations don't
really matter.
Anthony Nance
> As we all know, without magical technology stealth
> is virtually impossible in space:
>
> http://www.projectrho.com/rocket/rocket3w.html
>
> This appears to be a well-kept secret in the SF world, as
> indicated by the book I am currently work-avoiding, which features
> a secret asteroid base only located by intelligence work,
>
> Are there any recent SF books that take the impossibility
> of stealth in space into account?
WJW's Dread Empire trilogy features a decent amount of military
tactics related to conducting a space-based war, and he pays
pretty good heed to the lack of stealth, including relativistic
arcs, decoys, and a small group of folks freezing their butts
off on an asteroid(?) while trying not to give off heat or
energy signatures while observing a strategic system.
Tony
John Schilling
Sullivan) wrote:
>DougL <lamper...@gmail.com> wrote:
>>On Jan 21, 1:02 am, phoe...@ofb.net (Damien Sullivan) wrote:
>>Even without that the intercept problem is utterly trivial compared to
>>the problem of accelerating the projectile in the first place. If you
>>can accelerate to 95% c then I can hit you with some trivial fraction
>>of the same mass accelerated to 5% c in the opposite direction.
>I don't think it's that easy.
>Let's be specific. The R-bombers accelerate a couple of light years
>away. This is visible for light-years, everyone knows they're coming,
>roughly how fast, and maybe even which planet in the solar system
>they're aiming at. But they're not that big, when they're done
>accelerating they run cold, and they can use cold jets to stealthily
>dodge laterally, or even add small amounts of imprecision to their
>direct velocity.
That's pretty much useless. An R-bomber with a 50% propulsion mass
fraction, using cold-gas helium from a carbon nanotube tank, can
manage an own-frame delta-V of roughly one kilometer per second.
If it's approaching at 0.95c, that corresponds to a divert angle
of 0.2 arc-seconds.
Since we know where the R-bomber started, and we know where the target
is, we only need to defend a 0.2 arc-second cone around the threat
axis.
>Their target is a planet. Big, visible, and on a known trajectory.
>Unless we invoke Paul Birch planets don't dodge. If it, or even most of
>its fragments, hit the planet thenm it delivers its 'payload' of kinetic
>energy.
>Your target is a cold R-bomber, possibly less than 100 meters in radius,
>stealthed against radar and not emitting much heat (AI crew), coming in
>at near lightspeed anywhere within a 6000 kilometer radius (I'm using
>the size of Earth.) Diverting this or blocking it early enough so that
>fragments miss the planet doesn't seem that trivial to me.
Neither does accelerating a stealthy, massive projectile to 0.95c in the
first place. You don't get to postulate an arbitrarily difficult and
expensive attack, then claim that because the defense isn't absolutely
trivial you have clearly devised an Unstoppable Superweapon.
>It can still do cold random dodges as it draws near, and emit low-mass
>films ahead of it to pre-react with low-density clouds you might have
>strewn in its path.
And this "pre-reaction" is going to be cold and stealthy? It, and
the subsequent reaction of your R-bomber blasting through the cloud
of debris from the pre-reaction, is going to be the signal that tells
the defender exactly where to concentrate his second line of defense.
>>Everything that makes you hard to hit applies, but an order of
>>magnitude or so worse, for you being able to see my shot and dodge or
>>block it.
>Don't need to dodge specific shots, just avoid being on a predictable
>trajectory. And the R-bomber has to block a 100 meter radius area, you
>have to block a 6000 kilometer raidus area.
The R-bomber has to block a 100 meter radius area with mass that it has
gone to the considerable trouble of accelerating up to 0.95 c. The
defender gets to use relatively cheap, dumb matter dispensed by ordinary
rocket, and it only needs to block a 0.02-arcsecond cone centered on
the hundred-meter hole you just blasted through his previous line of
defense.
You can try to fake him out by clearing multiple holes through the outer
defensive layers, but each of those holes is going to be harder for you
to make than it is for him to plug.
And since you're giving him months or years of warning along with that
fairly well-defined threat axis, he can set up many, many defensive
lines.
--
*John Schilling * "Anything worth doing, *
*Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" *
*Chief Scientist & General Partner * -13th Rule of Acquisition *
*White Elephant Research, LLC * "There is no substitute *
*John.Sc...@alumni.usc.edu * for success" *
*661-951-9107 or 661-275-6795 * -58th Rule of Acquisition *
Aaron Denney
> Aaron Denney <wno...@ofb.net> writes:
>
>>On 2008-01-21, James Gassaway <dtr...@sonic.net> wrote:
>>> Aaron Denney wrote:
>>>> On 2008-01-20, James Gassaway <dtr...@sonic.net> wrote:
>>>>> Third, we do not currently have full time-full sky (360 by 360)
>>>>> observation.
>>>>
>>>> 360 by 180. But that's an artifact of a not necessarily good
>>>> coordinate system. Say, rather, 4 pi steradian.
>>>
>>> You're assuming that no space-based attack can ever come from the sunlight
>>> side of the planet?
>
>>No, I'm assuming that longitude ranges from -180 to 180, and latitude
>>from -90 to 90. 360 x 180. This coordinate system isn't great because
>>a "square degree" near the pole is quite different than one near the
>>equator.
>
> I think you can avoid that inconvenience of wildly different
> `square degree' areas, at least, by using as your coordinate system the
> sine of the latitude and then the longitude in radians, although this
> doesn't do anything to avoid the odd effects that being near a pole will
> have on coordinates. Also I've never been able to figure out what if
> any name that projection has.
It's just cylindrical, restricted to the surface of a sphere. IIRC, it
helps, but not completely, because the radial coordinate changes.