Recommend
8 
 Thumb up
 Hide
50 Posts
1 , 2  Next »   | 

Diaspora» Forums » General

Subject: TANSIS: There Ain't No Stealth In Space rss

Your Tags: Add tags
Popular Tags: [View All]
John Reiher
United States
Kenmore
Washington
flag msg tools
designer
Avatar
mbmbmbmbmb
First, read There Ain't No Stealth In Space on the Atomic Rocket website before you come back with a "no, you're wrong" statement.

OK, in game this means that even T4 ships will be visible because their drive plume will be visible in the IR and X-Ray bands. Excluding T4 ships from the discussion, all other spacecraft will be visible within certain ranges using space-based sensors.

So that's the first free tag "There Ain't No Stealth In Space", usable on any spacecraft that is operational and moving through space. However, if a ship is coasting, then they are harder to spot, since they are only radiating life support heat and the ship's power plant. A much smaller signature.

That's the free tag "Not so silent, and not so deep." Usable by either side.

Now, TANSIS doesn't mean that you can't use camouflage, guile, and simple misdirection. Q-ships come into mind. One problem with your drive plume, is that its spectrum and temperature will indicate if the ship is using a Civspec drive versus a Milspec drive. Also, the plume temperature will indicate if the ship is pushing a full load or an empty shell.

This fact means you can't use a decoy. The spectrum and temperature will be for a small, light vehicle, not for a warship.

More tags and aspects:

"You can't hide your lying drive."
"No one here but us chickens."
"Wolf in sheep's clothing."
"Decoys are only for duck hunting."

And finally, most "civilized" systems, T1+, will have a System Navigation service. Nav Buoys will be in solar orbit, spaced out so that they can cover the whole system and their job is to track everything in space, and provide navigation beacons for incoming ships. And tell everyone else in system that you've arrived.

Free-tag: "Ground control to Major Tom."
4 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
John Reiher
United States
Kenmore
Washington
flag msg tools
designer
Avatar
mbmbmbmbmb
Halfjack wrote:
In Diaspora T4 is always your get out of jail free card--if the story is better with a T4 ship that radiates in no spectrum, then go there.

Well their ship may not radiate, but unless they have the magical inertialess drive, their drive plume is quite visible. If you suck all the heat out of the drive plume, you've also sucked out all the thrust as well.

I don't know, the magic heat dump aspect for a T4 ship to me is not at all realistic. If you can dump heat into another dimension, then you should be able to pull kinetic force from one and move about without using a fusion drive.

I'm a fan of Ken MacLeod and his transhuman stories. But even with his most outrageous hypertech, he still gives a nod to reality. He still abides by the law TANSTAAFL "There Ain't No Such Thing As A Free Lunch"

By dumping heat into another dimension, they are creating energy in that dimension and destroying heat in their dimension. They are breaking the first law of thermodynamics:

Energy can be neither created nor destroyed. It can only change forms.

So, to stay within the strictures of hard SF, they are not "dumping heat" they are exchanging heat for mass. Now the thermal output of a ship is not going to generate a lot of mass. 1 gram of matter gets you 15 ktons of energy. So we're talking grains of matter.

The second law pretty much guarantees that you can't get rid of all the heat your T4 ship generates: It can't get rid of the heat generated to get rid of the rest of the ship's heat. The T4 ship will never get a box full of heat on it's heat track, but that does not mean it doesn't radiate heat. It's just very little heat.

But the amount of heat is so low, you need a highly specialized, supercooled sensor to see the T4 ship against the 3° K cosmic background radiation.
2 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
Tim P
United States
Fayetteville
Arkansas
flag msg tools
Halfjack wrote:
T4 violates any physical law that suits the story. That's the reason it's there.

This means there is totally the possibility of a Firefox mission in our campaign.

http://en.wikipedia.org/wiki/Firefox_(film)
1 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
John Reiher
United States
Kenmore
Washington
flag msg tools
designer
Avatar
mbmbmbmbmb
Halfjack wrote:
T4 violates any physical law that suits the story. That's the reason it's there.

Well, I'm a hard core hard SF fan. So, I'll probably not break any physical laws with the T4 tech. I will use as a guide Indistinguishable from Magic by the late Dr. Robert Forward. Now that's T4 tech that not only obey's the physical laws, it picks them up and runs away with them.
1 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
Martijn Vos
Netherlands
flag msg tools
mbmbmbmbmb
I think T4 should allow stealth. Perhaps it manages to radiate its heat only in very specific directions (compare the angular sides of many modern stealth vehicles). That would make them very hard to detect.

When they're under thrust, the heat plume is still an issue, obviously. How long is that plume? Would it be possible to use a huge shield to cover it from prying eyes?

Also, TANSIS not withstanding, I'm wondering how feasible it really is to look everywhere at once. We 21st century humans certainly seem to be having some trouble tracking everything, although we have been getting noticeably better at it in recent years.

And of course you can still hide if you have a warm object behind you. There aren't many warm objects in space, and looking from multiple angles simultaneously will make it really hard to hide in front of one from all angles.

I'm now wondering how feasible it would be for an invasion fleet to deploy a huge cloud of hot gas as camouflage. It won't hide their arrival, but it might hide their size, number, speed, and other details. But I have no idea how feasible that really is. It'd be a cool idea, though.
1 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
Tim P
United States
Fayetteville
Arkansas
flag msg tools
mcvos wrote:

I'm now wondering how feasible it would be for an invasion fleet to deploy a huge cloud of hot gas as camouflage. It won't hide their arrival, but it might hide their size, number, speed, and other details. But I have no idea how feasible that really is. It'd be a cool idea, though.

Our group's night would be ended at the sophomoric laughter and reversion to grade school mentality that the thought of invasion fleets spewing huge clouds of hot gas would sadly but inevitably evoke.

On a serious note, I'm guessing the sheer scale that such a cloud would have to operate at would be extremely problematic. Gas doesn't have a lot of mass, but the volume required for storage would be pretty intense.
2 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
John Reiher
United States
Kenmore
Washington
flag msg tools
designer
Avatar
mbmbmbmbmb
mcvos wrote:
I think T4 should allow stealth. Perhaps it manages to radiate its heat only in very specific directions (compare the angular sides of many modern stealth vehicles). That would make them very hard to detect.

When they're under thrust, the heat plume is still an issue, obviously. How long is that plume? Would it be possible to use a huge shield to cover it from prying eyes?

I remember seeing a post/article about this in another group. I'll see if I can find that info.

Quote:
Also, TANSIS not withstanding, I'm wondering how feasible it really is to look everywhere at once. We 21st century humans certainly seem to be having some trouble tracking everything, although we have been getting noticeably better at it in recent years.

Indeed we are getting better at it:



Quote:
And of course you can still hide if you have a warm object behind you. There aren't many warm objects in space, and looking from multiple angles simultaneously will make it really hard to hide in front of one from all angles.

Well, to misquote Wrath of Khan, you show 2 dimensional thinking. Please define "in front of" when you're in 3 dimensional space and the people you're trying to hide from are at multiple angles and different locations in the star system?

About the only place I can think of to hide in is right inside a comet's tail, within spitting distance of the comet nucleus. Of course if you do that, you best have some damn tough armor as the comet dust and other debris beat the Hell out of your ship.

Quote:
I'm now wondering how feasible it would be for an invasion fleet to deploy a huge cloud of hot gas as camouflage. It won't hide their arrival, but it might hide their size, number, speed, and other details. But I have no idea how feasible that really is. It'd be a cool idea, though.

Beside the issue of that it would take megatons of gas to provide sufficient cover (hot or cold), is that the gas is not accelerating but your ships are. And if they are just coasting, you've just provided target practice for the defending system's kinetic weapons.

Besides, the gas will continue to expand until it's too thin to provide cover.
1 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
William Hostman
United States
Alsea
OR
flag msg tools
designer
I've been Banished to Oregon... Gaming in Corvallis, living in Alsea... Need gamers willing to try new things...
badge
The Splattered Imperium
Avatar
mbmbmbmbmb
Stealth tech works just fine in space. Better even than on planets.

Stealth tech involves redirection and minimalization of signature. Radar absorbtion and reflection, or making the return look like something else.

The temperature issue is the big one. Anything with people on it is an IR source. That's solved by a course that puts you between a suitable IR source and the target.

It's also reduced by a mirror-backed shield with minimal contact points... reflecting the IR from the ship proper away from target.

Note that either of these work against a cone shaped zone, not omnidirectionally.

Exhaust IR is the hardest thing to mask. But, unlike planes, one need not be producing exhaust. The current (unmanned) long range spacecraft have no exhaust to find... except when under thrust. And even then, it's not a bright IR plume, but a think IR cone, easily lost against a planet.

You set your course and coast, starting far enough out that you're below threshold on the detectors, and coast.

All in all, Atomic Rockets' essay is flawed in that it shows a misunderstanding of "stealth" and of thermos design. Stealth is not omnidirectional; there are certain angles and wavelengths that the stealth jets show up beautifully in.
 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
John Reiher
United States
Kenmore
Washington
flag msg tools
designer
Avatar
mbmbmbmbmb
aramis wrote:
Stealth tech works just fine in space. Better even than on planets.

Stealth tech involves redirection and minimalization of signature. Radar absorbtion and reflection, or making the return look like something else.

Well, if you're going to use RADAR or other active sensors, you might as well paint yourself fluorescent orange or that ugly lime green. If you use active sensors, you're making yourself a target.

Quote:
The temperature issue is the big one. Anything with people on it is an IR source. That's solved by a course that puts you between a suitable IR source and the target.

Well, first, you have to get into that position. And your target will watch you go all the way there. It's not like WWI and you're in your Sopwith Camel, diving on that Albatross out of the sun. Remember that this is hard SF. You have limited propellant, so you can't jink all over space, you pretty much have to plan out your attack and plot your courses and hope that you have enough remass to get to a safe port after you engage the enemy.

You want to hide? Wait until your target gets to a planet. Then you can hide behind the planet and launch ordinance in retrograde orbits for maximum impact.

Combat in deep space is almost 100% lethal for both sides, especially if they expend all their delta-V in trying to get into a better position.

Quote:
It's also reduced by a mirror-backed shield with minimal contact points... reflecting the IR from the ship proper away from target.


You know, a radiator and cooling system concentrates and redirects internal heat much better than letting your hull simply radiate to vacuum. In any case, your "shield" will get hot either from the sunlight falling on it or simple from absorbing the IR it's shielding.

Quote:
Note that either of these work against a cone shaped zone, not omnidirectionally.

And only against one set of eyes. If you're facing more than one opponent, they will work together and correlate their information and target your ship.

Quote:
Exhaust IR is the hardest thing to mask. But, unlike planes, one need not be producing exhaust. The current (unmanned) long range spacecraft have no exhaust to find... except when under thrust. And even then, it's not a bright IR plume, but a think IR cone, easily lost against a planet.

You set your course and coast, starting far enough out that you're below threshold on the detectors, and coast.

And you pray that they didn't spot your initial burn and get a track on you. Remember, once you start coasting, Sir Isaac Newton is now driving your ship and that course is entirely predictable.

Hiding your drive is going to be kinda hard. As a general rule, anything that can keep thrusting at more than one gee for more than a day is a little sun pouring tens of terawatts in space. Or even hundred thousands of terawatts. The total energy consumption of Earth some years ago was around 15-20 terawatts, for comparison.

You're not going to hide that kind of output. Your ship will be an X-Ray star in the sky, a very bright one in fact. The only place that won't see those X-Rays is directly in front of the drive, behind your tungsten drive shield.

Quote:
All in all, Atomic Rockets' essay is flawed in that it shows a misunderstanding of "stealth" and of thermos design. Stealth is not omnidirectional; there are certain angles and wavelengths that the stealth jets show up beautifully in.

You're not the first person to say it's flawed, but so far it has stood the test of time. I never knew how much heat we generate with all our technology until I saw the numbers NASA put out for the ISS. It's a major issue if their cooling systems crash. Fusion drives are little suns, they are just as hard to hide.

I'm not the one to say never, but stealth is never going to be anything like what you see on TV. The best stealth is showing up in port, looking like a merchant ship, get your raiders on board the hight port, grab the goodies, not kill anyone, but make sure they can't raise an alarm, and then run for the slipknot and bug out as fast as you can.

At this point, I'd like to point out that you don't have random battles in space. You're fighting over territory, planets, asteroids and other such stuff. What's your goal in engaging in combat?

If you answer "to destroy the enemy ship" then you've lost the battle. The smart opponent will then choose his battlefield and time of battle to his best advantage. Think about it from the point of view of an orbital battle: Different orbits could be tagged with things like "Orbital Asteroid Killer Lasers", "Kinetic Kill Coilguns" and other nastiness, that the defender can freely tag and waste an opponent.

Hey Brad, that sounds like another minigame: Orbital combat. That's where most of your battles will take place, not in deep space. Let me think about that.
4 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
bobafetthotmail
msg tools
Quote:
Stealth tech works just fine in space. Better even than on planets.
I beg to differ. Being in space is like being in the darkest night on an entirely flat floor. If you light up a match you don't see a damn thing, but anyone in a very long range range can notice it.
Like those snipers in the old days, shooting at lit cigarettes.

On the ground you have loads of random clutter to hide into. If you were lighting a match in the middle of a jungle/city/varied terrain, much less people around you will see that.

Quote:
The problem with using thermos design to make space craft is that you kill you crew. You must get rid of the heat waste from life support and there must be heat waste. Or everyone dies.

Robots stealth ships, on the other hand....
Except that computers (and bot brains) do generate heat.
That your power plant generates heat.
That your weapons generate heat.
That your engines generate (loads of) heat.

About anything that does something needing power generates heat because it isn't 100% efficient.

And the main problem with heat is not that you cook the crew, but that you meltdown the reactor, fry the computers, overheat the weapons (especially lasers), melt the engines.

Quote:
The temperature issue is the big one. Anything with people on it is an IR source. That's solved by a course that puts you between a suitable IR source and the target.
So it is the sun. But frankly you can't expect to have always the sun "behind you" (from the target's viewpoint).

Quote:
It's also reduced by a mirror-backed shield with minimal contact points... reflecting the IR from the ship proper away from target.
So you just created a gigantic thing that acts odd and will stand out on other kinds of scans (optic) to hide your ship on IR.

Not to sound too geeky, but the general wisdom is to place your radiators "edge on" the enemy. This way the IR you radiate away with them is emitted perpendicularly to your vector and the taget doesn't see these emissions. Works if the target is only in one direction though. And anything irradiated from your hull will still be detectable (a good reason to insulate it very well and use only radiators to cool it off).

Quote:
Exhaust IR is the hardest thing to mask. But, unlike planes, one need not be producing exhaust. The current (unmanned) long range spacecraft have no exhaust to find... except when under thrust. And even then, it's not a bright IR plume, but a think IR cone, easily lost against a planet.
The problem of this approach is that is terribly slow. Probes generally take multiple years and use gravity assists from planets instead of thrusting.

But that's an engine problem. Most engines cannot manage to accelerate the craft over a certain speed, due to fuel efficiency. Chemical rockets can't manage you to go faster than around 4-5 km per second (a little more if you multistage ala Saturn V), and that's a glacial pace for anything going more far than the Moon.
But they are rather brawny and they need little time to build up speed.

Most other engines are very fuel efficient (ion engines, VASIMR), but their acceleration plain sucks (you don't even notice it). Being very fuel efficient, they can keep thrusting for months, and reach speeds that chemical rockets only dream about.

But the problem of most today's "very fuel efficient engines" is that they aren't self-powered. They just drink ludicrous amounts of energy to throw an inert fuel (propellant) very fast, (and energy consumption isn't an engineering limit, it is a fundamental limit of such engines).
Nuclear reactors aren't really suited for space. They are heavy (radioactives fissing are heavy, the shielding needed for crew and electronics's safety is heavy, the radiators needed to dump the waste heat are ludicrously big and thus heavy).

Theoretically only self-powered engines can do better.
So we have fusion torches, fusing something and using the energy from fusion to heat the propellant into super-hot plasma and shoot it out of the thrust ports of the craft with magnetic nozzles (anything phisical would be instantly-vapourized).

Still, space is big, so let's make an example:
I'll get a spacecraft with a non-descript engine able to thrust at 0.3 gees (a "gee" is an earth gravity), and fuel tanks that hold 180 km/s of delta-v (change in speed. For comparison, the best chemical rocket has around 6 km/s).

Now, this thingy departs from Earth and goes to Mars.
Being brawny, it can ignore orbital mechanics and just burn up to speed, cruise and decelerate at arrival.

Having 180 km/s delta-v means that I can get up to 90 km/s of speed, cruise on my way to mars, and then decelerate to 0.

At 0.3 gees of acceleration (3 m/s2) that ship will need 8 hours to get up to speed. While thrusting, it is pouring a whopping 450 GW in the exaust. It's like if it was detonating a Davy Crocket per second behind it. For 8 hours. And it cannot hide behind the planet for long, because after 15 minutes has reached the escape velocity and is already drifing in interplanetary space.

At 90 km/s will reach mars in one week if Mars is in the closest spot or two months if it is in the farthest. Reaching other planets is much more boring at this speed, it's around 1 AU per three weeks.

You may say it is too slow, so let's pimp it a little.
Assuming a more fuel-efficient engine (ten times the above) with the same acceleration, the same fuel tanks will give me 1800 km/s of delta v now.

With this baby I can reach jupiter (medium distance) in two weeks, Saturn in three. But let's look at how bright is my plume now. This engine is spitting 4.5 TW, or around a third of the current total human race's energy consumption, or around 1 kiloton of TNT per second. And the burn time is now ten times as high, around three days.

You think you can hide it? Be my guest.arrrh
1 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
Brian York
United States
Baltimore
Maryland
flag msg tools
The other thing that makes it harder to hide (if using a drive), but easier (otherwise) is where the slipknots are located. By definition, if you're appearing 5AU above the plane of the ecliptic, then you're not hiding behind the sun. And, being that far above the plane of the ecliptic, there's not a lot else to hide behind either. Thus it's going to be nasty trying to hide drive plumes.

That said, you can *also* bet that by far most of the possible detectors you're facing are in a known direction (until and unless the host system decides to be spoilsports and puts a small sky-survey IR scope out farther than the slipknot, of course). And if your civilization can't afford six Hubble-equivalents (only designed for fast all-sky infrared surveys, so probably based around wide-field IR detectors), then the incoming ship probably doesn't have to worry too much about hiding anyway. Why six? So you can have them in an orbit perpendicular to the ecliptic such that there's *always* at least one looking down on each slipknot. You could do it with three, but six lets you position them a bit closer and still maintain coverage.
1 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
William Hostman
United States
Alsea
OR
flag msg tools
designer
I've been Banished to Oregon... Gaming in Corvallis, living in Alsea... Need gamers willing to try new things...
badge
The Splattered Imperium
Avatar
mbmbmbmbmb
Halfjack wrote:
The problem with using thermos design to make space craft is that you kill you crew. You must get rid of the heat waste from life support and there must be heat waste. Or everyone dies.

Robots stealth ships, on the other hand....

You're making the EXACT same error that Winch does: presuming 360° protection.

For the IR, you only have to prevent the target from seeing it. You put all your radiators in the aft, and the IR Reflective material on the aft side of the fore-shield, and you have just massively reduced your IR signature in a HUGE cone. As long as that cone is toward the sensors you need to defeat, and the cone itself is constructed to scatter and/or absorb radar, you've just made yourself much lower signature vs those targets. Yes, it does increase your IR signature in the aft view, but stealth does work.

Crude ascii art follows.

\
r-==-)
/
 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
John Reiher
United States
Kenmore
Washington
flag msg tools
designer
Avatar
mbmbmbmbmb
aramis wrote:
Halfjack wrote:
The problem with using thermos design to make space craft is that you kill you crew. You must get rid of the heat waste from life support and there must be heat waste. Or everyone dies.

Robots stealth ships, on the other hand....

You're making the EXACT same error that Winch does: presuming 360° protection.

For the IR, you only have to prevent the target from seeing it. You put all your radiators in the aft, and the IR Reflective material on the aft side of the fore-shield, and you have just massively reduced your IR signature in a HUGE cone. As long as that cone is toward the sensors you need to defeat, and the cone itself is constructed to scatter and/or absorb radar, you've just made yourself much lower signature vs those targets. Yes, it does increase your IR signature in the aft view, but stealth does work.

Crude ascii art follows.

\
r-==-)
/

First off, how did you get into this position? You just didn't appear in situ, you had to travel to get into this position.

Also, there are some problems with your setup:

Problem #1 is radiators to the aft. Do have any idea of how big your radiator has to be to effectively radiate the heat your ship and drive output? Well, visit the Atomic Rocket Page on Radiators, and a radiator to handle a measly 150 gigawatts is 90 meters on a side. That's a football field length sized object. And that's only for 150 gigawatts. I'll leave it as an exercise for the interested to figure out how big it would be for 4.5 terawatts.

Problem #2 is that you have to turn your radiator sideways to your drive, otherwise your drive plume will radiate the radiator, overheating your ship. Since it has to be sideways, you can't hide it from your target.

Problem #3 given how big your radiator is, your IR shield would have to be humungous. Also, what's it made of? Aerogel? Ceramics? And even if you paint it black, it will shine in sunlight. Remember, the moon is the color of asphalt, and Iapetus' dark side is even darker and we can see it just fine. So you just put up a big, shiny reflector on your ship. Might as well paint a target on it.

Problem #4 is that there is no such thing as the perfect RADAR reflector/absorber. In fact, if it absorbs RADAR, it probably absorbs IR. Especially if you paint it black. So, unless you have the sun at your back, it's soaking up the solar insolation and getting nice and hot. There's a reason why spacecraft are white or covered in gold foil.

All you've done is add a lot of extra mass to your spacecraft, force yourself to put a bigger drive on it, and not have much mass left over, even at a 5:1 mass ratio, for weapons.

2 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
bobafetthotmail
msg tools
aramis wrote:
For the IR, you only have to prevent the target from seeing it.
So you just created a gigantic thing that acts odd and will stand out on other kinds of scans (optic, ladar) to hide your ship on IR.

Not to mention that most sysems have a feeble amount of IR-emitting dust on the ecliptic plane (it is used to detect where such plane is by astronomers), and your big black "hole" on the IR emission of the dust on the eclyptic plane will give you away.

The general wisdom is to place your radiators "edge on" the enemy. This way the IR you radiate away with them is emitted perpendicularly to your vector and the taget doesn't see these emissions. Works if the target is only in one direction though. And anything irradiated from your hull will still be detectable (a good reason to insulate it very well and use only radiators to cool it off).

But generally IR emissions are a concern for tactical ranges, If you are talking of interplanetary distances, then your drive plume will easily give you away.

polemarkh wrote:
And if your civilization can't afford six Hubble-equivalents.
Not to sound nitpicky, but Hubble would be overkill (and it was the center of one of the most unlucky series of events of the entire history of space exploration, rising up the costs to have it operational much above the cost of building it).
You don't need to locate engine plumes in other star systems, nor to see other galaxies, like Hubble was designed to do.

Medium-size ground-based observatories are more than enough.
A few scattered around to have full sky coverage and some spares, and you are set. Automatic sky survey is fast (hours).

Quote:
I'll leave it as an exercise for the interested to figure out how big it would be for 4.5 terawatts
While those 4.5 terawats were exaust power (power of the exaust) in my example above, the baby spitting out so much power won't get anywhere close to 50% efficiency (I've yet to see anything getting over 40% in energy conversion). So, to get 4.5 terawatts of exaust power, you will have a 10+ terawatts fusion torch that must dump somewhere all the terawatts not going into the thrust.

Most concepts use an open chamber, where the only thing worth protecting are the supercooled magnets that focus and exaust the plasma.
All radiations must be free to escape, and a huge radiator must keep magnets at around 4 kelvins (they are superconductors) even when heavily "shined on" by your small sun.
A pic showing what I mean for "open chamber". The craft in the pic come from a game where they just said that the engine dumped all the waste heat in the propellant (what most rockets do nowadays). So they don't have gigantic radiators. That's also called cheating, because it is not possible to do it at so high power levels.

Orion drive ships almost seem easy to do in comparison.
2 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
William Hostman
United States
Alsea
OR
flag msg tools
designer
I've been Banished to Oregon... Gaming in Corvallis, living in Alsea... Need gamers willing to try new things...
badge
The Splattered Imperium
Avatar
mbmbmbmbmb
Drive plume is IRRELEVANT in most cases; if you're maneuvering, rather than coasting, inbound, then you've already got bigger issues. Drive plumes are anti-stealth; stealth is not about attack; it's about keeping yourself below threshold from particular targets in the operational regime.

Best example: the stealth bomber shows up on radar. But not at full size; it shows up about the size of a waterfowl, and is below detection threshold. Until it opens the bomb bays. Then it looks like a trailer full of bombs... jumping in size by a factor of several thousand times.

Many asteroids are above background temp; we can hardly detect them. Only reason we detect them easily is that there are SO many of them.

Radio, IR, and other EM radiation simply has to be kept below the point where the target picks up more of yours than of background. (This means no using 1-10Ghz...)

Ladar is a lousy search sensor, but a great pinpoint system. Radar is incredibly good sweep; not so good detail, because unlike ladar, one can easily rig a 30-60° radar ping; a ladar ping is limited in range not just by laser strength, but also sweep accuracy, and it's beam is measured in arc-minutes or less.

Just like current naval vessels carry 2-10 different radar sensors; one is a low resolution navigational; it will pick up a rowboat or piper, but not a missile. Then there are the targeting radars, with resolutions in the 1cm range, on the CIWS, and the main targeting radars with a 1-2° arc, but incredibly accurate range and resolution of a few cm, tied to the gunnery systems.

Ladar is a targeting sensor, not a sweep nor search sensor. A "What's that blip?" answerer. Like Hubble, the field of view is too narrow.

Optical scanning is also very low scan angle or very low resolution; to get both, it becomes impossibly large. Further, due to the low view angle, it's usually part of time-intensive search patterns. Sure, we could use 6 hubble units to search the sky; assuming 1 image per second, you are only going to get each patch of sky once a day. And then, you still have to process the information to figure out if indeed something moved.

Stealth doesn't get you to orbit; it gets you in to the point you're a threat, in a slow patient mode. It's about directing your emissions away from the enemy.

And the shield doesn't need to be huge to be effective. It needs to merely provide a sufficient angle to allow closing to the target zone's patrol point; 5° coverage should be more than adequate for all but the final close; at that point, one goes hot anyway.
1 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
Brian York
United States
Baltimore
Maryland
flag msg tools
bobafetthotmail wrote:
Not to sound nitpicky, but Hubble would be overkill (and it was the center of one of the most unlucky series of events of the entire history of space exploration, rising up the costs to have it operational much above the cost of building it).
You don't need to locate engine plumes in other star systems, nor to see other galaxies, like Hubble was designed to do.

Not a problem (and yes, indeed, I do know this -- I just tend to use Hubble as an example because my day job involves working with it). To be fair, I probably should have used a combination of Hubble and JWST (or another infrared scope) as my real example. The idea would be that, because the slipknots are relatively small points (by which I mean, subtend rather small angles when viewed from planetary distance), what you'd probably want to do is just have a couple of detectors (say one UV photon-counter and one IR doing periodic readouts and occasional flushes) just staring at that part of the sky.

aramis wrote:
Drive plume is IRRELEVANT in most cases; if you're maneuvering, rather than coasting, inbound, then you've already got bigger issues. Drive plumes are anti-stealth; stealth is not about attack; it's about keeping yourself below threshold from particular targets in the operational regime.

The issue here is that, in this setting, you appear in one of two well-defined zones, and you *have* to maneuver if you want to actually get to the inhabited planet. Not to mention that, *because* you know where an inbound ship will appear, you don't need to survey the whole sky. You just need to be able to look at two places from opposite directions.

aramis wrote:
Many asteroids are above background temp; we can hardly detect them. Only reason we detect them easily is that there are SO many of them.

I'm nitpicking a bit here, but really the reason we detect so many asteroids is that we're not *trying* to detect them in the IR, because we know that's not the best way (because they're not appreciably hotter than background). Thus, we look for asteroids in the optical, or by opportunistic transits.

Spacecraft, on the other hand, *are* appreciably hotter than background, at least from some directions. And when you know where they're going to appear, and when they *have* to maneuver to get from there to their destination, the job is a lot easier.

aramis wrote:
Optical scanning is also very low scan angle or very low resolution; to get both, it becomes impossibly large. Further, due to the low view angle, it's usually part of time-intensive search patterns. Sure, we could use 6 hubble units to search the sky; assuming 1 image per second, you are only going to get each patch of sky once a day. And then, you still have to process the information to figure out if indeed something moved.

See above re. known starting locations. Also, note that the easiest thing to do would be to do a wide-FOV all-sky-survey once/day (and it wouldn't be too long before you'd have identified all of the stuff that's bright enough to show up in your all-sky-survey), and then take a careful look at anything *new* that shows up (or that transits stars, etc.). If you make sure you have the appropriate limiting magnitudes, it should be possible. Sure, it'll take a fair bit of computational power, but then we *are* talking about the far future here.
3 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
John Reiher
United States
Kenmore
Washington
flag msg tools
designer
Avatar
mbmbmbmbmb
aramis wrote:
Drive plume is IRRELEVANT in most cases; if you're maneuvering, rather than coasting, inbound, then you've already got bigger issues. Drive plumes are anti-stealth; stealth is not about attack; it's about keeping yourself below threshold from particular targets in the operational regime.

Best example: the stealth bomber shows up on radar. But not at full size; it shows up about the size of a waterfowl, and is below detection threshold. Until it opens the bomb bays. Then it looks like a trailer full of bombs... jumping in size by a factor of several thousand times.

That's a bad example, because the B-2 launches from over the horizon, out of sight of the target. Until it crests the horizon, the target doesn't know it's there.

But in space, especially with T1+ cultures, you see the ship fire up its drives, you watch it do its initial burn and you get a track on its course. The spectra of the ship's drive will tell you if it's cargo vessel or a lighter warship. So you know where it's going and you know what it's going to intersect. If it's you, you make a course correction. If you're really the target, the unknown ship will make a course correction to intercept you. As you said, drive plumes are not stealthy. They telegraph your movements and where you're going to.

Quote:
Many asteroids are above background temp; we can hardly detect them. Only reason we detect them easily is that there are SO many of them.

We're getting much better at spotting them because we're getting much better at spotting them because we have to. Only recently have we've been able to see Ceres' disk. But right now, no one believes we'll be hit by an asteroid any time soon. So what needs to happen is either the Moon gets walloped with one or we get hit by a big enough one that everyone sits up and screams bloody murder that we Have To Do Something about the Asteroid Menace. Then you'll see a lot more space based telescopes put up to spot them durn asteroids long before they become a menace.

Quote:
[ snippage ]

Stealth doesn't get you to orbit; it gets you in to the point you're a threat, in a slow patient mode. It's about directing your emissions away from the enemy.

And the shield doesn't need to be huge to be effective. It needs to merely provide a sufficient angle to allow closing to the target zone's patrol point; 5° coverage should be more than adequate for all but the final close; at that point, one goes hot anyway.

You seem to be basing all your arguments on the engagement portion of your attack. The rest of us are pointing out that that's worthless.

Let me ask you a question: Where is this engagement taking place? What's the range of this engagement? Where are you going after this engagement?

You're also assuming single enemy. Why? You've created a warship designed to take on a single vessel. That's never going to happen. All the target ship has to do is launch his missiles and once they get outside the shadow cone you've created, they can see you ship. Primarily because you've designed it to be very bright in the IR to the rear of the ship, so it's now a beacon.

These are smart missiles, (why carry any other kind?) and they relay your position and now I have a target. You now have to dodge my missiles, which are coming from 360°, and in the process expose yourself to my ship. More missiles, more dodging... eventually one side or the other is destroyed or disabled.

More than likely your combat is not going to take place in deep space, it's going to take place in orbit about a planet. All your stealth doesn't work silhouetted against a planet.

If it's a friendly planet, the defender will have satellites in orbit that will report your position, but not the defender's. He has true stealth, he'll try to stay out of sight on the other side of the planet. He'll launch kinetics and other nasties to engage your defenses and maybe take your ship out with a lucky hit with a retrograde orbit smart kinetic round.

I really don't see a need for stealth in space. It's not going to last, since when you start firing your weapons you've given away your position. If you have to do a course correction, that will be visible. The engagement ranges are such that if your warship had a porthole, (real warships don't have portholes, weakens the hull), you would not be able to see the other ship, other than as a point of light.

As to why space combat will take place mainly in orbit, it's because the defenders will have the advantage. Unless you plan to turn your ships into impactors and bombard the planet, you have to turn around and decelerate to make orbit. Which means unless you have sensors out on long booms, you can't see anything through your plume.

And that's when the defenders launch their first wave of missiles at you. Now you have to decelerate and dodge, and sadly, your defensive lasers have to shoot through your drive plume, unless you turn off your drive to fire the missiles. But if you turn off your drive, you now have to overburn your drive to make orbit.

We can play this game all day long, and we're not going to convince you that stealth in space isn't possible or practical. I look at is as extra mass on your ship that's not going to do anything useful.

Your version of stealth only works if you can convince your target not to move, not have other ships nearby that can spot for him, and that he's ignored you completely until you've somehow snuck up on him, even though everyone has seen you fire up your drive, head towards him, decelerate, and then turn around say "you can't see me". (If you're not decelerating, then unless your chasing him, you get one shot at him, and then you've shot past him and he can now see your rear end and target that.)

If you're chasing him, then he can drop stuff to make your life miserable. Like missiles. He can kick them out without lighting them and just have them tumble until they exit your "stealth shadow" and then they see your drive, your radiator, everything. They lock on, fire up their drives and tell the target "he's over there." And now your ship has to dodge or do something to prevent those missiles from hitting you and the missiles the target just launched based on the targeting info from the first set of missiles.

Stealth? What stealth?
4 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
bobafetthotmail
msg tools
aramis wrote:
Drive plume is IRRELEVANT in most cases; if you're maneuvering, rather than coasting, inbound, then you've already got bigger issues. Drive plumes are anti-stealth;
The problem with drive plumes is at the beginning of your voyage.
You can't really hide your engine plume (assuming engines with decent performance) and unless you use murderous accelerations (10+ gees), even a trip to mars requires hours of continuous burn.

This means that they can spot you and write down your course. Then, while you are coasting you aren't maneuvering with your main engine, so you cannot really get that much far from their prediction.

At this point stealthing the craft's cruise is irrelevant, because they know your approximate ETA and your approximate course.
You can hope to throw off their targeting systems for a while, but they know you are paying a visit.

Quote:
Best example: the stealth bomber shows up on radar. But not at full size; it shows up about the size of a waterfowl, and is below detection threshold. Until it opens the bomb bays. Then it looks like a trailer full of bombs... jumping in size by a factor of several thousand times.
Stealth 'bommers can be easily spotted by over-the-horizon radars, because the radar pulse comes from above (instead than from the surface) and the bommer can't be designed to baffle both. The same goes for f22.
But really, who can afford decent over-the-horizon radars? US, Russia, China. Are they going to war against each other any time soon? No. So it is a "stealth enough" plane.

polemarkh wrote:
The idea would be that, because the slipknots are relatively small points (by which I mean, subtend rather small angles when viewed from planetary distance), what you'd probably want to do is just have a couple of detectors (say one UV photon-counter and one IR doing periodic readouts and occasional flushes) just staring at that part of the sky.
A textbook smart move. Jump Points are supposed to be obvious chokepoints after all.
Without Jump Points (and point-to-point FTL), you could aim telescopes at planets, and at any enemy base (no secret bases, because the first craft getting there will be spotted and tracked until arrival, and the base thus discovered)
3 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
フィル
Australia
Ashfield
NSW
flag msg tools
designer
badge
I am the wasp / that burrows in! I am the shriek / of twilight din!
Avatar
mbmbmb
Why do I feel like I've accidentally walked into a comic book store?
6 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
William Hostman
United States
Alsea
OR
flag msg tools
designer
I've been Banished to Oregon... Gaming in Corvallis, living in Alsea... Need gamers willing to try new things...
badge
The Splattered Imperium
Avatar
mbmbmbmbmb
In Diaspora's setup, stealth essentially favors the defender... the defender can have stuff on parabolic long term orbits that is set to watch but not be readily seen from one or the other slipknot. Which means also that, when it's relevant, having more detailed information. In short, if the locals have any sense of paranoia, you're going to be brutally surprised... because the ships on patrol are likely NOT burning until they decide you're a threat.

2 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
bobafetthotmail
msg tools
aramis wrote:
In short, if the locals have any sense of paranoia, you're going to be brutally surprised... because the ships on patrol are likely NOT burning until they decide you're a threat.
Yeah, this is pretty much what would happen in real life too.
Assuming the attacker comes from the jump point, of course.
Otherwise both see the other doing his businness.
That would be the death of space pirates.
Thankfully with jump points you can have pirates waiting for you with engines cold too (assuming the system hasn't a strong government able to hunt them down on its own). Doing their businness fast and then jumping away before you can catch them.

But anyway, these "course and ETA" about ships and stuff going around your system will be kept either as military intelligence or Space Traffic Control (a little like with airplanes today), the average freighter or liner won't have this info at hand. Further helping pirates.

IR emissions become relevant only at 5 to ten times or so the weapon range (which is awesome by earth standards, but still nearly nothing if compared to interplanetary distances), otherwise you need a so badass telescope with so long exposures that only a dedicated defensive installation can hope to track you down.
3 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
John Reiher
United States
Kenmore
Washington
flag msg tools
designer
Avatar
mbmbmbmbmb
bobafetthotmail wrote:
Thankfully with jump points you can have pirates waiting for you with engines cold too (assuming the system hasn't a strong government able to hunt them down on its own). Doing their businness fast and then jumping away before you can catch them.

Well, there's the problem that the slipknot is 5AU above or below the system's barycenter, so you just can't "wait for someone" to come out of the slipknot. You'd be in a near-stellar polar orbit, hopefully not getting too close to the system's primary.

Now, if slipknots are like Lagrange Points, you could orbit within the point. That also means that there may be garbage in the slipknot, as it would be a natural collector of debris and stuff. That would make exiting a slipknot dangerous, and you'd want to kill as much of your velocity before you slipped.

Since there is no mention of this in the rules, I'd say no, you can't "hang around" the slipknot without burning your drive to maintain position.

Quote:
But anyway, these "course and ETA" about ships and stuff going around your system will be kept either as military intelligence or Space Traffic Control (a little like with airplanes today), the average freighter or liner won't have this info at hand. Further helping pirates.

It really depends. Doing a google search on flight locator, I found a Google Earth hack that let you do just that, follow a flight. It wouldn't be that hard to expand that to show you all the flights in the air. At least commercial flights.

I think it really depends on the nature of the local government. Is it under one single government or is it balkanized? Is there a strong independent movement or a repressive government? That will determine if flight data will be available.

If the local control of the system nav data is in the hands of an entrepreneur, then it's for sale, probably with different levels of access at increasing prices.

Quote:
IR emissions become relevant only at 5 to ten times or so the weapon range (which is awesome by earth standards, but still nearly nothing if compared to interplanetary distances), otherwise you need a so badass telescope with so long exposures that only a dedicated defensive installation can hope to track you down.

Or you just have lots of average nav buoys throughout the system, so that no one place is more than .5 AU from one or more buoys.
3 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
Matthew M
United States
New Haven
Connecticut
flag msg tools
admin
8/8 FREE, PROTECTED
badge
513ers Assemble!
Avatar
mbmbmbmbmb
Kedamono wrote:

Since there is no mention of this in the rules, I'd say no, you can't "hang around" the slipknot without burning your drive to maintain position.

There is mention of it in the Slipknot Stations sidebar on page 20. T2 stations need constant thrust to stay in the vicinity. T3 stations can be sustained with minimal effort. T4 stations seem to hang by the slipknot while breaking the rules of physics as we (our T-1 selves) understand them.

-MMM
2 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
John Reiher
United States
Kenmore
Washington
flag msg tools
designer
Avatar
mbmbmbmbmb
Thanks Matthew. I've read the PDF, but it's not easy to read, even on my 27 inch screen. So, I was right, you can hang around the slipknot by burning fuel.
1 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
Martijn Vos
Netherlands
flag msg tools
mbmbmbmbmb
bobafetthotmail wrote:

Still, space is big, so let's make an example:
I'll get a spacecraft with a non-descript engine able to thrust at 0.3 gees (a "gee" is an earth gravity), and fuel tanks that hold 180 km/s of delta-v (change in speed. For comparison, the best chemical rocket has around 6 km/s).

Now, this thingy departs from Earth and goes to Mars.
Being brawny, it can ignore orbital mechanics and just burn up to speed, cruise and decelerate at arrival.

Having 180 km/s delta-v means that I can get up to 90 km/s of speed, cruise on my way to mars, and then decelerate to 0.

At 0.3 gees of acceleration (3 m/s2) that ship will need 8 hours to get up to speed. While thrusting, it is pouring a whopping 450 GW in the exaust. It's like if it was detonating a Davy Crocket per second behind it. For 8 hours. And it cannot hide behind the planet for long, because after 15 minutes has reached the escape velocity and is already drifing in interplanetary space.

At 90 km/s will reach mars in one week if Mars is in the closest spot or two months if it is in the farthest. Reaching other planets is much more boring at this speed, it's around 1 AU per three weeks.

You may say it is too slow, so let's pimp it a little.
Assuming a more fuel-efficient engine (ten times the above) with the same acceleration, the same fuel tanks will give me 1800 km/s of delta v now.

With this baby I can reach jupiter (medium distance) in two weeks, Saturn in three. But let's look at how bright is my plume now. This engine is spitting 4.5 TW,
Your example doesn't add up. If your acceleration is the same, how can the power of the engine suddenly have multiplied by 10? Also, all of this depends on your unspecified mass, which is a rather important factor here.

Perhaps you should fill out the example a bit more, so we can see how you arrived at these numbers. Because at the moment, they don't mean much.

Actually I think I can guess: You're saving fuel by throwing your propellant out the back 10 times as fast.

So let's say we want to accelerate 1000 kg at 1m/s^2 by throwing 1 gram of mass out the back per second. Impulse of the propellant needs to be the same, so we need to throw it at 10^6 m/s, giving it 0.5*10^-3*10^12=500MJ of kinetic energy. Per second, so that's 500 MW.

Make our spaceship 10 tons (10 times as heavy, and 10 times as fuel efficient), and we need to throw the propellant at 10^7 m/s, giving it 50GJ of kinetic energy. 100 times as much. So power required goes up by the square of our fuel efficiency with this kind of engine.

Of course the power generation is never 100% efficient, so you lose some as heat. This heats up your ship, and is detectable as IR. How much? Well, that depends on how efficient it is.

But drive your drive plume, isn't that just tiny bits of mass going really really fast in the same direction? They're not necessarily hot, are they? Of course heating them up is a simple way to accelerate your propellant, but it's not a very efficient, nor is it the only way.
1 
 Thumb up
 tip
 Hide
  • [+] Dice rolls
1 , 2  Next »   |