Superconductors, Stealth vs. ECM/ECCM in Space

[Junghalli]

Would it be possible (I'm not saying in any way easily feasible, just possible) to use a laser as your means of propulsion (photon momentum) to prevent your reaction mass giving you away, and to put your engine at the focal point of a large parabolic infrared light mirror so that all the infrared light from waste heat was directed in a single direction (ideally, the same one as the laser)? Of course you'll never get it to be perfect, but I wonder if you could get it quiet enough to make it worth it.

Could work in theory, but a photon drive is really low thrust. 300 megawatts per newton IIRC.

[Beowulf]

Because if the drone is have the same signature as your ship, it's going to have to weigh the same as your ship. Otherwise the emission signature of the drone's drive is going to be different than you.

Since when can we magically detect the mass of a distant drone? All we can see is light coming from it, and it's not going to produce enough gravitational effect on its surroundings to derive it from the movement of planetary bodies. Are you saying that the mass has to be the same so that the light and heat radiated from it is the same? Why can't you simply actively emit more light in the direction of the sensor?

You can't detect the mass, but you can infer it from the drive temperature, mass flow, and doppler shift. You can't just have the decoy emit the signature, because all that information comes from the drive plume, which is going to be much, much larger than any practical decoy. It'll come from the wrong place, and can therefore be ignored.

[Darth Wong]

Because if the drone is have the same signature as your ship, it's going to have to weigh the same as your ship. Otherwise the emission signature of the drone's drive is going to be different than you.

Since when can we magically detect the mass of a distant drone? All we can see is light coming from it, and it's not going to produce enough gravitational effect on its surroundings to derive it from the movement of planetary bodies. Are you saying that the mass has to be the same so that the light and heat radiated from it is the same? Why can't you simply actively emit more light in the direction of the sensor?

You can't detect the mass, but you can infer it from the drive temperature, mass flow, and doppler shift. You can't just have the decoy emit the signature, because all that information comes from the drive plume, which is going to be much, much larger than any practical decoy. It'll come from the wrong place, and can therefore be ignored.

That depends on how far away these targets are, and how huge the telescopes are. If you're using gigantic telescopes you can see in greater resolution, but you can't sweep those suckers around like a flashlight either, which limits your scan speed and creates its own problems. You're assuming perfect resolution; no ECM solution has to be perfect. It only has to overcome the inherent limitations of the sensor technology.

[Sky Captain]

What if you do your burn on the other side of the planet in a way planet is likely to be between your ships and known locations of enemy sensor platforms.
Let`s say a fleet from Jupiter`s colonies want to attack Mars. They do their main burn while Jupiter is between them and known Martian sensor platforms then use Jupiter`s gravity to swing around to Mars interception course (a lot depends on Martian sensor platform placement, if they have good coverage it might not work). Of course ship`s electronics, crew, life support will still generate heat during coasting phase, but that will be orders of magnitude less than thermal output of main engine. Also decoy that can fake small IR signature of a coasting warship is going to be much cheaper.

Still far from perfect, but it might cause confusion for Martian defenders, because they won`t know for sure how much of those weak IR signatures that just appeared from behind the Jupiter are real warships and how much are decoys. They would have to wait while approaching fleet comes close enough for optical observation to tell the difference.

[GrandMasterTerwynn]

These (unrelated) questions assume a hard science fiction setting.
[*]It's a given that there is no stealth in space. If you radiate, you are visible. Period. Does this extend to ECM? I'm not suggesting that you can render your craft undetectable, but would it be possible to sufficiently disrupt self-guided weapons so as to render them ineffective? If someone lobs missiles at you, can you "jam" them so that they fail to intercept you / fail to arm before impact / etc.? Or would the No Stealth in Space rule preclude "jamming" of missile weapons?[/list]

The missile has four things working against it:

A) Smaller surface area to mount sensors on, which means smaller-aperture, lower resolution sensors.
B) You can compensate for this within reason by using telemetry links to the missile from the firing vessel, or from other vessels serving as fire-control relays.
C) Smaller internal volume and limited power reserves means that the missile's internal smarts aren't going to be as smart as the computers directing your opponent's EW suite. Also, the missile won't have the power reserves needed to power a beefy radar or LIDAR set.
D) The missile has limited delta-V. You only need your ECM to work well enough to get the missile far enough out of position that it can't generate an intercept anymore.

From this, one can devise several possible electronic defenses against an incoming missile.

1) Attempt to spoof the control links. Sure, you won't be able to issue false commands to the warhead, as it will almost certainly be using some manner of highly-encrypted link. You might, however, attempt to swamp the control link signal with a lot of noise. Depending on the design of the missile firmware, the missile may elect to disregard further remote input if it can't get a reliable uplink. This forces it to rely on internal guidance, making it easier to decoy. Since the missile's downlink signal will probably be fairly weak, you can direct your ECM at the launching ship as well.

2) Attempt to spoof the missile's guidance system. You can absorb or scatter radar or LIDAR beams coming your way, or you can attempt to generate false returns, or swamp the missile's radar set with noise. The attacking vessel may get around this by putting the missile guidance radar on-ship, rather than in the missile. Against radar, decoys have their uses. They would also be useful against missiles with a passive beam-riding RF seeker, which is trying to home in on your own radar and ECM emissions. They would be much less useful against IR sensors, as an inhabited ship is going to have a spot on it somewhere that's nearly 300K warmer than the background. If you're actively thrusting, then your drive emissions will be much hotter than that. They'll also be less-useful against optical sensors which can, as has been mentioned, derive your approximate mass and velocity by looking at your drive emissions signature. The missile will also be able to derive the shape and features of your ship. Furthermore, a missile may not switch over to its IR/optical seeker until it's much closer to you, and you're filling enough of it's field-of-view for it to reliably resolve you. The attacking ship will also have a sophisticated set of large-aperture sensors on-board to do this for the missile. At which point, you're back to attempting to spoof the missile's control links.

3) Dazzle the missile's guidance system. The missile's firmware may attempt to protect its sensors by shuttering them, or protect its tracking solution by reducing exposure times and sensitivities to keep the sensors from being saturated. This is the same as shooting at them with your point-defense, only you're starting to fire on them while your beam spread is still too wide to affect a hard-kill. The missile may attempt to defeat this by spinning rapidly, but the resulting gyroscopic stabilization will make it hard to maneuver.

[Beowulf]

You can't detect the mass, but you can infer it from the drive temperature, mass flow, and doppler shift. You can't just have the decoy emit the signature, because all that information comes from the drive plume, which is going to be much, much larger than any practical decoy. It'll come from the wrong place, and can therefore be ignored.

That depends on how far away these targets are, and how huge the telescopes are. If you're using gigantic telescopes you can see in greater resolution, but you can't sweep those suckers around like a flashlight either, which limits your scan speed and creates its own problems. You're assuming perfect resolution; no ECM solution has to be perfect. It only has to overcome the inherent limitations of the sensor technology.

You may need a gigantic telescope for discrimination, but you can use much smaller and handier telescopes for tracking and search. You just need to use them to cue the giant telescope to the location of the possible targets. If you manuever, you can be distinguished from the decoys. Ditto if the decoys manuever. It gets worse if multiple telescopes can operate in sync, since then you can also get distance by some fairly simple trigonometry (if you have precise enough pointing).

1) Attempt to spoof the control links. Sure, you won't be able to issue false commands to the warhead, as it will almost certainly be using some manner of highly-encrypted link. You might, however, attempt to swamp the control link signal with a lot of noise. Depending on the design of the missile firmware, the missile may elect to disregard further remote input if it can't get a reliable uplink. This forces it to rely on internal guidance, making it easier to decoy. Since the missile's downlink signal will probably be fairly weak, you can direct your ECM at the launching ship as well.

With sophisticated enough antennas and receivers, you can distinguish between a signal coming from in front of you and one coming from behind you, and be able to reject the jamming coming from incorrect directions. Alternatively, you use laser comms, and keep the telescopes locked onto each other. Not going to eliminate the problem, but will reduce it to the point where it's not going to matter too much because by the time it matters, you'll likely already be at the point where the missile can distinguish the targets reliably itself. Note that this requires four telescopes (one pointing at where the missile was, another pointing at where the missile will be, and a third and fourth on the missile pointing at past and future locations of the ship).

3) Dazzle the missile's guidance system. The missile's firmware may attempt to protect its sensors by shuttering them, or protect its tracking solution by reducing exposure times and sensitivities to keep the sensors from being saturated. This is the same as shooting at them with your point-defense, only you're starting to fire on them while your beam spread is still too wide to affect a hard-kill. The missile may attempt to defeat this by spinning rapidly, but the resulting gyroscopic stabilization will make it hard to maneuver.

A viable way of increasing the difficult of an intercept. I'm not sure if the countermeasure is viable though (though the missile may already be spinning as a way to decrease the required number of manuevering engines).

[Darth Wong]

That depends on how far away these targets are, and how huge the telescopes are. If you're using gigantic telescopes you can see in greater resolution, but you can't sweep those suckers around like a flashlight either, which limits your scan speed and creates its own problems. You're assuming perfect resolution; no ECM solution has to be perfect. It only has to overcome the inherent limitations of the sensor technology.

You may need a gigantic telescope for discrimination, but you can use much smaller and handier telescopes for tracking and search. You just need to use them to cue the giant telescope to the location of the possible targets. If you manuever, you can be distinguished from the decoys. Ditto if the decoys manuever. It gets worse if multiple telescopes can operate in sync, since then you can also get distance by some fairly simple trigonometry (if you have precise enough pointing).

Well obviously, you break stealth if you start doing a lot of maneuvering burns. I didn't think anyone was seriously questioning that.

But why would that be necessary? Look, nobody is going to fight over empty space; they'll fight over territory of value, like planets and moons. If somebody is plotting an attack course to a target of value, they'll probably know exactly where it will be at any given time. They can plan out a course starting from very far away and coast in, and do all their burns at the beginning, when they're really far away and they're obstructed from view. If they're trying to use stealth, they're probably trying to attack large predictable targets. I don't think anyone is seriously expecting to be doing all kinds of full-burn maneuvering while maintaining stealth.

[Samuel]

That depends on how far away these targets are, and how huge the telescopes are. If you're using gigantic telescopes you can see in greater resolution, but you can't sweep those suckers around like a flashlight either, which limits your scan speed and creates its own problems. You're assuming perfect resolution; no ECM solution has to be perfect. It only has to overcome the inherent limitations of the sensor technology.

You may need a gigantic telescope for discrimination, but you can use much smaller and handier telescopes for tracking and search. You just need to use them to cue the giant telescope to the location of the possible targets. If you manuever, you can be distinguished from the decoys. Ditto if the decoys manuever. It gets worse if multiple telescopes can operate in sync, since then you can also get distance by some fairly simple trigonometry (if you have precise enough pointing).

Well obviously, you break stealth if you start doing a lot of maneuvering burns. I didn't think anyone was seriously questioning that.

But why would that be necessary? Look, nobody is going to fight over empty space; they'll fight over territory of value, like planets and moons. If somebody is plotting an attack course to a target of value, they'll probably know exactly where it will be at any given time. They can plan out a course starting from very far away and coast in, and do all their burns at the beginning, when they're really far away and they're obstructed from view. If they're trying to use stealth, they're probably trying to attack large predictable targets. I don't think anyone is seriously expecting to be doing all kinds of full-burn maneuvering while maintaining stealth.

The problem is that you will still be pretty visible due to the fact your temperature is so much higher than your surroundings.

Decoys might work for the coasting, except they would have to be powered so they looked like the actual ships and they would be useless when the shooting started- not to mention enemies could just fire some mass driver rounds to test the mass.

Finally, your enemies can watch you when you are accelerating- you are simply that visible.

[Junghalli]

The thing about trying to do your burn behind an obstructing object, like Jupiter, is that it's fairly easily defeated by a prepared enemy. You just have to seed your solar system with sensor platforms.

Also, it's worth pointing out that any burn is going to be visible a long way away. The space shuttle's main engines could be detected out to the orbit of Pluto. Even it's manuevering thrusters could be detected in the asteroid belt. That's with present tech, mind you. Reference.

[McC]

There are a lot of what-if edge cases coming into play, so let's refine the conditions.

• Assume that both parties have already confirmed initial detection of one another, so any attempt to conceal one's self from initial detection of the opposing vessel is irrelevant. Range is variable.
• Assume those designing the weapons and countermeasures are not idiots (i.e. if IR is "undefeatable," they'll use IR; if it makes sense to use a range of different sensors, they'll do that).
• Assume that Atomic Rocket is correct with regard to drones: they'll have to be as expensive/massive/hot as full ships, thereby rendering them an ineffective means of "carried" ECM.

My main question is one of electronic warfare. I'll refine that as well.

• Is it conceivable that a missile with an intelligent sensor suite and computer system could be "jammed" by transmissions from its target?
• Is it conceivable that opposing vessels could sufficiently "jam" one another so as to require "eyeballing" (which can still be computer assisted) attacks of either a directed energy or projectile nature?

[Beowulf]

You may need a gigantic telescope for discrimination, but you can use much smaller and handier telescopes for tracking and search. You just need to use them to cue the giant telescope to the location of the possible targets. If you manuever, you can be distinguished from the decoys. Ditto if the decoys manuever. It gets worse if multiple telescopes can operate in sync, since then you can also get distance by some fairly simple trigonometry (if you have precise enough pointing).

Well obviously, you break stealth if you start doing a lot of maneuvering burns. I didn't think anyone was seriously questioning that.

But why would that be necessary? Look, nobody is going to fight over empty space; they'll fight over territory of value, like planets and moons. If somebody is plotting an attack course to a target of value, they'll probably know exactly where it will be at any given time. They can plan out a course starting from very far away and coast in, and do all their burns at the beginning, when they're really far away and they're obstructed from view. If they're trying to use stealth, they're probably trying to attack large predictable targets. I don't think anyone is seriously expecting to be doing all kinds of full-burn maneuvering while maintaining stealth.

Of course no one is going to fight over empty space. However, there's a good probability of fighting in empty space. If all you do is coast, the enemy can just lob munitions at you, at which point you'll have to fire back, or take the hits. And once you fire back, you've just revealed which target is real, and which are fake.

[Junghalli]

Is it conceivable that a missile with an intelligent sensor suite and computer system could be "jammed" by transmissions from its target?

If you flooded enough energy into its sensors to burn them out. Shine a bright laser into their sensors.

[Admiral Valdemar]

You don't even need that much energy aimed at the sensors. Enough visible laser light to flood the sensor CCD is all you need. It works against human targets with laser pointers over the counter, you just need a slightly beefier model to get the range with a conical beam spread and any optical detectors are useless. Radar can be dealt with via other means, as I said, by ECM or meta-materials. It's IR that is the big problem, and you'll never mask that short of breaking physics somehow. So you kill IR sensors (as easy as any optical detector suite) or accept you're visible no matter what you do.

Coasting in anything but a target rich environment that overwhelms the enemy's defence points to give you time is suicide. You can't manoeuvre and if your CIWS activate you've wasted your time anyway, unless you get real close to make it count without being pounded to oblivion beforehand. Even silent running, your power systems are going to be producing a lot of heat, and the only way you're getting rid of that is by radiators on your vessel's skin. Anything above 0 Kelvin sticks out like a signal flare in the void.

[GrandMasterTerwynn]

Assume that Atomic Rocket is correct with regard to drones: they'll have to be as expensive/massive/hot as full ships, thereby rendering them an ineffective means of "carried" ECM.

ECM drones are still useful as full ships. If not as decoys, then as remote soft-kill 'dazzling' platforms.

My main question is one of electronic warfare. I'll refine that as well.
Is it conceivable that a missile with an intelligent sensor suite and computer system could be "jammed" by transmissions from its target?

Addressed already. If a missile's comms system lacks a means of distinguishing signal direction, then its control link can be jammed, forcing the missile to rely on strict internal guidance. If the missile uses certain kinds of signal homing, a sufficiently sophisticated EW suite could conceivably spam that part of an incoming missile's guidance package with false returns. Of course, once its guidance computer realizes what's going on, the missile will simply switch to optical/IR homing, change its radar timing/frequency, or whatever else the missile might be carrying in its guidance package.

Is it conceivable that opposing vessels could sufficiently "jam" one another so as to require "eyeballing" (which can still be computer assisted) attacks of either a directed energy or projectile nature?

No. If you're not so far away from your target that you're experiencing lightspeed lag, those eyeballs will either be fed information from dazzle-able sensors, be out in a position promising impending death, and will be feeding data into slow human brains, which must then engage in even slower manual data input just to get the data back into the computers.

[lPeregrine]

Possibly silly questions, but it seems like a couple assumptions are being made here:

1) That the other side has unlimited ammo to "test" your coasting decoys. I'd be quite happy if my opponent wasted half of his missiles checking to see if my decoys were ships or not. Who cares if they're exposed the moment point defense is/is not fired, as long as they've drawn the missiles far enough away from my real ship to prevent an intercept.

2) That the decoys need to move a great distance away from the ship they're covering. For example, consider a remote ECM platform deployed a short distance from the launching ship. A weapon doesn't need to miss by all that much to save the real ship, would sensors be able to pick out the real ship 100m away from its decoy?

[Admiral Valdemar]

Possibly silly questions, but it seems like a couple assumptions are being made here:

1) That the other side has unlimited ammo to "test" your coasting decoys. I'd be quite happy if my opponent wasted half of his missiles checking to see if my decoys were ships or not. Who cares if they're exposed the moment point defense is/is not fired, as long as they've drawn the missiles far enough away from my real ship to prevent an intercept.

Why waste missiles? Use of railguns firing solid slugs of DU would be more than enough. If you're hit by a chunk of pointy metal going several dozen klicks/second, then you're going to feel it. You could effortlessly fire of a single shot at as many targets of reasonable size as you wanted. They're not going to move out of the way, and those that do or shoot down your shell, will soon be privy to escalation protocol.

2) That the decoys need to move a great distance away from the ship they're covering. For example, consider a remote ECM platform deployed a short distance from the launching ship. A weapon doesn't need to miss by all that much to save the real ship, would sensors be able to pick out the real ship 100m away from its decoy?

That depends on sensor resolution and fidelity with respect to the ECM deployed. If going by simple visual targeting, then there's no way you can miss unless the drone or mother ship lase the enemy ship's sensors in return. Additionally, a tactical nuke with a good load of shrapnel jacketing will make good flak for such eventualities. If the drone is that close, then a hit that vapes the decoy will mission kill the mother ship at the very least.

[lPeregrine]

Why waste missiles? Use of railguns firing solid slugs of DU would be more than enough. If you're hit by a chunk of pointy metal going several dozen klicks/second, then you're going to feel it. You could effortlessly fire of a single shot at as many targets of reasonable size as you wanted. They're not going to move out of the way, and those that do or shoot down your shell, will soon be privy to escalation protocol.

Why assume that you have railguns with the accuracy to hit a target at such long distances with a solid slug? It might be very easy to do the theoretical calculations for the shot, but doing it with a real weapon is very different.

That depends on sensor resolution and fidelity with respect to the ECM deployed. If going by simple visual targeting, then there's no way you can miss unless the drone or mother ship lase the enemy ship's sensors in return. Additionally, a tactical nuke with a good load of shrapnel jacketing will make good flak for such eventualities. If the drone is that close, then a hit that vapes the decoy will mission kill the mother ship at the very least.

Well, 100m was just a random number. I guess it depends on the exact sensors involved, but how plausible would it be to put a decoy close enough to the launching ship to hide it in the launching ship's IR signature (to avoid the engine thrust problem) and prevent it from being ignored as an obvious decoy, but far enough away that anything homing in on the decoy will miss the launching ship? You'd probably need to replace your decoys as they are destroyed, but could you divert enough fire away from the launching ship to justify spending that mass on decoys instead of other defense systems?

[Admiral Valdemar]

Why assume that you have railguns with the accuracy to hit a target at such long distances with a solid slug? It might be very easy to do the theoretical calculations for the shot, but doing it with a real weapon is very different.

Then fire multiple cluster munitions within a set pattern. A large non-manoeuvring object in space is easy to predict for using Newtonian mechanics.

Well, 100m was just a random number. I guess it depends on the exact sensors involved, but how plausible would it be to put a decoy close enough to the launching ship to hide it in the launching ship's IR signature (to avoid the engine thrust problem) and prevent it from being ignored as an obvious decoy, but far enough away that anything homing in on the decoy will miss the launching ship? You'd probably need to replace your decoys as they are destroyed, but could you divert enough fire away from the launching ship to justify spending that mass on decoys instead of other defense systems?

What would this decoy be doing? Are you trying to mask the IR signature? Impossible. Are you using the decoy as a staging platform for ECM and dazzling lasers? It's not going to fare well in an engine wake at all. If it's at any real distance, like tens to hundreds of klicks, then the two targets are easily resolved on radar, and the bigger target wins a volley of missiles for its trouble. You can't hide a decoy in open space without practically placing it under the wing of the mother ship, and doing that defeats the point of such a decoy in the first place. Too far away, and it is obviously identified as a decoy and all focus turns to the larger body that has just wasted resources and time on a decoy that achieved nothing.

Why not just replace that decoy with a fast-attack drone that consists of a high-gee engine and enough fuel/propellant to allow it to get in quick and try to take out the enemy's detection capability via lasers or micro-missiles? It would achieve the same objective of giving you an easier ride, and less likely to be a waste. Though in this instance, why not just fire an equivalent mass of tac. nukes at the target and saturate it's point-defences? Either way, your stealth is either hopeless at best, and lethal at worst.

[Adrian Laguna]

ECM in the form of blinding sensors should be able to work. A bright enough spotlight being shined in your eyes will blind you completely. You might know there's a bright light in front of you, but you won't know where in front because you can't see shit. At that point retaliation is pure guess work, you could easily empty a gun's clip and hit nothing but air. The same should hold true for any ship's sensors, if you can cause them to white-out from ten thousand kilometres away, them knowing what general direction you're coming from isn't going to help them much. They can guess, but most likely the vast majority of their fire will miss by a wide margin.

[Beowulf]

You don't even need that much energy aimed at the sensors. Enough visible laser light to flood the sensor CCD is all you need. It works against human targets with laser pointers over the counter, you just need a slightly beefier model to get the range with a conical beam spread and any optical detectors are useless. Radar can be dealt with via other means, as I said, by ECM or meta-materials. It's IR that is the big problem, and you'll never mask that short of breaking physics somehow. So you kill IR sensors (as easy as any optical detector suite) or accept you're visible no matter what you do.

Laser light is polarized. Therefore it can be rejected (polarized mirror shunts it out of the vision path or whatever). This works until the mirror goes kablooie from absorbing the fraction of the energy that's absorbed. There's other methods to dim the incoming light as necessary (irises, liquid crystal blockers). You'd need to use weapons grade lasers to blind at very long range, plus be very good at predicting where the enemy would be.

Coasting in anything but a target rich environment that overwhelms the enemy's defence points to give you time is suicide. You can't manoeuvre and if your CIWS activate you've wasted your time anyway, unless you get real close to make it count without being pounded to oblivion beforehand. Even silent running, your power systems are going to be producing a lot of heat, and the only way you're getting rid of that is by radiators on your vessel's skin. Anything above 0 Kelvin sticks out like a signal flare in the void.

Actually, it's 3 Kelvin (Microwave background). Close enough, anyway. Coasting is a dead man's trick.

Why waste missiles? Use of railguns firing solid slugs of DU would be more than enough. If you're hit by a chunk of pointy metal going several dozen klicks/second, then you're going to feel it. You could effortlessly fire of a single shot at as many targets of reasonable size as you wanted. They're not going to move out of the way, and those that do or shoot down your shell, will soon be privy to escalation protocol.

Why assume that you have railguns with the accuracy to hit a target at such long distances with a solid slug? It might be very easy to do the theoretical calculations for the shot, but doing it with a real weapon is very different.

Stick a laser command guidance system on it. It's still cheap. That gets you close enough (there can only be so much angular dispersion, which you can equip more delta-V than necessary to correct onto the shot).

[Darth Wong]

You don't even need that much energy aimed at the sensors. Enough visible laser light to flood the sensor CCD is all you need. It works against human targets with laser pointers over the counter, you just need a slightly beefier model to get the range with a conical beam spread and any optical detectors are useless. Radar can be dealt with via other means, as I said, by ECM or meta-materials. It's IR that is the big problem, and you'll never mask that short of breaking physics somehow. So you kill IR sensors (as easy as any optical detector suite) or accept you're visible no matter what you do.

Coasting in anything but a target rich environment that overwhelms the enemy's defence points to give you time is suicide. You can't manoeuvre and if your CIWS activate you've wasted your time anyway, unless you get real close to make it count without being pounded to oblivion beforehand. Even silent running, your power systems are going to be producing a lot of heat, and the only way you're getting rid of that is by radiators on your vessel's skin. Anything above 0 Kelvin sticks out like a signal flare in the void.

Why would a vessel have to be producing a lot of heat while coasting? You're assuming it would be like a Star Trek vessel: a big ship with hundreds of humans on board running around. It seems to me that in a hard sci-fi universe, we'd be using an awful lot of robots, semi-autonomous remote-controlled vehicles, etc. And if you float a shield alongside your vessel, you could be keeping its facing surface cool too.

[Admiral Valdemar]

Why would a vessel have to be producing a lot of heat while coasting? You're assuming it would be like a Star Trek vessel: a big ship with hundreds of humans on board running around. It seems to me that in a hard sci-fi universe, we'd be using an awful lot of robots, semi-autonomous remote-controlled vehicles, etc. And if you float a shield alongside your vessel, you could be keeping its facing surface cool too.

I'm thinking patcom sized vessels, which have at most half a dozen officers and maybe a dozen crew, tops. Your thermal signature would depend on your readiness level, for instance, capacitors charged for weapons banks and sensor units. If you're totally down, running batteries for life support and relying on minimal passive sensors, then your signature is smaller, but you're counting totally on being able to use that stealth successfully. Any enemy action and you're a sitting duck. The shield idea would still be susceptible to enemy investigation if it strays too close to vital space, again, that depends on how dense any set sector of space is with debris and how small and easy to conceal your ship is and whether the enemy has detector drones dotted around the system.

[Ender]

Because if the drone is have the same signature as your ship, it's going to have to weigh the same as your ship. Otherwise the emission signature of the drone's drive is going to be different than you.

Since when can we magically detect the mass of a distant drone? All we can see is light coming from it, and it's not going to produce enough gravitational effect on its surroundings to derive it from the movement of planetary bodies. Are you saying that the mass has to be the same so that the light and heat radiated from it is the same? Why can't you simply actively emit more light in the direction of the sensor?

I'm reminded of the Simpsons. "I'm a Mathemagcian!". No magic involved, simple calculation. Doppler shift gives you exhaust velocity, luminosity gives you mass flow. Thrust is exhaust velocity times mass flow. Divide thrust by observed acceleration and you get mass.

Why would a vessel have to be producing a lot of heat while coasting? You're assuming it would be like a Star Trek vessel: a big ship with hundreds of humans on board running around. It seems to me that in a hard sci-fi universe, we'd be using an awful lot of robots, semi-autonomous remote-controlled vehicles, etc. And if you float a shield alongside your vessel, you could be keeping its facing surface cool too.

Even if you assume you were cold, with all onboard power supplies shut down for everything, you'd still show up and you came in system. The local solar constant it going to heat you up. You may only get upto, say 150 K, (temp of an asteroid IIRC) but against a background of 3 K you show up easily.

[Darth Wong]

I'm reminded of the Simpsons. "I'm a Mathemagcian!". No magic involved, simple calculation. Doppler shift gives you exhaust velocity, luminosity gives you mass flow. Thrust is exhaust velocity times mass flow. Divide thrust by observed acceleration and you get mass.

How does this disprove the notion that at great distances, you can fake these things by adjusting a drone's active emissions? The whole point of ECM is to produce fake emissions; why are we assuming that its emissions must be its natural rocket emissions? And yes, I know that if you assume arbitrary resolution for the sensor device you can make out the difference, but I'm still not seeing why people should be assuming that.

Even if you assume you were cold, with all onboard power supplies shut down for everything, you'd still show up and you came in system. The local solar constant it going to heat you up. You may only get upto, say 150 K, (temp of an asteroid IIRC) but against a background of 3 K you show up easily.

So you look like a rock; why doesn't that count as stealth?

We're talking about a hard sci-fi environment, aren't we? In such an environment, everything takes months. We're not talking about an object streaking in at 0.9c.

[Beowulf]

I'm reminded of the Simpsons. "I'm a Mathemagcian!". No magic involved, simple calculation. Doppler shift gives you exhaust velocity, luminosity gives you mass flow. Thrust is exhaust velocity times mass flow. Divide thrust by observed acceleration and you get mass.

How does this disprove the notion that at great distances, you can fake these things by adjusting a drone's active emissions? The whole point of ECM is to produce fake emissions; why are we assuming that its emissions must be its natural rocket emissions? And yes, I know that if you assume arbitrary resolution for the sensor device you can make out the difference, but I'm still not seeing why people should be assuming that.

Because it'd also have to reproduce the spectrum of the drives, including any nulls and so forth, at shifts appropriate for the relative exhaust velocity. The shifts change depending on accleration vector, and current relative velocity, so you can't just have it be fixed. And it glows over a very large distance. What's worse, each engine will have slightly different characteristics as far as specific impulse and so forth go, which results in a unique signature. So if the ship's been seen before, they can determine by spectrum which one is which. Or at least until the change out the engines anyway.

That's not counting the sheer power required to do so. Even today, your average rocket has a power in the gigawatt level. The Space Shuttle has an output of about 31 GW at liftoff. More advanced rockets, although they'd have better fuel efficiencies, most likely, won't have any better power efficiencies. In fact, they can't, if they want better fuel efficiency. And to output at a given signal level, you'll need many times greater heat output. If you're going to claim arbitrarily large values for the ECM equipment output, then it's not a stretch to assume arbitrary resolution for the sensor device.

Even if you assume you were cold, with all onboard power supplies shut down for everything, you'd still show up and you came in system. The local solar constant it going to heat you up. You may only get upto, say 150 K, (temp of an asteroid IIRC) but against a background of 3 K you show up easily.

So you look like a rock; why doesn't that count as stealth?

We're talking about a hard sci-fi environment, aren't we? In such an environment, everything takes months. We're not talking about an object streaking in at 0.9c.

You look like a rock coming in towards an object that needs to be defended. Of course they're going to take a hard look at it. Either you're a hostile trying to sneak in, or your a rock that can be mined/needs to be deflected/needs to be destroyed. In any case they're going to take a long hard look at it, and with months to spare, they can stick some pretty large optics to take a look.