Stealth in space

[SciMan]

Then you have to worry about getting rid of the heat from the coils themselves, as well as the power required to fire them in the first place, and the power used to cool the slugs.

I'm going for "use as little power as possible until it's too late for the enemy or target to do anything about it".

Basically, it looks like an asteroid, is the same temperature as an asteroid, ... and oh crap it just shot a missile at us that we're too close to dodge.

[tater]

Again, you need to define all available tech. Anti-missile fire is basically 100% effective, it's only a matter of at what range (the FC solution is trivial as you know exactly where it is going, and eventually its bearing will not change).

Unmanned warships are possible, but also the expendable as targets (your own ships would be similarly unmanned, and you'd not mind losing them anyway).

if you posit drifting probes that have missiles, you need to think about timescales. Were they dropped in the Oort Cloud, and did a retro burn 10,000 years ago to fall into the system, or did the war start a few weeks ago (assume some FTL, unless we are talking one solar system)? In that case ships need to appear somewhere in system, then engage targets. Depending upon your FTL flavor they won't know where the enemy is.

[luizopiloto]

there's no possibility of begin "invisible" in space... It can disperses radio waves to be invisible to radars as the the actual stealth planes. You can coat the craft with a mirrored surface, so it becomes "invisible" in the visual light spectrum... But... What bout IR light?

The only possible way of loosing heat in space is through irradiation, IR light, It is impossible to do it in another way... and to have energy you will generate heat... and the today IR sensors can be really sensitive... Imagine how they will be tomorrow?

I hope not, but, if we start to have battles in space... it will be like submarines hunting each other... hiding behind stuff or in front of the system star to not be detected... launching flares as decoys to lure enemy... and so...

Edited May 27, 2015 by luizopiloto

[Wesreidau]

Just remember that even in the days of bright primary colored uniforms and shooting at twenty paces, stealth was still obtained by placing oneself behind a hill. As a tactical matter, stealth and surprise are both possible. As an engineering matter, however, you're boned.

I anticipate warships will be "painted" in WWI-style dazzle camouflage to make them harder to identify as one class or the other, not harder to identify as a ship. Odd angles of aluminum sheeting and graphene fabric, exotic paints, who knows. There were a lot of ships in WWI that threw up a sheet metal funnel stack and presto, that antique armored cruiser is now identified as a modern battlecruiser. Better stay clear. Guessing and second-guessing intelligence reports will be a crucial element of strategy then as it is now, and if you wish to make a surprise maneuver just slide Jupiter between yourself and the observer before making your burn. With DEWs able to fire out to even several light-seconds showing up on an unexpected part of the horizon could mean your weapons strike first and their return fire is that much shorter-lived.

[Dausuul]

You cannot keep the ship from radiating IR, period. Failure to do so cooks the crew, period. How do you radiate inside, exactly? That's where the heat already is.

That's why I mentioned a heat sink, also known as "a big block of ice that keeps the ship cool." You are, of course, limited by the length of time it takes the ice to melt (or sublimate, or just warm up, depending on what kind of ice you've got). If your mission isn't done by then, you're screwed. However, while the ship is coasting, you only need to absorb as much waste heat as the life support systems and the crew members' own bodies generate. If the crew compartment is small relative to the size of the ship, this should be doable.

The only reason FOR stealth is presumably war, right? Your spacecraft cannot be moving fast, as that would take a visible burn.

Accelerating up to speed does pose a challenge, and may not be possible to accomplish stealthily. However, nobody says you have to stay with the engine that's gotten you up to speed. Ride on a booster rocket which accelerates hard and alters its course frequently. At some point, separate from the rocket and leave it to continue on its course-changing way. The enemy doesn't know when you separated or what your course was when it happened. If they're watching the rocket, all they're going to see is the glare of its drive going full blast. The nice thing about space is that once you're up to speed, you can coast to your destination.

As a result, the weapon is not a KE weapon. Any directed energy weapon requires massive power inputs… all of which power, must be radiated. All. Megajoules per cm^2 worth for directed energy weapons.

A directed energy weapon travels at the speed of light. The enemy's first observation of the weapon will be when it hits them (well, maybe a couple of seconds' warning if your weapons throw off energy while preparing to fire). At that point, your stealth mission has been successful. You can quit sneaking around, fire up your main engines, and blast out of there.

Again: You don't have to be stealthy forever. Just long enough to get where you need to be and do what you need to do.

This has been beaten to death by space warfare gaming geeks for ages on the next, very possibly since before you were born (we had long discussions about it on USENET in the 1980s, back when the ante to be on the net at all was to be in science or engineering at the university level). The answer has not changed.

I've read many of those discussions, and it looks to me as if the "stealth is impossible" side relies on some very unrealistic assumptions--most notably, that your ship must be able to remain stealthy indefinitely, and that you must be able to accelerate hard in stealth. Saying that stealth in space is difficult and limited (indisputably true) is very different from saying it's impossible.

[KerikBalm]

In theory, you could achieve limited stealth via directed radiation-> but this requires you to know where the enemy already is.

Consider the current state of human civilization... you can pretty much just present a super cold face to earth, and radiate away from the sun/away from the ecleptic, and you wouldn't be detected.

Then you'd have to make maneuvers when there is an occuluding body.... the sun would work very well...

Now, once you've got observation craft presenting cold sides to Earth... you've got a detection network that the Earthlings cannot detect.

If the Earthlings send up obeservation craft of their own, you'll detect them first, and know not to radiate in their direction.

Next you make a massive hard-Xray laser, with a 30 meter focusing "lens"/ phased array, get your pulse energy into the gigajoules, and the power output into the petawatts, and you've got a weapon that can vaporize targets multiple AU away.

Game over.

Stealth in space could be a thing if you know where the enemy is.

People say that sort of disproves the whole idea - how can you know where the enemy is, if there is stealth in space. If you don't know where the enemy is, you can't have stealth in space... but then you can know where the enemy is... Its not self contradictory...

Its a positive feedback loop, that leads to dominance for one side.

The side that has better knowledge of where the enemy is, can radiate away from there, making them less likely to be detected, allowing them to get progressively better and better observation, and become progressively better and better at avoiding detection.

One side can have stealth, but not both.

The first side to achieve full 360 degree sensor coverage denies stealth to the enemy.

They then know where not to radiate, and can be stealthy.

Game over for the side lacking full sensor coverage.

[Shpaget]

You can't achieve 360° stealth since a stealthy ship has to radiate waste heat in some direction, I guess it should be away from the enemy. So the non stealth party only has to send a bunch of probes in various directions, highly elliptical and/or polar or retrograde orbits. A stealthy ship still has to radiate waste heat and will eventually be detected by at least some of the probes.

[luizopiloto]

What is the temperature of space?

Well... By what they told me, it's close to 0 K°. You cannot cool down any part of the ship close to 0 K°. That's the problem, there's no way to irradiate heat from just one part of the ship...

Why do you think IR telescopes can see so far away?

[Bill Phil]

Well...

If you make your ship look and act like something else, as well as make other properties like something else, then the "enemy" would probably think it's something else.

Not so much stealth, but disguise.

Like if your ship looked like an asteroid, and had equipment to actively cool the insides to "asteroid level", and propulsion was kept at a minimum, then the enemy would think it's an asteroid. And when you get far enough away from their station, you open fire. Close enough to shoot, but far enough to not be assumed a threat to the station and then shot.

But this may not work...

[AngelLestat]

What is this? zombie topic apocalypse?

3 resurrected threads or more just in the science section

[GreeningGalaxy]

Some comments about disguise:

- Disguising yourself as an innocuous freighter is fine, as long as you don't mind being an innocuous freighter. Sure, a freighter with a gun is slightly better in combat than no ship at all, but you're going to blow your cover in a big hurry if you try to linger around sensitive tactical zones or get on a good trajectory to start shooting at anything.

- Disguising yourself as an asteroid is even worse, because while innocuous freighters are generally expected to follow innocuous flight paths, they're at least expected to move and radiate heat. Asteroids are expected to do neither, so you're going to raise some alarms when the enemy notices that you're radiating a tiny bit more than you should for an asteroid. Getting up and moving is a dead giveaway, no matter how slowly you do it.

Sure, you could count on your enemy not paying attention to every last asteroid out there, but that's not a very safe assumption assuming advanced sensing technology. This goes doubly so if you've already tried the asteroid ploy on this enemy before.

- I suppose disguising yourself as an enemy warship (or, hell, flying a captured enemy warship) could work just fine, assuming you know all their secret codes. This might just take the form of hacking into your enemy's robotic warships without them knowing until it's too late, which is less proper stealth and more electronic warfare. Still, we'll take our small victories.

And to reiterate regarding thermodynamics:

-There's still no way to conceal your waste heat. It doesn't matter how big your radiator is, it doesn't matter how your engine works, and it doesn't matter how big a heat sink you have - you're still going to glow, and if you don't glow enough, you're going to cook and glow. Trying to make a multi-megawatt or -gigawatt reactor invisible to a high-tech infrared telescope in the same solar system as you is like trying to hide a megaphone with the siren button taped down on the top floor of a university library - no matter how many layers of blankets and insulation you wrap around it, it's going to get heard or seen, and almost certainly both. And the megaphone won't melt if it's prevented from emitting its sound for all to hear.

-This also goes for directional radiators. Directional radiators are terribly inefficient compared to regular ones, but inefficient radiators aren't illegal - the real problem is that the backside of your reflector will always be warmer than the cosmic background, which is what the enemy will be seeing you against. You can try to buy time by assuming that the enemy's telescopes aren't good enough to see you through 2000 layers of near-perfectly-reflective unobtainium-mylar, but you still have the problem that adding another 9 to the end of your reflection efficiency only means that your enemy has to increase their telescope sensitivity by just a little bit to keep seeing you. Don't let this stop you from having desperate people try something like this in your sci-fi, but don't treat it like it's always going to work or is remotely practical.

-Running dark is not useful if you're planning on changing your trajectory at any point, and it's right out if you have people in your ship. There may be situations in which supercooled sensor buoys or kinetic projectiles could go unnoticed for long enough to be useful, but those are going to be infrequent.

TL;DR - stealth in space, where 'stealth' refers to "being able to reliably hide oneself from an enemy at an unknown location", is still impossible. This doesn't mean that surprising your enemy is impossible, or that there aren't things you can do to make yourself less likely to get spotted - just that you shouldn't count on not being seen, because someone who's looking for you has everything in their favor for finding you.

[KerikBalm]

"Directional radiators are terribly inefficient compared to regular ones, but inefficient radiators aren't illegal - the real problem is that the backside of your reflector will always be warmer than the cosmic background, which is what the enemy will be seeing you against."

Directional radiation would be inefficient, yes... but given Earth's current observation capabilities.... you can basically radiate in 350 out of 360 degrees... trying to radiate in a narrow band would be very inefficient... but for our current observation capabilities, one wouldn't need to sacrifice all that much in terms of radiator efficiency.

As far as " the real problem is that the backside of your reflector will always be warmer than the cosmic background, "

There is nothing prohibiting you from running a heat pump, and cooling down 1 part of your ship to levels of the cosmic background.

This of course increases your total heat output, putting even more load on your already restricted radiators.

Combine this with the rocket equation, and you'll need so much mass reserved for radiators and cooling systems, that you'll have a terrible mass fraction, which means you'll need a very high Isp to do anything.

High Isps mean a lot of heat generation (due ot high power outputs)... which means you can't maneuver very much at all, and your exhuast will be very hot (so you can only thrust very far away, with the sun inbetween you and your target, etc).

It all sounds extremely impractical but it is not, stricktly speaking, absolutely impossible,

[GreeningGalaxy]

"Directional radiators are terribly inefficient compared to regular ones, but inefficient radiators aren't illegal - the real problem is that the backside of your reflector will always be warmer than the cosmic background, which is what the enemy will be seeing you against."

Directional radiation would be inefficient, yes... but given Earth's current observation capabilities.... you can basically radiate in 350 out of 360 degrees... trying to radiate in a narrow band would be very inefficient... but for our current observation capabilities, one wouldn't need to sacrifice all that much in terms of radiator efficiency.

As far as " the real problem is that the backside of your reflector will always be warmer than the cosmic background, "

There is nothing prohibiting you from running a heat pump, and cooling down 1 part of your ship to levels of the cosmic background.

This of course increases your total heat output, putting even more load on your already restricted radiators.

Combine this with the rocket equation, and you'll need so much mass reserved for radiators and cooling systems, that you'll have a terrible mass fraction, which means you'll need a very high Isp to do anything.

High Isps mean a lot of heat generation (due ot high power outputs)... which means you can't maneuver very much at all, and your exhuast will be very hot (so you can only thrust very far away, with the sun inbetween you and your target, etc).

It all sounds extremely impractical but it is not, stricktly speaking, absolutely impossible,

You're right that high Isp means very high engine power. However, it's not true that only burning far from the enemy, near the sun, etc. will help you. If you're running a big fusion torch, you're going to be visible from the next star system over, and you'll be putting out a lot of very distinctive wavelengths of light that will be identifiable even if you're right in front of the sun. Also, if you are right in front of the sun, be aware that you're going to show up as a great big black dot. Even if you manage to shield all your running heat in one direction (dubiously possible, but also admittedly not theoretically illegal), there's no way you'll do that with your exhaust too - for one, the hot part of your exhaust will extend many kilometers behind your ship, and it's also going to be emitting some gamma rays and stuff that you can't contain.

So if you're trying to do a high-speed flyby of a primitive civilization's planet, and you aren't planning on stopping or using your engine at all once you get close, you might get away with just putting a little shield between you and them. However, you might wonder what you'd hope to gain from doing that in the first place, and it would be very easy for a civilization with spacecraft to spot you just by being where you don't expect them to be, or by being in too many places for you to safely radiate your heat.

So I stand by what I said - reducing your observability and making it less likely for your enemy to spot you is possible, but the success of these tactics is more likely to reflect badly on your enemy than well on you - they're not the kind of thing that should be expected to work with any degree of reliability on a vigilant and well-established enemy, and it certainly won't be possible to hide once the enemy knows what you look like and has an idea of where you are (both of which will be revealed as soon as you fire your engine).

[cicatrix]

Stealth in space... it's a 'hide & seek' game as well as in anything claiming to be 'stealth'. Actually, if you hide behind some other object (a planet, for example) you will be nearly impossible to detect from the opposite direction. Speaking of just any 'stealth' technology - it can only be 'stealthy' for a very limited range of detectors. If you change the detection principle a previously stealthy object will be revealed. There's another way to hide in space though (meaning prevent an enemy to detect your IR emissions) - just scatter around just enough 'decoys' with strong IR emission. You will be perfectly 'hidden' among them.

[GreeningGalaxy]

There's another way to hide in space though (meaning prevent an enemy to detect your IR emissions) - just scatter around just enough 'decoys' with strong IR emission. You will be perfectly 'hidden' among them.

Decoys don't really work, because they're too easy to tell apart from real ships. By looking at your exhaust during burns, the enemy can tell your exact thrust power, exhaust velocity, thrust, and therefore mass. Not only does this allow them to track you with precision even if you're invisible between burns, but it also can tip them off to whether a given radiation source is a real warship or a silvered balloon.

You won't be able to make reliable fake fusion torches, either, because the real ones emit very distinctive spectral lines which will be impossible to simulate without using real fusion. There are too many details like that that will allow your enemy to pick you out of a crowd of decoys. If your decoys are convincing enough to pass off as capable warships, it means that they essentially are warships, and you might as well mount weapons on them and use them as such.

[cicatrix]

Decoys don't really work, because they're too easy to tell apart from real ships. By looking at your exhaust during burns, the enemy can tell your exact thrust power, exhaust velocity, thrust, and therefore mass. Not only does this allow them to track you with precision even if you're invisible between burns, but it also can tip them off to whether a given radiation source is a real warship or a silvered balloon.

You won't be able to make reliable fake fusion torches, either, because the real ones emit very distinctive spectral lines which will be impossible to simulate without using real fusion. There are too many details like that that will allow your enemy to pick you out of a crowd of decoys. If your decoys are convincing enough to pass off as capable warships, it means that they essentially are warships, and you might as well mount weapons on them and use them as such.

The fact that the detector is this sensitive means it can also be blindened with radiation intense enough. By 'decoys' I mean something tgat will lit the entire 'horizon' (if this figure of speech can be applied to space). You cannot distinguish white on white.

[Shpaget]

Actually, if you hide behind some other object (a planet, for example) you will be nearly impossible to detect from the opposite direction.

Yes, planets are a very good camouflage, however, how do you get behind a planet without being spotted in the first place?

Depending on a planet you hide behind, you'll need to pick your orbit carefully.

[doing math now]

If I'm not wrong, for Mercury and Venus, such an orbit would require a period of 365 days. For Venus that would be about 2 000 000 km orbit.

For outer planets, L2 would suffice.

That is terribly far away and would likely be spotted by some probe on a completely unrelated mission.

If you somehow manage to do it and are safely hidden behind a planet, what are you going to do there?

Being behind a planet hides you well from whatever is on the other side, but also puts you in a very useless place to observe (or attack) the thing that you are hiding from.

The fact that the detector is this sensitive means it can also be blindened with radiation intense enough. By 'decoys' I mean something tgat will lit the entire 'horizon' (if this figure of speech can be applied to space). You cannot distinguish white on white.

Sure you can. You can never hope to achieve the same power output over a significant portion of the sky as your engines are producing. If you had that kind of power source at your disposal, you would not try to hide. You would incinerate entire planets, not play hide and seek.

Also, ND filters.

[KerikBalm]

However, it's not true that only burning far from the enemy, near the sun, etc. will help you. If you're running a big fusion torch, you're going to be visible from the next star system over, and you'll be putting out a lot of very distinctive wavelengths of light that will be identifiable even if you're right in front of the sun.

I wasn't talking about in front of the sun, I was talking about *behind* the sun.... Like 2 AU away. Ie.... Earth____1AU____Sun_____1AU_____"Stealthy" ship

Note that 2 AU is within striking range of a hard X ray laser with a 30 meter focusing array and multiple gigajoule laser pulses... but moving such a behemoth... without its exhuast plume showing up.... maybe if you did your burn from alpha centauri, and then presented a cold face to earth as you approached, and opened up at 2 AU.... but it seems more practical to just get closer, or use a KEW.

Also, if you are right in front of the sun, be aware that you're going to show up as a great big black dot.

Unless you are radiating a lot of energy away from the sun.. I'm imagining something almost like the bi-tonal camoflauge of many aquatic animals.

Present a cold side to the inner solar system, and emit alot of radiation in a narrow cone meant to mimic the sun... but yea... from most directions, that wouldn't work, and you'd need to know which directions you can't radiate to.

Even if you manage to shield all your running heat in one direction (dubiously possible, but also admittedly not theoretically illegal), there's no way you'll do that with your exhaust too - for one, the hot part of your exhaust will extend many kilometers behind your ship, and it's also going to be emitting some gamma rays and stuff that you can't contain.

Indeed, which is why you'd need an occluding body... I think many kilometers is an understatment... again... I think you'll need the sun in between you and the target when you light up your torch to change your trajectory... from there you power down and do your best to present a cold side to the enemy planet as you get close during your flyby... it would definitely be maneuvers on the "strategic" scale, not the "tactical" scale.

So if you're trying to do a high-speed flyby of a primitive civilization's planet, and you aren't planning on stopping or using your engine at all once you get close, you might get away with just putting a little shield between you and them.

It would be enough to wipe out Earth level civilization with a barrage that we wouldn't see coming (but given our capabilities... why bother hiding...)

However, you might wonder what you'd hope to gain from doing that in the first place, and it would be very easy for a civilization with spacecraft to spot you just by being where you don't expect them to be, or by being in too many places for you to safely radiate your heat.

Indeed, too many spacecraft renders this unworkable, on side has to start with dominance... a cold war type scenario would render it moot.

But as to a spacecraft where you don't expect it to be... I think one could easily identify and avoid all of earth's spacecraft capable of observing them. Its not like our spacecraft are designed to hide.

At the most basic level, you could just radiate in all directions except along the ecliptic plane, and you'd be safe from detection by Earthlings.

Again, two forces, coexisting in significant size before hostilities, will make "stealth" completely unworkable.

So I stand by what I said - reducing your observability and making it less likely for your enemy to spot you is possible, but the success of these tactics is more likely to reflect badly on your enemy than well on you - they're not the kind of thing that should be expected to work with any degree of reliability on a vigilant and well-established enemy,

Agreed, it only works when one side has a vast advantage over the other.

I agree completely that it is extremely impractical and not likely to work in a crowded system - but it is not, strictly speaking, impossible in all cases.

I can imagine some sci fi story where two rival "cruisers" arrive in a star system at nearly the same time... lets say one arrives first and starts some operations of some sort (ISRU refueling?) on a planetoid.

The 2nd one arrives, and anticipates that its quarry is trying to do some ISRU.

Both sides have a limited number of probes to launch to get alterntative observation points.

The "hunting" cruiser can assume its quarry is in the ecliptic plane, and radiate anywhere but there.

A quick survey of the system leads to obvious ISRU candidates, an insertion burn is planned with the sun between it and the best candidate.

This hunter equiped with the directional radiation equipment nears its target, and detects it.

The target, either radiating in all directions, or in a direction that it didn't anticipate the enemy ship coming from (perhaps it, too, was not radiating along the eclptic, so the "hunting" ship purposefully came in along a different plane), is detected but fails to detect the pursing ship.

The pursing ship readies its hard-xray laser array.

Its heat signature from the immense power output arrives simultaneously with the laser pulse... the target is destroyed due to a section of its hull exploding as the laser vaporizes a portion of it.

Is that stealth? Is that scenario plausible?

Yes and yes I think

Is it unrestricted fly around like a cloaked ship in star trek, or a F117 over baghdad?

No and No

Edited May 28, 2015 by KerikBalm

[Shpaget]

The first ship doesn't launch the probes? One probe just 30° ahead or behind on a similar orbit around the star will get rid of almost all usable blind spots behind that star.

[Wesreidau]

Ship A and ship B are on opposite sides of Titan. Both are on the same orbital plane with the same inclination and speed and altitude; synchronized in a perpetual tail chase. Ship A decides to engage, burning to change its orbit to intersect Ship B. Ship B cannot see Ship A's burn, and so does not know Ship A will come over the horizon. In this, Ship A has surprise.

Not stealth. Surprise. But since the purpose of stealth is surprise, it is functionally the same.

If Ship B has a probe around Jupiter able to see Ship A's burn, then it can transmit that information to Ship B. However, light is not instantaneous. It is possible, given distances between proxy observers, to strike before being observed translates into intelligence. Getting accurate information to those who need it has always been a military challenge.

And that speaks nothing of shooting the probes. Unless probes carry their own antimissile systems, I can see a real use for the missile even if CIWS systems become 100% effective.

[tater]

Directional radiators presume knowledge of where enemy detectors are. Accept stealth for the sake of argument (bad given, but wth). Enemy sensor platforms and picket ships are now also stealthy. I am presuming FTL, as any 1- system scenario has us seeing every single ship take off anyway. So a wild enemy ship appears. Where does it point the magical radiator (since it is being watched by "invisible" sensor platforms it cannot know the location of)? How does it maneuver without being seen?

Decoys… Decoys are not a thing. Any decoy that would work would be another whole ship, it can't just look like a ship in IR (aside from the fact that it might well be resolved anyway with a space based telescope), it needs to act like one, and that means observed drive plumes matching the altered orbit. That means the right mass.

Being in front of the sun would certainly mitigate detection, but from the earth, for example, that's 0.5 degrees to hide in, as you must by definition be directly between the sensor and the star. Even then you are then transiting, and now a dark contrast.

If if you want stealth, you should stop trying to pretend to have "hard" SF, and posit "subspace radiators" or something.

- - - Updated - - -

Ship A and ship B are on opposite sides of Titan. Both are on the same orbital plane with the same inclination and speed and altitude; synchronized in a perpetual tail chase. Ship A decides to engage, burning to change its orbit to intersect Ship B. Ship B cannot see Ship A's burn, and so does not know Ship A will come over the horizon. In this, Ship A has surprise.

How does A know B is there? LOS is reciprocal. A cannot get to the far side easily without knowing at all times where B is, even when it is unseen.

It would s not impossible to imagine rare cases where a ship might find itself surprised, but both would likely be surprised, and this would be very, very rare.

Edited May 28, 2015 by tater

[KerikBalm]

The first ship doesn't launch the probes? One probe just 30° ahead or behind on a similar orbit around the star will get rid of almost all usable blind spots behind that star.

Scenario 1: The captain was not too bright, and didn't think it was worth using his limited probt supply when no enemy had been detected.

Scenario 2: Probes were launched, and they were spotted by the hunter first (since they come from the ship intending to do ISRU operating, and therefore launched from the ecliptic, where the hunter is not radiating). The hunter fires its hard X ray laser, but has a sufficient heat sink/ insulation, to maintain its cold "shield" (as you called it), and is not detected by the others. The destroyed probe is vaporized the same instant it would have been able to detect anything... no information gets sent

Scenario 3: the victim ship fled from a nearby star system where the battle went south for its side... it has no probes yet...

Of course, this assumes ship travelling at a significant portion of C, or one of the longest pursuits imaginable. Assuming a significant portion of C, there's no way the first ship wouldn't detect the pursuer... unless the pursuer slowed down far outside the system... but by that point the fleeing ship should have plenty of time to do ISRU, and then leave the ecliptic.

It seems directional radiation could situationally work to hide your current position... but the situation needs to get pretty contrived to allow you to do any maneuvers.

Tater - please see post #68, which addresses those issues (and admits that in many cases, directional radiation wouldn't work, but there are cases where it could... situational stealth if you wish).

I also suggest a review of post 62 and 56 -stealth can't be working for both sides at once, unless both sides capabilities are limited, or known before hand.

For example, to hide from the governments of Earth, you know radiating anywhere away from the ecliptic plane is safe.

[cicatrix]

Sure you can. You can never hope to achieve the same power output over a significant portion of the sky as your engines are producing. If you had that kind of power source at your disposal, you would not try to hide. You would incinerate entire planets, not play hide and seek.

Also, ND filters.

To detect something at this distance your field of view should be very narrow. I'm not saying that this is 100% reliable, but imagine I launch 2 thermonuclear warheads like this:

These two blasts will give me at least some time.

[tater]

I read that post. Drifting in from another system seems pretty absurd, the great, great grandchildren of the "attacker" would be interested to discover the result, except they won't know, either, unless they send a craft for BDA, and maybe their GGGG grandchildren can find out.

If that's the case throw a rock.

If ships have FTL, they need not contain themselves to the ecliptic, they can FTL out of plane, then use normal space if stealth were considered a thing (if you consider it real, then all reasonable countermeasures will also become a thing, so there will be sensors scattered all around, etc).

A hard x-ray laser? What is pumping it, a bomb? If it is a reactor… all that energy has to be radiated.

You really have to jump through hoops to try and justify any sort of stealth in space, even in special cases. For what people think of generally as SF combat (we will assume FTL drive as the sole conscious attempt to violate physics), we have to have warships appearing in system, then finding the enemy (who is now also magically stealthy), maneuvering without being seen (impossible), etc.

One of the guys we hashed this out with around 20 years ago is an IR astronomer (at the time he was at Mauna Kea). Even a comfortable crew compartment is a relatively bright IR source for an early 1990s IR telescope. He did the math on reasonable (current at the time) telescope systems, and whole sky surveys capable of detecting "player" sized starships were easy to do, as they could be very wide field. If the ship was actually powered up, it was "naked eye" visible in magnitude (except in IR) at a vast range.

We did this because we actually wanted stealth to work, but it just doesn't. With a lot of hand-wavium, we managed to get some sensor rules for a space combat game that allowed some mitigation of otherwise automatic detection at great range. At any sort of tactical range… all ships are easily visible.

Again, I'd stress that for a nitty-gritty discussion, you really need to nail down the specifics of the SF universe people are dealing with so we are all on the same page. If it is Earth vs Mars using nothing we don;t have now, that is different than having a space warship using FTL drive to go to a nearby system to attack.

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To detect something at this distance your field of view should be very narrow. I'm not saying that this is 100% reliable, but imagine I launch 2 thermonuclear warheads like this:

These two blasts will give me at least some time.

Yeah, but the time frame involved is pretty short, so the target will only alter their heading by a little assuming they are moving at a decent clip. Assuming you know the best they can do burn wise, their future position is still little changed, in other words.

[Shpaget]

If Ship B has a probe around Jupiter able to see Ship A's burn, then it can transmit that information to Ship B. However, light is not instantaneous. It is possible, given distances between proxy observers, to strike before being observed translates into intelligence. Getting accurate information to those who need it has always been a military challenge.

And that speaks nothing of shooting the probes. Unless probes carry their own antimissile systems, I can see a real use for the missile even if CIWS systems become 100% effective.

Light is not instantaneous, but it's a lot faster than spaceships.

In such a scenario a probe would be a few light seconds away at the most. Knowing the signal delay, you can easily compute the position of the enemy with a known and small margin of error. There would be no surprise.

Burning to change orbit is slow, ships take time to move around.

Also all this does not deal with the problem of how does the second ship come to the other side of the planet without being detected/shot at.