Stealth in Space

[Markdoc]

Re: Stealth in Space

 

As to stealth in space' date=' maybe one could minimize ones emissions to a very high degree, but a thought occurs: if true stealth isn't feasible, how about the opposite? Scattering thousands, or millions(!) of fake emitters around a system to randomly create false signatures and overwhelm the defenders ability to react to every possible sighting?[/quote']

 

For the same reason people don't try to overwhelm radar systems with swarms of plane-like drones in the real world: if it isn't the same mass and speed as a warcraft, a computer will screen it out in a microsecond. If it does have the same mass and performance as a real warcraft, why not just put weapons on it and increase your fleet's firepower a thousand-fold instead?

 

It's the same reason that modern ECM operates in limited spheres and on short time frames - it's not done to try and hide, but simply to confuse enemy targetting for a short period until you can kill his sensor capabilities. It's been suggested for example that you could "hide" your heat signature in space by mass nuclear detonations. That's not exactly stealthy: people in nearby star systems are going to notice that you are setting off thousands of nukes but stealth isn't the goal - it would simply be to confuse their targeting for a few seconds while you launch your attack and take evasive action: like a modern aircraft releasing chaff and flares against incoming missiles. Hopefully if you distract them briefly, you can outrun what's coming back in return.

 

cheers, Mark

[Xavier Onassiss]

Re: Stealth in Space

 

As to stealth in space' date=' maybe one could minimize ones emissions to a very high degree, but a thought occurs: if true stealth isn't feasible, how about the opposite? Scattering thousands, or millions(!) of fake emitters around a system to randomly create false signatures and overwhelm the defenders ability to react to every possible sighting?[/quote']

 

This isn't impossible, just very expensive. If the enemy's passive sensors are any good at all, you'll need the decoys to have exactly the same emissions profile as the spacecraft they're supposed to imitate. Sure, you can create a false radar contact with a small decoy that looks convincing, but its engine output for a given acceleration will be much lower than a full-size spacecraft, which gives away the game. So in the end, the decoy needs to have similar size and power output to the craft it's imitating to be convincing.

 

Decoys in space turn out to be almost as difficult as stealth. However, they might work in specific applications -- like countermeasures v. guided missiles which rely on a single type of sensor. (Although it would take a wicked-big IR flare to distract a missile away from a torch-drive....)

[Tasha]

Re: Stealth in Space

 

"The warriors".

 

The ship from earth used a laser as a drive system, the kzin telepath didn't realize it was a weapon because the humans onboard didn't consider it one.

 

Humans had been conditioned for decades against violence, with education, drugs and brainwashing being used to pacify the masses. It was illegal to learn history without a special permit.

 

The ARM (Amalgamation of Regional Militia) maintained the goody goody peaceful society thrua police state that regulated technology, used memory erasures on various potential troublemakers and forcibly maintained population control laws.

 

All in all, the contact with the kzin probably saved humanity from pacifying itself into stagnation.

 

Actually we are both right.

 

Excerpt The Warriors by Larry Niven

The Captain hurried, knowing that the Telepath couldn't stand this for long.

"How do they power their ship?"

"It's a light-pressure drive powered by incomplete hydrogen fusion. They use an electromagnetic ramscoop to get their own hydrogen from space."

 

Early in the story the drive is called a Photon Drive, using it for communications purposes was also mentioned. Later the Kzinti Telepath lets us all know that the drive is a primitive Ramjet that is powered by incomplete fusion (whatever that means). Later ships in the setting are said to use the Bussard ramjet which does use fusion to move around. http://en.wikipedia.org/wiki/Bussard_ramjet

[Sundog]

Re: Stealth in Space

 

Yeah that was the earliest Man Kzinti war story. The Kzin ship opened fire on an Earth Torchship (Buzzard Ramjet' date=' fusion torchship that used the hydrogen that was theorized to exist in space). Under fire mankind turned it's fusion drive toward the Kzinti ship destroying the Kzin ship and allowing mankind time to report home about the aggressive alien species. Also, Earth's technology was being retarded by a secret organization who's whole job was to keep technological progress slow enough that mankind wouldn't destroy itself during it's many wars against itself.[/quote']

 

Actually, it wasn't a torchship. Angel's Pencil used a fusion powered photon drive, which, for efficiency, was a laser. It sliced the Kzin ship in half.

They did something similar in The Mote in God's Eye, wher a solar sail ship, challenged by a human warship while sundiving (to slow down), used it's solar sail to focus the reflected starlight onto it's challenger. Unfortunately for it, the captain of the warship simply dived his vessel through the sail to avoid the focus.

[austenandrews]

Re: Stealth in Space

 

This isn't impossible' date=' just very expensive. If the enemy's passive sensors are any good at all, you'll need the decoys to have exactly the same emissions profile as the spacecraft they're supposed to imitate. Sure, you can create a false radar contact with a small decoy that looks convincing, but its engine output for a given acceleration will be much lower than a full-size spacecraft, which gives away the game. So in the end, the decoy needs to have similar size and power output to the craft it's imitating to be convincing.[/quote']

Not if you can target the sensors you want to fool. Even if there are a million sensors, shooting decoy beams at each one will take only a fraction of the energy of mimicking the energy signature in all directions. You could bounce power beams between them, so they wouldn't even need to generate it all themselves.

[Roy_The_Ruthles]

Re: Stealth in Space

 

Not if you can target the sensors you want to fool. Even if there are a million sensors' date=' shooting decoy beams at each one will take only a fraction of the energy of mimicking the energy signature in all directions. You could bounce power beams between them, so they wouldn't even need to generate it all themselves.[/quote']

 

What do you mean by decoy beams? I'm imagining it like shining a flashlight in someone's eyes to blind them.

[Cancer]

Re: Stealth in Space

 

Not if you can target the sensors you want to fool. Even if there are a million sensors' date=' shooting decoy beams at each one will take only a fraction of the energy of mimicking the energy signature in all directions. [/quote']

 

Assuming, of course, you already know (1) where a large enough number of those sensors are ahead of time, and (2) the spectral sensitivity and other response characteristics of those sensors. I think that's sort of like assuming you've already belled the cat.

 

My guess is that cloaking is unfeasible simply because sensor arrays -- especially passive sensor arrays, robotically operated -- are so cheap and easy to put on station. A star system with a permanent base, let alone an inhabited planet, ought to have thousands to millions of sensor arrays whose sensitivity spans the electromagnetic spectrum from pair-production gamma rays to VHF radio (lower frequencies than that don't propagate through low-density plasma) scattered throughout the system. And I mean "scattered": in our Solar System, those ought to be in orbits or on solid bodies from Mercury out to the Kuiper Belt, with ecliptic latitudes ranging to +/- 90°. How far out that array extends depends on your assumptions about drive systems, both insystem and interstellar.

 

Add other kinds of detectors (for gravity anomalies, static magnetic field anomalies, neutrinos, charged particles, N rays, whatever) as included in your game's tech level/rubber science. Even if your neutrino detectors require a cubic kilometer of scintillation mass -- and that is sort of what current neutrino detectors are -- well, there's a lot of kilometer-size asteroids and dead comets out there, and if you're not stationed in that system already, you're going to have all those charted out and investigated well enough to know the "real" ones from the artificial ones? Again, I think you're assuming you've already belled the cat.

 

This IS the kind of observational astronomy question that we've had to deal with for decades. The history of discovering the gamma-ray bursters and then figuring out what they are is the case study for putting together a sensor package that responds within seconds to sudden, without-warning gamma-ray bursts scattered very literally at random evenly around the sky. (I'm referring to the SWIFT gamma-ray burst mission and its ground-based support telescopes.) Yes, it's geared toward finding precursors in one bandpass (gamma rays) and slewing multiple more powerful detector systems of another bandpass (optical) toward the precursor target. But it works and it has worked for more than five years now, and that's one lousy satellite around a pre-interplanetary tech planet guiding about a half-dozen telescopes (again, all on that lousy little planet).

 

Unless you're in deep space (and this has to mean interstellar space, which means you are effectively alone against an enemy ship or squadron), or fighting an opponent at such close range that the signal lag time from most of the sensors you're trying to cloak against means those data can't enter your tactical situation -- which again to my mind is assuming you've already belled the cat in the sense that you have achieved the tactical surprise goal that stealth tech is supposed to be gaining you -- the arguments against "stealth in space" just are too overpowering.

[austenandrews]

Re: Stealth in Space

 

What do you mean by decoy beams? I'm imagining it like shining a flashlight in someone's eyes to blind them.

In short, if you shine a beam of light at me in the right way, it'll look like you're shining a much more powerful light in all directions.

 

A sensor recognizes a spaceship by actively or passively detecting various flavors of radiation emitted, reflected, refracted or obfuscated by said ship. The sum of these signals comprise a "beam" with a certain signature that strikes the sensor. A real ship will show such a signature from any direction. That's why it would take a lot of energy for a decoy to mimic a real ship's powerful engines. But if you only have to send that energy in a small beam to a sensor, the energy requirement is far less. That way you can mimic a fleet of ships without having to expend an equivalent amount of energy.

 

Assuming' date=' of course, you already know (1) where a large enough number of those sensors are ahead of time, and (2) the spectral sensitivity and other response characteristics of those sensors. I think that's sort of like assuming you've already belled the cat.[/quote']

Yep. That just means it's hard, not impossible. With the right intel, you could pull off amanojaku's decoy scheme without actually building an expensive fleet of decoy ships.

 

"Assuming you've already belled the cat" sounds like a "no true Scotsman" argument. If it works, it works.

[Markdoc]

Re: Stealth in Space

 

In short, if you shine a beam of light at me in the right way, it'll look like you're shining a much more powerful light in all directions.

 

A sensor recognizes a spaceship by actively or passively detecting various flavors of radiation emitted, reflected, refracted or obfuscated by said ship. The sum of these signals comprise a "beam" with a certain signature that strikes the sensor. A real ship will show such a signature from any direction. That's why it would take a lot of energy for a decoy to mimic a real ship's powerful engines. But if you only have to send that energy in a small beam to a sensor, the energy requirement is far less. That way you can mimic a fleet of ships without having to expend an equivalent amount of energy.

 

 

Yep. That just means it's hard, not impossible. With the right intel, you could pull off amanojaku's decoy scheme without actually building an expensive fleet of decoy ships.

 

"Assuming you've already belled the cat" sounds like a "no true Scotsman" argument. If it works, it works.

 

But it would only work if you knew where every sensor was, ahead of time - meaning that you already have acheived total superiority in terms of targetting. How you manage to locate all the sensing platforms without active scanning - which means turning yourself into giant beacon and shouting "Here I am!" - and how you manage it without lighting yourself up for the other sensors (since you'll need to hit every sensor simultaneously, otherwise you'll look anomalous to the system) .... I'm thinking it would be much more feasible to simply build a decoy the same as your actual ship.

 

And of course that still wouldn't give you stealth - it'd just make it harder to target your ship. But if you can already target every single sensor they have simultaneously .... what do you need decoys for, again? Just knock 'em out. You're going to be announcing your presence anyway.

 

cheers, Mark

[austenandrews]

Re: Stealth in Space

 

But it would only work if you knew where every sensor was' date=' ahead of time - meaning that you already have acheived total superiority in terms of targetting. How you manage to locate all the sensing platforms without active scanning - which means turning yourself into giant beacon and shouting "Here I am!" - and how you manage it without lighting yourself up for the other sensors (since you'll need to hit every sensor simultaneously, otherwise you'll look anomalous to the system) .....[/quote']

Sensors don't get stealth either, right? Anyway intel is what spies are for. If all that data is coordinated, it's cataloged somewhere. Heck, you might be getting real-time feeds, the same as your enemy.

 

I'm thinking it would be much more feasible to simply build a decoy the same as your actual ship.

Doesn't scale if you're talking about massive power generators.

 

And of course that still wouldn't give you stealth - it'd just make it harder to target your ship. But if you can already target every single sensor they have simultaneously .... what do you need decoys for, again? Just knock 'em out. You're going to be announcing your presence anyway.

Decoys are temporary feints, part of some larger tactical or strategic plan. I don't think it's difficult to imagine a scenario where such a scheme could be useful.

[Escafarc]

Re: Stealth in Space

 

I'm thinking that it will be a lot like submarine combat with ships having a "Running Silent" mode.

[amanojaku]

Re: Stealth in Space

 

Actually we are both right.

 

 

 

Early in the story the drive is called a Photon Drive, using it for communications purposes was also mentioned. Later the Kzinti Telepath lets us all know that the drive is a primitive Ramjet that is powered by incomplete fusion (whatever that means). Later ships in the setting are said to use the Bussard ramjet which does use fusion to move around. http://en.wikipedia.org/wiki/Bussard_ramjet

My bet on "incomplete fusion" would be that the humans only fused hydrogen up to helium. Maybe complete fusion would mean fusing hydrogen up to just below iron on the periodic table to get the maximum energy out of it.

 

That's just my guess, iron is the break even point on fusion, so maybe fusing to just below it would be considered complete fusion for power.

[amanojaku]

Re: Stealth in Space

 

Re decoys in space: You have a very small, cheap device designed specifically to put out as large a radiant sig as possible,and a large, expensive vessel doing it's damnedest to minimize emissions. The former could easily put out a larger signal than the latter.

 

As to active systems, a carefully designed hull can still mess with things like radar, scattering the return signal.

 

Stealth or counter detection systems in space are not impossible, just expensive, hard and not completely reliable.

[Narf the Mouse]

Re: Stealth in Space

 

I'm thinking that it will be a lot like submarine combat with ships having a "Running Silent" mode.

Except you could be seen for light-minutes from your environmental systems alone. With current equipment. So let's run this.

 

1) You start up your drive out of detection range and coast in.

2) It takes you six months to get there (Atomic Rockets page - If you want to try to understand the calculus involved, feel free. Basically, the faster your drive can accelerate, the further you have to be to not be detected).

3) In those six months, patrol craft and sensor platforms, both active (easily-detectable) and passive (much less easy to detect than you are) will be moving around - And all they need is a single positive return.

3a) Better be heading for a planet, or you'll have to adjust course. Whoops.

4) You're detectable out to 147 light-seconds (According to my quick calc I did yesterday). That's 2.47 / 8 = 30% of the distance between the Earth and the Sun, or 44,100,000 km. Pluto is 7,375,927,931 km away. Assuming we want to detect out to pluto:

4a) In a circle: 72,797,490,770 km^2 / 435,249,554 km^2 = 167.25 km^2. 168^2 = 28,224. Sounds like a lot, except it's perfectly doable for a single-system nation, given a few decades of casual building.

4b) In a sphere: 304,933,416,270 km^3 / 1,823,169,069 km^3 = 167.25 km^3. 168^3 = 4,741,632. Assuming you want to cover all approaches, it'll take 168x as long.

 

So: Assuming your target civilization is new and hasn't really researched or built Von Neuman machines, that approach may work if you come at the solar system top-down.

[Xavier Onassiss]

Re: Stealth in Space

 

My bet on "incomplete fusion" would be that the humans only fused hydrogen up to helium. Maybe complete fusion would mean fusing hydrogen up to just below iron on the periodic table to get the maximum energy out of it.

 

That's just my guess, iron is the break even point on fusion, so maybe fusing to just below it would be considered complete fusion for power.

 

"Incomplete" might also mean that some of the hydrogen is exhausted as reaction mass rather than fused. This would reduce efficiency/exhaust velocity but greatly increase thrust.

[amanojaku]

Re: Stealth in Space

 

"Incomplete" might also mean that some of the hydrogen is exhausted as reaction mass rather than fused. This would reduce efficiency/exhaust velocity but greatly increase thrust.

A good possibility. Still, whatever the hydrogen fuses too probably gets ejected as reaction mass, I imagine. So even if it was fused 100% to a higher element you'd still get thrust when you dumped it. Since angle's pencil was using a photon drive it wasn't chucking out reaction mass, maybe they fused the hydrogen up to oxygen and stopped, oxygen being useful on a ship full of live humands who want to stay that way.

[Tasha]

Re: Stealth in Space

 

"Incomplete" might also mean that some of the hydrogen is exhausted as reaction mass rather than fused. This would reduce efficiency/exhaust velocity but greatly increase thrust.

 

Perhaps what it means is that the atoms are crushed enough to generate lots of heat which could be projected out as Thrust. Their technology couldn't achieve the fusion of the atoms which would increase thrust in a huge way.

[Ian Mackinder]

Re: Stealth in Space

 

Noting also that Space Is Big. Even locating something as unstealthy as a planet could be a very big deal if you aren't certain of where to look.

[Roy_The_Ruthles]

Re: Stealth in Space

 

Planets tend to not be emitting radiation in every direction by default. That makes them fairly stealthy. Ones that are emitting radiation in all directions shouldn't be that hard.

 

As far as the beam of light trick to blind sensors, I still don’t understand how a single vector beam could imitate a wide angle signal. It should be possible to calculate the drop off of signal and thus locate the center of the beam, which is where you fire. It’s like shooting the direction that’s holding a flashlight on you, with seeking bullets. It seems like the system would have to:

 

1) Use spies to find the design and location of all sensors in a system

2) From outside detection range, blind all sensors with light speed interference.

3) These sensor beams need to outrun the light speed emissions of the ship which launched them, or else the defenders have a position fix.

4) Avoid having this single position fix triangulated, and missiles fired upon it, which would actively search for the ship as well.

 

My problem seems to be that to blind a sensor you need to have been undetected, which was the point of the decoy beams in the first place. Once you have been detected, you need to blind every missile from every angle from finding you. This also includes avoiding predicatively launched missiles, trying to intercept you if they manage to get 2 data points and plot your momentum.

 

Also, the sensors would probably be armed, since any station could have minutes, if not hours of light speed delay. At least, they would be armed if the system had any reason to expect intruders.

 

Re decoys: Any decoy would need to match the propulsion signature and momentum of the ship it is decoying. This would require it to be as massive as the ship it is decoying, which makes it almost as expensive as a real ship.

 

Stragetic stealth is possible, via launching an object with 0 ΔV, from outside detection range. I’d like to think that electromagnetic launching systems would minimize generated heat, but you would still have heat from whatever power plant did the generating. But either way, if you launched from far enough away, you could get strategic stealth, but any plan for 6 months in the future might as well have been a KE kill missile at near C speeds.

[Markdoc]

Re: Stealth in Space

 

I think that austenandrews' point was that you could "fake" mass, size and thrust by sending fake data at the signals so that your decoys didn't have to be as massive and complicated as your actual ship, since if they were, there'd be no point in having decoys.

 

I agree with you that it doesn't seem at all likely to work, since, as noted you'd have to know not only where every sensor platform was, but what it was monitoring at any given time. All you'd need to do to defeat that sort of decoy system would be to squirt one probe (or even a reflector, to give you an altered angle of attack on your signal) out on a random vector as soon as you received a potential signal - and then he's screwed.

 

Having a direct intel feed wouldn't help there (and the whole intel aspect relies on you having access to some sort of FTL communications system anyway - otherwise you'd always be behind your enemy's reactions, even if you had perfect penetration of their systems). The sensors would be sending information home and then your penetration would need to send the information to you: the time lag would be substantial - by the time you got the information, the enemy would have reacted several minutes (best case) to weeks (worst case) ago and your intel would be out of date. If we have FTL communications, we're off in rubber science territory again* - not to mention that if you have information bearing FTL transmissions you'd be able to watch your enemy's reaction to your actions prior to actually making them and then make your battle plans based on that, which makes my brain hurt to just think about it.

 

I don't think his suggestion was intended to make you stealthy, though, since by definition you are doing the opposite, when you deploy decoys. It was just a way to make you harder to shoot.

 

cheers, Mark

 

*of course if we have FTL spaceships, then we're in the rubber science zone anyway, so really, I have no problems with "cloaking systems" or massless decoys - you could produce decoys by making multiple planned entries to the system and then hiding among the echoes generated by your Schrodinger field

[Tom Carman]

Re: Stealth in Space

 

Given the practical considerations, I suspect that stealth in space would be not so much a matter of concealing your position as concealing your identity. Sensors that can detect that you are THERE likely have a lot more range than ones with enough fine discrimination to determine that you aren't who you say you are.

[austenandrews]

Re: Stealth in Space

 

I think that austenandrews' point was that you could "fake" mass' date=' size and thrust by sending fake data at the signals so that your decoys didn't have to be as massive and complicated as your actual ship, since if they were, there'd be no point in having decoys.[/quote']

Right.

 

I agree with you that it doesn't seem at all likely to work, since, as noted you'd have to know not only where every sensor platform was, but what it was monitoring at any given time.

Correct, it would only work if you had that kind of intel. You wouldn't use it otherwise. So it's probably not going to work against an entire developed system's sensor array. It would be more suited against individual ships or small stations. In any case, as noted above, decoys are transitory feints that aren't intended to stand up to prolonged scrutiny. If they're effective enough to make the enemy commit resources against them in the second or two required to get data from more remote sensors, they've done their job.

 

not to mention that if you have information bearing FTL transmissions you'd be able to watch your enemy's reaction to your actions prior to actually making them and then make your battle plans based on that, which makes my brain hurt to just think about it.

Has anyone written a story like this? I think you could hammer out a workable tactical system, given time. It's mind-bending because it's unfamiliar, rather than illogical.

 

*of course if we have FTL spaceships, then we're in the rubber science zone anyway, so really, I have no problems with "cloaking systems" or massless decoys - you could produce decoys by making multiple planned entries to the system and then hiding among the echoes generated by your Schrodinger field

Love it!

[Narf the Mouse]

Re: Stealth in Space

 

There's a large error in one certain area, though: They're assuming that the heavy material needed to make a drone isn't significantly cheaper than the expensive, high-tech material needed to make a spaceship. A drone just needs a hull, an engine and to be filled with garbage to the same weight as the spaceship it's imitating. Any stellar nation would produce significant quantities of garbage, such as gold, which is semi-useless and very heavy.

 

Of course, you still have to pay for the engine.

[Cancer]

Re: Stealth in Space

 

Gold is far from useless. As a corrosion-free coating, as an electrical conductor, as both at the same time, it's really technologically valuable, and will be for quite some time, even absent bling use.

[Narf the Mouse]

Re: Stealth in Space

 

Gold is far from useless. As a corrosion-free coating' date=' as an electrical conductor, as both at the same time, it's really technologically valuable, and will be for quite some time, even absent bling use.[/quote']

That's why I said semi-useless - We have corrosion-free coatings and we're currently developing better electrical conductors. As a generally non-alloyable, gold has limited utility.