Gateworld Virtual Fleet 4.0 - Discussion thread

[Cmdr. Setsuna F. Seyei]

why do people keep saying stealth is impossible in space? can you give reasons why this would be the case?

[thekillman]

why do people keep saying stealth is impossible in space? can you give reasons why this would be the case?

One, because it's true.

I can give a one-word summary: Thermodynamics.

The problem of stealth in space can be explained a number of ways, and so i'll show a number of considerations.

Stealth works by trying to blend into your environment. Aircraft used to do so by painting their craft in bluish-white colors to make them hard to spot. With the invention of radar that was useless, so they resorted to what we think of as stealth nowadays. Radar works by shooting a beam of EM in a direction, checking for anything that bounces back and then determining the distance by time-of-flight measurement. The more EM is bounced back the bigger the target is (with respect to distance). So naturally to hide from radar you'll want to bounce back as little as possible. To do this, a bat-shaped form was developed with sharp angles and flat surfaces to scatter radar away as much as possible. To further reduce the backscatter they painted the craft with radar-absorbent paint (which happens to be black hence stealth craft are usually black).

Such a painted, sharp-angled aircraft thus bounces back as little radar EM as possible. But here's the crux: it's not invisible. Just about everything bounces radar signals back, including the air itself and various distortions, as well as birds etc. To get any sensible reading the signal is filtered. On a radar screen the difference between a flock of birds and an aircraft is easy to spot. But a stealth craft scatters back a radar signal that's very different from it's nature. The radar software can thus easily mark it as noise, an error, a bird, or anything in stead of the plane it is. You could imagine that the enemy would then simply respond to such errors, but the very point is that the signal has become more generic so they'll be sending out intercepts to birds, atmospheric effects etc too. Enemy planes would slip through. It's a matter of hiding in existing and similar signals.

Space is dark and cold. This is probably well known, but it's good to consider this: space is a couple of degrees above absolute zero. Space is a couple of degrees above absolute zero. Absolute zero.

I emphasize that a lot because imagine this: take a lump of water-ice in the winter. If you hold it, it's cold. Now magically teleport that ice into space. The ice is 273 degrees above the temperature of space. Consider ice versus boiling water. That times three is what such a lump of ice would look like in space.

Now consider a spaceship. To blend in with the rest of space it would need to be absolutely dead. 270-ish degrees below 0C. First of all metal becomes brittle so it's likely that your ship would be chipped away as micrometeorites bombard it. Those temperatures are not practical for any significant structural work. Put humans on such a craft and it needs to be hotter than a lump of earthly ice in space. Aim a telescope in the general direction and it's a Christmas tree. It's also a very unique IR signature since planets will be well-known and thus ruled out any any asteroid or comet will be cold as space. Stars have a very different signal. Check the doppler shift and you know the direction the craft is going and how fast. Perform basic calculations and you know where it can go. Missiles are ready and armed by the time any enemy craft is within a lightyear. Missiles can be fired however far their ships can go. If you got interstellar spacecraft you got interstellar missiles.

Now consider the power plant aboard a spaceship. Any meaningful spaceship with meaningful time-of-flight will have a megawatt to gigawatt powerplant. No matter what you do it's never 100% efficient so a megawatt powerplant emits kilo to megawatt heat. A gigawatt powerplant emits megawatt to gigawatt heat. Thermodynamics apply, so eventually the heat spreads through the ship and it inevitably heats up and so gets above absolute zero. Cooling is a process with a 400 to 600% efficiency. That is, 1 watt of power can pump about 4 to 6 watts of heat. Cooling power is thus a process with energies comparable to whatever you're cooling. A gigawatt reactor has a megawatt cooling installation. But there's no convection or conduction in space, so all heat has to be radiated. We're talking hundreds of square meters for a gigawatt reactor. You can't hide that. Every tiny device on the ship heats it and causes the entire thing to be a beacon of Infrared. It's a Christmas tree in the middle of nowhere in the darkest night. It's a beacon that shines for lightyears.

Herein lies that last problem of stealth in space: No environment is more sensor friendly than space. Even the radio signals we've been emitting across the globe are measurable in space. In alpha centauri they can watch our shows in good quality. It might be much worse further away, but in at least a couple of dozen lightyears they can still make out what we were watching. A ship coasting along is going to be visible as a very recognizable IR dot in the sky that everyone can see within lightyears.

Lastly, it's extremely unlikely that your ship is going to be coasting. We're talking months to years of acceleration to get to another star. For an extremely long time people are going to see the signature of an intensely hot flame that's even more visible than the already-visible ship signature. In stead of a handful of lightyears we're talking dozens. You need a crapton of energy to move between stars and it's again a lighthouse in a sea of darkness. Antimatter is by far the worst: positron-electron annihilation creates a very specific photon. If you're moving along in your antimatter-powered interstellar craft, every system within lightyears will know that you're flying an antimatter-powered ship.

So yea, in conclusion:

*Stealth in space does not work because you're hiding against the absolute cold of space. A couple of degrees above that can be noticed if you're looking for that. dozens of degrees above that and it's a dead giveaway. Hundreds above that and you're a beacon in space.

*thermodynamics means that your ship can't be that cold. Even the radiothermal generator to keep your electronics powered in sleep mode will mean that your ship is hot enough to be seen.

*you can't cheat thermodynamics.

To put things into perspective:

The Space Shuttle's much weaker main engines could be detected past the orbit of Pluto. The Space Shuttle's manoeuvering thrusters could be seen as far as the asteroid belt. And even a puny ship using ion drive to thrust at a measly 1/1000 of a g could be spotted at one astronomical unit. As of 2013, the Voyager 1 space probe is about 18 billion kilometers away from Terra and its radio signal is a pathetic 20 watts (or about as dim as the light bulb in your refrigerator). But as faint as it is, the Green Bank telescope can pick it out from the background noise in one second flat.

This is with current off-the-shelf technology. Presumably future technology would be better.

You don't need radar in space. All you need are a couple of ears to listen.

[thekillman]

Correction:

Sorry gormagon, i made a mistake. A kilogram of air is about 833liters. No way a chemical laser gun (which given the weight, i expect to be RPG launcher sized) has 833 liters of air to cool itself with in a second. Imagining a bottle of coke (1.5L) i would expect such a gun to have about 10-15 liters of air in direct contact with the gun and capable of taking the heat.

Air is about 1,2kg/m^3 which is 1,2 g/L. So we're talking 12-18 grams of air.
Conveniently, air is about 1KJ/(kg*K) so 1J/(g*K). That means 12-18 joules to heat the air by a degree.

I'll assume the heat is divided about 80/20, that is 80% to the air and 20% to the gun. The air will then heat up by 9200J or 511 degrees. At 400 degrees air takes up 1.064J/g*K. Correcting for this, we get 480 degrees air.

AKA the handheld laser is a blast furnace. Assuming i got it the wrong way around and the division is 20/80, it heats up by 2300J and thus gets to 161 degrees. At 161 degrees the air does not have a significantly increased heat capacity so this is final.

So an air-cooled gun is going to be impractical. In space it certainly is. The gun could be mass-cooled (that is, the gun acts as a heat sink) in which case you could fire maybe 30 shots before it would get warm to the touch. After 60 shots it's roughly 55 degrees (if the gun was at room temperature) and unless special precautions are made, it's going to be painful to hold. If we're talking atmospheric combat, you'd need to coat it (quite thick, talking millimeters to centimeters here) in stuff like the shuttle's heat shield to prevent a small explosion in your face. Remember, this is from 25 degrees to at least 161 degrees in ONE SECOND. At 160 degrees the air will be 20% less dense so we're talking small explosions here. In space, the weapon would not cool very fast. A water reservoir (or other heat sink) would help but even then, you eventually need to replace the coolant to bring the gun back to operating temperatures. However, since a man-to-man laser space battle is going to take place near a ship or station, it's up to you to decide whether you really want to be shooting 20 armor-piercing laser shots in an attempt to kill a human. Again these lasers won't stop until they're out of energy or too diffuse, and the first only happens after it has hit enough things and the latter only happens if it's lightseconds away.

I could improve the gun quite a bit by choosing a different material.
Silicon improves the heat capacity to 0,71KJ/kg*K so that gives about 80% more shots for mass-cooling. It's unlikely that your entire gun is silicon but i imagine various components could be.

Sodium has a whopping 1.2 heat capacity (same units as before), but is less likely as a construction material.

Magnesium has 1.05. While magnesium dust is very flammable, it's a common high-tech construction material so it may be used.

Lithium has a capacity of 3,57. It may be too reactive to be sensitive in a laser that uses a supersonic chemical reaction with highly reactive components.

Aluminium has a capacity of 0,91. This is most realistic for a ton of components. Not sure what the optics are made of, but silicon is a good guess.

All in all, the gun may at best double the shots i calculated. Counting shots went out of style with rifles but they're back in full swing with laser guns. Good luck counting the shots that completely miss (you can't see laser beams unless they hit something ).



Other considerations:
A gyrojet would work similar to a bullet, fracturing on impact and almost certainly killing whoever's hit.

A laser, not so much. To get any sensible cutting capacity we're talking lasers with a beam diameter of 0.2mm to a max of 1mm. That beam goes straight. It'll prick through armor like a needle, then prick through the body and cauterizing any wound and then prick through the back of the armor into a wall and it'll keep puncturing stuff until it's harmless or off into space.If you're hit by a 0.2mm laser cannon it'll go right through you. If it didn't hit anything too important, you'll live. So laser combat means that you need to hit people before the rest of the stuff is too damaged, you need to hit them well and your gun shouldn't melt before theirs.

[Gormagon]

uhm....

Bullets -of any kind- have an explosive in them that causes them to propel. The reason an explosive is an explosive and not just a slow burn is because they can oxidize very fast. And they can oxydize very fast because they don't need air. The explosive is self-oxidizing, that is it either is a metastable molecule (e.g. nitroglycerine) or an oxidizer/fuel mixture (IIRC most plastic explosives).

Wait a second....so your saying you could fire an Ak-47 in space? I was told that firing conventional guns in space is impossible?.........or am I misreading this....and what would that mean for vessels armed with auto cannons?

[thekillman]

Wait a second....so your saying you could fire an Ak-47 in space? I was told that firing conventional guns in space is impossible?.........or am I misreading this....and what would that mean for vessels armed with auto cannons?

You don't have to take my word for it:

http://www.livescience.com/18588-shoot-gun-space.html

https://answers.yahoo.com/question/i...7175701AAZSfmd

http://www.straightdope.com/columns/...-work-in-space

http://www.thetruthaboutguns.com/201...ience-fiction/


They all give the same reason: the bullet contains an explosive, which contains it's own oxidizer. It doesn't need air to function. Any explosive will work in space.

EDIT:

ok i'm crying. There are quite a few people that keep claiming it doesn't work because of lack of oxygen. Cmon, i learned in 3rd year of middle school(whatever the local name is, it's different for ever country) that an explosive has it's own oxygen. It's actually very hard to make an explosion from fuel+air. It requires a nearly perfect mixture of air and fuel, uniformly distributed and with maximum surface area. Frequently, a small explosion is used to create a bigger one. In SGU's Malice you can see that the explosion from the explosive device is a dust/vapor explosion as the cloud comes first and a second later it ignites.


EDIT 2:

It's actually madness if a bullet would require air to function. If you've ever seen a bullet (even a picture) you can see it's all metal. There are no air ducts to allow the explosive to soak up air. The barrel is a great pressure vat (where the bullet is a cap blowing off) so it would also be the worst design to allow air in. The bullet chamber is enclosed too, so no air refreshing there too. All in all, a bullet that required air wouldn't work.

The engine in your car needs air. Check it. It has a big air inlet in the front. A big fan to cool and suck in air. It has systems to filter the air, mix it with fuel and inject it into a cylinder. Nothing of the sorts exist in a gun. A gas BBQ or heater has massive ventilation to keep the gas burning. The gas oven sucks in air actively. Cooking on gas has the pot on a slight elevation to ensure the gas flame can breathe. Anything that requires oxygen, has either active suction or plenty of ventilation holes. A gun has neither.

[Gormagon]

Well, where I live we are ranked Horrible in the education department, world wise we don't crack the top twenty. I have had to fill in gaps myself, but there are still many.

I was informed you cannot fire normal guns in space and never thought to investigate.

[thekillman]

I had a debate about evolution. The other guys barely understood biology. Gave that one up, teaching them my 3 years of biology. You don't have tot be Einstein, sciece starts with a healthy dose of curiosity, critical thinking and fact checking.

[Cmdr. Setsuna F. Seyei]

@ thekillman what about if you had a time space bridge with a heatsink on board? wouldn't that help minimize your thermal signature?

[Gormagon]

The heat would still be easily detectable from your active power plant. The only way to get real stealth is space is with a yet unknown science, or pseudo scifi science.

Biology was actually something I did quite well in, along with creative writing, public speaking, and psychology.

My studies actually led me to believe its far more likely DNA was designed however, its far to complex to have both formed and 'written' itself so spectacularly in so 'short' of a time. Not going to say what or who though. Nor do I really want to get into it.

Oh, here, hows this work? Not my theory something I found....

Well hot plasma would be more effective, deflecting energy and vaporizing mass. But it could also melt your ship. 'Cold' plasma could be used to contain it. So what you would want to do is layer it; cold/hot/cold. That would work anywhere; in space or dirtside. Or in space, to save power, you could turn off the outermost shield and it would be just as effective.
The thing is, if this is a near-future scenario, (2064-2104) you'd better make sure its mounted on something big. Like, really big. No fighters or tanks. More like an aircraft carrier, minimum. If this is a little farther along, (2104-2204) then fighters and tanks would be acceptable. Personal shields wouldn't work for another 50 years or so at least.

We actually have the tech right now. Just not the cash. No one does. On earth. impractical, eh kinda lol plus to power this thing...maybe if we round it off a few times, we could call it 100 times the power requirement of earth per year, to run it for an hour. XD
That shield would be for something like an aircraft carrier. We could power that, though. Currently, we use fission reactors. Fusion is much more energetic. If we manage to figure that out, maybe 50 to 75 years, then you could power it. It'd even fit aboard ship lol. You want to know what your fuel would be?

Pure Water. XD

all metal and all solid matter would not melt. It would be Vaporized. Gasified. If the shield is made a certain way, all incoming matter could be made into plasma and incorporated into the shield, making it stronger.
So projectiles are of no concern.

[thekillman]

@ thekillman what about if you had a time space bridge with a heatsink on board? wouldn't that help minimize your thermal signature?

The heat would still be easily detectable from your active power plant. The only way to get real stealth is space is with a yet unknown science, or pseudo scifi science.

Cooling implies you have something colder to cool against. A heat sink isn't a magic heat disappear device. The heat sink will increase in temperature too. Consider that water can take about four kilojoules per kilogram kelvin. A Megawatt reactor (80% efficient) will be outputting 200KW of heat. It's heating up 50 kilograms (~50 liters) of water at a degree per second.

You run into scaling again. More heat sink stuff (won't be that much better than water) means bigger engine means bigger powerplant means more water etc.

Lastly, the problem isn't with your reactor. It's the engine. In many cases your engine is your reactor. Whatever you do you're spewing out hot gas/hot plasma/hot ions out the back. You need to. Anything with a reasonable amount of thrust will have flares visible for AU's. As Atomic Rocket mentioned, a torchship (a ship that doesn't need elaborate transfers but just flies straight to it's target) would have something closer to terawatt engines. Interstellar travel needs even more to be of any conceivable kind.

Lastly, a spacetime bridge is a wormhole. If we assume that one can really be made using black holes, then per my earlier post on black holes, you're moving millions of tonnes of material. A black hole supplies it's own power to move, but the wormhole you describe would not. A microwormhole doesn't work. A several million tonne wormhole would already be the size of a nucleus. For cooling it's impractical to say the least.

My studies actually led me to believe its far more likely DNA was designed however, its far to complex to have both formed and 'written' itself so spectacularly in so 'short' of a time. Not going to say what or who though. Nor do I really want to get into it.

Nature has a knack for capturing complex things in beautifully simplistic ways. But it's actually one of the few things where i can imagine people think that. Life brings quite heavy questions to the universe and we seem no closer to answering them.

Oh, here, hows this work? Not my theory something I found....

Well hot plasma would be more effective, deflecting energy and vaporizing mass. But it could also melt your ship. 'Cold' plasma could be used to contain it. So what you would want to do is layer it; cold/hot/cold. That would work anywhere; in space or dirtside. Or in space, to save power, you could turn off the outermost shield and it would be just as effective.
The thing is, if this is a near-future scenario, (2064-2104) you'd better make sure its mounted on something big. Like, really big. No fighters or tanks. More like an aircraft carrier, minimum. If this is a little farther along, (2104-2204) then fighters and tanks would be acceptable. Personal shields wouldn't work for another 50 years or so at least.

We actually have the tech right now. Just not the cash. No one does. On earth. impractical, eh kinda lol plus to power this thing...maybe if we round it off a few times, we could call it 100 times the power requirement of earth per year, to run it for an hour. XD
That shield would be for something like an aircraft carrier. We could power that, though. Currently, we use fission reactors. Fusion is much more energetic. If we manage to figure that out, maybe 50 to 75 years, then you could power it. It'd even fit aboard ship lol. You want to know what your fuel would be?

Pure Water. XD

all metal and all solid matter would not melt. It would be Vaporized. Gasified. If the shield is made a certain way, all incoming matter could be made into plasma and incorporated into the shield, making it stronger.
So projectiles are of no concern.

Would the cold plasma not rapidly become really hot plasma? *

I would like to point out that vaporizing a projectile doesn't do all that much important. you'll still be hit. Unless you can do it a few projectile-seconds out as the expansion speed is a couple of thousand meters per second. (hence projectile-seconds. If it's faster you need to kill it further away)

Several times the power supply of the earth is a LOT of power. At that point you could invest in a Cosmic Ray Laser and still puncture through that shield.


* I must say that thin film physics is quite a different beast than a regular lump of anything.



Though if i were you, i'd go with cold plasma shields that make lasers less effective, and so tip the balance to ensure kinetic weapons like railguns are possible.

[Gormagon]

So, plasma shields. Effective against directed energy weapons, and in some ways against ferromagnetic projectiles. Not fool proof, not a force field.

[thekillman]

Mostly just lasers. Particle beams may have more spread out damage but their energy is so high they cant be stopped by it

[Cmdr. Setsuna F. Seyei]

@ the killman I was referring to the McKay spacetime bridge like the one in s5 ep 16 Brain Storm

[thekillman]

@ the killman I was referring to the McKay spacetime bridge like the one in s5 ep 16 Brain Storm

Well if anyone can explain to me what it is precisely, i'd be happy to talk about it. A space time bridge by definition is a wormhole. I don't know what makes that one from brainstorm so different. I could look into it more but... Wormholes as stargate has them is not how wormholes work. Well they got the basic principle right but that's it. On the other hand, if SG had realistic wormholes they'd not have stargates to begin with so i can see why they took some liberties.

So yea i'll look into it

EDIT:
Thinking about it....

The device sucks away heat, that much is made apparent in Brainstorm. So i would say that for cooling the ship it's fine. The main problem remains: that the engines would flare up on every telescope. You can accelerate lightyears away and coast in relative coldness. It may not be picked up by your average telescope. However, remember that we're building massive telescopes to look into the background radiation, which is just a few degrees above absolute zero. If we can see the background radiation and the IR of faraway stars, then a ship a few degrees above zero is still spotted. It doesn't have to be spotted dozens of lightyears out. At any kind of cosmic distance the enemy has weeks to prepare and fire long-range missiles.

Secondly, because of the laws of thermodynamics (can't win, can't break even and can only lose) the bridge would not cool perfectly so the ship would always stay above absolute zero. Not to mention that because heat flow is a function of a temperature gradient, the cooling would go excruciatingly slow at the last hundred or so degrees.

Lastly, as you coast through space relatively cold hoping no telescope is aimed at you, you still need to slow down and again flare up your engines for however long you accelerated. Even firing your maneuvering thrusters would be noticeable. You can't cool your exhaust (well not without wasting a ton of energy and thrust) as the heat of the nozzle flame is exactly what you need to go forward.


Although i would file this under "magic" because the matter bridge simply doesn't exist in this state. The diagrams in Brainstorm make it clear that it's a wormhole. Stargate wormholes are magic.

[Gormagon]

" The cold plasma and hot plasma are different types of plasma the heat transfer would not effect it/you can replace the layers. " ???????


So, any further details on the effectiveness of plasma shields/electromagnetic shields/layered or whatever against the following: Rail cannons/Coil guns/auto cannons , proton beams, neutron beams, infrared lasers, x ray lasers, gamma ray lasers, nuclear fission/fusion devices, EMP, and radiation bombs?

Or any thoughts on "expanding metal foam" and metal foam in space ships and space craft construction in comparison to nano material, advanced composites and super alloy?