phavoc said:
atpollard said:
Three points to make in contribution to this topic:
First, Insulation in spacecraft is kind of an odd concept because space is a vacuum ... you already have the worlds best insulation (you are a giant thermos bottle).
Second, If you posit the existence of a material that will efficiently reflect or refract heat (EM energy in the IR spectrum - or other spectrum), then it is possible to construct a Fresnel lens (like on a lighthouse) for the 'radiator' and direct your waste heat in a narrow cone. This makes your ship very bright from one specific direction and very dim from all other directions.
Third, There was some anti-radar research that involved compounds that could absorb energy in specific EM wavelengths and radiate it off in a different wavelength. In the real world, this is used for anti-radar coatings on military vehicles. If the Far Future has materials/coatings that operate on a similar principle except across a broader range of EM wavelengths, it may be possible to tune what wavelength your ship glows in. Enemy scanning for IR signatures, too bad you radiate all your waste energy in the x-ray wavelengths.
Just tossing in my 2 cents.
Use or ignore as appropriate.
Some good points. Insulation is good because it allows you to control your heat generated. So, for example, your stealthy ship retains all the heat on the inside (which is normally the greater part of it) and you can deal with it as you please. You really don't want a totally refractive hull since that, too, would reflect off into space and you'd be all nice and "shiny" on IR sensors.
The absorbtion idea is interesting. We know you can passively detect powerful X-rays, but a narrow-beam that continually changes angles and emission level might be harder to detect from normal background radiation. Having something that continually emits a stream is kind of like turning on a narrow-beam flashlight in the dark.
In theory dumping anything out behind the shadow of your ship is a good idea. Except where someone has deployed a scanner array that can look "up" and "down" from various angles and compare the results to look for sneaky people. Probably not going to be present in any low-tech system, but I would think the scan sats would be dirt cheap and spread pretty heavily around any military or A/B starport that has any risk of being attacked by the enemy or even well-organized pirates. It's unfortunate we don't yet have a really good understanding of how pirates are able to flourish raiding ships coming into planetary systems, or even on longer trips to outer planets and stations. Wasn't the new pirate supplement supposed to address some of that?
Here's an interesting exercise. take a pen light, put you hand in front of it...Now have someone walk to one side or the other until they can see that penlights bulb. A small object creates a cone hat gets wider as you move away from the source...of course you probably already knew that...but that little exercise makes the problem a lot more readily apparent.
creating a network that can see around the tiny hull of a starship to a directed energy beam..say a MASER being used to get rid of excess heat though some clever engineering. The system would have to be a large distance away from the general path of the starship..millions, or trillions of miles.
and If ya haven't been hit in the head, or hiding on some obscure thread away from the forum..I think you know how radically different and sometimes passionately opposed opinions and theories on piracy are. There isn't a neat and tidy way to deal with the issue of piracy, or for that matter stealth in space. If I could think of an idea that would satisfy everyone, or even a significant majority, I wouldn't put it here..I'd write it up, sell it to Mongoose, and watch my bank account grow.
Condottiere said:
Again, the issue that puzzles me is how much heat is there?
With a fusion reactor onboard, it could be productively channelled to it, and if you switch it off, or more likely, really power it down, for that stealth run, you could use it as a heatsink.
the primary heat source is the fusion power plant. A fusion reactor creates temperatures hotter than the surface of the sun within it's fusion chamber.
the secondary heat source is anything mechanical or electrical on the ship. Reach over and put you hand near the power supply of your desktop/laptop... that heat alone is enough to be seen one heck of a long way off..no multiply that by a few thousand pieces of electronics and machinery packed into a metal can the size of a WWII destroyer.
sooner or later that heat makes it to the exterior of the ship by one means or another. .
if you are using reactor that requires cooling or converts something into a liquid to turn a turbine You might be able to co-opt part of the cooling system, or even the fuel tanks as a heat sump. a few thousand liters of liquid hydrogen setting around waiting to be fused would be a great heat sump.
of course some out gassing would occur, but could be controlled with a system that captures the gas, then cools it back to a liquid state. that would indirectly use the reactor to cool the hull of the ship.
alex_greene said:
hiro said:
Reaction drives obviously have a heat signature, does a gravitic drive have a signature?
Possibly visual light emissions from coronal discharge, and - according to Larry Niven - an almost-coherent neutrino wake. Possibly gravitons too.
Anything that is electrically or mechanically powered has a heat signature. maybe not as spectacular as a chemical rocket or fusion torch, but it's enough to cause issues if you're trying not to be noticed.
The Heat can be dealt with by some clever engineering, and applied physics. Another source of detection from gravitics is the EM/particle noise such a system would generate. If you have ever had an OLD radio occasionally you can hear a buzzing in the signal caused by a car driving pas. the spark-plugs generate a broad, weak, radio signal as they operate. At one time most electronics generated interference on the EM band as well..although that's hardly a major issue now.
I practice it is actually possible to detect a radar detector, which is basically only a specially tuned radio receiver, by it's peculiar EM interference created when it is operating. to me that has always hinted that any drive system using a emitter of any sort can be detected and precisely tracked by its EM noise....
