Open Circuit Turbine...

[Caseck]

'Nother idea for propulsion in a vaccum. You could have a supply of liquid hydrogen/helium/methane etc... You apply heat to said liquid, either from antimatter annihilation or conventional battery/electric. You allow said gas to escape into vaccuum via turbine. You can either link said turbine directly to a transmission or to a generator for power.

Again, this allows indigenous refuelling where helium/nitrogen/CO2/O2/methane liquid or ice is available.

Drawbacks? Thermal signature of escaping heated gas. Unless actual oxidation of the mixture occurs, it's not going to be a bigger signature than naturally occurring geysers and so forth, but it will be noticable. If actual oxidation (combustion) occurs in the turbine, it will be a much larger signature, but then again, it'll produce much more power.

[Cameroon]

I would almost not worry about thermal signatures if I were in a vacuum. If you're on the "cold" side, no matter how small your signature you should show up very clearly since there is extremely little, or no, ambient heat. If you're on the "hot" side, then thermals could very well be entirely useless.

I did say "almost not worry"

[Caseck]

The funny thing about a thermal sig, is it is very much line-of-sight. Looking forward, yes, maybe there is some spill, but in vehicles without a LOT of heat output, or "being sneaky" you can mask that heat output. Especially if you know where the guy is looking at you from, and have a system (which is suprisingly rudimentary at the moment in real life...) you can block thermal imaging very effectively.

It isn't a "Blip-I-see-you" super camera or anything. In many ways it's probably more limited than the visible light spectrum. Not better, just different really...