Actually, yeah, i like the idea of it being clouds of plasma freezing and dispersing (as a result of freezing...superheated plasma, well it wont be plasma anymore if it aint hot!)...stratcomm hit the nail on the head...if it looked like ICE coming out of the ship though it might look somewhat more interesting ^^ but not fire...it always looks funny when you see things "burning" in space --- there are some things about space sim video games that are "wrong" that actually make it feel cooler (like condensed nebulae) --- and there are other things, like burning things as if there is air, which don't XD
*COUGH* Freelancer is extremely guilty of that...the ships burn like matches when they're about to die