[gurps] Starship Troopers, one more time

[Anthony Jackson]

Onno Meyer wrote:
> 
> Those numbers don't look good - it takes a trivial power cell to 
> power reactionless thrusters for a few minutes.

Well, if you tweak the stats for power cells and/or reactionless 
thrusters it works. There are also various semi-plausible air-breathing 
engines which might allow high thrust for a very short time and then 
need to recharge (for example, you might have a compressor that collects 
air, and then uses it as reaction mass for a thermal rocket, possibly by 
mixing it with jet fuel. Doing some basic math, I'd expect an 
air-kerosene rocket to have an ISp of ~200 if combustion is very 
efficient, but the vast majority of reaction mass is actually air, so 
effective ISp is 1,500-2,000.