re: Fission powered rockets
I've heard of Orion, I read Dyson's article on it. It would have worked, but where would you test it?
Have you heard of NERVA? I don't remember exactly what the acronym means, but it was a fission-powered, liquid hydrogen reaction mass reactor engine, with an effective specific impulse about 2 or 3 times that of H2/O2 combustion. A full scale prototype was actually successfully static tested in the 60s, but it was abandoned too because of safety reasons. Somebody described it as getting the power of a Hoover Dam out of something the size of a piano.