[Spaceships] getting into orbit without superscience?

[Varyon]

Originally Posted by Fred Brackin

Only the exhaust is hydrogen or maybe water. Bombarding those with neutrons causes no serious radiation problems.

If you're using hydrogen (and you want to use hydrogen for the Isp) the most you can get is tritium when one of your neutrons hits a deuteron (i in 7000 of hydrogen atoms).

If you're in atmosphere, even if you aren't using a ram-rocket design I think your exhaust would contain free neutrons, which would interact with the atmosphere to generate secondary radiation. I'd still count that as "radioactive exhaust" - although I'll admit when I'm thinking of NTR in atmosphere, I'm generally thinking of a ram-rocket (and outside of atmosphere, the radiation hazard of the exhaust probably doesn't matter - it's primarily an environmental concern, after all). Although maybe those free neutrons were what you were talking about when you said "traces of the fissionable core?"

EDIT: Of course, I could be wrong and the intent actually is that flakes of the fissionable core are somehow getting into the exhaust. That just strikes me as a monumentally poor design. Of course, looking through SS1, I see no indications that any of the drives have radioactive exhaust, so I assume that information is in a different book?