I have some remarkably good diagrams of early-program NERVA nuclear rocket designs (first half of the 1960’s), but the later, more refined designs remain a bit unavailable. (I know an archive that has several linear feet of NERVA stuff… anyone want to fund an expedition for me?) Here is an Aerojet diagram for a 75,000 lb-thrust NERVA from 1968. Compare to THIS design from 1962…
Minor update: I made an offhand mention above of getting funding for a research expedition. I’ve gotten a few responses to this, both in comments and email. So… who might be seriously interested? If I could get at least ten people to commit to pitch in $100, I’d get the process underway. The archive has several linear feet of NERVA stuff, several linear feet of Solar Power Satellite stuff, and a whole bunch of boxes of Space Shuttle development stuff (ILRV, Phase A, etc.). Ideally, I’d spend about a weeks there, scanning and photocopying. Investors would get DVDs containing scans of everything I get… excepting, of course, that non-US investors wouldn’t get any ITAR-marked stuff.