NASA had the Prometheus concept study on such nuclear options for a while, but I believe the huge amount of waste heat and penetrating radiation from the reactors was not considered to be particularly science-friendly. The huge amounts of power they produced somewhat offset those concerns, though. JIMO would have kept the reactor at arms length from the spacecraft. About 20 meters away, in fact, on a loooong truss lined with thermal radiator panels to dump the waste heat! Prometheus was, of course, canceled as a result of the belt-tightening that Constellation imposed, as that architecture metamorphosed into one in which new “game changing” technologies were not considered high value as they are now.

BTW, I see that I referred to a “fusion” reaction once in my last post. Wishful thinking! I meant “fission”, of course.

We even borrowed a couple in the 90’s (sent them back when the contract ended). Several missions were proposed using reactors – remember the Jupiter Icy Moons Orbiter concept?

a really good piece by Jim Oberg

Robert G. Oler

That’s correct, but understand that there is a fission reaction going on in commercial reactors. That’s what “reactor” means. You have neutrons instigating a fusion reaction that produces heat. That isn’t how an RTG works. It isn’t a “reactor”. An RTG works entirely using the heat released by radioactive decay to generate electricity. The planetary astronomy community is asking for RTG isotopic material.

Now, that being said, is would be quite wonderful to get a space qualified reactor that could be used for all manner of amazing things. Power, propulsion, etc. etc. That’s been the dream of space enthusiasts for generations. The planetary astronomy community would LOVE to be asking for fission fuel, but someone has to come up with a reactor first.