Well Robin, that certainly bursts my thorium bubble. Should have thought of that myself. It's still not a crazy idea. And as you point out, plutonium could be even better. The main problem with the whole concept is that it would really have to be built in space. Testing this out in the atmosphere would be like a continuous Chernobyl.
On Tuesday, May 4, 2021, 08:44:45 PM GMT, Robin <mixent...@aussiebroadband.com.au> wrote: In reply to Michael Foster's message of Tue, 4 May 2021 20:14:00 +0000 (UTC): Hi, Thorium isn't fissile by slow neutrons, only by very fast neutrons, and then the reaction cross section is hundreds of times lower. So the very thing that keeps it safe to store would likely also make it unusable. Though it is fertile, the conversion to fissile takes time, that would not be available in a rocket engine. (The half life of Th233 is 22 minutes, and that of Pa233 is 27 days). In a ground based reactor, you just leave the Th233 & Pa233 sitting around until they slowly convert. Of course, you could do the conversion to U233 on the ground first, (or in orbit for that matter), then fuel the rocket with U233, but that is essentially the same thing as using U235.
