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. > What's crazy about it? It appears to be more promising than anything else for > interstellar travel, unless we discover the reactionless drive that many have > proposed. But there is no reactionless drive yet. So why not try this? > >Furthermore, I think there might be a major improvement possible unless I'm >missing something. How about using thorium salt water instead of uranium? You >could start the engine with the lowest isotope concentration of uranium salt >that would start and maintain a reaction. Then when the reaction is well >established make the transition to the thorium salt water. In other words, you >would have a uranium "pilot light". > >A large container of thorium salt solution wouldn't need anything to absorb >neutrons and would be inherently stable, thereby avoiding the possibility of >catastrophic failure. The uranium salt could be kept in far smaller quantities >and would only be used to start the reaction. > >I doubt this engine would ever be built, but it's fun to speculate. [snip] Regards, Robin van Spaandonk <mixent...@aussiebroadband.com.au>
