4 ms·

Well fusion would be too exotic to be developed in this century unless there is some unbelievable breakthrough but it is very realistic that all the micro-nucle

by ck2 2y ago

Well fusion would be too exotic to be developed in this century unless there is some unbelievable breakthrough but it is very realistic that all the micro-nuclear-reactor research & development being invested into by datacenter giants now might power a spaceship someday a decade down the road? (the engine development would also have to advance obviously but not implausible)

throwanem 2y ago
It's been studied in the past (NERVA, et al.), and does seem to offer a specific-impulse advantage in the extremely high temperatures achievable by routing propellant through the reactor core. (So-called "closed-cycle" systems heat reaction mass outside a fairly conventional primary coolant loop; "open-cycle" doesn't have a coolant loop, but rather ejects hot coolant directly as reaction mass. There was also a nuclear-powered cruise missile design, I think called "Project Pluto," on this theme, although not directly related and so far as I know only studied in theory.) It does of course still require reaction mass, but theoretical efficiency seems higher than other feasible systems; it wasn't really explored much in the old days due to the general post-Apollo builddown, and also due to the concerns of radioactive debris in case of mishap and radioactive exhaust if the system were used as a launch motor. (If not used to launch, it would need some orbital assembly and a lot of heavy lift, given not least the massive shielding required for remotely survivable crewed use.) Another fission-based propulsion system, not relying on a steady-state reaction, was also studied under the name "Project Orion." I'll leave that one as a diversion for the interested reader, mainly because it seems unlikely anyone not already familiar would believe a word of any description I could give.

4 ms·

Well fusion would be too exotic to be developed in this century unless there is some unbelievable breakthrough but it is very realistic that all the micro-nucle

by ck2 2y ago

throwanem 2y ago
It's been studied in the past (NERVA, et al.), and does seem to offer a specific-impulse advantage in the extremely high temperatures achievable by routing propellant through the reactor core. (So-called "closed-cycle" systems heat reaction mass outside a fairly conventional primary coolant loop; "open-cycle" doesn't have a coolant loop, but rather ejects hot coolant directly as reaction mass. There was also a nuclear-powered cruise missile design, I think called "Project Pluto," on this theme, although not directly related and so far as I know only studied in theory.) It does of course still require reaction mass, but theoretical efficiency seems higher than other feasible systems; it wasn't really explored much in the old days due to the general post-Apollo builddown, and also due to the concerns of radioactive debris in case of mishap and radioactive exhaust if the system were used as a launch motor. (If not used to launch, it would need some orbital assembly and a lot of heavy lift, given not least the massive shielding required for remotely survivable crewed use.) Another fission-based propulsion system, not relying on a steady-state reaction, was also studied under the name "Project Orion." I'll leave that one as a diversion for the interested reader, mainly because it seems unlikely anyone not already familiar would believe a word of any description I could give.