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A core is just nuclear fuel with enough other parts that it can be handled. Of course there needs to be a control mechanism for adjusting the output, you just c

A core is just nuclear fuel with enough other parts that it can be handled. Of course there needs to be a control mechanism for adjusting the output, you just can't use that for eliminating heat output. Once the core has been turned on there is decaying fission products producing heat, that is why you can't turn off a nuclear power plant in an instant, and why you might want to get rid of the core. Unused cores can be stored with few special precautions as the unspent fuel decay too slowly to be a major hazard. The ship would carry one small nuclear reactor, and several tons of coolant/propellant. The only way the cooling system is actually going to keep up is by ejecting the hot coolant into space, which is also what creates thrust. You can't recycle the coolant as there is no efficient way to cool the coolant. In effect, if you don't want to dispose of the core you have to keep the engine on consuming coolant/propellant, depending on a lot of factors that may or may not be viable.

simonh 7y ago
>You can't recycle the coolant as there is no efficient way to cool the coolant. Alright, this is the crux of the problem. Yes you can, the ISS has huge radiator panels in it's shadow for thermal management. The shuttle also had radiator panels in the bay door structure, they were so crucial the vehicle had to re-enter soon after closing the doors to avoid excessive thermal buildup. This is a known solved problem. And that's on vehicles that aren't carrying any nuclear power systems, and just have to contend with solar radiative heating.
- NohatCoder 7y ago
  The ISS doesn't have a heat budget anywhere close to that of a reactor core, you'd need to carry a much larger radiator construction, just for this job. Extra cores cost way less weight.
  - simonh 7y ago
    But if you don’t have mechanisms to moderate those cores output, they’ll be blazing away all the time. You can’t get away from the fact you need a way to moderate the reaction, including For ‘spare cores, which you at least need a mechanism to activate, and you need an active cooling system. And on top of all that, even with reaction mass cooling the core when it’s active, that not going to be enough to capture all the generated heat.

simonh 7y ago

>You can't recycle the coolant as there is no efficient way to cool the coolant. Alright, this is the crux of the problem. Yes you can, the ISS has huge radiator panels in it's shadow for thermal management. The shuttle also had radiator panels in the bay door structure, they were so crucial the vehicle had to re-enter soon after closing the doors to avoid excessive thermal buildup. This is a known solved problem. And that's on vehicles that aren't carrying any nuclear power systems, and just have to contend with solar radiative heating.

NohatCoder 7y ago
The ISS doesn't have a heat budget anywhere close to that of a reactor core, you'd need to carry a much larger radiator construction, just for this job. Extra cores cost way less weight.
- simonh 7y ago
  But if you don’t have mechanisms to moderate those cores output, they’ll be blazing away all the time. You can’t get away from the fact you need a way to moderate the reaction, including For ‘spare cores, which you at least need a mechanism to activate, and you need an active cooling system. And on top of all that, even with reaction mass cooling the core when it’s active, that not going to be enough to capture all the generated heat.