6 ms·

Absolutely not, in space you have the option of jettisoning the core, carrying coolant for a controlled shut down is a waste of weight. You might even go as far

Absolutely not, in space you have the option of jettisoning the core, carrying coolant for a controlled shut down is a waste of weight. You might even go as far as having 4 disposable cores, one for each acceleration stage.

dvdhnt 7y ago
Serious questions... Would the core just float off into space? Couldn't it make its way back to Earth? Or compromise potential life on Mars?
- ceejayoz 7y ago
  It's pretty straightforward to put it in a safe, permanent orbit. https://en.wikipedia.org/wiki/Graveyard_orbit https://en.wikipedia.org/wiki/Graveyard_orbit
baybal2 7y ago
Brilliant solution man. Additional nuclear fuel, unlike the popular belief says, will not be taking any much significant weight. A critical mass of plutonium is only 10kg, and you will likely have it reduced with moderation and reflectors. If you have to keep disposing heat away from a powered down, but still residually active core, you will have to keep a no joke mass of radiators just for that.
dogma1138 7y ago
Not sure why this is being downvoted jettison the core would likely be the go-to solution you can put into a stable orbit or even set on course with the sun and let it burn off... There is no much need for a complex control mechanism in fact keeping those core as orbital modules on mars would likely allow you to skip many of the complications of having a complex control system to prevent a run away effect and modulate power output no one really cares if the core would go critical even at low orbit on Mars as there is so much radiation there from natural sources anyhow. If the core goes critical mid way then either have a fallback core or just jettison it and wait for a rescue mission. The vessels would likely have enough supplies for such occasions and as far as risk to the crew goes nuclear propulsion in space is much less dangerous than chemical propellants that can actually explode. With a nuclear core you can safely vent hydrogen and xenon to space not worrying that much about radiation or long term contamination the cores can be more or less exposed with large fin stacks for radiative cooling.
- kwoff 7y ago
  "set on course with the sun and let it burn off" - https://laughingsquid.com/why-it-is-more-difficult-to-crash-into-the-sun-than-leave-the-solar-system/ https://laughingsquid.com/why-it-is-more-difficult-to-crash-...
simonh 7y ago
So you would not build in mechanisms to moderate the heat output of the core, and have it generating at full power constantly? Ok, what state is the core in before you want to fire the engines? Suppose you want to burn to leave Earth, and agin to slow down at Mars, what happens to the engine core on the coasting period of many months in between? If you're carrying several disposable cores, if there's no way to moderate their output how do you store them safely when not in use and switch them on? Also, whole propulsion cores are lighter than the cooling system for a single core? Really?
- NohatCoder 7y ago
  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.

dvdhnt 7y ago

Serious questions... Would the core just float off into space? Couldn't it make its way back to Earth? Or compromise potential life on Mars?

ceejayoz 7y ago
It's pretty straightforward to put it in a safe, permanent orbit. https://en.wikipedia.org/wiki/Graveyard_orbit https://en.wikipedia.org/wiki/Graveyard_orbit

baybal2 7y ago

Brilliant solution man. Additional nuclear fuel, unlike the popular belief says, will not be taking any much significant weight. A critical mass of plutonium is only 10kg, and you will likely have it reduced with moderation and reflectors. If you have to keep disposing heat away from a powered down, but still residually active core, you will have to keep a no joke mass of radiators just for that.

dogma1138 7y ago

Not sure why this is being downvoted jettison the core would likely be the go-to solution you can put into a stable orbit or even set on course with the sun and let it burn off... There is no much need for a complex control mechanism in fact keeping those core as orbital modules on mars would likely allow you to skip many of the complications of having a complex control system to prevent a run away effect and modulate power output no one really cares if the core would go critical even at low orbit on Mars as there is so much radiation there from natural sources anyhow. If the core goes critical mid way then either have a fallback core or just jettison it and wait for a rescue mission. The vessels would likely have enough supplies for such occasions and as far as risk to the crew goes nuclear propulsion in space is much less dangerous than chemical propellants that can actually explode. With a nuclear core you can safely vent hydrogen and xenon to space not worrying that much about radiation or long term contamination the cores can be more or less exposed with large fin stacks for radiative cooling.

kwoff 7y ago
"set on course with the sun and let it burn off" - https://laughingsquid.com/why-it-is-more-difficult-to-crash-into-the-sun-than-leave-the-solar-system/ https://laughingsquid.com/why-it-is-more-difficult-to-crash-...

simonh 7y ago

So you would not build in mechanisms to moderate the heat output of the core, and have it generating at full power constantly? Ok, what state is the core in before you want to fire the engines? Suppose you want to burn to leave Earth, and agin to slow down at Mars, what happens to the engine core on the coasting period of many months in between? If you're carrying several disposable cores, if there's no way to moderate their output how do you store them safely when not in use and switch them on? Also, whole propulsion cores are lighter than the cooling system for a single core? Really?

NohatCoder 7y ago
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.