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I'd still like to know how they plan for a potential explosion of the space craft carrying the fuel inside the atmosphere. They better have a good story on that

I'd still like to know how they plan for a potential explosion of the space craft carrying the fuel inside the atmosphere. They better have a good story on that. Even if the rocket breaks up and the fuel reaches ground in perfectly sealed containers, that still doesn't mean the danger is over.

throwaway4aday 4y ago
I imagine step one is to launch from the coast heading out over the ocean. If Starship is fully operational by then it would be the obvious choice and depending on the reactor design there might be enough weight capacity to build in some extra shielding. I also wonder if the fuel can be shipped separate from the reactor.
philipkglass 4y ago
The fuel doesn't become dangerously radioactive until after the reactor powers up for the first time. The uranium fuel is only about as toxic as something like barium or lead until the chain reaction starts generating fission products. This is in fact safer to launch than past space missions such as Pioneer, Voyager, and Cassini. Those used radiothermal generators that were far more radioactive and hazardous than a fresh reactor core.
credit_guy 4y ago
The same plan as for all the countless cases when they sent radioisotopes in space. Perseverance and Curiosity each have 4.5 kg of Plutonium-238 on board. Did that worry you?
- bayesian_horse 4y ago
  Yes. And the lunar reactor will require more power and thus more fuel.
  - philipkglass 4y ago
    The plutonium 238 fuel in RTGs has a half life of 87.7 years: https://en.wikipedia.org/wiki/Plutonium-238 https://en.wikipedia.org/wiki/Plutonium-238 Uranium 235, the fuel used in reactors, has a half life of 703.8 million years: https://en.wikipedia.org/wiki/Uranium-235 https://en.wikipedia.org/wiki/Uranium-235 This means that plutonium 238 is roughly 8 million times as radiotoxic as uranium 235, gram for gram. If this mini-reactor carries 4.5 tonnes of fuel it will be 0.012% as dangerous at launch as the power source for the Curiosity rover.

throwaway4aday 4y ago

I imagine step one is to launch from the coast heading out over the ocean. If Starship is fully operational by then it would be the obvious choice and depending on the reactor design there might be enough weight capacity to build in some extra shielding. I also wonder if the fuel can be shipped separate from the reactor.

philipkglass 4y ago

The fuel doesn't become dangerously radioactive until after the reactor powers up for the first time. The uranium fuel is only about as toxic as something like barium or lead until the chain reaction starts generating fission products. This is in fact safer to launch than past space missions such as Pioneer, Voyager, and Cassini. Those used radiothermal generators that were far more radioactive and hazardous than a fresh reactor core.

credit_guy 4y ago

The same plan as for all the countless cases when they sent radioisotopes in space. Perseverance and Curiosity each have 4.5 kg of Plutonium-238 on board. Did that worry you?

bayesian_horse 4y ago
Yes. And the lunar reactor will require more power and thus more fuel.
- philipkglass 4y ago
  The plutonium 238 fuel in RTGs has a half life of 87.7 years: https://en.wikipedia.org/wiki/Plutonium-238 https://en.wikipedia.org/wiki/Plutonium-238 Uranium 235, the fuel used in reactors, has a half life of 703.8 million years: https://en.wikipedia.org/wiki/Uranium-235 https://en.wikipedia.org/wiki/Uranium-235 This means that plutonium 238 is roughly 8 million times as radiotoxic as uranium 235, gram for gram. If this mini-reactor carries 4.5 tonnes of fuel it will be 0.012% as dangerous at launch as the power source for the Curiosity rover.