4 ms·

I believe a tank full of liquid hydrogen would be a reasonable neutron radiation shield. Generally things like water or concrete are used for neutron radiation

• senectus1 6y ago
  yeah but you "burn" that shielding as you go... slowly depleting it as you get faster and further away.
• m4rtink 6y ago
  On NTRs (and space reactors in general) you only need a "shadow shield" that casts a radiation shadow in the direction of thing to protect (crew, sensitive systems). This makes the necessary shielding much less than a full sphere, reducing the mass to a mere fraction. Thing get a bit hairy though when you need to dock with something or even when running multiple engines (the neutron balance would apparently be totally wrong).
• valuearb 6y ago
  You want to be careful to avoid heating your hydrogen fuel, it’s slowly evaporating through the tank even when near absolute zero, any significantly higher temperature is going to increase that rate.
  • bigbubba 6y ago
    I envision the tank being between the engine and the capsule, not wrapped around the engine or something like that. As another commenter points out, you only need a shadow shield. I don't think there would be much more heat transferred from the engine to the fuel tank than in traditional engines; the neutrons would warm up the fuel some but perhaps naively I assume that effect would be fairly small. Now that I think about it more, I'm not sure. Is it the neutrons that heat the water in a nuclear reactor?