follow-up: here is what wolfram alpha spits out for a 0.1 grams dust particle hitting you at 0.08c: https://www.wolframalpha.com/input/?i=1%2F2+*+10%5E-4kg+*+(

follow-up: here is what wolfram alpha spits out for a 0.1 grams dust particle hitting you at 0.08c: https://www.wolframalpha.com/input/?i=1%2F2+*+10%5E-4kg+*+(0.08c)%5E2 https://www.wolframalpha.com/input/?i=1%2F2+*+10%5E-4kg+*+(0... it's 35% of the fission energy released by totally fissioning 1g of U-235! i.e. I don't know whether this it's feasible to just have a heavy water & lead shield, as 0.1g is fairly optimistic to be the heaviest particle hitting you. Already at this size we're in range of tactical nuclear weapons.