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Re: starship-design: Staged Fusion Power
Multistaged fusion all the way up to iron should be theoretically possible,
but the yield isn't spectacular more than a well chosen single stage:
( I) 1 (2H) + 2 (3He) -> 1 (4He) + 1 (1H) + 18.4 MeV
(II) 24 (2H) + 2 (3H) -> 1 (54)Fe + 401.4 MeV
24 (2H) means 24 atoms of Hydrogen, where the Hydrogen has atomic mass 2.
Reaction (I) is the most efficient single fusion reaction.
Reaction (II) is the short-circuit of the multi stage fusion.
The input mass of reaction (I) is 1*2 + 2*3 = 5
The input mass of reaction (II) is 24*2 + 2*3 = 54
So we can repeat reaction (I) 54/5=10.8 times before we've used the same
amount of mass as needed for reaction (II).
Doing reaction (I) 10.8 times will yield: 10.8*18.4=198.7 MeV
So fusing all the way to Iron has a yield (401.4/198.7)=2 times better than
fusing merely to light elements.
So, all the trouble (eg. higher fusion temperature, unwanted fusion
ractions) for a two times higher yield, is likely not worth it.