Third-generation fusion fuels
3He + 3He → 4He+ 211
p 12.86 MeV 0 https://en.wikipedia.org/wiki/Helium-3
What about this reaction mixture? I remember hearing about it but it isn't talked about much. You could get the He3 from the decay of Tritium bred from Lithium as has been discussed, or from the atmospheres of the gas giants Saturn, Uranus, Neptune (likely not Jupiter too much radiation belts). Given the advanced fusion drives being discussed the outer solar system is obviously reachable.
The second possibility, fusing 3He with itself (3He + 3He), requires even higher temperatures (since now both reactants have a +2 charge), and thus is even more difficult than the D-3He reaction. However, it does offer a possible reaction that produces no neutrons; the charged protons produced can be contained using electric and magnetic fields, which in turn results in direct electricity generation. 3He + 3He fusion is feasible as demonstrated in the laboratory and has immense advantages, but commercial viability is many years in the future
I presume you are thinking of this for the SFS Z- Pinch and not for the Staged Z- Pinch, Giorgio and I were just talking about.
Like for D+He3 fusion, they would probably make the He3 in dedicated fusion reactors: D+D -> He3 + n (and T + p in the other branch with half the T decaying to more He3 after 12 years). I presume that the neutron from D+D->He3 could be used to breed even more T in a lithium blanket.
I see little advantage for He3 + He3 over D+He3. The cross section is smaller than for D+He3. So the gain would be lower. For a space drive, it would mean more expensive fuel. Plus, the capacitors to drive the higher current would be larger and the Z- Pinch would have to be longer. Not sure how exactly it would compare to their proposed PB11 space drive version, but that could be a useful baseline for comparisons. There would probably be some advantages in regards to less neutron shielding and the exhaust would not contain any Tritium from D+D side reactions. But I am not sure how well all that would make up for the mass gain in the other areas. Maybe some time in the far future, this would be feasible, but I would not hold my breath for the near future.