From https://astralcodexten.substack.com/p/open-thread-232: "Speaking of turning money into big positive impacts on the future, Sam Altman writes in to say he enjoyed the recent book review of The Future Of Fusion Energy, and that he predicts Helion (the fusion startup he’s a leading investor in) has a 85% chance of Q > 1 D-T fusion by 2024, and a 65% chance of Q > 1 D-He3 fusion by 2026."
Apr 14, 12:53pm: Will Helion achieve breakeven deuterium-helium-3 fusion by 2026? → Will Helion achieve breakeven deuterium-helium-3 fusion before 2026?
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No one has even come close to Q=1 on D-T with magnetic confinement yet. The big result last year was “Q>1” on ICF when you ignore 99% of the energy used to power the lasers because it doesn’t go into the fuel. D-He3 requires 8x higher temperatures to reach the same reactivity, which both increases radiative losses and makes it harder to maintain enough density (and the reaction rate is proportional to density squared)
D-He3 is so much harder than D-T that they'd have to be commercially mass producing D-T reactors before I'd take any of their D-He3 plans seriously.
@jack I interpreted it as “before”, but I’m not sure that’s what Altman meant… it might be more likely that he meant “by the end of”.
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