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You could say the same thing about Bitcoin. Fusion is in the VC hype cycle but there are no new developments that suggest it can become cheaper and more predict

You could say the same thing about Bitcoin. Fusion is in the VC hype cycle but there are no new developments that suggest it can become cheaper and more predictable than fission, which itself is dying, primarily because of financial uncertainties and risks. On the contrary, physics suggest that performance scales with size, so even the extraordinary expensive ITER project is way too small to achieve engineering break even, let alone financial break-even. You will only hear about scientific break-even, which is a useless milestone because, yes, you get more energy than you put it, but you put electric energy and get fast neutron energy, only you need an order of magnitude more of that to get back the electricity you put in. Understanding different types of break-even would be an obligatory primer to anyone navigating hyped fusion claims: https://news.newenergytimes.net/2022/04/08/fusion-q-values-and-breakeven-explained/ https://news.newenergytimes.net/2022/04/08/fusion-q-values-a...

pfdietz 4y ago
Fusion reactors (after they're big enough to have ignited) have diseconomy of scale, due to the square-cube law. Cost scales (at least) as reactor volume, while power is limited by power/area through the surface of the reactor vessel.
- manholio 4y ago
  But are we hitting that power density ceiling yet? It doesn't seem so, we're not even in the "big enough to have ignited" range, only scraping at the door of "big enough for scientific break-even", but have already blown any reasonable chance for such designs to be cost effective even if they were to be mass produced. Massive superconducting magnets generating megatons of force, building-sized vacuum chambers that are almost guaranteed to leak some amount tritium, which only adds to the unavoidable regulatory burden imposed by the fast neutron environment, activated structure and every day production of weapon-grade material etc. etc., even if the current technology magically works tomorrow, it's still an economic dead-end. The present fusion crop is megascience at its worst, draining public funds for something that can't possibly ever work and producing very little substantial science in the way. We need to take a step back and reassess. At least Helion is trying a new path, even if they are likely to end up in a similar dead-end.
  - pfdietz 4y ago
    It's not clear there's ANY window for DT reactors between "too small to ignite" and "too large to have competitive volumetric power density".

pfdietz 4y ago

Fusion reactors (after they're big enough to have ignited) have diseconomy of scale, due to the square-cube law. Cost scales (at least) as reactor volume, while power is limited by power/area through the surface of the reactor vessel.

manholio 4y ago
But are we hitting that power density ceiling yet? It doesn't seem so, we're not even in the "big enough to have ignited" range, only scraping at the door of "big enough for scientific break-even", but have already blown any reasonable chance for such designs to be cost effective even if they were to be mass produced. Massive superconducting magnets generating megatons of force, building-sized vacuum chambers that are almost guaranteed to leak some amount tritium, which only adds to the unavoidable regulatory burden imposed by the fast neutron environment, activated structure and every day production of weapon-grade material etc. etc., even if the current technology magically works tomorrow, it's still an economic dead-end. The present fusion crop is megascience at its worst, draining public funds for something that can't possibly ever work and producing very little substantial science in the way. We need to take a step back and reassess. At least Helion is trying a new path, even if they are likely to end up in a similar dead-end.
- pfdietz 4y ago
  It's not clear there's ANY window for DT reactors between "too small to ignite" and "too large to have competitive volumetric power density".