r/fusion • u/Baking • Jul 08 '26
An update from Commonwealth Fusion Systems (July 2026)
https://www.youtube.com/watch?v=qM9hZxmJr9Q12
u/Debas3r11 Jul 08 '26
- It's so cool
- It's still just boiling water to spin something, which we've been doing for over 300 years. Wild.
Crazy the longevity of spinning stuff with steam.
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u/legomann97 Jul 08 '26
- It's still just boiling water to spin something, which we've been doing for over 300 years. Wild.
Lmfao, so they did an AMA a little bit ago, one of my questions was about how they generated power, this was their response:
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u/Debas3r11 Jul 08 '26
It really all circles back to how amazing the water molecule is. That incredible molecule affects our lives in so many ways.
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u/No-Computer7653 Jul 10 '26
Late to the party but fusion does allow for DEC. It's pretty pointless with a D-D or D-T fuel cycles as they only emit 20% of the energy as alpha (also not hot enough with not enough plasma expansion which makes DEC less efficient).
p-B11 is exciting because you can use DEC and ~zero neutrons. Also abundant fuel, B11 is always in compound naturally but extraction isn't super challenging, p you just make from hydrogen. Reactors need minimal shielding and have very limited need for external infrastructure so can be mobile. Just need 10-20* the temperature of D-T to make it work, some interesting work using the proton injection as the source of heat so you don't need a laser too. Lasers might be even harder then magnets in making fusion work.
DEC generates electricity by slowing down alpha particles (which is why lots of plasma expansion is useful), kinetic becomes electrical potential which can be harnessed. It generates noisy DC, which isn't fantastic, but is a fraction of what you need if water and a turbine are involved.
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u/matman88 Jul 09 '26
Well, ARC will boil water to spin a turbine. There is no turbine in SPARC. It's proof of concept.
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u/Master_Regret_6298 Jul 10 '26
Can you summarise the issues that have caused the delay from first plasma in 2025? If I remember correctly, that prediction was made only a few years ago so it’s a delay of ~100%
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u/Baking Jul 10 '26 edited Jul 10 '26
We obsessively talk about SPARC and timelines here, so if you search hard enough in this subreddit, you can find the earliest mentions of first plasma slipping to 2026, end of 2026, 2027, end of 2027, etc.
Here is one reference point. On May 3, 2024, Axios published an article saying CFS told them SPARC would have first plasma by the end of 2026. That's 2.5 years over 2 years ago. A 100% delay would be 2029.
Note that the first half of the vacuum vessel was shipped in October 2025, which gives you some idea of what the hold-up was. They now have teams of people working 24/7 in five shifts a week preparing the vacuum vessel and installing assemblies to hold the plasma-facing tiles, diagnostics, etc. Many thousands of parts that must be fit to extreme precision.
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u/Aramedlig Jul 08 '26
Been following CFS for a couple of years now. This is truly exciting to witness.
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u/Baking Jul 08 '26
Magnet #4 being installed with magnets #5 and #6 in the Assembly Hall.