this post was submitted on 05 Jun 2026
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Commonwealth Fusion Systems (CFS) has verified the core plasma physics assumptions for its upcoming ARC fusion power plant following a peer-reviewed study published in the Journal of Plasma Physics.

The research confirms the ARC reactor design aligns with known physics, allowing the company to shift its focus toward detailed hardware engineering...

According to the validated models, the ARC plant will produce approximately 1.1 gigawatts (GW) of fusion power to generate 400 megawatts (MW) of net electricity for the grid...

CFS engineers are using this simulation framework to optimize upcoming design iterations, adjusting dimensions like tokamak width and divertor length to refine reactor performance before manufacturing begins.

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[–] SynonymousStoat@lemmy.world 65 points 5 days ago* (last edited 5 days ago) (2 children)

Just watched a really good and incredibly informative video on this, https://youtube.com/watch?v=nt4rZgndOoE. From what is explained in the video is that this is mostly filing paperwork, they haven't verified their reactor works or that it's able to output power, let alone output more power than what is required to start and maintain a fusion reaction. So over all, a little exciting, but really nothing to get too excited about yet.

Edit: grammar fixes

[–] Tetsuo@jlai.lu 24 points 5 days ago (11 children)

Ah I was wondering this and my cursory search result was that :

  • Their design (ARC) is sound for its physics.
  • their design would produce more energy if nothing goes wrong with the hardware.
  • The hardware is designed but not built yet.

Basically it's really promising because on paper it should really work as expected. But at the same time without building it, there will be obstacles along the way. The materials could last too little time for it to be commercially viable.

So they seem to be at the very last theoretical step of fusion energy but there is still a huge challenge in actually building the thing and most importantly, it to be viable commercially.

[–] echodot@feddit.uk 9 points 5 days ago

Fusion power is still basically TRL 3 and every time it looks like they might be going to move up a level everyone loses their damn minds. It's not really possible to put a timeline on any of this because the technology doesn't exist yet and we can't simulate in computers what we've never seen before, not with any degree of accuracy.

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[–] LibertyLizard@slrpnk.net 8 points 5 days ago

Yeah this feels more like a long-shot gamble by a hungry start up that the beginning of a new transformative tech.

[–] saimen@feddit.org 19 points 5 days ago (2 children)

The research confirms the ARC reactor design aligns with known physics

That's...assuring? I guess?

[–] LodeMike@lemmy.today 14 points 5 days ago

"We aren't completely batshit insane!"

[–] davetortoise@reddthat.com 8 points 5 days ago

Physically possibility is one thing. Materials and engineering constraints are another thing entirely.

Physically possible =/= Feasible.

That’s incredible. I hope it happens in my lifetime.

[–] LovableSidekick@lemmy.world 9 points 4 days ago* (last edited 4 days ago) (1 children)

Amazing. Fusion has been 20 years away since I was in school 50 years ago. I know this isn't the actual reactor but it's a big step - so maybe 10 years now?

[–] Cocodapuf@lemmy.world 2 points 4 days ago* (last edited 4 days ago)

Honestly, less. At least less for a working fusion reactor. Probably 10 - 20 before first commercial deployment.

[–] squaresinger@lemmy.world 21 points 5 days ago

So we only need 23 of them to power that one new data center in Utah.

[–] Cocodapuf@lemmy.world 9 points 5 days ago (1 children)

My bet has always been on Commonwealth Systems getting there first. But they aren't there yet... so time will tell.

Helios also has a really novel reactor, it would be amazing to see that work. It's arguably a much more elegant design than a tokamak.

[–] Mister_Hangman@lemmy.world 2 points 4 days ago (1 children)

Sure but who can get to market the fastest and have a product that can easily adapt to the needs of data centers?

[–] Cocodapuf@lemmy.world 3 points 4 days ago* (last edited 4 days ago) (2 children)

Well to be honest, I personally think that data centers are a huge waste of this emerging technology, but yeah, I suppose it's probably a perfect use case for fusion...

My question, is who can miniaturize their technology sufficiently to put it in a spacecraft? When we get fusion reactors in space we'll be able to use electric propulsion to make vehicles with insane range. We could send humans to Jupiter in a matter of months and have plenty of propellant for a return trip in a perfectly reusable vehicle. We already have all the tech for this, all except a suitable power source.

[–] gandalf_der_12te@feddit.org 1 points 3 days ago (1 children)

we can already put a nuclear fission power plant into a spaceship to generate very fast effective exhaust velocities.

i'm not sure what the exact reason is why we aren't doing this already, but i suspect it has a lot to do with ease-of-use and price being significantly on the side of chemicals

the only reason why we use nuclear power on submarines at all is because there's literally no other power source for them. they have to stay underwater for weeks / months, chemical fuel to run life support system for that long would be difficult to bring, no solar energy because underwater, battery would be insanely heavy ... nuclear is the only option there.

that's not true for spaceships. for launch, chemicals are available and cheaper / fire up faster. for mid-flight, solar panels are available.

[–] Cocodapuf@lemmy.world 1 points 3 days ago

i'm not sure what the exact reason is why we aren't doing this already, but i suspect it has a lot to do with ease-of-use and price being significantly on the side of chemicals

Well the reason we don't have nuclear thermal rockets boils down to budget cuts at NASA and environmental/safety concerns around nuclear. We made significant progress on two different nuclear rocket designs before they were scrapped for entirely political/budgetary reasons. And by budgetary reasons I don't mean that the program proved to be too expensive or difficult, I mean that NASA's annual budget was year after year and they simply had to drop some projects.

That's not true for spaceships. for launch, chemicals are available and cheaper / fire up faster. for mid-flight, solar panels are available.

Chemical propellants are great for launch, but the advantage of nuclear for deep space missions are really immense. The additional efficiency means you can make shorter trips, bring more supplies, and have more redundancy for equipment failures. It also provides the possibility of bringing the entire craft back home for future missions rather than simply expending it.

And as a power source, solar is fine around earth. But for trips further out, like to Jupiter, well at that distance your panels would only get about 4% of what we get here around earth... That's just not going to cut it for crewed missions.

Honestly, spacecraft are probably the absolute best use case for fusion power. They're one of the few contexts where the energy density is extremely important and the high cost is still worthwhile.

[–] ironycanal@lemmy.dbzer0.com 2 points 4 days ago (1 children)

Not in the top five problems of a Jupiter trip.

[–] Cocodapuf@lemmy.world 2 points 4 days ago (1 children)

Power and propulsion aren't in the top 5 problems?

Well enlighten me, what's more important that we haven't figured out?

[–] ironycanal@lemmy.dbzer0.com 1 points 4 days ago (1 children)

Keeping a human alive healthy and capable of re-entry.

[–] Cocodapuf@lemmy.world 2 points 3 days ago* (last edited 3 days ago) (1 children)

We've done that. The ISS has been occupied for the last 25 years uninterrupted. The space station can go months between resupplies. In other words, we've shown that a crew can survive in a spacecraft without aid from earth for months. With some mission specific planning, I don't see why we couldn't manage a 6 month mission.

[–] ironycanal@lemmy.dbzer0.com 0 points 3 days ago

You're the expert.

[–] CapuccinoCoretto@lemmy.world 13 points 5 days ago (3 children)

Isn't this how Half-Life began?

[–] SynonymousStoat@lemmy.world 37 points 5 days ago (1 children)

No, that had nothing to do with fusion or fission. The Resonance Cascade was a quantum event created when Gordon inserted a Xen crystal sample into a Anti-Mass Spectrometer.

[–] sundray@lemmus.org 15 points 5 days ago (1 children)
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[–] qupada@fedia.io 18 points 5 days ago (1 children)

They're waiting for you Gordon... In the test chamber

[–] hume_lemmy@lemmy.ca 9 points 5 days ago (1 children)
[–] sem@lemmy.blahaj.zone 5 points 5 days ago

Gordon doesn't need to know all that!

[–] MalMen@masto.pt 4 points 5 days ago

@CapuccinoCoretto @Delta_V cant wait to have another being attatch to my head

[–] Kevlar21@piefed.social 9 points 5 days ago (2 children)

I thought this was 30 years away?

[–] Warl0k3@lemmy.world 15 points 5 days ago* (last edited 5 days ago)

(I feel the need to point out that it's been 30 years since people started saying this...)

Oh man though this one is cool - I have a dear dear friend working on this project, and it's absolutely wild. Nothing they're doing is new, exactly but modern magnet designs have enabled SPARC to simultaneously hit a bunch of metrics that were previously entirely reliant on purpose-built machines.

Excerpt from them when I asked them about this yesterday:

While no existing tokamak has reached the same parameters that SPARC will simultaneously, there is empirical evidence in part for all of the major parameters it seeks to reach. the purple dot is ARC, the power plant design, and the red X is ITER, the gigantic international tokamak being built which doesn't take advantage of newer and more powerful magnets (which is what allowed SPARC/ARC to have much smaller volume)

so like yeah, we've built a ton of reactors that could do all this individually and then CFS have managed a system that has combined those results into a single machine and that has been the big goal for years (beyond stopping the plasma from fizzling out). There's still challenges to solve, but this system has cleared all the previous hurdles (barring some of the noncritical ones). It's so damn cool. It's not fusion happening now, the headline is sensationalist, but it's the biggest step forward we've had probably since research into plasma fusion started.

[–] SaveTheTuaHawk@lemmy.ca 3 points 5 days ago

This just says in theory it should work. In practice, it might never work.

[–] eleitl@lemmy.zip 5 points 5 days ago

Validate sustained 10:1 energy excess and tritium breeding excess, at an economically acceptable price point first.

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