Somewhat relevant, folks here might also be interested in a whitepaper we recently put up on arXiv that describes what we are doing at Pacific Fusion: https://arxiv.org/abs/2504.10680
Section 1 in particular gives some extra high-level context that might be useful to have while reading Sam and Scott's update, and the rest of the paper should also be a good introduction to the various subsystems that make up a high-yield fusion demonstration system (albeit focused on pulser-driven inertial fusion).
Any truth to that?
Modern lasers can also repeat shots much more quickly. Power gain on the capsules appears to scale faster than linear with the input power, so getting to practical gain might not be as far off as it appears at first glance.
These are some of the reasons that various fusion startups are pursuing laser fusion for power plants.
Bear in mind that I wasn't directly involved, and this my impression picked up from conversations during my time in fusion research, which was about 10 years ago.
https://lasers.llnl.gov/about/what-is-nif
>NIF is a key element of the National Nuclear Security Administration’s science-based Stockpile Stewardship Program to maintain the reliability, security, and safety of the U.S. nuclear deterrent without full-scale testing.
So it seems more likely to me that some physicists figured out how to get their fusion power research funded under the guise of weapons research, since that's where the money is. NIF's original intent was mostly weapons research but it's turned out to be really useful for both, and these days, various companies are attempting to commercialize the technology for power plants.[3]
[1] https://theaviationist.com/2025/04/26/us-nuclear-weapons-wil...
[2] https://www.fusionindustryassociation.org/congress-provides-...
[3] NYTimes: https://archive.is/BCsf5
The purpose of it is to show that the USA is still capable of producing advanced hydrogen bombs. More advanced then anybody else.
The '2.05 megajoules' is only a estimation of the laser energy actually used to trigger the reaction. It ignores how much power it took to actually run the lasers or reactor. Even if they update the lasers with modern ones there is zero chance of it ever actually breaking even. It is a technological dead end as far as power generation goes.
The point of the 'breakthrough' is really more about ensuring continued Congressional approval for funding then anything else. They are being paid to impress and certainly they succeeded in that.
However I suspect this is true of almost all 'fusion breakthroughs'. They publish updates to ensure continued funding from their respective governments.
People will argue that this is a good thing since it helps ensure that scientists continue to be employed and publishing research papers. That sentiment is likely true in that it does help keep people employed, but if your goal is to have a working and economically viable fusion power plant within your lifetime it isn't a good way to go about things.
If the governments actually cared about CO2 and man-made global warming they would be investing in fusion technology and helping to develop ways to recycle nuclear waste usefully. Got to walk before you can run.
There's "breakeven" as in "the reaction produces more energy than put into it", and there's breakeven as in "the entire reactor system produces more energy than put into it", which isn't quite the same thing.
Energy gain (in the general sense) is the ratio of fusion energy released to the incoming heating energy crossing some closed boundary.
The right question to ask is then: “what is the closed boundary across which the heating energy is being measured?” For scientific gain, this boundary is the vacuum vessel wall. For facility gain, it is the facility boundary.
On the other side of the coin, if you put 10kWh in and get 10kWh of fusion out, that's 20kWh to run a steam turbine, which nets you about 8kWh. So really you need to be producing 15kWh of heat from fusion for every 10kWh you put in to break even.
Availability (reliability engineering) https://en.wikipedia.org/wiki/Availability
Terms from other types of work: kilowatt/hour (kWh), Weight per rep, number of reps, Total Time Under Tension
Additionally the final plot of scientific gain (Qsci) vs time effectively requires the use of deuterium-tritium fuel to generate the amounts of fusion energy needed for an appreciable level of Qsci. The number of tokamak experiments utilizing deuterium tritium is small.
Here was my completely layman attempt to forecast fusion viability a few months ago. https://news.ycombinator.com/item?id=42791997 (in short: 2037)
Is there some semblance of realism there you think?
Mind you, it's not useless! It produced a TON of very useful fusion research: neutral beam injectors, divertors, construction techniques for complex vacuum chambers, etc. At this point, I don't think it's going to be complete by the time its competitors arrive.
One spinoff of this is high-temperature superconductor research that is now close to producing actually usable high-TC flexible tapes. This might make it possible to have cheaper MRI and NMR machines, and probably a lot of other innovations.
I'm sure there'll be plenty of fascinating applications of high-Tc tape, however I'm not sure MRI/NMR machines will be one of those. There would still be a lot of thermal noise due to the high temperature. Which is why MRI/NMR machines tend to use liquid helium cooling, not because superconductors capable of operating at higher temperatures don't exist.
ITER has been criticized since early days as a dead end, for example because of its enormous size relative to the power produced. A commercial follow-on would not be much better by that power density metric, certainly far worse than a fission reactor.
There is basically no chance than a fusion reactor operating in a regime similar to ITER could ever become an economical energy source. And this has been known since the beginning.
I call things like ITER "Blazing Saddles" projects. "We have to protect our phony baloney jobs, gentlemen!"
Much of the interesting tokamak engineering ideas were on small (so low-power) machines or just concepts using high-temperature superconducting magnets.
There's the common joke that fusion is always 30 years away, but now with the help of ITER, it's always 10 years away instead.
The idea of using literal guns (gunpowder, then light gas gun, then coil gun) to impact projectiles against each other seemed like it was probably ludicrous, but I haven't seen any critical media or numbers yet.
(it's been 30 years away for 50 years already, but as long as I'm not dead 30 years from now, it's still a good investment...)
I want to believe, but this does not make that easier.
(I work for one startup in the field, Commonwealth Fusion Systems. We're building our SPARC tokamak now to demonstrate net energy gain in a commercially relevant design.)
https://www.metaculus.com/questions/9464/nuclear-fusion-powe...
