Lawrence Livermore claims a milestone in laser fusion | Hacker News Reader

Lawrence Livermore claims a milestone in laser fusion

physicstoday.scitation.org

564 pointsfurcyd292 comments

The article mentions losses at the hohlraum but doesn't mention losses in the laser. "Ignition" means they controled the implosion well enough to break (almost) even on laser energy, but the laser itself is less than 1% efficient on wall power. Input energy to the entire system is over 400 MJ per shot. Even at max theoretical fusion yield, it wouldn't come close to breakeven.

There's also a firing rate issue. Even if the system produced net power, significant production would require many shots per second. Currently, the laser flash lamps are expendable and it takes on the order of a day (and lots of money) to prep for each shot.

Some of these drawbacks were addressed in the LIFE proposal, which would use fusion neutrons to burn fission fuel in a blanket around the fusion chamber. You could burn spent reactor fuel subcritically (no fission chain reaction), for example. But then it's a fission machine, and criticality excursions aren't much of an issue in conventional fission reactors. In the end, there are many drawbacks and little benefit with such a setup -- even if it worked.

I love lasers, and NIF is a marvel. But there really is no sensical story about power production in it. Even the machine's stated purpose -- stockpile maintenence -- is highly dubious. It is really an elaborate welfare machine, given to weapons scientists in exchange for their support of testing bans.

I think your take on this is accurate, but it’s a little deeper than a welfare program. The government needs to maintain a population of cleared scientists who know how to calculate things like fusion yields, simulated with classified codes. These fake fusion energy programs contribute to that; some of the most capable scientists don’t want to work on weapons, so they can kid themselves that they are working on “energy”.

There is no reasonably foreseeable future with fusion as part of the electricity grid. Even if we got fantastically lucky and were able to build a practical (magnetic or inertial) reactor in 50 years, by that time improvements in energy storage and transmission technologies will have allowed renewable energy to dominate, and no government would be crazy enough to permit it to be built.

http://progressive.org/op-eds/let-cut-our-losses-on-fusion-e...

> some of the most capable scientists don’t want to work on weapons, so they can kid themselves that they are working on “energy”.

This should be highlighted.

Anecdotally, I have a friend who worked at Macdonald-Detweiller on algorithms for handling the controlled descent of autonomously-guided aircraft when lacking propulsion and relying solely on gliding. She was horrified when I told her she was working on smart bomb guidance systems.

By what deductive reasoning process, and evidence, made you come to that conclusion?

The flight profiles of a guided bomb - and a glider aircraft - are very different. I appreciate there’s a lot of dual-use, but I’m skeptical someone could be working on something so central to the system and not know what it’s really for - all of the stories of internal-disinformation I’ve heard about from the defence sector were all to keep “peripheral” workers quiet.

Nope, newer guided bombs are almost all of the glide variety, see the SDB/Stormbearker and JSOW. They can achieve high glide ratios similar to aircraft, can follow pre programmed waypoints, have variable terminal profiles including the ability to attack from different directions, and can loiter. Speaking as someone who just left that industry, she was 100% working on glide bombs.

I'll admit I was thinking more of JDAMs than those glide-bombs... huh TIL! Thanks!

She gave me a great many more details than what I shared, and they weren't important for sharing the anecdote.

That anecdote reminds me of the big twist in "Real Genius", an otherwise comedic film.

Wow, what did she think it was for?

Clearly, delivering cuddles and cookies to the destitute.

In a sense, we programmers who work on ML are just as guilty. It seems to be used primarily for for surveillance and reliably scalable automation of centralised control of industry and society.

We're just cattle killing cattle

Defeatist. Most of us are able to say no to such jobs.

Not OP, but it could also be used in engine-out situations on drones or de-orbiting satellites.

She'll probably be suitably shocked again for the next guy that comes along and explains what she's really doing to her.

What motivation is there for her to falsely say she's shocked?

Not wanting to admit that she knows perfectly well what it is she is doing, seems to be the obvious explanation. Like, what else could it be; how could one not understand that this must be it?

Couldn't she have just not told dleslie the details? dleslie said the friend gave dleslie many more details. If the friend was ashamed of what she was doing, I think it would have been much simpler for her to only say very briefly what she worked on, like flight control software, but not go into any details and say it's confidential.

Intentionally giving a ton of details that will lead to dleslie figuring it out seems counter to her goal of not admitting what she's doing. Also her giving out this information sounds like it might actually be breaking confidentiality agreements.

If you're not familiar with different types of bombs and weapons then you might not have even heard of a glide bomb before. And someone else suggested engine-out situations on drones or de-orbiting satellites.

Spoiler alert, but this reminds me of that Orson Scott Card novel

> These fake fusion energy programs contribute to that; some of the most capable scientists don’t want to work on weapons, so they can kid themselves that they are working on “energy”.

This sounds quite anti-progressive and anti-scientific, I have trouble understanding where this sentiment comes from. If Fusion reactors could be realized, this would solve all energy problems. As you mention, renewables done right doesn't stop at production but also includes global deployment of Smart Grids and Energy storage capabilities. It's nuclear energy done in a reasonable way. Apart from that, it's really not clear if production fusion reactors will ever be possible so it's clearly a research topic. Perhaps better availability of computing power (to engineer the confining magnetic fields) and better abilities to orchestrate such complex projects will also help if you look at the challenges of the ITER project.

“This sounds quite anti-progressive and anti-scientific, I have trouble understanding where this sentiment comes from.”

It can’t be, it was first published in the Progressive.

It comes from my scientific knowledge of the field and is my factual description of what I personally observed, working on-and-off in both magnetic and inertial fusion for many years. My motivation is not anti-scientific but in defense of real science that is not getting done because of the billions wasted on fake energy projects.

I read your article here [1] and I've found it a bit problematic.

You don't give a real foundation impetus to 'stop' fusion research other than the perception not making enough progress in general terms, and that the money could be used on renewables.

It's a problematic argument because 'a few billion' is a very, very small amount of investment for an energy potentially which could yield significant results, even decades away.

It maybe a 80 year-long project, even then, it would be worth it.

Renewables are not suffering from money otherwise allocated to Fusion.

I think if you gave some very specific arguments as to why some investment will not work - even as an experimental vehicle - that would lend more credibility to your argument, but then you'd also have to have that view corroborated in some way aka 'this experiment does not materially advance science, and they know it, here is the evidence or logic'.

[1] https://progressive.org/op-eds/let-cut-our-losses-on-fusion-...

Are you saying that no energy projects should be funded or that there are better uses of energy funding (and if so which areas)?

"there are better uses of energy funding (and if so which areas)?"

He said so somewhere else. I would assume:

batterie, electrolyse, fuel cells, more flexible energy grid, solar panel as light weight foil ... all that works already today and can be greatly improved.

Fusion is awesome. And we can greatly benefit from it, someday. But to me it sounds like scam if it is advertised as the energy solution. Not when we are still at the stage of basic research (except for bombs).

Till then I would rely on the very big working fusion reactor we have: the sun.

> If Fusion reactors could be realized, this would solve all energy problems.

If fusion reactors could be realized, they'd likely be so Rube Goldbergish and expensive that no one would want them.

There's this tendency to conflate "getting a fusion reactor" and "getting a fusion reactor that actually makes sense to use". The former, while difficult, is likely MUCH easier than the latter.

The first computers were massive Rube Goldberg machines the size of industrial buildings which cost a fortune and were useful only for the militaries of nation states. Now machines with a billion times the number of transistors fit in our pockets.

Projects like ITER and NIF are monstrously complex because they are science experiments where lots of things need to be varied and we don't even know what it is we need to do. An economical reactor designed by people who knew how to make such a reactor would look remarkably different.

Reasoning by analogy is not valid reasoning.

With old and new computers, the physics are different - what makes the principles still work is that logics are the same, both have gates, memory etc.

With fusion you still have the same physical substrate you need to affect.

Also you have something backwards in your reasoning. Real production systems are usually much more complicated because they need to stay up all the time, witness real nuclear power plants with their little armies of engineers, operators etc. versus the simple research reactors of old times.

I was not reasoning by analogy, I presented an example that contradicts the claim that machines meant for widespread adoption must resemble their experimental form.

The laws of physics are unchanged, computers improved because of clever workarounds that allowed us to accomplish the same tasks in easier ways. Practical fusion reactors need to produce power via fusion, but beyond that the how is irrelevant. Swap out different lasers, different magnets, different power supplies, hell even the fuels might be different, it's frankly ignorant to claim that these changes are the same physics but "use a shorter wavelength in your fab" isn't.

A modern computer in terms of number of logic gates is astronomically more complex than ENIAC, however what matters for practicality is not complexity but cost. The cost of complexity decreases as you learn what you're doing. Chicago Pile 1 cost $17 million in today's dollars to produce about half a watt of thermal power, or $34,000,000/Wth. A modern nuclear plant costs about $2/Wth. ITER will cost $45 Billion to generate 500 MW. If fusion sees 0.001% of the economic improvement that fission experienced, that's $0.52/Wth.

The conclusion that DT fusion reactors will be expensive follows from basic engineering considerations on heat transfer, not from specifics of any design. The volumetric power density will be lousy, so cost will be high.

> A modern nuclear plant costs about $2/Wth

This may have been the projection before the AP1000 and the EPR flamed out. In practice, the cost can escalate well above that. Their complexity made them difficult to build. And yet, these designs have reactor power densities orders of magnitude better than ITER, and are far simpler (and more fault tolerant) than a fusion reactor would be.

The cost is not a function of volumetric power density. I believe we have had this conversation before.

The most expensive nuclear plant projected to be constructed is the Hinkley Point C reactor. With all its overruns, it's projected that the cost will be £23 Billion, which works out to $3.37/Wth. $2/Wth is a $6 billion 1000 MWe plant, quite typical. Note that this is for reactors in the west, in China, where non-technical issues like NIMBYism aren't a concern, the cost is closer to $1/Wth.

> The cost is not a function of volumetric power density. I believe we have had this conversation before.

Yes, and you failed to make the case that larger things aren't more expensive than smaller things (all else being equal, but note that fission reactors are made of steel, not the complex sophisticated equipment of fusion reactors). We can continue the argument here, if you can come up with any argument for your position that makes any sense.

We have simple research "fusion reactors", to the point where we know a lot about fusion. That's not the hard part. Making the real production system is the hard part.

Maybe some vested interests don't want to solve energy problems. Didn't the cotton industry kill hemp in the early 30s or so? And created the whole Reefer Madness scare?

Why wouldn't the natgas and upstream/downstream petroleum industry want to do the same thing with any potential competitors? There is already propaganda about windmills killing seagulls and windmills being ugly, so why not take it an extra step and flash pictures of thalidomide babies and then say "wow do you really want this?" with respect to nuclear? Seems totally within the realm of possibility.

EDIT: Correction - I think I actually meant the petroleum industry when I was referring to cotton in this post. What killed the hemp industry in the 50s (I said 30s earlier but I made a mistake) apparently was the availability of inexpensive, manufactured synthetic fibers.

This is deeply fascinating to read.

But what about projects like Iter? There's a lot going on in fusion that has no alternative government justification. Surely those provide little to no value for weapons programs.

If fusion for grid-scale energy is really accepted to be non-viable (and if we're honest... it is) then that has some pretty far-reaching consequences.

I don't think that fusion is categorically non-viable, but the approaches of the currently funded megaprojects all seem to be. More creative and compact approaches could still have potential. Of course, there's always PACER, which illustrates our cognitive dissonance.

There are plenty of true believers working in fusion energy. Enough to support big projects like ITER.

But consider this analogous situation. I was working in a government physics lab when Star Wars (excuse me—SDI) was still a program that you could get money from for all kinds of projects. Nobody—I mean nobody—actually doing research believed in the program. That we would actually build a Star Wars defense shield to make Ronald Reagan proud. But they happily sent off grant proposals and were glad to accept money to work on various things. You can spin lots of pet projects so it sounds like they are all about missile defense. But the algorithms I worked on, during my brief involvement, would have been more useful for game design.

Out of curiosity, are you familiar with Project Excalibur at all? I’m curious how the simultaneous-targeting of dozens of reentry vehicles from a single fission-explosion-powered sea-urchin multi-laser was supposed to work. Going by leaked and declassified material I’ve seen the concept was too far developed for it to have been laughed-out of the room, so what’s the story?

…or any other juicy bits you got for us?

Doesn’t ring a bell, but I’m not an expert in Star Wars stuff. I don’t know if this qualifies as juicy, but let me just point out, as a general strategy, that if your boss puts you on a project that you don‘t want to work on, and you are in a position to ensure that the project will lose its funding by failing to meet its milestones...well, you can‘t work on a project that doesn’t exist.

> you can‘t work on a project that doesn’t exist.

You've lost me :S

It's still around, they just changed the name. And it's still a boondoggle.

Fusion isn’t just about grid power. In terms of covering the needs for food, shelter, etc the Hubble telescope, cassini probe, large hadron collider etc are useless. However, there’s plenty of economic capacity to push limits simply to explore what’s possible and what’s out there.

Fusion is likely the energy source of the future and that’s ok. It’s ok to dream of far future deep space colonization, and take just one tiny step closer to that dream.

Mass, sustainable renewables with large energy-storage systems do kinda make fusion unnecessary though.

Places with existing gas and oil, and maybe even coal, power stations aren’t going to tear them down when fusion becomes do-able or even economically viable. Not just due to the sunk-cost fallacy but because they don’t want 10,000+ newly unemployed workers who honestly probably won’t retrain for fusion. And more reasons like that.

I think you overestimate how much companies care about their existing employees. If firing 90% of them is significantly more profitable that’s what their going to do. Solar is so cheap largely because it needs very few workers per GWh so they can fire people.

I personally doubt Fusion will be significantly cheaper than Fission let alone coal any time soon. But, if it happens their not going to care about their workforce. That said, fission > fusion isn’t going to require more training for most of the workers. In many locations they would both have identical cooling towers for example.

Who knows, fusion could be key to accessing the next order-of-magnitude level for society. Perhaps it'll be key to large scale carbon sequestration to stabilize future climate change effects.

If we had cheap Fusion tomorrow we could replace much of fossil fuels with synth fuels with neutral CO2 cycle. We get to reuse existing infrastructure but without massive co2.

It could, but IMO it's a very low odds bet. There are fundamental physical reasons why fusion reactors will struggle to compete. Fusion is a technology that IMO persists on cultural momentum, a meme technology that is part of the future because that's a story that we've been told since the 1950s. I think the most likely end will be that controlled fusion will go into a similar niche as dirigibles and vacuum tubes as a retrofuturistic anachronism. It will be recognized as something that used to be part of the future, but no longer is.

It might be be cheaper than fission. More complex reactor vs less need for thick containment walls and likely fewer NIMBY issues. Decommissioning costs are likely significantly lower. Operating costs and downtime are more questionable as you don’t need nearly as much security or to deal with enrichment and spent fuel. No need for radioactive plumbing etc. Even just constructing fuel rods is shockingly expensive.

D-T requires extracting tritium from a breeder blanket which will likely be very expensive. But the ratio of T:D can be lowered the more efficient the design, with pure D-D designs avoiding that issue entirely.

Here is an article about the probably unavoidable downsides of fusion [0], from the Bulletin of Atomic Scientists. To summarize their points:

- neutron bombardment, the unavoidable consequence of the only realistic fusion reaction, deuterium + tritium, turns every known material brittle and radioactive; and can be trivially used for uranium enrichment

- tritium is almost impossible to contain, and requires fission plants to create - the fusion plants could theoretically create a surplus, but they would have to recapture essentially 100% of a very hard to capture gas (today they normally leak about 10% of the injected tritium)

- fusion plants need to be massive to be even close to break-even - the energy drain of the facility consumes a sizeable portion of the generated energy; most of this power drain is still required while the facility is not operating the reactor, increasing projected costs of running a facility

- ICF tech is very close to fusion weapon tech, so there is a massive risk for proliferation from there as well; MCF tech is not, thankfully

[0] https://thebulletin.org/2017/04/fusion-reactors-not-what-the...

I don't think the containment (and a containment will be needed) will be significantly cheaper. The fusion reactor itself is much larger, and accessing it (like, lifting the top off an ARC reactor) will require considerable volume. ITER has a large volume around it where robotic servicing equipment can be arranged to get inside the reactor.

All this volume will have to be hermetically sealed from the outside world, since it will become permeated with tritium. Keeping that tritium from escaping the building will be a major headache (polymer seals cannot be used on penetrations, as tritium permeates through polymers). This will be true in any fuel cycle using deuterium, not just DT, since D+D -> T+p reactions will be occurring.

> Keeping that tritium from escaping the building will be a major headache

JET already had robust procedures for handling Tritium. It wasn’t that difficult because we are talking about such small amounts and the T is lighter than air so minute releases aren’t a major public hazard. Don’t forget Fission reactors actually produce Tritium.

A commercial reactor will involve far larger amounts of tritium, and the structure of the reactor will be so hot that tritium will permeate through it. The amount of tritium made and consumed in a 1 GW(e) DT fusion reactor in a year would be enough, if it were all released, to raise two months of the entire flow of the Mississippi River above the legal limit for drinking water. Containment is going to have to be extremely good.

Their never going to have a full years tritium on hand so that’s kind of an odd benchmark. Getting the cost of Tritium down to $10,000 per gram is somewhat optimistic, significant effort is going to be used to recover it.

As to the Mississippi River flow estimate that’s something like 6 orders of magnitude larger than what I am referring to. Still, the other way of looking at that statistic is if half of the Tritium used per day was dumped into the Missisippi every day it would be considered safe to drink when well mixed.

That figure was to point out the large volume flowing through the system. Containment will have to be very good. Only a tiny percentage of that tritium can be allowed to escape.

Realize also that what has to be constrained is the cumulative leakage from all fusion power plants, not just a single one. The world would need on the order of 10,000 1GW power plants, to displace fossil fuels.

That’s moving the goalposts, the US only has 95.5 gigawatts of nuclear power and it’s moving away from nuclear. At that level even just 99.9% containment you can replace all US fission reactors and have 1/10th the annual releases your concerned about spread across a much larger area.

Globally, I do think fission or potentially fusion has a minor role because it could be important for a few countries locally even if it’s not cost effective in most areas. But realistically their only really competing with each other.

It's not moving the goalposts, it's describing the scale of the problem. If fusion won't be addressing a significant fraction of the CO2 problem, it will be because it's inferior to the non-fossil energy sources that are. In which case, why is it even needed?

Nuclear fission looks unable to compete with renewables at current prices in almost all the world. There's a zone around Poland where it does the best. But even those zones go away as renewables and storage proceed down their experience curves. If there are very minor niche uses, fission would work just fine vs. fusion, particularly in high latitude countries that are already members of the nuclear club.

> In which case, why is it even needed?

Circling back to my original post, it’s clearly not needed any time soon. I think it’s worth doing in much the same way building the ISS was worth doing. That said, I was trying to avoid being dismissive of possible upsides which seem unlikely but still possible.

Whatever the opposite of devils advocate is.

Don't get too fascinated by the takes you hear about on Hacker News, as many of these comments are written by software engineers as they are by deeply embedded domain experts.

A lot of the posters on hacker news have just mastered the cynical take. It’s an ego booster for people who can’t handle that there are other people out there accomplishing things.

The cynical take is a product of talking to engineers, not scientists.

The tragedy of engineering is that in any market niche, generally only one technology can win. The others are driven to extinction. It's like ecology's "one niche, one species" rule. As Freeman Dyson pointed out, this is not like science, where multiple complementary theories may coexist. We build chips from silicon, not GaAs or superconducting niobium or any of the other possible technologies that were considered over the decades.

An engineer, if he's old enough, will have seen many technologies come up then fail and die. There are more ways to solve problems than there are sufficiently distinct problems, so this is inevitable. When fusion competes with fission, and wind, and solar, and geothermal, and..., it's a fight to the death. The notion that fusion is inevitable is a stacking of the mental deck to just assume fusion will win this competition.

A HN user’s cynical take on other HN users’ cynical takes. Masterful.

I'll take that bet - say, $500 in 2021 dollars, that a fusion power plant is selling energy to the grid? I'll even make it easier and halve the time you suggested to 25 years, so we can settle the bet in 2046.

I’m interested, but the bet needs another condition, to exclude toy demonstration projects. The reactor will have to generate at least 100MW (far less than existing coal plants) and be in operation for an integrated time of at least 90 days over the course of any one year on or before 2046. Accept?

100MW seems like a substantial moving of the goalposts, given your earlier statement that "there is no reasonably foreseeable future with fusion as part of the electricity grid" and that I've already cut the timetable by 25 years :) That said, I'll still accept - I'm emailing you at your profile address for the details!

"Practical" is in there.

A price competitive 10 MW generator probably meets that standard though (Islands, small towns, isolated mills, etc).

...very fast spaceships for the solar system, interstellar big ones probably. With continous thrust.

That would likely not demonstrate grid comparable cost though.

I didn’t mean to move the goalposts. I just want to exclude demonstration projects that might produce some net energy but not be serious commercial sources of electricity. But thanks for accepting anyway.

I've sent an message to the address listed in your profile, it's coming from a nonstandard domain though, so if you don't see it, it may be in spam. Also, I now realize that the longbet page is still under review, so you might not be able to see that either until the staff approve it.

I wonder how many of the bets on the longbets site stem from HN discussions. Probably not a significant number, but it would be deeply interesting to go back and read the discussions that spawned them.

Longbets should include a link to the thread in question in the bet.

Edit: Would be nice to have a link to refer back to the discussion that led to the bet. To my knowledge, most bets do not provide such a citation.

Is that a prescriptive or descriptive statement? I just looked at about 20 and didn't see anything immediately obvious, but that was with in page text search, and not actually paying attention enough to tell whether it's common or encouraged to include a link to online discussions in general (and I would happily search for a data set or scrape the data if I could expect to find it there).

Seems like any profitable plant should count. Some designs work best at smaller scales, but if they worked out they'd be cheap and for more power you just build a lot of them. Even in fission, there's a big push now to build reactors small enough to mass-produce in factories. Maybe say at least 100MW total power?

Energy has the most externalized costs of any industry.

The 5th fleet is in the Gulf to protect the flow of Oil.

The USD is backed to some extent by petrodollar, and that is a geopolitical hammer the Americans like to use at least to some extent.

So what does 'profitable' mean?

If Climate Change gets really problematic quickly, then guess what, all Nuclear Plants become considerably more profitable because the government will socialize the losses in case of catastrophic failure meaning owners don't pay for massive insurance costs which are a problem for profitability today give the possibility of $100B payouts in the case of failure.

I'm wary of the commentator's cynicism. If we can make demo plants operating at some scale, close to break even in 25 years ... then that's a strong hint there's material progress, and that those plants could be breaking even another 25 years later.

It also easily justifies a number of scientists working on it now even if only pans out in 50 years. The long term surpluses are potentially ginormous, like, to the point where they existentially shape the future, much like carbon fuels triggered the industrial revolution.

Yeah maybe leave out "profitable," it's too fuzzy and hard to verify. One of the bettors simply expressed skepticism that there would be "fusion as part of the electricity grid," period, so just leave it at that. At least, that's what I would want if I were betting.

(I do think it's entirely possible that fusion will be solidly profitable, especially with carbon pricing.)

https://longbets.org ?

That would be my favored platform!

I like what Tim Bray's doing with his time. https://longbets.org/863/

I'd bet a bitcoin against him.

I think this is a safe bet. Between Commonwealth Fusion's Arc/Sparc, or General Fusion's spinning glob of hot metal, or TAE systems, or any of the others, I think you have a better than average chance of settling this bet within 20 years.

ARC has a power density 40x worse than a LWR's primary reactor vessel.

General Fusion abandoned their first scheme because of at least three showstoppers (vaporization of the liquid metal wall, Richtmyer-Meshkov instability turning the implosion into jets of metal, and stochastic magnetic field lines in the spheromak causing unacceptable loss of energy via electrons to the metal). The new scheme has extremely serious engineering problems (the central pillar will be in a radiation/thermal environment orders of magnitude worse than the walls of ITER, and subject to extreme JxB forces). And they've never produced a neutron, as far as I know.

Rostoker et al. were told 20+ years ago that their p-11B concept couldn't work, for at least eight different reasons.

https://www.researchgate.net/publication/235032059_Comments_...

If I had to bet on any current private fusion effort I'd choose either Zap Energy or Helion.

Why is the power density of the ARC/SPARC reactor problematic?

Lower power density implies larger size, which implies higher cost. Since the parts outside the reactors themselves (the turbines, generators, heat sink, etc.) will be similar, this means a fusion power plant will cost more to build that a fission power plant.

The other problem is that size is also related to reliability. A fusion reactor will have many more parts than a fission reactor. It will also be much more complex, and operate at higher radiation and thermal stresses. This is particularly important because it is very difficult to repair something that is so radioactive that hands-on access is not possible.

> no government would be crazy enough to permit it to be built

Why? Nuclear fusion doesn't have the meltdown risk or waste problems of fission.

Fusion still has to deal with waste, just not high-level waste. Through the process of neutron activation all of the parts exposed to neutrons eventually become radioactive enough to be treated as low-level waste. In a reactor large enough to produce energy for the grid these parts could be very large (and expensive) to deal with (not to mention replace).

The main parts of a commercial tokamak would be huge. I read once that due to thermal stresses, replacement might be needed annually. I seem to recall that the STARFIRE project[1] estimated nearly 60 tons of low-grade radioactive waste per year of the operational lifetime.

[1] https://www.sciencedirect.com/science/article/abs/pii/002954...

Power plant waste:

60T/y for 1200 MWe = 50g / kWe·y = 1.6 mg/MJ

Coal energy density:

24 MJ/kg = 0.024 MJ/g -> 42 g/MJ

Not perfect, but depending on what the waste is, doesn't seem too bad.

Coal is absolutely the worst so it may not be a fair comparison. How would fusion compare to renewables like solar or wind?

https://en.wikipedia.org/wiki/Aneutronic_fusion

Yes, though the article consists almost entirely of reasons why aneutronic fusion is really hard ("the conditions required to harness aneutronic fusion are much more extreme than those required for deuterium-tritium fusion being investigated in ITER").

Note that the "Candidate fuels" section is not part of "Technical Challenges", but it might as well be. Helium-3, by far the easiest, is vanishingly rare. Deuterium would not really be aneutronic. Then further down is a list of worse and worse headaches.

The leading scenario for acquiring the most convenient fuel candidate is "mining it on the moon". (The alternative scenario being to scale up production of tritium by existing heavy-water reactors from the nuclear weapons program, which decays into helium-3... and defeats the point of researching extremely complex, clean, aneutronic fusion reactors)

I want to like aneutronic fusion, but it takes an objective that is several breakthroughs away and plays the game on nightmare mode.

Anything beyond D-3He or D-D is likely impossible. And any fuel with deuterium will still make enough neutrons to render the reactor inaccessible to hands-on maintenance. So there will still be a waste problem (as well as a huge reliability and maintenance problem). The reactor might not AS MUCH radioactivity, but much of the cost of dealing with it will scale with the mass of the contaminated material, not its activity. And fusion reactors will be very large. The cost of dealing with the activated material might end up higher than the cost of dealing with spent fission reactor fuel.

...is even further from breakeven than deuterium+tritium fusion.

There is no meltdown risk with modern fission reactor designs. But there is the waste problem.

If you follow the links my Op-Ed, you’ll find articles describing the radioactive waste and proliferation risks that will accompany any fusion reactor. Not as great as fission, but far from zero. And there is the problem of production and transportation of tritium, a very nasty substance.

A commercial fusion reactor would be fantastically expensive and complex, and require a huge infrastructure to support it.

"Does Fusion produce radioactive nuclear waste the same way fission does?

Nuclear fission power plants have the disadvantage of generating unstable nuclei; some of these are radioactive for millions of years. Fusion on the other hand does not create any long-lived radioactive nuclear waste.

Can fusion reactors be used to produce weapons?

No."

https://www.iaea.org/topics/energy/fusion/faqs

> Can fusion reactors be used to produce weapons?

> No.

That is a deeply misleading answer. While this would likely be easy to detect by international observers, it is not hard to enrich uranium in a fusion plant [0]. So fusion reactors, like fission reactors (though with less chance of clandestine operation) are still a nuclear weapon proliferation risk.

[0] https://web.mit.edu/fusion-fission/HybridsPubli/Fusion_Proli...

Couldn't you use regular fusor to generate neutrons to enrich uranium? Do you specifically need neutrons with the 14.1Mev energy produced by D-T fusion (which you can make in a regular fusor, if you have the tritium for it) or is there a path starting from lower energy levels? Or do fusors just not make enough neutrons for enrichment to be practical?

You probably could. However, the question wasn't whether fusion power plants are a bigger risk for nuclear weapons proliferation than other technologies, it was simply if they can be used for nuclear weapon development, to which the answer is yes, but not as easily as you can with fission power plants.

Right, as other commenters have pointed out, this is low-level radioactive waste. It, along with tritium, is great for dirty bombs and catnip to terrorists.

A dirty bomb is a weapon. They are talking about “atom bombs”.

> is great for dirty bombs and catnip to terrorists.

This is another variant of “think of the children”. How many terrorists have built these dirty bombs?

I saw it in at least two movies.

They haven’t been able to yet, because we don’t have any fusion reactors out there.

Is the risk any worse than a terrorist making a bomb that spreads a bunch of non-radioactive heavy metals, or any other toxic substance? What about when compared to the general damage caused by mining and burning coal?

Not necessarily, if I take “any other” literally.

Tritium’s low molecular weight means that a bomb can disperse it over a large area. It has a half-life of 12.5 years and its beta radiation is known to be carcinogenic from animal studies. An inhaled, microscopic bit of tritium will be irradiating your lung tissue for many years, although the actual effects of this are not known. However, it is very strictly controlled, and you need all kinds of special licences and certifications to use it in your laboratory, for these reasons.

So the lure for the terrorist is just that: it’s good for terror, because of the psychological effect.

“What about when compared to the general damage caused by mining and burning coal?”

If the choice were between coal and fusion, for me there would be no contest. We would have to put everything into developing fusion power. Fortunately, there are alternatives that are better than either and are already working.

> Fortunately, there are alternatives that are better than either and are already working.

Agreed, I would love to see more spending for things like, CSP molten salt research and storage systems in the public domain. That way, even if countries like the US are still captive by certain industries to not adapt it at scale, countries like Chile with +100MW systems with 17h of molten salt storage that are grid connected now, can benefit.

Dirty bombs are actually terribly ineffective weapons. The radiation would be unlikely to harm anyone who wasn't close enough to be killed by the conventional explosives unless they spent a considerable amount of time in the irradiated area afterwards without any sort of protection. While the cleanup operation could be expensive, the whole affair would be more an inconvenience than anything else. On the plus side though, now you can detect the terrorists' essentially conventional explosive which would otherwise be quite concealable with radiation detectors.

Also tritium is essentially harmless. It is an incredibly weak beta emitter - the electrons it emits won't make it through the upper layers of dead skin if it's outside of your body. It has an extremely short residency period in the body if it is ingested (a benefit of being chemically identical to hydrogen). It also will dissipate in an area rapidly - it rises quickly and even if it is in an enclosed space it will pass straight through the walls. Also it's worth noting that a fusion plant like ITER has less than a gram of tritium inside of it at any given time.

You’re correct about the skin penetration, but the risk with tritium is in inhalation. Experiments with mice demonstrate carcinogenesis. The increase in cancer risk from inhaled tritium in humans is unknown, but the substance is considered dangerous enough that it’s a pain in the ass to get the certifications to use it in your laboratory. It definitely should not be considered harmless.

I worked with Stephen Bodner on the fusion program mentioned in the fine article. We did our experiments with deuterium. The reason we did not use DT, which would have been better for the experiments, is because nobody wanted to (1) go through the hassle of getting the lab certified to handle tritium' (2) get anywhere near the stuff. It is considered very hazardous.

Tritium is a pain in the ass to get certifications for because it is so difficult to contain. Even in an airtight setup, it will leak. If you spend a substantial amount of time in lab with a tritium leak, and are inhaling the stuff over months or years, yes it's dangerous, but hydrogen doesn't remain in your body long enough for a single brief exposure to do anything.

Mercury vapor is very hazardous, that doesn't mean a mercury bomb is an effective weapon.

Your points are solid; I accept that this material would not be very effective as a weapon, except maybe in a confined space. But it’s still something whose possession we want to control, so handling and transporting it adds to the cost and complexity of operating a commercial fusion facility.

I have a watch with lume powered by phosphor-coated tritium vials. I’d better keep it safe from terrorists trying to build dirty bombs.

The problem with this statement is that you are assuming tritium would be “great for dirty bombs and catnip for terrorists”. But then you go on to say that it hasn't happened yet other than in films because there are no fusion reactors yet. This is, in other words, speculation.

The problem of fission isn't meltdown risk or waste (or fuel availability), the problem of fission is capital cost. The capital cost of a fusion power plant is likely to be much higher than that of a fission power plant of equal capacity.

> Even if we got fantastically lucky and were able to build a practical (magnetic or inertial) reactor in 50 years, by that time improvements in energy storage and transmission technologies will have allowed renewable energy to dominate, and no government would be crazy enough to permit it to be built.

Not so sure about that. Vast solar and wind farms are eyesores and are not environmentally benign.

You're right. they’re not. But no form of electricity production at the scale we need it, and the even more massive scale in the future, is environmentally benign. The challenge is to find the best way to leave chemical combustion behind, and fast. Notice the new interest in the old devil, nuclear fission, among various green groups.

That's mostly interest among astroturfers, not actual green groups. There was a bit of interest among some genuine greens about a decade ago, but that evaporated as solar and wind continued to decline in cost and the nuclear renaissance flamed out.

I think they're aesthetically pleasing, personally. Both solar and wind farms.

Would be nice to note the thing you linked to was written by yourself, for full disclosure.

Yeah. that was a big secret.

> and no government would be crazy enough to permit it to be built

I can imagine China building one simply for the national prestige. "China built the world's first commercial nuclear fusion power station". The Chinese government wants to prove itself the equal of other major world powers (especially the US) and being the first country to have commercial nuclear fusion would be a good way of sending that message. Even if it is more expensive and less safe than renewable energy.

And then the US government would build one to "counter the nuclear fusion gap with China" and "ensure American supremacy in nuclear fusion technology".

That said, this isn't going to be technically feasible for a few more decades (at least), and we don't know what the geopolitical situation will be like by then. Maybe China-US competition will still be as strong, even stronger, then as now. Maybe it will be in the past and the world will have moved on to something else. Who knows.

Now that you said it, a holhraum does bear a resemblance to a Teller-Ulam device.

Is NIF even a "fake fusion energy program"? TFA specifically mentions their goal of simulating fusion detonations in nuclear weapons.

Yeah, but they regularly send out press releases gushing about the energy application. This helps with Congressional funding.

Here is the head of the NNSA, the funding agency for the NIF, quoted in the fine article:

“It also offers potential new avenues of research into alternative energy sources that could aid economic development and help fight climate change”

That’s some finely tuned BS right there.

> mean that renewables will soon be able to supply all of our energy needs

pure propaganda. Otherwise why all the panic about global warming. If true we'll have no problem hitting all the targets to avoid the a global warming catastrophe.

> Otherwise why all the panic about global warming

Because it doesn't just need to be feasible, it also has to be actually implemented. That costs a lot, and comes with a shit ton of friction. The fossil economy is a massive beast to try to turn around, and it would be so even if aliens landed and gave us the schematics to a perfectly working dream fusion reactor right now. That's why there is a "panic".

I agree, except in 50 years the productivity of the world will be so high that building this, even if it costs 500B in today's dollars, someone will pay.

Would they be useful in space?

No DT reactor will be useful in space. The size of the reactor will dwarf that of a fission reactor of equal output.

What about SPARC and ARC?

Building enough ARC reactors to supply the world primary energy demand require beryllium 100x more than the estimated global resource of that element. A single ARC reactor uses 40% of the current world annual production of Be.

"Renewable" maximalists are such bores.

On the contrary, it will be so much energy it will be like a new agrarian revolution. No society outside the be able to resist it.

Having toured NIF a few times and worked in one of the buildings adjacent to it a few summers ago, I will say the energy stuff always seemed more like a way to get funding. The main use and aim for NIF is and always has been to re-create some of the conditions inside nuclear weapons and similar fusion-based reactions.

The whole NIF building has the ability to switch modes between classified and unclassified. They wouldn't have gone through the trouble of making this a toggleable feature on the building if they weren't actively using it for both.

> The whole NIF building has the ability to switch modes between classified and unclassified.

Interesting, can you explain this more? What gets hidden?

I don't know the specifics but I imagine most of it is waving a magic wand and saying poof now this room is classified. But there are logistics that go with that, certain door technologies that have to be in place, probably some complex security procedure for "switching" between modes, (i.e. I would think they need to clear the building of uncleared personnel and be 100% sure there isn't someone hiding in a bathroom somewhere) etc etc, and it's enough of a pain that most buildings are either one or the other all the time. The ability to switch on the fly for a large facility like that is super rare and indicative of there being a real need for switching.

All I know for sure is on the tour they mention they can switch the whole building to be unclassified or classified and during the tour it is in unclassified mode.

I imagine a big chunk of switching to classified is shooing the un-cleared visitors.

Likewise for going from classified mode to unclassified mode they would have to sweep the whole facility for sensitive material

I'd imagine waste disposal processes and cleaning staff to be major headlines in the switching procedures.

Cleaning staff usually have TS clearance at places like this oddly enough, and are usually on a pension and work there for life.

I've heard that, at an air force base where civilians work, there's a blue light that turns on both on the door and inside the room, when that room is in "classified" mode, and they are only allowed to do classified work when the light is on and the door closed.

To be clear though, I don't think anything about NIF's actual design is classified. Maybe the parameters they use on some tests and the angles on some of the lenses and/or target design/composition are, but the actual setup is all publicly documented AFAIK.

The aliens have to go to their cryopods :).

>> There's also a firing rate issue. Even if the system produced net power, significant production would require many shots per second. Currently, the laser flash lamps are expendable and it takes on the order of a day (and lots of money) to prep for each shot.

Oh, but then there's this part:

>> Further experiments will require the manufacture of additional fuel capsules and hohlraums. These may not be ready until at least October, Herrmann says. The nanocrystalline diamond-coated capsule that was imploded in this month’s event took six months to grow at General Atomics, which has long worked with LLNL on fabricating capsules. The spheres have to be polished and the core’s interior etched with tools inserted through a 2-micron-diameter hole drilled into it. The tritium–deuterium mixture is injected through a tiny fill tube just prior to the shot.

That's actually uplifting to read! Even if we don't end up getting fusion power out of this, it's got to be helping fund improvements in nano-manufacturing!

Well, it is aweseom tech. But probably nothing I would bet we can rely on, soon.

for the love of god, someone please rename these "diluthium crystals"!

> There's also a firing rate issue ...

The NIF goal was ignition, not continuous power production. The original spec was one shot every four hours. Achieving one shot per day is close.

The nuclear stockpile bit is kind of true, although it's sort of true, HEDP systems are the only way in a controlled setting to create nuclear level conditions without setting off a nuke. That said, NIF at least from the energy perspective just like ITER was just to push the research forward than it was to produce break-even fusion in 10 years. If you really want that you'll need gobs of money, probably even beyond the level of things like the LHC. The reason we don't have fusion in either field (MCF or ICF) is because we don't fund it to that level.

EDIT: on funding, this[0] image shows what is neccessary and the level we actually funded. It's been around for a while but it may prove informative for the uninitiated.

[0]https://i.imgur.com/3vYLQmm.png

I get the point the graph’s authors are making, but I wonder how those projections (made in the 70s) would hold up today, knowing what we know about the engineering challenges for each fusion approach.

In other words, I’d love to see a 2021 recreation of that graph.

> the LIFE proposal, which would use fusion neutrons to burn fission fuel in a blanket around the fusion chamber.

This is crazy. If you are going to have fission and fission products, you might as well just build a fission reactor. It would be vastly simpler, smaller, and cheaper.

http://web.mit.edu/fusion-fission/WorkshopTalks/skepticsvg.p...

My money is on stellarators. Just saw Wendelstein in the newsfeed here: https://news.ycombinator.com/item?id=28211413

Stellarators face many of the same likely showstoppers as tokamaks. Power density, materials, maintainability, complexity, cost.

In the utmost respect, you sound like Lazlo from the movie Real Geniuses.

https://www.youtube.com/watch?v=HoT-h0S1gkE

> Herrmann noted that in previous experiments, neutrons exiting the capsule on one side of the implosion arrived a few picoseconds earlier than did those flying off the opposite way

Let’s all just take a step back here and marvel at this statement. We (science-humans) are capable of building a machine that can detect and quantify picosecond level variances in neutrons traveling in an enclosure. We can do amazing things.

Side note - the lab is just down the road from me, I’m proud of my fellow Livermorons, and continue to hope they keep all those megajoules contained.

For context, in wired chip-to-chip communication electronics, femtosecond variations are (statistically) measurable. Picoseconds are rather pedestrian. A 56 Gbaud signal has a single-symbol duration of about 18 picoseconds and perturbations on the order of 1 picosecond are rather large 5.6%.

Not to downplay the achievement of the article or the innovation in fusion physics and engineering in general, just a bit of context for the timescales.

For further context, the fastest oscilioscopes commercially available (Keysight UXR) samples at 256G with 20fs (rms) of jitter. Modern coherent optics runs at over 100GBaud, a picosecond is 1/10th of a symbol period.

MSRP of $1.3 Million US dollars

https://www.eevblog.com/forum/testgear/something-amazing!-ke...

AKA roughly one Brooklyn apartment.

Used a similar scope during my grad school tenure for measuring 200GS/s ADCs. RF electronics is a wonderful field.

In a 5nm semiconductor chip a standard cell inverter (like combinational AND / OR gates) can switch in 5 picoseconds. These things are characterized with at least 2 more significant digits so we feel we know how they respond at the 10's of femtosecond level of precision.

A nice rule of thumb for these kind of timescales (courtesy of a lecture by Grace Hopper) is to consider the speed of light: 1 nanosecond at the speed of light is about 1 foot (300 mm). A picosecond is then 0.3 mm.

Which is also a method to shift light pulses by the shortest of durations! Insert an optical delay line into the setup and by varying the path length, you can delay a light pulse by a tiny amount of time, e.g. for a pump-probe experiment (a pump-probe experiment works like this: first pulse does something to the system ("pump"), second pulse comes a short time later and reads out ("probes") the state of the system at that time. Changing the time delay gives an idea of the dynamics).

Here is a drawing of an optical delay line: https://www.thorlabs.com/images/TabImages/Delay_Line_Kit_D1-...

The part labelled "V-Block" can move along the "translation stage" which changes the length of the optical path by twice this amount. Use the speed of light to calculate which delay the pulse incurred over the distance. You can now send pulse after pulse through your setup while changing the delay by tiny amounts to see how things (e.g. chemical processes) happen on these time scales.

Relevant video for those who haven’t seen the lecture:

https://www.youtube.com/watch?v=9eyFDBPk4Yw

For those questioning the “Livermorons”: I can’t speak directly to that but can say that Naval Aviation uses a similar term for those who elect to stay at NAS Lemoore: “Leemorons”. It’s not a perjorative; the people I’ve talked to use the term affectionately.

In a large enough community, these two (perjorative and affectionate) are not mutually exclusive. c.f. Yankee Doodle, etc

And it's important to note that these developments in sensor technologies can be carried forward to future experiments even if the NIF is ultimately incapable of being improved much further. The quest for fusion is not simply achieved or failed, working on tough problems like this leads to technological progress at every step along the way.

It still amazing how much of the periodic table we owe to this place. https://www.llnl.gov/news/tags/periodic-table

A considerable number of post-1960 Nobel prizes in physics and chemistry, as well as a fair bit of the medicine ones, come from sensor-related discoveries.

Either they're directly applicable to sensing phenomena, or they form a substantial part of a sensor technology.

Contrast with the pre-1960 period which was dominated by discovery of fundamental particals, elements, and laws or principles.

Disclaimers: this is based on a somewhat casual review of awards, and even if my own assessment is reliable, the Nobel award process itself has numerous opportunities for bias and trend-based behaviours.

While everyone is focusing on the picosend part of this, I’m more impressed by the neutron detection. Electrically charged particles sound much easier to detect, let alone with any kind of temporal precision

It reminds me of the gravity wave detectors. It boggles my mind that we are able to build machines that can measure such staggeringly tiny effects.

Lol.. livermorons

Livermorons? Really?

It's the correct demonym for people from Livermore and also a bit funny. One of the breweries in the area even named a drink after it.

Maybe they have a sense of humor about themselves.

you need to with the heat there in the summer

> I’m proud of my fellow...

The part after that, was it a typo? :)

Nope, looks legit: https://www.google.com/search?q=livermorons+site:www.reddit....

To be honest, Livermorans sounds a bit more natural to me than Livermorons. And it does appear that some people from Livermore call themselves Livermorans, like "Cheryl is a native Livermoran" [1].

[1] https://www.lvwine.org/blog/winemakers-talk-harvest-favorite...

I think you miss the point: it’s a friendly in-joke that the people who stay in that area are “morons”.

You see this in places where there isn’t much to keep you there except your profession, typically government. I’m aware of Livermore and Lemoore, but I’m sure there are others.

And to completely explain the joke to death, it's also ironic to self-deprecatingly call yourselves "morons" when you work at a scientific laboratory.

No, this has nothing to do with those of us that choose to live here being stuck because of our professions, what the heck gave you that idea?

Everyone I know who lives here LOVES Livermore. It’s decent commute distance to most places in the Bay Area, is surrounded by beautiful hills, 40+ wineries, an award winning downtown, and the friendliest people of any biggish California city I’ve lived in.

It’s a joke, but related to the awkward sounding and looking term Livermoran.

There is a LOT more keeping the 100k of us in Livermore than our professions.

My apologies; I grew up half and half between Marin and Fresno and that’s what I recall for both.

If I mistook where the term up north came from then I do apologize.

Edit: I think an issue was with my explanation. The people I know in both areas actually love it; people outside the area think they are stupid for living there. Therefore there is some appropriation of the pejorative.

Once again, if that’s mistaken in reference to Livermore then I apologize.

We can do so much and yet so little. All of this progress may amount to nothing if we cannot overcome our internal obstacles to our collective survival.

Awaiting the downvotes but it's true.

lol yeah y'all aren't in denial, sure....

Reading the info so far...I would advise a frugal dose of moderate optimist toned down with a spice of healthy scepticism:

"The lab hasn’t yet reproduced this month’s results, and Herrmann cautioned that doing so might not be straightforward. “We don’t know what variability will be in successive shots. It’s a nonlinear process where alpha heating heats up the fusion fuel and creates more fusion, which creates more heat.” Herrmann says the 3.5 MeV alpha particles, which remain in the plasma, produced 20% of the fusion yield, with 14 MeV neutrons accounting for most of the energy."

"The lab is still analyzing the results from the shot. It’s not yet known which or what combination of advances to the targets, laser pulse lengths, or other variables led to the leap in performance. Some of the instruments were saturated by the unexpected yield of the reaction. A few that are used in the target chamber for other, non-ignition experiments will need repair."

"Herrmann acknowledged that the announcement deviates from the standard practice of peer-reviewed publication. But the results, he says, were leaking, “so we wanted to put it out so people could discuss the facts.” "

This is fantastic. And I agree with the fellow mentioning direct drive as better. If you can get the same results using direct drive, you’ll have a sizable energy gain above what the input energy was, perhaps enough to drive a (multiple stage) heat engine and produce net electricity.

Anyway, I also want to point out that laser inertial confinement fusion bears a not-coincidental (some of the same codes and plasma physics techniques developed for laser fusion were used by Lawrence Livermore and others to develop EUV) resemblance to the extreme UV light sources sold by ASML and used for the highest end computer chips today. Compare the LIFE fusion reactor concept (based on an evolution of the NIF) with the EUV light source of droplets of tin being hit with a pulsed laser:

https://en.wikipedia.org/wiki/Laser_Inertial_Fusion_Energy

EUV light source: https://youtu.be/IattxYrc9Go

(The Hohlrahm of the National Ignition Facility, surrounding the tritium deuterium fuel pellet, is acting like the tin droplet of the EUV light source, converting longer wavelength pulsed laser light to (near) X-Rays.)

NIF isn't supposed to achieve net power generation. It's a defense research facility which is intended to test nuclear weapons technology without violating weapons testing bans.

That is not quite correct. Yes, its primary purpose is “stockpile management,” but it’s not exclusively that. It was ALSO sold as a facility to study fusion power generation, hence this announcement.

LIFE was a proposed follow-on project to NIF that would be focused on power generation demonstration (high repetition rates, etc). It never went anywhere and work on it effectively stopped around 2013 or so.

But the comment you’re replying to is exactly correct. NIF is not LIFE. Ignition is far from net power generation, by a few orders of magnitude.

I picked up on that angle as well.

“Ignition” isn’t about generating electricity. It’s about making fusion bombs which don’t emit neutrons or other radiation (from a fission trigger) while the device is in storage.

So, not primarily a power generation design like a tokamak would be.

Here is your daily bit of useless knowledge: the energy released by fusion from this single, microscopic target is roughly the caloric value of a McDonald's cheeseburger (~300kCal).

A cheeseburger's worth of energy actually extracted from something the size of a spec of dust. It's a good way to make numbers real.

Alternatively it's about the amount of energy to raise 4 L of water from room temperature to boiling.

For some reason I'm surprised a cheese burger has enough energy to boil my kettle multiple times.

A cheeseburger has enough energy to power you for most of a day. Possibly doing a lot of heavy lifting, and continuously running the largest and most sophisticated neural network hardware on the planet.

That'd be a very large cheeseburger. I burn more calories in a typical 50 min workout (weights, not cardio, it's easier with cardio.)

Looking up burgers I've eaten recently:

* A bacon cheeseburger from Five Guys is 1060 kcal

* A double-double from In-N-Out is 670 kcal, and that's before you make it animal style

But yeah, not a McDonald's cheeseburger. I'm somewhat offended that they're allowed to call those "burgers".

A 300 kcal cheeseburger? I don’t think so. The baseline metabolic rate of an adult is ~1700 kcal/day.

The definition of a dietary calorie (kilo-calorie) is the amount of energy needed to raise the temperature of 1kg of water by 1 degree Celcius.

So the kettle math is actually quite straightforwards.

Yeah, I mean, it's just generally astounding that the food I eat is enough to power even a sedentary lifestyle, let alone one with a bunch of running and other exercise.

Since any practical reactor will use steam turbines to translate heat to useable energy that last one is actually a good way to think of it.

Not steam turbines, closed-cycle gas turbines.

Yes, the energy equivalent of McDonald's Cheeseburger dietary calories.

From a blob of matter about 100 microns across and over a timespan of less than a nanosecond.

Obviously, once (or IF) they get this thing to be repeatable and then scalable, it will become a big deal.

For intuition about what it's like to release the energy instantly, it's also ~ one hand grenade.

I like how they didn't expect it:

The US gives about the same amount of money to the National Ignition Facility as to the ITER project, roughly half a billion dollars per year (a bit more for NIF, a bit less for ITER). Of course, the main objective of the NIF is to assist in the stewardship of the nuclear stockpile, not to seek economic nuclear fusion. Still, it's great that they achieved this milestone. Congrats to all involved. And good luck in the future.

"the main objective of the NIF is to assist in the stewardship of the nuclear stockpile"

I suspect that's always been a funding fig leaf. The nuclear stockpile stewardship claim is highly dubious.

Not that I mind. There are worse things diverted DOD money has been squandered on.

Fusion using lasers is an off-shoot of H-Bomb development, and advances by John Nuckolls from early laser-based fusion research in the 1960s(!) were fed back into H-Bomb research.

These fields are surprisingly related. For details, see Alex Wellerstein's book "Restricted Data", chapter 7.

MCF faces a few engineering hurdles. ICF faces several times more. Investing in a facility on the scale of NIF for ICF doesn't make much sense if the goal is economic fusion power on the grid. There are much lower hanging fruits where that money could be spent: such as on new MCF machines or a wider and shallower mix of ICF machines. Ask non-US fusion researchers how they feel about ICF if you want a proper outside perspective.

Magnetic confinement fusion like ITER is no less of a boondoggle. Maybe even more so because the progress is intentionally slow in spite of not having a dual-role for “stockpile stewardship.” ITER is being funded not just by the US but by many countries, started development in 1985, detailed design in 2001, and construction in 2013, but it’s not even PLANNED to get full fusion until 2035. 2035!

Plus, it won’t even generate electricity at all. That’s planned for the DEMO reactor that won’t start operation until 2051 at earliest. It is depressingly slow if you think one of the main reasons we should be developing alternative energy sources is to address climate change. It’s so bad as to qualify as a waste and maybe even a negative investment as it’s pulling a bunch of researchers toward a project that literally has no hope of being relevant to fighting climate change (as its first possible kilowatt-hour of electricity won’t start until 30 years from now, well after we’ve exhausted our carbon budget for 2 degrees C of warming).

I also understand that fusion in general is unlikely to be an economically-viable energy source anyway, since the reactor and any surrounding material will be relatively quickly (~few years) be made brittle by the neutron bombardment, while also becoming radioactive - meaning any fusion plant will have to be carefully and constantly torn down and rebuilt, and materials from the old plant securely stored for large amounts of time (not as large as fission waste, but still in the order of decades or centuries). There are other concerns with hydrogen escape etc, but this one seems completely fundamental.

Some methods of fusion solve this in varying ways, with liquid metal blankets, etc, or using non-neutron is fusion fuels. But that’s missing the point. There’s no path to these more viable methods of economically producing power that don’t run through the path of generating more fusion energy than it absorbs, so we start with the easier fuels first to prove we can do sustained fusion before worrying too much about neutron embrittlement.

Even if we had unobtainium that was free of radiation degradation, fusion reactors would still be unlikely to be competitive -- they're just too large and complex, and hence expensive.

The problem is that ITER is funded as a science project, and the researchers want to get as much research as possible.

So they are going to spend a lot of time studying plasma before they irradiate the vessel with fusion byproducts and it's no longer safe to take apart (for example, to add new sensors).

It's the only facility of this size so the research program is completely sequential.

We could have fusion, we just need to spend $20 billion a year for 10 years. Not $1 billion a year for 200 years.

The first job of ITER is to show that disruptions can be controlled. This is absolutely necessary, and requires access to the machine to repair it when disruptions occur. So this had better be done without tritium (or possibly even deuterium). And if they can't do it, they will never be allowed to operate the machine with tritium.

They could spend the same amount per year and get results in 5-10 years if it were being run competently.

There’s no point in babying a facility if it means taking decades too long to get useful results!

What about "magnetic mirrors"? https://www.llnl.gov/archives/1980s/mirror-fusion-test-facil...

I recall hearing a scientist from the lab say that was the way to go and they mothballed it because they wanted to focus on weapons research.

Mirrors are interesting. They hit very high performance metrics in a small budget. However they have this pesky issue of requiring an electrostatic field. Conduction losses are a killer, scale up in nasty ways, and ablate material quickly.

In terms of inexpensive neutron sources: they're perhaps some of the best we have.

I don't buy this view. You can see from the quotes these physicists don't really understand why they got this result. We don't actually know enough about what is happening with ICF of MCF or any other xF to rule out approaches. And why should I need to seek foreign opinions to confirm your view? NIF detractors grow on trees in the US. You never, ever get a story about NIF without one chiming in.

This isn't diverted and it isn't DOD money. It's DOE money. If it's a figleaf then what's it covering?

Department of Energy wasn't made when the grid came online; it was made when nuclear bombs were invented. The DoE isn't the department of electrical power security; it is the department of nuclear weapons security. The fusion energy research has been painfully underfunded because there isn't a political motivation to solve the problem. How does solving the energy crisis benefit the countries that benefit the most from it? Put another way: when you are on top of the hill, why would you flatten the landscape?

This is amazing! But then...

“It gives the US a lab capability to study burning plasmas and high-energy physics relevant for [nuclear weapons] stewardship,”

Are you freaking kidding me? How about solving the energy crisis required to reverse climate change? Nope. More bombs :(

It’s not more bombs so much as maintaining our existing nuclear deterrent without actually testing warheads by blowing them up, something that, thankfully, is behind us. Warheads deteriorate over time; you can’t just keep them on the shelf and claim that they will still work if used. And our adversaries know this.

Don't get too alarmed by this. It's how a good portion scientific progress in America has always worked (especially if the project needs military scale funding). The tech eventually makes it out to civilian space.

For when every home in America has an aging nuclear warhead?

AND to solve the provisioning of fissile-capable material in third world country by having tech that can work on fissiON-capable material, ie non-radioactive. Which makes carrying those to Africa a progress rather than war material. Which means we might need less bombs.

I'm pleased to say I finally have funds to start construction on my new theoretical fusion reactor.

In a loose way it is similar to the inertial confinement at LLNL, but instead of pulsing 3 to 4 times per day, I'll be creating billions of implosions per second. This is possible because of the way I recycle energy that is otherwise lost, not needing a hohlraum(heating only the Deuterium), and ramping up the implosion energy harmonically instead of brute forcing it with a single large punch.

I have more information at www.DDproFusion.com

I'm honestly not sure why there seems to be so much interest in fusion these days. Wind and solar seem to offer a limitless, carbon-free energy supply with relatively cheap, well understood technology that is already price competitive with coal and gas. By contrast fusion seems super expensive and technologically very complex - even fission plants take 10+ years to bring on line. Does fusion offer some advantage over wind + solar that I'm missing?

My armchair/spectator interest in fusion comes from the idea of significantly increasing the energy available per capita, without increasing carbon footprint. Traditional renewables might meet our current energy needs eventually. Fusion could let everyone on the planet enjoy the same, or even a significantly increased, lifestyle. As the saying used to be long before I was born, "energy too cheap to meter" (though obviously it still would be metered).

With enough surplus energy, you could run entire reactors just for carbon sequestration, or nation-scale desalination, or climate engineering, or what have you.

A joke some friends of mine who study fusion make to this kind of comment; wind and solar are fusion powered.

In a simpler way of looking at it, (1) what is the source of the energy of solar/wind? (2) how much land and materials are required to linearly increase power production?

There is a finite amount of space and resources on the planet to continue to scale power production with humanities consumption.

Fusion, preferably MCF/tokamaks in the style of smaller sized ones like SPARC @ MIT and less like ITER (behemoths that take decades to build and maintain) offer two things (1) the fuel is comprised of the most common elements in the universe, (2) power per square foot is much greater than solar or wind... And bonus (3) once developed it should in theory require less material per watt generated. And less materials mean less processing and fabrication which in turn reduces the environmental impact on the planet.

Excuse my lack of knowledge on the subject, but from a few comments/articles it seemed that although Tritium can be recuperated through contact of the charged neutrons with lithium "blankets" surrounding the enclosure, it is still incredibly hard to achieve self-sustainability, to the point where we might need fission reactors just to produce that isotope. Am I missing something or isn't Tritium not so readily available?

The margins for 'breeding' tritium from lithium are slim, yes. I don't think fission reactors can help in the long term, but right now that is how we get tritium for our experiments.

How about advancing the frontiers of science? That alone is worth it, it is not?

You seem to want to halt all further research into alternative energy and settle with the current state of our solar/wind capabilities, which is strange.

We can do both.

Fusion is a poor kind of science. It's very inward focused, answering questions that are relevant to fusion but not much else. As pure science, it would not merit the $$$ being focused on it.

As stronglikedan said, spaceflight propulsion/institutional inertia. (Stationary space facilities will use solar, just like on Earth. Space transport, unlike Earth transport, will be an awful combo of slow and expensive. Space stations will need to be simple. One type of computer. One type of microcontroller board. Maybe three sizes of screw. Solar panels are simple, identical, and interchangeable. And not radioactive! (Fun fact: every bolt on the outside of the ISS uses the exact same head size: 7/16" hex))

Seasonal variation with solar is a bit of a bummer. If we need to fully electrify everything, (Transport and heating) then winter will be a problem. Either we massively overprovision solar in order to still have heat on the shortest day of the year, or we run thousand mile cross-country transmission lines and enormous battery banks.

Even so, the economics are such that heavy industry might become a seasonal job. Right now we run aluminum smelters 24/7 because baseload power is fairly consistent, but if solar power is free in July but dear in January you might see multi-month shutdowns. This gives headaches to central planners, and makes them inclined to pour billions into fusion if it can preserve some of the status quo.

> Even so, the economics are such that heavy industry might become a seasonal job.

Or it will move to locations where seasonality is not as important.

Something of a question mark of how long the tropics are going to remain habitable. We're still on the "business as usual" emissions curve, with no signs of meaningfully changing that. That puts us 5C higher by the century, and will keep going up after that.

Many equatorial regions will either be too hot for human life, (https://advances.sciencemag.org/content/6/19/eaaw1838) or be active combat zones as a result of refugees escaping heat. Some cities in India are now routinely hitting 50C during the summer, and we've only had 1C of warming.

If the tropics threaten to become uninhabitable countries like India will go ahead with direct climate engineering by dispersing fine particles in the stratosphere to reflect sunlight. This need not be at all expensive, even for them. No credible threat from other countries would deter them, as they'd face mass destruction otherwise.

I think wind and solar are plan A at this point, if for no other reason than they're hard to beat on cost. Battery storage is still expensive, though.

If fusion works out, it could be used to make up the difference when the sun isn't shining and the wind isn't blowing (though if we eventually get high-capacity transcontinental HVDC lines to buy and sell power from practically anywhere or batteries become really cheap, that becomes less of a concern).

Fusion would also would require far less land, and some people object to having a landscape covered in windmills and solar panels.

Fusion might be useful in places where renewables are less practical, like on ships. Naval vessels might conceivably replace fission reactors with fusion. If they're safe and relatively simple to run, you might even see them on civilian ships. Or you could have fusion reactors in remote places, like floating on a buoy in the middle of the ocean, to serve as a charging station for battery-powered ships.

Fusion may be useful for establishing a human foothold outside of Earth. For instance, methane production on Mars (for rocket fuel) will require enormous amounts of energy, which could be supplied by a fusion reactor. (A fission reactor would perhaps work just as well, but there are legitimate reasons why people get nervous about launching hazardous materials into space on a rocket that might blow up before it achieves escape velocity.)

We might also begin engaging in projects that require enormous amounts of energy. For instance, if certain CO2 absorption strategies are energy-intensive, and we can't practically generate that amount of energy from renewables.

At this point, we really don't know if it'll work much less what the practical limitations will be, so perhaps the best we can do is say "if a fusion reactor can produce X amount of energy and weighs Y tons and requires such-and-such amount of cooling and requires an overhaul once every N months at a cost of D dollars, we might want to use it in these applications".

Hydrogen made from renewables and burning in combined cycle turbines would likely be far cheaper than fusion.

Fusion would be horrible for ships. Ships are volume constrained, and fusion reactors are very large.

Land constraints are not globally significant at current energy demand. The world is constantly hit by 100,000 TW of sunlight; average global primary energy demand is about 18 TW.

In space, DT fusion reactors will be inferior to fission reactors, which will be much smaller and lighter for a given power output (and also much simpler).

It's very difficult now to make a case for fusion. In the past, the case was something like "fission will be a big winner, but then we'll have trouble with uranium availability and safety and waste, and fusion, while slightly more expensive than fission, will still be cheap and solve these problems." But that's not how it turned out -- fission failed because it was too expensive, and fusion being even more expensive than fission makes it a nonstarter.

Fusion doesn't have to be big. ITER is huge because it was the smallest it could possibly be given the superconducting magnetic coils that were available at the time it was being designed, but we have much better high temperature superconductors now. (This is the basis of MIT's SPARC and ARC projects.)

Currently, we don't have any practical working fusion reactors, so it's hard to say what the attributes of such a reactor would be. We have some designs that according to our understanding of physics might work, but the designs are likely to go through many iterations before we have something that can be mass-produced and deployed in volume. Rebco tape probably isn't the best high-temperature superconductor that will ever be discovered. And so on.

> Fusion doesn't have to be big.

It does, actually, with neutron producing fuels. The problem is that volumetric power density is limited by the areal power density limit on the wall of the reactor, and by the need of a sufficiently thick blanket to absorb neutrons. The inferiority vs. fission is roughly (thickness of fusion reactor blanket)/(diameter of fission reactor fuel rod). This is independent of any details of plasma confinement.

Something like ARC has much higher power density than ITER, but it's still very inferior to fission reactor. ITER's power density is just so incredibly bad.

Does it matter? Fusion doesn't have the same power per unit volume as fission in order to be usable on a ship, it just has to be good enough to be usable in that application: i.e. able to produce maybe in the neighborhood of a couple hundred kilowatts continuously without being overly bulky or expensive.

There might be limits though on how small the reactor can be made. ARC is apparently meant to produce hundreds of megawatts, which sounds like it maybe be two or three orders of magnitude more powerful than what even a large container ship would use for propulsion. SPARC is a physically smaller reactor, but not intended for continuous or long-term use. If the basic design works out, probably the first real-world designs will be optimized for utility power generation, where size doesn't really matter except to the extent that "bigger" tends to mean "more expensive". Minimum-size designs might take longer to show up.

If I understand correctly, the ARC design uses FLiBe to capture the energy from the neutrons. It takes up the space between the vacuum chamber and the outer housing. The FliBe heats up, and is pumped out into heat exchangers that produce steam to run a turbine. At some point there's a practical limit to the amount of heat that can be removed that way, but it seems like a low-output reactor should be easier rather than harder to make from that standpoint.

Clarification: I wasn't thinking clearly in terms of unit conversion; 100kw is about as much power as a small car.

This is an ~80 megawatt ship engine. https://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA9...

"Hundreds of megawatts" may be oversized for ship application, but maybe more like 2x to 10x oversized rather than 100x to 1000x. Or maybe not. Apparently they use some pretty powerful reactors in aircraft carriers: https://en.wikipedia.org/wiki/A4W_reactor

Solar+wind(+energy storage) needs a lot more materials and land to produce the same amount of energy.

So the footprint of fusion would be a lot smaller.

Also for the same reason deployment would be faster allowing a faster phase out of fossil fuels.

Solar and wind can be deployed very quickly, and can be deployed today. Fusion will be available somewhere between "decades from now" and "never".

A tired response, and a false choice at that.

Deploying solar and wind does not preclude continued research and development into alternative energy production methods.

It's a direct rebuttal to the false statement "Also for the same reason deployment would be faster allowing a faster phase out of fossil fuels."

Fossil fuels had better be phased out soon, and fusion cannot be available in that time.

IMO, the prospects of fusion reaching a practical state are so remote that even the current level of funding on it is difficult to justify. There are fundamental engineering constraints that render it inferior to fission -- and fission is now going extinct itself, being too expensive.

Fusion (and fission, if we are willing) would be the only way to actually reverse climate change by using CO2 capture and then electrolysis to put carbon back in the ground. Solar and wind might be able to just sustain human consumption for energy but only fusion would give us enough energy to take CO2 out of the atmosphere.

> Fusion (and fission, if we are willing) would be the only way to actually reverse climate change

Why are you excluding renewables? Argue quantitatively and show your work.

It doesn't scale or do 24/7 power like fission/fusion would. Not sure why everyone is still against nuclear but that's fine too. I certainly have nothing against solar or wind and think we need a mix.

And, honestly, my life would be way better if I could spend twice the energy I do now, without destroying the planet. Energy use is basically a synonym for quality of life for humans. If we can expand it without destroying the world, we should.

More 9s. Closer to 24x7.

My best guess? Space.

With a tokamak, like SPARC (https://www.psfc.mit.edu/sparc) it's clear how energy will be extracted, the vessel will be heated and the cooling fluid goes through a heat exchanger to get the energy.

How would it work here? I imagine something like spiderman 2 where a big ball of fire is suspended in a chamber, but how would energy be transformed to electricity?

Basically the same idea. 80% of fusion's energy output is in neutrons, which would be absorbed by special shielding around the vessel, while the other 20% is released as hot plasma that would heat up the inner surface of the vessel. Coolant loops would transfer the heat to a steam turbine.

Without any googling, wouldn’t be the same way as a fission or coal power plant? Energy from exothermic reaction heats up water which is then used to turn a steam turbine

Seems like it could also be mechanical. There are gigantic Diesel engines that have pistons capable of each absorbing this kind of energy. Have a little bit of gas or water near the target and there will be quite an expansion.

Also a "thermonuclear internal combustion engine" is kind of retro-futuristic and cool.

Largest Diesel engine in the world[1] burns 160g (5.6oz) of diesel each combustion, within a 960mm (38in) diameter cylinder with a 2500mm (8.2ft) stroke. A barrel of oil is about 160 litres and contains 6.1E9 Joules[2], so each combustion stroke is about 6MJ.

The fusion reaction released 1.3MJ of energy. So a single cylinder fusion engine seems realistic!

[1] https://en.wikipedia.org/wiki/Wärtsilä-Sulzer_RTA96-C

[2] https://www.ocean.washington.edu/courses/envir215/energynumb...

A Cheeseburger weighs 3.9oz for comparison https://cockeyed.com/science/weight/cheeseburger-mcdonalds.h...

This is General Fusion's approach.

Wow, cool idea!

https://www.nytimes.com/2021/08/17/science/lasers-fusion-pow...

There's a long history of fraud and misleading / sensational claims made my companies in the fusion space. The industry is nowhere near break-even (total energy into system == total energy out). ITER is a great example today. This is covered well with in-depth research by journalist Steven B. Krivit. He's put together a documentary exposing ITER's many false and dubious claims that I recommend watching: https://www.youtube.com/watch?v=xnikAFWDhNw&t=8s

There are two different definitions of breakeven, and science journalism is usually not good at making those distinct (and yeah, often the press releases from the institutions don't help). "Scientific" breakeven is the first milestone we'll hit, and that's what NIF is claiming to be close to. You're referring to what's known as "engineering" breakeven, which is harder to achieve and requires yet higher fusion yields. Unless you hear otherwise, assume that anyone talking about breakeven means "scientific" breakeven -- if they'd achieved "engineering" breakeven, they'd make sure to spell that out!

I remember a talk ten years by the director of LL describing how a power plant would potentially need something like liquid lithium walls to absorb the energy and transfer heat to steam. That sounded amazing.

Also, ASML did commercialize EUV which relies on blasting a steady drip stream of molten tin, and people 10 years ago said it would never be useful for industry…

Slightly tangential, but this amazing scientific work makes me wonder how much more we could have achieved over the last 30-40 years, had we diverted even a small fraction of military funding to science and space research. Say, $100B/year.

LLNL's budget is $2.5 billion. The entire Nasa budget is around $25B/year; NSF is $8.5B. It's true that there's also military R&D and of course the majority of R&D is private sector[1], but just saying, what a shame that there isn't more of a national focus.

Not only should we be spending more on civil R&D, but what did we gain from that military expenditure, for example the couple of trillion we poured into Afghan for 20 years?

1. https://ncses.nsf.gov/pubs/nsb20203/cross-national-compariso...

Raising budgets don't intrinsically guarantee better results. Would a larger staff of physicists etc. lead to more breakthroughs or quicker results? Or would it just be piddled away in frivolous experiments, nicer Aeron chairs and the like?

A physicist friend from NSF told me once that $50 billion would be about right.

depends on where the bottle necks in the research are. I doubt its man power. its most likely production of the various parts.

generally speaking you don't get great returns on increasing the number of scientists. you do get great returns by speeding up the production of data.

Releasing more energy is good, but is it enough of a difference that the delta can be captured (assuming imperfect capture process) + is it able to offset the cost of the expensive laser setup (maintenance)?

Baby steps, there are any number of issues to address if the goal was to create something that is energy producing for consumption. However, taking out even any aspect of commercialization or scaling this is an important milestone in terms of science and engineering. That's not to say don't ask those questions, it is just allow the excitement of progress while asking future questions.

The article states that the reaction produced more energy than the fuel absorbed, not more energy than it took to run the lasers. I expect the efficiency of power transfer to the fuel is pretty low.

You're right, they had 1.8 MJ of photons hitting the target, but something like 400MJ of energy going into the laser, which is inefficient (<1%).

Wow, I didn't guess that low. I guess it makes sense though.

also mentioned chain reactions which would be one way to generate more energy than input even if your input was high.

wow, I remember my friend in grad school working on this.... 20 years ago? They said it would never work and was just funded to keep livermore going.

Holy shit, they got the power and energy units correct.

One would hope, that's the official American Physical Society publication...

> "These extraordinary results from NIF advance the science that NNSA depends on to modernize our nuclear weapons and production. It also offers potential new avenues of research into alternative energy sources that could aid economic development and help fight climate change."

Well, at least they're pretty honest about the order of their priorities.

I can't help but wonder, with fusion: When we'll be able to harness this energy in a stable and net producing manner, yes that will cut carbon emissions and solve the nuclear waste problem, but also, is it going to be the catalyst that will enable humanity to accelerate wreaking havoc on what's left of our ecosystems?

> is it going to be the catalyst that will enable humanity to accelerate wreaking havoc on what's left of our ecosystems?

The question is how cheap can it get, can the energy production scale up vs cost, and how much does maintenance cost.

This is a good video about fission energy production economics https://www.youtube.com/watch?v=cbeJIwF1pVY

If one of these fusion reactor projects results in a competitively priced power plant, ok, we can reduce fossil fuel energy production towards zero in a few decades. That's pretty good for the environment but nothing really "new" is possible.

If one of these fusion reactor projects results in a 10x reduction in the cost of electricity... then we have something new. Things that people didn't imagine being possible before become possible.

Things like desalination instead of taking water from rivers or aquifers because it's cheaper. Tearing down dams because the power isn't needed. "Farms" in skyscrapers packed with artificial light where food can be produced without pesticides or herbicides because it's a controlled environment. Using landfills like mines, extracting tiny amounts of useful materials so ordinary mining becomes much less needed.

You can also think of plenty of things cheap plentiful energy could make happen that are destructive too... it is difficult to project and I assume will go in both directions.

For reference, the hydraulic press channel recently demonstrated what the fusion energy released here looks like. 10^6 joules is basically one hand grenade. Very exciting! https://www.youtube.com/watch?v=eDA7EUDOiwU

Just for comparison please consider that a jelly donut contains about 1.6MJ.

So does a 100 kg, 1 m diameter disk spinning at 56 Hz. I'd rather be sitting next to a donut if that disk stopped in less than a second.

Somehow I get the feeling you’re familiar with the jelly donut analogy WRT inertial confinement fusion.

A candy bar is equivalent to a stick of dynamite, energetically. But then, energy and power are not the same :D

Probably need to use more fuel for a sustained reaction?

There's no sustained reaction in this setup, it will be dropped targets and lasers pulsing at the right time.

I am sorry I did not mean indefinitely sustained. Surely not all of the fuel "ignites" at the same time? Shouldn't a larger mass of fuel increase the energy output (there's more of it to "burn")?

Yes, a larger mass of fuel would produce more output, but it would also require more laser energy to compress it. They're already maxing out the lasers they have.

What a great distraction from the real problems!

If we had that free limitless renewable energy, and we used it as we do now to fuel "growth" building malls and car parks, extracting ores from the crust, and produce pesticides, then we will have solved no problem at all.

Spieces do not become extinct, they are being exterminated. Energy production is but a tiny part of the ecological crisis we're in. We need to solve the energy usage problem, not its production.

This is madness.

extracting ores from the crust

The Earth has an insane amount of material. It's the greatest tragedy that life occupies only the thinnest film on the thinnest edge of the Earth. The more we can make use of the full potential of the Earth, the more life there can be. It's a waste to just leave all that matter buried, doing nothing more than providing gravity.

We need to solve the energy usage problem, not its production.

More energy means more solutions. Think carbon sequestration, vertical farming, building megastructures to combat sea level rise, climate engineering, or even just pumping heat into space as infrared.

We are indeed in a climate crisis, but 85% of the crisis is that people have given up on the future and just want to panic.

For me what you write reads like "we need to focus on treating the symptoms rather than the cause of our problems."

Are we so attached to always having more and more? mostly to the benefit of a handful of super wealthy? While our democraties become authoritarian and ecosystems collapse?

Social justice (not a skewed idea of "progress") goes hand in hand with solving the ecological crisis.

It seems like your "real problem" is that you want to tell 80% of humanity that they will never be permitted to achieve the same quality of life we enjoy in Western society today.

Good luck with that.

Not only that but the West must also regress, that is correct. That is pretty much obvious once you have accepted that current growth is unsustainable and has been for a long time.

But we can (and probably will) keep pretending, that's fine, it will just be more and more "to late" and we'll cause more and more irreversible damage.

There is no green growth.

Heck, I shouldn't care, I have no children and a comfortable life. Let's keep playing music until we sink.

> The shot...demolished the facility’s previous record yield

Thought 'demolish' was going in another direction there

is there somewhere a summary of “basic science” problems that need to be solved to make fusion feasible? And - would throwing more money at the problem?

This book: https://www.simonandschuster.com/books/The-Star-Builders/Art... just came out and is a very accessible explainer.

The maybe-tldr version: we can make fusion occur, but it currently (well, until today) takes more energy to make it happen than we get out. We have good models that predict this relationship, and it mostly boils down to maximizing the "triple product": temperature times plasma density times confinement time. The two most popular broad approaches are "magnetic confinement" (holding a plasma for awhile with magnetic fields) and "inertial confinement" (taking a capsule and rapidly mechanically compressing it, with lasers or a railgun or something, which is what this NIF thing is), and each chooses to maximize the triple product by leaning on different multiplicands -- inertial confinement is much shorter time, but higher density as compared to magnetic. For both, the other factor is plasma instabilities: plasmas don't like to behave, and like to leak out of their enclosures or not maintain the shapes you want them to, and lots of research seems to be about controlling those.

Beyond that, what the challenges are depend on the approach you choose. For inertial, bumping up the triple product seems to be mostly about building bigger and more powerful systems, and managing plasma instabilities. NIF also uses an "indirect" approach where the lasers get (inefficiently) turned into X-rays which then compress the plasma, and "direct" inertial fusion has even bigger plasma instability problems to solve.

For magnetic, the most mature technologies, tokamaks, have well-understood properties in terms of plasma management, and the main still-to-do work had been thought to just be making the machines bigger, which is what ITER is doing, but the recent change is the development of high-temperature superconducting magnets, which might allow for much higher-strength magnetic fields, which would allow for success with smaller machines (that's what, e.g., Commonwealth Fusion, is pursuing). In either case, the goal is just bumping up the triple product until we get to net gain. Other magnetic approaches (stellarators, etc.) are probably at a somewhat-earlier stage of understanding plasma behavior.

For both inertial and magnetic, there will also be development needed after net energy gain to get enough of a gain factor that the economics actually make sense and things can be mass-produced (current thinking is that to actually be economical, we need to get to ~30x energy out compared to what went in), and also likely some materials-science innovations needed to keep the reactor from wearing out due to high neutron flux, and possibly some work producing tritium, the likely fuel, from lithium.

Beyond those MCF and ICF, there are also a bunch of other less-mature technologies that startups are exploring that might also produce good results, and (the founders think) might do so more efficiently than the big approaches, but they're not as far along, and the work still to do is more basic-science-ish. This would be things like Z-pinch, fuel cycles other than deuterium-tritium, etc. etc.

Also, realizing I didn't answer the "money" question. Fusion enthusiasts definitely think so, and personally (just random interested lay-person) it seems like for tokamaks in particular, the physics are now well-enough understand that it's probably just a matter of money/time, but it's hard to say for sure.

thank you!

"just around the corner" quote from 1955

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