581 Comments
Comment deleted
Expand full comment

This is a technical puff piece for fusion; it is not a book review.

Expand full comment
Jun 17, 2022·edited Jun 17, 2022

“ Stellarators also have the best name, look the coolest, and are my favorite.”

It was worth my subscription just to get nuggets like that.

Expand full comment

No thoughts on General Fusion or TAE? As an interested lay person, I like General Fusion's approach (Steam pistons! Liquid metal vortex!), and it seems like they've made substantial progress, recently settling on a site in the UK for a demonstration scale plant.

Expand full comment

There seems to be a lot of negativity around this subject. My understudying is the science of this is accepted. It will work. The great difficulty is the engineering. This will be by far mankind’s greatest engineering challenge.

A lot of people will be upset if engineers solve this problem and the world continues on in energy abundance. How can we have Mad Max or some other dystopian future if engineers solve all the problems? Mankind must suffer!

Expand full comment

Hello everyone !

I just made this account so I can engage in the conversation, while still being an anonymous reviewer. I will try to answer all the questions I find in the comments.

I have invited Jason Parisi, one of the authors of the book, to come as well.

Expand full comment
Jun 17, 2022·edited Jun 17, 2022

This review speaks at length about fusion but I'm not clear how exactly it is used to generate power - is it still fundamentally producing heat for steam for electricity generating turbines? Later on the article mentions another option for generating electricity but does not expand. I think the article would have been a bit stronger with a brief overview of the full plant concept including the stages beyond fusion itself.

I'm hopeful that the technology works out, will follow it.

Expand full comment

I've been working on fusion for the last year under an Emergent Ventures grant, and working alongside Schmidt Futures and Adam Marblestone to identify philanthropic opportunities in the space. That doesn't by any means make me an expert, but it's enough that I'm willing to share my opinion.

I think every prediction on this list is about an order of magnitude too optimistic, with the exception of CFS and ITER. I would also clarify that while Q>5 in steady state would be a momentous achievement, it's still puts us a far ways off from fusion energy that is economically or climate relevant. For example, I am fairly optimistic that ITER will "work", but it doesn't actually provide us with a path to commercial fusion energy.

Having said that, I think fusion is absolutely worth pursuing, and that in fact, we're severely underinvesting at the margin even with my revised predictions. Concretely, for the industry as a whole, I would give us a 20% chance of having fusion energy on the grid by 2035, and a 35% chance by 2040.

I'm happy to chat more with anyone here who's working on fusion, or just anyone who's interested:

KyleSchiller@gmail.com

Expand full comment
Jun 17, 2022·edited Jun 17, 2022

You haven't convinced me that this is anything more than the usual techie over-optimism: "yeah all the other times failed, but this time for sure!"

You also don't explain *why* the US etc. gave up on funding fusion research, or why other countries didn't surge ahead with this technology and leave the US eating their dust. Instead, your best candidate is one that is funded by a grab-bag of countries who may or may not decide to pull out at any time.

My impression is that fusion didn't get funded because "too difficult, too technical, a lot of ways it can go ka-blooey, and there were easier, cheaper methods of energy production".

Even what you describe as the new way forward with private funding is a lot of "doing experiments" and not "by 2040 we will have commercial energy generation via fusion".

I'm sorry to say that from this, I'm expecting fusion to be left behind as one of the 'flying cars/moon colonies' dreams of the 70s that never happened, and that renewable energy such as wind, solar and so on will take up the slack (along with nuclear) when it comes to being the shiny new tech for energy generation.

And as Derek Jones points out, you haven't reviewed the book, you've told us (very informatively) about fusion and what your opinion of the state of play is.

Expand full comment

(1) Do other experts agree with the 80%-by-2035 prediction?

(2) Why should I care if we "get fusion"? Does the cost of energy decrease (how much?), or what other effects are significant?

Expand full comment

Footnote 5 is just a duplicate of 4.

I recall over a decade ago Mencius Moldbug pointed to ITER as his example of over-funded science:

https://www.unqualified-reservations.org/2010/01/hanson-moldbug-debate/

I don't know if he's talked about fusion at his substack, since a paying subscription is required to comment there.

Expand full comment

I think there are quite a few more private fusion companies than you listed, for example https://lppfusion.com/

Expand full comment

Great article! I had no idea we made consistent progress on fusion for so long. However I'm very surprised that the author thinks that three of the current major companies working on fusion are likely to succeed (70% by 2040). That seems incredibly unlikely to me, as just in general most startups fail.

Expand full comment
Jun 17, 2022·edited Jun 17, 2022

It doesn't seem to be controversial that we will reach fusion eventually if we follow tokamak extrapolations (though I think your timeline is super optimistic). The question is how cheap and scalable would this generated energy be. It is very possible CFS's SPARC will go online, generate energy, but self-destroy through neutronicity.

In any case, I'd love to hear: what is your prediction for fusion energy costing under 3.2¢/kWh (or any other price) in 2035 or 2040?

Expand full comment

I strongly suspect fusion power has already been solved, although the specific details is a confluence of both conspiracy theory and culture war. (Basically, just, suppose a government has fusion power, and imagine what they'd do to situate themselves before releasing it.)

Expand full comment

> Other significant milestones are Q=5, ‘burning', and Q=, ‘ignition', when the fusion sustains itself without any external heating.

Is there supposed to be a number after the second Q?

Expand full comment

Nice essay about fusion power but in what way is this a book review?

Expand full comment
Jun 17, 2022·edited Jun 17, 2022

I'm also surprised with the amount of credibility you give to NIF, which seems to be generally accepted as a nuclear weapons maintenance program dressed up as fusion research. My impression was that no one in fusion power takes the NIF seriously as a path to actual energy generation.

Expand full comment

If by "get fusion" we take the definition in footnote 1 (somebody does an experiment that gets Q > 5), then yes, we will probably get fusion on something like the timeline the author describes. However:

1. Q = 5 is *far* from commercially viable. Q represents an energy gain in terms of the energy going into the plasma. It does not account for all the other energy needed to run the system. The most optimistic number I have seen is that Q > 20 is commercial fusion. And even that is optimistic because of point #2.

2. Neutronic fusion (basically everyone doing D-T fusion) relies on neutrons crashing into stuff and generating heat, which then boils water, which then drives a steam turbine. So one input into the electricity economics for fusion is the cost of the generating equipment, the steam turbine itself. If we look at the other modes of electricity production that also use steam turbines, and compare the cost of their steam, we will see that fusion is clearly worse than everyone else. Coal: we mine this thing from the ground and set it on fire and it gives us heat to make steam. Fission: we mine these magic rocks from the ground and hold them together and it gives us heat to make steam. Geothermal: we drill holes in the ground until we reach hot temperatures, circulate water, and it yields steam. Fusion: we build the most complex and finnicky machine ever known to man (read: very expensive) and then it produces heat which we can use to make steam. Neutronic fusion is an expensive way to make steam, so the economics are unlikely to work if it is actually competing on a level playing field with other ways of making steam.

3. The insanely complex and finnicky machine neutronic fusion uses to make heat will need to undergo maintenance, and perhaps more often than other machines, because it is constantly being bombarded with radioactive neutrons. When it needs to undergo maintenance, it will be radioactive because of all the radioactive neutrons that have bombarded it. So maintenance will be expensive.

4. The neutrons emitted by neutronic fusion can be used to breed plutonium and other fissile material, so the technology will have to be closely controlled, which is a further headwind on it ever becoming economic.

5. Fusion advocates have tried to get fusion to be perceived as "safe" because it cannot lead to a meltdown. While it can't melt down like a fission reactor, fusion can suffer from a confinement failure (i.e., a big explosion). A confinement failure is likely to strew radioactive parts everywhere in its vicinity.

D-T fusion is indeed the closest technology to scientific breakeven (Q > 1) and maybe even to something like Q > 5 like the author suggests. But that does not mean it will ever be commercially viable. I believe that the scientists working on it know that it won't ever be commercially viable, but they don't want to say so because they want to continue to get funding either from governments or private investors to achieve the breakeven milestone.

Most of my criticisms of fusion are totally standard; they were noted by Lawrence Lidsky from MIT in 1983. http://orcutt.net/weblog/wp-content/uploads/2015/08/The-Trouble-With-Fusion_MIT_Tech_Review_1983.pdf

Expand full comment

This is a great article but this is not a book review.

Expand full comment
User was banned for this comment. Show
Expand full comment

This is the only non-Scott book review I've read the whole way through. Thank you :)

Expand full comment

The formatting has been lost in the nuclear equations, making them very hard to read (like 36Li instead of superscript 3, subscript 6, Li). Some symbols have also been lost, like arrows and what I assume was an infinity symbol. Is there any way to fix this in Substack?

Expand full comment

Not a book review, and a remarkably immature writing style for a professional physicist.

Expand full comment

The dark horse in the energy race is deep geothermal. Watch for it to make a move in turn three.

Could somebody find a book on deep geothermal and write a review of it? (Probably less math.)

Expand full comment

Not convinced.

Expand full comment

Stylistic point, you talk about how the triple product is the most important thing for fusion, but don't actually explain what it is. You do quite well in some areas in explaining things in a way that doesn't require much background, but in other places slip over it

Expand full comment

The peanuts comparison is amusing but doesn't seem particularly revealing since the US is far from the only place finding fusion research. Would be interesting to look at global spending on fusion and how that comaores to other projects.

One of the interesting things about fusion seems to be the unusual level of international cooperation

Expand full comment

Another fusion physicist here (just a novice, though.)

What I always was afraid of regarding ITER was an Apollo Program-style Phyrric victory. "Hooray! We've achieved the nigh-impossible! Go us! Obviously not cost-effective, though, so let's basically shelve the whole field." Anything that's cost-effective is going to have to be massively simpler and cheaper than ITER - being just a reactor rather than a super-diagnosed experiment would help, of course - and I do think that the key innovations that come to the rescue probably are indeed going to come from outside the field of plasma physics proper.

Take heavier-than-air flight, for example. Why was it first invented when it was, around the turn of the 20th century? It's not because the Wright Brothers were far beyond everybody else (their advances in stability and control notwithstanding); you'll note that there were rival claimants to the title, some of whom did pick up support from major institutions. But they were all within a few years of the Wright Brothers, anyway - why's that? The reason is that the technological landscape had simply advanced far enough at that point, to the point of engines with sufficient power-to-weight ratios becoming available.

Can you imagine trying to make do without? Achieving heavier-than-air flight for humans by pushing the field of aerodynamics to the limit to make a perfectly-optimized jumbo-jet-sized airframe that is, in the end, capable of briefly lifting a baby into the air because all the rest of its power needs to go into lifting its own weight? There's a Phyrric victory for you.

High-performing superconductors may be, I feel, the equivalent of high-performing engines here. Fusion power is (if I'm not terribly mistaken) proportional to the strength of the magnetic field to the fourth power. Just like you could make a brick fly with a good enough engine, you may well achieve the plasma-physically "impossible" just by spamming more magnetic field strength at the problem.

Which is something I'm hoping for, myself: my interest in plasma-based nuclear power is because it's the sort of power source needed for high-thrust, high-specific-impulse (and thus high-squared power!) space propulsion. Tokamaks aren't the most rockety concept out there, I'd have to admit. So I'm looking forward to what we're able to develop - a brighter, positive-sum vision of the future is something I think is worth working for.

Expand full comment

> This reaction can be written as:

> 12D +13T 24He +01n .

> The subscript is the number of protons that each element has and the superscript is the number of protons + neutrons [4]. Both of these numbers are conserved: if you add up the total superscript on the left, it must equal the total superscript on the right.

This has been severely mangled; it appears that the superscripts are now just normal text and the subscripts have disappeared.

Expand full comment

15 years at best to get positive outcomes on a few plants. If the best we can hope for is 5 plants with Q>5 in 2040, and they take 15 years to build, then maybe we'll have 20 by 2055. And then maybe we'll have 100 by 2065. How many plants would you need to meet current energy demands?

And then you have the other cost considerations. Sure, the fuel may be cheap, but seriously the engineering hours and other material inputs into these reactors needs a LOT of gains in efficiency before they're feasible. Even if you assume they depreciate as fast as other plants, because of all the specialised equipment their repairs and maintenance is likely to be more expensive and the capital costs will be huge too. There is more to operating costs than fuel, and this is nothing I ever see addressed in any of the pieces I read on the topic.

It's cool science, and we should pursue it. But at this point I think it's the future of energy for the 22nd century, not this one sadly.

Expand full comment

Heh, peanut subsidies

Expand full comment

Some of the probabilities seem optimistic. South Korea's DEMO having the same probability of success as ITER when it's basically conditional on ITER's success? All these speculative private companies having a 70% chance of achieving fusion, the same as ITER's, despite having no revenue?

As a total layman it seems like these might be more accurately modelling a question like "How likely is it that XYZ will achieve fusion by a certain date on the merits of their technology, given that they don't go bankrupt or catastrophically fail or get defunded by a new government or anything else unrelated to technical problems?"

Expand full comment

The subscript and superscript do not appear to be working.

Expand full comment

"The fusion reaction chain in the sun burns six protons (hydrogen nuclei) into helium-4, two protons, and two positrons over the course of five fusion reactions. What we do is simpler."

Is this why human-made fusion reactors have so much higher energy density than the Sun? I used to think that fusion of course would be possible, because it's happening constantly in the Sun. But with more research, I found that a glob of sunstuff is slightly warm and slightly glowy, and the only reason the sun is so hot and so bright is because it's so big that the surface area to volume ratio means that that slight amount of heat and light builds up to an incredible degree. The exceptional thing about the Sun as a power plant is that it will keep on burning for billions of years.

Since any fusion power plants we build will be a lot smaller than the sun, and reasonable-sized globs of sunstuff would be pretty useless for power generation, it seems like we'd have to do something fundamentally different from what the Sun does to get useful results.

Expand full comment

> Q is the ratio of the amount of energy you put into the fuel to the amount of energy produced by fusion.

I think this might be backwards? Should be the ratio of power produced to power input.

Expand full comment

I am glad to have read this, so I'm glad it was picked as a finalist... but it's an essay, not a book review, so I'm not likely to vote for it.

Expand full comment

I really like the section on private funding. I always figured fusion was impossible because capital markets manage to throw trillions of dollars towards any idea at least as good as “sell pet products online using a sock puppet” or “lend mortgages to people who can’t afford them.” “Unlimited free energy if you overcome some tough physics and engineering problems” seems like at least as good an idea to throw money at. This article seriously updated my priors.

Expand full comment

Proton number is not generally conserved in fusion. For example, in the sun proton-proton fusion gives a product of one deuterium atom, which has one proton and one neutron, via beta decay. It does so happen that D-T fusion conserves proton number. Also, the graph has the wrong inflation correction. The original data is in Fiscal Year 1978 dollars, which converts into 2012 dollars at less than 4:1, so the never-fusion constant $200M in the original becomes $800M in 2012 dollars, not the $1B portrayed in the graph.

Expand full comment

Also, Alcator C-Mod closed in 2016 and has not reopened.

Expand full comment

Are there any efforts planned toward building stellarators that use high temperature superconducting coils? From your description, it sounds stellarators are pretty great, so it would be interesting to know if they could also take advantage of a stronger magnetic field.

Expand full comment

I'm kind of surprised high Tc superconductors have made such a difference, if you are talking about the perovskite ceramics. Not my field, but I thought they had problems with current density, and surely you need a very high current density for compact tokamaks.

Expand full comment

This was a great review. I like your writing style. Did you take lessons from Julius Caesar?

Expand full comment
Jun 18, 2022·edited Jun 18, 2022

That [CLASSIFIED] is funny since it's well known (implosion). It feels more like PR to unlink from nuclear weapons research stigma.

Expand full comment

Most important outcome of this review - I finally learned why ion plasma and blood plasma are both called plasma. And it's pretty disappointing.

(other than that it's not a book review, but it is an excellent Much More Than You Wanted to Know post!)

Expand full comment

This is a really interesting and informative article about the state of fusion energy experiments, but I'm puzzled about why it's being presented as a book review. It mentions a book, but seemingly only in passing.

Expand full comment

Unintended consequences:

Centralized power generation has large economic incentives to eliminate the competition of decentralized power generation. Centralized power is a target that needs to be defended.

Big is bad.

Expand full comment

@Fusion Reviewer.

Great article, thanks for spending the time reading the book and writing this review.

You mentioned that stellarators are your 'favourite.' I think that a huge advance in the field in the past couple of years has been on stellarator optimization. Here's some preliminary reading:

https://terpconnect.umd.edu/~mattland/projects/6_optimization/

https://simsopt.readthedocs.io/en/latest/

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.035001

Next frontier in stellarators is optimizing for turbulent transport, which I suspect will be much trickier.

Expand full comment

Great book indeed! See also "The Star Builders."

Professional skeptics like to say that nuclear fusion energy and AI are always 20 years in the future, but in the last few years there has been measurable and promising progress toward both.

Waiting for fusion energy, whose operational deployment will likely take, yes, 20 years (!!!), conventional nuclear energy is the only viable way to move away from fossil fuels in the short term.

So let's invest more in fusion research, but also in building more old-fashioned nuclear reactors, because that's what we have right now.

Expand full comment

Great article, shame the second sentence is so inaccurate. Most elements heavier than helium are indeed created by fusion - but not all. For example the elements lithium to boron are created by cosmic spallation. Very heavy elements (such as gold) are mostly created in neutron star mergers, which are not really fusion.

Expand full comment

Regarding Helion, what's your source for the 25% D-T reaction?

As I understand they plan for 66% D-D + 33% D-He3. Since half of D-D reactions yields one He3, the fuel cycle only needs deuterium as input and has tritium as a (valuable) waste product.

Also D-D reaction is not aneutronic but the neutrons are slower than D-T's

Expand full comment

I have a manifold prediction market on the likelihood 2% of the grid is fusion by 2050. It’s pretty low (33%). https://manifold.markets/J/will-fusion-provide-2-of-us-electri I’ll write some criticisms of this post in the morning.

Current state of the art is q=1 with exorbitantly expensive DT fuel. Economic breakeven would require q>4 using DD fuel instead, and DD requires ~5x higher temperatures. Radiative losses are usually proportional to the fourth power of temperature, and there are other additional ways for electrons to lose energy at extreme temperatures. A design that yields Q=1 at temp T would probably be like Q=0.001 at temp 5T. So they need to get three and a half orders of magnitude better.

Expand full comment

Very interesting comments to this review. I think the review is good and faithfully follows the book and there is no reason to denigrate it. It's just that the book itself is simply a description of what is the state of fusing at this moment.

Some people apparently expect more from a book. It had to be a story, not just the list of facts. Other people filled to void by inventing the story (that's what our brains do with everything) but that story is boring – “scientists were slow working on fusion energy because it is complicated, but gradually got better and after 30 years or so it will work and everybody will live happy forever”. And now they are criticizing the story and are not happy with it.

Expand full comment
Jun 18, 2022·edited Jun 18, 2022

As a european taxpayer (that's not true, I don't pay taxes), I will be very upset if an american company reach fusion before us.

Re Inertial confinement: in a seminar at my university, a person working at NIF candidly admitted that they are mostly working at [CLASSIFIED] and they are not going to produce a power plant

Edit: I wouldn't be this confident in private startups now that monetary policy is tightening. I am afraid that money will flee from risky technological startups towards safer options.

Expand full comment
Jun 18, 2022·edited Jun 18, 2022

Scott, maybe it's time for a Guest Post Contest so people stop trojan horsing them in as book reviews.

Expand full comment

Question not just for the author: assuming that this is correct and the likelihood of nuclear fusion being imminent is underestimated: what is currently under/over-valued by the market?

Expand full comment

This is a bit like reading an article confidently predicting "we will have GAI by 2035" and then seeing in the fine print that they define "have GAI" as "there is a dense language model with 10x parameters than GPT3".

Expand full comment

In case it isn't obvious, this entry should have been disqualified for not actually being a book review. It doesn't even pretend to be one! So, as a book review it gets a full zero out of ten from me. As an evangelising puff piece, about three out of ten - the single word sentences are genuinely cringe-worthy. However, the biggest problem with it is that it entirely skirts over the question of whether there is any possibility of fusion being an economical way of generating energy. Not impressed.

Expand full comment

For a supposed review of a book titled "The Future of Fusion Energy", I am missing a big part of, well, the future of fusion energy. Let's say that ITER is a whopping success, and they achieve fusion. Yay for science! But - how long until a reactor can be designed and built that actually generates measurable amounts of power - let's say, a few hundred MW? How expensive would it be? How big would it have to be, just in terms of the physics of transporting away the generated heat? How quickly could this ideally be rolled out?

The thing is, if we want a highly sophisticated reactor that generates power, but costs billions to build and creates a whole bunch of radioactive waste in the process, we already have those. They're called nuclear power plants. Why should I get excited about an alternative that may or may not be technically feasible, may or may not be economically feasible, and may or may not be stable and clean?

Expand full comment

I concur with the assessment that this doesn't read like a book review.

I also have significant concerns with the one-sentence brush-off that these probabilities are unlikely to be correlated. They're all tackling the same problem, and their approaches are different but--except for inertial confinement versus magnetic confinement--not THAT different. I believe that the correlation between the probabilities is far higher than the reviewer is letting on... or at least the reviewer needs to show their work.

Expand full comment

I saw this critique of fusion linked: https://inference-review.com/article/the-quest-for-fusion-energy

(h/t: Marginal Revolution):

There are some substantive appearing challenges. Care to respond to these?

Expand full comment

I'm a bit confused by the discussion of funding. The claim is made that funding for fusion research has been very low in the US, but lots of expensive experiments are described. I guess international funding is higher? I wish the article went into a bit more depth about funding levels.

Expand full comment

Review aside, my question is how optimized fusion stands up against optimized geothermal energy in terms of economics and practicality. MIT seems to be the center of the energy universe, so it's not surprising that the front runners in both fields are start ups coming out of there.

https://newatlas.com/energy/quaise-deep-geothermal-drilling-questions/

Quaise is one I'm really excited about, and it seems to be imminently practical. But I would love to see an article as in-depth as this discussing the issues and history of the field. Because it seems to me that, were this technology to get working, the simplicity of a deep hole that can be plugged into existing coal fire plants (and then run forever) without building-sized techno-marvels would pull ahead.

Any input?

Expand full comment

Question for the reviewer: I read a short story a long time ago (so I might be misremembering and they were trying to get fission instead of fusion) and in the story they thought that deuterium-3, an isotope of hydrogen with 2 neutrons, would be easier to work with. How true is that?

(The conceit of the story was that D-3 is hard to make on Earth, but that either Uranus or Neptune (can't remember which) had it in abundance in its atmosphere, somewhere on the order of quadrillions of dollars worth, so a private company sending out automated harvesters (it was a robot themed scifi anthology) was seen as a high risk, obscenely high reward strategy.)

Expand full comment

Excellent overview on the tech.

Rest of it: not great.

I particularly like how the profusion of 50%/70%/whatever probabilities sum up to success for sure. Clearly a techno-optimist with very little experience in the difficulties of realizing lab visions into systems that actually work commercially. For example: where is the author's personal experience in a community of estimated success actually yielding results? i.e. has the author's estimates of success ever been tested against actual outcomes?

Nor am I particularly impressed by the funding aspect. Let's take whatever was actually paid, in the author's graph, as actually representative (it doesn't seem like it which I will get into later): the cumulative spend in 2012 dollars for fusion research from the 1970s to today is easily $50 billion.

Large Hadron Collider cost $5B; Apollo program cost $25B - it seems we have long ago exceeded the "spend" the author blithely projects as necessary. ISS is $150B - but $50B cumulatively (note 2012 adjusted dollars) vs. $150B is not nothing.

Nor are government cost estimates to be trusted - the California high speed rail as well as programs like the F35 are monuments to something besides success in outcome as opposed to success in pork barrel.

Then there's the entire commercialization aspect.

It is notable that there are absolutely NO numbers for the cost of fusion energy, anywhere in the article.

This should matter, no? Just because you get more energy in than you get out, does not mean that energy is affordable. The cost of fuel isn't necessarily the driving factor - we have real world examples like nuclear power plants where the construction plus lawfare costs are so enormous as to materially impact LCOE.

So net net: I'd be happy of the author is right - but I will absolutely not hold my breath waiting for it - not the actual scientific/engineering achievement of commercial fusion energy much less the possibility of fusion energy replacing other sources.

Expand full comment

@Fusion Reviewer: Why did the DOE pull funding from the MIT group that later formed Commonwealth Fusion Systems / SPARC? And, in fact, is that actually how it happened? From a google search, it looks like DOE *awarded* funding to Commonwealth Fusion Systems in 2019 https://federallabs.org/news/doe-awards-infuse-funding-to-brookhaven%E2%80%93commonwealth-fusion-energy-project . Are you sure it was that DOE pulled funding -> the group formed a startup, rather than the group formed a startup -> DOE gave them startup-funding money and pulled their academia-money? I have no idea how plausible any of this is, but I haven't thought of any other explanations for why DOE would pull funding from an MIT group but then give money to a startup of the same people doing the same thing.

(BTW I really liked this and was happy to finally stumble into a fairly short, readable, and accurate assessment of the current state of affairs! So thank you for the post.)

Expand full comment

What about General Fusion? (MTF)

Expand full comment

Review-of-the-review: 7/10

I'm glad I got to read this. It's a quantitative and specific introduction to the optimistic case for fusion power, with a book recommendation for those interested in learning more. But... it's not a book review? It's not any kind of review, really; it's forthright boosterism. Which is a good thing to have! Fusion energy is super cool and we should pursue it! And this post makes concrete claims that can help us understand and measure progress-- that's great! But I can't consider myself informed about fusion prospects just from reading this.

Like, as soon as I saw Figure 1, I thought to myself: this looks like the kind of stuff academics say to get funding for their projects. And the reviewer accepts this uncritically? Grant-writing, like political campaigns and Survivor, is a game whose sophisticated players expect that everyone including themselves is stretching the truth. The review's only acknowledgement that reality might diverge from projections is the offhand reference to a 20-year gap in the exponential triple progress trend as being due to needing larger reactors. (Why were they suddenly needed? And why did that need create such a discontinuity? The reviewer never explains.) I've also seen criticisms of the economic feasibility of fusion power on a variety of grounds (tritium production, facility requirements, power capture...) which admittedly are somewhat outside the scope of the review-- but I'd love to at least see them acknowledged and the risks quantified.

I won't be voting for this finalist but I was happy and interested to read it. As always, many thanks for contributing!

Expand full comment

Thank you for the overview of recent progress in fusion tech, imao it's much more interesting than just learning about another random book.

Expand full comment

I've been following fusion since the 1960s when GE had an exhibit on it at the 1964-1965 World's Fair. It does feel closer than it did back then or in the 1970s with its energy crisis. In retrospect, we can see how some of the obstacles may have been removed by means of high speed computing, high temperature superconductors, high precision deposition machining, laser technology and a host of other technologies that didn't exist back then. There are obviously obstacles still to be removed. Back in the 1970s, I knew MIT physicists who were working on the problem, and in retrospect it feels like they were trying to fuse nuclei by rubbing two sticks together.

Expand full comment

Very cool primer of the state of the field, thanks for writing it!

I can't help comparing your bullish view of the future of fusion with the bearish one expressed by Daniel Jassby (formerly of the Princeton Plasma Physics Laboratory) in this recent article:

https://inference-review.com/article/the-quest-for-fusion-energy

Personally I know nothing about plasma physics, but my understanding of Jassby's main points is:

1. Tokamaks like JET produce a mix of beam-thermal and thermonuclear fusion. Theory says that beam-thermal fusion is limited to Q<2. Thus, to achieve higher values of Q, tokamaks must transition to a design where thermonuclear fusion predominates. Is this an extra challenge that ITER must overcome, beyond being a bigger version of JET?

2. Jassby is also skeptical that the breeding reaction can produce all the necessary tritium in practice. He claims that Tokamaks would need external sources of tritium, which are difficult and expensive to obtain.

3. Based on a comparison of 2021 results from JET (tokamak) and NIF (inertial confinement), Jassby claims that inertial confinement holds more promise than magnetic confinement -- although it also faces significant engineering challenges. In particular, he argues that inertial confinement is better able to deal with issues 1 and 2 above.

4. He concludes that "the stark reality is that practical fusion-based electric power remains a distant prospect. It is likely unachievable anytime in the next half a century."

I cannot evaluate Jassby's claims, and don't know if his preference for inertial confinement is due to some personal bias. Thoughts?

Expand full comment

I liked this, and I don't care whether it counts as a book review. I'm happy to read the broader category "essays with a specific book as the occasion". I'm not as interested in this specific book as I am in fusion power, the thing itself; so why constrain the essay to merely summarizing and evaluating the book?

Expand full comment

I'm afraid I'm not familiar enough with fusion to understand the benefits of getting fusion

Expand full comment

Can I still vote on this review if I'm pretty sure I know how you are? Give your pretty orange cat a lot of pats for me.

Like many commenters, I do think you underestimate the difficulty of going from engineering breakeven to economic viability: not so much the engineering problem, but the haphazard funding, the bad PR of anything nuclear, the regulatory mess, the lack of political interest in anything that takes >5 years, etc. Hopefully China will succeed, and the west will freak out and try to catch up.

IMO the crucial takeaway from the post is that plot: we haven't (so far) run into serious problems making fusion work, and we don't even expect to run into more than average, we just haven't had funding to try at all. I didn't know that!

Expand full comment

OK let's say it all works out as you say and we get ready to build fusion power plants. What are the costs of those plants going to be and won't they suffer from the same regulatory laws for safety and such that keep fission power from being economical? Sensible regulations for fission (and fusion) plants seem like the most important step... Well and build Yucca mountain for waste storage.

Expand full comment

Great writing and interesting topic

Expand full comment

So disappointing that we have not made fusion a funding priority. It would change everything about the CO2 and climate change issues. The funding graph was an eye-opener.

Expand full comment

A common criticism of the smaller experiment approach is that the heat flux through the walls of the machine would be too significant to prevent damage, and if your machine is too small it will just "melt".

Particularly, ITER was designed to support a heat flux on the order of 10 MW/m^2, whereas SPARC and others would be moving something on the order of 100MW/m^2 from the plasma through the walls of the reactor. A professor of fusion materials I spoke with told me that this makes small reactors impossible. Could I get some perspective or suggested reading materials as to why this might be wrong?

I know that the superX diverter can reduce this heat flux significantly, but as far as I know SPARC has not specified their diverter configuration.

Expand full comment

I understand why everyone's complaining about this not being a book review, but to me the value of the ACX book reviews are not in their analyses of writing styles or authorship, but in the way they give me insight into topics and fields I wouldn't have looked into myself. Criticising the book's treatment is part of that, but I thought this review achieved that when it covered the research in the years since the book had been published. I enjoyed it!

Expand full comment

i agree that scaling may solve some of the ratio issues, but am more intrigued by point elon brought up in his video about allegedly difficult to solve maintenance issues. Can tokamaks run continuously for years on end or is maintenance a pain? power plants that are in maintenance more than a very low single digit percentage of time are going to be difficult to manage.

Expand full comment

Do you know where I can find the original figure 12? Really want a framed photo of that it looks so cool!!

Expand full comment

true true. i guess i have no idea how fast a tokamak can be turned on/off (or any clue about anything else on this topic really). My impression was that it must take a while to heat stuff up to these extreme temps but maybe not.

Expand full comment
Jun 21, 2022·edited Jun 21, 2022

Eh. Great to see that at least the human race is at least kinda trying at the moment. But still, not a word on how we are actually supposed to extract reliable and safe energy from such a plasma, without the benefit of half a million kilometers of colder matter to shield us from its onslaught. Am I just supposed to fit some radiator tubes inbetween those super magnets? And I can somehow strike a balance between that fluid not becoming super radio active, and my reactor lining vaporizing / transmuting away, and contaminating my plasma?

I genuinely do not know if these are all trivial problems that have been solved 50 years ago; or if we are still so busy actually building plasmas, that we unironically have no idea how to get anything resembling economic utility out of them, once they are humming along. I fear the latter. I mean its easy to talk about breeder blankets and what not; but its another one to actually build one, and run a viable busines using one.

Expand full comment

> 12D +13T 24He +01n .

Seems like the latex got mangled up beyond recognition.

It probably was alike to

_1^2\mathrm{D} +_1^3\mathrm{T} \rightarrow _2^4\mathrm{He} +_0^1\mathrm{n}

https://quicklatex.com/cache3/7f/ql_977960472b50d72ffe1ba3507ad2ab7f_l3.png

Written like it is, it is strictly less helpful than without any numbers whatsoever.

D+T ---> He-4 + n

would be my preferred rendition in a single ascii line.

Expand full comment

How this is a finalist for a book review contest when it barely mentions the book, let alone actually review it, is kind of a mystery to me.

Expand full comment

Do you have a model for thinking about the commercialization of these achievements? E.g. how much will the first generation of power plants cost to build? Will they be able to charge below current natural gas prices? Solar?

Expand full comment

So what you're trying to say is that fusion is 20 years away...

Hah, pull the other one!

Reaching net energy gain isn't the end there will still be a long way to go after that, like sorting out maintenance issues, and trying to bring costs down. I peg it as about 60 years away still and likely only useful beyond the inner planets.

Expand full comment

What I wonder from this post is why not the oil countries are not investing hard in fusion. They will be the ones most impacted by it.

Expand full comment

Any comments on First Light Fusion's "Projectile Based Inertial Confinement" ?

https://firstlightfusion.com

Expand full comment

Since this book review makes some explicit forecasts and this community is in general interested in forecasting: there are a bunch of questions on Metaculus pertaining to fusion. One of them pertains to "fusion ignition" (https://www.metaculus.com/questions/3727/when-will-a-fusion-reactor-reach-ignition/) . Unfortunately, there appears to be no agreement as to what fusion ignition means exactly (cf. my comment in the discussion there). Hence IMO the resolution criteria of the question are not ideal. I have tried my best to bring up some of the issues but I am a total lay person in this area.

It would be great if someone with actual expertise could weigh in there and also on the Wikipedia article (https://en.wikipedia.org/wiki/Fusion_ignition) on fusion ignition so that we can get better forecasts and knowledge dissemination on this topic.

Expand full comment

"Fusion funding is literally peanuts: In 2016, the US spent twice as much on peanut subsidies as on fusion research."

I laughed at this one. Very fresh way of using "literally".

Expand full comment

What do you think of Eric Lerner / Lawrenceville Plasma Physics and their "Focus Fusion" design?

Expand full comment

No mention of Deepmind's recent contribution to plasma contouring! Also its not England, its UK. An American author I would guess.

Expand full comment

Wonder why no mention of the Lawrence Livermore MFTF?

Expand full comment