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A Commercial Path to Fusion

physicsworld.com

142 points_bpgl105 comments

This is R&D - not a commercial path.

These types of fusion projects are trying to prove the most basic piece of the puzzle: net energy generation. And it is a big problem, even for Commonwealth. I've heard that the magnets are underperforming by about a factor of 2 - and that's 4 years into the project.

But commercialization is a lot more than just proving that the concept is physically possible. It was proven possible that man could walk on the moon, but it's not a commercial activity 50 years in. Commercialization for nuclear energy systems means global deployment, mass manufacturing, lack of proliferation risk, extreme safety, etc. Fusion systems like Commonwealth's do not meet any of these criteria. They are constantly generating radioactive waste because they have to breed their fuel and reprocess it on site.

To commercialize, you have to be able to deploy the technology in a significantly better way than traditional fission. These large fusion prototypes ($65B for ITER and $5B for Commonwealth based on their 2015 white paper, so probably 2-4x larger now) exacerbate traditional nuclear's cost problems because they are construction projects that will last decades. Viable nuclear solutions will be factory manufactured rather than constructed.

For comments from MIT dissenter in 80s that stand true today: http://orcutt.net/weblog/wp-content/uploads/2015/08/The-Trou...

For a review of fusion problems: https://thebulletin.org/2018/02/iter-is-a-showcase-for-the-d...

I'm a little dismayed that your first link is, as you note, from the 80s, and that your second link is about ITER, another old design that is orders of magnitude larger than the scheme in the article, a size it must have due to the very same technical limitation that the subjects of the article are working to remove.

But that is hardly the only disappointing thing about your post; It's just fear-mongering. Of course a development reactor isn't going to be "manufactured," but "built." What prototype has ever been manufactured before it was proven? One of the very points of fusion is its low proliferation risk. I don't know why you burden fusion with "extreme safety," either. Bicycles don't have "extreme safety," and we seem to do just fine. The impact of a fusion "disaster" is probably much less than a fall off of a bicycle.

Let's just toss out all physics pre 2000 because it's old. lol. Truth doesn't age. Just using ITER as an example. I can update that link with a Commonwealth one in a few years I suppose.

Manufacturability is a function of a lot of things like parts, systems, interactions, size, mass, supply chain, transportability, etc. Generally speaking, more complex things are less manufacturable and they become manufacturable by simplification and reduction. As a kind of measure of manufacturability, look at the cost. Think about the most expensive piece of technology that is mass manufactured today. It's probably the 777 or 737 - so price tag on order <$100M. Big ships are on order $10Ms. Maybe military procurement goes into the $500M, but those are low quantity and generally failed programs.

So if it's more than $100M and much more complicated than a wide body aircraft, today's economy and technology level is probably not going to be able to mass manufacture it.

The size and complexity of these fusion systems is physically constrained by various factors many of which are physics limited. And even with the innovations they propose but have yet to prove out, the size and complexity is still too large to manufacture.

Regarding fusion's proliferation risk: "One of the best ways to produce material for atomic weapons would be to put common, natural uranium or thorium in the blanket of a D-T reactor, where the fusion neu- trons would soon transform it to weapons- grade material. And tritium, an unavoidable product of the reactor; is used in some hydro- gen bombs. In the early years, research on D-T fusion was classified precisely because it would provide a ready source of material for weapons."

The big point Lidsky was making was that, for general reasons, DT fusion reactors will have lousy volumetric power density, compared to fission reactors.

So in addition to the points you make there, let's look at ITER's power density. Dividing the gross fusion power of ITER by the reactor (not plasma) volume, it will be about 0.05 MW/m^3.

In contrast, the power density of a PWR (gross thermal power divided by the volume of the reactor vessel) is about 20 MW/m^3.

ITER is worse by a factor of 400. Lidsky was being generous to fusion reactors, compared to this. MIT's ARC concept is about 0.5 MW/m^3, also much worse.

Lidsky's point is still valid, 35 years later, because it was based on generic arguments. Pfirsch and Schmitter were making basically the same argument in Europe at the time. Had they all been listened to!

MIT us using 8MW/m^3 for DT. Apparently pretty basic physics and it applies over a wide temperature range.

https://www.youtube.com/watch?v=rY6U4wB-oYM&t=335

I believe that is using the volume of the plasma, not of the reactor. If you wish to go there, the power density of a PWR core is 100 MW/m^3.

Yes. The only number I could find for a Uranium PWR core was 69MW/m^3. Lidsky said in 1983 that "the power density is only one-tenth as large" (fusion vs. fission) so I assume this is what he was talking about. I only wanted to compare apples to apples.

Obviously, additional equipment surrounding the core or plasma adds to the volume, but the major portion of the construction cost is the steam equipment and power generators which is the same cost and volume per MW for either technology (or for fossil fuel power plants for that matter.)

The major part of the cost of a fission plant is the non-nuclear part, but I don't think that would be true of a fusion plant.

In any case, if some parts are common, but the non-common parts are cheaper in a fission plant, fusion will be more expensive than fission -- and since fission has already lost in the market due to its cost, fusion would do likewise.

He is pointing out a very important reality though. First you prove physical viability. Then engineering viability. Finally, after operating a full commercial unit for a while, you may prove economic viability. It's easy to assume physical viability leads to economic viability but this really is not the case.

If you can show by general arguments that engineering viability is unlikely, demonstrating physics viability is pointless.

it's a she.

Oh crap. I'm sorry. Thanks for the correction. Too late for it to let me edit.

>I've heard that the magnets are underperforming by about a factor of 2 - and that's 4 years into the project.

Hi - could you pls point me to the source for this? Would be great to see actual data on where we are on these projects. thx

There are no "magnets" at this point, so not sure what he is talking about. Basically they are building up HTS Twisted Stacked-Tape Cables (TSTC) and they plan on building their first full-size prototype coil in 2020.

Current tests include subjecting conductors to a 13T field in a 700mm chamber at the National Institute for Fusion Science (NIFS) in Japan. One of the key properties of HTS is that they maintain superconductivity at high magnetic fields.

Some slides from a recent talk discussing this phase of research: https://indico.cern.ch/event/775529/contributions/3309887/at...

Overheard a wailing researcher at a bar in Boston. Sorry.

gotcha thank you.

yep, at least until we get aneutronic fusion going with direct schema of electricity generation bypassing the heat engines, the fusion on Earth has no chances of competing with the most of the existing and especially solar/wind energy sources. Other than that the 2 most interesting potential applications are weapons and space propulsion. Those applications are better served by inertial confinement (laser, Z-machine, fusor, DPF) which historically been showing better results and usually at much lower costs (and even the high cost NIF can be redone today using modern solid state which would lower the cost/size dramatically) yet historically the resources have been poured into the huge systems like Tokamak.

> yep, at least until we get aneutronic fusion going with direct schema of electricity generation bypassing the heat engines, the fusion on Earth has no chances of competing with the most of the existing and especially solar/wind energy sources.

This sounds like unfounded opinion to me. While I agree that ITER derived designs are unlikely to compete economically, that doesn't prevent alternative designs, especially hybrid fusion/fission sub-critical reactor's, from competing.

For those not familiar, here's the wikipedia page on hybrid fusion-fission [1]. The idea is to use a sub-break-even fusion reactor as a source of very high energy neutrons that would trigger fission in uranium or thorium isotopes that are otherwise non-fissile. For example U-238, which constitutes 99% of all uranium on earth, and which is currently the dead weight as far as uranium is concerned (worse, you spend a lot, a lot of money to separate U-235 from U-238). U-238 can undergo fission when targeted by fast neutrons, but can't sustain a chain-reaction, so fusion-fission hybrid reactors can't lead to a Chernobyl event (but a Fukushima is possible).

Not clear why we don't hear more about fusion-fission hybrids on HN. It sounds like such a promising technology.

[1] https://en.wikipedia.org/wiki/Nuclear_fusion%E2%80%93fission...

Hybrid fission-fusion reactors combine the worst features of both. Why would anyone want one?

If Apollo 11 had found oil on the moon, we would have a few thousand people living there already. There is just nothing profitable in going to the moon.

With fusion the opposite is true: we know energy is precious, and we know its market price. Just prove it can be done and commercialization will happen very quickly.

> If Apollo 11 had found oil on the moon, we would have a few thousand people living there already.

You're forgetting the most important piece of information in the economy: price.

Since oil produced on Earth is cheap, compared with hauling it back from the Moon, we don't get any from the Moon.

Now, if we had found some exotic energy source that didn't exist on Earth at all, that would be a different story.

> Now, if we had found some exotic energy source that didn't exist on Earth at all, that would be a different story.

Which does exist, btw: helium-3 which is deposited by the solar wind and captured in cold traps on the lunar poles. It doesn't exist on Earth in any quantity, except artificially produced in nuclear laboratories. He3 fusion is easier to achieve and less dangerous to operate.

Sounds like an excellent reason to go to the Moon :-)

Unlikely:

"The helium-3 incantation" - http://www.thespacereview.com/article/2834/1

tl;dr the popularity of mine-the-moon-for-he3 meme is due to wishful thinking about sustainable moon colonies, and there's no analysis that suggests it's even remotely practical to do.

That article is bogus. Let's take the outline points:

"There are no fusion reactors."

Well, duh. Fusion power isn't that far off though. Even Lockheed has a self-funded fusion power program being run out of Skunkworks, which isn't known for ivory-tower boondoggles. Even so, part of the point is that He3 fusion is different from D-T fusion, which brings us to...

"Helium-3 fusion is even more difficult than regular fusion."

No, He3 fusion ignition temperatures are higher than D-T fusion. But in every other way aneutronic fusion reactors are easier to build and maintain than neutron-generating D-T. They can be smaller, lighter, generate less radioactive waste, permit more efficient direct electrical current generation, and require simpler electrostatic containment than Tokamak-like designs. You can literally build one in your garage.

"Helium-3 may be very difficult to locate and mine on the Moon"

This was invalidated by LRO's data on the cold traps in permanently shadowed craters on the Moon (and MESSENGER's data on Mercury), which were then validated by simulations of the Moon's exosphere and interaction with the solar wind. The regolith in these craters is as much 40% volatiles by weight, of which a economically extractable fraction is He3 from the solar wind.

The huge point against lunar 3He, even ignoring that it's two orders of magnitude less reactive than DT, is the difficulty of extracting it on the moon.

3He occurs in regolith in concentrations measured in the ppb. Even with beneficiation of fine fractions and efficient recycling of heat from the thermal extraction step, the energy requires are large, a significant fraction of the energy the 3He would produce when fused.

So to power the terrestrial economy with 3He, you need to put a significant fraction of the terrestrial energy output on the moon to get the 3He. Power plants on the moon will be much more expensive than on Earth (because labor, materials, and supply chains will be more expensive there, even with cheap space transport), so this is unlikely to pencil out.

Your information about the composition of the moon is 30 years out of date. He3 would be mined from the cold traps in permanently shadowed craters at the north and south poles of the moon. There it exists in extremely high concentrations, alongside other useful volatiles that together make up 40% of the surface material by weight.

“Refining” is a process as simple as shoveling it into a pressure container, heating it, and then letting dissipatively cool back to ambient temperature, collecting the other volatiles as they condense out. What’s left is a mix of inert gasses, including He3.

There is no data on 3He at the poles. The area there is small anyway.

The concentration of 3He on the moon in general is such that simply heating regolith without heat recycling and separation of fines would use more energy than the 3He would yield if fused.

and build a fusion reactor =D

Which is relatively trivial to do with He3, which is rather the point :)

He3-He3 fusion produces no neutrons, so it requires no mass shielding. The energetic particles that result are electrically charged, so their kinetic energy can be directly turned into electricity, which further adds to efficiencies and avoids all the real engineering problems that come from coupling power generators to the fusion plasma in some way. The ignition temperature for He3 fusion is higher than the traditional D-T fusion, but it's a heck of a lot easier to achieve high temperature containment when you don't have to worry about things like shielding, and that shielding becoming radioactive from neutron bombardment. A great deal of the engineering challenges that plague D-T fusion simply don't show up in He3 fusion.

However the way that you get He3 in large quantities, on Earth, is through D-T fusion. So He3 fusion being easier doesn't help much because to get the fuel you have to do the harder D-T fusion first... unless you go to cold traps on the Moon, or mine the atmosphere of Jupiter/Saturn.

3He-3He fusion is probably impossible. The 3He fusion reactors being talked about would use D-3He, and would still produce neutrons.

The two big issues with neutrons are damage to the reactor structure, and induced radioactivity preventing hands-on maintenance. D-3He could help with the first, but not the second. A D-3He reactor would still have to be maintained remotely, with robots. At best, it would reduce the radiation load on the robots.

The need to maintain fusion reactors with robots reminds me of what they did at the hot cells at Hanford to ensure they could be maintained after being used for reprocessing. They required that the operators install all the equipment there using the remote handling equipment (mechanical waldoes, not robots). I'll believe the fusion people can maintain their reactors when they do the same thing.

Oil on the Moon wouldn't be hauled back to Earth, it would be used for an independent space based industry that produces things that are harder to do on Earth.

Not for energy, it wouldn't - good luck burning anything on the moon!

I was thinking of fancy plastics. Perhaps bring-your-own oxidizer rocket fuel.

Hauling it back from the moon wouldn't be overly expensive. It'd be getting there in the first place that would.

You're missing the point. We know there are asteroids with price changing amounts of precious metals - we aren't mining them.

Commercialization involves so much more than proving it can be done physically. And it also involves more than meeting a price in a padded environment. There are hurdles to jump that are totally disconnected from the price.

> We know there are asteroids with price changing amounts of precious metals - we aren't mining them.

Are there?

As I understand it, the mass of the asteroid belt is primarily confined to just a handful (about 12) of objects, and everything else is so diffuse that it would never be profitable.

I think they are going for the smaller ones anyway, given they are looking to fetch and park them closer for the actual mining. If you are patient and know some orbital mechanics, it takes surprisingly little energy to move stuff around up there. If you can automate it and be sending missions out regularly, sure it takes a while to get your first asteroid back, but after that you can have a steady supply.

Yes, there's a dumb amount of precious metals up there. If you were to bring back the contents of a single asteroid you'd crash the market. Here's a master's thesis on the topic: http://digitool.library.mcgill.ca/R/-?func=dbin-jump-full&am...

Presumably, any public or insider information about a credible funded technologically-sound attempt to mine the asteroid would crash the market first. So, the first sign of such an attempt would be huge shorts in the paper commodity markets by the people funding the mission. They would have to make their money on the financial hedging, not on the actual sale of mined PMs.

Perhaps it also means that Bitcoin has a more credible claim to a limited future supply than traditional PMs with a "proven 5,000 year track record".

Yeah, but if you look at that paper, platinum is extracted at roughly $20,000,000 per tonne--roughly the price of a single rocket launch right now. And we extract only 200 tons per year. That's a $20 billion market, but it's so sensitive to supply that nobody is rushing to open more mines.

> Just prove it can be done and commercialization will happen very quickly.

You seem to be saying "just show Q high enough and we're home free to commercially successful fusion power".

But this is totally wrong. Fusion faces profoundly difficult obstacles to success even after the physics problems have been solved. These may be "mere engineering" problems, but engineering problems are perfectly capable of sinking a technology.

I figure this sci-fi punchline is relevant:

> Rod: Your kind began as self-repairing distributed storage systems for our supercomputers. When the cities fell, some of you survived, and changed just enough to continue to survive and evolve. You are now at least a million generations removed from anything we created.

> Kevyn: You created? You don't mean you personally, do you?

> Rod: Me personally? What do you think I look like? Some kind of an engineer?

> Kevyn: Actually, What I thought was that you looked really, really old.

> Rod: Heh... You youngsters, are always so cute with your little accidental insults. No, I didn't create you. Engineers did. I created something far more powerful... The marketing campaign that made you profitable.

Source: https://www.schlockmercenary.com/2001-12-16

For a breakdown of the reasoning behind the project, if you haven't already seen it:

https://www.youtube.com/watch?v=L0KuAx1COEk

For a layman this was incredibly interesting. The speaker explains the concepts very well.

That video was super informative! Thank you for sharing it

For anyone interested in learning more about the history of fusion power research I would recommend the book: A Piece of the Sun: The Quest for Fusion Energy

I found it informative, and a really easy read to get a good overview of the history of the research.

That's a really good book.

Another one that is also very good is "The Future of Fusion Energy" which has lots on modern methods.

https://www.amazon.com/Future-Fusion-Energy-Jason-Parisi/dp/...

Also well worth checking are the podcasts 'Physical Attraction' which has done many episodes on fusion and 'Omega Tau' that has long episodes on ITER, Wendelstein 7X and superconductors.

Agreed this a great history about how the standard designs came about, particularly the two big ones historically: Tokamak (Soviet approach, mentioned in this article) and Stellarator (US/Princeton approach). Then later in the 1970s ICE using lasers (inertial confinement fusion) which is the other dominant form in modern attempts since Stellarator hasn't worked out.

Reads a bit like those Manhattan Project books.

https://www.amazon.com/Piece-Sun-Quest-Fusion-Energy/dp/B00D...

Approx four or five years ago I had an accidental/random conversation with one of the prominent researchers at the Princeton facility (PPPL). Long to short, he said, "We're getting there. The more funding we have, the sooner we'll get there. But yeah, we're really close."

Mind you, that's what any research scientist would say. But everything I've seen and read since tells me he's was being honest and has been accurate. I hope he's right.

https://www.pppl.gov/

That's really one of my dream: that fusion ends up being up in the corner and suddenly the energy crisis is over.

I too will be happy to see the clean energy problem solved. On the other hand, if big oil - and the countries that depend on it - implodes then we have a new problem. That's not pretty.

I have a good friend who is a physics graduate student at Princeton working on fusion and he has said the same.

I was very close to finishing a 2 week project 6 weeks ago.

He was lying to you, or misleading you. We may be really close to Q>1. That would put fusion where fission was in 1942. It would not mean we were, or ever could be, close to practical fusion power plants.

ITER is 5 years from first plasma and 15 years from full operation.

With all the various experiments over the years, if we haven't gotten ignition by now, we'll never get it. Fusion is going to be perpetually "just 5-10 years away"

https://www.scientificamerican.com/article/worlds-largest-nu...

Stellator didn't work out? What is Wendelstein 7-X then? Christmas lights?

Apologies I didn't phrase that right. There's been more recent work on Stellator. The book takes a longer history look at it and didn't dwell very long on modern developments. Stellator definitely took a decline in popularity at one point before making a bit of a comeback with Wendelstein 7-X and some other places.

Stellarators will have the same low power density of tokamaks. They are not immune to the generic arguments Lidsky, Pfirsch, and Schmitter made against DT fusion reactors.

Inertial confinement fusion was for fusion bomb technology development. It's used to produce bomb-like conditions on a laboratory scale. It was once billed as having something to do with energy production, but that was for PR purposes only.

[citation needed]

It's not hard to find.[1]

[1] https://thebulletin.org/2013/07/nuclear-weapons-the-death-of...

Ok let's agree to disagree with the idea that ICF never had a legitimate energy purpose. Goodbye

What ICF did was play off the weapons and the energy people. When one side raised questions about the validity of the justification for ICF from their side's point of view, the ICF people could just point to the other side.

I think in the end the real justification was maintaining a cadre of physicists who were familiar and experienced with the physics of materials at H-bomb like conditions, in case new generations of bombs needed to be designed, and also to help validate improved computer codes for simulating those conditions without actual bomb tests.

An oldie but a goodie is "Man Made Sun: The Quest for Fusion Power" by T.A. Heppenheimer from 1984 or so.

thanks for the recommendation! In college I took a senior/grad level class on controlled fusion and this was the text book that was used: https://www.amazon.com/Principles-Fusion-Energy-Introduction... (https://classes.cornell.edu/browse/roster/SP18/class/ECE/484...)

The plasma needs to be >=200 million kelvin, the superconductor that contains it doesn't work if its not <=20 kelvin. No wonder this is an engineering nightmare!

I wonder if gradients that extreme exist in nature.

I won't say it's not challenging, but bear in mind that while the plasma is at high temperature, it has very low density. The atoms are moving really fast but there aren't many of them. Consequently the amount of heat is comparable to fossil plants.

The magnets are on the outside of the containment vessel, their whole point is to keep the plasma in the center. What little leaks out ablates the walls of the container, it never even touches the magnets.

How would a commercial venture plan to recoup their investment cost when (if) they finally reach a viable reactor design?

If an American/European company came out with a working reactor, would India and China pay for the technology, or would they put hundreds of billions into developing their own? What about the opposite scenario? Even a tiny peek at the design would shave off a large portion of the cutting edge investment. On the other hand, fusion could completely alter the course of climate change, perhaps it's cheaper in the long run to just give out the technology.

Disney manages to get them to pay for movies enough of the time. Reactors are more difficult to bootleg.

The Omega Tau podcast had some very interesting discussions about various improvements needed for fusions reactors to hit parity in their Wendelstein 7x episode. Some discussions I think come out all the more because the 7x was targeted to plasma research so many practical aspects are discussed outside the normal fusion discussion that hits regular science media.

https://omegataupodcast.net/312-the-wendelstein-7-x-fusion-e...

The SPARC project’s first task, over the next few years, will be to build and test a full-scale prototype HTS fusion magnet. ... one of the primary missions of the prototype HTS coil will be to investigate our ability to detect and mitigate a “quench” event, which is a sudden loss of superconductivity.

Good for a decade of funding and theses before having to actually work on fusion.

This is not a "commercial path to fusion". This is superconducting magnet R&D.

With renewables getting better every day, at what point will they make fusion reactors irrelevant?

Saul Griffith has an old talk entitled "Climate Change Recalculated." The gist is that he converts everyday energy consumption into averaged watts over a day, and then looks at the energy area density of renewables. The resulting picture is rather daunting. If we go 100% renewable--If we even could!--all of our lifestyles would be radically curtailed, and this is after a construction binge of enormous scale.

We absolutely need fission and/or fusion. Of this there is no doubt.

This feels like it fails the sniff test for me. The UK is currently getting about 1/3 of its electricity from renewable sources[0]; my understanding is that variability is the reason it's not getting more, and people seem pretty bullish about improvements in battery tech. Does the UK have such unique geography?

[0] https://smarterbusiness.co.uk/uk-renewable-energy-percentage...

Yeah, that's bullshit. Energy density of renewables doesn't preclude current lifestyles. The Earth is constantly hit by 100,000 TW of sunlight, and the energy collected doesn't have to be used near where the collectors are.

Density in this case referring to "kW per acre of solar panels", and the #s come out to something like covering all of Australia with solar panels, if I remember correctly.

> and the #s come out to something like covering all of Australia with solar panels, if I remember correctly

You do not remember correctly. Estimates seem to vary, but Musk reckons 100 miles by 100 miles for America[0] which I make as 0.003% of Australia. It's a large (if imaginary) place.

[0] https://futurism.com/elon-musk-tells-national-governors-asso...

GP remembers correctly. From http://longnow.org/seminars/02009/jan/16/climate-change-reca... :

> In other words, the land area dedicated to renewable energy (”Renewistan”) would occupy a space about the size of Australia to keep the carbon dioxide level at 450 ppm. To get to Hanson’s goal of 350 ppm of carbon dioxide, fossil fuel burning would have to be cut to ZERO, which means another 3 terawatts would have to come from renewables, expanding the size of Renewistan further by 26 percent.

That confuses primary energy with zero-entropy energy (work). One does not replace a gigajoule of coal with a gigajoule of electrical energy. It also is talking about biomass, which is very land inefficient.

So, basically, the source you are pointing to is obviously flawed and should be ignored.

They become irrelevant as soon as massive energy storage becomes cheap. But as it stands now, fusion seems more realistic than cheap energy storage. But who knows what people come up with.

Cheap energy storage is far more realistic than fusion. I'm amazed you could think otherwise. Simply extrapolating cost reductions of Li-ion cells down their experience curve gives cheap storage, and there are hundreds of alternative chemistries and technologies that could also work, and that can be demonstrated more cheaply than any fusion reactor.

FWIW, Dr. Robert Bussard claimed in 2006 that the inertial electrostatic confinement fusor could be developed for ~$200M IIRC

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

"Should Google Go Nuclear? Clean, cheap, nuclear power (no, really)" https://www.youtube.com/watch?v=rk6z1vP4Eo8

I wouldn't believe that for a moment, and Google probably didn't either.

It's interesting how the internet enables wishful thinking like this. You'd have thought the dearth of peer reviewed papers about Polywell would have been a clue, but true believers admit no impediment to their belief.

There are good theoretical reasons to believe IEC fusion cannot work on advanced fuels, reasons that HAVE appeared in the peer reviewed literature.

Absence of evidence is not evidence of absence. Would it be so terrible to do a little more research? If only to honor Dr Bussard's (RIP) memory? Google's not hurting for cash right now?

"When a physicist tells you something is possible you should believe him, when a physicist tells you something is impossible you should doubt him."

I forget who said that, but it holds. Lots of things had "good theoretical reasons" for not working until someone figured out how. Planes? Visiting the Moon?

Absence of evidence is evidence of shenanigans.

If someone is making a claim, especially a remarkable claim, it is their responsibility to provide evidence for their claim. If they cannot, or if their evidence is such that it cannot pass peer review, something stinks, and one should be highly skeptical.

This is not a case of "no one has shown X, therefore X should be dismissed". It's "P has claimed X, but has not shown evidence to justify their claim, therefore their claim should not be believed." If someone holds a position, presumably they had a good reason to do that, and one can ask for that reasoning and evidence (and ask that that reasoning and evidence be verified by peer review.)

Dude, Dr. Bussard died not long after the video I linked to, so maybe you don't realize you're kind of disparaging a man who's no longer here to defend himself.

In any event, I didn't mean to upset you. I'm not a physicist, nor some sort of "true believer", I just think Dr. Bussard's ideas deserve more research before we can rule them out so definitively. Maybe I'm a gullible dufus. On the Internet.

SPARC is an HTS experiment, showing the viability of compact Q>1 using the technology, showing you don't have to be ITER -size to have successful fusion. It doesn't claim to be and won't be much more than that. An important step, nonetheless.

What I find particularly troubling about the design of tokamak reactors is that on one hand you have magnets that need to be cooled to -250C or whatever the “high” temperature is nowadays and in the middle of it you have plasma that will leak thermal radiation in any way possible. The magnets themselves will heat up from running large electric currents through them. This just feels like a recipe for a disaster - if things suddenly stop working, due to heat or otherwise you have a very hot, radioactive plasma trying to equalise its energy with the outer world...

Well, there's kind of a chain of intuitions here that are off by up to orders of magnitude. First, YBCO has a critical temperature of 93K, not 23K or so as you've suggested (albeit not as a value for YBCO). In other words, there have been advances in high temperature superconductors. Second, the magnets will not heat up from having large currents running through them. This is the point of superconductors. So, this estimate of resistivity is high by several orders of magnitude. Third, any estimate of the total energy of the hot plasma that gets us anywhere near verbiage hinting at explosions is too high by several orders of magnitude. You could typically extinguish a burning plasma by blowing gently on it. Finally, the thermal gradients aren't nearly so dire as, you know, 200e6K immediately next to 90K. There is typically over a meter of, in order: near-vacuum; inner wall; flowing lithium blanket; outer wall; and liquid nitrogen or other cryogenic coolant, all between the plasma and the magnets.

This is the farthest thing from a recipe for disaster.

Just want to point out that specific critical temperature varies with magnetic field. The article mentions 12T and 20K so presumably that is within some reasonable safety margin of the limit for YBCO at that field strength.

Don't fusion reactors have problems with vessel degradation from fast neutrons turning the reactors themselves into radioactive waste?

LFTR is what fusion should have been, and should have gotten equivalent funding. Plentiful fuel (thorium), can "burn" current nuclear waste as fuel, meltdown safe, etc etc etc. And they can scale down to pretty small sizes, per another commenter's "construction" vs "factory production" comment.

The only interesting fusion idea I've seen is antimatter catalyze fusion rockets for space travel.

Wind/Solar/Storage have won. This would be wasted money.

> Don't fusion reactors have problems with vessel degradation from fast neutrons turning the reactors themselves into radioactive waste?

Yea and no. More neutrons per joule of output, but the waste is short-lived and easier to manage.

But also the neutron flux is so large that every atom will get knocked out of its lattice over the reactor lifetime, so the metallurgy is (I’m told by a metallurgist) complicated.

The most serious problem with fusion, though, is that coolant does not circulate through the reactor, but rather around it. This makes fusion reactors have much lower power density than fission reactors.

The first steam engines had problems with leaking steam - this problem was solved, and then we had the industrial revolution.

Identifying problems that don't happen to have current solutions, and then suggesting other people not spend their time or resources trying to solve them, sounds like you have an agenda.

Fusion isn't even economically viable, and can't be allegedly made viable without multibillion dollar projects with high probability and history of boondoggle status?

Come on.

Steam engines clearly produced power at a huge economic benefit.

LFTR also has this characteristic, and also needs vessel engineering to become profitable and usable.

Fusion has dubious net power benefits, dubious profitability even with net-energy experimental status.

And all of that is wasted funding, that should go into battery, solar, wind, electrical transmission, and other storage means, which are beating coal (thankfully) and will hopefully beat natural gas soon.

At the rate renewables are dropping in price, fusion will NEVER CATCH UP. It's not even a matter of the old "twenty years" joke. It's not going to catch up. Ok, maybe in a hundred years when the main research curve on those has finally petered out.

If we're still here.

You seem intent to couch your armchair predictions as ineluctable.

Sticking with the steam engine comparison it was 320 years ago that we had the first proper steam engine (arguably some variety existed ~2 millennia ago, but that'd just support my argument even more).

It took 70 years, though, before we had a decent one (Watt's). And that was before anyone had worked out how to bore accurate holes in cast iron -- so even that was version was a bit clunky.

In contrast it's less than a hundred that we've even just known about neutrons, and the complexity delta between boiling water and fusion reactors suggests that we (you) should not assume that if we haven't solved all the problems around them yet, then we never can or will.

Statements like this:

> Steam engines clearly produced power at a huge economic benefit.

invite questions as to why we hadn't been doing this for thousands of years.

Everything is clear in hindsight.

> And all of that is wasted funding, that should go into battery, solar, wind, electrical transmission, and other storage means, which are beating coal (thankfully) and will hopefully beat natural gas soon.

How society expends its resources isn't a consensus arrangement - sometimes very frustrating, other times it works out well.

Fusion research has a huge positive benefit if / when we get it to work. It's also probably going to be very important for the initial extra-solar expeditions. Doubtless there'll be other, currently unknown, benefits that come out of fusion-related research.

Multiple billions of dollars that you are cashing in _right now_ as inevitably hugely positive and beneficial.

As if the alternative investment of those limited funds wouldn't be MORE beneficial pushing the envelope of storage/solar/transmission/EV/battery research.

It's clear you're a fusion researcher, thus the only guaranteed benefits is your bottom line and continued ability to work in your desired field and specialty.

I am not a researcher, I'm just a generally frightened environmentalist, and my opinion is that this is a boondoggle that can wait for when lower scale pure research has produced a more clear path, and when bigger problems have been solved.

Luckily for you, I have zero input into budgeting and policy.

Not, in fact, a fusion researcher.

But happy that other people are.

Putting all the eggs in one basket doesn't sound like a recipe for success.

If they have won why do they not power most of the grid?

Inertia. If I remember right, if you look at how the distribution of new power sources rather than existing ones, more than half of new power is renewable.

Because renewables have improved on a timescale short compared to the design lifetime of typical generating equipment. This is an unusual situation in the power business, and it means much of the installed base is zombie tech, obsolete stuff that wouldn't be used if the cost weren't sunk.

Within America, at least, there are still quite heavy subsidies to fossil fuels companies to keep them competitive and keep jobs local - their survival is partially due to some heavy market manipulation by the government.

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