For April’s Fool Day, you should release an episode of Gobbledygook without the Science.

I almost spat out my Flammkuchen when you said it was named after one of EM's children 🤣...top notch!

09:17 Tokamak Energy, a spherical tokamak ST80 HTS 11:05 Commonwealth Fusion Systems SPARC 12:49 ENN Fusion Technology 13:59 Type One Energy 15:03 Renaissance Fusion 16:13 Helical Fusion, nTtau, Princeton stellarators (psi) 16:28 tae Technologies (tri alpha energy) 19:13 Zap Energy 20:44 MIFTI 20:57 NovaFusion 21:48 first light 23:55 HB11 Energy 24:05 generalfusion 25:20 Helion Energy

Sabine, this is one of your best videos yet, especially for those of us most interested in how physics principles translate into useful applications. Well-researched, balanced, un-hyped, and succinct.

What a star. Sabine manages to provide an excellent overview but in an interesting ,entertaining and actually humorous way. Speaks for 30 mins whilst maintaining one’s interest. Marvellous - love the videos. Thanks.

Thank you Sabine for going over the different reactors, their operating principles, and the companies pursuing them. It was very informative.

I had to be rushed to the emergency department while I was watching this video because your joke about Elons favorite child ST80-HTS had me literally dying. Omg. Dr Hossenfelder, you’re often very funny, but that was solid gold! 🙌 Thank you so much for your detailed and in-depth science videos. I learn so much from you and love your sense of humor. (And I’ll be sending you the bill from my hospital visit as a token of appreciation. 😆)

I currently am doing D-D fusion in my small lab at a Q total of 10e-9 using IECF. It produces enough neutrons to do a number of good activation experiments of several elements. The one thing learned by actually doing fusion by any method is that net power production from fusion is a tough nut to crack. The common man is easily impressed by the press. Sabine is always a voice for reason and logic. This is something rare among people and even many scientists in the fusion biz. Sabine has, for the first time, pulled together the encyclopedia of current startup efforts with significant details around each effort and the fusion fuels used. Finally, I hold out little hope in any current fusion effort such as ITER , a multi-billion dollar debacle, or any of the startups with their ridiculous hyped grid ready fusion promised in the late 20' or the mid 30's. The key to commercial viability is a Q total >20 but with Q total >100 being far more viable with the ability to work 24-7-365 for a number of years as with the current fission, coal, gas and hydro plants. Oddly, this continuous expectation of energy from our wall outlets has persisted as a mindset for over a century now.

My three takeaways from this video about fusion: 1. Wow. I too am now actually optimistic. 2. Sabine is an international treasue. 3. I need to do more with my life. Absolutely inspiring human ingenuity and effort. Incredible.

Thanks for reuploading with the corrections! Great overview on the subject. Exciting times lie ahead :)

My favorite is General Fusion. The rotating shell of molten lithium and lead absorbs radiation which protects the reactor and provides a way to extract the heat. Bombarding the lithium with neutrons produces tritium which is needed to fuel the reactor. A demonstration plant at 70% scale is scheduled to start operation at Oxford in the next couple of years.

Thank you for a really interesting and useful video! I love how you just explain things without attempting to make everything "fun" like many of the older science channels on KZfaq. You do have a sense of humor but it doesn't get in the way of explaining the science. That approach is very much appreciated.

Great sight gag with the duct tape and the WD40 at 1:46: if something's moving and you don't want it to, duct tape; if it's not moving and you want it to, WD40. Together they can fix anything.

"I came out of doing this video being more optimistic about nuclear fusion than before. It seems likely to me that at least one of these approaches should work out in the end, though I haven't been able to make up my mind which one's the most promising." Given your usual scepticism towards all things, these two sentences actually fill me with great hope for the future.

6:00 I've never came across such a compelling explanation of inertia before-well done! 👍

I wonder if the reason fusion gets all the love is because it's not yet regulated like fission. You can make a pretty good pitch if you assume a best-case-scenario for your own technology's regulatory framework, while comparing it to the current highly-outmoded regulatory framework of your competition.

Thank you, Dr. Hossenfelder, for this brilliant review of fusion and fusion startup companies. Without question the most informative and interesting half hour I've spent this year, and for some time before that. Just. Excellent.

You can call it Nova Fusion if you want to. Trademarks like that are product/industry specific. As long as you aren't planning to market the output electric charge as a hair volumizer, you are probably fine. 😜

What an amazing overview, extremely well documented and precise! I personally believe that tokamaks and stellarators are in a more advanced status than the other approaches pursued by those private companies, but I am looking forward to seeing the progress also in those other directions. The more, the better at this point, and maybe the best approach to fusion energy is still to be found.

Sabine you're the absolute empress of deadpan humor :)) Love all these amazing ideas - so cool!

Brilliant overview and summary, Sabine! I find it amusing that two of the approaches involve respectively gunpowder and steam pistons. Steampunk fusion 😂

Others would tingle around making money as "investment consultants" showing around those results on flip charts to investment bankers. So thanks Sabine for the hard work putting all these together into a video and give it away for free.

I'm new to the channel and I'm amazed of how well explained is the information. Thank you so much, Sabine! I love your style!

Well done, Sabine. I didn't know there were so many start-ups. Still, Solar Panels make electrons straight away, which is what you want, and wind gives a lot of energy at might. I live in California, and the panels on my roof, pay for both our electric cars and our electricity bill is close to zero. Seems easier than all this fusion-shmusion

I'm hopeful Helion's approach with direct electrical conversion works. If they're able to avoid a steam generation cycle entirely that will be is own breakthrough!

LOVE the graphic for "the engineering part". Absolutely the truth.

That is the best and most comprehensive video I've seen about Nuclear Fusion. I've learned more about the various approaches to fusion in this one video, than I have in dozens of others. What a shame Tokamak Energy doesn't call their device "Peter". 😎 Thanks Sabine.

I just love the conciseness of this video! Very informative!

You left out the big problem with inertial confinement: repetition rate. To actually get net energy out, rep rates of 100-1000 Hz or higher will be required, which rules out NIF as ever generating net energy. BTW, I did DD fusion in a pulse-powered Z-pinch back in the 80’s, but suffers from the rep rate problem.

Thanks for the great video! I'd previously only known about a few of these companies. I love how you pointed out the upsides of each approach as well as factors that make that approach more of a challenge.

What an interesting presentation. I thoroughly enjoy the format and approach that Sabine takes for some of the most important issues of our time.

Great overview, thanks. I love Helion's concept for direct electricity generation from the expansion of the plasma in the magnetic field. It's way past time the human race moved beyond heating water into steam to turn a turbine to generate electricity. That's so primitive. Hope Helion's design works.

You had me laughing so hard with the Elon Musk kids name joke xD

Thanks Sabine. For little reactors, the thermal and magnetic gradients are mind bogglng. For big reactors the size and cost are mind bogglng.

Thank you for this lovely summary 🙌 I was familiar with some of the concepts, but WOW, so many more than the two previous main contenders

This is an excellent video, I haven't seen any other video yet that have actually done a detailed overview of most of the fusion designs that companies are pursuing.

I don't know, between fuel scarcity, durability and general net-gain issues (all of them being frankly understatements on my part), I still remain rather skeptical that we will see a comerically viable fusion reactor any time soon.

You always make the seemingly impossible to understand digestible to people like myself. Thank you for all your videos, they must take a considerable amount of time and effort. I'm really glad I found your channel, you're wonderful.

SPARC is a partial acronym. Dennis Whyte explains it in his Lex Fridman appearance. ARC (Affordable, Robust, Compact) is the eventual end-to-end pilot plant they plan on making eventually. SPARC is a component of it, and is the actual tokamak. It's named SPARC as a play on words, because it's the thing that 'sparks' the fusion reaction.

It's one of the best channels on KZfaq. I am always captivated with each video, and I end up watching till the very end.

Thanks Sabine for the work to assemble all the informations about all these startups, and presenting clearly which technique they intend to use. Great job !

You know at first I watched a few random videos back in the day of yours that were interesting then you starts producing regular ones and they weren’t great. But I stuck with it and you have really hit your stride. Your content is both informative and interesting enough for an adhd brain to hold. I want to say keep it up and I appreciate how far you’ve come. Working at a boring job where I dont learn I really like your stuff now

I am deeply fascinated by this type of research. Thank you for the deep dive into the different approaches of these various companies to solve the same problem.

I actually like Helion. One of their ideas is to have two separate reactor setups. One will produce Helium 3 exclusively. The other will be used for power production. If the video on them by Real Engineering is accurate, they're already making repeatable, reliable fusion reactions.

Thank you, Dr. Hossenfelder. Bringing many alternatives into one review is useful and valuable. I hope you release an update to this every year for the remainder of this decade. We need to see trends. It'll be interesting to see if privately funded fusion is always 7 years away after 7 years; more than 4x 'better' than existing fusion research. 🤔 Best Wishes. ☮

Oh yay! Watched the previous upload and gonna watch this one too. Can't ever have too much Sabine in your life right? 😝

Excellent Sabine for giving ur valuable information on such a crucial topic

It's not a startup, but Lockheed's Skunkworks department has been working on small, 'portable' fusion reactors for a long time and have an interesting design. As a continuation of this episode it might be interesting to talk about the non-startup organizations working on fusion.

I've been intrigued by Helion for awhile now, and I was happy to see they made Sabine's list. I just wish she'd spent a bit more time on them, perhaps explaining why she's skeptical about their timetable. Overall great video, and I'm also very enthusiastic about the future of this technology.

I like that Helion produces electricity directly rather than having to spin a big turbine. If it works, then that seems like it would be a huge boost in efficiency.

Wonderful summary, thanks Sabine!

Good summary. Note: Among other problems mentioned, Helion's "push back back on the mag field => direct electrical capture" implies some pretty severe Electrical Engineering challenges. They are apparently already building their own special purpose capacitor factory...

Most likely, Big Friendly Gun is a reference to the weapon BFG in several video games but specifically Doom and Quake. Clearly that's not what the acronym meant originally. :)

Excellent breakdown. I had the pleasure of attending a seminar hosted by General Fusion back in 2012 at UBC, and back then they were looking at using explosives to simulate the compressive force of the pistons - explosives being easier to time in perfect sequence than pistons. They were also trying to work out the Deuterium-Deuterium reaction as their primary fusion force at the time, since Tritium is fairly hard to come by unless you're the Japanese government. (If you don't get that reference, Fukushima has a bunch of tritium-laced water in storage tanks, as a result of the cleanup efforts, and unfortunately all the fusion research in the world is not enough to use it up faster than it's being collected, leading to some controversy over storage problems.)

this was phenomenal. i have watched several videos from several channels on the future of fusion and i never felt i was getting a reliable comment about any of them; now, for the first time, i do. i think the biggest advantage you have over those other numerous channels that i tried for news about energy, physics and engineering is that you are: 1. most maximally educated on the topics 2. reliable the first one is obvious but the second one comes as a surprise to me. don't get me wrong, i am not offending you; i mean literally any channel that i have watched during the years starts as reliable and objective but then you can see the patterns of bending the truth to promote or demote something. either to attract more clicks or to compensate for a compensation ;). that is not the case with you. i think it is because of your highly developed and vast personality. i hereby thank you and have a suggestion for the future videos: you are exceptionally fit to talk about the critical topics related to physics, technology and engineering out there. people like me are in need of a person like you to comment on these topics. i believe if a person really understands something, they can talk about it in simple terms and even make a couple of jokes about it on the way. on many channels, you can see several layers of work: first they try to get their facts right, then they try to make it simpler and then they try to integrate jokes and humor into it. the results are at best disoriented. sentences that contradict each other and humor that point to unrelated directions. you on the other hand, are like a poet: even the single words are speaking. so in essence, maybe if you are willing to, you can add a new playlist to your channel to freely comment on critical and new engineering and tech news and ideas. the problem with being really powerful is that you can't see you power, others can. i can only imaging that if you just make free comments on cellphone batteries (without doing any additional research) how beautiful and attractive that could be to the youtube community. to summarize: i think this video is phenomenal because you are freely giving us you opinions on a matter. i think you are at a level of intellect that can actually help the world with that. if 99.9999 percent of people start to give their opinion on some matter of science or technology without doing any research, they would give you their integrated compensations for not knowing the reality. you on the other hand are completely different, you can give your opinion freely and it will integrate all the knowledge there is. a scientist, an artist and a sorceror in one.

Sabine...you are such a legend! Absolutely love your extensive knowledge and brilliant commentary, but your awesome German dry wit is what keeps me coming back 😂. Love your work, keep being awesome! 🫡 Vielen Dank und viel Respekt aus Kanada 🙏

Personally I think if general fusion gets their design working it'll be ahead of the competition in terms of application, the construction of it is significantly simpler than most designs, integrates sheilding, intwgrates energy capture, integrates lithium breeding, and they've been billing it as capable of being connected to existing turbines (which makes its small size critical as it can actually fit in an existing structure unlike a tokomak). Ultimately continuous large scale plasma vessels like tokomaks and stellerators are the end goal, but I seriously doubt they'll be in the market any time soon, and certainly not soon enough.

They should use the idea of cavitation bubbles which heat up to extreme temperatures using water for ignition. Instead of trying to use hard to make or find matter, they should use water.

Very insightful. Love the dry humour too.

Kudos to Sabina, love the humour as much as the information

Great video on an important subject, Sabine. Thank you. It may be a long shot, but I'm rooting for Helion because of the way they are extracting power from the reaction.

Many thanks for the work collecting all this info together. A great summary, thanks, Sabine. One maybe to add next time is LPPFusion - who are still trying to solve the reasons why Dense Plasma Focus doesn't scale. To be fair to them, they have made progress from the disappointments of this approach in the 1960s and they now have one of the highest wall plug efficiencies of the privately funded efforts. Proceed on all fronts!

Excellent summary. Thank you for all the work it took to do this. I was recently wondering how this technology was coming along; thanks.

In 1967, when I was in college, I did a paper on articles about "Magentohydrodynamitic generators" , my spelling may be off a bit, but I have been waiting for seeing something work before I pass from this world, I remember a couple of companies were doing this, one of them was Allis-Chalmers, another was either Westinghouse or GE, maybe both. Interesting report Sabine.

Uploaded again, you're the best. And suggestions for new episodes: 1. Quantum ZENO effect 2. Weak young sun paradox. Thank you

I like the Ductape+WD40 engineering approach. That will do it!

This is fantastic, well delivered, well informed and well funny. More please

Great presentation as always. From what you said, I still believe commercially viable Nuclear Fusion remains 30+ years away!

I like the big friendly gun. Everyone is thinking of all these advanced techniques and they are like, 'lets shoot it with a gun'. It is actually inspiring how many different and creative ways people have come up with to approach this.

I was hoping to see Sabine's take on Focus Fusion (LPP Fusion). I did see her take on a company doing a deuterium / boron reaction, but I don't think its the same company. Not a shill for them, just looking to get a 2nd opinion other than their own.

Brilliant,, articulate and dry humorist all rolled into one!! Rare combination and much admired by me. Thanks for your many interesting videos 🌹😘

Another great summary of a complicated science and engineering topic in a way understandable at several levels.

Incredibly informative. Just putting all these things side by side is a huge advance for transparency. I wonder. I have long felt First Light's is the simplest approach of all and is going to win this. It reduces fusion to a repeatable, entirely mechanical process. None of the others, including the "mixed" confinement ones, are as simple. Removing complexity seems to me the first order problem here.

I watched a video on Helion's approach a couple of months ago and thought it was most interesting, particularly the idea of generating electricity directly. However I have no really in-depth knowledge of the particulars of all these approaches beyond a broad understanding of what each is trying to accomplish. I do think with so many people and companies throwing the book at the problem something has to come out of it at some stage. I am wondering whether I will be around to see one of them triumph as I'm kind of living on borrowed time. One thing I do hope is that there might be some collaboration between the groups of scientist which could yield a result with a synergetic mix of ideas - it would get in the way of competition but might be a win-win. Thankyou for such a comprehensive overview of what is currently going on in the field. A most riveting talk!

Thanks for the comprehensive review. It is good to know so many different types of fusion types being tested by various startups around the world -- I only know Tokomak before watching this video.

Great video, very informational, thank you!

That's quite an array of new fusion projects. Interesting to hear about this. You should do a video on the "safire sun" reactor thing. It looked a bit like a scam that needs debunking but I'm not qualified so I don't know for sure. And I haven't seen much reaction about it. Maybe that's a sign. 😅

Very well done! At the beginning, I wondered if you would mention two companies I have been watching for some time. Yes, you mentioned them both, General Fusion and Helion. :) Your explanations were also very well done. For the short time you spend on each (which I know is the purpose of the video - to introduce your watchers) your explanations are well-balanced; not too much and enough to help us understand the differences. Thanks!! I love your videos. :)

Thank you very much for this, really interesting video!

I can't wait to see your next video on the current breakthrough in fusion. This is amazing. ;)

Thank for the awesome review, the amount of work needed to make a video like this is unbelievable I suppose. (Did anyone make the astonishing sum of the fundings of all these projects together? I'm glad for the employees anyway.) As for the perspective, well, if one asked 30 years ago "how long does it take to see a viable commercial reactor", the answer was always "30 years". Now, skipping what the researchers boast, a sensible answer appears to be the same "30 years". (So I'll never see it happen, but maybe a solid progress in my knowledge is already achieved : number "30" is kind of magic).

As always, thank you for doing this. Would you consider looking at the feasibility of their claims? These companies say that can get it working by such and such date, but it might be good content to go over what they're using in these projections. I bet you'd get a lot of business interested views looking for someone to digest the technical projections.

When it came to the startup name ChatGPT found, I initially understood "nowhere fusion" and thought it was totally apt. I'd really love to see fusion happen with proper output, but after watching I came out more sceptical than before. - Very cool overview video.

A very interesting overview, thanks Sabine. I had somehow not heard of the z-pinch technique before but it definitely seems like a promising avenue for exploration. Exciting stuff.

Like others, eg. New Energy Times, Sabine recognises the different uses of Q - we can call them Qplasma and Qmachine. To put fusion experiments into context, the recent record-breaking JET run had Qp of 1 and Qm of 1%. For a commercial device, we need Qm of about 30. Thus we need a factor of 3000 increase over the JET result. Even with the 30 figure, the electricity production will be one third of this, giving an effective Q of 10. Draw your own conclusions.

I really enjoyed this video and many of the other videos on this channel. As a mechanical engineering professor in the Seattle area, I do have one little niggle. I've toured and met with the CEOs of both Zap Energy and Helion Energy. Both companies are technically in Everett Washington, about 20 miles north of Seattle. Its a distinction only someone in the Seattle area would care about. (But people from Everett care about a lot) 🙂

Vacuum -> Fuel -> Detonation -> Containment -> Reaction Mass Syphoning. Repeat. Using fusion reactors for generating electricity is only 1% of what they could do.

Thank you for the summary ❤

I watched this episode already. When I was done, KZfaq told me it didn't exist and I was plunged into an existential crisis. I'm going to invent a machine that makes it so that whenever the Police measure my car's velocity, they won't know where it is.

For any DT reactor, you need to ask: "what is the volumetric power density of your reactor (and not just the volume of the plasma)". You will find that this figure is MUCH lower than the volumetric power density of a fission reactor (for a commercial PWR, this is roughly 20 MW/m^3.) After that, ask how their fusion reactor is going to produce heat more cheaply than a fission reactor would, if it's going to be so much larger and more complicated. If they can't answer these questions convincingly, be very skeptical. IMO, Helion's approach is the most promising, as it evades this comparison with fission, as it's directly producing electrical energy, not producing heat that is to be converted to electrical power via a thermal cycle (as in DT fusion and fission). Also, the neutrons from DD fusion are much less damaging that the ones from DT, since they are of lower energy, below the threshold for (n,2n) reactions in most materials, and also having much lower cross section for the very nasty (n,alpha) reactions, which limit the lifespan of exposed materials (the helium builds up and forms high pressure microbubbles that rip the material apart.)

Great video. 😊 Love the deadpan humor.

👍 Excellent summary! I like general fusion because it addresses neutron radiation up front.

The older I get the more sceptical I get about Fusion technology. I am convinced there will be children born today who reach my current age of 40 and will still be waiting for it to happen. I'm more interested in the enormous fusion reactor which crosses the sky for all of us on a daily basis- seems like a pretty convenient energy source if we learn how to store it properly.

People go crazy about fusion, but it is much more difficult to achieve then they imagine. A better and more achievable power source is a Liquid Fluoride Thorium Reactor. Why no one speaks about them? They are near perfect solution to current problems of the world!

Hi Sabine, There is a small American company called LPP Fusion whosw approach is differnt again. They aim to use Hydrogen and Boron and feed firectly into the grid, They have achieved the required temperature in a small reactor but fall short on confinement and density but not that far away, They call their approach Focus Fusion which does not require a Tokamak because they encourage the natural instability of the plasma to assist with the fusion prossess. They require more funding and at present are a small private company. Their founder is Eric Lerner who is excited about Nuclear Fusion and feels commercial generation is not far away. I enjoy your Yotunes immensely. Best wishes Edwin Rigg

I remember reading about the promise of Nuclear Fusion, in the 1960's. And it has an earlier history. Many billions of dollars have been spent trying to make it happen. At first countries had programs, now the private sector is giving it a go. These has been some meager success.

Brilliantes Englisch, geballtes Wissen, Begeisterung und ein starker Auftritt! Tolles Format, freue mich auf mehr!😋

I've been hopeful in the past about fusion but I learned from watching experts in the field here on yt that most of these startups stay quiet about their unsolved problems. Also, proving fusion and claimed characteristics of the achieved reaction is well-established in peer-reviewed science but very lacking among these startups so I would take their claims of confinement time, temperature, and net gain with a grain of salt.

A part from the video itself, which is excellent, I much appreciate the clarification about when to say "torus" instead of "donut".

Thank you for all your research!