4 ms·

> I find it fascinating (and a bit worrying) they are still basically attempting to optimize the same two approaches that were developed in the 50s/60s, tokamak

> I find it fascinating (and a bit worrying) they are still basically attempting to optimize the same two approaches that were developed in the 50s/60s, tokamak and stellarator. This would be a bit like worrying that aerospace engineers are still optimizing wings. Like wings, tokomaks/stellarators are the best tools for the job, as dictated by the underlying physics of the systems in question. Basically, donut-shaped magnetically-confined plasmas "leak" into themselves, rather than out into the world. > Many people have spent their whole careers on it and have died without making significant progress. This is a popular view that is entirely wrong. The figure of merit, which is the triple product of confinement time, density, and temperature, outpaced Moore's law right up until a gain of about 0.95, when the magnetic technology of the day caused the necessary size increase to put ITER in the realm of international cooperation. ITER absolutely will produce more power than it consumes. The plasma physics are just that well understood. The problem is size. MIT have recently worked out that a new breed of superconducting magnets can more than double the available field strength, resulting in a 16-fold reduction in reactor size (due to a 4th power gain in confinement strength as a function of field strength). They hope to achieve a gain of about 2 with a university-scale reactor before ITER, designed with the magnets available at the time, is complete. Most, if not all, of the above comes from https://www.youtube.com/watch?v=L0KuAx1COEk https://www.youtube.com/watch?v=L0KuAx1COEk. ARC and SPARC, the MIT reactor concepts, are the most exciting thing I've heard about in...gosh, I guess my whole life. They could pull it off. If they do, we could save the planet with fusion-powered CO2 scrubbing. We could avert disaster.

lwlml 9y ago
You know, I had a sad thought about fusion-powered CO_2 and that was once it will be built, the energy is likely to be used not for CO_2 scrubbing but instead to mine Bitcoin.
- flashman 9y ago
  "Cheap energy means cheap air conditioning. We don't have to change a thing!"
  - tomaskafka 9y ago
    That's how it worked ever since, including coal and oil. https://en.m.wikipedia.org/wiki/Jevons_paradox https://en.m.wikipedia.org/wiki/Jevons_paradox
dmix 9y ago
That's interesting, I wish I ended the book with that type of optimism. It was a bit disheartening to hear about the many failed starts and the slow down of progress. But that said it wasn't totally lacking optimism. It was more of the hard reality of how challenging the problem will be to solve. I still follow the development of it and there is definitely incremental progress. Thanks for think about MIT's work, that's interesting.
dredmorbius 9y ago
Wings work for what we want them to do, and have since they were first tried. Stellarators don't. Progress has been minimal. The more so if one recognises the distinction between Texas Sharpshooting -- drawing targets around the holes we've made with various technical methods -- and the actual initial intent. This particular problem has turned out to be vastly more difficult than anticipated or advertised. I've watched what little progress has been made over more than 40 years.
- alimw 9y ago
  > Wings work for what we want them to do, and have since they were first tried. Pretty sure people have been messing with wings for centuries longer than they have worked.
  - dredmorbius 9y ago
    What held aircraft back was prime movers, fuel, and materials. Once petrol-fueled engines and aluminium were available, the Wright beothers were flying within a few years of the Ford Model T. Monocoque airframes followed another few years later. The most perfect aircraft ever, the DC-3, which remains in active commercial use, was developed within the next 3 decades, largely thanks to aluminium alloys. Aivionics and wing design were largely solved by then. With the gas turbine, jet aircraft appeared, and Boeing is still effectively building and selling scaled-up versions of its 707 airframe (1957). The USAF will be flying the very same aircraft for over 80 years, the B-52. First flight 1952, last date af manufature: 1962. What progress has been made in aircraft over the last 65 years is largely limited to improved controls (both linkages and avionics), novel materials, and more recently, improved modeling duringg design and development. Outside military applications, that still has exceptionaally limited commercial impacts. See various sources, though Robert Gordon's The Rise and Fall of American Growth has a good overview. The contrast, particularly with man-years of effort and billions in spending, to fusion, couldn't be starker.

lwlml 9y ago

You know, I had a sad thought about fusion-powered CO_2 and that was once it will be built, the energy is likely to be used not for CO_2 scrubbing but instead to mine Bitcoin.

flashman 9y ago
"Cheap energy means cheap air conditioning. We don't have to change a thing!"
- tomaskafka 9y ago
  That's how it worked ever since, including coal and oil. https://en.m.wikipedia.org/wiki/Jevons_paradox https://en.m.wikipedia.org/wiki/Jevons_paradox

dmix 9y ago

That's interesting, I wish I ended the book with that type of optimism. It was a bit disheartening to hear about the many failed starts and the slow down of progress. But that said it wasn't totally lacking optimism. It was more of the hard reality of how challenging the problem will be to solve. I still follow the development of it and there is definitely incremental progress. Thanks for think about MIT's work, that's interesting.

dredmorbius 9y ago

Wings work for what we want them to do, and have since they were first tried. Stellarators don't. Progress has been minimal. The more so if one recognises the distinction between Texas Sharpshooting -- drawing targets around the holes we've made with various technical methods -- and the actual initial intent. This particular problem has turned out to be vastly more difficult than anticipated or advertised. I've watched what little progress has been made over more than 40 years.

alimw 9y ago
> Wings work for what we want them to do, and have since they were first tried. Pretty sure people have been messing with wings for centuries longer than they have worked.
- dredmorbius 9y ago
  What held aircraft back was prime movers, fuel, and materials. Once petrol-fueled engines and aluminium were available, the Wright beothers were flying within a few years of the Ford Model T. Monocoque airframes followed another few years later. The most perfect aircraft ever, the DC-3, which remains in active commercial use, was developed within the next 3 decades, largely thanks to aluminium alloys. Aivionics and wing design were largely solved by then. With the gas turbine, jet aircraft appeared, and Boeing is still effectively building and selling scaled-up versions of its 707 airframe (1957). The USAF will be flying the very same aircraft for over 80 years, the B-52. First flight 1952, last date af manufature: 1962. What progress has been made in aircraft over the last 65 years is largely limited to improved controls (both linkages and avionics), novel materials, and more recently, improved modeling duringg design and development. Outside military applications, that still has exceptionaally limited commercial impacts. See various sources, though Robert Gordon's The Rise and Fall of American Growth has a good overview. The contrast, particularly with man-years of effort and billions in spending, to fusion, couldn't be starker.