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Interesting. What are the benefits to any of these approaches in your opinion? What seems key to me is having a large enough energy output to harness without w

by kposehn 14y ago

Interesting. What are the benefits to any of these approaches in your opinion? What seems key to me is having a large enough energy output to harness without waste in the flare window while being able to manufacture fuel in sufficient volumes to power the sucker.

DennisP 14y ago
Biggest benefit, but theoretically hardest to achieve, is boron fusion, which is nonradioactive. Since the energy is carried away in charged particles instead of neutrons, you don't need a steam cycle. Focus fusion would be a small boron fusion device, producing 5MW per reactor at a tenth the price of coal. Potential drawbacks: the energy gain is a bit marginal so you have to also capture x-rays, and erosion of the electrodes could be a problem. But a 5MW plant should only cost half a million or so. Picosecond laser would also do boron fusion (which in that design is only ten times harder than D-T), but with a 10,000x energy gain, divided by the one percent efficiency of the laser. It's projected to produce power as cheaply as focus fusion. Tri-Alpha supposedly could achieve boron fusion but they've been very tight-lipped about the whole thing. They've gotten close to $100 million in venture capital though, including from Paul Allen. Polywell, if it works, could do D-T fusion in a 2-meter sphere, or boron fusion in a 3-meter. I've seen relatively high projected costs, though that may be for D-T. If you're a scifi fan, this was invented by the guy who came up with Bussard ramjets. He was also a big tokamak guy, before he gave up on them. Levitated dipole sorta turns tokamaks inside-out, with the plasma contained around the outside of a solid levitating torus. This seems to solve some plasma instabilities that tokamaks struggle with. They say it would be ideal for D-D fusion. Deuterium (for D-D) and boron are readily available in large quantities relative to what we'd need. D-T needs tritium, which would have to be made by bombarding lithium with the neutrons from the fusion reaction. This would limit how fast we could roll out the reactors. D-D and D-T would both require steam turbines. Most people focus on D-T since it has the least stringent requirements, and the rest of these are D-T. General Fusion uses a vat of molten lead and lithium, spinning to open a channel down the middle. A plasma ball is shot in from each end, then 200 steam-driven pistons slam into the container, making an acoustic shock wave that compresses the D-T plasma. The neutrons hit the lithium for tritium, heat the lead, and it all drives the steam turbine, with some steam diverted to drive the pistons. Jeff Bezos is a big investor in this one. Right now they've got the pistons working with the tight timing they need, and a prototype with a dozen pistons or so. NIF says they're farthest along the development path, they're leveraging big advances in lasers, and with their LIFE development they're already working with thirty or so commercial suppliers to put together a practical reactor design with as much off-the-shelf equipment as possible. They don't need as much tritium inventory to start up as tokamaks, and think they can be competitive with fossil fuels. They've been talking 2020 or so for a demo reactor, but they also thought they'd manage ignition this year, and a recent DOE report said it'll be another couple years. Helion targets a middle ground between tokamaks and NIF, in terms of temperature and density, which they think will be easier. They need $20 million for a full-size reactor, already built a 1/3-scale test unit. They're also working with NASA on a fusion rocket design. Tokamak (like ITER) seems to be on a solid path to net power, but it's such a huge, complicated, expensive device that it's hard to imagine it being economical, and they're talking about a thirty year timeframe at best.
- ThaddeusQuay2 14y ago
  Bussard was a genius who couldn't get funding. Less than a year before he died of cancer, he asked Google for a paltry sum to continue his research, shortly after the government cut him off. I have wondered why Google didn't jump on this. Do you know? And now, ironically, the Navy, the very entity which tossed him out, has not only picked up his research, but has apparently gone all quiet about the results. Here's the video of his excellent (and, in retrospect, sad) presentation at Google. I say "sad" because it shows an intellectual giant, nearly on his deathbed, practically begging an Internet giant, for what was really the tiny amount he needed to continue with what had become his life's work. Anyway, it's an intense, fast-paced, insightful, and (likely) final public look into his mind, his work, and his character. http://youtube.com/watch?v=FhL5VO2NStU http://youtube.com/watch?v=FhL5VO2NStU (Should Google Go Nuclear?) http://youtube.com/watch?v=rk6z1vP4Eo8 http://youtube.com/watch?v=rk6z1vP4Eo8 (archive copy) UPDATE: I found a good paper covering the above talk. It's a 25-page PDF, of less than 2MB, with color photos and charts from the video. http://askmar.com/ConferenceNotes/Should%20Google%20Go%20Nuclear.pdf http://askmar.com/ConferenceNotes/Should%20Google%20Go%20Nuc...
  - dalke 14y ago
    I watched the video of his Google presentation. It seemed to be more of the "overwhelm them with slides" sort of talk. It did not instill in me a sense of that what he was talking about was practical, but rather that he was in his own world and that if he just showed how neat the physics was that he would get funding.
    - ThaddeusQuay2 14y ago
      It was more of a "slides, with a whole lot of words coming out of his mouth, the mouth of one of the world's foremost experts on the subject matter" sort of talk. I got the sense that it was practical to proceed to the next level, which is all he was asking of Google. I also got the impression that he was in his own world. That tends to be how geniuses talk. There was no introduction, no covering of the basics, no time to settle in. It was like jumping into the ocean of his mind, and you either sank or swam with his thoughts. He was 78, and possibly already sick with cancer at that time, yet he came off as a young visionary with unwavering optimism. That, combined with his accomplishments, made him amazing, and one of my heroes.

by kposehn 14y ago

DennisP 14y ago

Biggest benefit, but theoretically hardest to achieve, is boron fusion, which is nonradioactive. Since the energy is carried away in charged particles instead of neutrons, you don't need a steam cycle. Focus fusion would be a small boron fusion device, producing 5MW per reactor at a tenth the price of coal. Potential drawbacks: the energy gain is a bit marginal so you have to also capture x-rays, and erosion of the electrodes could be a problem. But a 5MW plant should only cost half a million or so. Picosecond laser would also do boron fusion (which in that design is only ten times harder than D-T), but with a 10,000x energy gain, divided by the one percent efficiency of the laser. It's projected to produce power as cheaply as focus fusion. Tri-Alpha supposedly could achieve boron fusion but they've been very tight-lipped about the whole thing. They've gotten close to $100 million in venture capital though, including from Paul Allen. Polywell, if it works, could do D-T fusion in a 2-meter sphere, or boron fusion in a 3-meter. I've seen relatively high projected costs, though that may be for D-T. If you're a scifi fan, this was invented by the guy who came up with Bussard ramjets. He was also a big tokamak guy, before he gave up on them. Levitated dipole sorta turns tokamaks inside-out, with the plasma contained around the outside of a solid levitating torus. This seems to solve some plasma instabilities that tokamaks struggle with. They say it would be ideal for D-D fusion. Deuterium (for D-D) and boron are readily available in large quantities relative to what we'd need. D-T needs tritium, which would have to be made by bombarding lithium with the neutrons from the fusion reaction. This would limit how fast we could roll out the reactors. D-D and D-T would both require steam turbines. Most people focus on D-T since it has the least stringent requirements, and the rest of these are D-T. General Fusion uses a vat of molten lead and lithium, spinning to open a channel down the middle. A plasma ball is shot in from each end, then 200 steam-driven pistons slam into the container, making an acoustic shock wave that compresses the D-T plasma. The neutrons hit the lithium for tritium, heat the lead, and it all drives the steam turbine, with some steam diverted to drive the pistons. Jeff Bezos is a big investor in this one. Right now they've got the pistons working with the tight timing they need, and a prototype with a dozen pistons or so. NIF says they're farthest along the development path, they're leveraging big advances in lasers, and with their LIFE development they're already working with thirty or so commercial suppliers to put together a practical reactor design with as much off-the-shelf equipment as possible. They don't need as much tritium inventory to start up as tokamaks, and think they can be competitive with fossil fuels. They've been talking 2020 or so for a demo reactor, but they also thought they'd manage ignition this year, and a recent DOE report said it'll be another couple years. Helion targets a middle ground between tokamaks and NIF, in terms of temperature and density, which they think will be easier. They need $20 million for a full-size reactor, already built a 1/3-scale test unit. They're also working with NASA on a fusion rocket design. Tokamak (like ITER) seems to be on a solid path to net power, but it's such a huge, complicated, expensive device that it's hard to imagine it being economical, and they're talking about a thirty year timeframe at best.

ThaddeusQuay2 14y ago
Bussard was a genius who couldn't get funding. Less than a year before he died of cancer, he asked Google for a paltry sum to continue his research, shortly after the government cut him off. I have wondered why Google didn't jump on this. Do you know? And now, ironically, the Navy, the very entity which tossed him out, has not only picked up his research, but has apparently gone all quiet about the results. Here's the video of his excellent (and, in retrospect, sad) presentation at Google. I say "sad" because it shows an intellectual giant, nearly on his deathbed, practically begging an Internet giant, for what was really the tiny amount he needed to continue with what had become his life's work. Anyway, it's an intense, fast-paced, insightful, and (likely) final public look into his mind, his work, and his character. http://youtube.com/watch?v=FhL5VO2NStU http://youtube.com/watch?v=FhL5VO2NStU (Should Google Go Nuclear?) http://youtube.com/watch?v=rk6z1vP4Eo8 http://youtube.com/watch?v=rk6z1vP4Eo8 (archive copy) UPDATE: I found a good paper covering the above talk. It's a 25-page PDF, of less than 2MB, with color photos and charts from the video. http://askmar.com/ConferenceNotes/Should%20Google%20Go%20Nuclear.pdf http://askmar.com/ConferenceNotes/Should%20Google%20Go%20Nuc...
- dalke 14y ago
  I watched the video of his Google presentation. It seemed to be more of the "overwhelm them with slides" sort of talk. It did not instill in me a sense of that what he was talking about was practical, but rather that he was in his own world and that if he just showed how neat the physics was that he would get funding.
  - ThaddeusQuay2 14y ago
    It was more of a "slides, with a whole lot of words coming out of his mouth, the mouth of one of the world's foremost experts on the subject matter" sort of talk. I got the sense that it was practical to proceed to the next level, which is all he was asking of Google. I also got the impression that he was in his own world. That tends to be how geniuses talk. There was no introduction, no covering of the basics, no time to settle in. It was like jumping into the ocean of his mind, and you either sank or swam with his thoughts. He was 78, and possibly already sick with cancer at that time, yet he came off as a young visionary with unwavering optimism. That, combined with his accomplishments, made him amazing, and one of my heroes.