4 ms·

Fusion is hard. Neutrons are a concern, yes, but none of this matters without ignition, without break-even (choose your definition). Until break-even is achieve

Fusion is hard. Neutrons are a concern, yes, but none of this matters without ignition, without break-even (choose your definition). Until break-even is achieved, it’s all premature optimization to me. Compact or not, clever neutron handling or not, integrated tritium-breeding or not, break-even is the minimum bar to cross, and no one has crossed it outside of fission-triggered bombs. That must be the focus. Once that is achieved, there will be plenty of resources to solve the myriad of other problems, but until break-even is achieved (by ANY means other than fission trigger), solving those other problems just doesn’t matter.

pfdietz 7y ago
The focus on ignition is strange. If the engineering and economics look hopeless, then why focus on ignition? The only reason I can think of is that the people working on it want to keep their jobs and defer the likely practical showstoppers until after the ultimately irrelevant plasma physics problems are solved.
- tim333 7y ago
  Well it's a step in the direction. If you can get that to work then maybe you can then figure out the other stuff afterwards.
  - pfdietz 7y ago
    In the same sense that climbing a tree is a step in the direction of getting to the moon.
    - Robotbeat 7y ago
      In the same sense that flying to orbit is a step to getting to the Moon. We did Mercury before Apollo.
    - gmueckl 7y ago
      Climbing a tree is useful for going to the moon. Having access to heights from which to drop things is a prerequisite step for the first experiments that lead to an understanding of gravity and acceleration ;).
- graycat 7y ago
  Global level strategy suspicion, guess: The US has to try because China, Russia, even North Korea, are trying and it just MIGHT work, or something from it might work and be the basis of something serious eventually. Broad observation: Physical science research was a sleepy area until The Bomb. Then supposedly Ike with J. Conant, et al., said, IRCC, "Never again will US academics operate independent of the US military." Then the US Congress via the NSF and DoD went to the leading US research universities and "made them an offer they couldn't refuse" -- accept the grant money or cease to be a leading research university. And, oh, BTW, you can take 60% or so as overhead for the English department, the string quartet concerts, the little theater production, the glossy alumni magazine, the new front gate to the campus with the big, round fountain just inside, the new art gallery, a new, on campus, 6000 square foot Georgian house for the president with, of course, a black limo. Or some such!!!! Then the bio-medical sciences mentioned to Congress that a big fraction of Members of Congress are old and need medical care for heart disease, cancer, other diseases of aging, etc. so should have, say, the NIH to do for bio-medical what the NSF does for the STEM fields. Congress went along.
- Robotbeat 7y ago
  If ignition hasn’t been achieved, why bother with clever engineering or economics? Without ignition/breakeven, the best engineering and economics in the world are irrelevant. Ultimately, physics showstoppers matter more than any others.
Dumblydorr 7y ago
If you ignore all other parameters and achieve that one, you run the risk of walking down an engineering path that cannot deal with those downsides. Seems 30 years out still...
- Robotbeat 7y ago
  I just find that these other considerations are either an excuse or a distraction from actually meeting this minimum objective goal. Breakeven or get out.
  - pfdietz 7y ago
    Every journey starts with a first step, but so does every dead end. If the engineering and economic issues are showstoppers, then focusing on breakeven is simply wasting money. It's almost a canonical example of shortsightedness.
    - Robotbeat 7y ago
      It's actually much more true the other way around: if physics is somehow fundamentally preventing you from fusion ignition, then focusing on engineering or economic issues is a complete waste in money and a dead end. Because while economics and engineering change over time, physics[1] does not. It's like spending money trying to solve the economics challenges of a perpetual motion machine[2]. [1](Although our understanding of physics does.) [2](...which fusion is not)
      - pfdietz 7y ago
        A showstopper is a showstopper. Yes, physics can rule things out. But so can economics. There is no reason to give the first priority over the second, if the second is sufficiently bad. And I will claim those practical considerations render fusion very dubious. And yes, they change over time: they have gotten WORSE for fusion. It used to be that fusion was competing with fission to be that post-fossil energy source. That was, perhaps, not too unreasonable, especially if the fission had to be with breeding. But now, it competes with dramatically cheaper renewables.
learnfromstory 7y ago
The problem is that we need it to just barely break even and then a little bit more. Having a tremendously energetic fusion device is both useless and a solved problem: we already know how to light one off, but it only lasts a millisecond and it destroys everything for miles around. For what it is worth, fission also suffers this problem. A promptly critical fission reaction is possible, indeed quite easy to achieve, and very undesirable. All fission technology is dedicated to keeping the reaction just barely critical.

pfdietz 7y ago

The focus on ignition is strange. If the engineering and economics look hopeless, then why focus on ignition? The only reason I can think of is that the people working on it want to keep their jobs and defer the likely practical showstoppers until after the ultimately irrelevant plasma physics problems are solved.

tim333 7y ago
Well it's a step in the direction. If you can get that to work then maybe you can then figure out the other stuff afterwards.
- pfdietz 7y ago
  In the same sense that climbing a tree is a step in the direction of getting to the moon.
  - Robotbeat 7y ago
    In the same sense that flying to orbit is a step to getting to the Moon. We did Mercury before Apollo.
  - gmueckl 7y ago
    Climbing a tree is useful for going to the moon. Having access to heights from which to drop things is a prerequisite step for the first experiments that lead to an understanding of gravity and acceleration ;).
graycat 7y ago
Global level strategy suspicion, guess: The US has to try because China, Russia, even North Korea, are trying and it just MIGHT work, or something from it might work and be the basis of something serious eventually. Broad observation: Physical science research was a sleepy area until The Bomb. Then supposedly Ike with J. Conant, et al., said, IRCC, "Never again will US academics operate independent of the US military." Then the US Congress via the NSF and DoD went to the leading US research universities and "made them an offer they couldn't refuse" -- accept the grant money or cease to be a leading research university. And, oh, BTW, you can take 60% or so as overhead for the English department, the string quartet concerts, the little theater production, the glossy alumni magazine, the new front gate to the campus with the big, round fountain just inside, the new art gallery, a new, on campus, 6000 square foot Georgian house for the president with, of course, a black limo. Or some such!!!! Then the bio-medical sciences mentioned to Congress that a big fraction of Members of Congress are old and need medical care for heart disease, cancer, other diseases of aging, etc. so should have, say, the NIH to do for bio-medical what the NSF does for the STEM fields. Congress went along.
Robotbeat 7y ago
If ignition hasn’t been achieved, why bother with clever engineering or economics? Without ignition/breakeven, the best engineering and economics in the world are irrelevant. Ultimately, physics showstoppers matter more than any others.

Dumblydorr 7y ago

If you ignore all other parameters and achieve that one, you run the risk of walking down an engineering path that cannot deal with those downsides. Seems 30 years out still...

Robotbeat 7y ago
I just find that these other considerations are either an excuse or a distraction from actually meeting this minimum objective goal. Breakeven or get out.
- pfdietz 7y ago
  Every journey starts with a first step, but so does every dead end. If the engineering and economic issues are showstoppers, then focusing on breakeven is simply wasting money. It's almost a canonical example of shortsightedness.
  - Robotbeat 7y ago
    It's actually much more true the other way around: if physics is somehow fundamentally preventing you from fusion ignition, then focusing on engineering or economic issues is a complete waste in money and a dead end. Because while economics and engineering change over time, physics[1] does not. It's like spending money trying to solve the economics challenges of a perpetual motion machine[2]. [1](Although our understanding of physics does.) [2](...which fusion is not)
    - pfdietz 7y ago
      A showstopper is a showstopper. Yes, physics can rule things out. But so can economics. There is no reason to give the first priority over the second, if the second is sufficiently bad. And I will claim those practical considerations render fusion very dubious. And yes, they change over time: they have gotten WORSE for fusion. It used to be that fusion was competing with fission to be that post-fossil energy source. That was, perhaps, not too unreasonable, especially if the fission had to be with breeding. But now, it competes with dramatically cheaper renewables.

learnfromstory 7y ago

The problem is that we need it to just barely break even and then a little bit more. Having a tremendously energetic fusion device is both useless and a solved problem: we already know how to light one off, but it only lasts a millisecond and it destroys everything for miles around. For what it is worth, fission also suffers this problem. A promptly critical fission reaction is possible, indeed quite easy to achieve, and very undesirable. All fission technology is dedicated to keeping the reaction just barely critical.