9 ms·

Parent was basically saying it has not been a physics problem for decades, it's already an engineering problem and there is no change there. The physics are kn

Parent was basically saying it has not been a physics problem for decades, it's already an engineering problem and there is no change there. The physics are known to work and have been demonstrated decades ago in a different engineering context (i.e. weapons).

jliptzin 4y ago
Didn’t we already know it’s just an engineering problem by virtue of the sun existing?
- woeirua 4y ago
  No. Just because the sun exists, does not mean that it is necessarily physically possible to emulate controlled nuclear fusion without an _immense_ gravity well. Ignition in this context is a validation of our understanding of the physics. _Now_ it is just an engineering problem.
- mlyle 4y ago
  Ordinary hydrogen-hydrogen fusion in the sun only works because the sun is so freakin' huge. It's so unlikely even under the sun's massive gravitational and heat that the power output is about 270W/cubic meter-- compare to human metabolism or an energetic compost pile, which is over 1000W/cubic meter. We actually have to do a whole lot better than the sun, under far less favorable conditions-- to have practical fusion for energy generation on Earth. Inertial confinement fusion ignition (and to a lesser extent, thermonuclear weapons) strongly suggest this is possible.
  - jliptzin 4y ago
    Interesting, didn’t know that!
- idiotsecant 4y ago
  Boy, the HN pedantry is potent this morning. The fact that black holes exist does not mean that we can spin one up to harvest it's hawking radiation for power. It's not just an engineering problem. That's not what that phrase means.
  - smt88 4y ago
    Your point is well-taken, but please be less of a jerk about it.
  - unethical_ban 4y ago
    Say that to rob74, the starter of this thread, who essentially says "so what if it is the first time we've ever had a net positive fusion reaction, there is still work to be done and I don't like the people working on it" in order to wave it off.
dotancohen 4y ago
As I understand it - correct me if I'm wrong - one of the consequences of the December 5 experiment is that the engineering uncertainty was brought into the realm of "this now fits the progress of engineering, so we expect to be able to engineer the thing given sufficient capital and time", rather than the previous "we have no idea if we'll ever be able to engineer this thing".
- HPsquared 4y ago
  It has always been a matter of building a machine with sufficient performance. That's engineering, by definition.
  - lazide 4y ago
    What kind of machine though is the point. A bomb? Already done. A fusion reactor? We’re still light years away from anything of the sort. This is only one tiny tiny step there, and we’ve got miles to go.
    - Robotbeat 4y ago
      This is actually a significant step, not a tiny step. Achieving fusion ignition, ie including the 2021 shot, is THE non-linear scaling effect needed to make fusion a viable energy source. The other items needed to make this practical would’ve been premature to fund without this significant advance. https://physicstoday.scitation.org/do/10.1063/PT.6.2.20221213a/full/ https://physicstoday.scitation.org/do/10.1063/PT.6.2.2022121... EDIT: Being down-voted, why? Previous steps to actually develop a power plant around NIF-like inertial fusion were cancelled in order to focus on achieving ignition first: https://en.wikipedia.org/wiki/Laser_Inertial_Fusion_Energy https://en.wikipedia.org/wiki/Laser_Inertial_Fusion_Energy
      - lazide 4y ago
        Uh no. For sure, you can’t even consider the possibility of a fusion power plant without the core reaction producing power. That they figured out how to do the energy equivalent of getting the coal to actually light (finally!) in this context, is indeed useful. But it is a tiny, tiny step towards an actual working fusion power plant. And it does nothing to fix the economic issues here in competition with all the other energy sources, which matters. Igniting that bit of ‘coal’ took near 100x the energy we got out of it. It was essentially putting it in a giant blowtorch, and then getting excited when it finally got lit and burned. That we previously only got half smoldering was indeed a problem! And that it finally lit is indeed cool. it also took an extreme amount of thought, precision, investment, etc. to do it once. Meanwhile, solar plants in the area were churning out billions of kwh.
zmgsabst 4y ago
We can debate the importance, but it’s clear that they’ve made a qualitative leap in their technology the past few years — a “breakthrough”. https://en.wikipedia.org/wiki/National_Ignition_Facility#/media/File%3ANIF_output_over_10_years.png https://en.wikipedia.org/wiki/National_Ignition_Facility#/me...
- HPsquared 4y ago
  That's quite the leap, clearly some big progress when it's presented like that.
- rz2k 4y ago
  And that graph does not include the 2022 experiment with 3.15, which also happened to be the first one with net positive output.
  - Robotbeat 4y ago
    Yup, here’s the one: https://physicstoday.scitation.org/do/10.1063/PT.6.2.20221213a/full/media/sizes/full/figure2-3.jpg https://physicstoday.scitation.org/do/10.1063/PT.6.2.2022121... Credit: Mark Herrmann/LLNL From this article: https://physicstoday.scitation.org/do/10.1063/PT.6.2.20221213a/full/ https://physicstoday.scitation.org/do/10.1063/PT.6.2.2022121... Clear qualitative difference. Additionally, this is laser energy, but the lasers aren’t used directly. They produce X-rays which are the ones that actually drive the ablative implosion of the fuel pellet. If you used X-rays directly, the gain value would be MUCH higher… I think by that measure, they would’ve achieved Q=1 back in 2013? Note that hey COULD use the lasers directly to drive implosion but haven’t yet. The Hohlraum/X-ray/indirect method I think produces more consistent lighting on the target, and is more analogous to the operation of an H-bomb, which is partly what this entire process is intended to replicate. They may do future experiments to try direct drive, in preparation for actually using this as a power production method and improving the efficiency dramatically… in combination with far higher efficiency modern lasers, this could enable Q high enough for net electricity production.
    - pfdietz 4y ago

jliptzin 4y ago

Didn’t we already know it’s just an engineering problem by virtue of the sun existing?

woeirua 4y ago
No. Just because the sun exists, does not mean that it is necessarily physically possible to emulate controlled nuclear fusion without an _immense_ gravity well. Ignition in this context is a validation of our understanding of the physics. _Now_ it is just an engineering problem.
mlyle 4y ago
Ordinary hydrogen-hydrogen fusion in the sun only works because the sun is so freakin' huge. It's so unlikely even under the sun's massive gravitational and heat that the power output is about 270W/cubic meter-- compare to human metabolism or an energetic compost pile, which is over 1000W/cubic meter. We actually have to do a whole lot better than the sun, under far less favorable conditions-- to have practical fusion for energy generation on Earth. Inertial confinement fusion ignition (and to a lesser extent, thermonuclear weapons) strongly suggest this is possible.
- jliptzin 4y ago
  Interesting, didn’t know that!
idiotsecant 4y ago
Boy, the HN pedantry is potent this morning. The fact that black holes exist does not mean that we can spin one up to harvest it's hawking radiation for power. It's not just an engineering problem. That's not what that phrase means.
- smt88 4y ago
  Your point is well-taken, but please be less of a jerk about it.
- unethical_ban 4y ago
  Say that to rob74, the starter of this thread, who essentially says "so what if it is the first time we've ever had a net positive fusion reaction, there is still work to be done and I don't like the people working on it" in order to wave it off.

dotancohen 4y ago

As I understand it - correct me if I'm wrong - one of the consequences of the December 5 experiment is that the engineering uncertainty was brought into the realm of "this now fits the progress of engineering, so we expect to be able to engineer the thing given sufficient capital and time", rather than the previous "we have no idea if we'll ever be able to engineer this thing".

HPsquared 4y ago
It has always been a matter of building a machine with sufficient performance. That's engineering, by definition.
- lazide 4y ago
  What kind of machine though is the point. A bomb? Already done. A fusion reactor? We’re still light years away from anything of the sort. This is only one tiny tiny step there, and we’ve got miles to go.
  - Robotbeat 4y ago
    This is actually a significant step, not a tiny step. Achieving fusion ignition, ie including the 2021 shot, is THE non-linear scaling effect needed to make fusion a viable energy source. The other items needed to make this practical would’ve been premature to fund without this significant advance. https://physicstoday.scitation.org/do/10.1063/PT.6.2.20221213a/full/ https://physicstoday.scitation.org/do/10.1063/PT.6.2.2022121... EDIT: Being down-voted, why? Previous steps to actually develop a power plant around NIF-like inertial fusion were cancelled in order to focus on achieving ignition first: https://en.wikipedia.org/wiki/Laser_Inertial_Fusion_Energy https://en.wikipedia.org/wiki/Laser_Inertial_Fusion_Energy
    - lazide 4y ago
      Uh no. For sure, you can’t even consider the possibility of a fusion power plant without the core reaction producing power. That they figured out how to do the energy equivalent of getting the coal to actually light (finally!) in this context, is indeed useful. But it is a tiny, tiny step towards an actual working fusion power plant. And it does nothing to fix the economic issues here in competition with all the other energy sources, which matters. Igniting that bit of ‘coal’ took near 100x the energy we got out of it. It was essentially putting it in a giant blowtorch, and then getting excited when it finally got lit and burned. That we previously only got half smoldering was indeed a problem! And that it finally lit is indeed cool. it also took an extreme amount of thought, precision, investment, etc. to do it once. Meanwhile, solar plants in the area were churning out billions of kwh.

zmgsabst 4y ago

We can debate the importance, but it’s clear that they’ve made a qualitative leap in their technology the past few years — a “breakthrough”. https://en.wikipedia.org/wiki/National_Ignition_Facility#/media/File%3ANIF_output_over_10_years.png https://en.wikipedia.org/wiki/National_Ignition_Facility#/me...

HPsquared 4y ago
That's quite the leap, clearly some big progress when it's presented like that.
rz2k 4y ago
And that graph does not include the 2022 experiment with 3.15, which also happened to be the first one with net positive output.
- Robotbeat 4y ago
  Yup, here’s the one: https://physicstoday.scitation.org/do/10.1063/PT.6.2.20221213a/full/media/sizes/full/figure2-3.jpg https://physicstoday.scitation.org/do/10.1063/PT.6.2.2022121... Credit: Mark Herrmann/LLNL From this article: https://physicstoday.scitation.org/do/10.1063/PT.6.2.20221213a/full/ https://physicstoday.scitation.org/do/10.1063/PT.6.2.2022121... Clear qualitative difference. Additionally, this is laser energy, but the lasers aren’t used directly. They produce X-rays which are the ones that actually drive the ablative implosion of the fuel pellet. If you used X-rays directly, the gain value would be MUCH higher… I think by that measure, they would’ve achieved Q=1 back in 2013? Note that hey COULD use the lasers directly to drive implosion but haven’t yet. The Hohlraum/X-ray/indirect method I think produces more consistent lighting on the target, and is more analogous to the operation of an H-bomb, which is partly what this entire process is intended to replicate. They may do future experiments to try direct drive, in preparation for actually using this as a power production method and improving the efficiency dramatically… in combination with far higher efficiency modern lasers, this could enable Q high enough for net electricity production.
  - pfdietz 4y ago