4 ms·

Am I wrong in thinking that the energy quantities here are shockingly small? The 1.8 MJ laser array that's being used to trigger these reactions, that's like 4

Am I wrong in thinking that the energy quantities here are shockingly small? The 1.8 MJ laser array that's being used to trigger these reactions, that's like 400 calories, less energy than you'd get from a ham and cheese sandwich with mayo, and the output they're hoping to achieve, 100kJ, that's 2mL of gasoline.

1-6 6y ago
Wasn't all this effort involved just to prove Fusion is possible before going all into the tech? The machines are massive today but so were early computers.
- akiselev 6y ago
  Nuclear arsenal maintenance drove this effort.
mytailorisrich 6y ago
If I understand correctly how this works, this is a laser pulse of 1.8MJ and that pulse's duration is in the 20ns range. So it's actually massively powerful but very short. If you were to burn gasoline at a rate of 2mL per 20ns you would be burning 100,000 L per second, which is a higher rate than Saturn 5 on takeoff so quite a burner...
aqme28 6y ago
I mean, for small enough duration in time, any power plant is producing a laughably small amount of energy. How much power it produces is the better question.
jvanderbot 6y ago
If power in < power out, they've "proven" fusion, and the rest is scaling.
- handol 6y ago
  1800 kJ > 100 kJ Even if they achieve 'burning plasma', it's still like a 100hp engine using an 1800hp spark plug.
  - jvanderbot 6y ago
    This really doesn't have anything to do with what I said or the long-term goals of a fusion project as stated in TFA.
asah 6y ago
.oO( humans... portable mayo powered reactors! #matrix )
colechristensen 6y ago
But is it a ham sandwich every hour or every few nanoseconds?
dredmorbius 6y ago
1 Hiroshima atomic bomb (15 kt TNT) is 37,500,000 ham sandwiches (at 400 kcal/sandwich).
- Someone 6y ago
  Such comparisons are almost meaningless. For explosives, its not only about how much energy gets released, but also (almost more so) about how fast it gets released. For example, per kilogram, TNT releases less than a tenth of the energy that burning gasoline does, and a sandwich stores more energy than the equivalent weight in dynamite (but both are cheating, as TNT and dynamite both include the oxygen needed to ‘burn’ them, whereas gasoline and sandwiches don’t)
  - dredmorbius 6y ago
    And the forms of energy, deliverable size, etc., etc. Ham sandwich prompt radiation, thermal pulse, blast, and long-term radiation effects are somewhat less than those of the Little Boy gadget. The last may depend on how much hot sauce is applied. Both weight and volume exceeded the B-29 and would be better suited for a bulk-cargo carrier of about 30' beam, 40' depth, and 300' length. The relationship between promptness and completeness of reaction is an interesting one, and not limited to TNT and petroleum. The WWII atomic weapons haad a pretty remarckably low efficiency --- most of the fissile material was dispersed before it could fully react. Nuclear power generation is far more efficient. And generally slower. See related the Beruit 2020 ammonium nitrate explosion: https://news.ycombinator.com/item?id=25154155 https://news.ycombinator.com/item?id=25154155 https://news.ycombinator.com/item?id=24064248 https://news.ycombinator.com/item?id=24064248
leephillips 6y ago
That 1.8 Mj is the energy in the laser output. I haven’t looked at the numbers for a while, but it probably takes 10x that much energy to operate the laser facility. A commercial fusion power plant will never exist. And it’s no accident that the article doesn’t mention the laser efficiency. NIF has a public relations office that has honed its game over decades. Their purpose is to influence Congress by selective reporting through press releases and by feeding propaganda into articles like this.
raziel2701 6y ago
Yeah, that's what's so incredibly powerful about nuclear energy, e=mc^2 of a grain of sand is a huge amount of energy.
jjk166 6y ago
1 MJ is the optimal energy scale for inertial confinement fusion. Going larger makes the fuel harder to compress, going smaller means there is less fuel that gets compressed; either way your ratio of input energy to output energy goes down. Also while these energies are low, they are also for very short durations. 1.8 MJ in 1 ns is 1.8 PW.

1-6 6y ago

Wasn't all this effort involved just to prove Fusion is possible before going all into the tech? The machines are massive today but so were early computers.

akiselev 6y ago
Nuclear arsenal maintenance drove this effort.

mytailorisrich 6y ago

If I understand correctly how this works, this is a laser pulse of 1.8MJ and that pulse's duration is in the 20ns range. So it's actually massively powerful but very short. If you were to burn gasoline at a rate of 2mL per 20ns you would be burning 100,000 L per second, which is a higher rate than Saturn 5 on takeoff so quite a burner...

aqme28 6y ago

I mean, for small enough duration in time, any power plant is producing a laughably small amount of energy. How much power it produces is the better question.

jvanderbot 6y ago

If power in < power out, they've "proven" fusion, and the rest is scaling.

handol 6y ago
1800 kJ > 100 kJ Even if they achieve 'burning plasma', it's still like a 100hp engine using an 1800hp spark plug.
- jvanderbot 6y ago
  This really doesn't have anything to do with what I said or the long-term goals of a fusion project as stated in TFA.

asah 6y ago

.oO( humans... portable mayo powered reactors! #matrix )

colechristensen 6y ago

But is it a ham sandwich every hour or every few nanoseconds?

dredmorbius 6y ago

1 Hiroshima atomic bomb (15 kt TNT) is 37,500,000 ham sandwiches (at 400 kcal/sandwich).

Someone 6y ago
Such comparisons are almost meaningless. For explosives, its not only about how much energy gets released, but also (almost more so) about how fast it gets released. For example, per kilogram, TNT releases less than a tenth of the energy that burning gasoline does, and a sandwich stores more energy than the equivalent weight in dynamite (but both are cheating, as TNT and dynamite both include the oxygen needed to ‘burn’ them, whereas gasoline and sandwiches don’t)
- dredmorbius 6y ago
  And the forms of energy, deliverable size, etc., etc. Ham sandwich prompt radiation, thermal pulse, blast, and long-term radiation effects are somewhat less than those of the Little Boy gadget. The last may depend on how much hot sauce is applied. Both weight and volume exceeded the B-29 and would be better suited for a bulk-cargo carrier of about 30' beam, 40' depth, and 300' length. The relationship between promptness and completeness of reaction is an interesting one, and not limited to TNT and petroleum. The WWII atomic weapons haad a pretty remarckably low efficiency --- most of the fissile material was dispersed before it could fully react. Nuclear power generation is far more efficient. And generally slower. See related the Beruit 2020 ammonium nitrate explosion: https://news.ycombinator.com/item?id=25154155 https://news.ycombinator.com/item?id=25154155 https://news.ycombinator.com/item?id=24064248 https://news.ycombinator.com/item?id=24064248

leephillips 6y ago

That 1.8 Mj is the energy in the laser output. I haven’t looked at the numbers for a while, but it probably takes 10x that much energy to operate the laser facility. A commercial fusion power plant will never exist. And it’s no accident that the article doesn’t mention the laser efficiency. NIF has a public relations office that has honed its game over decades. Their purpose is to influence Congress by selective reporting through press releases and by feeding propaganda into articles like this.

raziel2701 6y ago

Yeah, that's what's so incredibly powerful about nuclear energy, e=mc^2 of a grain of sand is a huge amount of energy.

jjk166 6y ago

1 MJ is the optimal energy scale for inertial confinement fusion. Going larger makes the fuel harder to compress, going smaller means there is less fuel that gets compressed; either way your ratio of input energy to output energy goes down. Also while these energies are low, they are also for very short durations. 1.8 MJ in 1 ns is 1.8 PW.