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Comment by cyanoacry | Hacker News Reader

This is definitely true, and the BBC totally omitted these facts. The official NIF announcement[1] tried a little bit to cover their tracks. They posted some flashy numbers about the total energy output from neutrons, but nestled in the bottom of the page is the total energy dumped into the entire system:

1.7 megajoules.

In comparison, the fusion power produced was a paltry 8 kilojoules, which they compare to the "energy required to form the plasma".

For this technology to be actually effective, there needs to be a multiplier of several thousand. As other commenters have mentioned, this is mostly just nuclear weapons development.

[1] http://www.physicstoday.org/daily_edition/politics_and_polic...

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> total energy dumped into the entire system: 1.7 megajoules. In comparison, the fusion power produced was a paltry 8 kilojoules

In other words, the National Ignition Facility hasn't achieved ignition yet.

If you can actually achieve ignition, then nobody will care about the megajoules needed to get it ignited. Because once you've got ignition, you can get an arbitrary amount of energy out.

But if you can't get ignition, well, then, that pesky 0.3% heating efficiency will still leave you a couple of orders of magnitude away from engineering breakeven.

> get an arbitrary amount of energy out.

Not really. You have to build larger, or more, power plants. So you have to make enough extra energy to sell to pay for plants.

While they have had problems in the recent past: https://www.sciencenews.org/article/ignition-failed

~~ They've since had ignition: http://www.independentnews.com/news/article_792110c0-2c5b-11... ~~

[I'm positive that the ICF's predecessors also achieved ~~ignition~~ fusion on smaller scales.]

The real trick is that [0] you need to get out more than you put in (exceed break-even) [1] you need to be able to harness the energy produced by the ignition and [2] be able to do it over and over again, producing reliable power.

> They've since had ignition

No. Notice how it is worded.

> "More importantly, Moses said, the mechanism that generated the powerful energy burst appeared to be the self-sustaining thermonuclear fusion process that defines ignition."

In other words, they did not achieve ignition. They achieved something that is necessary to get ignition. Specifically, alpha heating.

This is another important step on the road to ignition. It is not, however, ignition itself.

Why do you think the title of the article says "Marks Progress Toward Ignition," rather than "Finally Achieves Ignition?"

You're right. In my head "ignition"=fusion, so I was auto-translating as I was skimming. They're looking for something slightly different, and probably using energy output (among other things) as indications of self-sustained fusion, which we've certainly obtained in bombs (fission explosion sets off fusion reaction ☞ big bada boom).

And this seems to hand out a wealth of information as to why they haven't gotten there yet: http://www.reddit.com/r/technology/comments/1nxtyb/nuclear_f...

The BBC did say:

> the amount of energy released through the fusion reaction exceeded the amount of energy being absorbed by the fuel

As soon as I saw that, I immediately understood that they're nowhere near breakeven -- much less power generation.

It's an extremely misleading half-truth. Worse, Q must be an order of magnitude greater than 1 IIRC to be economically viable.

They did not mention Q at all in the article and their claims cannot be compared to any intellectually honest definition of "break even" in good faith without more information

IIRC from a recent HN discussion, ITER has attained Q of 0.65 and NIF is nowhere close to that.

Are you sure you're not thinking of JET[1]? ITER's not scheduled to be operational until 2020 AFAICR.

Incidentally when I went to see JET (it's up the road from me, not that far from Oxford) the scale of the thing was enormous. They mentioned that they'd had been able to sustain plasma for 600 seconds. I've got some pictures up[2] on flickr.

[1] - http://www.i15.p.lodz.pl/strony/EIC/ne/future_2_1.html

[2] - http://www.flickr.com/photos/z3r0kl3w/sets/72157623979315835...

I'm jealous you got to see JET.

One of my favorite stories is the disruption. This happens when things don't go just right, and all the plasma with its energy squirts onto one spot. This typically puts the equipment in jeopardy. People try to prevent it, but as they push the boundaries of what's been done, it's going to happen.

Keep in mind that there's only about as much mass in the entire chamber as in a few cubic centimeters of air; it's basically a vacuum. But what little there is is so hot, and there's so much energy wound up in the fields. When JET had a disruption, the entire machine, the largest tokamak in the world, LIFTED ITSELF OFF THE GROUND AND JUMPED A FEW FEET OVER.

The LHC beam-dumps[1] at CERN are also at that holy-shit-physics scale. A more explanatory article[2] also covers the superconducting magnet quenches, in which up to 10GJ of stored energy suddenly decides it really ought to be following Ohm's law again.

Any good refs for this disruption situation?

[1] http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach...

[2] http://www.symmetrymagazine.org/article/december-2007/protec...

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