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Comment by flexie | Hacker News Reader

Here is more on the tech, including a drawing: http://aviationweek.com/technology/skunk-works-reveals-compa...

This article provides a lot more engineering information and other background and is well worth a thorough read. Thanks to flexie for finding and sharing the link.

Thanks, much, much better than the original article.

This looks very similar to the old Russian Gas Dynamic Trap: https://e-reports-ext.llnl.gov/pdf/366958.pdf

RF and neutral beam heated steady reactor with very high mirror ratio and superconductors.

What is the operating temperature of these superconducting magnets?

I can't see how heat energy is supposed to be flowing out of that plasma envelope yet the magnets are supposed to stay at near-zero temps?

Seems premature to call this a breakthrough when they haven't even built a prototype yet.

This is HN. If the hyperloop was a technological breakthrough, so is this press release.

Hyperloop case doesn't have 50 years of track record of being "just few years from now", and as far as I remember, the design was more-less feasible if only someone would get around to building it. It didn't have such hard problems to be solved as fusion still has.

> Hyperloop case doesn't have 50 years of track record of being "just few years from now"

There have been steady incremental advancements in the field. I think your knee jerk reaction is coming from "cold fusion" which does have the problems you are talking about. Two very different fields.

The main issue with fusion is that it can't be weaponized and therefore doesn't have a nice military grant behind it. It lacks a Manhattan Project. It's probably always been "a few years from now" under the assumption of adequate funding.

The events following this announcement will probably be a good time to form a concrete opinion on fusion. It's being given a fair chance, so lets first see if it can prove itself.

This is promising stuff. Most of the other reactors have been Tokamak reactors - which are better suited to research and not practical applications, so we could be seeing some interesting results here.

It already has been weaponized, in the form of a fusion bomb.

zamalek probably meant to refer to the waste products from fusion not being a proliferation concern.

It's true that there were people in the early 70s who said fusion was thirty years away. However, they conditioned that on a certain level of funding. For the funding they got, the same people said it would never happen.

This is an enlightening explanation: http://www.chforum.org/scenario2012/paper1-4-1.jpg

Thanks for the graph, and @DennisP for saying the same in written words. I recall seeing that graph once on HN, but for some reason I didn't pay attention to it back then.

I think you could make the argument that fusion is more or less feasible if someone would just get around to building it too...

I don't believe this is the case. I'm pretty sure there have been "hard" limits so far on what can be achieved. I'm not a physicist, not even close but as I understand it two issues remain. One is that sustaining the fusion reaction has been problematic. I believe the longest sustained reactions have been less than one second. Two is that currently we have to put more energy into creating and sustaining the reaction than it yields. These two things make this categorically different than a challenge like building the hyperloop which as far as I know didn't have any unsolved science or engineering problems.

Again, I could be wrong on my physics but as I understand it, fusion power is still a question of "is it even possible" whereas the hyperloop was more of a question about socioeconomic will.

One of the problems with creating longer-running fusion reactions is that if they do it, in order for the reactor to not wildly overheat almost instantly, they need a massive cooling system to carry the generated heat away. At that point, you almost might as well hook up a steam turbine loop and generator and put the power on the grid.

There's lots of other problems too - I don't think they have a well-tested solution for adding fresh fuel and disposing of the fused products on an ongoing basis.

JT-60 in Japan has done about half a minute, actually. There is less of an issue with sustaining reactions (since there has been steady progress over the years) than with coming up with materials that would stand up under a commercial fusion reactor's duty cycle.

http://iopscience.iop.org/0029-5515/48/8/085002

See, not a physicist. Thanks.

I was curious about detail when I saw the news, Thanks for sharing!

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