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Comment by lutusp | Hacker News Reader

> Hot fusion has been around for a long time.

Only in the stars and in thermonuclear weapons. It has not been achieved in a break-even sense anywhere else, in spite of decades of research. Many very large projects are dedicated to achieving it, including the National Ignotion Facility:

http://en.wikipedia.org/wiki/National_Ignition_Facility

The linked article shows that, in spite of vast amounts of money being spent, the project has yet to achieve break-even (i.e. produce more power than required to start the reaction).

> In fact I remember a couple of high school kids made a hot fusion device once.

No, that did not happen. It's an urban myth.

View on HN

http://www.ncsu.edu/park_scholarships/news/article.php?id=24...

Nowhere near break even though.

This is just a plasma generator, not a fusion reactor. Not to dismiss this student's achievements, but any fluorescent lamp is a plasma source. Plasma is the "fourth state of matter", essentially separate electrons and nuclei in a relatively high energy, electrically conductive medium:

https://en.wikipedia.org/wiki/Plasma_(physics)

It's a fusor - which does (as its name suggests) do fusion - which is why they are used as neutron sources.

http://en.wikipedia.org/wiki/Fusor

A quote from your linked article: "Hopes at the time were high that it could be quickly developed into a practical source of fusion power. However, as with other fusion experiments, development into a generator has proven to be difficult."

Translation: no break-even fusion reaction. If this approach held promise for fusion power research, it would be being explored instead of the millions of dollars in the much more common laser-confinement and tokamak approaches.

Strictly speaking and from a technical standpoint, if it doesn't produce more power than is present for conventional reasons (like electronic current flow), and in spite of its name, it's not a fusion reactor as that term is understood in physics.

It's a nice plasma source, and it produces neutrons -- very useful -- but it's not a fusion power source.

I never said it was a "reactor", or that it was close to break even - merely that creating a device where fusion reactions do occur is not that difficult.

Read my comment above I say "Nowhere near break even though."

Incidentally, there has been a lot of work in inertial electrostatic confinement - it doesn't look terribly promising and no it is not break even but people do appear to be working in this area:

http://en.wikipedia.org/wiki/Polywell

As established by arethuza, hot fusion has been accomplished for some time, relatively easily, outside of thermonuclear weapons and stars. That was the claim in dispute. Nowhere in this thread was there a claim about power generation.

> As established by arethuza, hot fusion has been accomplished for some time ...

Let's be clear about what we're talking about. A fusion generator by definition produces more power than it requires. Apart from stars and thermonuclear devices, this has not been achieved anywhere. Without clear terminology, we will go in circles.

Also, the NASA project documents specify and require a net power gain in the fusion reaction:

http://www.nasa.gov/directorates/spacetech/niac/2012_phaseII...

Quote: "an in-depth analysis of the rocket design and spacecraft integration as well as mission architectures enabled by the FDR need to be performed. Fulfilling these three elements form the major tasks to be completed in the proposed Phase II study. A subscale, laboratory liner compression test facility will be assembled with sufficient liner kinetic energy (~ 0.5 MJ) to reach fusion breakeven conditions."

> Nowhere in this thread was there a claim about power generation.

Except in the NASA documents that describe the project under discussion.

Yea. That is what is called hot fusion - where you have to put in energy to keep the fusion going.

And yes I was referring to the Fusor linked below. That is hot fusion.

> That is what is called hot fusion - where you have to put in energy to keep the fusion going.

No -- in general, "hot fusion" means producing more power than is required to start the reaction. Otherwise the term "hot fusion" makes no sense, since a reaction with a power gain < 1 is endothermic.

I emphasize that the term "hot fusion" is used in a lot of different ways, by people who aren't using it in its strict physical meaning. But in physics, "hot fusion" should mean an exothermic fusion reaction.

> And yes I was referring to the Fusor linked below. That is hot fusion.

It's not a fusion generator, which by definition produces more power than it requires. And the NASA documents that describe the project under discussion specify a fusion generator, a device with a power gain > 1.

http://www.nasa.gov/directorates/spacetech/niac/2012_phaseII...

"an in-depth analysis of the rocket design and spacecraft integration as well as mission architectures enabled by the FDR need to be performed. Fulfilling these three elements form the major tasks to be completed in the proposed Phase II study. A subscale, laboratory liner compression test facility will be assembled with sufficient liner kinetic energy (~ 0.5 MJ) to reach fusion breakeven conditions."

Note that last few words.

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