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Comment by calibas | Hacker News Reader

Note, the power output was about 1/3 the power needed to sustain the reaction.

> JET’s latest experiment sustained a Q of 0.33 for 5 seconds, says Rimini. JET is a scaled-down version of ITER, at one-tenth of the volume — a bathtub compared to a swimming pool, says Proll. It loses heat more easily than ITER, so it was never expected to hit breakeven. If engineers applied the same conditions and physics approach to ITER as to JET, she says, it would probably reach its goal of a Q of 10, producing ten times the energy put in.

This seems odd to me, nobody has reached a Q of 1 yet, and she's claiming to be able to reach 10? That's great if it's true, but it seems a little fishy...

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Q=10 is still not enough if you actually measure the whole experimental setup. Don't forget that to goal is to make a power plant where the whole building produces more energy than it consumes, and does it economically.

A 1000% return is insane economically. Perhaps I'm not seeing the logic but the pure YOY return on 1000% seems to logically conclude a rational strategy of "nothing else matters besides building this and it will easily pay off and investment"

This just means for every n W of _heat_ injected the fusion creates 10n W of heat. But I'm pretty sure the experiment itself consumes much more electricity than it could theoretically produce (don't forget that converting heat to electricity has an efficiency below 50%). Fusion researchers mislead the public to get more funding when they say ITER will make more energy than it requires. Fusion might be never viable.

Yeah well anything above a ratio of 1 would be beyond anything we have in terms of return based on investment in relation to cost to generate heat and it’s output. Basically all technology thus far is <1 right?

Q is just energy out over energy in. It is not an economic return.

Yeah but what else puts out more than puts in energy wise?

Any energy source that people actually use. And most of them have near-zero energy input during active use.

A 1000% return only just covers unavoidable inefficiencies.

No Tokamak will ever pay off its investment.

Right, that’s the ridiculousness of it.

The good thing about fusion is that a lot of problems stem from the size of the surface area as compared to the volume.

The bigger the reaction vessel gets, the favorably this ratio is.

This experiment just shows that the predictions about ITER seem to be in a realistic region.

You have that backwards.

The bad thing about fusion is that the power has to radiate through the surface of the reactor. That means that when you are at the engineering limit of what that wall can withstand, your volumetric power density decreases as you make the reactor larger.

This is unlike a fission reactor, where heat is transferred through the surfaces of large numbers of thin fuel pins, and where the surface area increases in proportion to the volume of the core.

Bigger being better is not a plus.

The best part to me:

> ... If engineers applied the same conditions and physics ...

& __physics__

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