Merged How Close is power from Nuclear Fusion

There was a time in my life when I expected to see useful fusion reactors come on line in my lifetime. Now, at age 68 I no longer expect that.
 
theprestige said:
Fusion seems to have a slightly different problem, in that there are precursor technologies that need to develop/mature, and it's not clear how long that's going to take or how much it will cost to speed up the process.
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There appear to be many people working on all sorts of possible solutions.. Maybe just the size of the effort well eventually give us a breakthrough. Or not, as the case may be.
 
Nuclear Fusion Breakthrough Confirmed: California Team Achieved Ignition

A major breakthrough in nuclear fusion has been confirmed a year after it was achieved at a laboratory in California.

Researchers at Lawrence Livermore National Laboratory's (LLNL's) National Ignition Facility (NIF) recorded the first case of ignition on August 8, 2021, the results of which have now been published in three peer-reviewed papers.
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This is fantastic! Now we're only 19 years away from fusion power!
 
theprestige said:
Actually it sounds like a major breakthrough. Why sneer instead of celebrate?
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There is a lot to question here.

The article cited by shemp says
Once the hydrogen plasma "ignites", the fusion reaction becomes self-sustaining, with the fusions themselves producing enough power to maintain the temperature without external heating.
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This reaction apparently lasted 100 trillionths of a second. Does that qualify as self sustaining? Looks to me like it didn't sustain but the actual situation is they claim it produced enough energy to sustain.

But that is suspect too. The energy measurements for this vary quite a bit. Some sources cite that it took 10 times as much energy to make this happened as was produced. Other put the ratio at over 250 to 1. Obviously you can't build a sustaining cycle with those kinds of losses.

Also seems they haven't been able to reproduce this yet.

Breakthrough of some kind I hope, but really hard to tell. Solid facts seem hard to come by.

ETA: I should point out I haven't read the three papers yet, but the summaries I've read and heard about don't contradict the things I just cited. My understanding is that they simply confirm that the 100 trillionth of a second reaction actually occurred.
 
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RecoveringYuppy said:
This reaction apparently lasted 100 trillionths of a second. Does that qualify as self sustaining?
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It does if you only gave it 100 trillionths of a second of fuel to use up. It's just a type of positive feedback, and positive feedback reactions end whenever the conditions they depend on to keep feeding back change.

RecoveringYuppy said:
Some sources cite that it took 10 times as much energy to make this happened as was produced. Other put the ratio at over 250 to 1.
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This kind of variation results from differences in what gets counted as input and what doesn't. There are multiple stages to setting up this kind of thing, which don't all have equal claims to being part of the input energy. For an analogy, consider a fire created at a fire-fighting school which destroys a house which was built just to be burned. Is the input energy the energy released by the ignition system alone? (I'd say "match" but I'm sure they don't use a match for this.) What about the energy it took to first get the ignition system up and running (striking the match)? What about the energy it took to produce the match? What about the energy it took to build the house? (A successful run of a fusion power plant would probably radiate parts of the machinery to death pretty quickly, causing the need to at least partially rebuild it before the next run.) After posting this, I'll try to find a Sabine Hossenfelder video which explained the differences between different fusion input energy levels in more detail than I'm recalling at the moment. I think there were a few different standard ways look at it called Q1, Q2, & Q3. (Part of her point was that the one that sounds the most optimistic is the one that gets published the most.)

RecoveringYuppy said:
Obviously you can't build a sustaining cycle with those kinds of losses.
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Actually you can. You just wouldn't want to other than for research. Sustaining (positive feedback) and input/output ratio are two different things.
 
Delvo, thanks for the Hossenfelder youtube. That is exactly what I was getting at and applies big time here.

RecoveringYuppy said:
This reaction apparently lasted 100 trillionths of a second. Does that qualify as self sustaining?
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Delvo said:
It does if you only gave it 100 trillionths of a second of fuel to use up. It's just a type of positive feedback, and positive feedback reactions end whenever the conditions they depend on to keep feeding back change.
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That doesn't make sense to meat all. This is an inertial confinement laser induced facility. Fusion reactors based on that process would be cyclic pulses with energy from the last pulse. This while methodology isn't even aiming for a self sustaining reaction.

Delvo said:
This kind of variation results from differences in what gets counted as input and what doesn't.
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Yes, of course. You've gone on to amplify my point especially with the youtube video. It was exactly the one I was trying remember late last night when I posted.

I can't think of any interpretation of "self sustaining" that it is at all accurate here. All the points that Hossenfelder made apply here plus the fact that this isn't even a methodology aiming for self sustaining reactions.

Your fire analogy is spot on, except it's spot on as an example of exactly what this didn't do.
 
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Maybe we could build a power plant next to the sun, use a grid of satellites to transfer power via lasers, hook the last one up to a space elevator, and transfer the power down to earth.

An added bonus is that any aliens who get weird readings about our solar system will wonder what the hell the idiots are up to.
 
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It seems like I see headlines about some fusion "breakthough" several times a year. I don't think it means that actual usable fusion energy is coming any time soon. It's always some kind of research and development step. They have yet to hook up a boiler and a turbine to one of these experiments. Also, it's going to be insanely expensive I bet.
 
Puppycow said:
It seems like I see headlines about some fusion "breakthough" several times a year. I don't think it means that actual usable fusion energy is coming any time soon. It's always some kind of research and development step. They have yet to hook up a boiler and a turbine to one of these experiments. Also, it's going to be insanely expensive I bet.
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Yes. Even if/when it becomes possible to make something very hot for a significant period of time, that heat still has to be turned into a useful for of energy (starting with steam I would guess). Some significant engineering will be required.
 
Did you notice the date on that? That's the event we just discussed. See Shemp's post above.
 
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