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> How is fusion different? It's not but people don't seem to realize this or maybe just don't want to think about it. Spending $100B to produce 1GW of power (m
by cletus 5y ago
> How is fusion different?
It's not but people don't seem to realize this or maybe just don't want to think about it. Spending $100B to produce 1GW of power (made up numbers) is not an economical source of power. So hydrogen being free (deuterium and tritium are essentially free; Helium isotopes are more complicated) is irrelevant until the capital cost of the plane is much, much lower.
And even then you still have to deal with these significant issues:
- Neutron embrittlement of the container;
- Energy loss from the chamber from neutrons; and
- Containment. The plasma is essentially an extremely high temperature turbulent fluid. Because of the turbulence and the super-high temperatures containment is likely to remain a significant issue.
I hope fusion becomes commercially viable and economical but I'm just not convinced (yet) that that will ever be the case. It certainly won't be ITER even with tens of billions spent on it.
People get caught up on the fact that stars do fusion without considering what's different. To summarize:
- Energy loss from neutrons is essentially a non-issue because of gravity and just the size of stars. To put this in context, it's estimated that photons created at the Sun's core take ~30,000 years to escape;
- Stars are relatively inefficient with their fuel. IIRC the Sun converts ~4.5M tons of matter into energy every second. It sounds like a lot but that's a tiny fraction of the Sun's mass (~10^30 kg). That's because hydrogen atoms are so unlikely to fuse and they go through several intermediate states before that happens. Fusion in the lab already produces many more fusion reactions per unit mass than stars do.
I firmly believe that space-based solar power collection is our most likely future.
EDIT: corrected "photons"
- marktangotango 5y ago> I firmly believe that space-based solar power collection is our most likely future. Isn't this the same capital expenditure analysis your post starts with though? How many billions does it cost to get the solar panels to orbit in sufficient quantity? And ground stations to receive the energy beams (microwave presumably). This is where Musk/Spacex push for cheap kg to orbit really matter. Even in the 70's they worked out that mining the moon for raw materials to build space based solar was much more economical.
- cletus 5y agoSo during the Space Shuttle (and earlier) era I believe the cost of getting payloads to LEO was $20-50k/kg. Currently with Falcon 9 it's gone down to ~$1000/kg. I imagine this will continue to get cheaper with further reuse and Starship. But we really need to get down to <$10/kg. Thing is, that's entirely achievable. I believe the ultimate future here will be orbital rings [1]. Space elevators get a lot more attention and they really shouldn't because they're a lot less achievable and they require materials we haven't invented yet (to resist the centrifugal force). Imagine being able to take a cable car into orbit. That's what orbital rings promise and you need little more than copper wire and stainless steel. Not only would this bootstrap colonization of space but you can simply attach collectors to the ring itself and run the power down a cable to the ground so you don't even need to suffer the power loss from wireless transmission (which, for the record, is a practical method still). [1]: https://www.youtube.com/watch?v=LMbI6sk-62E https://www.youtube.com/watch?v=LMbI6sk-62E
- marktangotango 5y agoHa, I had not heard of orbital rings yet, thank you. My comment there is "who will think of the children/astronomers" parodying the simpsons. Although that applies space elevators as well. https://www.youtube.com/watch?v=RybNI0KB1bg https://www.youtube.com/watch?v=RybNI0KB1bg
- bigfudge 5y ago> photos created at the Sun's core take ~30,000 years to escape I’m guessing you meant photons but this still seems amazing. Is there somewhere I can find out more about that?
- whimsicalism 5y agoIt's not really "the same" photon though.
- deleted 5y ago[deleted]
- cletus 5y agoSo this is based on mathematical modeling. Here's one reference I found [1] that estimates 5,000 years. I know I've heard 30,000 too, which is really within the same order of magnitude. [1]: https://sciencing.com/fun-sun-moon-stars-8459789.html https://sciencing.com/fun-sun-moon-stars-8459789.html
- jhgb 5y agoWhen I was younger (like three decades ago), the number I was taught was something like two million years (if I remember it correctly; I might still be able to find that book if I'm lucky).
- 5y ago
- zpeti 5y ago$100bn to get to a working fusion reactor doesn’t mean the second one will cost €100bn as well…
- cletus 5y agoOh for sure. To be clear, I meant the amortized cost, not the initial cost of, say, ITER. I could've stated that better.
- nitrogen 5y agoEither way we (humanity) have to research these things or we are guaranteeing that we will reach an energy and materials plateau and eventual decline as a species.
- PaulDavisThe1st 5y agoThis makes no sense. A plateau does not imply decline.
- drran 5y agoYep, but if you want to have cheap energy, then it better to start with something cheaper, like LENR, which is still pain to reproduce, but give it $100bn and 20 years and then compare with ITER.
- pfdietz 5y agoAs long as we're in fantasyland I suggest perpetual motion machines, or perhaps unicorn power. It's hard to make up for LENR's lack of existence with clever engineering. But even if LENR existed, how do you think it would get around the problem described? LENR would make heat, low grade heat.
- drran 5y agoA low-grade heat is OK for heating of buildings, so it can replace natural. LENR is hard to reproduce even for those who can reproduce, but at this point we can be sure that LENR is not a fantasy land. Multiple scientists in multiple institutions are able to reproduce the experiment sometimes, so this is the science. IMHO, external factors are involved, e.g. cosmic rays, which generate muons[0], or radioactive elements or gases decaying, and LENR devices are just boosting them. [0]: https://en.wikipedia.org/wiki/Muon-catalyzed_fusion https://en.wikipedia.org/wiki/Muon-catalyzed_fusion
- chadcmulligan 5y agoHere's an article about why fusion is a bad idea [1] and its from the bulletin of atomic scientists so they should know. I'd love to hear it refuted but doesn't seem to have happened. [1] https://thebulletin.org/2017/04/fusion-reactors-not-what-theyre-cracked-up-to-be/ https://thebulletin.org/2017/04/fusion-reactors-not-what-the...
- thangalin 5y agohttps://www.youtube.com/watch?v=L0KuAx1COEk https://www.youtube.com/watch?v=L0KuAx1COEk https://www.reddit.com/r/fusion/comments/67rqqg/comment/dgtmuf5/?utm_source=share&utm_medium=web2x&context=3 https://www.reddit.com/r/fusion/comments/67rqqg/comment/dgtm... "For the record The Bulletin of Atomic Scientists is a [sic] anti-nuclear advocacy group. They often resort to fear mongering or using the straw man fallacy to advocate their point." https://news.ycombinator.com/item?id=14203206 https://news.ycombinator.com/item?id=14203206
- chadcmulligan 5y agoThats good, thanks