Revamped German stellarator should run longer, hotter and compete with tokamaks

Post by pfdietz » Sun, Sep 11, 2022, 8:03 PM UTC

GordonS wrote: post #91

pfdietz wrote: post #53

Earlier quoted context omitted.

DT fusion would be just ridiculous for space flight. Anything a DT reactor could do a fission reactor could do much better -- much smaller, much higher power density, much less complexity. And similarly for use in ships down here on Earth. In practice, synfuels would be better than either for ships on Earth.

I don't understand this; if fission reactors were "better", we wouldn't be pouring so much into fusion? Also, if it makes a difference, I didn't mean we'd be bolting a first gen tokamak to a container ship; I meant, much later down the line, if we were able to miniaturise (similar to how we have nuclear powered subs and ice breakers).

Post by GordonS » Sun, Sep 11, 2022, 8:19 PM UTC

pfdietz wrote: post #101

GordonS wrote: post #91

Earlier quoted context omitted.

I don't understand this; if fission reactors were "better", we wouldn't be pouring so much into fusion? Also, if it makes a difference, I didn't mean we'd be bolting a first gen tokamak to a container ship; I meant, much later down the line, if we were able to miniaturise (similar to how we have nuclear powered subs and ice breakers).

You seem to think that government decisions are rational. Fusion is a meme technology. People just have this assumption that's it's valuable, without having rationally arrived at that conclusion (which, when you examine it in detail, is very difficult to justify.) I suspect this was because it started back in the 1950s when consent was easier to manufacture and nuclear was being pushed. Fission lost that glamour with…

Post by pfdietz » Sun, Sep 11, 2022, 8:24 PM UTC

GordonS wrote: post #103

pfdietz wrote: post #101

Earlier quoted context omitted.

You seem to think that government decisions are rational. Fusion is a meme technology. People just have this assumption that's it's valuable, without having rationally arrived at that conclusion (which, when you examine it in detail, is very difficult to justify.) I suspect this was because it started back in the 1950s when consent was easier to manufacture and nuclear was being pushed. Fission lost that glamour with…

It's not only governments pouring cash in, but private equity too. With all due respect, it seems ridiculous to me that fusion is a "meme technology" - aside from money, are all those many thousands of scientists really working on a technology they know can't work?

Post by Retric » Sun, Sep 11, 2022, 9:28 PM UTC

mjhay wrote: post #64

marcosdumay wrote: post #56

Earlier quoted context omitted.

> but I'm not convinced fusion will ever be economically feasible Not on Earth. But put a good enough fusion reactor on a rocket, and you can reach neighboring stars in 3 or 4 decades instead of the 15 one would expect for fission. (Of course, nobody is even sure reactors can get that good, but it does look possible.)

Fission fragment rockets could actually compete with fusion here. The reaction mass is the fission fragments themselves, which could get a specific impulse of around 10^6 s. The technology to do this is within relatively easy reach, at least by interstellar rocket standards. https://en.wikipedia.org/wiki/Fission-fragment_rocket

Post by exitheone » Sun, Sep 11, 2022, 10:27 PM UTC

Maken wrote: post #15

dleslie wrote: post #6

Forgive my ignorance; what with all the effort made to isolate the exceedingly hot plasma from connecting with any surface, what are the plans to extract the heat in order to generate power?

Because no known material can withstand direct contact with the plasma. Even with the air gap the walls require a cooling system, and therefore a continuous hot stream of fluid will be generated like in any other thermal power plant. However, at the stage fusion research is, the main problem is figuring how to create a device to keep the plasma fluid stable for long periods of time. As far as I know, none of the exis…