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Honest question: Has man-made nuclear fusion ever happened? Or is it theory, happening on the sun?

jhomedall 6y ago
Hydrogen bombs use fusion.
correct_horse 6y ago
Nuclear fusion happens in man-made thermonuclear bombs. I believe it also happens in research reactors that require more energy than they produce due to various inefficiencies.
cweagans 6y ago
Fusion is relatively easy to achieve. Farnsworth and Hirsch did it back in the 60s and there's a community of people building DIY fusors at home. The hard part is getting the reaction to produce more energy than it requires to sustain. Given a breakthrough that solves that problem, fusion would be a really appealing energy source given the abundance of hydrogen.
mchusma 6y ago
Yes man-made nuclear fusion is quite "easy". The hard part is getting more energy out than you put in. The sun does this all the time, basically by having so much mass that hydrogen gets sucked in by gravity to collide with other particles. Keeping hydrogen close enough to smash into each other is hard, the sun is just so big that it can do that. Hydrogen bombs do this by using other explosives to push hydrogen together. This isn't a good power source. We can't use gravity to cause hydrogen to collide here on earth (we have no artificial gravity). But we have magnets, so we try to bounce hydrogen particles around super fast in a small space with magnets instead of using gravity. Now getting more energy out is a bit like starting a fire. You need to apply heat for a while with a lighter before the fuel ignites, then the burning fuel keeps releasing energy. Same basic idea with fusion. You put in energy to start fusing hydrogen. Once the hydrogen is releasing power, it will cause other hydrogen particles to bounce around super fast and continue fusing, releasing more energy. The part that hasn't really been done yet is proving that the "fire" can stay lit, and that is what people are trying to do. It's hard for a bunch of reasons, but the theme is "making a tiny sun-like place on earth is challenging". When this article mentions "q" that is what it is referring to. q=2 means for every joule of energy put in you get 2 joules out. (disclaimer: this is a quick version that omits a lot)
- kamaal 6y ago
  >>The hard part is getting more energy out than you put in. I thought this was impossible due to law of conservation of energy. Well eventually we get lucky with things like gravity, and water cycles doing the work for us by giving us rivers and we build a dam around it. But you can never design a process where you can take more than what you put in.
  - tuatoru 6y ago
    You're forgetting the mass-energy equivalence, E = mc^2. Both fission and fusion are elaborate ways of converting a small fraction of the mass of the fuel to energy. Also, "you can't get more than you put in" applies to closed systems. Reactors are open systems.
_ph_ 6y ago
Yes, it has. Setting aside hydrogen bombs, the predecessor of ITER, JET has achieved nuclear fusion. To do so, it has used more electricity than it generated, but it maintained fusion and generated electricity. ITER is supposed to achieve a net gain of electricity.
ceejayoz 6y ago
You can fuse atoms at home. https://en.wikipedia.org/wiki/Fusor https://en.wikipedia.org/wiki/Fusor

Hydrogen bombs use fusion.

Nuclear fusion happens in man-made thermonuclear bombs. I believe it also happens in research reactors that require more energy than they produce due to various inefficiencies.

cweagans 6y ago

Fusion is relatively easy to achieve. Farnsworth and Hirsch did it back in the 60s and there's a community of people building DIY fusors at home. The hard part is getting the reaction to produce more energy than it requires to sustain. Given a breakthrough that solves that problem, fusion would be a really appealing energy source given the abundance of hydrogen.

mchusma 6y ago

Yes man-made nuclear fusion is quite "easy". The hard part is getting more energy out than you put in. The sun does this all the time, basically by having so much mass that hydrogen gets sucked in by gravity to collide with other particles. Keeping hydrogen close enough to smash into each other is hard, the sun is just so big that it can do that. Hydrogen bombs do this by using other explosives to push hydrogen together. This isn't a good power source. We can't use gravity to cause hydrogen to collide here on earth (we have no artificial gravity). But we have magnets, so we try to bounce hydrogen particles around super fast in a small space with magnets instead of using gravity. Now getting more energy out is a bit like starting a fire. You need to apply heat for a while with a lighter before the fuel ignites, then the burning fuel keeps releasing energy. Same basic idea with fusion. You put in energy to start fusing hydrogen. Once the hydrogen is releasing power, it will cause other hydrogen particles to bounce around super fast and continue fusing, releasing more energy. The part that hasn't really been done yet is proving that the "fire" can stay lit, and that is what people are trying to do. It's hard for a bunch of reasons, but the theme is "making a tiny sun-like place on earth is challenging". When this article mentions "q" that is what it is referring to. q=2 means for every joule of energy put in you get 2 joules out. (disclaimer: this is a quick version that omits a lot)

kamaal 6y ago
>>The hard part is getting more energy out than you put in. I thought this was impossible due to law of conservation of energy. Well eventually we get lucky with things like gravity, and water cycles doing the work for us by giving us rivers and we build a dam around it. But you can never design a process where you can take more than what you put in.
- tuatoru 6y ago
  You're forgetting the mass-energy equivalence, E = mc^2. Both fission and fusion are elaborate ways of converting a small fraction of the mass of the fuel to energy. Also, "you can't get more than you put in" applies to closed systems. Reactors are open systems.

_ph_ 6y ago

Yes, it has. Setting aside hydrogen bombs, the predecessor of ITER, JET has achieved nuclear fusion. To do so, it has used more electricity than it generated, but it maintained fusion and generated electricity. ITER is supposed to achieve a net gain of electricity.

ceejayoz 6y ago

You can fuse atoms at home. https://en.wikipedia.org/wiki/Fusor https://en.wikipedia.org/wiki/Fusor