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>No, it isn't. We think it's possible because we have extensive experimental data on fusion reactions from Earthbound experiments. From those experiments we kno

>No, it isn't. We think it's possible because we have extensive experimental data on fusion reactions from Earthbound experiments. From those experiments we know a wide range of possible conditions that can produce sustained, controlled fusion. There is zero evidence sustained, controlled, above break-even fusion works at the types of energy densities people talk about for power plants. None; keine, zero, zilch: there is arguably as much evidence for this as the existence of ghosts or leprechauns. The models don't work! I ain't saying we shouldn't try, but there are by now reasonable arguments to be made that it's a big waste of time and money better spent on something boring that we know will work, like thorium. To make another technological analogy from nature: if the earth's gravitational potential well were larger, we wouldn't have been able to achieve orbit using chemical rockets. The specific impulse of fuels which exist in the periodic table of the elements would have been insufficient to achieve this. For example: https://arxiv.org/abs/1804.04727 https://arxiv.org/abs/1804.04727 -similarly, the properties of plasmas may make it impossible to achieve controlled, above break-even nuclear fusion in a conveniently small and dense volume. There is at present no evidence that it can be achieved. They've been working on it for 65 or 70 years now depending on how you count things, you'd think there would be some positive indications by now beyond optimistic press releases. As for your wishful thinking that a controlled nuclear fusion technology couldn't be used as a weapon, well, there you go again with that wishful thinking. Controlled fusion is a non-proliferation nightmare. Should this actually come to pass and become routine enough to be a meaningful part of the power grid, it will be a hell of a lot easier to build a fusion howitzer than an ICBM with H bomb at the business end of it. I mean, you're a nuclear physicist, man!

pdonis 7y ago
> There is zero evidence sustained, controlled, above break-even fusion works at the types of energy densities people talk about for power plants. This is just another way of saying we haven't gotten it to work yet. That's true, we haven't. The same could have been said about controlled fission in 1941. > there are by now reasonable arguments to be made that it's a big waste of time and money better spent on something boring that we know will work, like thorium. I agree there are reasonable arguments to be made about this. But comparing controlled fusion to ghosts and leprechauns is not one of them. > it will be a hell of a lot easier to build a fusion howitzer I have no idea where you're getting this from. Again, I really don't think you've grasped the implications of the fact that the energy content of the fuel inside a reactor producing, say, a gigawatt of power, is the same whether the reactor is fueled by coal, oil, natural gas, or fusion. So a "fusion howitzer" based on a fusion reactor would have no more explosive power than a chemical explosive howitzer (which is not based on a coal, oil, or natural gas plant anyway, it's a very different thing). Nuclear fission is a unique case here because of the historical accident of fission power developing in such a way that multiple years' worth of fuel, containing orders of magnitude more stored energy than was being burned at any given time, was all inside the reactor core at once, instead of the reactor having fuel continually injected just in time to be burned, like every other kind of reactor. All of the downsides of fission--the possibility of meltdown, decay heat removal, huge spent fuel pools containing lots of long-lived radioisotopes, even an accident like Chernobyl--are due to this unique attribute. Newer designs like pebble bed reactors have shown that this is not a necessary attribute of fission power. But it won't be an attribute of fusion power at all.
- scottlocklin 7y ago
  People claim to have seen ghosts and leprechauns. Nobody's claiming to have seen break even. Only "if you give me enough money you'll see it." Which one could say about ghosts and leprechauns also. The difference between the energy content of a coal reactor and a hypothetical fusion reactor: you can store a lot more gigawatts in the back of a pickup truck for one of them, and that is the one that makes enough neutrons to sterilize a city block when you burn them up. I mean, how many pounds of fusion fuel does it take to level a city?
  - pdonis 7y ago
    > Nobody's claiming to have seen break even. Huh? That milestone was reached some years ago. https://www.livescience.com/43318-fusion-energy-reaches-milestone.html https://www.livescience.com/43318-fusion-energy-reaches-mile... What has not yet been achieved is ignition--a self-sustaining reaction that does not require continuous energy input. > how many pounds of fusion fuel does it take to level a city? We already know how to make a fusion reaction that will level a city. Having a working controlled fusion reactor would not affect our capability to level cities. So I really don't understand why you keep harping on this.
    - scottlocklin 7y ago
      Because you can put the energy required to level a city in the back of a pickup truck, then level a city with it using the same technology has a hypothetical fusion reactor possible, that's why. I don't know why you can't see the destructive potential of a project Daedelus with the business end aimed at Los Angeles. The NIF result created 35000 neutrons, and you should know that press release is the functional definition of a scientific fraud -I wrote a couple of articles on it which you can go find if you care about fraud.
      - pdonis 7y ago
        > Because you can put the energy required to level a city in the back of a pickup truck Yes, we can already do this, it's called a fusion bomb. > then level a city with it using the same technology has a hypothetical fusion reactor possible No, a bomb is not the same as a fusion reactor. A bomb burns a megaton of TNT's worth of fusion fuel all at once. A fusion reactor outputting a gigawatt of power burns the same amount of fuel in about a year. It's not at all the same thing.

pdonis 7y ago

> There is zero evidence sustained, controlled, above break-even fusion works at the types of energy densities people talk about for power plants. This is just another way of saying we haven't gotten it to work yet. That's true, we haven't. The same could have been said about controlled fission in 1941. > there are by now reasonable arguments to be made that it's a big waste of time and money better spent on something boring that we know will work, like thorium. I agree there are reasonable arguments to be made about this. But comparing controlled fusion to ghosts and leprechauns is not one of them. > it will be a hell of a lot easier to build a fusion howitzer I have no idea where you're getting this from. Again, I really don't think you've grasped the implications of the fact that the energy content of the fuel inside a reactor producing, say, a gigawatt of power, is the same whether the reactor is fueled by coal, oil, natural gas, or fusion. So a "fusion howitzer" based on a fusion reactor would have no more explosive power than a chemical explosive howitzer (which is not based on a coal, oil, or natural gas plant anyway, it's a very different thing). Nuclear fission is a unique case here because of the historical accident of fission power developing in such a way that multiple years' worth of fuel, containing orders of magnitude more stored energy than was being burned at any given time, was all inside the reactor core at once, instead of the reactor having fuel continually injected just in time to be burned, like every other kind of reactor. All of the downsides of fission--the possibility of meltdown, decay heat removal, huge spent fuel pools containing lots of long-lived radioisotopes, even an accident like Chernobyl--are due to this unique attribute. Newer designs like pebble bed reactors have shown that this is not a necessary attribute of fission power. But it won't be an attribute of fusion power at all.

scottlocklin 7y ago
People claim to have seen ghosts and leprechauns. Nobody's claiming to have seen break even. Only "if you give me enough money you'll see it." Which one could say about ghosts and leprechauns also. The difference between the energy content of a coal reactor and a hypothetical fusion reactor: you can store a lot more gigawatts in the back of a pickup truck for one of them, and that is the one that makes enough neutrons to sterilize a city block when you burn them up. I mean, how many pounds of fusion fuel does it take to level a city?
- pdonis 7y ago
  > Nobody's claiming to have seen break even. Huh? That milestone was reached some years ago. https://www.livescience.com/43318-fusion-energy-reaches-milestone.html https://www.livescience.com/43318-fusion-energy-reaches-mile... What has not yet been achieved is ignition--a self-sustaining reaction that does not require continuous energy input. > how many pounds of fusion fuel does it take to level a city? We already know how to make a fusion reaction that will level a city. Having a working controlled fusion reactor would not affect our capability to level cities. So I really don't understand why you keep harping on this.
  - scottlocklin 7y ago
    Because you can put the energy required to level a city in the back of a pickup truck, then level a city with it using the same technology has a hypothetical fusion reactor possible, that's why. I don't know why you can't see the destructive potential of a project Daedelus with the business end aimed at Los Angeles. The NIF result created 35000 neutrons, and you should know that press release is the functional definition of a scientific fraud -I wrote a couple of articles on it which you can go find if you care about fraud.
    - pdonis 7y ago
      > Because you can put the energy required to level a city in the back of a pickup truck Yes, we can already do this, it's called a fusion bomb. > then level a city with it using the same technology has a hypothetical fusion reactor possible No, a bomb is not the same as a fusion reactor. A bomb burns a megaton of TNT's worth of fusion fuel all at once. A fusion reactor outputting a gigawatt of power burns the same amount of fuel in about a year. It's not at all the same thing.