how to build a fusion reactor, part two
Apr. 5th, 2007 09:05 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
zwolYeah, that was a long five PM seminar. Sorry.
In part one I explained how the basic problem with fusion reactors is not so much making the hydrogen fuse as getting the return energy out in a useful form, and I suggested that the problem is the use of the wrong fundamental force. Electromagnetism just doesn't work so well when you're trying to stop neutrons. (Or gamma rays.) The short-range forces are no use either, and that leaves us with gravity.
Gravity's ideal for our purposes, really: it's long range and it can pull on everything coming out of the reaction. I suggest that what you want for this job is a long tube with the fusion reaction in the middle. The gravity field inside the tube acts like a black hole radially, so nothing gets out the sides of the tube. Axially, the field is much weaker, so particles can travel away from the reaction zone, but (this is actually pretty easy) it's constant. As particles travel down the tube they thus deposit more and more of their energy into the gravity field. You tune the field intensity and the length of the tube so that by the time the particles get to the ends, the photons have all been Dopplered down to microwave frequencies, the matter is moving at room-temperature speeds, and the neutrons have decayed into proton-electron pairs. You cut the gravity field off entirely at the end of the tube, absorb the microwaves with an antenna, and you just have hydrogen and helium gas coming out. Meantime, the energy has all fed back through your gravity generator and been converted into electricity.
Yes, I admit, this does require a gravity generator, and not just any gravity generator either. The field I described could be produced by a spatial distribution of non-exotic matter — you don't need negative mass anywhere — but you would never be able to get it to hold its shape. Furthermore, the gravity generator needs to run on only a fraction of the energy coming out of the reaction. And, most important of all, energy deposited into the field needs to be extractable as electricity. There's no point doing all this otherwise.
Still, if you can do artificial gravity for your spaceship's decks, I don't see why you can't do this too. And it has the nice feature that it'll make the hydrogen fuse in the first place, too. Gravitational confinement: it works for the Sun.
In part one I explained how the basic problem with fusion reactors is not so much making the hydrogen fuse as getting the return energy out in a useful form, and I suggested that the problem is the use of the wrong fundamental force. Electromagnetism just doesn't work so well when you're trying to stop neutrons. (Or gamma rays.) The short-range forces are no use either, and that leaves us with gravity.
Gravity's ideal for our purposes, really: it's long range and it can pull on everything coming out of the reaction. I suggest that what you want for this job is a long tube with the fusion reaction in the middle. The gravity field inside the tube acts like a black hole radially, so nothing gets out the sides of the tube. Axially, the field is much weaker, so particles can travel away from the reaction zone, but (this is actually pretty easy) it's constant. As particles travel down the tube they thus deposit more and more of their energy into the gravity field. You tune the field intensity and the length of the tube so that by the time the particles get to the ends, the photons have all been Dopplered down to microwave frequencies, the matter is moving at room-temperature speeds, and the neutrons have decayed into proton-electron pairs. You cut the gravity field off entirely at the end of the tube, absorb the microwaves with an antenna, and you just have hydrogen and helium gas coming out. Meantime, the energy has all fed back through your gravity generator and been converted into electricity.
Yes, I admit, this does require a gravity generator, and not just any gravity generator either. The field I described could be produced by a spatial distribution of non-exotic matter — you don't need negative mass anywhere — but you would never be able to get it to hold its shape. Furthermore, the gravity generator needs to run on only a fraction of the energy coming out of the reaction. And, most important of all, energy deposited into the field needs to be extractable as electricity. There's no point doing all this otherwise.
Still, if you can do artificial gravity for your spaceship's decks, I don't see why you can't do this too. And it has the nice feature that it'll make the hydrogen fuse in the first place, too. Gravitational confinement: it works for the Sun.
