I dont think that this is more feasible than John Sloughs FRC- imploding liner concept and that one is already pretty far along.http://forum.nasaspaceflight.com/index.php?topic=30437.150
Since Sandia already has a bigger device, I do have to wonder about the merrits of additional tests with this smaller machine.
Yeah, the description of this project on the contest page doesn't say why this particular research is any different from the much bigger and better-funded z-pinch research going on elsewhere. The description doesn't even acknowledge any other research programs. Either it is an inferior copy of the other programs, with nothing new to add, or it has some novelty that the contest page completely fails to address.
Also, the focus on spacecraft propulsion is misguided. If they can really create a practical pulsed-fusion propulsion module, then they can get over-unity from a fusion reaction and that can easily be turned into the long-sought fusion electrical power generation solution that will have far, far more impact in the immediate future than a new spacecraft propulsion system.
Quote from: ChrisWilson68 on 06/23/2013 08:38 amAlso, the focus on spacecraft propulsion is misguided. If they can really create a practical pulsed-fusion propulsion module, then they can get over-unity from a fusion reaction and that can easily be turned into the long-sought fusion electrical power generation solution that will have far, far more impact in the immediate future than a new spacecraft propulsion system.That I am not so sure about. Fusion for space propulsion does not have to economically compete with coal. Terrestrial fusion does. E.g. I dont think that inertial confinement fusion like the NIF will ever be able to be economical. A gold plated fuel hohlraum that has to be replaced for every shot does not sound very economical to me. Plus, I dont see how they will be able to breed tritium in a device with such an architecture.The z- pinch might work a little better in some respects, but it still sounds quite complex. Even tokamaks might never result in economical reactors (but its really good science). For the same reason MSNW has two rather different concepts for space propulsion and terrestrial power generation. Anyway, the question remains what this z- pinch project will do better than Sandias z- machine that warrants it to be funded.
OK, that's a good point. It would be possible to have a space fusion drive even if the electricity-generation version wasn't competitive with coal. Still, it would at the very least be a lot closer to being viable as an electrical power source than any current fusion project, and a lot of money is going into those other fusion programs.
The novelty in this research is that it will utilize lithium deuteride as the fuel source.
The novelty in this research is that it will utilize lithium deuteride as the fuel source. Since this material exists as a solid at room temperatures, we expect the reactivities to be much higher than the gas fed deuterium experiments. The only other pulsed power effort experimenting with lithium deuteride was from 1962 when they tested single exploding wires on a z-pinch machine much less powerful than the Charger-1. Besides the much higher densities of the fuel, it is in great abundance and relatively low cost compared to other approaches which may require deuterium tritium or deuterium helium-3 reactions. Both tritium and helum-3 would require a major infrastructure for production that does not exist in order to produce the tons needed for a single mission, and the fusion fuel cost would greatly exceed the launch cost. Therefore, this can be seen as a more pragmatic approach to the problem.The operating costs of running lithium deuteride experiments with the Charger-1 is expected to cost about $5000 to $10,000 per week. The z-machine at Sandia Labs would cost up to 100 times this. We can do many more experiments towards understanding the optimization and scaling with lithium deuteride targets, and help guide the design of similar targets for more powerful machines. There are more problems to be solved than can be realistically solved by one group alone, and collaboration with as many groups as necessary is vital in order to design and build a fusion propulsion system.
While I do somewhat understand why the lithium deuteride might be a better fuel than Deuterium gas for an inertial fusion device, I am not exactly sure why exactly it would work better than D+T for achieving fusion. In fact the crosssection of D+Li is almost as low (and I believe the power density is even lower) as P+B11 but is not as aneutronic due to the D+D (and probably also D+T and T+He4) side reactions.
Is the Li mostly meant to breed T for D-T fusion like in hydrogen bombs?6Li + n -> T + He + 4.784 MeV7Li + n -> T + He + n - 2.467 MeV
And because lithium deuteride exists as a solid at room temperature, we expect higher reaction rates even though the cross section is lower.
Quote from: Elmar Moelzer on 06/24/2013 10:13 pmQuote from: Kschultz on 06/24/2013 04:16 pmThe novelty in this research is that it will utilize lithium deuteride as the fuel source. Since this material exists as a solid at room temperatures, we expect the reactivities to be much higher than the gas fed deuterium experiments. The only other pulsed power effort experimenting with lithium deuteride was from 1962 when they tested single exploding wires on a z-pinch machine much less powerful than the Charger-1. Besides the much higher densities of the fuel, it is in great abundance and relatively low cost compared to other approaches which may require deuterium tritium or deuterium helium-3 reactions. Both tritium and helum-3 would require a major infrastructure for production that does not exist in order to produce the tons needed for a single mission, and the fusion fuel cost would greatly exceed the launch cost. Therefore, this can be seen as a more pragmatic approach to the problem.The operating costs of running lithium deuteride experiments with the Charger-1 is expected to cost about $5000 to $10,000 per week. The z-machine at Sandia Labs would cost up to 100 times this. We can do many more experiments towards understanding the optimization and scaling with lithium deuteride targets, and help guide the design of similar targets for more powerful machines. There are more problems to be solved than can be realistically solved by one group alone, and collaboration with as many groups as necessary is vital in order to design and build a fusion propulsion system. Thanks for the information! That is indeed interesting to know and might change my opinion on the project. While I do somewhat understand why the lithium deuteride might be a better fuel than Deuterium gas for an inertial fusion device, I am not exactly sure why exactly it would work better than D+T for achieving fusion. In fact the crosssection of D+Li is almost as low (and I believe the power density is even lower) as P+B11 but is not as aneutronic due to the D+D (and probably also D+T and T+He4) side reactions. Can you give us some more details on that?Part of the reason we're using lithium deuteride and not deuterium tritium is because tritium is rare, expensive, and radioactive. And because lithium deuteride exists as a solid at room temperature, we expect higher reaction rates even though the cross section is lower. In addition to this, we do plan on breeding tritium from neutron lithium reactions, which we can then provide to research groups that are pursuing deuterium tritium fusion. Collaboration like this is what's really vital for making fusion work.
Quote from: Kschultz on 06/24/2013 04:16 pmThe novelty in this research is that it will utilize lithium deuteride as the fuel source. Since this material exists as a solid at room temperatures, we expect the reactivities to be much higher than the gas fed deuterium experiments. The only other pulsed power effort experimenting with lithium deuteride was from 1962 when they tested single exploding wires on a z-pinch machine much less powerful than the Charger-1. Besides the much higher densities of the fuel, it is in great abundance and relatively low cost compared to other approaches which may require deuterium tritium or deuterium helium-3 reactions. Both tritium and helum-3 would require a major infrastructure for production that does not exist in order to produce the tons needed for a single mission, and the fusion fuel cost would greatly exceed the launch cost. Therefore, this can be seen as a more pragmatic approach to the problem.The operating costs of running lithium deuteride experiments with the Charger-1 is expected to cost about $5000 to $10,000 per week. The z-machine at Sandia Labs would cost up to 100 times this. We can do many more experiments towards understanding the optimization and scaling with lithium deuteride targets, and help guide the design of similar targets for more powerful machines. There are more problems to be solved than can be realistically solved by one group alone, and collaboration with as many groups as necessary is vital in order to design and build a fusion propulsion system. Thanks for the information! That is indeed interesting to know and might change my opinion on the project. While I do somewhat understand why the lithium deuteride might be a better fuel than Deuterium gas for an inertial fusion device, I am not exactly sure why exactly it would work better than D+T for achieving fusion. In fact the crosssection of D+Li is almost as low (and I believe the power density is even lower) as P+B11 but is not as aneutronic due to the D+D (and probably also D+T and T+He4) side reactions. Can you give us some more details on that?
Yes and no. D + Li itself is about as hard (harder) to burn as PB11. The D+T and D+D side reactions might be what you really want. If you can do D+Li, you should theoretically be able to do PB11 also and the latter is considered the holy grail of nuclear fusion.
Quote from: Elmar Moelzer on 06/26/2013 12:31 amYes and no. D + Li itself is about as hard (harder) to burn as PB11. The D+T and D+D side reactions might be what you really want. If you can do D+Li, you should theoretically be able to do PB11 also and the latter is considered the holy grail of nuclear fusion.While p-B11 is a great reaction, we still expect to get higher reaction rates from D+Li. The reason again is because D+Li is a solid, whereas p-B11 would be a gas-puff system.
