Today had some fairly cool space related stuff, starting with the first talk of the day, by Alan Hoffman of RPPL. His topic was Field Reversed Configurations, and he mentioned space propulsion as one of the applications. The nice thing about FRCs is that they include open field lines, which means the field lines are not circling the plasma, but exit the fusion device – all magnetic field lines are topologically circles, but there is an important distinction between lines that enclose plasma and ones that do not. Open field lines allow plasma to be expelled, providing propulsion. Obviously this is utterly useless if you don’t have net power gain in the reactor, but hey… Anyway, FRCs are a good candidate for the fusion power core in fusion powered spacecraft, if they ever materialize.

Another spacecraft relevant talk was Tom Intrator’s talk on Magnetized Target Fusion, which involves compressing a target plasma inside a conductive shell. MTF is something of a hybrid between traditional magnetic confinement and inertial confinement. Interestingly the current favored plasma configuration for the MTF target plasma is a field reversed configuration. The reason that MTF is spaceflight relevant is that it holds the promise of delivering the hoped-for pure fusion thermonuclear explosive that Dyson and collaborators anticipated when they began work on Orion.

I had a chance to talk to Artan Qerushi, who is working for TriAlpha Energy (sorry, no link). The big deal here is that TriAlpha has venture funding and is building a research reactor to explore their concept, which uses an FRC and ion beams to fuse protons with Boron-11. It’s widely believed in the fusion community that bremsstrahlung losses (basically electromagnetic radiation emitted due to collisions) kill the possibility of doing p-B11 fusion, but after considerable discussion with Artan I’ve come to believe that the Colliding Beam Fusion Reactor violates the assumptions which go into the bremstrahlung loss analysis without violating any laws of physics. There’s plenty of room for the idea to be tripped up, but nothing obvious that threatens to kill it – this is not cold fusion. The outstanding news is that there is someone credible building a fusion machine with venture capital funding.

One last thing – I blithely blew off heavy ion fusion earlier. It turns out I was wrong, and there are people working seriously on it, though not as many as are working on laser ICF. Based on talks today it looks like ICF will break even in the next 15 years or so. Still lots of problems to work out before it can be commecialized, though.