MHD

From AVI's pointer to Construction Physics I wound up looking over Yamata-1, and then wondering about MHD electricity generation, since the initial article said 20T magnets were lighter and cheaper. Cool idea--propel your ship using electromagnetic forces on seawater. You can guess some of the problems easily.

Maybe that would make MHD generation more feasible too.

MHD electricity generation gives more bang at higher fluid speeds, so post-boiler exhaust isn't ideal. Using a "flame"(*) to put a plasma through a strong magnetic field would tend to push positive ions to one side and negative to the other, to be captured by respective sets of electrodes to produce DC current.

The devil is in the details, of course--said hot plasma is apt to be good at eroding the electrodes. I'm getting tired and going to call the research quits for tonight, but I wonder if injecting streams of cold gas to flow along the walls of the expansion MHD chamber would help protect the electrodes.

That would increase the resistance, of course, but might be worth it.

I don't doubt somebody else has tried this already.

(*) You can find youtube videos of people trying MHD with a small rocket motor.