@Neal yes we of course only learn years later of the newest inventions, no navy wants to give away its advantgages, or hints on how their system works.
@Aktungbby: Interesting links, thanks!
I thought the rim-driven impeller maybe with a stator and a rotor, where the inner moving part (screw) does not even need a coil but just has to be made of a metal 'core' looks promising. Less maintenance, well, as long as the coil in the outer rim is ok, otherwise changing the whole thing might be a nightmare, maintenance-wise.
There are numerous advantages though because there does not have to be any rotary shaft seals, indeed no shaft leaving the hull altogether.
The screw should be much longer though, and have no tips at all, just like the churro example, something we discussed back then. We thought of a "flat" Archimedes-like screw where revolutions probably could not have been counted, moving within a hollow cylinder or tube. Or something looking like those Colani-aircraft propellers, adapted for underwater dynamics.
Interesting that they now think of a "churro" extending over the whole submarine, i wonder how this design would look like. Maybe with a tube running through the whole of the sub, with water intake and outlet, i doubt they would put the moving part on the outer hull
