This was an article I remembered reading back in the ‘70s in Science Digest. So, the other day after my previous post, I read the Wikipedia article ‘Magnetohydrodynamic drive’, and, yes, problems include excessive noise (I believe seawater turbulence) and electrolysis. A small amount of current will generate a small amount of electrolysis, but, this is an extreme magnetic field. This drive would require extreme amounts of energy, which is not available, as the drive isn’t all that efficient.
The biggest problem is the magnetic signature on a sub that wants no magnetic field to elude those magnetic seeking torpedoes.
The state of the art of subs even in my time in the Navy in the 70s was when rigged for quiet, the subs were quiet enough that there was permitted no extraneous noise, certain equipment was shut down, most pumps were sound isolated in three axes, walking around with quiet shoes only if absolutely necessary, personnel not on watch were in there bunks, whispering only, no talking. That’s hard to beat.
A shaft stopped and locked certainly makes for insane noise and vibration, but, a trailing shaft still makes a lesser noise, mostly water turbulence, but since the drive turbine also turns, it would overheat, thus a small amount of steam would still be admitted to the turbine to keep it ‘cool’, another source of noise.