from wiki:
The magnetohydrodynamic drive, or "caterpillar drive", which has no moving parts was popularized as a submarine propulsion system by the movie version of The Hunt for Red October, written by Tom Clancy, which portrayed it as a virtually silent system.
Although experimental surface ships have been built with this propulsion system, speeds have not been as high as expected. In addition, the drive system can induce bubbles to form, compromising stealth, and the low efficiency leads to very high required reactor powers. These factors make it unlikely to be considered for any military purpose.
But who knows, I'd like to believe there is a purpose to showing the prop
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