- something that will either attract or repel any electrically conductive material? I thought I once heard that something like this is possible using superconducting magnets and “inductance”, but I can’t confirm this. I do vaguely recall that there were plans to propel submarines using electricity and jets of seawater (electrically conductive brine).
In 1966? That what you’re thinking of?
The technology is interesting, but impractical for military subs. For one, it generates a big magnetic field, so you might be able to follow the sub with a simple compass. It also leaves a trail of ionized chlorine, so you could just toss a bunch of swimmers into the water and find out where the eye-stinging is the worst.
It’s called magneto-hydrodynamic (MHD) propulsion. The principle is described in DDG’s link, but modern versions use superconducting magnets. It was featured in The Hunt for Red October.
In realitiy, it’s only been used on one experimental ship. This ship cost $55 million to build and achieved a top speed of 8 knots. :rolleyes:
There’s also the Kasimir effect that causes conductive surfaces to repel each other no matter what. I think that’s what it is called and what it does, anyway - could have the spelling wrong. It’s a very weak effect that reminds me of perpetual motion machines…
The Casimir effect is the apparent attraction of two uncharged, closely spaced metal plates. It arises by vacuum fluctuations outside the plates causing “pressure” on them, and pushing them together, as there are fewer of these fluctuations inside, and thus lower pressure.
Apparently the Casimir effect can be repulsive in limited circumstances, according to the Wikipedia article. But I don’t know the reference, so I can’t elaborate on that it. In any case, the Casimir effect is generally understood to be an attractive phenomenon.