Hunting submarines with magnets | Hacker News Reader

Hunting submarines with magnets

economist.com

40 pointsmiraj12 comments

Ah, I thought it might be an article about the magnets that the Canadians literally dropped on submarines! https://warisboring.com/nato-bombed-soviet-submarines-with-t...

Oh, they gave them up because they were too effective on subs in training?

This is a ludicrous article. NATO must have these ready and waiting.

This is an interesting concept -- but how do you know where to drop the magnets in the first place?

If this works, that would be cool. However, these defense contractors are incentivized to make it seem like something is working so that they beat other contractors to follow-on funding. That doesn't necessarily mean that they are close to making it production-ready for a Navy boat.

SQUID is tough technology. It takes liquid nitrogen or liquid helium to get them cold enough to superconduct. A tank of liquid nitrogen is easy enough to take on a boat, though.

The devices are so sensitive that you can rotate a cheap one 90 degrees and easily measure the earth's magnetic field. Advanced ones are used to measure brain wave activity. My concern is that SQUID devices are so sensitive that they cannot be stabilized enough on a boat in the ocean to prevent noise (from Earth, boats, gyroscopes, liquid nitrogen pumps, etc) that would make it able to consistently detect the Debye effect.

This may be an incredibly stupid question, but I know they used gravimeters to map the ocean floor on subs.

And I recall an anecdote of snow fall on a roof effecting their results in a lab, could you possibly use them to detect other subs.

If it is based solely on mass, then I don't think so. A submerged submarine is almost neutrally buoyant[0]. It has the same average density as the water around it. Therefore, the mass of the ship is the same as the mass of the water it displaces, and a gravimeter wouldn't observe anything different.

[0] Err, almost. There is no such thing as perfectly neutral buoyancy. In practice, they are very slightly heavy and fly though the water as a lifting body.

Cheers! That's a very good point.

From space... https://en.wikipedia.org/wiki/Swarm_(spacecraft)

My computer science teacher in high school was a sailor in the Soviet Navy. He alluded to something like this being used. That would have been in the min 90s or so. At that point we weren't part of the empire so he probably didn't care about keeping the secrets about it.

The article mentions an article from 1990 in the Soviet military magazine "Naval Collection."

Yap, saw it. The way he talked about it sounded more like a "it already works in practice this way" vs "it could work in theory". But I maybe misremembering, it was a long time ago.

My a lecturer in the office next to mine was working on this stuff around 1990/91 (we were in the theory section of the Physics Dept of the University of Glasgow.) I'm not sure it came to anything, he described the theory behind it to me when he was working on the grant application; these sort of side-project applications went on all the time.

At this distance in time, my memory of it is no more than what's in the article anyway, so it's not like I have secrets to tell.

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