Submarines: Magnetometers & Degaussing Made Simple

The debate between advocates for Germany or Sweden, in the Netherlands future submarine competition, continues. The French contender has been strangely quiet...wonder why? Do the French know France has won, or what?

In the German corner Anonymous on February 5, 2021 commented :

"Dear Pete,

Magnetic signature is an interesting topic. Germans always put a focus here because of the mine threat in the Baltic Sea and the shallowness of it [see map below].

Lots of places and opportunities there to hide from active sonar. Not so many to hide from magnetometers . And magnetometers are likely to get more powerful and so small that they even can be used from fairly small unmanned aerial vehicles. (see this link eg:  about “SQUID” sensors).

Smart design of the submarine's degaussing system mitigates the problem to a certain extent. However, this system continuously nibbles on your (limited) amount of energy. Not so cool for the captain when his sub is in a high threat environment. Best way to avoid a high magnetic signature is to dramatically reduce the magnetic field of the steel structure. The rest can be reduced with a much smaller degaussing system.

As always... it's some kind of philosophical question and guessing what your future opponents capabilities might be during the life cycle of your submarine."
_______________________________

Baltic Sea Depth Map: Originally in this 2015 article - Above the lighter the blue the shallower the water. The average depth of the Baltic Sea is only 53 meters. The maximum depth, while only 459 meters, is more than deep enough for submarines to hide.

That is if they choose the right hiding places - and those hiding places do not conceal the presence of an opponent's sea-floor (or tethered) sensors. (Map courtesy European Environment Agency).

Pete Comment

Of course having composites in place of steel, where possible in the submarine, may help  minimise magnetic signature as well.