Modern Submarines Too Quiet? Don't Try to Listen Then

The Economist in the last six months published a series of interesting articles on the challenges of anti-submarine warfare.

As long time readers may have figured out, I love - from a professional perspective - ASW. Neglected and unloved by most, but to me a passion. Though few really cared outside fellow fetishists, I was actually damn good at it - for an officer.

It is all math and a little bit of instinct built by experience, but since I got too old to play tactical and was needed elsewhere - and then after leaving AD totally out of it - I've had to nibble what I can off of open source.

For those of you who share this passion, one thing we are always looking for is where technology is going. ASW is hard and is always getting harder in the Darwinian measure/counter-measure hide-n-seek that defines this warfare area. You cannot sit still and expect to win.

Though some 100# heads tell you they have "war winning" technology - even when briefed in you soon realize that, well, ... there are holes in the tactical applications. That being said, the more tools the better - and operational experience tells us that you need lots of different tools in order to successfully prosecute enemy submarines through search, localization, track, and attack. 

Not everything works everywhere against all targets - so bring a big toolbag.

As such, this little bit had me reaching for the circular slide rule;

...modern submarines are very quiet, and neither side has gained a definitive upper hand.

There are other options. Submarine-spotting aircraft carry “magnetic anomaly detectors” (MAD) which pick up disturbances in the Earth’s magnetic field caused by a submarine’s metal hull. Those disturbances are tiny, which means MAD is only useful at ranges of a few hundred metres.

There may, though, be a better way. Thanks to something called the Debye effect, it might be possible to hunt submarines using the magnetic signatures of their wakes. Seawater is salty, full of ions of sodium and chlorine. Because those ions have different masses, any nudge—such as a passing submarine—moves some farther than others. Each ion carries an electric charge, and the movement of those charges produces a magnetic field.

The Debye effect has been known since 1933, but its effects were thought to be tiny. The American navy set out to explore it nonetheless in 2009, giving research grants to three firms to check whether it could be used for submarine detection. One, Cortana Corporation of Falls Church, Virginia, found a significant effect. Cortana was given a second grant in 2011 to continue the work, which was expected to produce a sensor which could be deployed from a ship. Since then the navy has continued to award Cortana grants for hush-hush jobs.

Neither Cortana nor the navy will discuss exactly what they are up to. But it is likely that the technique can only detect certain submarine movements in some situations. Submarines produce many different types of wake. As well as the familiar V-shaped wake they leave underwater disturbances known as “internal waves”, flat swirls called “pancake eddies” and miniature vortices which spin off from fins and control surfaces. These all depend not only on speed and depth but also on the submarine’s hydrodynamics (the underwater version of aerodynamics).

Read it all. Exciting stuff.

Add to it some of the things ... well ... things still locked away, and I like new ways to work the early part of the kill chain ... as long as those sneaky bastards keep moving ...

As a side note, why does The Economist keep putting stuff out about ASW? One has to remember, the island nation was twice in the last hundred years almost starved to death by submarines.

She knows.