Finding The Tiny Terrors

The Strategy Page ^ | 6/12/2010 | The Strategy Page

[ErnstStavroBlofeld]

The use of a North Korea midget sub to sink a South Korean corvette three months ago, has forced the United States, and South Korea, to seriously confront the problems involved in finding these small subs in coastal waters. This is a difficult task, because the target is small, silent (moving using battery power) and in a complex underwater landscape, that makes sonar less effective. After the Cold War ended in 1991, the U.S. recognized that these coastal operations would become more common. So, in the 1990s, the U.S. developed the Advanced Deployable System (ADS) for detecting non-nuclear submarines in coastal waters. The ADS is portable, and can quickly be flown to where it is needed. ADS is believed to now be in South Korea, or on the way. ADS basically adapts the popular Cold War SOSUS system (many powerful listening devices surrounding the major oceans, and analyzing the noises to locate submarines) developed by the United States.

ADS consists of battery powered passive (they just listen) sensors that are battery powered and deployed by ship along the sea bottom in coastal waters. A fiber optic cable goes from the sensors (which look like a thick cable) back to shore, where a trailer containing computers and other electronics, and the ADS operators, runs the system. ADS has done well in tests, but it has never faced the North Korean mini-subs.

North Korea has a fleet of over 60 mini-subs, plus about 25 older Russian type conventional boats. North Korea got the idea for minisubs from Russia, which has had them for decades. North Korea has developed several mini-sub designs, most of them available to anyone with the cash to pay. The largest is the 250 ton Sang-O, which is actually a coastal sub modified for special operations.

[TXnMA]

Aside from the fact that ('way back when there was a Heathkit Company) I built my own (rotating disk) depth sounder, I have virtually zero knowledge of sonar. (My thing in computers is graphics manipulation...)

It seems to me something like the graphics trick astronomers use for finding comets, asteroids, etc. should work for locating subs. It uses the principle of taking two images -- separated by a time interval -- then subtracting one image from the other. Anything that is stationary (subtracted from itself) returns a zero. Only that which has moved produces a signal.

If the ADS is purely passive, adding a few active, anchored "pingers" should provide such "snapshot-subtraction" capability.

For all I know, that is already common practice -- but it makes sense to me for locating small, moving targets...