February 15, 2012: Taiwan has ordered 440 U.S. AN/SSQ-53F sonobuoys, for $762 each. This sonobuoy weighs 8.6 kg (19 pounds) and can last up to eight hours once ejected into the ocean by an aircraft or a helicopter. The sonobuoy transmits back to the aircraft what it hears. The AN/SSQ-53F has a shelf life of five years.
Taiwan got this hot little item because the U.S. Navy is big on sonobuoys again. Another 65,000 were ordered last year, most of them the new AN/SSQ-53F. While sonobuoy technology has not changed dramatically, the way sonobuoys are used has. This is all about taking advantage of new software and cheap, but massive, computer power to provide an edge against Chinese non-nuclear (and very quiet) submarines operating in Taiwanese coastal waters. The most effective way of hunting down subs is via helicopters or maritime patrol aircraft equipped with homing torpedoes and sonobuoys.
Sonobuoys are up to a meter (3.1 feet) long, 120mm in diameter, and weigh up to 18 kg (40 pounds). They are used once by dropping them into the water. The U.S. has two basic types. The most common type floats upright, sending sonar signals into the water and transmitting any data bouncing back to the aircraft overhead. Another type collects water data (bathythermograph, conductivity, temperature, and depth), which it also transmits to aircraft overhead.
The data analysis systems look for faint patterns left by submarines slowly moving through coastal waters. This takes into account the underground geography and the activity of undersea animals and plants. The number and pattern of deployed sensors would also be taken into account. This is the area where quiet subs have suddenly become most vulnerable.
New pattern analysis software was developed and quiet diesel-electric subs from allies were used to test and refine the system. The data analysis computers are located in the aircraft, nearby ships, or even back at land bases (via data transmission via satellite). Once the sub is located the aircraft or helicopter drops a homing torpedo that will seek out (with the help of the pattern analysis) and attack the sub.
The U.S. has been scrambling to develop the ability to detect the new generation of quiet diesel-electric subs. You won't hear any official pronouncements about progress in this area, for obvious reasons. There is progress but just how much won't be publicly known until these new anti-submarine methods are used in combat. But the increased orders for sonobuoys, and the known progress in sonobuoy data analysis, is an indicator of where the best solutions are being found. For Taiwan the new technology is a big help because most Chinese subs are noisy and do not require a lot of sonobuoys to pinpoint.