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How Nork Heavy Torpedo Could Have Sunk Cheonan
Defense Minister Kim Tae-young's comments on Sunday that a bubble jet caused by a heavy torpedo was the most likely cause of the blast that sank the Navy corvette Cheonan have put North Korean heavy torpedoes on the top of the list of suspects.

It is difficult to imagine a country other than North Korea launching a torpedo attack against a South Korean warship, and the extent of damage the Cheonan suffered has made a heavy torpedo the probable cause. Military experts believe North Korea has four types of heavy torpedoes: Yu-3G, ET-80A, TYPE 53-59, and the TYPE 53-56.

One source said if a North Korean torpedo was the culprit, it would most likely have been a Yu-3G. Developed in China during the mid 1980s, the Yu-3G is a "passive acoustic homing" torpedo that tracks the sounds of a vessel's propellers and its wake and attacks accordingly. Experts believe the North would have equipped the Yu-3G with a fuse that can be detonated by the magnetic field generated by a vessel.

The lower part of the Cheonan, beneath the gas turbine room where the external explosion is believed to have happened, is the part of a ship that produces the strongest magnetic field. When equipped with a 200 kg high explosive, the Yu-3G, with a range of 12 km, is said to be strong enough to split a warship the size of the Cheonan in half.

The ET-80A is also a passive acoustic homing torpedo with a range of 7.3 km. The Type 53-59 and Type 53-56 torpedoes, which were developed in the former Soviet Union and were exported to China and North Korea, are straight-track projectiles that travel in a straight line toward their targets after being fired.
Posted by: Steve White 2010-04-30
http://www.rantburg.com/poparticle.php?ID=295680