Go to contents

`Non-contact Explosion Likely Sank Cheonan`

Posted April. 26, 2010 03:32,   


The naval patrol vessel Cheonan was apparently ripped in half due to a “non-contact” underwater explosion below the gas turbine room at the left bottom of the hull, investigators said yesterday.

Yoon Duk-yong, co-head of the joint public-private investigation team, said this conclusion was reached based on a visual examination of the inside and outside of the sunken corvette in the probe’s second interim report. The Cheonan was salvaged Saturday. “The hull had no traces of burns or melting due to heat or puncture (created by a direct explosion),” he added.

On the location of the external explosion, Yoon said, “Around a 10 meter-long space of the gas turbine room was empty, so the explosion must have occurred somewhere below the portside of the ship near the turbine room. More damage was seen on the right side of the ship since the impact came from the portside and raised the right side (in a fan shape). The bottom of the hull was entirely bent upwards, so the impact went in that direction.”

On the extent of the damage to the hull, Lt. Gen. Park Jeong-I, co-head of the investigation team, said, “The bottom of the hull was bent. The keel (spine of the hull) was cut and was entirely rolled upwards.” According to Lt. Gen. Park, an analysis of photos that matched the ripped parts of the bow and stern showed that the portside section lost 3.2 meters and the starboard lost 9.9 meters. The Cheonan was 88.3 meters long.

The team said the explosion could have been caused by a torpedo or mine detonation, but is reportedly placing more weight on the possibility of a “bubble jet” induced by a torpedo detonated underwater that causes shockwaves.

In a question-and-answer session with reporters immediately after a public address by Prime Minister Chung Un-chan in the afternoon, Defense Minister Kim Tae-young said, “The bubble jet effect from a heavyweight torpedo explosion seems to be the most likely explanation.”

On the observation that no pillar of water that normally occurs in a bubble jet explosion was seen, Yoon said, “The pillar can rise (if the explosion occurs far away) and could go sideways (if the explosion is near). An underwater explosion would immediately send shockwaves and create a bubble jet within one or two seconds. If the explosion occurs near the bottom of the hull, the initial explosion effect is magnified while the bubble jet effect (which enables seawater to lift the center of the hull with expansive force) is minimized.”

srkim@donga.com pen@donga.com