Investigators Point to Bubble Jet

5-Day Mourning Period Begins for 46 Dead, Missing Cheonan Sailors

By Jung Sung-ki

Staff Reporter

A massive air bubble caused by a proximity explosion below its hull split the Navy frigate Cheonan in two, investigators indicated Sunday, bolstering suspicions that a North Korean torpedo or mine could have been the cause of the disaster.

Prime Minister Chung Un-chan announced a five-day national mourning period in tribute to the 46 dead and missing sailors from the ship.

The government designated April 29 a national day of mourning. The fallen seamen will be posthumously promoted by one rank and be decorated with the Hwarang Cordon of the Order of Military Merit, the country's fourth highest military medal, the prime minister said.

"After a visual examination of the inside and outside of the broken section, we've concluded that there must have been an underwater explosion," Yoon Duk-yong, co-head of a 130-strong civilian-military team, said, announcing the interim results of the investigation into the ship sinking.

The announcement came a day after the bow of the sunken frigate was raised.

"Given the appearance, moreover, it is most likely to have been a non-contact explosion, not a contact blast," said Yoon, a professor emeritus at the Korea Advanced Institute of Science and Technology (KAIST). "The exact location and power of the explosion will be discovered through further analysis and simulations."

Yoon again ruled out the possibility of an onboard explosion, a reef or a metal fatigue fracture.

The ammunition magazines, fuel tanks and diesel engine room show no signs of fire damage, and sheaths covering cables remain relatively intact, the professor said.

The bottom of the hull has a few scratches but there were no holes, he added.

Lt. Gen. Park Jung-i, co-head of the investigation team, was more explicit about the possibility of an external explosion.

Park said the port side of the 47.6-meter bow section lost 3.2 square-meters of its hull, while the starboard lost 9.9 square-meters, which means the port side of the hull was affected by external pressure first, which then moved up the starboard side.

"An explosion must have come from below the gas turbine room because that entire section was lost," Park said.

Earlier in the day, Defense Minister Kim Tae-young said, "An explosive induced bubble jet is believed to be the most likely cause at the moment, but the possibility of other causes is still under investigation."

He said it would take a month to collect debris for analysis and to announce the final results.

The bubble jet effect occurs when a torpedo or mine detonates in the water some distance away from the ship. The explosion creates a "hole" in the water, and due to the difference in pressure, this sphere collapses from the bottom.

This creates a "pillar" of water that can rise up to 100 meters into the air, damaging a ship heavily. The water breaks a meter wide hole straight through the ship, flooding one or more compartments, and can break the ship apart.

Mysteriously, none of the 58 survivors from the incident saw a column of water.

The Cheonan sank in waters off the disputed sea border with North Korea. The North has never recognized the sea border, the Northern Limit Line (NLL), drawn up by the U.S.-led United Nations Command at the end of the 1950-53 Korean War, leaving the West Sea (Yellow Sea) a major flash point for conflicts.

Fatal skirmishes between the navies of South and North Korea occurred in 1999, 2002 and last November.

근접 수중폭발 잠정 결론

정부 합동 조사단은 천안함이 수중 근접 폭발에 의해서 반파 된 것으로 보인다고 잠정 결론을 내렸다. 이로써 북한의 어뢰 혹은 기뢰에 의해서 천안함이 침몰했을 것이라는 추정에 더욱 무게가 실리게 됐다.

이와 관련, 정운찬 국무 총리는 닷세간의 국가적 애도기간을 선포했고 29일을 국민 애도의 날로 정했다. 정총리는 희생자들은 한 계급 특진과 함께 화랑 무공 훈장을 받을 것이라고 밝혔다.

윤덕용 합동조사단 민간측 단장은 브리핑에서 “선체의 내부와 외부를 육안으로 살펴본 결과 수중 폭발이 있었던 것으로 결론냈다”라고 말했다 그는 또한 “변형된 모습을 봤을 때 접촉 폭발보다는 비접촉 폭발에 가깝다”며 “정확한 폭발 위치와 폭발 강도는 추가적인 분석과 시뮬레이션을 통해서 밝혀 질 것 이다”라고 덧붙였다.

윤 단장은 선내 폭발과, 암초, 피로 파괴의 가능성은 배제했다.