중앙데일리

Having no doubt over ship’s sinking

U.S. naval expert says skeptics don’t understand ‘mechanics of torpedoes’

[천안함 폭침 1주년] “1번 쓰인 어뢰 추진체, 미군 도면과 일치”

Mar 26,2011
At left: “No.1” can be seen written in Korean on the bottom of a torpedo propeller found after the Cheonan sinking. At right, a propeller fan from the North Korean torpedo is seen covered in aluminum oxide, a by-product of an explosion. An investigation team found the same material on the Cheonan’s stern. Aluminum oxide was also produced in a simulated experiment by the investigation team. Left: Provided by the Ministry of National Defense, Right: By Kim Tae-seong

U.S. Navy Rear Adm. Thomas Eccles, who led the U.S. team involved in South Korea’s investigation of the Cheonan sinking, said those who do not agree with the results of the investigation - which found North Korea responsible - are “those who are unfamiliar with the mechanics of torpedoes.” Another expert said such a belief is “ridiculous.”

One year after the Cheonan corvette was sunk in the Yellow Sea on March 26, killing 46 sailors, debate persists over the cause of the accident.

Lee Seung-hun, a U.S.-based Korean professor, has said that the “No. 1” found inscribed in Korean on a torpedo fragment could not have survived the scorching heat of the explosion. “No. 1” is significant because the South Korean military had recovered a North Korean torpedo one year earlier with a numerical sign and Korean letter marked in a similar place.

But Eccles, who was part of the 15-man U.S. team, told the Voice of America that the heat of the explosion would not have been enough to obliterate the writing. “As an engineer, I cannot agree to [Lee’s] claims,” Eccles said.

The rear admiral also said the investigation would have concluded the torpedo was North Korean even without the “No. 1” inscription. Eccles said his team determined that the torpedo’s propeller was an exact match to diagrams his team had brought with them about North Korean weapons.

And Song Tae-ho, a professor of mechanical engineering at the Korea Advanced Institute of Science and Technology, said Lee’s claims were “ridiculous.”

“Professor Lee is ignoring the principle of the conservation of energy,” Song told the JoongAng Ilbo. “When a torpedo explodes underwater, heat of around 3,000 degrees Celsius is created, but as bubbles are created and swell they push out the water around them, creating low temperature and low pressure.

“As heated gas moves its energy into the seawater around it, the [gas itself] falls in temperature. If it were to keep its heat, then the energy conservation principle would shatter,” he said. “The temperature inside the bubbles goes down 604 degrees Celsius 0.0071 seconds after detonation. After 0.1 seconds, the temperature falls quickly to 28 degrees Celsius.”

Lee also claimed that paint on the torpedo section would have melted due to the heat of the explosion, but Song scoffed at Lee’s assertion, saying Lee had never seen the section so he could not know whether there was paint on it or not.

“He should make those claims at the scene,” Song said. “The dark paint on the propeller never melted.”

Suh Jae-jung, a U.S.-based Korean professor at Johns Hopkins University, said Thursday during a presentation at the National Assembly attended by liberal groups, lawmakers and Lee that an “underwater explosion” did not cause the Cheonan to split in half, which was the conclusion of the investigation. Suh said there were no signs of fragments or water columns, which would indicate an explosion.

The head of the joint investigation team, Yoon Duk-yong of KAIST, told the JoongAng Ilbo that “torpedoes made with the latest technology do not create damage with fragments but make bubbles to wreak havoc. The [torpedo’s aluminum casing] shattered into shards and scattered in the water; they did not harm the vessel and are very hard to find.”

Yoon said air bubbles caused by the explosion lifted the ship and split it in half as the bubbles shrank upon impact and lowered the pressure under the ship, sucking it down into the water.

The professor said sailors on the Cheonan witnessed water columns and he also said no sailors were burned, more proof of an explosion because all the energy from the torpedo had extinguished upon impact.

The president also was critical of those who defend Pyongyang.

“It creates an even bigger sadness that not one among the people who [have backed] North Korea’s claims has confessed his wrongs with courage,” said President Lee Myung-bak, cited by his spokeswoman yesterday.


By Christine Kim [christine.kim@joongang.co.kr]


Related Korean Article[중앙일보]

[천안함 폭침 1주년] “1번 쓰인 어뢰 추진체, 미군 도면과 일치”

에클스 미국 측 조사단장

토머스 에클스 미 해군 준장은 24일(현지시간) “천안함 사건 뒤 사고 해역에서 발견된 어뢰 추진체는 미군이 확보한 북한 어뢰 도면과 정확히 일치한다”며 “한글로 쓰인 ‘1번’ 글자가 없었어도 어뢰가 북한 것이라는 결론을 내렸을 것”이라고 말했다. 천안함 사건 1주기를 맞아 미국의 소리(VOA) 방송과 가진 인터뷰에서다. 에클스 준장은 지난해 4월 진행된 천안함 사건 민·군 합동조사 당시 미국 측 조사단장이었다.

그는 어뢰 폭발 때 ‘1번’ 글자가 지워지지 않은 데 대해 “탄두가 폭발하면 고열이 발생하지만 추진체는 탄두로부터 5m 뒤에 있는 데다 물속에 있어 글자를 지울 정도는 안 된다”고 설명했다. 그러면서 ‘1번’ 글자가 남아 있는 것에 의혹을 제기하는 사람들을 향해 “어뢰의 폭발 메커니즘을 잘 몰라서 그러는 것 같다. 공학자로서 그런 주장에 동의할 수 없다”고 말했다.

에클스 준장은 미 해군 최고의 수중 무기 전문가로 꼽힌다. 그는 미 해군의 수중전과 관련된 어뢰, 잠수함 탑재 탄도미사일 등 수중 무기체계를 총괄해온 인물이다. 현재 미 해군 해상체계 사령부의 수석 기술부장이다.




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