hankyoreh

By Lee Geun-young, science correspondent

Observers are now seeking cause of the Kwangmyongsong-3 rocket’s failure, in which the Unha-3 rocket used by North Korea exploded roughly two minutes after the launch and sank into the West Sea. Analysts said it was more of a “beginner’s level mistake” compared to the Unha-2 rocket launch in 2009, which succeeded as far as the third-stage separation.

Ministry of National Defense policy planning director Shin Won-sik said in a briefing Friday morning that the cause of the explosion had not yet been determined, and that a careful analysis was being conducted by South Korean and US military authorities.

But observers in and around the military tentatively ventured that the second-stage booster may have ignited prematurely. A Defense Ministry official said, “The explosion took place before the first-stage booster separation, which leads us to suspect it resulted from the second-stage booster igniting prior to the first-stage separation.”

Korea Aerospace Research Institute senior researcher Chae Yeon-seok said, “Given that the explosion and crash took place before the 450 km the first-stage booster would have had to travel if it had proceeded normally, it looks as though the second-stage booster ignited and exploded while the first and second-stage boosters were not separated.”

Meanwhile, analysts in Japan speculated about the possibility of self-destruction. Speaking in an interview with NHK, Tetsuo Yasaka, an emeritus professor of rocket engineering at Kyushu University, mentioned both the possibility of engine trouble with the first-stage booster and the chance that North Korean authorities detonated the rocket when it strayed from its course.

Other possible causes of the failure mentioned by Japanese experts included a fuel leak due to fuel tank cracking, an excess fuel supply, a loss of booster balance owing to the inability to use the Earth’s rotation due to the southerly launch path, and ill-advised design changes intended to boost the rocket‘s performance.

Cho Kwang-rae, the head of KARI’s Naro satellite launch project, said the chances of a self-destruct device being detonated were slight, since the rocket did not veer far off its course.

“At this point, there is only speculation that the explosion occurred due to pressure from internal causes, such as engine trouble,” Cho said. “We would need to analyze the data sent to the base station by the booster to know the actual cause.”

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