Musudan’s high speed is bad news for defense

A medium-range ballistic missile launched Wednesday by North Korea flew at an average speed of Mach 11.3, or 11.3 times faster than the speed of sound, according to an analysis of a timeline seen on a monitor at the launch site.

The hypersonic speed of Mach 11.3 has sharply raised concerns about the capabilities of the Patriotic Advanced Capability-3 (PAC-3) missile defense system that the South Korean military has purchased to upgrade its existing PAC-2 missile defense system. The PAC-3 flies at Mach 3.5 to 5 and intercepts incoming missiles at altitudes of up to 40 kilometers (25 miles).

Analysis of one photo released by the North’s state-run Korean Central Television shows the count 12:32 on a screen watched by North Korean leader Kim Jong-un, who oversaw the launch Wednesday morning in the eastern coastal city of Wonsan in Kangwon Province.

“The screen displays the trajectory of the Musudan from the moment it was launched to its falling point,” said a military official involved in the assessment of the North’s latest intermediate range ballistic missile [IRBM] launch. “The number 12:32 indicates the total time it took for the missile from liftoff to its crash into the sea.”

The official spoke on the condition of anonymity. The calculation that the Musudan flew at a speed of Mach 11.3 also depends on the North’s claim that it soared to a height of 1413.6 kilometers, a claim South Korean Defense Minister Han Min-koo concurred with on Friday.

“I understand that the missile reached an altitude similar to what North Korea has claimed,” he said.

If the missile was placed at a normal angle on a launch pad, it would have flown at least 2,827.2 kilometers, twice the 1,413.6 kilometers.

Experts said if the missile was able to soar as high as 1,000 kilometers, it could have flown approximately 3,000 to 4,000 kilometers had it been placed at a normal angle on the launching pad, the full range of an IRBM.

When the 2,827.2-kilometer trajectory is divided by 725 seconds, or 12 minutes and 32 seconds, it yields a calculation that the missile flew 3,759.6 meters per second, 11.3 times faster than the speed of sound, which moves at 333 meters per second.

Another military source, who asked not to be named, said the military assessed that the missile had flown at Mach 17.

“When a ballistic missile flies above the atmospheric altitude and is in a vacuum, its maximum speed can reach Mach 20,” said Lee Choong-geun, a research fellow at the Science & Technology Policy Institute. “If the Musudan re-enters the atmosphere after flying 3,500 kilometers, its speed will be around Mach 10.”

The speed of the Musudan has raised worries about the defense capabilities of South Korea, which has been upgrading its missile defense system to PAC-3 from PAC-2.

The worries extend to the Terminal High Altitude Area Defense (Thaad) system being discussed between Washington and Seoul.

The U.S.-made advanced defense system is designed to shoot down incoming missiles at altitudes of up to 150 kilometers above ground. Thaad missiles can travel at speeds over Mach 8 and are in the hypersonic category.

Kim Kyong-soo, a professor at Korea National Defense University, played down the worries somewhat.

He said Thaad missiles have technical capabilities to shoot down Musudan missiles even if they travel at hypersonic speeds. But he admitted there would be less time to make judgements and decisions to fire Thaad missiles to intercept incoming Musudans traveling at hypersonic speeds.

BY KANG JIN-KYU, JEONG YONG-SOO [kang.jinkyu@joongang.co.kr]