North Korea's successful rocket launch on Wednesday is believed to have given it the technology to build an intercontinental ballistic missile with a range of more than 10,000 km.
Some experts even believe that the range has now been extended to more than 13,000 km. A North Korean ICBM with a 10,000-km range could hit the northwestern coast of the continental U.S., while a 13,000-km range means most areas of the U.S. are now potential targets.
The longer estimate is based on the fact that the first-stage booster flew further than initially expected.
North Korea has conducted four test launches of space rockets, which are widely seen as a cover to test long-range ballistic missile technology. It succeeded in separating the first and second stages in launches conducted in 1998 and 2009. The second stage of the rocket launched in August 1998 landed around 1,620 km away, while the second stage of the one launched in April 2009 landed around 3,800 km away, doubling the range over the 10-year period.
The maximum range of the rocket North Korea fired in 2009 was estimated to be over 6,700 km, so with the latest rocket suggesting a range of over 10,000 km, it has again nearly doubled the range within three years.
Now, North Korea seems to have the capacity to build an ICBM with a range of at least 10,000 km. But before it can make a viable missile, it needs to miniaturize nuclear warheads and develop technology allowing the rocket to re-enter the atmosphere.
North Korea is believed to have placed a 100 kg payload inside the nozzle of the latest rocket. "That is still too small and not efficient enough to carry a nuclear warhead," a Defense Ministry official here said.
Some rocket experts speculate that if North Korea manages to build nuclear warheads weighing 500-1,000 kg, it would be able to hit targets on the U.S. west coast. According to U.S. military magazine Global Security, the latest rocket is capable of carrying a payload weighing between 250 kg to 550 kg.
But one rocket scientist with a state-run research center here said, "A 100 kg payload could be North Korea’s limit at this point."
North Korea has apparently been busy trying to miniaturize nuclear warheads that can be mounted on missiles. South Korean intelligence believes the North has conducted over 100 tests since the late 1980s to develop a detonator that could trigger a nuclear explosion by compressing fissile material.
Some military analysts estimate the North has improved its capability to build smaller, lighter and more potent nuclear warheads in its two nuclear tests -- one in 2006 and the other in 2009. There is also a possibility that the North acquired additional technology from Pakistan and Iran.
But the government here believes North Korea does not have the technology to build a missile capable of re-entering the earth's atmosphere from space. The warhead of a long-range missile shoots above the atmosphere and travels through space, only to freefall toward its intended target when it re-enters the atmosphere.
Thus the warhead of an ICBM with a 10,000-km range has to withstand tremendous shocks and temperatures of between 6,000 and 7,000 degrees Celsius as it re-enters the atmosphere, but the North apparently only has the technology to build warheads that can withstand temperatures of 2,000-3,000 degrees.
Still, according to Lee Soo-seok at the Institute for National Security Strategy, the North could acquire the technology "sooner than expected."