3 Reasons N. Korea Can’t Nuke the U.S. (Yet)

A view of the launch of North Korea's Kwangmyongsong-3 satellite from the Pyongyang General Satellite Control Command Center on Dec. 12, 2012.
Xinhua/KCNA/Xinhua Press/Corbis

Thursday, North Korea stated explicitly that in addition to planning a third nuclear test, it would also be "targeting" the United States with its nuclear program.

But although the Democratic People's Republic of Korea has rockets and an active nuclear program, threats of a nuclear attack may be bluster, according to some experts – at least for now.

Hans Kristensen, director of nuclear information at the Federation of American Scientists, told Discovery News. "They've built some devices that can go off," he said. "That's not the same as a bomb."

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There are three parts to making a nuclear weapon, he said. First is the fissile material -- uranium and plutonium. The second is the ability to get a bomb onto a plane or missile. Last is designing a missile that will reach targets as far away as the continental United States. North Korea has the first, has not shown it has the second and is part way towards the third.

North Korea showed it had the fissile material when it set off two test explosions, one in 2006 and one in 2009. Most experts consider the first a failure, given that it was only the equivalent of 1,000 tons of TNT, or one kiloton. The 2009 explosion was more successful, estimated at several kilotons -- still a fraction the power of the bomb used on Hiroshima.

Setting off a nuclear explosion is one thing, but building a warhead small and light enough to fit in a plane or on top of a missile is another. For comparison, it took the United States several years to develop warheads that could fit on a rocket. "The first hydrogen bomb we dropped on test sites in the Pacific was the size of a small house," said Kristensen. That was in the 1952. A missile capable of sending a bomb to the USSR wouldn't debut until 1959.

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If the North Koreans can shrink a bomb down to that size, they would still need a long-range missile. So far the DPRK has test-flown several missiles of varying ranges. This past December, they launched a satellite, which is reportedly spinning out of control. North Korea has launched satellites before: in 2009 with the Kwangmyŏngsŏng-2, which the government said was a communications satellite, and in 2006 it conducted a test of several missiles, among them the Taepodong-2, which failed seconds after lift-off.

Although none of the missiles or rockets successfully tested so far could reach the continental United States, it's possible that the North Koreans could develop one. Current estimates for the range of a Taepodong-2 are as much as 6,200 miles, enough to reach the western half of the United States. That estimate is at the high-end and assumes the missile has a two-stage rocket.

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