Shrinking the Bomb

A bomb is useless to North Korea — as an offensive weapon or as a deterrent — unless the country can make a convincing case that it has a reliable delivery system. So when the North flaunts missiles at military parades, as it did on April 15, the stars of the show tend to be the big missiles that are designed to reach Washington and New York. While several intercontinental ballistic missiles rolled down the streets of Pyongyang, conducting a flight test that proves one could fly that far, and land with accuracy, is so far only an aspiration.

Missing from the parade were the short- and medium-range missiles that have been successfully flight tested. American intelligence agencies believe some of those can carry operational nuclear arms. The critical one is the Nodong, which has a range of about 800 miles.

But the North Koreans are discovering — as the United States, the Soviet Union and China did before them — that it is far more complicated to design an intercontinental missile. With that weapons system, a warhead would move at four miles a second and re-enter the atmosphere in fiery heat — so, if badly engineered, it would burn up long before hitting a target. To reach their goal, North Korean weapons designers are looking to miniaturize their warheads, making them far lighter and more powerful.

The big effort these days is to merge two technologies: Get a missile that can cross the Pacific, and marry it to a warhead that can survive the ride. And this is why the United States is so desperate to stop the cycle of testing.

The cyber- and electronic warfare attacks that President Barack Obama ordered against the country’s missile fleet were intended to slow North Korea’s learning curve. The Musudan, which can travel 2,200 miles, has racked up an embarrassing failure rate of 88 percent — although how much of that is due to incompetence or outside meddling is not known. Until the North Koreans figure out what is going wrong, and how to fix it, they appear hesitant to test the KN-14 and the KN-08, both of which are designed to hit the continental United States.