$40-billion missile defense system proves unreliable

With a convulsive rumble, followed by billowing flames and exhaust, a sleek 60-foot rocket emerged from its silo at California's Vandenberg Air Force Base.

It was a test of the backbone of the nation's missile defense system. If North Korea or Iran ever launched nuclear weapons against the United States, the interceptors at Vandenberg and remote Ft. Greely, Alaska, would be called on to destroy the incoming warheads.

Scientists conducting the test at Vandenberg on Sunday, Jan. 31, 2010, had left little to chance. They knew exactly when the target missile would be launched from an atoll in the Marshall Islands 4,900 miles away. They knew its precise dimensions, expected trajectory and speed.

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