SEOUL, South Korea — They don't call it rocket science for nothing.

North Korea's first successful launch of a three-stage, long-range rocket has outraged world leaders who consider it similar to a missile capable of attacking the United States, Europe and other far-away targets. But experts say Pyongyang is years away from even having a shot at developing reliable missiles that could bombard the American mainland.

A missile program is built on decades of systematic, intricate testing, something extremely difficult for economically struggling Pyongyang, which faces guaranteed sanctions and world disapprobation each time it stages an expensive launch.