The blast shook buildings miles away. A rocket has exploded on the SpaceX launch pad at the Kennedy Space Center in Florida. SpaceX, a private aerospace company headed by Elon Musk, was preparing the Falcon 9 rocket for a satellite launch flight this weekend. But shortly after massive plumes of dark smoke blasted over the launch pad, NASA announced that the rocket had exploded during an engine test. No one was hurt in the blast, and the fault appears not to have been with the rocket itself. But a launch pad malfunction is already drawing scrutiny.