An aircraft resembling a large bodyboard detached from a flying B-52 bomber and then shot across the Pacific on Wednesday at more than 3,500 mph, shattering aviation records and reigniting decades-long efforts to develop a vehicle that could travel faster than a speeding bullet. The unmanned X-51 WaveRider, powered by an air-breathing hypersonic engine that has virtually no moving parts, was launched midair off the coast near Point Mugu. It sped westward for 200 seconds before plunging into the ocean as planned. Previous attempts at hypersonic flights lasted no more than 10 seconds. "Everything went very well for a first...