X-43A Scramjet Primed for Mach 10 NASA -- Riding like the tip of a spear on its modified Pegasus booster rocket, NASA's third X-43A hypersonic scramjet research vehicle took to the skies today for a captive-carry flight, remaining attached to its B-52B mothership aircraft.     Serving as a final in-flight check-out of the research vehicle and booster rocket combination prior to the actual launch and free-flight, the successful mission paves the way for launch day, tentatively scheduled for later this Fall...