This week in Edwards history Published Aug. 10, 2017 By 412th Test Wing Public Affairs EDWARDS AIR FORCE BASE, Calif. -- On Aug. 8, 1955, the X-1A was lost after an explosion took place while still mated to its mother ship at an altitude of 30,000 feet, just 70 seconds before launch. NACA pilot Joe Walker escaped unharmed from the cockpit, whereupon the research plane was jettisoned over the bombing range. The accident, which took place on its second mission with NACA, was caused by the reaction of an Ulmer leather gasket to liquid oxygen.