<hi style=afpcap>The North American X-15 was designed to be an air launched hypersonic research aircraft capable of achieving a high Mach number. Three examples were built with all serving with the Air Force Flight Test Centre at Edwards AFB, California as well as NASA at the Dryden Research Centre. Basically a rocket with a cockpit mounted at the front, the X-15 was launched from a modified B-52 bomber at altitude. Once free from the mothership, the X-15 pilot inginted the rocket motor and climbed to altitude.</hi>