As of March 2017, the X-15’s official world record for the fastest time has not been broken
The amazing photograph in this article shows the first of four captive-carry flights of the X-15 coupled to its Boeing NB-52A Stratofortress “mother ship” (s/n 52-003A), which was taken on March 10, 1959, at Edwards Air Force Base (AFB).
A. Scott Crossfield, a test pilot for North American Aviation, was seated in the X-15’s cockpit.
The North American X-15 belonged to the X-plane family of experimental aircraft, and it was flown by the National Aeronautics and Space Administration (NASA) and the United States Air Force (USAF) at hypersonic speeds. In the 1960s, the X-15 broke speed and altitude records while traveling to the edge of space and returned with useful information for designing aircraft and spacecraft.
As of March 2017, William J. “Pete” Knight’s flight of Mach 6.72 at 102,100 feet (31,120 m), a speed of 4,520 miles per hour (7,274 km/h), the greatest speed ever recorded by a human, powered aircraft, has stood as the X-15’s official world record.
Thirteen flights by eight different pilots during the X-15 program satisfied the Air Force spaceflight requirement by flying higher than 50 miles (80 km), making them eligible to be astronauts. The civilian pilots received their NASA astronaut wings in 2005, 35 years after the final X-15 flight, but the Air Force pilots received theirs right away.
Two of the 199 X-15 missions (both by Joseph A. Walker) met the international (Fédération Aéronautique Internationale) definition of a spaceflight by traveling more than 100 kilometers (62.1 miles) in altitude, making them actual space trips.
Photo by Edwards History Office file photo / U.S. Air Force
