[X-15 Hypersonic Research Program]

NASA. "X-15 Hypersonic Research Program," Updated February 28, 2014. <https://www.nasa.gov/reference/x-15/>

PHOTOGRAPH SIGNED BY THE FIRST CLASS OF PILOTS OF THE HYPERSONIC X-15 AIRCRAFT: NEIL ARMSTRONG, JACK MCKAY, JOE WALKER, ROBERT RUSHWORTH, FORREST PETERSON, AND ROBERT WHITE.

The X-15 hypersonic research program lasted from early 1959 through operational flights in 1968. In its time, the X-15 aircraft set unofficial world speed and altitude records: Mach 6.7 on October 3, 1967 flown by Air Force pilot Pete Knight; and 354,200 feet on August 22, 1963 flown by NASA pilot Joe Walker (pictured here fourth from left).

A total of twelve pilots flew X-15 hypersonic planes during the program, ultimately logging 199 flights. The hypersonic research program was key in developing air and spacecraft built for exiting and re-entering our atmosphere. Insights gained from these tests were applied to the development of the Mercury, Gemini, and Apollo spacecraft, particularly the thermal protection and navigation equipment.

After flying the X-15 as a NASA pilot, Neil Armstrong would later go on to use the spacecraft developed from this program as Commander of the historic Apollo 11 moon landing.