Origins of the X-15

The X-15 did not start as an aircraft. It started as a research question: what happens to a crewed vehicle at several times the speed of sound, and at the top of the atmosphere? Six years separated the first formal recommendation from the day the first airplane rolled out of the factory.

1952: A recommendation to go faster and higher

In June 1952 the NACA Committee on Aerodynamics recommended more research toward Mach 10 and altitudes of 12 to 50 miles. That September, preliminary studies of space flight research began. The NACA was the government research agency that later became NASA, and those figures set the ambition for what became the X-15.

1954: From panel discussion to joint program

In February 1954 the NACA Research Airplane panel discussed the need for a new hypersonic aircraft. By July a proposal was in front of the Air Force and the Navy. In December 1954 the three organisations signed a memorandum of understanding that set up the joint program, and the Air Force invited contractors to compete to design the aircraft. That arrangement, with each service and the research agency sharing the work, ran for the life of the program.

1955–1956: Airframe and engine contracts

North American Aviation was selected in September 1955 to develop three X-15 aircraft. In February 1956 Reaction Motors received the contract for the XLR99 rocket engine. The engine was a major development effort in its own right, which is why the first flights used a pair of smaller XLR11 engines while the XLR99 was finished. Read more on the X-15 aircraft and its engines.

1956–1958: Mock-up, design freeze, rollout

• December 1956: mock-up completed.
• September 1957: design configuration set and construction starts.
• October 1958: North American rolls out airplane No. 1 from the factory.

The first X-15 reached the High-Speed Flight Station at Edwards, California, in early 1959. Its first flight came on 8 June 1959.

What the planners got right

The program was organised around measurement. Every flight carried instruments, and flights were planned to answer specific questions about heating, stability and control. That discipline is why a program of 199 flights produced data for more than 765 research reports. See the X-15 legacy for what those reports changed.