Armstrong was actively engaged in both piloting and engineering aspects of the X-15 program from its inception. He completed the first flight in the aircraft equipped with a new flow-direction sensor (ball nose) and the initial flight in an X-15 equipped with a self-adaptive flight control system. He worked closely with designers and engineers in development of the adaptive system, and made seven flights in the rocket plane from December 1960 until July 1962. During those fights he reached a peak altitude of 207,500 feet in the X-15-3, and a speed of 3,989 mph (Mach 5.74) in the X-15-1.

Armstrong was born August 5, 1930, in Wapakoneta, Ohio. He attended Purdue University, earning his Bachelor of Science degree in aeronautical engineering in 1955. During the Korean War, which interrupted his engineering studies, he flew 78 combat missions in F9F-2 jet fighters. He was awarded the Air Medal and two Gold Stars. He later earned a Master of Science degree in aerospace engineering from the University of Southern California.

Armstrong has a total of 8 days and 14 hours in space, including 2 hours and 48 minutes walking on the Moon. In March 1966 he was commander of the Gemini 8 orbital space flight with David Scott as pilot—the first successful docking of two vehicles in orbit. On July 20, 1969, during the Apollo 11 lunar mission, he became the first human to set foot on the Moon. From 1969 to 1971 he was Deputy Associate Administrator for Aeronautics at NASA Headquarters, and resigned from NASA in August 1971 to become Professor of Engineering at the University of Cincinnati, a post he held until 1979. He became Chairman of the Board of Cardwell International, Ltd., in Lebanon, Ohio, in 1980 and served in that capacity until 1982. During the years 1982-1992, Armstrong was chairman of Computing Technologies for Aviation, Inc., in Charlottesville, Virginia. From 1981 to 1999, he served on the board of directors for Eaton Corp. He served as chairman of the board of AIL Systems, Inc. of Deer Park, New York, until 1999 and in 2000 was elected chairman of the board of EDO Corp., a manaufacturer of electronic and mechanical systems for the aerospace, defense and industrial markets, based in New York City.

From 1985 to 1986, Armstrong served on the National Commission on Space, a presidential committee to develop goals for a national space program into the 21st century. He was also Vice Chairman of the committee investigating the Space Shuttle Challenger disaster in 1986. During the early 1990s he hosted an aviation documentary series for television entitled First Flights.

The X-15 research aircraft was developed to provide in-flight information and data on aerodynamics, structures, flight controls, and the physiological aspects of high-speed, high-altitude flight. A follow-on program used the aircraft as a testbed to carry various scientific experiments beyond the Earth's atmosphere on a repeated basis.

For flight in the dense air of the usable atmosphere, the X-15 used conventional aerodynamic controls such as rudder surfaces on the vertical stabilizers to control yaw and canted horizontal surfaces on the tail to control pitch when moving in synchronization or roll when moved differentially.

For flight in the thin air outside of the appreciable Earth's atmosphere, the X-15 used a reaction control system. Hydrogen peroxide thrust rockets located on the nose of the aircraft provided pitch and yaw control. Those on the wings provided roll control.

Because of the large fuel consumption, the X-15 was air launched from a B-52 aircraft at 45,000 ft and a speed of about 500 mph. Depending on the mission, the rocket engine provided thrust for the first 80 to 120 sec of flight. The remainder of the normal 10 to 11 min. flight was powerless and ended with a 200-mph glide landing.

Generally, one of two types of X-15 flight profiles was used: a high-altitude flight plan that called for the pilot to maintain a steep rate of climb, or a speed profile that called for the pilot to push over and maintain a level altitude.

The X-15 was flown over a period of nearly 10 years--June 1959 to Oct. 1968--and set the world's unofficial speed and altitude records of 4,520 mph (Mach 6.7) and 354,200 ft (over 67 mi) in a program to investigate all aspects of piloted hypersonic flight. Information gained from the highly successful X-15 program contributed to the development of the Mercury, Gemini, and Apollo manned spaceflight programs, and also the Space Shuttle program.

The X-15s made a total of 199 flights and were manufactured by North American Aviation.

X-15-1, serial number 56-6670, is now located at the National Air and Space Museum, Washington DC.

North American X-15A-2, serial number 56-6671, is at the United States Air Force Museum, Wright-Patterson AFB, Ohio. The X-15-3, serial number 56-6672, crashed on 15 November 1967, resulting in the death of Maj. Michael J. Adams.