Spaceflight Insider

Our Spaceflight Heritage: celebrating 55 years of X-15

The X-15 space plane on the wing of a B-52 aircraft. Photo Credit: NASA

On this date (June 8) in 1959, A. Scott Crossfield flew the X-15, leading the United States in the first glide flight at Dryden Flight Research Facility, CA.  Within the first 50 years of spaceflight, the X-15 became the world’s first operational spaceplane.  The experimental, rocket-boosted aircraft flew 199 flights with 12 different pilots at the controls from 1959 through 1968.

Various views of the X-15. Image Credit: NASA

Various views of the X-15. Image Credit: NASA

By the time contracts for the airframe and engine were signed with North American Aviation in 1955 and Reaction Motors in 1956, the program already had established goals of flying the X-15 to a speed of Mach 6 and an altitude of 225,000 feet. The precursor organization to NASA, the National Advisory Committee for Aeronautics (NACA), the U.S. Air Force, and the U.S. Navy collaborated in the X-15 program as a joint project in December 1954 by providing resources, including pilots. Eventually the Navy ended its involvement on the X-15 in order to concentrate on aircraft carrier operations.

North American chief project engineer Charles Feltz designed the aircraft with guidance from the Langley Research Center (Aeronautical Laboratory).  The X-15 was a single-seat, mid-wing monoplane that was roughly 50 ft long, with a 22-ft wing span. It was designed to conduct research into such areas as: high aerodynamic heating rates, stability and control, physiological phenomena, and other problems relating to hypersonic flight (above Mach 5).

In order to conserve fuel, the X-15 would be launched from the wing of a B-52 aircraft for high-speed altitude research.

The X-15 on the tarmac. Photo Credit: NASA

The X-15 on the tarmac. Photo Credit: NASA

As North American Aviation’s lead test pilot, Scott Crossfield would take control of the initial flights. According to John V. Becker, former aeronautical researcher at Langley, the X-15 program accomplished many goals for hypersonic flight such as:

  • First application of hypersonic theory and wind tunnel work on an actual flight vehicle.
  • First reusable superalloy structure capable of withstanding the extreme temperatures and thermal gradients of hypersonic reentry.
  • Scott Crossfield in front of the X-15. Photo Credit: NASA

    Scott Crossfield in front of the X-15. Photo Credit: NASA

    Demonstration of a pilot’s ability to control a rocket boosted aerospace vehicle through exit of the Earth’s atmosphere.

  • Given the similar flying characteristics between the two vehicles, the X-15 proved that the space shuttle could re-enter the atmosphere and glide to a precision landing. This was done in part by relying on a maneuver known as Terminal Area Energy Management where speed and altitude are carefully controlled so the vehicle can reach the runway instead of falling short or overflying it.
  • Discovery that the hypersonic boundary layer flow is turbulent and not laminar.
  • Development of the first practical full pressure suit for pilot protection in the space environment.

As a member of the NACA High-Speed Flight Research Station, Scott Crossfield would fly the X-15  fourteen times out of 199 recorded flights, therefore becoming the first pilot in history to fly the speed of sound. Over the next five years, after becoming a research pilot at Edwards Air Force Base in 1950, Crossfield flew fourteen different aircraft and logged more than 100 rocket flight hours. Altogether, he completed 16 missions mated to the B-52, one glided mission, and 13 powered flights, reaching a maximum speed of Mach 297 (1, 960 miles per hour) and a maximum altitude of 88, 116 feet. As a result, Crossfield became the single most experienced rocket pilot in America’s aerospace history.

As of 2014, the X-15 still holds the record for the highest speed ever reached by a manned, powered aircraft.





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Heather Smith's fascination for space exploration – started at the tender age of twelve while she was on a sixth-grade field trip in Kenner, Louisiana, walking through a mock-up of the International Space Station and seeing the “space potty” (her terminology has progressed considerably since that time) – she realized at this point that her future lay in the stars. Smith has come to realize that very few people have noticed how much spaceflight technology has improved their lives. She has since dedicated herself to correcting this problem. Inspired by such classic literature as Anne Frank’s Diary, she has honed her writing skills and has signed on as The Spaceflight Group’s coordinator for the organization’s social media efforts.

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