Considered among the most successful research aircraft ever built, the X-15 was designed to explore flight at supersonic and hypersonic speeds, and at altitudes up to more than 60 miles, effectively reaching the edge of space. Spanning a decade, and total of 199 flights, the program only suffered a single fatality. During one flight that reached an altitude of 266,000 feet, thus qualifying the pilot for astronaut wings, an electrical short caused the autopilot to shut off. While trying to fly the plane and simultaneously conduct experiments, Maj. Michael J. Adams was overtasked. He noticed the aircraft drift sideways and enter a spin, but managed to get it into a semicontrolled dive. Falling at 4,000 miles an hour, the X-15 began to oscillate, and then broke into pieces at 62,000 feet above the ground. Adams was unable to eject. Most of the wreckage landed on private property, north of Red Mountain. A memorial to the pilot was constructed on public land north of the site.
Three X-15s were built by North American Aviation in Inglewood, California. The rocket-powered plane was launched from a modified B-52 bomber at an altitude of about 45,000 feet. Of the 12 pilots who flew the X-15, eight flew above 50 miles altitude and qualified for astronaut wings. Due to the vehicle’s speeds (up to Mach 6.7), a test range running from Edwards to Wendover, Utah, was established, with three NASA radar tracking stations along the route. During 1961, the X-15 pilots surpassed Mach 4, 5, and 6 for the first time ever. In 1962, NASA pilot Joe Walker achieved an altitude of 354,200 feet (more than 60 miles). In 1967, Maj. William “Pete” Knight flew a modified X-15 to a record speed of 4,520 miles an hour (Mach 6.7).
A model was constructed to study the crash. Video courtesy of Peter Merlin/NASA.