Building On the Past: X-15
Mounted under the wing of a B-52, the X-15 Rocket Plane carried one pilot and 18,000 pounds of fuel, a mixture of liquid oxygen and anhydrous ammonia. Once the X-15 detached from the B-52, the pilot had seconds to light the engine. Every minute the plane dropped 4,000 feet.
Once the engine ignited, the X-15 burned through its entire fuel load in only 80 seconds. In that time, the pilot took the aircraft to elevations reaching space flight, sometimes as high as 354,000 feet. Plane and pilot would also reach speeds approaching Mach 6.7 (4,250 mph), twice as fast as a bullet fired from an M16.
When the X-15 re-entered the atmosphere, it could reach 2,400 degrees Fahrenheit (1,316 degrees Celsius). This data would assist future mission planners with creating safe re-entry procedures for the Mercury, Apollo, and Space Shuttle programs. Two X-15 pilots did later benefit from this data: Neil Armstrong and Joe Engle. Armstrong participated in both the Gemini and Apollo programs; Engle commanded the Space Shuttle Columbia.