The X-15 Rocket Plane
The North American X-15 rocket plane was built to meet a challenge. It was designed to fly at speeds up to Mach 6, and altitudes up to 250,000 ft. The aircraft went on to reach a maximum speed of Mach 6.7 and a maximum altitude of 354,200 ft. Looking at it another way, Mach 6 is about one mile per second, and flight above 265,000 ft. qualifies an Air Force pilot for astronaut wings.
The X-15 was a rocket-powered aircraft 50 ft long with a wingspan of 22 ft. It was a missile-shaped vehicle with an unusual wedge-shaped vertical tail, thin stubby wings, and unique side fairings that extended along the side of the fuselage. The X-15 weighed about 14,000 lbs empty and approximately 34,000 lbs at launch. The XLR-99 rocket engine, manufactured by Thiokol Chemical Corp., was pilot controlled and was capable of developing 57,000 lbs of thrust.
North American Aviation built three X-15 aircraft for the program. 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 rudders on the vertical stabilizers to control yaw and movable horizontal stabilizers 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 controlled roll.
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 plane was air launched by NASA's converted B-52 at 45,000 feet and a speed of 500 mph.
The X-15 was actually the second stage of a two-stage system. The first stage was a B-52 bomber, specially modified for the program, which carried the X-15 up-range into Nevada, pointed it towards Edwards, and launched it at 45,000 feet and 0.8 Mach number. The X-15 was usually launched about 200 miles from Edwards. The engine was lit immediately after launch and burned for about 85 seconds. During that period, it would boost the X-15 to an altitude of 160,000 feel and a Mach number of 5.4. The X-15 would then coast to 250,000 feet, reenter, and glide to a landing on the dry lake at Edwards. A typical X-15 flight lasted eleven minutes, including about four minutes in the traffic pattern. The X-15 would arrive and land at Edwards about 1 hour or more before the B-52 that launched it.
At approximately 0800 hours two pilots from Dryden would proceed up-range to evaluate the condition of the dry lake beds in the event of an emergency landing of the X-15. The most popular of these launch lakes were Mud, Delamar, Hidden Hills, Smith Ranch, Silver, Railroad Valley, Rosamond, and Cuddeback. On occasion they would buzz Beatty and Ely on their way out and on the way back just to make sure they were awake and knew what time it was.
High Range Tracking Stations Ely (NASA 3) and Beatty (NASA2):
NASA contractors for the X-15 program were Bendix Field Engineering followed by Unitec, Inc. The NASA High Range Tracking stations were located at Ely (NASA 3) and Beatty (NASA 2) Nevada with main control being at Dryden/Edwards AFB in California (NASA 1). “radar“ Personnel at the tracking stations consisted of a Station Manager, a Technical Advisor, and field engineers for the Mod-2 Radar, Data Transmission System, Communications, Telemetry, and Plant Maintenance/Generators. NASA had a site monitor at each tracking station to monitor our contractor operations.
On mission days a NASA van picked up each member of the crew at their residence for the 4:20 a.m. trip to the tracking station 18 miles North of Beatty on the Tonopah Highway. Upon arrival each performed preflight calibrations and setup of their various systems. The liftoff of the B-52, with the X-15 tucked beneath its wing, seldom occurred after 9:00 a.m. due to the heat effect of the Mojave Desert making it difficult for the planes to acquire altitude.
Though supporting flights of the X-15 was their main objective, they also participated in flights of the XB-70, the three Lifting Bodies, experimental Lunar Landing vehicles, and an occasional A-12/YF-12/SR-71 Blackbird flight.
USAF/NASA Betty High Range Tracking Station was deactivated at the end of the X-15 flights.
USAF/NASA Ely High Range Tracking Station was located on Kimberly Peak, located just a few miles North of the tiny community of Ruth, & 9 miles NW of the city of Ely Nevada was the chosen location for the northernmost tracking station, with the Yelland Field -- Ely's local airport, being used to ferry important equipment & visiting personnel to the area from Edwards AFB. Construction of the 5.8 mile long access road -- never paved-- was completed in October 1957, and then a level clearing measuring 100'x100' was blasted into the peak for the construction of the buildings. The Kimberly Peak Tracking Facility achieved initial operating capability in April 1961, at a total cost of $2,688,000 for the access road, 1780 square foot building (with equipment) and outbuildings such as the Power Bldg. The USAF provided most of the funds, with the understanding that NASA (in the early days, it was still known as NACA) would operate the site, but turn it over to the AF Flight Test Center once the X-15 program concluded. USAF/NASA Ely High Range Tracking Station was taken over by NASA and operated until 1 April, 1979 when NASA mothballed the site.
Generally there were two types of flight profiles: high-speed, or high-altitude. High-speed flights were usually done below an altitude of 100,000 feet and flown as a conventional airplane using aerodynamic controls. High-altitude flights began with a steep, full-power climb to leave the atmosphere, followed by up to two minutes of "coasting up" to the peak altitude after the engine was shut down. "Weightless" flight would last for 2 - 5 minutes as it made a ballistic arc before reentering the atmosphere.
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 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 piloted spaceflight programs, and also the Space Shuttle program.
The North American Aviation X-15s made a total of 199 flights. There were 196 successful landings in the program, and the two landing accidents that occurred were related to system or structural failures and not to pilot error. 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. X-15-3, serial number 56-6672, crashed on 15 November 1967, resulting in the death of Maj. Michael J. Adams. Parts of the X-15-3 are on display at the Air Force Flight Test Center Museum at Edwards AFB, and the San Diego Aerospace Museum, San Diego, California.
The X-15 flew to an altitude of 354,000 feet and reached a Mach number of 6.70. It flew its last flight over forty seven years ago, but to this day, except for the Space Shuttle no aircraft has flown half as high nor half as fast. The late Dr. Hugh L. Dryden termed it "the most successful research airplane in history."
The X-15 program made many accomplishments, some of which include:
First use of a full-pressure suit for spaceflight.
First use of reaction controls for maneuvering in space.
First use of a flight control system that automatically blended aerodynamic and reaction controls.
Development of thermal protection for hypersonic reentry.
Development of the first large, re-startable, and throttleable rocket engine.
Development of inertial flight data systems capable of functioning in a high-dynamic-pressure and space environment.
Demonstration of a pilot's ability to operate in "micro-gravity".
Demonstration of the first piloted reentry-to-landing from space.
Acquisition of hypersonic acoustic measurements, which influenced structural design criteria for Mercury capsule.
Verification of the validity of hypersonic wind tunnel data, which were later used in the design of the Space Shuttle.
X-15 Pilots in chronological order with total flights:
A. Scott Crossfield, NAA, 14
Joseph A. Walker, NASA, 25
Robert M. White, USAF, 16
Forrest S. Petersen, USN, 5
John B. "Jack" McKay, NASA, 29
Robert A. Rushworth, USAF, 34
Neil A. Armstrong, NASA, 7
Joe H. Engle, USAF, 16
Milton O. Thompson, NASA, 14
William J. "Pete" Knight, USAF, 16
William H. Dana, NASA, 16
Michael J. Adams, USAF, 7
X-15 Flight Summary:
Fastest speed (basic aircraft) was 4,104 mph (Mach 6.06) on flight 1-30-51 with pilot Joe Walker.
Fastest speed with tanks was 4,520 mph (Mach 6.70) on flight 2-53-97 with pilot William Knight.
Highest altitude was 354,200 ft (67 miles) on flight 3-22-36 with Joseph Walker.
Total flight time was 30 hr, 13 min. and 49.2 sec.
Total distance flown was 41,763.8 miles (statute).
Total flights of the X-15 was 199 between 1959 and 1968.
Hours above Mach (Cumulative):
Mach 1 - 18 hr, 23 min. and 11.6 sec
Mach 2 - 12 hr, 13 min., and 50 sec
Mach 3 - 8 hr, 51 min., and 12.8 sec
Mach 4 - 5 hr, 57 min., and 23.8 sec
Mach 5 - 1 hr, 27 min., and 15.8 sec
Mach 6 - 1 min. and 16.8 sec