The Research Airplane Program, a joint research effort by the National Aeronautics and Space Administration (formerly the National Advisory Committee on Aeronautics) and the military services, was conceived near the end of World War II to perform flight studies with a series of specially-constructed research aircraft in the then unexplored transonic-low-supersonic characteristics of full-scale aircraft in flight.
Although supersonic flight was first achieved in 1947, further research in the program resulted in notable increases in knowledge about the dynamics of manned flight in winged aircraft at speeds up to and in excess of 4500 mph and at altitudes up to and greater than 350,00 ft.
Two general categories of aircraft were obtained for the research airplane program: (1) those obtained to explore new areas of performance, such as the X-1, D-558 I, D-558 II, X-1A, X-1B, X-1E, X-2, and X-15; and (2) those obtained to investigate the effects of different airplane configurations, such as the X-3, X-4, X-5, XB-70, and the lifting bodies.
The outstanding contributions of this research program include providing important information on previously unexplored aircraft characteristics; validating the transonic-supersonic characteristics predicted by wind-tunnel tests and analytical techniques; and the intangible benefit of providing confidence in the achievement of safe, controllable, transonic-supersonic flight.
The first of the rocket-powered research aircraft, the X-1 (originally designated the XS-1), was a bullet-shaped airplane that was built by the Bell Aircraft Company for the US Air Force and the National Advisory Committee on Aeronautics (NACA). The mission of the X-1 was to investigate the transonic speed range (speeds from just below to just above the speed of sound) and, if possible, to break the "sound barrier".
The first of the three X-1s was glide-tested at Pinecastle Air Force Base, FL, in early 1946. The first powered flight of the X-1 was made on Dec. 9, 1946, at Edwards Air Force Base with Chalmers Goodlind, a Bell test pilot, at the controls.
On Oct. 14, 1947, with USAF Captain Charles "Chuck" Yeager as pilot, the aircraft flew faster than the speed of sound for the first time. Captain Yeager ignited the four-chambered XLR-11 rocket engines after being air-launched from under the bomb bay of a B-29 at 21,000 ft. The 6,000-lb thrust ethyl alcohol/liquid oxygen burning rockets, built by Chemical Reaction Motors, Inc., pushed him up to a speed of 700 mph in level flight. Captain Yeager was also the pilot when the X-1 reached its maximum speed, 957 mph. Another USAF pilot. Lt. Col. Frank Everest, Jr., was credited with taking the X-1 to its maximum altitude of 71,902 ft. Eighteen pilots in all flew the X-1s. The number three plane was destroyed in a fire before ever making any powered flights.
A single-place monoplane, the X-1 was 31 ft long, 10 ft high, and had a wing span of 29 ft. It weighed 4,900 lb and carried 8,200 lb of fuel. It has a flush cockpit with a side entrance and no ejection seat.
A single-place, straight-wing, jet-powered aircraft, the D-558 I "Skystreak" was manufactured by Douglas Aircraft, Inc. for a joint Navy/NACA flight research program. It was designed to investigate jet aircraft characteristics at transonic speeds, including stability and control and buffet investigations. The instrumentation used onboard this airplane to record detailed wing and tail pressures was designed at Langley Research Center, Hampton, VA, during the 1930's for use on dirigibles.
The D-558 I was 35 ft long and 12 ft high, with a wingspan of 25 ft. It weighed 10,258 lb when fully fueled. One General Electric TG-180 jet engine with 4000 lb of thrust powered the D-558 I, which took off and landed under its own power.
The first flight of the aircraft, of which three were built, was on Apr. 14, 1947, with Gene May, Douglas test pilot, at the controls. Its maximum speed of 650.8 mph, then a world record for turbojet powered aircraft, was achieved by Lt. Col. Marion Carl, USMC, on Aug. 25, 1947. It reached a peak altitude of 45,000 ft.
The X-4, a single-place, low swept-wing, semi-tailless aircraft was designed and built by Northrop Aircraft, Inc., for NACA. It had no horizontal tail surfaces and its mission was to obtain in-flight data on the stability and control of semi-tailless aircraft at high subsonic speeds. The two X-4 aircraft were 23 ft long, 14 ft high, and had wingspans of 26 ft. They weighed almost 8,000 lb at takeoff.
The X-4 was powered by two Westinghouse XJ-30 turbojet engines with 1,600 lb of thrust each. These engines boosted the X-4 up to speeds of 620 mph and up to altitudes of 40,000 ft.
The aircraft's maiden flight was on Dec. 16, 1948, with Charles Tucker, a Northrop test pilot, at the controls.
The X-4 helped demonstrate that tail surfaces are important for proper control effectiveness in the transonic speed range, and was also used to investigate the characteristic problems of tailless airplanes at low speeds, such as marginal longitudinal stability and control.
Three D-558 II "Skyrockets" were built by Douglas Aircraft Inc. for NACA and the Navy. The mission of the D-558 II program was to investigate the flight characteristics of a swept-wing aircraft at high supersonic speeds. Particular attention was given to the problem of "pitch-up," a phenomena often encountered with swept-wing configured aircraft.
The D-558 II was a single-place, 35 degree swept-wing aircraft measuring 45 ft in length. It was 11.5 ft high and had a wingspan of 25 ft. Fully fueled it weighed about 16,000 lb.
The first of the three D-558 IIs had a Westinghouse J-34-40 jet engine and took off under its own power. The second was equipped with a J-34-40 jet engine and a Reaction Motors Inc., LR8-RM-6 rocket engine. The jet engine was for takeoff and climbing to altitude and the four-chambered rocket engine was for reaching supersonic speeds. This aircraft was modified so it could be air-launched from a B-29 carrier aircraft and the jet engine was removed to make room for extra propellant tanks. The third Skyrocket had the jet engine and the rocket engine but was also modified so it could be air-launched. The rocket engine was rated at 6,000 lb of thrust.
The D-558 II was first flown on Feb. 4, 1948, by John Martin, a Douglas test pilot. A NACA pilot, Scott Crossfield, became the first man to fly faster than twice the speed of sound when he piloted the D-558 II to its maximum speed of 1,291 mph on Nov. 20, 1953. Its peak altitude, 83,235 ft, a record in its day, was reached with USMC Lt. Col. Marion Carl behind the controls.
The X-5 was the first aircraft capable of sweeping its wings in flight. It was a single-place jet-powered aircraft, measuring 36 ft in length with a wingspan of 19 ft (with the wings swept back 60 degrees). The wings could be swept back 20 to 60 degrees. The X-5 weighed 10,000 lb when fully fueled.
Its mission was to study the effect of wing-sweep angles of 20, 45, and 60 degrees at subsonic and transonic speeds. Results from these tests provided some of the design background for the F-111 and the Navy F-14 tactical aircraft.
Two X-5s were manufactured by Bell Aircraft Company. The X-5 was powered by an Allison J-45-A jet engine with a static thrust of 4,900 lb. The maximum speed was 716 mph and the maximum altitude reached was 49,919 ft. The aircraft was equipped with and ejection seat.
The first flight was completed on June 20, 1951, with Jean Ziegler, a Bell test pilot, at the controls.
Results of the research program provided a significant full-scale verification of NASA wind-tunnel predictions for the reduced drag and improved performance resulting from increasing the wing sweep as the speed of the aircraft approaches the speed of sound. The pilots found they could use the variable wing sweep as a tactical control to out-perform the accompanying escort aircraft during research missions.
It was a single-place aircraft, 42 ft long and 17 ft high, with a wingspan of 31 ft. With fuel, it weighed 15,500 lb. The XF-92A took off and landed under its own power using an Allison J-33-A jet engine, equipped with afterburner capability, rated at 7,500 lb of thrust.
The XF-92A, built by the Convair Aircraft Company, had a maximum speed of approximately the speed of sound and a peak altitude of 42,464 ft.
Stability and control, pitch-up and lift/drag measurements obtained from the XF-92A helped build up the technology that was used to develop such delta-wing aircraft as the F-102, F-106, B-58 and other high-performance aircraft.
A single-place jet aircraft, the X-3 had a slender fuselage and a long tapered nose. Its primary mission was to investigate the design features of an aircraft suitable for sustained supersonic speeds.
The X-3 was manufactured by the Douglas Aircraft Company. There was only one model produced. It was 66 ft long, 12 ft high and had a wingspan of 22 ft. Two Westinghouse XJ-35 turbojets, equipped with afterburners, powered the X-3. It was capable of takeoff and landing under its own power.
The top speed of the aircraft was just over the speed of sound. It reached and altitude of 41,318 ft.
A secondary purpose of the X-3 was to test new materials such as titanium.
The X-1A, X-1B, and the X-1D were growth versions of the X-1. They were almost five feet longer, had an improved rocket propellent system and conventional canopies. The X-1A and X-1B were modified to have ejection seats.
Their mission was to continue the X-1 studies at higher speeds and altitudes. The X-1A was the first to begin this research after the X-1D was destroyed in an explosion on a captive flight before making any research flights. On Dec. 12, 1953, Major Charles Yeager flew the X-1A up to a speed of 1,612 mph (almost two and a half times the speed of sound). Then on Aug. 26, 1954, Major Arthur Murray took the X-1A up to an altitude of 90,440 ft. Those two performances were the records for the X-1 program. Later the X-1A was also destroyed after being jettisoned from the carrier aircraft because of an explosion.
The X-1B was fitted with special instrumentation for exploratory aerodynamic heating tests. It had over 300 thermocouples installed on it. It also was the first aircraft to fly with a reaction control system, a prototype of the control system used on the X-15 and other manned aircraft. The X-1C was cancelled before production.
All three of the Bell Aircraft Company manufactured planes had a 6,000-lb thrust, XLR-11 four-chambered rocket engine. The XLR-11 was built by Reaction Motors Inc. The aircraft were all air-launched from a carrier aircraft.
The X-2 was a swept-wing aircraft designed to fly three times faster than the speed of sound. It was flown to investigate the problems of aerodynamic heating and stability and control effectiveness at high speeds and altitudes.
The X-2 was a single-place airplane with wings swept back to 40 degrees. It was 37 ft, 10 in. long, 11 ft high and had a wingspan of 32.3 ft. It was constructed primarily of steel (K-monel) and incorporated a skid-type main landing gear to make more room for fuel. It had an ejectable nose capsule.
The X-2 was powered by an XLR25-CW-3 two-chambered rocket engine. The Curtiss-Wright manufactured engine had a thrust of 15,000 lb. Two X-2s were made for NACA and the Air Force by Bell Aircraft Co. They were air launched from a B-50 carrier aircraft.
After one X-2 (no. 2 aircraft) was destroyed in an explosion on a captive flight before ever making any powered flights, the other X-2 (no. 1 aircraft) went on to perform as predicted including making a flight on Sept. 7, 1956, with Air Force Captain Iven Kincheloe at the controls to an altitude of 126,200 ft. Twenty days later the X-2 program ended when Air Force Captain Milburn Apt piloted the X-2 to its highest speed of 2,094 mph (over three times the speed of sound) before it went out of control and crashed. Captain Apt was fatally injured in the crash.
The number two X-1 was modified and redesignated the X-1E. The modifications included adding a conventional canopy, an ejection seat, a low-pressure fuel system of increased capacity, and a thinner high-speed wing.
The X-1E was used to obtain in-flight data at twice the speed of sound, with particular emphasis placed on investigating the improvements achieved with the high-speed wing. These wings, made by Stanley Aircraft, were only 3 - 3/8-in. thick at the thickest point and had 343 gauges installed in them for measurement of structural loads and aerodynamic heating.
The X-1E used the XLR-11 rocket engine from the X-1 to power it up to a speed of 1,471 mph and to an altitude of 73,458 ft. Like the X-1 it was air launched.
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 lb empty and approximately 34,000 lb at launch. The rocket engine, the XLR-99, was pilot controlled and was capable of developing 57,000 lb of thrust. It was manufactured by Thiokol Chemical Corp.
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 vertical stabilizers to control yaw and horizontal stabilizers which 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 ballistic control system. Eight hydrogen peroxide thrust rockets located on the nose of the aircraft provided pitch and yaw 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.
First flown in 1959, the three X-15 aircraft made a total of 199 flights. Flight maximums of 354,200 ft in altitude and a speed of 4,520 mph were obtained. Final flight was flown on Oct. 24, 1968. The X-15 was manufactured by North American Aviation, now known as Rockwell International Corporation.
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.
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.
The XB-70 was the world's largest experimental aircraft. Capable of flight at speeds of three times the speed of sound (2,000 mph) at altitudes of 70,000 ft, the XB-70 was used to collect in-flight information for use in the design of future supersonic aircraft, military and civilian.
The major objectives of the XB-70 flight research program were to study the airplane's stability and handling characteristics, to evaluate its response to atmospheric turbulence, and to determine the aerodynamic and propulsion performance. In addition there were secondary objectives to measure the noise and friction associated with air flow over the airplane and to determine the levels and extent of the engine noise during take off, landing, and ground operations.
The XB-70 was 189 ft long, 30 ft high, with a wingspan of 105 ft. Fully fueled it weighed over 500,000 lb.
Originally conceived as an advanced bomber for the United States Air Force, production of the XB-70 was limited to two aircraft when it was decided to limit the aircraft's mission to flight research. First flight of the XB-70 was made on Sept. 21, 1964. The number two XB-70 was destroyed in a mid-air collision on June 8, 1966. Program management of the NASA-USAF research effort was assigned to NASA in Mar., 1967. The final flight was flown on Feb. 4, 1969.
Designed by Rockwell International (North American Rockwell) the XB-70 had a long fuselage with a canard or horizontal stabilizer mounted just behind the crew compartment. It had a thin 65.5 degree swept delta wing. The outer portion of the wing could be folded down in flight to provide greater lateral-directional stability. The airplane had two windshields: a moveable outer windshield was raised for high-speed flight to reduce drag and lowered for greater visibility during take off and landing. The forward fuselage was constructed of riveted titanium frames and skin. The remainder of the airplane was constructed almost entirely of stainless steel. The skin was a brazed stainless-steel honeycomb material. Six General Electric YJ-93 turbojet engines, each in the 30,000-lb thrust class, powered the XB-70. Internal geometry of the inlets was controllable to maintain most efficient airflow to the engines.
Final flight was on Feb. 4, 1969, with Fulton and Sturmthal as crew.
Fastest mph flight was on Jan. 12, 1966, speed was 2,020 mph with White and Cotton as crew.
Fastest Mach flight was on Apr. 12, 1966, achieved Mach 3.08 with White and Cotton as crew.
Highest flight was on Mar. 19, 1966, attained 74,000 ft with White and Shepard as crew.
Total flight time is 252 hr and 38 min. Breakdown of flight time is: Subsonic, 145 hr and 28 min; Mach 1-2, 55 hr and 50 min; Mach 2-3, 49 hr and 32 min; Mach 3, 1 hr and 48 min.
Modified: February 2, 1994