Purpose:
The Bell X-1 rocket aircraft was designed specifically for research in the transonic speed range. Aircraft of the period, including F-80 and F-84 Jets, were limited to Mach numbers near 0.8 and 0.85 and could reach these speeds only in hazardous dives. In reaching subsonic speeds, these aircraft were virtually uncontrollable making it desirable to build a research aircraft which would be slowed merely by cutting the engine. Advanced X-1 series emphasized research in such areas as aerodynamic heating, pilot reaction control systems, and problems of supersonic flight.

Description:
The bullet-shaped X-1 was propelled by a four-chambered, liquid-fueled rocket engine: An improved version, the X-1A, featured turbo-driven fuel pumps, nitrogen-pressure fuel feed, increased fuel capacity, longer fuselage, and a nitrogen-pressurized cockpit modified for improved visibility.

Significant occurrences:
The Air Force took over the flight test program from the contractor on 27 July 1947 and although data accumulated
during the first few flights indicated that the X-1 would not break the sound barrier, Capt. Charles Yeager on 14 October 1947 exceeded the speed of sound in level flight. Later flights established the top speed of the X-1 at 967 mph and the maximum altitude attained was 73,000 feet. The second X-1 went to the NACA and after testing and modernizing in 1951 and 1954 was re designated the X-1E. The third X-1 was destroyed by an explosion during contractor testing on a captive flight on 9 Nov. 1951. The X-1A made its first powered flight on 21 Feb. 1953; Major Yeager reached a speed of 1,650 mph in the aircraft on 12 Dec. 1953 and Major Arthur Murray attained an altitude of 90,000 feet in the craft on 4 June 1954. The plane was transferred to the NACA on 1 March 1955 but was destroyed in an explosion on 8 August 1955.

Contributions:
The X-1 became the first aircraft to exceed the speed of sound in level flight and provided data on control, stability, buffeting, and other aerodynamic phenomena associated with transonic and supersonic flight. The X-1B was modified for investigation of aerodynamic heating and characteristics of reaction controls and during a three-year test program provided NACA with data on heat flow, effects of internal heat sources and sinks, and the effects of boundary-layer transition and aerodynamic interference. Research into reaction controls during the X-1B test series involved test flights at altitudes above 90,000 feet and paved the way for the hydrogen peroxide reaction system used in the X-15.

On October 14, 1947, flying the Bell XS-1 #1, Capt. Charles 'Chuck' Yeager, USAF, became the first pilot to fly faster
than sound. The XS-1, later designated X-l, reached Mach 1.06, 700 mph, at an altitude of 43,000 feet, over the Mojave Desert near Muroc Dry Lake, California. The flight demonstrated that aircraft could be designed to fly faster than sound, and the concept of a 'sound barrier" crumbled into myth.

The XS-1 was developed as part of a cooperative program initiated in 1944 by the National Advisory Committee for Aeronautics (NACA) and the U.S. Army Air Forces (later the U.S. Air Force) to develop special manned transonic and supersonic research aircraft. On March 16, 1945, the Army Air Technical Service Command awarded the Bell Aircraft Corporation of Buffalo, New York, a contract to develop three transonic and supersonic research aircraft under project designation MX-653. The Army assigned the designation XS-1 for Experimental Sonic-i. Bell Aircraft built three rocket-powered XS-1 aircraft.

The National Air and Space Museum now owns the XS-1 #1, serial 46-062, named Glamorous Glennis by Captain Yeager in honor of his wife. The XS-1 #2 (46-063) was flight-tested by NACA and later was modified as the X-1[ Mach 24" research airplane. (The X-1 E is currently on exhibit outside the NASA Flight Research Center, Edwards, California.) The X-1 #3 (46-064) had a turbo pump-driven, low-pressure fuel feed system. This aircraft, known popularly as the X-1-3 Queenie, was lost in a 1951 explosion on the ground that injured its pilot. Three additional X-1 aircraft, the X-1A, X-1B, and X-1D, were constructed and test-flown. Two of these. the X-1A and X-1D, were also lost, as a result of propulsion system explosions.

The two XS-1 aircraft were constructed from high-strength aluminum, with propellant tanks fabricated from steel. The first two XS-1 aircraft did not utilize turbo pumps for fuel feed to the rocket engine, relying instead on direct nitrogen pressurization of the fuel-feed system. The smooth contours of the XS-1, patterned on the lines of a .50-caliber machine gun bullet, masked an extremely crowded fuselage containing two propellant tanks, twelve nitrogen spheres for fuel and cabin pressurization, the pilot's pressurized cockpit, three pressure regulators, a retractable landing gear, the wing carry-through structure, a Reaction Motors, Inc., 6.000-pound-thrust rocket engine, and more than five hundred pounds of special flight-test instrumentation.

Design Features:

Many important structural and aerodynamic advances were first employed in the Bell X-1, including extremely thin yet exceptionally strong wing sections and a horizontal stabilizer that could be adjusted up and down to improve control, especially at transonic (near the speed of sound) speeds. Because of the stabilizer's success, later transonic military aircraft were designed with all moving The X-1's fuselage was shaped like a .50 caliber bullet. Even the windscreen was specially flared to retain the bullet shape. The X-1 carried more than 230 kilograms (500 pounds) of flight test instruments.

The X-1 (originally designated the XS-1 for Experimental Supersonic), a rocket-powered research aircraft, was a
bullet-shaped airplane that was built by the Bell Aircraft Corporation, Buffalo, N.Y., for the U.S. Army Air Forces and the National Advisory Committee for Aeronautics (NACA).The mission of the X-1s 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." There were three X-1s built with the designations as follows:
X-1-1 (46-062), X-1-2 (46-063), X-1-3 (46-064), that were flown by eighteen pilots from 1946 to 1951.

Though originally designed for conventional ground takeoffs, all X-1 aircraft were air-launched from Boeing B-29 or B-50 Super fortress aircraft. The performance penalties and safety hazards associated with operating rocket-propelled aircraft from the ground caused mission planners to resort to air-launching instead. Nevertheless, on January 5,1949, the X-1 #1 Glamorous Glennis successfully completed a ground takeoff from Muroc Dry Lake, piloted by Chuck Yeager. The maximum speed attained by the X-1 #1 was Mach 1.45 at 40,130 feet, approximately 957 mph, during a flight by Yeager on
March 26, 1948. On August 8,1949, Maj. Frank K. Everest, Jr., USAF, reached an altitude of 71,902 feet, the highest flight made by the little rocket airplane. It continued flight test operations until mid-1950, by which time it had completed a total of nineteen contractor demonstration flights and fifty-nine Air Force test flights.

The Bell Aircraft Corporation X-1-2 Sitting on the ramp at NACA High-Speed Flight Research Station with the Boeing B-29 launch ship behind . The B-29 was fondly referred to as "Fertile Myrtle". The painting near the nose depicts a stork carrying a bundle which is symbolic of the Mother ship launching her babe (X-1-2). The pilot access door is open to the cockpit of the X-1-2 aircraft.

On August 26, 1950, Air Force Chief of Staff Gen. Hoyt Vandenberg presented the X-1 #1 to Alexander Wetmore, then Secretary of the Smithsonian Institution. The X-1, General Vandenberg stated, "marked the end of the first great period of the air age, and the beginning of the second. In a few moments the subsonic period became history and the supersonic period was born." Earlier, Bell Aircraft President Lawrence D. Bell, NACA scientist John Stack, and Air Force test pilot Chuck Yeager had received the 1947 Robert J. Collier Trophy for their roles in first exceeding the speed of sound and opening the pathway to practical supersonic flight.

FASTER THAN SOUND

Higher speeds brought their problems. Even the faster piston-engine fighters sometimes ran into trouble during high-speed dives, losing their wings or tails for no apparent reason. Designers knew that their enemy was the invisible, seemingly harmless air, which became so compressed by the speeding aircraft that it formed almost solid shock-waves that hammered the structure until it broke up.

The shock-waves form when airflow over any part of the aircraft's structure reaches the speed of sound, which is 760 mph at sea level, dropping to 660 mph above 36,000 ft. By sweeping back the wings of their aircraft and making them thinner, designers managed to delay the shock-wave effects and gain a few extra precious miles per hour; but many experts doubted that aeroplanes would ever be able to fly above the speed of sound and newspapers began to write about the "sound barrier".

To discover if a specially-designed aircraft with a very powerful engine would be able to penetrate the barrier, the British government ordered a bullet shaped research monoplane from the Miles company. It then got cold feet and cancelled the project.

In the USA, work continued on a small rocket powered research aircraft known as the Bell XS-1 (later X-1), intended for a similar purpose. The pilot chosen for the attempt to smash through the sound barrier to supersonic speed was Captain Charles Yeager, who had no illusions about the hazards confronting him. Everything about the program was strange and rather like science fiction. To conserve fuel, it was even necessary to drop the X-I from a converted bomber at a height of around 30,000 ft, instead of taking off normally.

Each time he flew, Yeager approached a little nearer to the speed of sound. Eventually he reached a speed of Mach 0.94 (94 per cent of the speed of sound), and felt the aircraft bucking under the hammer blows of shock waves that would have smashed anything else in the air at that time. But he had complete confidence in the X-I's structure and finally, on October 14, 1947, he opened up the four-chamber rocket engine to full power for an all-out attempt to reach supersonic speed. Fighting to keep control, he watched the needle on the Machmeter swing past Mach .94, on to .96, .98 . . . suddenly, instead of getting worse, the hammering stopped. Yeager had become the first man to fly into the calmer conditions that lie beyond the "sound barrier". In doing so, he had proved that the barrier does not really exist.

By 1956, Britain's delta-wing Fairey Delta 2 research aircraft, powered by an ordinary jet-engine, was able to demonstrate that a properly-designed aeroplane can approach and pass the speed of sound with no more noticeable effect than a flicker of needles on the cockpit instruments as it does so. From that moment, it became only a matter of time..

Wingspan: 8.5 m (28 ft) Length: 9.4 m (30 ft 11 in) Height: 3.3 m (10 ft 10 in) Weight, gross: 5,557 kg (12,250 lb) Engine: Reaction Motors, Inc., XLR-11-RM-3 (model A6000C4) 4-chamber rocket engine, rated at 26,500 newtons (6,000 lb) static thrust Manufacturer: Bell Aircraft Co., Buffalo, N.Y., 1946