|X-1 #46-062, nicknamed "Glamorous Glennis".|
|Role||Experimental rocket plane|
|Manufacturer||Bell Aircraft Company|
|First flight||19 January 1946|
|Primary users||U.S. Air Force
National Advisory Committee for Aeronautics
The Bell X-1, designated originally as XS-1, was a joint National Advisory Committee for Aeronautics-U.S. Army Air Forces-U.S. Air Force supersonic research project built by the Bell Aircraft Company. Conceived during 1944 and designed and built during 1945, it achieved a speed of nearly 1,000 miles per hour (1,600 km/h; 870 kn) during 1948. A derivative of this same design, the Bell X-1A, having greater fuel capacity and hence longer rocket burning time, exceeded 1,600 miles per hour (2,600 km/h; 1,400 kn) during 1954. The X-1 was the first manned airplane to exceed the speed of sound in level flight and was the first of the so-called X-planes, a series of American experimental rocket planes designated for testing of new technologies and often kept secret.
Design and development
On 16 March 1945, the U.S. Army Air Forces Flight Test Division and the National Advisory Committee for Aeronautics (NACA) contracted with the Bell Aircraft Company to build three XS-1 (for "Experimental, Supersonic", later X-1) aircraft to obtain flight data on conditions in the transonic speed range.
The X-1 was in principle a "bullet with wings", its shape closely resembling a Browning .50-caliber (12.7 mm) machine gun bullet, known to be stable in supersonic flight. The pattern shape was followed to the extent of seating its pilot behind a sloped, framed window inside a confined cockpit in the nose, with no ejection seat. After the rocket plane experienced compressibility problems during 1947, it was modified with a variable-incidence tailplane thanks to the British who in an agreement with the US government (to develop a joint supersonic fighter) handed over the all-moving tail and associated turbojet data developed for the Miles M.52 to Bell and used in transonic flight on the X-1, allowing it to pass through the sound barrier safely, unfortunately the USA subsequently reneged on the agreement.    
The rocket propulsion system was a four-chamber engine built by Reaction Motors, Inc., one of the first companies to build liquid-propellant rocket engines in the U.S.. This rocket burned ethyl alcohol diluted with water with a liquid oxygen oxidizer. Its thrust could be changed in 1,500 lbf (6,700 N) increments by using just one or more than one of its chambers. The fuel and oxygen tanks for the first two X-1 engines were pressurized with nitrogen gas, but the rest used steam-driven turbopumps. The all-important fuel turbopumps were necessary to increase the chamber pressure and thrust while making the engine lighter.
Bell Aircraft chief test pilot Jack Woolams became the first person to fly the XS-1. He made a glide-flight over Pinecastle Army Airfield, in Florida, on 25 January 1946. Woolams completed nine more glide-flights over Pinecastle before March 1946, when the #1 rocket plane was returned to Bell Aircraft in Buffalo, NY, for modifications to prepare for the powered flight tests. These were performed at Muroc Army Air Field in Palmdale, California. After Woolams' death on 30 August 1946, Chalmers "Slick" Goodlin was the primary Bell Aircraft test pilot for the X-1-1 (serial 46-062). He made 26 successful flights in both X-1s from September 1946 through June 1947.
The Army Air Forces was unhappy with the cautious pace of flight envelope expansion and Bell Aircraft's flight test contract for airplane #46-062 was terminated. The test program was acquired by the Army Air Force Flight Test Division on 24 June after months of negotiation. Goodlin had demanded a US$150,000 bonus for exceeding the speed of sound. Flight tests of the X-1-2 (serial 46-063) would be conducted by NACA to provide design data for later production high-performance aircraft.
Mach 1 flight
On October 14, 1947, just less than a month after the U.S. Air Force had been created as a separate service, testings achieved their maximum with the first manned supersonic flight, piloted by Air Force Captain Charles "Chuck" Yeager in aircraft #46-062 that he had nicknamed Glamorous Glennis for his wife. This rocket-powered airplane was drop launched from the bomb bay of a modified B-29 Superfortress bomber, and it glided to a landing on the dry lake bed. XS-1 flight number 50 is the first one in which the X-1 recorded supersonic flight, at Mach 1.06 (700 miles per hour (1,100 km/h; 610 kn)).
As a result of the X-1's initial supersonic flight, the National Aeronautics Association voted its 1948 Collier Trophy to be shared by the three main participants of the program. Honored at the White House by President Truman were Larry Bell for Bell Aircraft, Captain Yeager for piloting the flights, and John Stack for the contributions of the NACA.
The story of Yeager’s October 14 flight was leaked to a reporter from the magazine Aviation Week, and The Los Angeles Times featured the story as headline news in their 22 December issue. The magazine story was released on 20 December. The Air Force threatened legal action against the journalists who revealed the story, but none ever occurred.
On January 5, 1949, Yeager used Aircraft #46-062 to perform the only conventional (runway) launch of the X-1 program, attaining 23,000 ft (7,000 m) in 90 seconds.
The research techniques used for the X-1 program became the pattern for all subsequent X-craft projects. The X-1 project assisted the postwar cooperative union between U.S. military needs, industrial capabilities, and research facilities. The flight data collected by the NACA from the X-1 tests then proved invaluable to further US fighter design throughout the latter half of the 20th century.
Later variants of the X-1 were built to test different aspects of supersonic flight; one of these, the X-1A, with Yeager at the controls, inadvertently demonstrated a very dangerous characteristic of fast (Mach 2 plus) supersonic flight: inertia coupling. Only Yeager's skills as an aviator prevented disaster; later Mel Apt would lose his life testing the Bell X-2 under similar circumstances.
Ordered by the Air Force on April 2, 1948, the X-1A (serial 48-1384) was intended to investigate aerodynamic phenomena at speeds greater than Mach 2 (681 m/s, 2,451 km/h) and altitudes greater than 90,000 ft (27 km), specifically emphasizing dynamic stability and air loads. Longer and heavier than the original X-1, with a bubble canopy for better vision, the X-1A was powered by the same Reaction Motors XLR-11 rocket engine. The aircraft first flew, unpowered, on 14 February 1953 at Edwards AFB, with the first powered flight on 21 February. Both flights were piloted by Bell test pilot Jean "Skip" Ziegler.
After NACA started its high-speed testing with the Douglas Skyrocket, culminating in Scott Crossfield achieving Mach 2.005 on 20 November 1953, the Air Force started a series of tests with the X-1A, which the test pilot of the series, Chuck Yeager, named "Operation NACA Weep". These culminated on 12 December 1953, when Yeager achieved an altitude of 74,700 feet (22,800 m) and a new airspeed record of Mach 2.44 (equal to 1620 mph, 724.5 m/s, 2608 km/h at that altitude). Unlike Crossfield in the Skyrocket, Yeager achieved that in level flight. Soon afterwards, the aircraft spun out of control, due to the then not yet understood phenomenon of inertia coupling. The X-1A dropped from maximum altitude to 25,000 feet (7,600 m), exposing the pilot to accelerations of as much as 8g, during which Yeager broke the canopy with his helmet before regaining control.
The aircraft was transferred to NACA during September 1954. After modifications, including the installation of an ejection seat, the aircraft was lost on August 8, 1955 while being prepared for launch from the RB-50 mothership, becoming the first of many early X-planes that would be lost to explosions.
The X-1B (serial 48-1385) was equipped with aerodynamic heating instrumentation for thermal research (more than 300 thermal probes were installed on its surface). It was similar to the X-1A except for having a slightly different wing. The X-1B was used for high-speed research by the U.S. Air Force starting from October 1954, prior to being transferred to the NACA during January 1955. NACA continued to fly the aircraft until January 1958 when cracks in the fuel tanks forced its grounding. The X-1B completed a total of 27 flights. A notable achievement was the installation of a system of small reaction rockets used for directional control, making the X-1B the first aircraft to fly with this sophisticated control system, later used in the North American X-15. The X-1B is now at the National Museum of the United States Air Force, Wright-Patterson Air Force Base at Dayton, Ohio, where it is displayed in the Museum's Research & Development Hangar.
The X-1C (serial 48-1387) was intended to test armaments and munitions in the high transonic and supersonic flight regimes. It was canceled while still in the mockup stage, as the development of transonic and supersonic-capable aircraft like the North American F-86 Sabre and the North American F-100 Super Sabre eliminated the need for a dedicated experimental test vehicle.
The X-1D (serial 48-1386) was the first of the second generation of supersonic rocket planes. Flown from an EB-50A (s/n #46-006), it was to be used for heat transfer research. The X-1D was equipped with a new low-pressure fuel system and a slightly increased fuel capacity. There were also some minor changes of the avionics suite.
On 24 July 1951, with Bell test pilot Jean "Skip" Ziegler at the controls, the X-1D was launched over Rogers Dry Lake, on what was to become the only successful flight of its career. The unpowered glide was completed after a nine-minute descent, but upon landing, the nose landing gear failed and the aircraft slid ungracefully to a stop. Repairs took several weeks to complete and a second flight was scheduled for mid-August. On 22 August 1951, the X-1D was lost in a fuel explosion during preparations for the first powered flight. The aircraft was destroyed upon impact after it was jettisoned from its EB-50A mothership.
The X-1E was the result of a reconstruction of the X-1-2 (serial 46-063), in order to pursue the goals originally set for the X-1D and X-1-3 (serial 46-064), both lost by explosions during 1951. The cause of the mysterious explosions was finally traced to the use of Ulmer leather gaskets impregnated with tricresyl phosphate (TCP), a leather treatment, which was used in the liquid oxygen plumbing. TCP becomes unstable and explosive in the presence of pure oxygen and mechanical shock. This mistake cost two lives, caused injuries and lost several aircraft.
The changes included:
- A turbopump fuel feed system, which eliminated the high-pressure nitrogen fuel system used in '062 and '063. (Concerns about metal fatigue in the nitrogen fuel system resulted in the grounding of the X-1-2 after its 54th flight in its original configuration.)
- A re-profiled super-thin wing (3 3⁄8 inches at the root), based on the X-3 Stiletto wing profile, enabling the X-1E to reach Mach 2.
- A 'knife-edge' windscreen replaced the original greenhouse glazing, an upward-opening canopy replaced the fuselage side hatch and allowed the inclusion of an ejection seat.
- The addition of 200 pressure ports for aerodynamic data, and 343 strain gauges to measure structural loads and aerodynamic heating along the wing and fuselage.
The X-1E first flew on 15 December 1955, a glide-flight controlled by USAF test pilot Joe Walker. Walker left the X-1E program during 1958, after 21 flights, attaining a maximum speed of Mach 2.21 (752 m/s, 2,704 km/h). NACA research pilot John B. McKay took his place during September 1958, completing five flights in pursuit of Mach 3 (1,021 m/s, 3,675 km/h) before the X-1E was permanently grounded after its 26th flight, during November 1958, due to the discovery of structural cracks in the fuel tank wall.
Aircraft on display
- X-1-1, Air Force Serial Number 46-062, is currently displayed in the Milestones of Flight gallery of the National Air and Space Museum in Washington, DC, alongside the Spirit of St. Louis and SpaceShipOne.
- X-1B, AF Ser. No. 48-1385, is on display in the Research & Development Hangar at the National Museum of the United States Air Force, Wright-Patterson Air Force Base, Ohio.
- X-1E, AF Ser. No. 46-063, is on display in front of the NASA Dryden Flight Research Center headquarters building at Edwards Air Force Base, California.
Specifications (Bell X-1)
- Crew: one
- Length: 30 ft 11 in (9.4 m)
- Wingspan: 28 ft (8.5 m)
- Height: 10 ft (3.3 m)
- Wing area: 130 ft² (12 m²)
- Empty weight: 7,000 lb (3,175 kg)
- Loaded weight: 12,225 lb (5,545 kg)
- Max. takeoff weight: 12,250 lb (5,557 kg)
- Powerplant: one × Reaction Motors XLR-11-RM3 liquid fuel rocket, 6,000 lbf (1,500 lbf per chamber) (26.7 kN) each
- Color : International Orange (same color as the Golden Gate Bridge)
- Maximum speed: 957 mph (Mach 1.26) (1,541 km/h)
- Range: five minutes (powered endurance)
- Service ceiling: 71,902 ft (21,916 m)
- Wing loading: 94 lb/ft² (463 kg/m²)
- Thrust/weight: 0.49
Specifications (Bell X-1E)
Data from The X-Planes: X-1 to X-45
- Crew: one
- Length: 31 ft (9.4488 m)
- Wingspan: 22 ft 10 in (6.9596 m)
- Height: 10 ft 10 in (3.3 m)
- Wing area: 115 ft² (10.684 m²)
- Empty weight: 6,850 lb (3,107.107 kg)
- Loaded weight: 14,750 lb (6,690.487 kg)
- Powerplant: one × Reaction Motors RMI LR-8-RM-5 rocket, 6,000 lbf (26.7 kN) each
- Maximum speed: 1,450 mph (Mach 2.24) (2,333.548 km/h)
- Range: 4 minutes 45 seconds (powered endurance)
- Service ceiling: 90,000+ ft (27,432+ m)
- Aircraft of comparable role, configuration and era
- Related lists
- List of experimental aircraft
- List of rocket planes
- List of X-1 flights
- List of X-1A flights
- List of X-1B flights
- List of X-1D flights
- List of X-1E flights
- Hallion, Richard, P. "The NACA, NASA, and the Supersonic-Hypersonic Frontier." NASA. Retrieved: 7 September 2011.
- Miller 2001, p. 15.
- Yeager et al., 1997, p. 14.
- The Miles M.52: Gateway to Supersonic Flight, Brown 2012, p. 87.
- Wings On My Sleeve, Brown 2008, p. 212
- Wood 1975, p. 36.
- 'The X-Planes: X-1 to X-45', Miller, Jay 2001
- Miller p. 23
- Anderson, Clarence E. "Bud". "Initial Glide Flights." cebudanderson.com. Retrieved: 14 October 2009.
- Yeager and Janos 1986, p. 96.
- Wolfe 1979, pp. 52–53.
- Anderson, Clarence E. "Bud". "A Turning Point." cebudanderson.com. Retrieved: 14 October 2009.
- Powers, Sheryll Goeccke. "Women in Flight Research at NASA Dryden Flight Research Center from 1946 to 1995," Monographs in Aerospace History, Number 6, 1997, NASA Headquarters, Washington, D. C.
- Miller 2001, pp. 21–35.
- Young, Dr. Jim. "Major Chuck Yeager's Flight to Mach 2.44 In the X-1A." AFFTC History Office, Edwards AFB. Retrieved: 14 October 2009.
- Martin, Douglas |title=Arthur Murray. "Test Pilot, Is Dead at 92." The New York Times, 4 August 2011. Retrieved: 6 August 2011.
- Thompson, Lance. "The X-Hunters." Air & Space, February/March 1995, ISSN 0886-2257. Retrieved: 12 March 2008.
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- "Photo number E-24911: X-1A in flight with flight data superimposed." NASA Dryden. Retrieved: 14 October 2009.
- "Fact Sheet X-1." NASA Dryden Fact Sheet. Retrieved: 12 March 2008.
- "Photo X-1A # E-24911." NASA, Dryden Collections. Retrieved: 14 October 2009.
- "Goleta Air & Space Museum." air-and-space.com, Edwards Air Force Base. Retrieved: 14 October 2009.
- "Fact Sheet X-1E." NASA, Dryden Collections. Retrieved: 12 December 2010.
- "Breaking the Sound Barrier." Modern Marvels (TV program). 2003.
- Hallion, Dr. Richard P. "Saga of the Rocket Ships." AirEnthusiast Five, November 1977-February 1978. Bromley, Kent, UK: Pilot Press Ltd., 1977.
- Miller, Jay. The X-Planes: X-1 to X-45. Hinckley, UK: Midland, 2001. ISBN 1-85780-109-1.
- Pisano, Dominick A., R. Robert van der Linden and Frank H. Winter. Chuck Yeager and the Bell X-1: Breaking the Sound Barrier. Washington, D.C.: Smithsonian National Air and Space Museum (in association with Abrams, New York), 2006. ISBN 0-8109-5535-0.
- Winchester, Jim. "Bell X-1." Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft (The Aviation Factfile). Kent, UK: Grange Books plc, 2005. ISBN 978-1-59223-480-6.
- Wolfe. Tom. The Right Stuff. New York: Farrar, Straus and Giroux, 1979. ISBN 0-374-25033-2.
- Yeager, Chuck, Bob Cardenas, Bob Hoover, Jack Russell and James Young. The Quest for Mach One: A First-Person Account of Breaking the Sound Barrier. New York: Penguin Studio, 1997. ISBN 0-670-87460-4.
- Yeager, Chuck and Leo Janos. Yeager: An Autobiography. New York: Bantam, 1986. ISBN 0-553-25674-2.
|Wikimedia Commons has media related to Bell X-1.|
- Bell X-1 Milestones of Flight
- NASA's History of the X-1
- Goodlin's NASA biography
- American X-Vehicles: An Inventory X-1 to X-50, SP-2000-4531 - June 2003; NASA online PDF Monograph
- Photo of Glamorous Glennis on display at the National Air and Space Museum in Washington, DC.
- Yeager's personal website
- Modeller's Guide to Bell X-1 Experimental Aircraft Part one
- Modeller's Guide to Bell X-1 Experimental Aircraft Part two
- "X-1 is Carried Aloft; Cockpit of the Bell X-1." Popular Science, August 1948, p. 97.