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The 'Bell X-1', originally designated 'XS-1', was a joint NACA-U.S. Army Air Forces/US Air Force supersonic research project and the first aircraft to exceed the speed of sound in controlled, level flight. It was the first of the so-called X-planes, an American series of experimental aircraft designated for testing of new technologies and usually kept highly secret.

Contents

Design and development

XS-1

Operational history

Legacy

Variants

X-1A

X-1B

X-1C

X-1D

X-1E

Survivors

Specification (Bell X-1)

Specification (Bell X-1E)

References

External links

Related content

Design and development

XS-1

On 16 March 1945 the United States Army Air Forces' Flight Test Division and the National Advisory Committee for Aeronautics (NACA) (now NASA) contracted Bell Aircraft to build three XS-1 (for "Experimental, Supersonic", later X-1) aircraft to obtain flight data on conditions in the transonic speed range.^[1] The XS-1 was the first high-speed aircraft built purely for aviation research purposes and was never intended for production.
The X-1 was in principle a "bullet with wings" that closely resembled the shape of the Browning .50-caliber machine gun bullet that was known to be stable in supersonic flight^[2]. The aircraft also featured an all-moving tailplane that allowed it to pass through the sound barrier safely. The pattern shape was followed to the point of removing a canopy. Instead, the pilot sat behind a sloped, framed window inside a confined cockpit in the nose. To modern eyes, the X-1 has a markedly stubby look, but in 1947 the diminutive airframe represented state-of-the-art in streamlining. It was only 31 feet long with a 28-foot wingspan.

Operational history

Bell Aircraft Chief Test Pilot, Jack Woolams became the first to fly the XS-1, in a glide flight over Pinecastle Army Airfield, in Florida, on 25 January, 1946. Woolams would complete nine additional glide flights over Pinecastle before March 1946, when the #1 aircraft was returned to Bell for modifications in anticipation of the powered flight tests, planned for Muroc Army Air Field (now Edwards Air Force Base) in California.^[3] Following Woolams' death on 30 August, 1946, Chalmers "Slick" Goodlin was the primary Bell Aircraft test pilot of X-1-1. He made 26 successful flights in both of the X-1 aircraft from September 1946 until June 1947.
The Army Air Force was unhappy with the cautious pace of flight envelope expansion and Bell Aircraft's flight test contract for aircraft #46-062 was terminated and was taken over by the Army Air Force Flight Test Division on 24 June after months of negotiation. Goodlin had demanded a $150,000 bonus for breaking the sound barrier.^[4][5][6] Flight tests of the X-1-2 (serial number 46-063) would be conducted by NACA to provide design data for later production high-performance aircraft.
On 14 October 1947, just under a month after the United States Air Force had been created as a separate service, the tests culminated in the first manned supersonic flight, piloted by Air Force Captain Charles "Chuck" Yeager in aircraft #46-062, which he had christened ‘''Glamorous Glennis''’, after his wife. The rocket-powered aircraft was launched from the belly of a specially modified B-29 and glided to a landing on a runway. XS-1 flight number 50 is the first one where the X-1 recorded supersonic flight, at Mach 1.06 peak speed; however, Yeager and many other personnel record the possibility that Flight #49 (also with Yeager piloting), which reached a top recorded speed of Mach 0.997, may have in fact passed the Sound Barrier. (The measurements were not accurate to three significant figures and no sonic boom was recorded for that flight.)
As a result of the X-1's initial supersonic flight, the National Aviation Association voted its 1948 Collier Trophy to be shared by the three main participants in 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 of NACA for the NACA contributions.

Legacy

The research techniques used in the X-1 program became the pattern for all subsequent X-craft projects. The NACA X-1 procedures and personnel also helped lay the foundation of America's space program in the 1960s. The X-1 project defined and solidified the post-war cooperative union between U.S. military needs, industrial capabilities, and research facilities. The flight data collected by the NACA in the X-1 tests then provided a basis for American aviation supremacy in the latter half of the 20th century.
The intentions of the X-1 experiments were not to exceed the speed of sound in and of itself, but to determine and then demonstrate that controlled, sustained flight was possible at supersonic speeds.

Variants

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 him from dying that day; later Mel Apt would die testing the Bell X-2 under similar circumstances.

X-1A

Ordered by the Air Force on 2 April, 1948, the 'X-1A' (serial 48-1384) was intended to investigate aerodynamic phenomena at speeds above Mach 2 and altitudes greater than 90,000 feet, specifically focusing on 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 Ziegler. The aircraft was transferred to NACA in September 1954. Following modifications, including the installation of an ejection seat, the aircraft was lost on 8 August 1955 while being prepared for launch from the RB-50 mothership.^[1]

X-1B

The X-1B was equipped with aerodynamic heating instrumentation for thermal research (over 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 US Air Force starting from October 1954 prior to being turned over to the NACA in 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 and achieved a maximum speed of Mach 2.44. 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 X-15. The X-1B is now on display at the National Museum of the United States Air Force, Wright-Patterson Air Force Base, Dayton, Ohio.

X-1C

The X-1C was intended to test armaments and munitions in the high transonic and supersonic flight regimes. It was canceled while still in the mock-up stage, as the birth 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 platform.^[8]

X-1D

Aircraft number #48-1386 was the first of the second generation of supersonic rocket planes. Flown from EB-50 Superfortress A, number #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 was also some minor changes to the avionics set.
On 24 July, with Bell company test pilot Jean 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 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. The X-1D was lost in a fuel explosion during preparations for the first powered flight.

X-1E

The 'X-1E' resulted from a significant reconstruction of the X-1-2 (s/n 46-063) in order to pursue the goals originally set out for the X-1D and X-1-3, both lost in explosions in 1951.

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.).^[9]

★ A re-profiled super-thin wing (3⅜ 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 facilitated 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.^[9]
The X-1E first flew on 15 December, 1955, a glide flight under the controls of USAF test-pilot Joe Walker. Walker left the X-1E program in 1958, after 21 flights, attaining a maximum speed of Mach 2.21. NACA research pilot John B. McKay took his place in September 1958, completing five flights in pursuit of Mach 3 before the X-1E was permanently grounded following its 26th overall flight, in November 1958, due to the discovery of structural cracks in the fuel tank wall.

Survivors

Aircraft #46-062 is currently on display in the Milestones of Flight gallery of the National Air and Space Museum in Washington, DC, alongside the Spirit of St. Louis and SpaceShipOne. Aircraft #46-063, now the X-1E, is on display in front of the NASA Dryden Flight Research Center headquarters building. Aircraft #46-064 was destroyed 9 November 1951, in a ground fire following a captive flight test, after completing only a single glide flight (20 July, 1951^[1]).

Specification (Bell X-1)

Specification (Bell X-1E)

References

1. Miller 2001
2. Yeager et al 1997, p. 14.
3. http://www.cebudanderson.com/initialglideflights.htm
4. Yeager, Chuck and Janos, Leo. ''Yeager: An Autobiography''. New York: Bantam Books, 1986, p. 121. ISBN 0-553-25674-2.
5. Wolfe, Tom. ''The Right Stuff''. New York: Farrar-Straus-Giroux, 1979, p. 52-53. ISBN 0-374-25033-2.
6. A Turning Point
7. Miller 2001
8. http://www1.dfrc.nasa.gov/gallery/photo/X-1A/HTML/E-24911.html
9. http://www.nasa.gov/centers/dryden/news/FactSheets/FS-083-DFRC.html
10. http://www.nasa.gov/centers/dryden/news/FactSheets/FS-083-DFRC.html
11. Miller 2001

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★ "Breaking the Sound Barrier." ''Modern Marvels (TV program)''. 2003.

★ Miles Ahead of their Time

★ Miller, Jay. ''The X-Planes: X-1 to X-45,'' Hinckley, UK: Midland, 2001. ISBN 1-85780-109-1.

★ Pisano, Dominick A., van der Linden, R., Robert and Winter, Frank H. ''Chuck Yeager and the Bell X-1: Breaking the Sound Barrier''. Washington, DC: 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 1-84013-309-2.

★ Yeager, Chuck, Cardenas, Bob, Hoover, Bob, Russell, Jack and Young, James. ''The Quest for Mach One: A First-Person Account of Breaking the Sound Barrier''. New York: Penguin Studio, 1997. ISBN 0-670-87460-4.

External links

★ 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

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