page_title: Bell X-1
section_title: X-1E
hierarchical_section_title: Bell X-1 / Variants / X-1E
caption_attribution_description: English: NASA test pilot Joe Walker in pressure suit with X-1E.
context_page_description: The Bell X-1 is a rocket engine–powered aircraft, designated originally as the XS-1, and was a joint National Advisory Committee for Aeronautics–U.S. Army Air Forces–U.S. Air Force supersonic research project built by Bell Aircraft. Conceived during 1944 and designed and built in 1945, it achieved a speed of nearly 1,000 miles per hour in 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 in 1954. The X-1, piloted by Chuck Yeager, was the first manned airplane to exceed the speed of sound in level flight and was the first of the X-planes, a series of American experimental rocket planes designed for testing new technologies.
context_section_description: (Bell Model 44)
  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 (⅜ 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.
caption: The X-1E, christened Little Joe, with pilot Joe Walker.
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