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.).
* 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.
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 (752 m/s, 2,704 km/h).. NACA research pilot John B. McKay took his place in 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 following its 26th overall flight, in November 1958, due to the discovery of structural cracks in the fuel tank wall.
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 on 20 July, 1951.