The famous Bell X-1 was the first aircraft to break the sound barrier in level flight. Its development started in 1945, and it was inspired by the shape of a Browning .50-cal machine gun round. Indeed, the Bell X-1 was essentially a bullet with wings, propelled by a four-chamber rocket engine. The first supersonic test flight occurred on 14 October 1947. After two Bell X-1 craft were destroyed by separate explosions in 1951, X-1E (with serial number 46-063) was reconstructed from X-1-2. Major modifications specific to the X-1E were a turbopump fuel feed system, a super-thin wing and a “knife-edge” cockpit windscreen. The X-1E performed its maiden flight on 15 December 1955 with test pilot Joe Walker at the controls. By the time the craft completed its 26th and final flight it had attained a top speed of Mach 2.21, which equates to 2,704kmph!
