Bell Aircraft Company was once again contracted by the National Advisory Committee for Aeronautics (NACA) and the United States Air Force (USAF) to provide a high-speed, rocket-powered research aircraft following their success with the Bell X-1 project of the late 1940s. This provided the impetus for the subsequent Bell X-2 to appear in the mid-1950s and continue the rigorous flight testing regime into the Mach 2 / Mach 3 speed range. The X-2 was essentially an evolved, more capable version of the X-1. A pair of X-2 aircraft were completed for the tests ahead and the product nicknamed "Starbuster".
To power the new aircraft the two-chamber, variable thrust Curtiss-Wright XLR-25 rocket engine of up to 15,000 lb output was installed and mated to throttle controls (controls which the X-1 lacked). Aerodynamic refinements were present about the sleeker, slimmer fuselage and a low-mounted, swept-wing mainplane assembly was used (unlike the straight wings of the X-1). The tail remained a single vertical fin with mid-mounted horizontal planes though all leading edges were also swept.
As with the X-1, the X-2 was an air-launched vehicle though this time a specially-modified Boeing B-50 Superfortress substituted for the original B-29 mothership. Also as in the X-1, the X-2 completed its first test flights solely under glide power with the first undertaken on June 27th, 1952 - landings aided by an integrated wheeled undercarriage arrangement. The first rocket-powered flight did not come until November 18th, 1955.
The X-2 became a record setter in its own right when it achieved a new speed record of Mach 2.87. It also became the first powered, manned aircraft to break the 100,000 foot altitude ceiling when it reached 126,200 feet on September 7th, 1956 (test pilot Iven Kincheloe at the controls). With some modifications added for Mach 3+ flight controlling, the X-2 then became the first aircraft to exceed Mach 3.0 on September 27th, 1956 (test pilot Milburn Apt). However, during this same flight, the aircraft experienced "inertia coupling" which spun the rocket plane out of control, killing Apt during his attempted ejection on May 12th, 1953.
Apt's death delayed further work involving the X-2 and the product was formally written off altogether in anticipation of the arrival of the more advanced North American X-15 rocket research aircraft arriving in the late part of the decade. Three of its kind would be built and the program would provide additional high speed data until its retirement in December of 1968.
As it stood, only the first X-2 prototype achieved any powered flights - 10 total - with seven glide flights to its name from the period of June 1952 to September 1956. The second prototype never completed its only powered flight and added three glide flights to its record before the end.
United States
