Bell X-2 Starbuster
A swept-wing, rocket-powered research aircraft built by Bell Aircraft Corporation for the U.S. Air Force and the NACA, designed to explore aerodynamic heating and stability and control beyond the X-1's regime. Its two airframes flew from 1952 to 1956: one was destroyed by an explosion over Lake Ontario in 1953, and the other reached 126,200 feet and then Mach 3.196 in September 1956, before inertial coupling destroyed it on that final flight and killed its pilot.
Why It Mattered
The X-2 was a joint programme of the U.S. Air Force, the National Advisory Committee for Aeronautics (NACA) and Bell Aircraft Corporation, begun in 1945 to extend research flying beyond the speed and altitude regime of the X-1 series. Its subject was the region near Mach 3: the structural effects of aerodynamic heating, and stability and control at high speeds and altitudes. NASA records the X-2 as the first aircraft to reach Mach 3, and the first to fly higher than 100,000 feet. Both marks were set in September 1956, the programme's last month; the altitude mark came twenty days before the flight that destroyed the aircraft. What the programme produced was data: NASA credits it with measurements of aerodynamic heating, and of stability and control effectiveness at high speed and altitude.
Design Notes
"Starbuster" was the nickname of the two X-2 airframes Bell built at its Wheatfield, New York plant. The airframe was built of stainless steel and K-monel, a copper-nickel alloy. Power was a two-chamber Curtiss-Wright XLR25 rocket engine, throttleable between 2,500 and 15,000 pounds of thrust and burning liquid fuel. A modified Boeing B-50 carried the X-2 to its launch altitude, around 30,000 feet; the pilot dropped away, lit the engine on powered flights, and after burnout glided to an unpowered landing on Rogers Dry Lake at Edwards Air Force Base. For escape, the entire nose formed a capsule that would jettison and deploy a stabilizing parachute, after which the pilot was to open the canopy and bail out manually; NACA representatives were concerned the system might prove dangerous to use.
Operational History
Bell test pilot Jean "Skip" Ziegler made the X-2's first flight on 27 June 1952, an unpowered glide after release from the B-50 at Edwards. That airframe was lost on 12 May 1953, in an explosion during a captive flight over Lake Ontario to check the liquid-oxygen system; Ziegler and B-50 crew member Frank Wolko were killed, and the aircraft fell into the lake and was not recovered. The surviving airframe was released for a glide flight at Edwards on 5 August 1954, and on 18 November 1955 Lt. Col. Frank "Pete" Everest made the first powered flight, lighting only the 5,000-pound-thrust chamber and reaching Mach 0.95. In 1956 Everest worked up to Mach 2.87 at 68,000 feet, on a flight that NASA says earned him the title "Fastest Man Alive." Capt. Iven C. Kincheloe then flew the altitude programme, reaching 126,200 feet on 7 September 1956. The Air Force was due to hand the X-2 over to the NACA in mid-September, but asked for an extension so that another pilot, Capt. Milburn G. "Mel" Apt, could be checked out. On 27 September 1956 Apt flew faster than Mach 3, the first person to do so, reaching 2,094 mph (Mach 3.196). Turning back toward Edwards, he met the control divergence called inertial coupling and the aircraft tumbled; Apt jettisoned the escape capsule but could not extract himself before it struck the ground, and was killed.
Afterlife
The fatal flight ended the programme before the NACA could begin the detailed flight research it had planned for the aircraft. Neither airframe survives: one lies unrecovered in Lake Ontario, and the other came down in the desert in three pieces and was scrapped, after a proposal to salvage and modify it for a hypersonic test programme was not approved. Kincheloe's altitude record stood until the X-15 programme. The X-2's legacy is its research: NASA credits the type with data on aerodynamic heating, and on stability and control effectiveness at the speeds and altitudes it reached.