Bell X-2

https://en.wikipedia.org/wiki/Bell_X-2

The Bell X-2 (nicknamed "Starbuster") was an X-plane research aircraft built to
investigate flight characteristics in the Mach 2–3 range. The X-2 was a
rocket-powered, swept-wing research aircraft developed jointly in 1945 by Bell
Aircraft Corporation, the U.S. Air Force and the National Advisory Committee for
Aeronautics (NACA) to explore aerodynamic problems of supersonic flight and to
expand the speed and altitude regimes obtained with the earlier X-1 series of
research aircraft.

The Bell X-2 was developed to provide a vehicle for researching flight
characteristics in excess of the limits of the Bell X-1 and D-558 II, while
investigating aerodynamic heating problems in what was then called the "thermal
thicket".

The Bell X-2 had a prolonged development period due to the advances needed in
aerodynamic design, control systems, high-temperature resistant materials to be
used, and other technologies that had to be developed. Not only did the X-2 push
the envelope of manned flight to speeds, altitudes and temperatures beyond any
other aircraft at the time, it pioneered throttleable rocket motors in U.S.
aircraft (previously demonstrated on the Me 163B during World War II) and
digital flight simulation. The XLR25 rocket engine, built by Curtiss-Wright, was
based on the smoothly variable-thrust JATO engine built by Robert Goddard in
1942 for the Navy.

Role
Research aircraft

National origin
United States

Manufacturer
Bell Aircraft

First flight
18 November 1955 (first powered flight) 27 June 1952 (first drop glide)

Retired
27 September 1956

Primary users
United States Air Force
National Advisory Committee for Aeronautics

Number built
2

Following a drop launch from a modified B-50 bomber, Bell test pilot Jean "Skip"
Ziegler completed the first unpowered glide flight of an X-2 at Edwards Air
Force Base on 27 June 1952. Ziegler and aircraft #2 (46-675) were subsequently
lost on 12 May 1953, in an inflight explosion during a captive flight intended
to check the aircraft's liquid oxygen system. A B-50 crew member, Frank Wolko,
was also killed during the incident. The wreckage of the aircraft fell into Lake
Ontario and was not recovered.

Lt. Col. Frank K. "Pete" Everest completed the first powered flight in the #1
airplane (46-674) on 18 November 1955. By the time of his ninth and final flight
in late July 1956 the project was years behind schedule, but he had established
a new speed record of Mach 2.87 (1,900 mph, 3050 km/h). About this time, the
YF-104A was demonstrating speeds of M = 2.2 or 2.3 in a fighter configuration.
The X-2 was living up to its promise, but not without difficulties. At high
speeds, Everest reported its flight controls were only marginally effective.
High speed center of pressure shifts along with fin aeroelasticity were major
factors. Moreover, simulation and wind tunnel studies, combined with data from
his flights, suggested the airplane would encounter very severe stability
problems as it approached Mach 3.

A pair of less experienced but excellent pilots, Captains Iven C. Kincheloe and
Milburn G. "Mel" Apt, were assigned the job of further expanding the envelope
and, on 7 September 1956, Kincheloe became the first pilot ever to climb above
100,000 ft (30,500 m) as he flew the X-2 to a peak altitude of 126,200 ft
(38,466 m). Just 20 days later, on the morning of 27 September, Apt was launched
from the B-50 for his first flight in a rocket airplane. He had been instructed
to follow the "optimum maximum energy flight path" and to avoid any rapid
control movements beyond Mach 2.7. With nozzle extenders and a longer than
normal motor run, Apt flew an extraordinarily precise profile; he became the
first man to exceed Mach 3, reaching Mach 3.2 (2,094 mph, 3,370 km/h) at 65,500
ft (19,960 m).

The flight had been flawless to this point, but, for some reason, shortly after
attaining top speed, Apt attempted a banking turn while the aircraft was still
above Mach 3 (lagging instrumentation may have indicated he was flying at a
slower speed or perhaps he feared he was straying too far from the safety of his
landing site on Rogers Dry Lake). The X-2 tumbled violently out of control and
he found himself struggling with the same problem of "inertia coupling" which
had overtaken Chuck Yeager in the X-1A nearly three years before. Yeager,
although exposed to much higher vehicle inertial forces, as a result of
extensive experience flying the X-1 was very familiar with its character, and
was able to recover. Apt attempted to recover from a spin, but could not. He
fired the ejection capsule, which was itself only equipped with a relatively
small drogue parachute. Apt was probably disabled by the severe release forces.
As the capsule fell for several minutes to the desert floor, he did not exit so
that he could use his personal parachute before ground impact, and was killed.

While the X-2 had delivered valuable research data on high-speed aerodynamic
heat build-up and extreme high-altitude flight conditions (although it is
unclear how much, as the Lockheed X-7 and IM-99 were among the winged vehicles
operating at comparable or higher velocities in this era), this tragic event
terminated the program before the National Advisory Committee for Aeronautics
could commence detailed flight research with the aircraft. The search for
answers to many of the riddles of high-Mach flight had to be postponed until the
arrival three years later of the most advanced of all the experimental rocket
aircraft, the North American X-15.

Specifications

General characteristics
Crew: one, pilot
Length: 37 ft 10 in (11.5 m)
Wingspan: 32 ft 3 in (9.8 m)
Height: 11 ft 10 in (3.6 m)
Wing area: 260 ft² (24.2 m²)
Airfoil: 2S-50 bicon
Empty weight: 12,375 lb (5,600 kg)
Loaded weight: 24,910 lb (11,300 kg)
Max. takeoff weight: 24,910 lb (11,300 kg)
Powerplant: 1 × Curtiss-Wright XLR25 rocket engine, 15,000 lbf (67 kN)at sea
level

Performance
Maximum speed: Mach 3.196 (2,094 mph, 3,370 km/h)
Service ceiling: 126,200 ft (38,466 m)



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