North American XB-70 Valkyrie

North American XB-70 Valkyrie
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Name	XB-70 Valkyrie
Caption	The second XB-70A (62-0207) in flight
Type	Strategic bomber, Supersonic research aircraft
National origin	United States
Manufacturer	North American Aviation
Designer	Harrison Storms
First flight	21 September 1964
Introduced	Never entered service
Retired	4 February 1969
Status	Retired
Primary user	United States Air Force
Program cost	$1.5 billion (entire program)
Unit cost	$750 million (average per aircraft, 1964)

North American XB-70 Valkyrie was a supersonic strategic bomber prototype developed for the United States Air Force in the late 1950s and early 1960s. Designed by North American Aviation under the leadership of Harrison Storms, it was intended to fly at Mach 3 at high altitude to evade interceptor aircraft and surface-to-air missiles. The program was ultimately canceled due to shifting defense priorities, the rising threat of Soviet anti-aircraft warfare systems, and the high cost of the project, but the two completed aircraft provided invaluable data for future supersonic transport and military aircraft design.

Development and design

The Valkyrie's origins trace to Cold War requirements for a high-altitude nuclear-capable bomber to replace the B-52 Stratofortress. The initial Weapons System 110A study evolved into a North American Aviation proposal featuring a large delta wing, six powerful General Electric YJ93 turbojet engines, and extensive use of stainless steel honeycomb and titanium to withstand kinetic heating at Mach 3. A key innovation was its variable-geometry wingtips, which could be folded down in flight to enhance directional stability through compression lift. The aircraft's design was heavily influenced by earlier research from the National Advisory Committee for Aeronautics and its successor, NASA. The program faced significant challenges, including immense technical complexity and escalating costs, which were scrutinized by officials like Robert McNamara at the United States Department of Defense.

Operational history

Only two flyable prototypes, designated XB-70A, were constructed (serial numbers 62-0001 and 62-0207). The first flight occurred on 21 September 1964 from Air Force Plant 42 in Palmdale, California, piloted by Alvin White and Joseph Cotton. Flight testing revealed handling challenges and confirmed the immense engineering achievement of sustained Mach 3 flight. The second prototype, incorporating design improvements, first flew on 17 July 1965. The program suffered a catastrophic setback on 8 June 1966 when aircraft 62-0207 was destroyed following a mid-air collision with a NASA F-104 Starfighter piloted by Joe Walker during a General Electric publicity photo flight near Barstow, California; Walker and Carl Cross were killed, while Alvin White ejected and survived. The remaining Valkyrie continued research flights for NASA until its final flight on 4 February 1969.

Specifications (XB-70A)

* **Crew:** 2 * **Length:** 185 ft 10 in (56.6 m) * **Wingspan:** 105 ft 0 in (32.0 m) * **Height:** 30 ft 9 in (9.4 m) * **Empty weight:** 253,600 lb (115,030 kg) * **Gross weight:** 534,700 lb (242,500 kg) * **Powerplant:** 6 × General Electric YJ93-GE-3 turbojet engines, 19,900 lbf (88 kN) thrust each dry, 28,800 lbf (128 kN) with afterburner * **Maximum speed:** Mach 3.1 (2,056 mph, 3,309 km/h) at 73,000 ft (22,250 m) * **Range:** 3,725 nmi (4,288 mi, 6,900 km) * **Service ceiling:** 77,350 ft (23,575 m)

Cancellation and legacy

The Valkyrie program was formally canceled in 1961, though funding continued for research aircraft. The rise of effective Soviet surface-to-air missiles like the S-75 Dvina made high-altitude penetration increasingly risky, shifting USAF strategy to low-level flight, exemplified by the B-1 Lancer. Furthermore, the growing capability and lower cost of intercontinental ballistic missiles, such as those deployed by Strategic Air Command, reduced the need for a manned bomber. Despite its cancellation, the XB-70 provided critical data on supersonic flight, aerodynamics, structural heating, and sonic boom effects, directly influencing the design of the American SST program and later military aircraft like the SR-71 Blackbird.

Aircraft on display

The sole surviving XB-70A, aircraft 62-0001, is preserved and on public display. It is housed at the National Museum of the United States Air Force at Wright-Patterson Air Force Base near Dayton, Ohio. The aircraft was flown to the museum in February 1969 and has been a centerpiece of its research and development gallery for decades, representing the ambitious technological frontiers of Cold War aviation.

Category:United States bomber aircraft 1950–1959 Category:Cancelled military aircraft projects of the United States Category:Delta-wing aircraft Category:Six-engined jet aircraft Category:North American Aviation aircraft