XB70 Valkyrie, Things You Might Now Know. The North American Supersonic Bomber That Never Was. A rare interview with General Fred Ascani, the person responsible for the XB70 program for the Air Force, and a look at the history of the Boeing SST 2707, the supersonic airliner that was also prematurely scrapped.
The North American Aviation XB70 Valkyrie was the prototype version of the planned B70 nucleararmed, deeppenetration supersonic strategic bomber for the United States Air Force Strategic Air Command. Designed in the late 1950s by North American Aviation (NAA), the sixengined Valkyrie was capable of cruising for thousands of miles at Mach 3+ while flying at 70,000 feet (21,000 m).

By the mid1950s, the United States had developed a stateoftheart, alljetpowered bomber force. The newly introduced Boeing B52 Stratofortesss could reach the Soviet Union from just about anywhere in the world. The soontobeintroduced supersonic Convair B58 Hustler could dash to supersonic speeds. Both aircraft were engineering marvels. But even so, they were expected to perform poorly over Soviet airspace. The B52 flew too slowly to stand a chance against the latest generation of Soviet interceptors, while the supersonic B58 lacked the required range and payload to be truly effective. The U.S. Air Force needed a nextgeneration bomber that would combine the capabilities of both these aircraft. A plane that could fly at supersonic speeds, travel long distances, and carry large payloads.

To meet their new bomber requirements, the Air Force contracted leading aerospace companies to explore radical new technologies, like nuclearpowered jet engines for extending aircraft range and highenergy ‘zipfuels’ to increase aircraft performance. Boeing and North American Aviation would play a vital role in research. But given the limitations of technology, the most practical solution put forward was the ‘dash concept’ which detailed an enormous aircraft that would travel subsonically most of the way to its target, before jettisoning outer portions of its wings and fuel tanks to make a supersonic dash. These concepts were studied in an era of extraordinary advances in aviation technology and engineering, and by 1957 it became apparent that it might be possible to build a large, longrange bomber that could fly supersonically over its entire mission.

In 1957, the Air Force outlined their specifications for an aircraft that would cruise at Mach 3, up to an altitude of 75,000 feet. It was expected to offer a similar payload and range to the B52. Boeing and North American Aviation both submitted design concepts, but North American’s proposal was selected for development. A key principle in North America’s design was compression lift, which would significantly improve the aircraft’s lifttodrag ratio when flying at high supersonic speeds. The new bomber would be designed as the B70 (XB70 in experimental prototype form) and named the Valkyrie.

General characteristics

Crew: 2
Length: 185 ft 0 in (56.39 m)
Wingspan: 105 ft 0 in (32.00 m)
Height: 30 ft 0 in (9.14 m)
Wing area: 6,297 sq ft (585.0 m2)
Airfoil: Hexagonal; 0.30 Hex modified root, 0.70 Hex modified tip
Empty weight: 253,600 lb (115,031 kg)
Gross weight: 534,700 lb (242,536 kg)
Max takeoff weight: 542,000 lb (245,847 kg)
Fuel capacity: 300,000 pounds (140,000 kg) / 46,745 US gal (38,923 imp gal; 176,950 L)
Powerplant: 6 × General Electric YJ93 afterburning turbojet, 19,900 lbf (89 kN) thrust each dry, 28,000 lbf (120 kN) with afterburner
Performance

Maximum speed: 1,787 kn (2,056 mph, 3,310 km/h)
Maximum speed: Mach 3.1
Cruise speed: 1,738 kn (2,000 mph, 3,219 km/h)
Combat range: 3,725 nmi (4,287 mi, 6,899 km)
Service ceiling: 77,350 ft (23,580 m)
Lifttodrag: about 6 at Mach 2
Wing loading: 84.93 lb/sq ft (414.7 kg/m2)
Thrust/weight: 0.314

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