XB-70 Valkyrie

North American Aviation built two XB-70 Valkyrie as prototypes for the proposed B-70 Mach 3 nuclear long range bomber for evaluation by the USAF Strategic Air Command as a potential replacement for the long range Boeing B52 bomber and the supersonic Mach 2 Convair B-58 Hustler bomber.

Design started in the late 1950's and the first prototype flew in September 1964, five years later in 1969 the B-70 Valkyrie project was abandoned, the main Strategic nuclear deterrent platform had become ICBM's and and was clearly moving towards submarine launched missiles like Polaris, additionally advances in anti-aircraft missile design had resulted in the "fly high and fast" invulnerability idea becoming outdated as had already been proved by the shooting down of  Francis Gary Powers Lockheed U2 Spy-plane in May 1960 whilst over Soviet territory.

It is of note that following a photo-shoot on the 8th of June 1966 the second prototype Valkyrie tragically crashed after a collision with a F-104 Starfighter, it is thought that the F-104 Starfighter was rolled into the Valkyrie prototype by the wake vortex produced by the Valkyrie's wingtip.

North American XB-70A Valkyrie Specifications:

• Crew: Pilot and Co-Pilot
• Length: 185 ft 10 in (56.6 m)
• Wingspan: 105 ft 0 in (32 m)
• Height: 30 ft 9 in (9.4 m)
• Empty weight: 210,000 lb (93,000 kg)
• Loaded weight: 534,700 lb (242,500 kg)
• Max takeoff weight: 550,000 lb (250,000 kg)
• Engines: Six 28,800 lbf(128 kN) General Electric YJ93-GE-3 afterburning turbojets
  
• Maximum speed: Mach 3.1 (2,056 mph, 3,309 km/h)
• Cruise speed: Mach 3.0 (2,000 mph, 3,200 km/h)
• Range: 4,288 mi ( 6,900 km)
• Service ceiling: 77,350 ft (23,600 m)