XB-70 Valkyrie

In my opinion, this is one of the most interesting-looking bombers to ever fly, the XB-70 Valkyrie, designed by North American Aviation. It was intended to be a supersonic, nuclear- armed, deep penetration bomber. It was designed way back when military planners thought that the B-52 would be retired by the late 1960s. (They were way wrong and the common belief is that the last pilot of the B-52 has not yet been born.)

The Valkyrie was designed to fly at or above 70,000 feet and at speeds up to Mach 3 to avoid being targeted by interceptor fight aircraft, the only effective way of defending against high altitude bombers at the time of the XB-70's design. Only two were ever built and the program was canceled in 1961 when it became apparent that the new surface to air missiles made high altitude attack untenable. This was most evident when the U-2 "Dragon Lady" piloted by Francis Gary Powers was shot down over the Soviet Union in 1960 by a volley of SA-2 Guideline missiles. The Valkyrie was later used for high speed and altitude testing, and some of their technology resurfaced in the B-1 Lancer and SR-71 Blackbird.

3 views of the XB-70

The Valkyrie was an advanced design, making use of honeycombed steel and titanium to combat the high temperatures that the airframe reached at supersonic speeds. The XB-70 was built around a large delta wing, common in designs of the time, and used supersonic technologies from the Mach 3 Navajo. One of its most interesting features is the use of compression lift. This created a shock wave below the aircraft that would increase the lift of the wing by 5%, giving the Valkyrie greater ceiling, range, and efficiency. The compression lift was generated by a wedge on the engine inlets. The design of the Valkyrie was different from almost every other aircraft in its time, in that the outer sections of the wing was hinged so that it could be pivoted down up to 65 degrees. The effect was to increase the directional stability of the the XB-70 when it was traveling at supersonic speeds and strengthen the effect of the compression lift. When the wingtips were pointed down, more of the shock wave would be trapped under the wings, increasing the lift.

General characteristics

Data from USAF XB-70 Fact sheet

• Crew: 2
• Length: 185 ft 10 in
  
• Wingspan: 105 ft 0 in
  
• Height: 30 ft 9 in
• Wing area: 6,296 ft²
  
• Airfoil: Hexagonal; 0.30 Hex modified root, 0.70 Hex modified tip
• Empty weight: 210,000 lb
  
• Loaded weight: 534,700 lb
  
• Max takeoff weight: 550,000 lb
  
• Powerplant: 6× General Electric YJ93-GE-3 afterburning turbojet
  • Dry thrust: 19,900 lbf each
  • Thrust with afterburner: 28,800 lbf each

Performance

• 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: 3,725 nmi (4,288 mi, 6,900 km) combat
• Service ceiling: 77,350 ft (23,600 m)
• Wing loading: 84.93 lb/ft² (414.7 kg/m²)
• lift-to-drag: about 6 at Mach 2
• Thrust/weight: 0.314

Early designs featured wing tip fuel tanks that could be jettisoned with the wing tips

Sadly, one of the XB-70s was lost in a terrible collision between the Valkyrie and a F-104 Starfighter in 1966. The F-104 pilot and the co-pilot of the XB-70 were killed and the pilot of the Valkyrie severely injured by the clamshell escape pod that closed on his left arm as he ejected.

XB-70 Valkyrie seconds after impact with a F-104 Starfighter