XB-70 Valkyrie
| XB-70 Valkyrie |
|---|
|
| Description |
|---|
| Role | Bomber prototype |
| Crew | |
| Dimensions |
|---|
| Length | 185 ft 10 in | 56.6 m |
| (with boom) | 192 ft 2 in | 58.6 m |
| Wingspan | 105 ft | 32 m |
| Height | 30 ft 9 in | 9.4 m |
| Wing area | | |
| Weights |
|---|
| Empty | | |
| Loaded | 534,700 lb | 243 t |
| Maximum take-off | | |
| Powerplant |
|---|
| Engines | 6 GE YJ-93 |
| Power | | |
| Performance |
|---|
| Maximum speed | 2,056 mi/h at 73,000 ft | 3300 km/h at 22250 m |
| Operating range | 4,288 mi | 7900 km |
| Service ceiling | 77,350 ft | 23600 m |
| Rate of climb | | |
| Armament |
|---|
| N/A |
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The North American XB-70 "Valkyrie" was conceived for the Strategic Air Command in the 1950s as a high-altitude bomber that could fly three times the speed of sound (Mach 3). The Valkyrie was configured as a canard delta wing, built largely of stainless steel honeycomb sandwich panels and titanium. It was designed to make use of a phenomenon called "compression lift," achieved when the shock wave generated by the airplane flying at supersonic speeds supports part of the airplane's weight. For improved stability at supersonic speeds, the Valkyrie could droop its wingtips as much as 65 degrees.
Drooping the wingtips also strengthened the compression lift effect -- With the wingtips drooped downwards, the shock waved caused by the compression wedge at the center of the wing would be further trapped under the wings, rather than simply flowing out past the end of the wings. Partially as a result of this, the XB-70 holds the record for the the highest lift-to-drag ratio on a manned aircraft, only later bested by the highly specialized D-21 drone.
Following the downing of the U-2 flown by Gary Powers, the viability of the XB-70 as a bomber was questioned, and the program was changed to a research program for the advanced study of aerodynamics, propulsion, and other subjects related to large supersonic aircraft. Initial plans were made to build 3 aircraft, each one incorporating modifications based on lessons learned from the previous aircraft's flight tests, but the program was cut down to two aircraft in July, 1964.
The first XB-70 made its maiden flight on September 21, 1964. The first aircraft would be found to suffer from weaknesses in the honeycomb construction, and was continually troubled by hydraulic leaks, fuel leaks, and problems with the aircraft's unusually complicated landing gear. In flight on May 7th, 1965, the divider separating the left and right halves of the engine inlet broke off and was ingested into the engines, damaging all six beyond repair. On October 14, 1965, on the first flight exceeding a speed of Mach 3, the stress again damaged the honeycomb construction, leaving two feet of the leading edge of the left wing missing. These construction problems resulted in the imposition of a speed limit of Mach 2.5 on the first aircraft.
These problems were almost completely solved on the second aircraft, which first flew on July 17, 1965. On May 19th, 1966, aircraft number two flew 2400 miles in a 91 minutes, attaining Mach 3 for 33 minutes of that flight. On June 8, 1966, however, it crashed following a mid-air collision with an F-104 that occurred while the aircraft were flying in close formation for a photo shoot. NASA Chief Test Pilot Joe Walker, piloting the F-104, and Carl Cross, copilot aboard the XB-70, were both killed in the crash, while Al White, the XB-70's pilot, successfully ejected.
The first aircraft and its limited abilities continued research, making 33 more research flights, On February 4, 1969, Valkyrie number one was retired and flown to the U.S. Air Force Museum in Dayton, Ohio.
The XB-70 caused so much concern in the Soviet Union that a special fighter aircraft design program was created to counter it. Though the XB-70 was cancelled, this program resulted in the MiG-25, still the fastest operational fighter aircraft in existence.
Specifications
- Span: 105 ft (32 m)
- Length: 185 ft 10 in (56.6 m) without boom; 192 ft 2 in (58.6 m) with boom
- Height: 30 ft 9 in (9.4 m)
- Weight: 534,700 lb (243 t) loaded
- Armament: None
- Engines: 6 GE YJ-93s developing 30,000 lb (133 kN) thrust each with afterburner.
Performance
- Maximum speed: 2,056 mph at 73,000 ft (3,300 km/h at 22,250 m) (Mach 3.1)
- Cruising speed: 2,000 mph at 72,000 ft (3,200 km/h at 22,000 m) (Mach 3.0)
- Range: 4,288 mi (7,900 km)
- Service Ceiling: 77,350 ft (23,600 m)
