File:United States Air Force - North American XB-70A Valkyrie bomber 35.jpg

English: (National Museum of the United States Air Force collection, Wright-Patterson Air Force Base, Dayton, Ohio, USA)

---

From exhibit signage:

NORTH AMERICAN XB-70 Valkyrie

The futuristic XB-70A was originally conceived in the 1950s as a high-altitude, nuclear strike bomber that could fly at Mach 3 (three times the speed of sound) - any potential enemy would have been unable to defend against such a bomber.

By the early 1960s, however, new surface-to-air missiles threatened the survivability of high-speed, high-altitude bombers. Less costly, nuclear-armed intercontinental ballistic missiles were also entering service. As a result, in 1961, the expensive B-70 bomber program was canceled before any Valkyries had been completed or flown.

Even so, the United States Air Force bought two XB-70As to test aerodynamics, propulsion, and other characteristics of large supersonic aircraft. The first XB-70A, on display here, flew in September 1964, and it achieved Mach 3 flight in October 1965. The second Valkyrie first flew in July 1965, but in June 1966, it was destroyed following an accidental mid-air collision. A third Valkyrie was not completed.

The first XB-70A airplane continued to fly and generate valuable test data in the research program until it came to the museum in 1969.

The Valkyrie's six large turbojet engines together provided an impressive 168,000 pounds of thrust.

The Valkyrie's airframe was built with advanced techniques and materials to reduce weight and to withstand high temperatures from aerodynamic heating at high speed.

The sleek Valkyrie took advantage of "compression lift", where the shock wave generated by the airframe at supersonic speed supports part of the airplane's weight. The XB-70A could also droop its wingtips as much as 65 degrees for additional stability at high speeds.

HIGHER AND FASTER: B-70 BOMBER CONCEPT

In the mid-1950s, the United States Air Force wanted a radically advanced new bomber that could fly much faster (Mach 3+ or 2,000 miles per hour) and higher (70,000+ feet) than the B-52 it would replace.

The revolutionary B-70 design promised to meet this demanding requirement. It would be expensive, however, and its survival could not be guaranteed against future Soviet defenses. In 1961 - before a prototype was built - the B-70 bomber program was canceled.

SUPERSONIC TEST VEHICLE: XB-70A

Although the bomber program was canceled, the United States Air Force ordered two XB-70As (AV-1 and AV-2) as pure test aircraft. Between 1964-1969, they carried out 129 flights, generating valuable data and knowledge regarding large supersonic aircraft.

The museum's XB-70A (AV-1) was the first one built and also the first Valkyrie to fly at Mach 3 (about 2,000 miles per hour). After this flight, however, it was limited to Mach 2.5 due to structural concerns.

The second XB-70A (AV-2) flew multiple times at Mach 3, including a sustained, 32-minute, Mach 3 flight in May 1966. Valkyrie AV-2 was lost in June 1966 afer an F-104 collided with it in mid-air. F-104 pilot Joe Walker (NASA) and XB-70A copilot Major Carl Cross (United States Air Force) died. North American pilot Al White ejected from the XB-70A, but was badly injured.

XB-70A TEST PILOTS

Seven pilots flew the Valkyrie: - Al White (North American Chief Test Pilot) - made the most XB-70A flights, 67, including piloting AV-1 on its Mach 3 flight in October 1965. - Colonel Joe Cotton (United States Air Force) - made 62 Valkyrie flights, including copiloting AV-1 on its Mach 3 flight in October 1965. - Lieutenant Colonal Fitzhugh "Fitz" Fulton (United States Air Force / NASA) - made 63 flights and had the most time (124 hours) in the XB-70A. - Van Shepard (North American) - Major Carl Cross (United States Air Force) - Don Mallick (NASA) - Lieutenant Colonel Emil "Ted" Sturmthal (United States Air Force)

NASA AND THE SUPERSONIC TRANSPORT PROGRAM

The United States government encouraged supersonic airliner progress with the National Supersonic Transport Program. NASA used XB-70A AV-1 as its primary aircraft to investigate supersonic transport operations.

In 1971, the American supersonic transport program was canceled, in part due to the problem of sonic booms on the ground. Sonic booms are loud, explosive noises caused by aircraft flying faster than the speed of sound.

Later in the 1970s, however, the supersonic British / French Concorde entered commercial service and the Soviet Union briefly operated the supersonic TU-144.

SOVIET RESPONSE: T-4 BOMBER AND MiG INTERCEPTOR

During the Cold War, development of new United States weapon systems prompted Soviet reactions, and vice-versa. In the case of the XB-70, the Soviet Union tested a supersonic bomber prototype, the T-4, and developed a new Mach 3 interceptor, the MiG-25.

First flown in 1972, the T-4 prototype only reached Mach 1.3 before it was canceled.

Ironically, the MiG-25 entered service in 1970, one year after the XB-70 was delivered to the museum.

TECHNICAL NOTES

ENGINES: Six General Electric YJ93S of 28,800 pounds of thrust each with afterburner

RANGE: 4,288 miles

SERVICE CEILING: 77,350 feet

LENGTH: 185 feet, 10 inches

HEIGHT: 30 feet, 9 inches

WEIGHT: 534,700 pounds loaded

---