The XB-70 was the attempt at developing a supersonic, long-range bomber during the Cold War.
It was not long after World War II that the United States not only had “the bomb” and had used it – twice – but faced a new enemy, the Soviet Union.
A piston-powered aircraft like the B-29 was not suitable to deliver a first strike in Russia even though Superfortresses “Enola Gay” and “Bockscar” each dropped the first atomic bombs on Hiroshima and Nagasaki.
In the early 1950s, as the Cold War heated up, the U.S. looked for a jet-powered bomber that could fly from the continental U.S. to a strategic target in the Soviet Union and return without refueling.
At the time, the B-52 was not ideal because it was sub-sonic. The thinking was that a bomber delivering a nuclear weapon needed to be supersonic to escape the bomb blast. Plus, flying at Mach 3-plus and 70,000 feet it would be beyond the range of Soviet interceptors and anti-aircraft weapons.
Hence, the U.S. Air Force and Strategic Air Command started development of the B-70 – a deep-penetration strategic bomber that could deliver nuclear weapons.
The work to define and produce a single B-70 would drag on through the late 1950s. In fact, the design delays turned the B-70 obsolete before it could got past the drawing board. By the late 1950s, the Soviets had developed surface-to-air missiles as part of its air-defense system.
A super-sonic bomber flying at high altitude couldn’t escape missiles. Ironically, the B-52 turned out to be the best nuclear bomber of choice because it could fly low enough and remain below the missile radar line of site.
Plus, as the nuclear arms race developed, bomber-delivered nuclear weapons became just the third prong of the United States’ trident. By the late 1950s, ICBMs hidden in silos and nuclear submarines stalking below the oceans’ surface figured to be the primary striking weapons. The B-52s served as a fallback delivery system.
In 1961, after spending $800 million on the B-70 development, the project was cancelled. However, the work done to study long-duration, high-speed flight resulted in two XB-70A Valkyrie being built. Each featured a canard, delta wing and six General Electric YJ93-GE-3 turbojet engines. It was flown by two crew members.
Compression lift – keeping the shock wave attached along the leading edge prevented the high pressure from spilling up over the wing – generated five percent of the total lift while inboard camber enhanced the effect of the higher pressure behind the shock wave.
The outer sections of the wings were hinged, not in the horizontal like the F-14, but downward up to 65 degrees to increase directional stability when supersonic and trapping the compression lift under the wings.
As a supersonic test platform, the XB-70A would fly only five years from 1964 to 1969. One crashed in 1966 during a mid-air, multi-aircraft photo shoot.
The remaining Valkyrie is permanently housed at the United States Air Force Museum near Dayton, Ohio. Meanwhile, the venerable B-52 – which the B-70 was designed to replace – is still flying missions. In fact, B-52s recently went on station in Qatar to support the American-led campaign against the Islamic State group.