The North American XB-70 Valkyrie, a Cold War-era bomber, was a technological marvel designed to fly at Mach 3 and at 70,000 feet, circumventing Soviet air defenses through speed and altitude.
Initially conceived as a replacement for the B-52, the Valkyrie boasted sharp angular design features, including six afterburning engines and a shockwave-riding airframe.
In this view the #1 XB-70A (62-0001) is in a level cruise flight mode at a relative high altitude judging from the darkness of the sky. The XB-70A, capable of flying three times the speed of sound, was the world’s largest experimental aircraft in the 1960s. Two XB-70A aircraft were built. Ship #1 was flown by the NASA Flight Research Center (now NASA Dryden), Edwards, California, in a high speed research program.
The Air Force began the XB-70 bomber program in 1955, requiring a Mach 3 bomber that could fly at 70,000 feet. In September 1957, the Air Force issued a new set of requirements that called for a bomber with a cruising speed of Mach 3.0 to 3.2, an over-target altitude of 70,000 to 75,000 feet, a range of up to 10,500 miles, and a gross weight not to exceed 490,000 pounds.
However, by the early 1960s, new Surface-to-Air Missiles (SAMs) threatened the survivability of high-speed, high-altitude bombers. Less costly, nuclear-armed ICBMs (Intercontinental Ballistic Missiles) were also entering service. As a result, in 1961, the expensive B-70 bomber program was canceled in favor of the ICBMs.
The XB-70 Had Fuel Tanks The Size of a Bomber
The XB-70 was initially designed to operate under the “brute force concept,” which called for carrying massive fuel for a long-duration subsonic flight into Soviet territory and an aerodynamic design optimized for high performance during a relatively “short” sprint through enemy airspace.
This approach led to the concept that leveraged external fuel tanks that could be jettisoned once depleted. These “tip tanks” may have been disposable, but they were neither small nor cheap.
As a 1960 Congressional report pointed out, each 191,000-pound tip-tank was approximately the same size as America’s existing B-47 Stratojet long-range nuclear bomber.
General Curtis LeMay, a legend of World War II’s European and Pacific air campaigns, was not impressed.
“This isn’t an airplane,” LeMay reportedly said, “this is a three-ship formation.”
The XB-70 Takes Shape
North American Aviation engineers went back to redesigning the aircraft. They used a document, “Aircraft Configurations Developing High Lift-drag Ratios at High Supersonic Speeds,” to explain that aircraft designed from nose to tail for a single flight condition could dramatically outperform those designed to compromise between high- and low-speed flight.
Engineers at North American Aviation used a principle called ‘ compression lift ‘ to build a bomber that could fly at Mach 3 for 7,500 miles. This concept was initially researched by the National Advisory Committee for Aeronautics (NACA, now NASA).
Compression lift occurs when a conical body underneath the center of a wing pushes the air to the sides, increasing pressure under the wing section and thus dramatically increasing lift. This design eliminates the need for a large wing, which creates considerable drag.
The XB-70 was designed to use the compression lift principle by riding its shock wave generated by supersonic flight. The lift thus created a wave much like a surfer riding a wave. The conical body underneath the wing’s center became a giant pod, slightly triangular when viewed from the bottom, which held six engines, a bomb bay, and landing gear.
The Valkyrie was powered by six General Electric J93-GE 3 turbojet engines, each delivering around 30,000 lb of thrust in the afterburner. Because of the installation design, an engine could be removed and replaced in only a few hours.
The engines were mounted side by side at the rear of the underwing pod. Two large rectangular inlet ducts provided two-dimensional airflow. A series of variable ramps inside the intakes, the Air Induction Control System (AICS), would expand and contract to manipulate airflow to the engines and protect them from the powerful shock of supersonic air.
The system detected small changes in pressure during flight and reduced supersonic air to subsonic speeds at the engine faces.
The XB-70 was operated by a four-man crew comprised of a pilot (and aircraft commander), co-pilot, bomb and navigation officer, and defensive systems officer.
The cabin was designed to provide each crew member with an “encapsulated ejection seat” that would enclose them to provide pressurized oxygen for the descent from 70,000 feet. This feature had already been designed for the B-58.
The Valkyrie’s large delta-wing was paired with forward canards, also known as horizontal stabilizers. These provided lift ahead of the aircraft’s center of gravity, allowed for better trim control, and reduced trim drag at high supersonic speeds.
The canards themselves had flaps, coupled with using the aircraft’s elevons as flaps. The large delta wing allowed for lower speeds on takeoff and landing than would otherwise be possible with such a design.
The outer wing panels were hinged to allow for improved subsonic and supersonic flight. The panels were flat during takeoff and low-speed flight, effectively extending the wing surface and improving the aircraft’s lift-to-drag ratio.
Once the Valkyrie reached supersonic speeds, the wingtips would angle down to reduce the wing area behind the bomber’s center of gravity (reducing trim drag) and increase directional stability at high speeds.
The Valkyrie Was Cited as the Answer to the B-52s’ Obsolescence
In early 1960, then-Senators John F. Kennedy and Lyndon Johnson made public statements in favor of the Valkyrie program before winning the 1960 Presidential election over Richard Nixon.
In a humorous quip, Johnson cited the B-52’s “obsolescence” as a reason for continuing the Valkyrie program. Now, some 65 years later, the B-52’s service life shows no end in sight for some time still.
But a year later, the Kennedy-Johnson administration axed the XB-70 program. The aircraft was to be used for testing purposes at NASA.
However, during a photoshoot opportunity, disaster struck. The Valkyrie was piloted by Al white and Maj. Carl S. Cross.
An F-104N, flown by Joe Walker, began to move in close to the XB-70’s right wingtip, too close for safety. The Valkyrie’s angled-down wingtips generated strong vortices, and these caught the F-104N and flipped it over onto the Valkyrie’s back.
Image: Screenshot from video embedded below.
North American XB-70 pasted into a generic cloudscape.
The upside-down Starfighter smashed across the Valkyrie’s tail surfaces, tearing most of them away and damaging the left wing. Joe Walker was killed instantly upon impact, and his F-104N fell to the floor of the Mojave Desert in a ball of flames.
For 16 seconds, the Valkyrie continued in straight and level flight but then went into two slow rolls and broke into an unrecoverable flat spin. White managed to eject, but Cross was killed when the aircraft hit the ground in an upright and level configuration. White received serious injuries during ejection but later returned to flight status. He never flew the remaining XB-70 again.
The remaining Valkyrie flew to Wright-Patterson Air Force Base in Ohio, where it was displayed at the Air Force Museum. It resides there today.
About the Author:
Steve Balestrieri is a 19FortyFive National Security Columnist. He served as a US Army Special Forces NCO and Warrant Officer. In addition to writing for 19FortyFive, he covers the NFL for PatsFans.com and is a member of the Pro Football Writers of America (PFWA). His work was regularly featured in many military publications.
