What does a Mach 3 bomber tell you when he finds himself parked under museum lights other than on an alert ramp?
North American XB-70 Valkyrie was a brainchild of the late 1950s, a coat-of-arms solution to a barbarous dilemma of how to fly an aeroplane through a stacked defense and back. It was in paper easy and in metal hard–so high and so fast that it eluded interceptors. During testing, the plane demonstrated that the feasibility of the premise was technically possible. It may also travel at Mach 3 or higher and fly in the thinned air at an altitude of 70,000 to 80,000 feet with the help of six General Electric YJ93 turbo jets. It also created a data bank of high-speed flight information which survived beyond the program itself.
It was never that performance with “just engines.” The airplane of the Valkyrie was designed around the shockwave control such as foldable wingtips that folded down and touched the supersonic speed to assist the trapping pressure and enhance the lift. Its structure, the signature manufacturing gamble, consisted of the brazed stainless-steel honeycomb sandwich panels that were to remain hard and withstand permanent heating. Those were light, strong, though not forgiving panels, early work was full of disbonds and skin problems that could only be remedied through process corrections, and not through quick patches. Even the paint had a mission tale to tell. The prototypes had an anti-flash finish, which was chosen to shield the crew and airframe during nuclear explosions, as opposed to addressing temperature control.
Heat was the perpetual collector of Mach 3. Leading edges and the nose were so hot at those speeds that engineers had to combine stainless steel with titanium in key places and consider fuel more than propellant. The Valkyrie employed a fuel circulation method that took heat to the engines after it was inerted and prevented hot fuel vapors to become an issue. It was an airplane system-systems issue, materials, aerodynamics, seals, hydraulics, inlets, any of which could bring a sortie to an untimely end.
Then world which gave the Valkyrie its right began to pass away.
As the XB-70 was changing between requirement and prototype, the threat it was to chase was modernizing. The dissemination of surface-to-air missiles and the development of enhanced radar networks diluted the notion that altitude and velocity could be used as armor. Simultaneously, long-range missile divisions became a reality and deterrent without the need to have crews, tankers and delicate high temperature constructions. Bomber doctrine shifted its focus out of the foreseeable high-altitude tracks to low-level penetration and subsequently low observability and standoff weapons–profiles on which a massive Mach 3 airframe had fewer benefits and many costs.
The most obvious turning point to the program happened on June 8, 1966, with a program-focused publicity flight. One NASA F-104N Starfighter piloted by Joseph A. Walker got trapped in the vortices of the Valkyrie and crashed into it. Walker and Valkyrie co-pilot Major Carl S. Cross had been killed, pilot Alvin S. White ejected and survived seriously injured. Not one radio call, but one that was reported shortly before the accident, quoted Walker saying that he was opposing the sortie. It is too rough and it is of no scientific value.
There was only one Valkyrie left and it still served as a research vehicle up to 1969, contributing to the U.S. knowledge of aerothermal loads, inlet control, and supersonic handling. However, the deeper message of the aircraft is not that it is tragic but rather of timing. The XB-70 proved that a country can be a winner in the production of a gorgeous machine and in addition to that strategy, survivability and sustainment have passed. The Valkyrie did not fall short of going fast; the task which it was commissioned to execute ceased to be the task which counted.
