XB-70 Valkyrie

The North American XB-70 Valkyrie was an experimental U.S. supersonic bomber developed in the 1950s–60s as a Mach-3, high-altitude strategic aircraft, featuring an advanced stainless-steel and titanium honeycomb structure designed to withstand sustained skin temperatures above 300 °C from aerodynamic heating. It was powered by six General Electric YJ93 turbojet engines fed by variable-geometry inlets that compressed airflow for efficient supersonic combustion, and it used distinctive drooping wingtips that folded downward at speed to exploit compression lift and improve directional stability. The XB-70 cruised at around 70,000 feet, reached top speeds over Mach 3, and incorporated one of the first large-scale fly-by-wire and analog stability-augmentation systems to manage its slender delta-wing design. Although only two prototypes were built and the bomber program was cancelled in favor of ballistic missiles and lower-altitude penetration strategies, the Valkyrie’s innovations directly influenced later supersonic aircraft research, including the Soviet Tu-144 and the Anglo-French Concorde, and remain a landmark in high-speed aerospace engineering.