The SR-71 Blackbird
The joint NASA-Air Force YF-12 research program lasted 10 years (1969-1979) and produced a wealth of data on materials, structures, loads, heating, aerodynamics, and performance for high-speed aircraft.
Because air friction subjected the plane to extreme heat during flight, the YF-12 was also used to study high-temperature phenomena unrelated to the plane itself. Perhaps the most significant of these studies was the Cold Wall Experiment, which involved exposing a cooled cylinder to the friction and heat of a Mach 3 environment.
The cylinder, which was hollow, equipped with sensors, and mounted beneath the aircraft, was cooled with liquid nitrogen and insulated from the heat that was generated during flight. When the plane neared Mach 3, a primer cord was used to blow the insulation from the frigid cylinder. Temperature, pressures, and friction readings from the cylinder in flight were compared with information developed from theoretical analysis and wind-tunnel simulation. The findings were a major achievement in fluid dynamics research.
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