SR-71 Blackbird

The Lockheed SR-71 is an advanced, long-range, Mach 3 strategic reconnaissance aircraft developed by Lockheed Skunk Works as a Black project. The SR-71 was unofficially named the Blackbird, and called the Habu by its crews, referring to an Okinawan species of pit viper. Clarence “Kelly” Johnson was responsible for many of the design’s innovative concepts. A defensive feature of the aircraft was its high speed and operating altitude, whereby, if a surface-to-air missile launch were detected, standard evasive action was simply to accelerate. The SR-71 was in service from 1964 to 1998 as top secret reconnaissance aircraft. Only 32 SR-71’s were built. Frequently called the Cold War Bird.

SR-71 was originally classified as the R-12. Public disclosure of the program and its renaming came as a shock to everyone at the Skunk Works and to Air Force personnel involved in the program. All of the printed maintenance manuals, flight crew handbooks, blueprints, training slides and materials had to be reprinted.

A difficult issue with flight at over Mach 3 is the high temperatures generated. As an aircraft moves through the air, the air in front of the aircraft compresses and this heat conducts into the aircraft‘s airframe. To help with this, high temperature materials were needed and the airframe was substantially made of titanium, obtained from the USSR, at the height of the Cold War. Lockheed used many guises to prevent the Soviet government from knowing what the titanium was to be used for. Finished aircraft were painted dark blue, almost black, to increase the emission of internal heat and to act as camouflage against the sky. The aircraft was designed to minimize its radar cross-section, an early attempt at stealth design.

The Pratt & Whitney J58-P4 engines used in the Blackbird were the only military engines ever designed to operate continuously on afterburner, and became more efficient as speed increased. Each J58 engine could produce 32,500 lbf of static thrust. Conventional jet engines cannot operate continuously on afterburner.

Crews flying the SR-71 at 80,000 Feet faced two main survival problems. First, with a standard pressure demand oxygen mask, human lungs cannot absorb enough of 100% oxygen above 43,000 feet to sustain consciousness and life. Second, the instant heat rise pulse on the body when exposed to a Mach 3.2 air flow during ejection would be about 450 °F. To solve these problems, the David Clark Company was hired to produce protective full pressure suits for all of the crew members of the SR-71. These suits were later adopted for use on the Space Shuttle during ascent.

The SR-71 was the world’s fastest and highest-flying operational manned aircraft throughout its career. From an altitude of 80,000 feet, it could survey 100,000 square miles per hour of the Earth’s surface. In addition, it was accurate enough to take a legible picture of a car’s license plate from this altitude. On 28 July 1976, an SR-71 broke the world record for its class, an absolute speed record of 2193.17 mph and an “absolute altitude record” of 85,069 feet. Several aircraft exceeded this altitude in zoom climbs but not in sustained flight.

I don’t know how many will read this, but some of these facts and statistics are amazing. As you probably know, it took almost twenty years before the United States, Pentagon, Air Force or Lockheed would admit the Blackbird existed.


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