No reconnaissance aircraft has ever had to fly in more hostile airspace, yet with total impunity, as has the SR-71 Blackbird. The SR-71 remains the fastest aircraft ever built as a marvel of aviation technology powered by air-breathing engines. Conceived during the height of Cold War tensions in the mid-1950s, the SR-71 developed into a much-needed critical asset for U.S. military commanders desiring accurate intelligence about Soviet military deployments.
The SR-71 originated from the subsonic U-2 reconnaissance aircraft at Lockheed Aircraft Corporation. While the U-2 had been a very good platform, it became quite apparent that this was indeed a very vulnerable aircraft to Soviet interceptors and surface-to-air missiles when one was shot down over the Soviet Union in 1960. This most definitely made apparent the requirement for a new high-speed, high-altitude-reconnaissance aircraft that would be capable of evading both interceptors and missiles.
The initial Lockheed proposal was for an aircraft powered by liquid hydrogen, but this was abandoned when it became apparent that consumption would be too great. The design was adapted to run on conventional fuel and the A-12 – the predecessor of the SR-71 – emerged. The A-12 was developed by the classified part of Lockheed known as ‘Skunk Works’, headed by Clarence L. “Kelly” Johnson; it cruised at Mach 3.2 and above 60,000 feet. The design team overcame a myriad of technical challenges, not the least of which was withstanding outside air temperatures of 600°F generated by flying at such high speeds. The designers selected titanium alloy for the external skin of the jet to protect the internal aluminum airframe.
It was yet another early application of stealth technology wherein the design featured a low radar profile through careful shaping of the airframe and special paint designed to absorb radar waves. Despite this, the A-12 never quite met its stealth design goals.
The A-12 first took to the skies with test pilot Lou Schalk on April 24, 1962. After extensive refinement, the CIA flew the first operational sorties of the plane over North Vietnam on May 31, 1967. The U.S. Air Force was eyeing this very technology for its use and ordered an interceptor version in 1960, which it called YF-12A. However, Skunk Works proposed a “specific mission” version for post-nuclear strike reconnaissance, which took shape as the SR-71.
Fifteen A-12s were produced by Lockheed, including a special two-seat trainer version. Two A-12s were modified to carry a reconnaissance drone, designated D-21, and were redesignated M-21s. At high speeds, the M-21s launched the drones to ignite their ramjet motors. Lockheed also produced three YF-12As, but only one survives today, displayed at the USAF Museum in Dayton, Ohio.
SR-71, named Blackbird for its unique black paint, first flew on December 22, 1964. The paint absorbed radar signals radiated airframe heat and provided camouflage against a dark sky at high altitudes. The Pratt & Whitney J-58 engines were designed to operate continuously in the afterburner and had the best fuel efficiency at Mach 3+ cruise speeds. A typical reconnaissance flight required multiple aerial refuelings, each of which involved descending to the tanker’s altitude and slowing to subsonic speeds, with resultant skin-panel shrinkage and leakage of fuel.
The SR-71 had operated from various bases, both in Kadena AB, Japan, and Beale AFB in California. It had given key intelligence in most geopolitical events of the time: the 1973 Yom Kippur War, the Israeli invasion of Lebanon, and the 1986 raid on Libya. Indeed, the SR-71 was an essential tool in a world where space-based observation systems were on the rise for global intelligence gathering.
Operating costs were extremely high for the SR-71 program, and competition from satellites was strong. The Air Force stopped flying SR-71s in January of 1990, but the program was revived in 1995 by Congressional action before its cancellation. NASA kept two SR-71As and one SR-71B that were used in high-speed research projects through 1999.
One SR-71A, on March 6, 1990, took off from Los Angeles and landed in Washington D.C. in a record 1 hour, 4 minutes, and 20 seconds, averaging 2,124 mph. This very plane is now on exhibit at the Smithsonian’s National Air and Space Museum and accumulated 2,801.1 flying hours during its 24 years of service.
The SR-71 Blackbird remains an icon of Cold War ingenuity and a testimony to the imagination of its engineers and pilots who brought it into flight.