SENIOR CROWN SR-71
Developed for the USAF as reconnaissance aircraft in the 1960s, SR-71s are still the world's fastest and highest-flying production aircraft. The aircraft can fly more than 2200 mph (Mach 3+ or more than three times the speed of sound) and at altitudes of over 85,000 feet.
In December 1962, the Air Force ordered six “reconnaissance/strike" aircraft for high-speed, high-altitude flights over hostile territory after a nuclear attack—hence its original designator RS. When President Johnson disclosed the aircraft’s existence in July 1964, he mistakenly transposed the designator letters. Air Force officials let the error stand and came up with the Strategic Reconnaissance (SR) category instead.
The SR-71 was developed from the A-12 design, as strategic reconnaissance aircraft. As Lockheed pressed ahead with the R-12, the airplane’s configuration diverged noticeably from that of the A-12. The most obvious difference was the addition of a second crew position, behind the cockpit, to accommodate the reconnaissance systems operator (RSO). The fuselage was lengthened slightly to make room for additional fuel capacity and the tail cone was extended slightly. The nose chines were broadened to improve cruise characteristics and compensate for loss of directional stability due to the change in length. There were numerous internal changes as well with regard to various subsystems.
Compared to the A-12, the SR-71 was about six feet longer, weighed 15,000 pounds more fully loaded, had more prominent nose and body chines and a two-seat cockpit, and carried additional optical and radar imagery systems and ELINT sensors in interchangeable noses. With the added weight, the aircraft flew slower and lower than the A-12 or the YF-12A, but it carried more fuel and had a longer range.
For its reconnaissance mission, the aircraft was outfitted with an advanced synthetic aperture radar system [ASARS-I], an optical bar camera and a technical objective camera wet film system. All were once part of the aircraft's original equipment.
The SR-71 was designed by a team of Lockheed personnel led by Clarence "Kelly" Johnson, at that time vice president of the company's Advanced Development Projects, known as the "Skunk Works." The first version, a CIA reconnaissance aircraft that first flew in April 1962 was called the A-11. The similar A-12 had a lower radar cross section. An interceptor version was developed in 1963 under the designation YF-12A. A USAF reconnaissance variant, called the SR-71, was first flown in 1964. The A-12 and SR-71 designs included leading and trailing edges made of high-temperature fiberglass-asbestos laminates which among other features contributed to their reduced radar signature.
Its existence was publicly announced by President Lyndon Johnson on Feb. 29, 1964, when he announced that an A-11 had flown at sustained speeds of over 2000 mph during tests at Edwards, Calif.
First flight of an SR-71 was on Dec. 22, 1964. The YF-12s were experimental long-range interceptor versions of the same airframe and were first displayed publicly at Edwards on Sept. 30, 1964.
In 1964, SR-71 airframes began to roll off the assembly line. By late 1967, a total of 31 airframes had been delivered to the Air Force. Two of these were SR-71B trainer models with a raised instructor’s cockpit in place of the RSO position. After one of these crashed in January 1968, it was replaced with a trainer built from the aft fuselage of the first YF-12A and the forward section of a structural test article (with added instructor’s position). The new trainer was called the SR-71C.
During their service lives, 12 of the SR-71 airframes were lost to accidents. The operational fleet was retired twice, first in 1990. A few aircraft were reinstated into service, but were retired again in 1997. NASA used several as research platforms and became the final agency to fly the Blackbird. The last SR-71 flight took place on 09 October 1999. Most surviving airframes were placed on display in various museums around the US, and one in the United Kingdom.
The SR-71 is a delta-wing aircraft designed and built by Lockheed. They are powered by two Pratt and Whitney J-58 axial-flow turbojets with afterburners, each producing 32,500 pounds of thrust. Studies have shown that less than 20 percent of the total thrust used to fly at Mach 3 is produced by the basic engine itself. The balance of the total thrust is produced by the unique design of the engine inlet and "moveable spike" system at the front of the engine nacelles, and by the ejector nozzles at the exhaust which burn air compressed in the engine bypass system.
The Blackbird weighs about 34 tons empty, and can carry another 20 tons of special JP-7 jet fuel (enough for about two hours of flight time) in its fuselage and wing tanks. In flight, the fuel is redistributed automatically to maintain the plane's center of gravity and load specifications. Because the Blackbird was designed to expand during flight, it has had a history of fuel tank leaks on the ground.
The airframes are built almost entirely of titanium and titanium alloys to withstand heat generated by sustained Mach 3 flight. The aircraft's largely titanium structure is coated with a special radar-absorbing black paint that helps dissipate the intense frictional heat resulting from flight through the atmosphere at faster than three times the speed of sound. It also gives the plane its distinctive "Blackbird" nickname.
Aerodynamic control surfaces consist of all-moving vertical tail surfaces above each engine nacelle, ailerons on the outer wings, and elevators on the trailing edges between the engine exhaust nozzles. Although most news reports characterize the SR-71 aircraft as `radar evading', in point of fact, however, the SR-71 was one of the largest radar targets ever detected on the FAA's long-range radars. The FAA was able to track it at ranges of several hundred miles. The explanation offered was that the radars were detecting the exhaust plume.
The SR-71A accommodates two crew members in tandem cockpits. The pilot flies the aircraft from the forward cockpit, while a systems operator monitors sensors and experiments in the rear station. For high-speed, high altitude missions, both crew members must wear full-pressure suites that resemble those worn by the early astronauts.
The Air Force needed technical assistance to get the latest reconnaissance version of the A-12 family, the SR-71A, fully operational. Eventually, the Air Force offered NASA the use of two YF-12A aircraft, 60-6935 and 606936. A joint NASA-USAF program was mapped out in June 1969. The NASA YF-12 research program was ambitious; the aircraft flew an average of once a week unless down for extended maintenance or modification. It made 90 flights between 16 July 1971 and 22 December 1978.
Congress appropriated $100 million in the fiscal year 1995 defense budget to reactivate two A-model jets and one B-model pilot trainer aircraft. The Air Force program office for the reactivation of the Blackbirds is at Wright-Patterson AFB, OH. They are operated by Air Combat Command. The move to reactivate the SR-71 Blackbird reconnaissance aircraft was not unopposed. Critics looked at the SR-71 's limitations -- it can effectively operate only in good weather and cannot transmit the images it collects directly to those who need them - -and concluded that the aircraft should be retired.