The SR-71, unofficially known as the "Blackbird," is a long-range, advanced, strategic reconnaissance aircraft developed from the Lockheed A-12 and YF-12A aircraft. The first flight of an SR-71 took place on December 22, 1964, and the first SR-71 to enter service was delivered to the 4200th (later, 9th) Strategic Reconnaissance Wing at Beale AFB, California, in January 1966. The U.S. Air Force retired its fleet of SR-71s on January 26, 1990, because of a decreasing defense budget and high costs of operation. The USAF returned the SR-71 to the active Air Force inventory in 1995 and began flying operational missions in January 1997. The planes were permanently retired a few years later.

Throughout its nearly 24-year career, the SR-71 remained the world's fastest and highest-flying operational aircraft. From 80,000 feet it could survey 100,000 square miles of Earth's surface per hour. On July 28, 1976, an SR-71 set two world records for its class: an absolute speed record of 2,193.167 miles per hour and an absolute altitude record of 85,068.997 feet.

On March 21, 1968, in the aircraft on display, Major (later General) Jerome F. O'Malley and Major Edward D. Payne made the first operational SR-71 sortie. During its career, this aircraft accumulated 2,981 flying hours and flew 942 total sorties (more than any other SR-71), including 257 operational missions, from Beale AFB, Calif.; Palmdale, Calif.; Kadena Air Base, Okinawa and RAF (Base) Mildenhall, England. The aircraft was flown to the Museum in March 1990.

No reconnaissance aircraft in history has operated in more hostile airspace or with such complete impunity than the SR-71 Blackbird. It is the fastest aircraft propelled by air-breathing engines. The Blackbird's performance and operational achievements placed it at the pinnacle of aviation technology developments during the Cold War. The airplane was conceived when tensions with communist Eastern Europe reached levels approaching a full-blown crisis in the mid-1950s. U.S. military commanders desperately needed accurate assessments of Soviet worldwide military deployments, particularly near the Iron Curtain. Lockheed Aircraft Corporation's subsonic U-2 (see NASM collection) reconnaissance aircraft was an able platform but the U. S. Air Force recognized that this relatively slow aircraft was already vulnerable to Soviet interceptors. They also understood that the rapid development of surface-to-air missile systems could put U-2 pilots at grave risk.

Lockheed's first proposal for a new high speed, high altitude, reconnaissance aircraft, to be capable of avoiding interceptors and missiles, centered on a design propelled by liquid hydrogen. This proved to be impracticable because of considerable fuel consumption. Lockheed then reconfigured the design for conventional fuels. This was feasible and the Central Intelligence Agency (CIA), already flying the Lockheed U-2, issued a production contract for an aircraft designated the A-12. Lockheed's clandestine 'Skunk Works' division (headed by the gifted design engineer Clarence L. "Kelly" Johnson) designed the A-12 to cruise at Mach 3.2 and fly well above 18,288 m (60,000 feet). To meet these challenging requirements, Lockheed engineers overcame many daunting technical challenges. Flying more than three times the speed of sound generates 316° C (600° F) temperatures on external aircraft surfaces, which are enough to melt conventional aluminum airframes. The design team chose to make the jet's external skin of titanium alloy to which shielded the internal aluminum airframe. Two conventional, but very powerful, afterburning turbine engines propelled this remarkable aircraft. These power plants had to operate across a huge speed envelope in flight, from a takeoff speed of 334 kph (207 mph) to more than 3,540 kph (2,200 mph). To prevent supersonic shock waves from moving inside the engine intake causing flameouts, Johnson's team had to design a complex air intake and bypass system for the engines.

Skunk Works engineers also optimized the A-12 cross-section design to exhibit a low radar profile. Lockheed hoped to achieve this by carefully shaping the airframe to reflect as little transmitted radar energy (radio waves) as possible, and by application of special paint designed to absorb, rather than reflect, those waves. This treatment became one of the first applications of stealth technology, but it never completely met the design goals.

Test pilot Lou Schalk flew the single-seat A-12 on April 24, 1962, after he became airborne accidentally during high-speed taxi trials. The airplane showed great promise but it needed considerable technical refinement before the CIA could fly the first operational sortie on May 31, 1967 - a surveillance flight over North Vietnam. A-12s, flown by CIA pilots, operated as part of the Air Force's 1129th Special Activities Squadron under the "Oxcart" program. While Lockheed continued to refine the A-12, the U. S. Air Force ordered an interceptor version of the aircraft designated the YF-12A. The Skunk Works, however, proposed a "specific mission" version configured to conduct post-nuclear strike reconnaissance. This system evolved into the USAF's familiar SR-71.

Lockheed built fifteen A-12s, including a special two-seat trainer version. Two A-12s were modified to carry a special reconnaissance drone, designated D-21. The modified A-12s were redesignated M-21s. These were designed to take off with the D-21 drone, powered by a Marquart ramjet engine mounted on a pylon between the rudders. The M-21 then hauled the drone aloft and launched it at speeds high enough to ignite the drone's ramjet motor. Lockheed also built three YF-12As but this type never went into production. Two of the YF-12As crashed during testing. Only one survives and is on display at the USAF Museum in Dayton, Ohio. The aft section of one of the "written off" YF-12As which was later used along with an SR-71A static test airframe to manufacture the sole SR-71C trainer. One SR-71 was lent to NASA and designated YF-12C. Including the SR-71C and two SR-71B pilot trainers, Lockheed constructed thirty-two Blackbirds. The first SR-71 flew on December 22, 1964. Because of extreme operational costs, military strategists decided that the more capable USAF SR-71s should replace the CIA's A-12s. These were retired in 1968 after only one year of operational missions, mostly over southeast Asia. The Air Force's 1st Strategic Reconnaissance Squadron (part of the 9th Strategic Reconnaissance Wing) took over the missions, flying the SR-71 beginning in the spring of 1968.

After the Air Force began to operate the SR-71, it acquired the official name Blackbird-- for the special black paint that covered the airplane. This paint was formulated to absorb radar signals, to radiate some of the tremendous airframe heat generated by air friction, and to camouflage the aircraft against the dark sky at high altitudes.

Experience gained from the A-12 program convinced the Air Force that flying the SR-71 safely required two crew members, a pilot and a Reconnaissance Systems Officer (RSO). The RSO operated with the wide array of monitoring and defensive systems installed on the airplane. This equipment included a sophisticated Electronic Counter Measures (ECM) system that could jam most acquisition and targeting radar. In addition to an array of advanced, high-resolution cameras, the aircraft could also carry equipment designed to record the strength, frequency, and wavelength of signals emitted by communications and sensor devices such as radar. The SR-71 was designed to fly deep into hostile territory, avoiding interception with its tremendous speed and high altitude. It could operate safely at a maximum speed of Mach 3.3 at an altitude more than sixteen miles, or 25,908 m (85,000 ft), above the earth. The crew had to wear pressure suits similar to those worn by astronauts. These suits were required to protect the crew in the event of sudden cabin pressure loss while at operating altitudes.

To climb and cruise at supersonic speeds, the Blackbird's Pratt & Whitney J-58 engines were designed to operate continuously in afterburner. While this would appear to dictate high fuel flows, the Blackbird actually achieved its best "gas mileage," in terms of air nautical miles per pound of fuel burned, during the Mach 3+ cruise. A typical Blackbird reconnaissance flight might require several aerial refueling operations from an airborne tanker. Each time the SR-71 refueled, the crew had to descend to the tanker's altitude, usually about 6,000 m to 9,000 m (20,000 to 30,000 ft), and slow the airplane to subsonic speeds. As velocity decreased, so did frictional heat. This cooling effect caused the aircraft's skin panels to shrink considerably, and those covering the fuel tanks contracted so much that fuel leaked, forming a distinctive vapor trail as the tanker topped off the Blackbird. As soon as the tanks were filled, the jet's crew disconnected from the tanker, relit the afterburners, and again climbed to high altitude.

Air Force pilots flew the SR-71 from Kadena AB, Japan, throughout its operational career but other bases hosted Blackbird operations, too. The 9th SRW occasionally deployed from Beale AFB, California, to other locations to carryout operational missions. Cuban missions were flown directly from Beale. The SR-71 did not begin to operate in Europe until 1974, and then only temporarily. In 1982, when the U.S. Air Force based two aircraft at Royal Air Force Base Mildenhall to fly monitoring mission in Eastern Europe.

When the SR-71 became operational, orbiting reconnaissance satellites had already replaced manned aircraft to gather intelligence from sites deep within Soviet territory. Satellites could not cover every geopolitical hotspot so the Blackbird remained a vital tool for global intelligence gathering. On many occasions, pilots and RSOs flying the SR-71 provided information that proved vital in formulating successful U. S. foreign policy. Blackbird crews provided important intelligence about the 1973 Yom Kippur War, the Israeli invasion of Lebanon and its aftermath, and pre- and post-strike imagery of the 1986 raid conducted by American air forces on Libya. In 1987, Kadena-based SR-71 crews flew a number of missions over the Persian Gulf, revealing Iranian Silkworm missile batteries that threatened commercial shipping and American escort vessels.

As the performance of space-based surveillance systems grew, along with the effectiveness of ground-based air defense networks, the Air Force started to lose enthusiasm for the expensive program and the 9th SRW ceased SR-71 operations in January 1990. Despite protests by military leaders, Congress revived the program in 1995. Continued wrangling over operating budgets, however, soon led to final termination. The National Aeronautics and Space Administration retained two SR-71As and the one SR-71B for high-speed research projects and flew these airplanes until 1999.

On March 6, 1990, the service career of one Lockheed SR-71A Blackbird ended with a record-setting flight. This special airplane bore Air Force serial number 64-17972. Lt. Col. Ed Yielding and his RSO, Lieutenant Colonel Joseph Vida, flew this aircraft from Los Angeles to Washington D.C. in 1 hour, 4 minutes, and 20 seconds, averaging a speed of 3,418 kph (2,124 mph). At the conclusion of the flight, '972 landed at Dulles International Airport and taxied into the custody of the Smithsonian's National Air and Space Museum. At that time, Lt. Col. Vida had logged 1,392.7 hours of flight time in Blackbirds, more than that of any other crewman.

This particular SR-71 was also flown by Tom Alison, the National Air and Space Museum's Chief of Collections Management. Flying with Detachment 1 at Kadena Air Force Base, Okinawa, Alison logged more than a dozen '972 operational sorties. The aircraft spent twenty-four years in active Air Force service and accrued a total of 2,801.1 hours of flight time.

SR-71 Blackbird - NASA

During the 1990s two SR-71 Blackbird aircraft were used by NASA as testbeds for high-speed and high-altitude aeronautical research at Dryden. The aircraft included an SR-71A and SR-71B (the trainer version), loaned to NASA by the U.S. Air Force.

SR-71 - In-flight from tanker

SR-71 In-Flight from Tanker

The SR-71, the most advanced member of the Blackbird family that included the A-12 and YF-12, was designed by a team of Lockheed personnel led by Clarence "Kelly" Johnson, then vice president of Lockheed's Advanced Development Company Projects, commonly known as the "Skunk Works" and now a part of Lockheed Martin Corp.

The Blackbird design originated in secrecy during the late l950s with the A-12 reconnaissance aircraft that first flew in April 1962 and remained classified until 1976. President Lyndon Johnson publicly announced the existence of the YF-12A interceptor variant on Feb. 29, 1964, more than half a year after its maiden flight. The SR-71 completed its first flight on Dec. 22, 1964. More than a decade after their retirement the Blackbirds remain the world's fastest and highest-flying production aircraft ever built.

The Blackbirds were designed to cruise at Mach 3.2, just over three times the speed of sound or more than 2,200 miles per hour and at altitudes up to 85,000 feet. The extreme operating environment in which they flew made the aircraft excellent platforms for conducting research and experiments in a variety of disciplines: aerodynamics, propulsion, structures, thermal protection materials, high-speed and high-temperature instrumentation, atmospheric studies and sonic boom characterization.

SR-71 activities at Dryden were part of NASA's overall high-speed aeronautical research program and involved other NASA research centers, other government agencies, universities and commercial firms. Data from the SR-71 research program will aid designers of future supersonic/hypersonic aircraft and propulsion systems.

Research at Mach 3

One of the first major experiments flown on the NASA SR-71 involved a laser air-data sensor. The sensor used laser light instead of air pressure to generate airspeed and attitude data such as angle-of-attack and sideslip, data normally obtained with small tubes and vanes extending into the airstream or from tubes with flush openings on an aircraft's outer skin. These flights also provided information on the presence of atmospheric particles at altitudes above 80,000 feet, where future hypersonic aircraft will operate. The system used six sheets of laser light projected from the bottom of the airplane. As microscopic-size atmospheric particles passed between the two beams, direction and speed were measured and processed into standard speed and attitude references. An earlier laser air-data measurement system was successfully tested at Dryden on a modified F-l04 testbed aircraft.

The first of a series of flights using the SR-71 as a science camera platform for NASA's Jet Propulsion Laboratory, Pasadena, Calif., was flown in March 1993. From the nose bay of the aircraft, an upward-facing ultraviolet video camera recorded data on celestial objects in wavelengths blocked to ground-based astronomers by Earth’s atmosphere. In another project, researchers at the University of California-Los Angeles used the SR-71 to investigate the use of charged chlorine atoms to protect and rebuild the ozone layer.

As part of NASA's commercialization assistance program, the SR-71 served as a testbed in development of a commercial satellite-based, instant wireless personal communications network, called IRIDIUM. The IRIDIUM system was developed by Motorola's Satellite Communications Division and during developmental testing, the SR-71 acted as a surrogate satellite for transmitters and receivers on the ground.

SR-71 ship #1 on ramp

SR-71 Ship #1 on Ramp

Because of its high-speed capabilities, scientists used the SR-71 in a program to study ways of reducing sonic boom overpressures that are heard on the ground much like sharp thunderclaps by aircraft exceeding the speed of sound. Aircraft designers have used data from the study in efforts to reduce the "peak" of sonic booms and minimize the “startle effect” they produce on the ground.

In 1997 and 1998 the SR-71 carried the NASA/Lockheed Martin Linear Aerospike SR-71 – or LASRE – experiment. The LASRE test apparatus was a half-span scale model of a lifting body with eight thrust cells of a linear aerospike engine, mounted on the back of an SR-71 aircraft during flight at high speeds and altitudes. Outfitted with the test fixture, the aircraft operated like a kind of flying wind tunnel that allowed engineers to gather aerodynamic data under realistic flight conditions.

By the time the Air Force loaned the two SR-71s to Dryden the center already had a decade of past experience with the Blackbirds. Three of the aircraft were flown at the facility between December 1969 and November 1979 in a joint NASA/Air Force program aimed at learning more about the capabilities and limitations of high-speed, high-altitude flight. The first two were YF-12A prototypes of a planned interceptor aircraft based on the initial A-12 design that ultimately evolved into the SR-71 reconnaissance aircraft. While plans were under way to add another aircraft to the fleet, one YF-12A was lost in a non-fatal mishap in 1971. The third aircraft, an SR-71A that was given the designation YF-12C for administrative purposes, soon took its place.

NASA researchers used the YF-12s for a wide variety of experiments involving aerodynamic and thermal loads, aerodynamic drag and skin friction, heat transfer, airframe and propulsion system interactions, inlet control system improvements, high-altitude turbulence, boundary-layer flow, landing gear dynamics, measurement of engine effluents for pollution studies, noise measurements and evaluation of a maintenance monitoring and recording system. On many YF-12 flights medical researchers obtained information on the physiological and biomedical aspects of crews flying at sustained high speeds. Research data from the YF-12 program also validated analytical theories and wind-tunnel test techniques that will improve design and performance of future military and civil aircraft.

SR-71 takeoff with afterburner showing shock diamonds in exhaust

Three SR-71 aircraft were used at different times during the 1990s by NASA as test beds for high-speed and high-altitude aeronautical research.

From February 1972 until July 1973, one YF-12A was used for heat loads testing in Dryden's High Temperature Loads Laboratory (now the Thermostructures Research Facility). The resulting data helped improve theoretical prediction methods and computer models dealing with structural loads, materials, and heat distribution at up to 800 degrees Fahrenheit, the surface temperatures reached during sustained speeds of Mach 3.

SR-71 Specifications and Performance

Two Pratt and Whitney J58 axial-flow turbojets with afterburners, each producing 32,500 pounds of thrust, powered the Blackbirds. Less than 20 percent of the total thrust used to fly at Mach 3 was produced by the engine itself, however. During high-speed cruise conditions the balance of total thrust was produced by the unique design of the engine inlet and a moveable conical spike at the front of each engine nacelle. Under these conditions, air entering the inlets bypassed the engines, going directly to the afterburners and ejector nozzles, thus acting as ramjets.

The airframes were built almost entirely of titanium and other exotic alloys to withstand heat generated by sustained high-speed flight. Capable of cruising at Mach 3 continuously for more than one hour at a time, the Blackbirds provided a unique research platform for thermal experiments because heat-soak temperatures exceeded 600 degrees Fahrenheit.


SR-71 3-view drawing

The aircraft was 107.4 feet (32.73 meters) long, had a wingspan of 55.6 feet (16.94 meters), and stood 18.5 feet (5.63 meters) high (from the ground to the top of the rudders when parked). Gross takeoff weight was about 140,000 pounds (52,253.83 kilograms), including a fuel weight of 80,000 pounds (29,859.33 kilograms). Aerodynamic control surfaces consisted of all-moving vertical tail fins above each engine nacelle and elevons on the outer wings and trailing edges between the engine exhaust nozzles.

NASA crews flew four Lockheed SR-71 airplanes during the 1990s. Two were used for research and two to support Air Force reactivation of the SR-71 for reconnaissance missions. Although the Air Force retired the Blackbirds in 1990, Congress reinstated funding for additional flights several years later. SR-71A (61-7980/NASA 844) arrived at Dryden on Feb. 15, 1990. It was placed into storage until 1992 and served as a research platform until its final flight on Oct. 9, 1999. SR-71A (61-7971/NASA 832) arrived at Dryden on March 19, 1990, but was returned to Air Force inventory as the first aircraft was reactivated in 1995. Along with SR-71A (61-7967), it was flown by NASA crews in support of the Air Force program. SR-71B (61-7956/NASA 831) arrived at Dryden on July 25, 1991, and served as a research platform as well as for crew training and proficiency until October 1997.

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Span: 55 ft. 7 in.
Length: 107 ft. 5 in.
Height: 18 ft. 6 in.
Weight: 170,000 lbs. loaded
Armament: None
Engines: Two Pratt & Whitney J58s of 32,500 lbs. thrust each with afterburner
Crew: Two

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