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Two SR-71 aircraft have been used by NASA as test-beds for high-speed and high-altitude aeronautical research. The aircraft, an SR-71A and an SR-71B pilot trainer aircraft, have been based here at NASA's Dryden Flight Research Center, Edwards, California. They were transferred to NASA after the U.S. Air Force program was cancelled.

As research platforms, the aircraft can cruise at Mach 3 for more than one hour. For thermal experiments, this can produce heat soak temperatures of over 600 degrees Fahrenheit (F). This operating environment makes these aircraft excellent platforms to carry out research and experiments in a variety of areas -- aerodynamics, propulsion, structures, thermal protection materials, high-speed and high-temperature instrumentation, atmospheric studies, and sonic boom characterization.

The SR-71 was used in a program to study ways of reducing sonic booms or over pressures that are heard on the ground much like sharp thunderclaps when an aircraft exceeds the speed of sound. Data from this Sonic Boom Mitigation Study could eventually lead to aircraft designs that would reduce the "peak" overpressures of sonic booms and minimize the startle affect they produce on the ground.

One of the first major experiments to be flown in the NASA SR-71 program was a laser air data collection system. It used laser light instead of air pressure to produce airspeed and attitude reference data, such as angle of attack and sideslip, which are normally obtained with small tubes and vanes extending into the airstream.

One of Dryden's SR-71s was used for the Linear Aerospike, or LASRE Experiment. Another earlier project consisted of a series of flights using the SR-71 as a science camera platform for NASA's Jet Propulsion Laboratory in Pasadena, California. An upward-looking ultraviolet video camera placed in the SR-71’s nosebay studied a variety of celestial objects in wavelengths that are blocked to ground-based astronomers.

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Dryden has had a decade of past experience at sustained speeds above Mach 3. Two YF-12A aircraft and an SR-71 designated as a YF-12C were flown at the center between December 1969 and November 1979 in a joint NASA/USAF program to learn more about the capabilities and limitations of high-speed, high-altitude flight. The YF-12As were prototypes of a planned interceptor aircraft based on a design that later evolved into the SR-71 reconnaissance aircraft. Dave Lux was the NASA SR-71 project manger for much of the decade of the 1990s, followed by Steve Schmidt.

Developed for the USAF as reconnaissance aircraft more than 30 years ago, SR-71s are still the world's fastest and highest-flying production aircraft. The aircraft can fly at speeds of more than 2,200 miles per hour (Mach 3+ or more than three times the speed of sound) and at altitudes of over 85,000 feet.

The Lockheed Skunk Works (now Lockheed Martin) built the original SR-71 aircraft. Each aircraft is 107.4 feet long, has a wingspan of 55.6 feet, and is 18.5 feet high (from the ground to the top of the rudders, when parked). Gross takeoff weight is about 140,000 pounds, including a possible fuel weight of 80,280 pounds. The airframes are built almost entirely of titanium and titanium alloys to withstand heat generated by sustained Mach 3 flight. Aerodynamic control surfaces consist of all-moving vertical tail surfaces, ailerons on the outer wings, and elevators on the trailing edges between the engine exhaust nozzles.

The two SR-71s at Dryden have been assigned the following NASA tail numbers: NASA 844 (A model), military serial 61-7980 and NASA 831 (B model), military serial 61-7956. From 1990 through 1994, Dryden also had another "A" model, NASA 832, military serial 61-7971. This aircraft was returned to the USAF inventory and was the first aircraft reactivated for USAF reconnaissance purposes in 1995. It has since returned to Dryden along with SR-71A 61-7967.

The last SR-71 flight was made on Saturday October 9, 1999, at the Edwards AFB air show. The aircraft used was NASA 844. The aircraft was also scheduled to make a flight the following day, but a fuel leak grounded the aircraft and prevented it from flying again. The NASA SR-71s were then put in flyable storage, where they remained until 2002. They were then sent to museums.

 

 

Dryden And  The SR-71

 

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Developed for the USAF as reconnaissance aircraft more than 30 years ago, SR-71s were the world's fastest and highest-flying production aircraft. The aircraft could fly at speeds of more than 2,200 miles per hour (Mach 3+, or more than three times the speed of sound) and at altitudes of over 85,000 feet.

Dryden had a decade of past experience at sustained speeds above Mach 3. Two YF-12A aircraft and an SR-71 designated as a YF-12C were flown at the center between December 1969 and November 1979 in a joint NASA/USAF program to learn more about the capabilities and limitations of high-speed, high-altitude flight. The YF-12As were prototypes of a planned interceptor aircraft based on a design that later evolved into the SR-71 reconnaissance aircraft.

The two SR-71s at Dryden were assigned the following NASA tail numbers: NASA 844 (A model), military serial 61-7980 and NASA 831 (B model), military serial 61-7956. From 1990 through 1994, Dryden also had another "A" model, NASA 832, military serial 61-7971. This aircraft was returned to the USAF inventory and was the first aircraft reactivated for USAF reconnaissance purposes in 1995. It has since returned to Dryden along with SR-71A 61-7967.

The last SR-71 flight was made on Saturday October 9, 1999, at the Edwards AFB air show. The aircraft used was NASA 844. The aircraft was also scheduled to make a flight the following day, but a fuel leak grounded the aircraft and prevented it from flying again. The NASA SR-71s were then put in flyable storage, where they remained until 2002. They were then sent to museums.

 

 

The SR-71 Blackbird

 

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Two SR-71 aircraft were used by NASA as testbeds for high-speed, high-altitude aeronautical research. The aircraft, an SR-71A and an SR-71B pilot trainer aircraft were based at NASA's Dryden Flight Research Center, Edwards, Calif. They have been loaned to NASA by the U.S. Air Force. Developed for the USAF as reconnaissance aircraft more than 30 years ago, SR-71s are still the world's fastest and highest-flying production aircraft.

The aircraft can fly more than 2200 miles per hour (Mach 3+ or more than three times the speed of sound) and at altitudes of over 85,000 feet. This operating environment makes the aircraft excellent platforms to carry out research and experiments in a variety of areas — aerodynamics, propulsion, structures, thermal protection materials, high-speed and high-temperature instrumentation, atmospheric studies and sonic boom characterization.

Data from the SR-71 high-speed research program may be used to aid designers of future supersonic/hypersonic aircraft and propulsion systems, including a high-speed civil transport.

The SR-71 program at Dryden was part of NASA's overall high-speed aeronautical research program, and projects involve other NASA research centers, other government agencies, universities and commercial firms.

 

 

Research At Mach 3

 

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One of the first major experiments to be flown in the NASA SR-71 program was a laser air-data collection system. It used laser light instead of air pressure to produce airspeed and attitude reference data such as angle of attack and sideslip normally obtained with small tubes and vanes extending into the air stream or from tubes with flush openings on an aircraft's outer skin. The flights provided information on the presence of atmospheric particles at altitudes of 80,000 feet and above where future hypersonic aircraft will be operating. The system used six sheets of laser light projected from the bottom of the "A" model. 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 collection system was successfully tested at Dryden on an F-l04 testbed.

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-looking ultraviolet video camera studied a variety of celestial objects in wavelengths that are blocked to ground-based astronomers.

The SR-71 has also been used in a project for researchers at the University of California-Los Angeles (UCLA) who were investigating the use of charged chlorine atoms to protect and rebuild the ozone layer.

In addition to observing celestial objects in the various wavelengths, future missions could include "downward" looking instruments to study rocket engine exhaust plumes, volcano plumes and the Earth's atmosphere, as part of the scientific effort to reduce pollution and protect the ozone layer.

The SR-71, operating as a testbed, also has been used to assist in the development of a commercial satellite-based, instant wireless personal communications network, called the IRIDIUM system, under NASA's commercialization assistance program. The IRIDIUM system was being developed by Motorola's Satellite Communications Division. During the development tests, the SR-71 acted as a "surrogate satellite" for transmitters and receivers on the ground.

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The SR-71 also has been used in a program to study ways of reducing sonic boom overpressures that are heard on the ground much like sharp thunderclaps when an aircraft exceeds the speed of sound. Data from the study could eventually lead to aircraft designs that would reduce the "peak" of sonic booms and minimize the startle affect they produce on the ground.

Instruments at precise locations on the ground record the sonic booms as the aircraft passes overhead at known altitudes and speeds. An F-16XL aircraft was also used in the study. It was flown behind the SR-71, probing the near-field shockwave while instrumentation recorded the pressures and other atmospheric parameters.

In November 1998 the SR-71 completed the NASA/Lockheed Martin Linear Aerospike SR-71 experiment (LASRE). LASRE was a small, half-span model of a lifting body with eight thrust cells of an aerospike engine, mounted on the back of an SR-71 aircraft and operating like a kind of "flying wind tunnel."

During seven flights, the experiment gained information that may help Lockheed Martin predict how operation of aerospike engines at altitude will affect vehicle aerodynamics of a future reusable launch vehicle.

 

 

Dryden's Mach 3 History

 

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B Model SR-71 At Sunset

Dryden has a decade of past experience at sustained speeds above Mach 3. Two YF-12 aircraft were flown at the facility between December 1969 and November 1979 in a joint NASA/USAF program to learn more about the capabilities and limitations of high speed, high-altitude flight. The YF-12s were prototypes of a planned interceptor aircraft based on a design that later evolved into the SR-71 reconnaissance aircraft.

Research information from the YF-12 program was used to validate analytical theories and wind-tunnel test techniques to help improve the design and performance of future military and civil aircraft. The American supersonic transport project of the late 1960s and early 1970s would have benefited greatly from YF-12 research data. The aircraft were a YF-12A (tail #935) and a YF-12C (tail #937). Tail number 937 was actually an SR-71 that was called a YF-12C for security reasons. These aircraft logged a combined total of 242 flights during the program. A third aircraft, a YF-12A (tail #936), was flown by Air Force crews early in the program. It was lost because of an inflight fire in June l971. The crew was not hurt.

The YF-12s were used for a wide range of experiments and research. Among the areas investigated were aerodynamic loads, aerodynamic drag and skin friction, heat transfer, thermal stresses, airframe and propulsion system interactions, inlet control systems, 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.

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

 

 

SR-71 Specifications And Performance

 

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A & B Model SR-71

The SR-71 was designed and built by the Lockheed Skunk Works, now the Lockheed Martin Skunk Works. SR-71s 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.

Speed of the aircraft is announced as Mach 3.2 — more than 2000 miles per hour (3218.68 kilometers per hour). They have an un-refueled range of more than 2000 miles (3218.68 kilometers) and fly at altitudes of over 85,000 feet (25908 meters).

As research platforms, the aircraft can cruise at Mach 3 for more than one hour. For thermal experiments, this can produce heat soak temperatures of over 600 degrees (F). The aircraft are 107.4 feet (32.73 meters) long, have a wing span of 55.6 feet (16.94 meters, and are l8.5 feet (5.63 meters) high (ground to the top of the rudders when parked). Gross takeoff weight is about 140,000 pounds (52253.83 kilograms), including a fuel weight of 80,000 pounds (29859.33 kilograms).

The airframes are built almost entirely of titanium and titanium alloys to withstand heat generated by sustained Mach 3 flight. 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.

 The two SR-71s at Dryden have been assigned the following NASA tail numbers: NASA 844 (A model), military serial 64-17980, manufactured in July 1967, and NASA 831 (B model), military serial 64-17956, manufactured in September 1965. From 1991 through 1994, Dryden also had another "A" model, NASA 832, military serial 64-17971, manufactured in October 1966. This aircraft was returned to the USAF inventory and was the first aircraft reactivated for USAF reconnaissance purposes in 1995.

The SR-71 last flight took place in October 1999.

 

 

Development History

 

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The SR-71 was designed by a team of Lockheed personnel led by Clarence "Kelly" Johnson, at that time vice president of the Lockheed's Advanced Development Company, commonly known as the "Skunk Works."

The basic design of the SR-71 and YF-12 aircraft originated in secrecy in the late l950s with the aircraft designation of A-11. 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 miles per hour during tests at Edwards Air Force Base, Calif.

Development of the SR-71s from the A-11 design, as strategic reconnaissance aircraft, began in February 1963. First flight of an SR-71 was on Dec. 22, 1964.

The SR-71 Wraps Up Its Flight Research Series

Leslie A. Williams
Public Affairs Specialist

"A 1999 four-flight research series for the SR-71 Blackbird, with a 41-foot-long test fixture mounted atop of the rear section of the aircraft, wrapped up Sept. 27 at Dryden.

The flights showed that the fixture barely impacted the SR-71's stability, handling and flying characteristics while soaring at Mach 3, or three times the speed of sound.

SR-71 Project Manager Steve Schmidt is pleased with the flight series.

'It went better than we predicted. Now we will wait for an opportunity, or a customer with a project. There are several in the wings,' he said.

'It flew like a scalded cat,' said the SR-71 flight test engineer Marta Bohn-Meyer. She said the plane was unbelievable in how it pushed to go faster.

The SR-71 stopped short of reaching one test point of going more than Mach 3 due to the failure of the liquid nitrogen system that was used to purge the test fixture. Without proper purge, there was a concern of overheating the fixture's internal systems. This purge system has proven very effective in past flights, said Tim Moes, Dryden's chief engineer for these research flights.

He added that the cause of the purge system failure is now well understood and procedures will be instituted to prevent this failure in the future. Although the two-hour flight did not reach Mach 3.2, the combined four-flight series proved that the SR-71 is a viable testbed for future technologies that need a high-speed, high-altitude flight environment.

Data obtained on the previous flight to Mach 3 can be confidently extrapolated to Mach 3.2, Moes said. Unlike wind tunnels that are constrained by its walls, the SR-71 airplane flies in actual atmospheric conditions, such as moisture and temperatures, at extreme altitudes and speeds making it an ideal testbed for supersonic flight.

NASA's Revolutionary Concepts (REVCON) project is one example of possible future use of the SR-71 as a testbed. The RevCon project encourages the development of ideas that could lead to revolutionary experimental planes.

The Pulse Detonation Engine (PDE), one of the first RevCon projects, is a revolutionary approach for future high-speed jet propulsion. The engine will have fewer parts, yet greater propulsion efficiency, resulting in lower maintenance and direct operating costs. A proposal to fly the PDE captive carry atop the rear section of Dryden's SR-71 Blackbird is being discussed."

 

NASA's SR-71 Is Back To Work

Leslie Mathews
Public Affairs Specialist

"Dryden sent its fastest and highest-flying airplane, the SR-71A, into the air for further research flights to evaluate the its performance, handling and flying qualities with a test fixture mounted atop the aft section of the aircraft. This test fixture was originally used for the Linear Aerospike SR-71 Experiment (LASRE), supporting research for the X-33 program.

The flight of the SR-71 A model June 30 was the first flight of this aircraft since October 29, 1998. The aircraft reached a maximum speed of Mach 2.25, about 1,450 mph at 55,000 feet. Three more flights are scheduled between July and September.

"The long anticipated prospect of getting the SR-71 aircraft back in the air is exhilarating," said Steve Schmidt, Dryden's SR-71 project manager. "This phase of the flight research program has gotten off to a great start in that the aircraft and project team performed flawlessly, which is further testament of the cooperative teamwork that has been a sustaining hallmark of the SR-71 program."

NASA's B model is used for proficiency training for pilots and the flight test engineers. Recently the B model completed its planned 200-hour phase inspection and has been put into flyable storage. These two SR-71s have been on loan to NASA from the U.S. Air Force, which just transferred ownership to NASA.

In addition to those two SR-71s, the Air Force turned over possession of its other two other flyable SR-71s, which will complement the two NASA planes in future flight research programs, providing unsurpassed flexibility as well as additional capabilities to perform multiple high-speed research experiments.

The SR-71 can fly more than 2,200 miles per hour, more than Mach 3, or three times the speed of sound, and at altitudes of more than 85,000 feet. Data from the SR-71's high-speed research program will be used to aid designers of future supersonic and hypersonic aircraft and propulsion systems. SR-71 flights have also provided information on the presence of atmospheric particles at extremely high altitudes, where future hypersonic aircraft will be operating.

As research platforms, the SR-71s carry out research and experiments in a variety of areas: aerodynamics, propulsion, structures, thermal protection materials, high-speed and high temperature instrumentation, atmospheric studies and sonic boom characteristics.

The LASRE project was a small, half-span model of a lifting body positioned on the rear of the SR-71 aircraft, which operated like an "airborne wind tunnel." The SR-71 has also acted as a surrogate satellite for transmitters and receivers on the ground, assisting in the development of a commercial satellite-based, instant and wireless, personal-communications network, called IRIDIUM.

Another project with the SR-71 joined NASA and the University of California-Los Angeles (UCLA), investigating the use of charged chlorine atoms to protect and rebuild the ozone layer. Ongoing research in high-speed, high-altitude flight continues to gain interest among the scientific community, industry and other government agencies."

NASA