As AirVenture 2000 participants celebrate speed, the undisputed kings of speed await a new challenge at NASA’s Dryden Flight Research Center in California’s Mojave Desert. Dryden, located on Edwards Air Force Base, is NASA’s flight research center, and home to the last serviceable members of Lockheed’s memorable triple-sonic Blackbird family of jets.
While the SR-71 version of the Blackbird allowed the U.S. Air Force to redefine aerial reconnaissance from the 1960s through the 1980s with parameters exceeding 2,200 miles an hour and 85,000 feet altitude, a few SR-71s and earlier YF-12 fighter versions provided NASA with high speed research aircraft that could not be matched anywhere in the world.
YF-12s at Dryden — NASA gained access to two YF-12s at Dryden under a joint NASA/Air Force research program spanning a decade beginning in 1969. A third Blackbird, shared by NASA but used mostly by the Air Force, was written off because of an inflight fire in 1971.
The YF-12s, characterized by truncated chines just ahead of the cockpit, gave researchers at the four NASA aeronautical centers (Dryden, Ames, Langley, and Lewis — now Glenn) opportunity to probe the aerodynamic, thermal, and structural effects of sustained high-altitude flight at three times the speed of sound. The Blackbirds routinely recorded temperatures of more than 500 degrees Fahrenheit on portions of their titanium alloy structure.
During the span of the YF-12 research effort at Dryden, NASA and Air Force missions amassed about 450 flight hours during 297 flights. NASA YF-12 pilots included Donald Mallick and the versatile Fitzhugh Fulton, assisted by NASA flight engineers Ray Young, Victor Horton, and Lorenzo Barnett.
The NASA roster of YF-12 pilots also included: William H. Dana, Einar K. Enevoldson, Stephen D. Ishmael, Gary E. Krier, John A. Manke, Thomas C. McMurtry, and Michael R. Swann. Air Force crews also flew the YF-12s during the program.
NASA set about creating a data base of information on phenomena
encountered in the YF-12s’ unique operating regime. More than 125 technical reports were published as a result of the NASA YF-12
explorations high over the Mojave Desert. Contributions include a still-viable data base distinguishing and measuring both thermal and aerodynamic (friction) heating of aircraft structures, important to the design of future high-speed aircraft.
One of the two YF-12As made available to NASA was lost on June 24, 1971, when an Air Force crew experienced an engine fire. The two crewmembers safely ejected, but a fuel-fed pyre in the desert marked the end of that research aircraft. It was replaced by the so-called YF-12C, which actually was an SR-71 redesignated.
The sole surviving YF-12A, aircraft number 60-6935, was ferried by an Air Force crew on Nov. 7, 1979, to its permanent home at the Air Force Museum near Dayton, Ohio.
SR-71s in the Desert — NASA Dryden’s other SR-71s arrived beginning in 1990, no longer cloaked in the secrecy that once surrounded the so-called YF-12C (SR-71A 61-7951). SR-71A serial number 61-7980 was given NASA number 844; the sole SR-71B (serial 61-7956), with a raised second cockpit, carries NASA number 831. SR-71A number 61-7971 was given NASA number 832 and served at Dryden from 1991 through 1994.
An improved laser air data collection system was tested early in NASA’s SR-71 program. The system uses laser light to acquire airspeed and attitude reference data, and verified the existence of atmospheric particles at altitudes of 80,000 feet and higher, where future hypersonic aircraft are expected to fly.
A NASA SR-71 used its high altitude capabilities to vault over atmospheric conditions that thwarted ground-based astronomers in efforts to study celestial objects with a camera using ultraviolet wavelengths. Another NASA project flew an SR-71 as a "surrogate satellite" for a communications satellite development test.
Air-to-air and air-to-ground sonic boom shockwave and pressure
measurements were made with a NASA SR-71 chased by a NASA F-16XL from Dryden, for research aimed at reducing the felt sonic boom on the ground.
In the fall of 1998, a Dryden-based SR-71 finished tests with a linear aerospike engine mounted atop its fuselage, foretelling a hoped-for future of NASA Blackbirds as flying wind tunnels for various research purposes.
The last airworthy SR-71s are at a crossroads today. Their Air Force counterparts have all been retired. An unequaled research asset of national importance, the SR-71s are expensive to maintain, and more so to operate. Crews must be kept proficient, and special personal equipment for each crewmember is pricey; pilot pressure suits, comparable to those worn by astronauts, cost about $150,000.
It will probably take the promise of a test program, with funding, to keep the remaining airworthy SR-71s flying into the future. The most recent flight of a NASA SR-71 was October 9, 1999. For now, the Blackbirds’ last stand may be on a sun-baked tarmac in the Mojave Desert.