Two SR-71 aircraft have been used by NASA as testbeds for high speed, high
altitude aeronautical research. The aircraft, an SR-71A and an SR-71B pilot
trainer aircraft are based at a NASA's base somewhere in southern California.
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 mph (Mach 3+ or more than three times the speed
of sound) and at altitudes over 85,000 feet. 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). 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.
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.
The first of a series of flights using the SR-71 as a science camera platform
for NASA's Jet Propulsion Laboratory was flown in March 1993. From the nosebay
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 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
Sonic Boom
Mitigation 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. One of Dryden's SR-71s was used for the
Linear
Aerospike SR experiment, or LASRE, in which the unique aerospike engine
developed for the X-33 Reusable Launch Vehicle was mounted on the back of the
SR-71.
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.
The aircraft are 107.4 feet (32.73 m) long, have a wing span of 55.6 feet
(16.94 m), and are l8.5 feet (5.63 m) high (ground to the top of the rudders
when parked). Gross takeoff weight is about 140,000 pounds (52253.83 kg),
including a fuel weight of 80,000 pounds (29859.33 kg). 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.
Data from the SR-71 high speed research program will be used to aid designers of
future supersonic/hypersonic aircraft and propulsion systems.