Flight Research
In March 1996, NASA initiated flight testing of a new thrust
vectoring concept that could lead to significant increases in
the performance of both civil and military aircraft flying at
subsonic or supersonic speed.
The tests at Dryden Flight Research Center are part of a program
known as ACTIVE (Advanced Controls Technology for Integrated
Aircraft), a collaborative effort of NASA, the Air Force's Wright
Laboratory, McDonnell Douglas Aerospace (MDA), and Pratt &
Whitney Government Engines & Space Propulsion unit (P&W).
The F-15 ACTIVE is exploring a vectored thrust system that
could replace conventional aerodynamic control surfaces.
The test aircraft is a twin-engine F-15 ACTIVE, a modified
version of the Air Force F-15B fighter built by MDA and powered
by F-100-PW-229 engines, each of which is equipped with a nozzle
that can swivel 20 degrees in any direction, giving the aircraft
thrust control in the pitch (up and down) and yaw (left-right)
directions. This vectored (deflected) thrust system could replace
conventional drag-inducing aerodynamic controls and thereby gain
increased fuel economy or range.
The tests began with four flights in March/April, then progressed
to the first supersonic flight on April 24. On that occasion,
the F-15 ACTIVE successfully demonstrated both pitch and yaw
deflections at speeds of Mach 1.2 to 1.5. The flight test plan
contemplated about 60 flights totaling 100 hours at speeds up
to Mach 1.85 and angles of attack (the angle between the aircraft's
body/wings and its actual flight path) up to 30 degrees.
The F-15 ACTIVE program is representative of the type of flight
research conducted by NASA to explore new technologies and new
flight regimes. NASA conducts such programs independently or
in cooperation with U.S. industry and the Department of Defense,
sometimes in cooperation with international development teams.
Another example of a Dryden flight research program is NASA's
High Alpha investigation. High Alpha refers to high angles of
attack, a flight regime in which the airflow becomes extremely
complex. To provide aircraft manufacturers with a technology
base for designing high performance aircraft capable of "supermaneuverability"
and of maintaining stability/controllability at high angles of
attack, NASA conducted the decade-long High Alpha program that
concluded on May 29, 1996 with the final flight of NASA's F-18
HARV (High Alpha Research Vehicle).
NASA's veteran F-18 HARV research aircraft concluded a decade-long
flight test program that explored aircraft maneuverability and
controllability at high angles of attack.
In the first phase of the program, initiated in 1987, the
F-18 HARV explored angles of attack up to 55 degrees. In the
second phase, NASA investigated thrust vectoring technology to
determine the impact on aircraft maneuverability at high angles
of attack. In the final phase, the F-18 HARV's handling qualities
were evaluated by 14 different pilots representing NASA, the
Department of Defense, and support contractors McDonnell Douglas
Aerospace and Calspan Corporation.
Among other flight projects under way at Dryden are two examples
of test programs intended to support NASA activities not directly
connected with aeronautics advancement. One is a project involving
airborne tests of an advanced thermal protection system (TPS)
for use on the X-33 Reusable Launch Vehicle (see page 30). The
project employs an F-15B Flight Test Fixture-II (FTF-II) aircraft
for atmospheric testing (the ascent and landing phases of the
launch vehicle's operation), where the potential threat to the
TPS is impact with rain drops, cloud droplets or ice crystals.
Test participants include Marshall Space Flight Center and Rockwell
International.
Another new program involves testing the Theseus, a robot
aircraft to be employed in NASA's Mission To Planet Earth program
for research in such areas as stratospheric ozone depletion and
the atmospheric effects of future high speed civil transport
engines. Built by Aurora Flight Sciences Corporation, Fairmont,
West Virginia, Theseus is a twin-engine propeller-driven craft
with a 143-foot wingspan. Constructed largely of composite materials,
it is capable of carrying 700 pounds of science instruments to
altitudes above 60,000 feet for durations of more than 24 hours.
The plane made its initial flight at Dryden in May 1996.
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