Eagle Is Testbed For LIFT Operations
To help the Space Shuttle safely return to flight, NASA
engineers are acquiring data on how insulating foam debris or
"divots" behave when these small pieces are shed from the Shuttle's
external fuel tank during launch.
NASA's Dryden Flight Research Center at Edwards Air Force Base,
CA, is conducting a series of flight tests of the divots as part of
the Return to Flight team effort. The Lifting Insulating Foam
Trajectory (LIFT) flight test series at Dryden is using the
center's F-15B Research Testbed aircraft to test these "divots"
in a real flight environment at speeds up to about Mach 2, or
twice the speed of sound.
Image Right: All six divots of thermal insulation foam have been
ejected from the flight test fixture on NASA's F-15B testbed as it
returns from a LIFT experiment flight. NASA Photo EC05-0028-18 by
Small-scale divoting occurs when the adhesive on the external
tank thermal protection system (TPS) foam fails. This occurs as a
result of decreasing atmospheric pressure combined with increased
heating during Shuttle ascent causing air trapped beneath the TPS
LIFT project manager Stephen Corda said objectives of the
current flight tests on the F-15B include determining divot
structural survivability and stability in flight and quantifying
divot trajectories using videography. The flight data of divot
trajectories may also be used for Computational Fluid Dynamic code
"We're using the unique capabilities of the supersonic F-15B
aircraft and the aerodynamic flight test fixture to provide a means
to eject these debris or divots from the fixture, and then
photograph them with a high-speed digital video system, where we're
able to video these divots in flight at up to 10,000 frames per
second," Corda noted.
NASA' s Space Shuttle Systems Engineering and Integration office
at the Johnson Space Center (JSC) in Houston, Texas, is funding the
LIFT flight tests at NASA Dryden as part of the Space Shuttle
Return-to-Flight effort. JSC aeroscience engineer Ricardo Machin
said the current LIFT flight tests will help them validate the
models that they use for debris transport analysis.
"In particular, it's going to help us understand whether the
divots break up once they come off the external tank, and secondly
whether they will trim and begin to fly, or if they'll tumble. The
difference between trimming and flying makes a huge difference in
the amount of kinetic energy that this piece of debris can impart
to the shuttle," Machin said.
Image Left: A post-flight inspection of the panels on the
F-15B's flight test fixture shows all six divots of TPS foam were
successfully ejected during the LIFT experiment. NASA Photo
EC05-0030-04 by Tony Landis.
The LIFT flight test requires two new capabilities: an in-flight
foam divot ejection system, and a high-speed video system to track
and record the trajectories of the divots in flight. Both
capabilities were developed by Dryden engineers in just over two
Dryden's LIFT team designed, fabricated, and ground-tested four
different divot ejection systems, completing 70 ground tests to
determine and refine the best approach. NASA Dryden engineers also
designed and procured the very high-speed digital video equipment,
including development of a system to synchronize the cameras with
the divot ejection system. In addition, they developed videography
analysis techniques in order to quantify divot trajectories.