|Volume: 03, Issue: 04||02/23/2005|
Shuttle Moving Safely toward Return to FlightNASA scientists aren’t taking any chances when it comes to returning the Space Shuttles to flight. The agency has adjusted the targeted launch date for STS-114, the Return to Flight mission, and has continued extensive testing and processing to ensure that the tragic loss of Space Shuttle Columbia is not repeated in the future.
NASA managers have refined the targeted launch window for STS-114. Discovery and its seven-member crew are now targeted to launch during a window that begins May 15 and ends June 3. The new window accommodates daylight launch attempts and ensures the most detailed and clear photography of the External Tank.
Discovery continues to undergo processing for STS-114 in the Orbiter Processing Facility (OPF) at Kennedy Space Center, Fla. KSC personnel have completed about 90 percent of the work scheduled for the orbiter. Meanwhile, preparations continue in the Vehicle Assembly Building for the attachment of the Solid Rocket Boosters to the External Tank, which is slated for no earlier than Feb. 25.
NASA engineers are also continuing to acquire data on how insulating foam debris behaves when shed from the Space Shuttle's external fuel tank during launch. NASA's Dryden Flight Research Center is conducting a series of flight tests of the debris, known as divots, as part of the Return to Flight team effort.
The Lifting Insulating Foam Trajectory (LIFT) flight test series at Dryden is using the research center's F-15B jet Research Testbed aircraft to test divots at speeds up to approximately twice the speed of sound (Mach 2).
Small divots pop off the external tank when the 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 to expand.
"We're using the unique capabilities of the supersonic F-15B and the aerodynamic flight test fixture to provide a means to eject these divots from the fixture. We record them with a high speed digital video system. We're able to record the divots in flight at up to 10,000 frames per second," said LIFT project manager Stephen Corda.
According to aeroscience engineer Ricardo Machin of NASA's Johnson Space Center, "The LIFT flight tests will help validate the models used 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 debris can impart to the Shuttle."
The LIFT flight test required 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 months.
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. They designed and procured the very high-speed digital video equipment, including development of a system to synchronize the cameras with the divot ejection system, and they developed videography analysis techniques to quantify divot trajectories.
For information about NASA's Return to Flight efforts on the Web, visit http://www.nasa.gov/returntoflight .
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