Contractors seek solutions to thermal protection system after Discovery’s return

Changes expected following Space Shuttle Discovery’s STS 114 return-to-flight mission will involve thermal protection system (TPS) processing, future external tank (ET) instrumentation and the removal of its protuberance air load (PAL) ramp.

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NASA astronaut Stephen Robin­son had to remove gap filler pro­truding from Discovery’s TPS during the July-August mission and the PAL foam ramp that came off during launch led to the Shuttle fleet being grounded again.

A slightly larger piece of foam fatally damaged Space Shuttle Columbia. Long-term solutions for the ET foam and TPS issues are being addressed by Space Shuttle contractors.

“We are looking at several different solutions to the foam shedding,” says Tom Marsh, vice-president for Lockheed Martin Space Systems, which supplies the external tank. “It might be possible to remove this ramp for future flights and we are looking at putting curves on certain areas.”

Marsh says the ET could be instrumented for future missions to provide more data. Such instrumentation could also make it easier to decide whether to remove the ramp, which was put in to smooth out airflow and reduce turbulence.

Boeing, which provides the orbiter, is looking at the TPS maintenance processes and a more robust tile material. It wants to ensure gap filler will not protrude in future and is examining the candidate tile material PRI-18 to protect vulnerable areas such as the main landing gear doors.

Hurricane Katrina has forced the NASA assembly facility at Michoud, New Orleans, to close and ET work for the next Shuttle mission is on hold. NASA is trying to decide whether it can work instead on an external tank for mission STS 121, still expected in March, at Kennedy Space Center, Florida.



Source: Flight International