Discovery crew plans heat-shield repair demo

NASA is planning to add a fifth spacewalk to shuttle Discovery's upcoming mission so astronauts can practice repairing the type of heat-shield damage done to Endeavour on a flight last month.

Discovery mission specialists Scott Parazynski and Douglas Wheelock aim to use a device similar to a caulk gun to repair thermal tile samples that have been deliberately damaged.

NASA engineers developed the Tile Repair Ablator Dispenser, or T-RAD, as part of a post-Columbia effort to give astronauts a way to repair damage to the thousands of thermal tiles that line the underside of the shuttle orbiter. The device is designed to extrude a putty like material to fill dents and gouges in the fragile tiles. Also known as the "goo gun," it has never been tested in space.

The development of heat-shield repair tools and techniques was one of the major recommendations made by the Columbia Accident Investigation Board.

NASA had planned to test the device on a mission next year. Plans to move up the spacewalk demo were laid after a chunk of foam the size of a baseball dug a deep gouge in tiles on Endeavour last month.

NASA managers considered using the T-RAD device to repair the tiles, but ground tests and engineering analyses showed the shuttle would come through atmospheric reentry without significant damage. The analyses proved correct.

A special stowage bin for the "goo-gun" and tile samples was installed in the cargo bay of Discovery earlier this week. The shuttle's payload bay doors, which already had been closed for flight, were reopened so the Tool Stowage Assembly could be attached to the starboard sidewall of the orbiter.

Kyle Herring, a spokesman for NASA's Johnson Space Center, said the extra spacewalk is expected to be officially added to the mission during a joint meeting next Monday between managers of the shuttle and International Space Station programs.

It will lengthen the upcoming mission to 13 days rather than 12 and will equal the greatest number of spacewalks ever carried out on a shuttle flight. The only other missions to feature five spacewalks have been Hubble Space Telescope servicing flights.

One of the spacewalks to be done on Discovery's stay at the station will be carried out by outpost commander Peggy Whitson and flight engineer Yuri Malenchenko rather than the shuttle crew.

Discovery is scheduled to launch Oct. 23 with the U.S. Harmony module, which will serve as the gateway to still-to-be-launched European and Japanese science laboratories.

The orbiter is slated to roll over to the Kennedy Space Center Vehicle Assembly Building from Bay No. 3 of the Orbiter Processing Facility on Sept. 19. The fully assembled shuttle is scheduled to roll out to launch pad 39A on Sept. 27.

IMAGE NOTE: Click to enlarge the photo of the orbiter Discovery in Bay No. 3 of the Orbiter Processing Facility at Kennedy Space Center. Photo credit: Jim Grossmann.