Discovery Crew Prepares For Unprecedented Spacewalk

Today's a day of putting away supplies for the crew of the space shuttle Discovery, along with preparations for tomorrow's spacewalk, which will include a newly scheduled and risky repair job.

Analysis showed that protrusions in two areas could produce excessive heat during re-entry and threaten the spacecraft.  NASA managers decided yesterday to remove two strips of fabric filler that are dangling from the shuttle's belly.

It's a risky maneuver but a NASA manager says it's one that has to be done.

During Wednesday's planned spacewalk, astronaut Steve Robinson will be dangled from a robotic arm on the international space station and maneuvered to the bottom of Discovery to remove  the gap fillers. Gap fillers are thin fabric stiffened with a ceramic material and used to plug gaps between the shuttle's tiles. One keeps tiles from vibrating against each other during liftoff and has no purpose for re-entry. The other is designed to prevent repeated overheating of a gap between two tiles.

However, not having it in place during a single re-entry would still be "well within our safety margins," NASA's deputy shuttle program manager Wayne Hale said.

If he cannot pull the gap fillers loose, Robinson will use a tool to cut them flush, or nearly flush, with the tiles, so they don't interfere with the shuttle's aerodynamic flow during re-entry to Earth's atmosphere, Hale said. Discovery can return safely without either of the gap fillers in place, Hale said.

While the protrusions might not pose any threat to Discovery, NASA acknowledges that "large uncertainty" concerning their potential effect prompted the agency to take action. "

During the procedure, scheduled to last 90 minutes, Robinson will only be visible to the other members of Discovery via a camera on the space shuttle's boom. A second astronaut, Soichi Noguchi, will be spacewalking at the same time, but he will be working on other tasks -- among them, installation of an external storage platform on the space station.

Earlier Monday, the pair completed their second spacewalk of the mission, replacing a faulty gyroscope on the space station.