NASA is trying to decide whether to send astronauts on a space walk to repair a small gash on the belly of Space Shuttle Endeavour.
A chunk of insulating foam from the shuttle's fuel tank apparently hit the orbiter at liftoff last week, creating a 3 1/2-inch-long gouge that penetrates all the way through the thermal shielding on the shuttle's underside.
A team of astronauts, including former teacher Barbara Morgan, spent yesterday working with a robotic arm, to get scanning equipment up close to the damaged tiles. They sent photos and 3-D images back to Earth for analysis.
NASA officials have worried about this scenario ever since Space Shuttle Columbia burned up during re-entry in 2003 after suffering similar damage. On Columbia, the full extent of the damage caused to the heat shielding by a similar chunk of foam was not known until after the disaster. That's why NASA now does inspections, like the one that found the gash on Endeavour.
Engineers are trying to determine whether the marred area can withstand the searing heat of atmospheric re-entry at flight's end.
The damaged thermal tiles are located near the right main landing gear door. The area, which is right beneath the aluminum framework for the right wing, is subjected to as much as 2,300 degrees Fahrenheit during re-entry.
"This is the kind of damage that we have spent several years since Columbia developing our analysis tools to be able to model, so I think we'll have it very well understood sometime early this week," said John Shannon, who chairs NASA's mission management team.
He said NASA engineers will reproduce the damage on a panel of tiles, and test them in a facility that simulates the extreme heat of re-entry.
"This is something we would rather not deal with but we have really prepared for exactly this case," Shannon said.
Meanwhile, two spacewalking astronauts replaced equipment on the international space station, a six-hour effort to replace one of the gyroscopes that help control the station's orientation.
Astronauts Dave Williams and Rick Mastracchio carefully unbolted the broken gyroscope from a space station truss and swung the more than 600-pound piece of equipment onto a temporary storage platform. Then Williams latched himself onto the station's robotic arm for a ride to the shuttle's cargo bay, where he retrieved the new replacement gyroscope.
"This is the most amazing ride I've ever had," Williams said.
After struggling a bit to loosen the bolts that attached the new gyroscope to its storage container, the astronauts got it free and installed it on the truss. Later, they planned to move the broken equipment to a spot where it will be stored for a few months until another shuttle can bring it back to Earth.
Endeavour's crew plans to conduct two more spacewalks on Wednesday and Friday, and they could add the gouge repairs to their to-do list. Depending on the extent of the damage, astronauts can slap on protective paint, screw on a shielding panel, or squirt in filler goo.
Endeavour has been docked at the space station since Friday. It will remain there until Aug. 20 for a record 10-day stay. Mission managers on Sunday approved the prolonged visit based on the successful testing of a new power transfer system flying on Endeavour. The system is drawing power from the station and converting it for use aboard the shuttle.
From NPR reports and The Associated Press