In this handout photo provided by NASA, The Space Shuttle Endeavour's payload bay is seen, as it was photographed by one of the Expedition 15 crewmembers aboard the International Space Station on Friday.
In this handout photo provided by NASA, The Space Shuttle Endeavour's payload bay is seen, as it was photographed by one of the Expedition 15 crewmembers aboard the International Space Station on Friday. NASA/Getty Images
In this handout photo provided by NASA, a close-up view of damaged tile on the underside of the Space Shuttle Endeavour.
In this handout photo provided by NASA, a close-up view of damaged tile on the underside of the Space Shuttle Endeavour. NASA/Getty Images
A NASA team of engineers and astronauts on Tuesday were trying to decide if a spacewalk is needed to repair a deep gouge in the Space Shuttle Endeavour's belly that the space agency says is not a danger for reentry.
A decision was expected by Wednesday from the specialists assembled to consider if the crew needed to fix the 3 ½ inch by 2 inch gouge to avoid extensive post-flight repairs.
The damage is relatively small and the will not pose a hazard for Endeavour to fly safely home. But part of it penetrates through the protective thermal tiles, leaving just a thin layer of coated felt over the space shuttle's aluminum frame to keep out the more than 2,000-degree heat of re-entry.
To patch the damaged area, spacewalking astronauts would have to perch on the end of the shuttle's 100-foot robotic arm and extension boom, be maneuvered under the spacecraft, and either apply protective black paint or squirt in a caulk-like goop.
Mission Control told the crew late Monday that officials had ruled out a third repair technique involving a protective plate that could be screwed over the damage.
All three techniques were developed following the catastrophic reentry of Columbia in 2003, and NASA has never attempted this type of repair on an orbiting shuttle. Only the black paint has been tested in space.
Astronauts Rick Mastracchio and Dave Williams have trained extensively on the ground and could perform any necessary repairs during the mission's fourth spacewalk set for Friday. Their last tile-repair class was just three or four weeks before launch.
"I think that regardless of what repair method is chosen over the next day or so, we could execute it if required," said John Shannon, chairman of the mission management team.
Covering the exposed white coated felt with black protective paint would keep heat from building up in the cavity, Shannon said.
For extra heat protection, the astronauts could also squirt in the caulk-like goop from a tank attached to their spacesuit's backpack. In that case, they would apply the paint first to make sure the goop stuck.
If the repairs are ordered, astronauts on the ground will practice repairing a replica of the gouge underwater so they can create precise instructions for the spacewalkers and their crewmates.
When an astronaut from the shuttle Atlantis' June mission had to staple up a thermal blanket that had peeled back during launch, the ground crew sent him 60 pages of instructions and four videos, Shannon said.
Mastracchio and Williams have already completed two spacewalks in three days. On Monday, they removed a 600-plus-pound gyroscope from the space station's exterior that failed last October. They installed a new one in its place that was carried up aboard Endeavour. The space station has four gyroscopes to keep it steady and pointed in the right direction.
Teacher-astronaut Barbara Morgan - Christa McAuliffe's backup for Challenger's doomed mission in 1986 - helped monitor the spacewalk from inside the joined shuttle-station complex.
From NPR reports and The Associated Press