CAPE CANAVERAL, Fla. -- As part of NASA's return to flight effort, shuttle engineers are figuring out the best way to repair damaged heat protection tiles while the orbiter still is in space.

One idea is to send spacewalking astronauts outside to apply a material with a trowel and fill in any damaged areas.

In order to test how well the material can be laid in place, the tools to be used and the procedures involved, crewmembers are flying in NASA's KC-135 aircraft, which is capable of providing brief periods of weightlessness.

In this recent image an unidentified crewmember uses a large flat trowel to remove excess material from a membrane-covered cavity on a damaged section of thermal tiles, while flying aboard the aircraft that is affectionately known as the Vomit Comet.

Credit: NASA