Space shuttle tile repair training. NASA astronaut Rex J. Walheim training in the repair of the thermal tiles used on the US space shuttles. He is using a tool similar to a putty knife, to smooth the repair material (orange). The training is taking place in free-fall on a flight of a KC-135 aircraft. Thermal tiles are used on space shuttles to protect them from the heat of re-entry into Earth's atmosphere. Following the break-up of the shuttle Columbia during re-entry in February 2003, due to damage to its thermal tiles, the space shuttles are examined in orbit after each launch. Several in-flight repairs have taken place since the space shuttles resumed service. Photographed on 8 August 2003.