Options for Leading Edge Repair
There is still concern that insulating foam and ice from the External Tank may shed and hit the Shuttle wing's leading edge causing damage. Langley is helping to explore possible on-orbit repair methods to prevent heat from penetrating the surface coating and reaching the skin of the wing leading edge. These methods make use of carbon-silicon carbide, a material that resists heat and has even greater strength than the leading edge material. These repair methods may also be applicable to tile repair.
Image above: This reinforced carbon-carbon plug repair concept uses flexible seven-inch plates to plug holes up to four inches. Credit: NASA
Langley led the development of a contingency repair tool that will fly on Discovery. One of the astronauts will demonstrate how the "plug" concept, designed for repair of the wing leading edge, could be assembled in the weightlessness of space. The plug uses flexible seven-inch circular carbon-silicon carbide plates to plug holes up to four inches. The plug attaches to the internal structure of the wing at the damage site, much like a picture hanger that -- once through the hole -- spreads and clings to the inside of the wall.
Several plug plates, in different shapes to fit different panel curvatures, are also aboard Discovery, in case there is a problem and mission managers elect to send an astronaut to the wing leading edge for a repair attempt. On STS-121, the plug concept is scheduled for demonstration on a wing leading edge panel fitted to a test rig in the cargo bay of Atlantis.
Additional Langley repair concepts are being readied for demonstrations on Shuttle flights in 2006. The "small area repair" concept covers a smaller hole or crack with a pre-formed patch and is planned to be flown on STS-115. The "tile area repair" concept uses patches to repair tile damage and is planned to be flown on STS- 116. The "large area repair" concept which, can repair holes up to 16 inches on the wing leading edge, is planned to be flown on STS-117.