Astronauts complete heat shield repair tests
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: July 30, 2005
Working the shuttle Discovery's cargo bay, astronauts Stephen Robinson and Soichi Noguchi tested potential heat-shield repair techniques today, a major milestone in NASA's recovery from the Columbia disaster.
Using a high-tech caulk gun, Robinson squeezed out dollops of a thick heat-resistant material known as NOAX and used trowels to work it into deliberately cracked and gouged samples of wing leading edge material. Multiple layers were applied and smoothed over the damage sites to build-up enough material to resist the heat of re-entry. The samples will be subjected to a battery of tests on Earth to find out how well the repairs might work in an actual re-entry.
"It seems to be well behaved," Robinson said of the thick goop. "I see just a very little bit of bubbling. ... It's about like pizza dough. Licorice-flavored pizza dough."
Noguchi floated nearby, using a toweled glove to clean the tip of the applicator and a variety of trowels.
"I would recommend if we were to do this for real to use lots of spatulas," Robinson said. "You can't clean it."
Because of time constraints, Robinson was told to skip one crack repair demonstration that engineers had planned to test in a high-temperature furnace back on the ground.
Noguchi then took center stage, using a different applicator to apply a dark "emittance wash" material to deliberately damaged heat-shield tiles. The material could prove useful fixing tiles with coating damage, improving their ability to reject heat.
"The idea of emittence wash is to apply a coat of a thick kind of dark gray paint to replace areas where the black tile coating has been cracked and removed," said Lora Bailey, a spacewalk planner at the Johnson Space Center. "Originally, it was intended for certain types of damages. However, the true extent of its use is being evaluated carefully by analysis and tests to determine the depth of damage that you can repair and also that is dependent on where the damage is on the vehicle."
Today's tests were completed about two-and-a-half hours into the planned six-and-a-half hour spacewalk.
"Everyone's smiling, great job," mission control radioed.
The astronauts now are pressing ahead with work to mount an attachment fitting to the space station's Quest airlock module where a large tool kit and spare parts box will be mounted during a spacewalk next week.
See the Status Center for full play-by-play coverage.