Space walkers use high-tech putty in test repairs

Two spacewalking astronauts pulled out a caulk gun and high-tech putty and tested a method for patching shuttle thermal tiles.

Two spacewalking astronauts pulled out a caulk gun and high-tech putty and tested a method for patching shuttle thermal tiles. It was the fourth spacewalk since Endeavour arrived at the international space station just over a week ago to deliver a robot and the first section of a Japanese lab.

The long-awaited repair test on Thursday night was ordered following the 2003 Columbia tragedy in which the shuttle exploded on its return after its wing was gashed at lift off by a chunk of fuel-tank insulating foam.

Astronaut Michael Foreman— ‘Mr Goo’ — squeezed the

salmon-colored material from the caulk gun-like dispenser and filled holes in deliberately damaged tile samples that were carried up aboard Endeavour. He used a small foam brush to tap down and smooth the putty, but small bubbles kept popping up.

His spacewalking partner, Robert Behnken, floated nearby, wiping excess putty from the nozzle of the caulk gun. Even more of a mystery than how the caulk gun would work was how the goo would behave. Engineers were curious about whether bubbles would form and rise to the top as they do on Earth or whether any bubbles would remain inside the material and cause it to swell. This so-called rising bread-loaf effect could jeopardise a repair and endanger a crew during re-entry. Flight director Mike Moses said the test would give NASA “that extra confidence boost” if astronauts ever have to use the repair method for real. The goo-filled tile samples will be returned to Earth aboard Endeavour for analysis.