NASA mission managers were relieved to see that a method of repairing damaged heat shield tiles in orbit was working as expected. Astronauts aboard the International Space Station performed a six-and-a-half hour spacewalk during which they tested a special foam dispenser and the technique to repair holes in the space shuttle's vital heat shield.

"Endeavour, we are absolutely captivated by what you guys are doing here," said astronaut Steve Robinson from Mission Control to the space shuttle. "It's like brain surgeons up there."

Atronauts Michael Foreman and Robert Behnken squeezed out a special goo-like material into damaged test tiles and then flattened the composite material with a special brush. Everything worked as expected, to their great relief. NASA engineers will take another look at the tiles when the space shuttle comes back to Earth. The shuttle's high-speed re-entry into our planet's atmosphere generates temperatures up to 1,500 degrees Celsius on some of the thermal tiles that line its underbelly.

The primary purpose of the detailed test objective was to evaluate the Shuttle Tile Ablator-54 (STA-54) material and a tile repair ablator dispenser in a microgravity and vacuum environment for their use as a space shuttle thermal protection system repair technique. Spacewalkers Robert Behnken and Mike Foreman have performed the test on the outside of the Destiny lab.

"I'm thrilled with what we saw today. The results based on testing we saw on the ground, we did a lot of testing in the vacuum chamber, the proof will come when the get this material back to the ground and cross section it, but, yes, it is behaving the way we expect it to behave but we have a lot of testing behind it," said space station flight director Dana Weigel.

The two also fixed a broken circuit breaker but failed to remove a power connector from the truss. It was vital to complete this tile repair test before space shuttle Atlantis flies to the Hubble Space Telescope in August. Unlike missions to the space station, Atlantis’ crew members wouldn’t be able to wait on the station for another shuttle to bring them home if Atlantis was damaged.