"What a view," said Soichi Noguchi as he emerged from the linked shuttle and international space station about 222 miles over central Asia.
"There are just no words to describe how cool this is," Robinson later said while riding the space station's robotic arm to connect a device needed for the installation of a storage platform next week.
The astronauts worked side-by-side in Discovery's open cargo bay, testing the repair methods on a variety of deliberately damaged tile and carbon samples brought to space. It took up nearly half of the six-hour, 50-minute spacewalk.
Robinson and Noguchi, a Japanese astronaut, worked with tools similar to an oversized caulk gun and large putty knives to apply an experimental material to the sample tiles that NASA hopes can be used in future missions to repair cracks in the delicate carbon panels lining the shuttle's wings.
The astronauts rearranged their schedule to perform the repairs while temperatures outside the shuttle were ideal for the experiment. Temperatures change very quickly; if they are in the sun, it can be up to 250 degrees Fahrenheit. When it's dark, it can be 250 degrees below.
"No bubbling at all. It's behaving very nicely," Robinson said of the experimental material as he applied it with the specialized gun. During another application, he noted a little bubbling. "It's gluey stuff so it's a little hard to get off."
The experimental material can be used to repair cracks or coating loss up to four inches long, but won't work on holes such as the one blown into Columbia's left wing by a 1.67 pound chunk of foam in 2003. All seven astronauts aboard that shuttle died.
In certain areas of the wing, NASA says cracks or coating damage measuring 2 inches long and .02 of an inch wide could doom the spacecraft.
NASA has developed a repair technique for holes in its carbon paneling, but that technique, which involves installing a patch over the hole and then bolting it inside the wing, will be tested inside Discovery later in the flight.
During their first spacewalk ever, Robinson and Noguchi also coated thermal tile samples with a caulk-like material in hopes of restoring the tiles' heat-rejecting ability, necessary for the shuttle to safely re-enter the Earth's atmosphere.
CBS Radio's Peter King reports this was an experiment. The astronauts have gone on record as saying they do not want to be test subjects for something that hasn't been proven so the samples will be brought back and lab tested to simulate the fiery shuttle reentry. If those tiles survive, this repair kit will be certified for future shuttle crews.
The sample tiles won't be tested for heat resistance until the astronauts return to Earth, but researchers want to see how well the mixture adheres in space and if there are any problems applying it in zero gravity.
"That works pretty well," Robinson said as Noguchi used a foam brush applicator on one of the sample tiles.
Before going back inside, the spacewalkers performed some space station repairs. They did a little rewiring to restore power to a gyroscope that stopped working four months ago because of a popped circuit breaker, replaced a broken global positioning antenna, and carried in a pair of experiment packages that had been mounted on the outpost's exterior.
"Great job. Everything was just perfect. Extra stuff got done," Mission Control radioed. "You guys get some rest."
Two more spacewalks are planned over the coming week.
NASA grounded future missions earlier this week after learning Discovery's external tank lost four sizable pieces of foam during Tuesday's liftoff. The foam pieces were bigger than the space agency wanted to see shed, and officials said despite years of tank redesign and the hundreds of millions of dollars spent more work is needed.
NASA officials have said Discovery appears to have sustained no major damage during launch and is scheduled to return to Earth on Aug. 7.
That date, however, could be pushed back a day so the shuttle's astronauts can spend another day working aboard the station and leaving its crew with additional supplies, such as surplus food, water and laptop computers.
NASA Administrator Michael Griffin said Friday that the agency may be able to launch another shuttle by year's end, but wants to do what it can for the station in case the fleet is grounded longer.