CAPE CANAVERAL, Fla. – Spacewalking astronauts worked on the outdoor plumbing of the international space station Saturday, hooking up new air-conditioning lines and installing clamps to prevent pressure buildups.
It was the second spacewalk in three days for David Wolf and Piers Sellers, visiting from space shuttle Atlantis.
The men immediately encountered stiff joints in some of the space station’s older pipes, which contained ammonia coolant. What’s more, the areas were hard to reach.
With his long arms, Sellers managed to pry open the joints ever so slightly and install the specially designed, pressure-relief clamps.
“It is quite possible you’re the only person in the astronaut office who could have done that task,” Pamela Melroy said from inside the orbiting complex.
“I’m the second-longest armed,” Sellers replied. “The other guy, we know about him. He’s a primate for sure.”
NASA designed the clamps after ground testing uncovered a potential pressure problem in the ammonia lines of the new $390 million girder, which was delivered last week by Atlantis. Older equipment, already in orbit, also was found to have vulnerable joints.
Engineers feared that if ammonia leaked into the joints and pressure built up, the pipes might not twist apart if a component needed to be replaced in the future. So clamps were built to prevent increased pressure – and it was up to Wolf and Sellers to install almost 30 of them Saturday.
As expected, pressure had already built up in some of the older lines.
Wolf successfully snapped on his first clamp, after relieving the pressure. “I felt it burp,” he said. Sellers had more trouble. “I need another third hand, really,” he said.
Mission Control was “flabbergasted” when Wolf discovered some missing pieces in the older plumbing. “Really good work catching that,” Melroy told him.
Altogether, 100 clamps will need to be installed, with the job spread over three shuttle visits.
Besides making those repairs, Wolf and Sellers connected cooling-system lines for the new 14-ton girder, which has three radiators and two ammonia tanks.
They also released the brakes on the railcar that came up on the girder, along with a set of tracks. Future spacewalkers will use the railcar to travel the length of the framework as more girders – and more track – are added.
As they completed the railcar work, Wolf and Sellers broke into song in honor of the two women helping them from inside. It sounded something like “A Bicycle Built for Two” and drew cheers from Melroy and Sandra Magnus.
Just then, Melroy informed Sellers that they were flying over England, where he was born. “Oh, wow,” Sellers exclaimed. The views from the spacewalkers’ helmet cameras, showing the docked Atlantis, were just as stunning.
Fortunately, the space station’s robot arm worked fine as a work platform. The crane malfunctioned during Thursday’s excursion, and the astronauts had to lug and plug in a TV camera by hand. On Saturday, Wolf noticed a sheared bolt on the camera assembly.