Two U.S. space shuttle astronauts floated out of the International Space Station Friday for the third and last time of their mission to finish work on a new station solar array and other maintenance chores. The crewmembers found some unfriendly bolts.
Shuttle Atlantis astronauts Heidimarie Stefanyshyn-Piper and Joe Tanner ventured out of the space station tethered to the outpost in their bulky spacesuits to face another six-and-a-half hours of work in the void.
Like any home handymen, they found again that maintenance tasks can take longer than expected because of the uncertainties of equipment.
The spacewalk was delayed 45 minutes when an overloaded station circuit shut down, stopping a pump used to depressurize the foyer from which the crewmembers were waiting to exit.
Once flight controllers solved that problem, the astronauts were on their way. Their main task was to deploy a radiator on the station's new solar energy panels, which were unfurled Thursday to double the outpost's power. The radiator will help cool the research complex.
But shuttle flight director John McCullough says the pair hit another snag while replacing an antenna that had deteriorated in the high radiation levels of the space environment. They had trouble unfastening bolts and making connections.
"Any time your are messing with bolts and connectors, the days tend to be challenging, especially ones that have been in orbit for as long as these have," he said.
The stuck connectors were not the first bolts to be a problem during Atlantis' supply mission to the outpost. On the two previous spacewalks, bolts either floated away before the spacewalkers could capture them or proved balky enough to cause one crewman to break his wrench. Mission directors say the escaped bolts pose no hazard to the space station.
The spacewalk supervisor, John Haensly, says Friday's bolt difficulties forced the cancellation of another minor maintenance task, but he adds that he is satisfied with the outing, which he calls an EVA, the space agency abbreviation for Extra Vehicular Activity.
"They overcame some minor obstacles, but we got everything done," he said.
The Atlantis crew enjoys a half-day off from work on Saturday before resuming equipment and supply transfers to the space station. The station crew is preparing for the arrival of their replacements on a Russian Soyuz rocket Wednesday, the day Atlantis returns to Earth.