CAPE CANAVERAL, Fla. -- Two spacewalking astronauts resumed construction on the International Space Station yesterday for the first time in more than 3 1/2 years, and NASA pronounced the outing a success, even though a small bolt floated away.
``I felt today like this is what NASA is supposed to do," said lead space station flight director John McCullough. ``This is what we're here to do."
The spacewalk to attach a new 17 1/2-ton box-like truss section included the connecting of 13 wires or tubes and the tightening or loosening of 167 bolts.
NASA managers downplayed an astronaut's concern about the 1 1/2-inch bolt that came free.
Astronaut Joe Tanner was working with the bolt, which had an attached spring, when the washer holding it in fell off. The bolt and spring floated over the head of astronaut Heidemarie Stefanyshyn-Piper and skittered across the truss.
While the washer went out into space safely, Tanner worried the bolt and spring could get into the truss's wiring and tubing and cause problems.
``I just hope that bolt is on its way to Mother Earth right now and not on its way" to a crucial joint in the addition, Tanner said.
Even though NASA didn't have any video showing the bolt missing the mechanism, managers at an afternoon news conference said they are certain that the bolt flew off into space harmlessly.
Space debris can be dangerous if it punctures space station walls or spacesuits and can jam crucial mechanisms. However, spacewalkers have a long history of losing material in space. In July, Discovery spacewalkers lost a 14-inch spatula that floated away.
The free-flying bolt marred an otherwise successful six-hour, 26-minute spacewalk yesterday morning. Two more spacewalks are planned for later this week.
``You did a phenomenal job and set the bar very high for the rest of the assembly," Mission Control told the crew when the spacewalk ended late yesterday morning.
Wearing bulky suits and gloves, Tanner and Stefanyshyn-Piper zipped through a list of arduous but mundane construction tasks, putting NASA ahead of schedule in connecting the addition. With extra time, Mission Control assigned them eight extra jobs of bolt removing and cover unlatching that would have been part of a spacewalk tomorrow.
Atlantis astronauts Daniel Burbank and Steve MacLean will head into space today.
The spacewalk was a first for rookie astronaut Stefanyshyn- Piper, who joined an elite club of female spacewalkers.
Only six other women have participated in any of the 159 U S spacewalks, and only one has gone on any of the 118 Russian spacewalks. A major reason is that spacesuits are too big for most women, said Stefanyshyn-Piper, who is 5 foot 10 inches tall. ``If you fit in a suit, then the easier it is to work," she said.
The 45-foot, $372 million addition includes two electricity-generating solar arrays that will be unfurled tomorrow.