Astronauts Heidemarie Stefanyshyn-Piper and Stephen Bowen were armed with grease guns, putty knives and oven-like terry cloth mitts to wipe away metal grit from the clogged joint.

It was the first of four spacewalks planned for space shuttle Endeavour's two-week visit to the space station; the astronauts also are making home improvements.

For more than a year, the jammed joint has been unable to automatically point the right-side solar wings toward the sun for maximum energy production. The repair work—expected to be greasy and hand-intensive—will take up much of all four spacewalks.

The joint is located near the extreme reaches of the 220-mile-high outpost. The spacewalkers had 85-foot safety tethers to keep them connected to the mother ship at all times.

NASA suspects a lack of lubrication caused the massive joint to break down; grinding parts left metal shavings everywhere and prompted flight controllers to use the joint sparingly. Besides scraping and wiping away the grit and applying grease, the spacewalkers will replace the bearings.

As a precaution, extra grease will be applied on a later spacewalk to the joint on the opposite side of the space station that has allowed those solar wings to produce ample electricity.

Before tackling the joint repairs, Stefanyshyn-Piper and Bowen had to get some relatively mundane work out of the way. First on their to-do list: collecting an empty nitrogen gas tank outside the space station and hauling it back to the docked shuttle for return to Earth. Then they had to move an ammonia hose coupler from the shuttle over to the station, storing it on a giant toolbox holding other spare parts.

Like other tasks on this mission, the astronauts began the spacewalk early.

"OK, let's go out," said Stefanyshyn-Piper, the first woman to serve as a lead spacewalker on a shuttle flight.

The spacewalk was expected to continue well into Tuesday evening.

As the action unfolded outside, the astronauts inside the shuttle-station complex started unloading the gear inside a huge trunk that was brought up by Endeavour.

The big-ticket item—and one of the first things to be hooked up—is a recycling system that will convert astronauts' urine and sweat into drinking water. It is essential if NASA is to double the size of the space station crew to six next June.

Endeavour also delivered an extra bathroom, kitchenette, two bedrooms, an exercise machine and refrigerator that will allow space station residents to enjoy cold drinks for the first time. Until now, they have had to settle for tepid or hot beverages.

The additions—coming exactly 10 years after the first space station piece was launched—will transform the place into a two-bath, two-kitchen, five-bedroom home.

Endeavour and its crew of seven arrived at the space station Sunday. The shuttle will remain docked through until at least Thanksgiving. The next spacewalk is set for Thursday.