Astronauts finish longest spacewalk outside station

By Chris Baltimore

HOUSTON (Reuters) - Two shuttle Endeavour astronauts finished the longest of their planned spacewalks outside the orbiting International Space Station on Saturday, a nearly seven-hour effort aimed at cleaning and repairing a contaminated joint on the station's solar power array.

Heidemarie Stefanyshyn-Piper and Stephen Bowen returned to the station's Quest airlock at 7:58 p.m. EST/0058 GMT after spending six hours and 57 minutes working in the vacuum of space as the station sailed about 225 miles (362 km) over Earth.

Stefanyshyn-Piper and Bowen worked together inside a 10-foot-(3-meter-)wide rotary joint, one of two on the station that pivot the station's sprawling solar wings so they can face the sun for power.

One of the joints is contaminated with metal filings, which engineers believe stemmed from a lubrication problem. A total of four spacewalks are planned for the 11-day mission.

The repair involves greasing the joint's metal ring so the debris can be collected and scraped off.

NASA planned for both astronauts to use grease guns, but a set of tools, worth about $100,000, accidentally floated off into space during the mission's first spacewalk on Tuesday.

The astronauts shared a grease gun during that outing and then revised their cleanup procedures to use grease-impregnated wipes for later spacewalks.

As a backup, NASA had the astronauts modify one of two caulking guns, flying as part of an emergency shuttle heat shield repair kit, so that it could dispense grease.