(AP) -- Two astronauts stepped out on a spacewalk to install a new tank of space station coolant Thursday as a large piece of orbiting junk headed their way.
The old rocket part was expected to pass within two miles of the shuttle-station complex late Friday morning, considered a safe distance by NASA specialists. Managers decided there was no need to move the linked spacecraft out of the way and proceeded with the spacewalk as planned.
Danny Olivas and Christer Fuglesang were nearly an hour late heading out the hatch because of minor spacesuit problems. It was the second spacewalk in three days for the Discovery and space station crews.
Their main job 220 miles up was to collect the new fully loaded ammonia tank from Discovery and hook it up to the space station. The old tank, launched seven years ago, was removed during Tuesday night's spacewalk. It will be returned to Earth next week aboard Discovery.
The tanks are big and awkward for spacewalkers to handle: nearly 5 feet long, 7 feet wide and 4 feet high. The new one weighs 1,700 pounds.
Both men are experienced spacewalkers. Fuglesang is Swedish.
At one point Wednesday, NASA considered moving Discovery and the space station into another orbit because of the space junk, and possibly even delaying this spacewalk. But by Thursday morning, the track of the debris became clearer and experts were able to say with certainty that the two spacecraft and 13 astronauts were safe where they were.
A third and final spacewalk is scheduled for Saturday.
Discovery is scheduled to undock from the space station Tuesday.
©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Explore further: Astronauts get Sunday morning off after busy week