Two spacewalking astronauts installed a new fully loaded tank of space station coolant on Thursday as a large piece of orbiting junk headed their way, just far enough away to pose no concern.

The old rocket part was expected to pass within two miles (3 kilometers) of the shuttle-station complex late Friday morning, considered a safe distance by NASA specialists. Managers decided there were no need to move the linked spacecraft out of the way and proceeded with the spacewalk as planned.

Danny Olivas and Christer Fuglesang, a Swede, 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.

Despite the late start, Olivas and Fuglesang quickly accomplished their main objective. They collected the new ammonia tank from Discovery, bolted it onto the space station, and then hooked up all the electrical and fluid lines. Mission Control praised their effort.

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 (1 1/2 meters) long, 7 feet (2 meters) wide and 4 feet (1.2 meters) high. The new one weighs 1,700 pounds (770 kilograms).

The men, both experienced spacewalkers, appeared to have no problem dealing with the tanks.

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.

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