Tension in Space on Discovery Astronauts' First Spacewalk

With the Earth spinning some 220 miles beneath them, two astronauts strolled from space shuttle Discovery -- and into the cold vacuum of space outside the International Space Station.

Tensions rose when their spacewalk -- anticipated to last about 6 1/2 hours -- was interrupted at the two-hour mark by a robotic work station that shut down in the orbiting lab. The astronauts operating the robot arm, with spacewalker Stephen Bowen perched on its end, rushed to another computer station in another room.

The station arm was stuck motionless for nearly half an hour, with Bowen stuck gripping a big, broken pump that needed to be moved.

He dared not let go.

Mission Control asked if he was comfortable.

"I'm fine as long as it's not too much longer?" Bowen radioed. "How much longer?"

Close, he was told. But it took several more minutes until the robot arm could come back to life. Finally, the operation resumed and Bowen carried the 780-pound (353-kilogram), 5-feet (2.74-meters)-by-4-feet pump over to its new location on the exterior of the space station. He got help from spacewalking partner Alvin Drew in latching the pump down.

The pair had already installed an extension cable, and wrapped up the walk with a lighthearted experiment to capture the vacuum of space in a small metal canister. The bottle will be displayed in Japan.

Stephen Bowen, a spacewalking veteran, was a last-minute addition to the visiting crew of shuttle Discovery. He's filling in for an astronaut who hurt himself in a bicycle crash last month. Alvin Drew, meanwhile, is now the world's 200th spacewalker. He's making his first spacewalk.

The two astronauts climbed through the Quest airlock at 10:46 a.m. EST (1618 GMT) -- about half an hour earlier than expected -- and returned early as well, sealing the ISS airlock at 5:17 p.m. EST.

Although Bowen is a latecomer to the STS-133 crew, he brings extensive spacewalking experience to the mission. He is a veteran of five prior spacewalks. [Inside and Out: The International Space Station]

The injured Kopra will stay involved in today's activities, however, by providing support to the spacewalkers from mission control at NASA's Johnson Space Center in Houston -- which woke the space shuttle Discovery and the International Space Station crews at 6:23 a.m. EST Monday morning with the song “Oh What a Beautiful Morning.”

Discovery, NASA's most traveled space shuttle, is making its final flight on this mission before being retired along with the rest of the shuttle fleet later this year. The 11-day mission will deliver a storage room and humanoid robot to the station.

All in a day's work

The first task for the spacewalkers was to install an extension cable between NASA's Unity and Tranquility nodes. This will provide access to a power source on the outside of the station once a new storage module, which Discovery delivered to the station, is robotically installed tomorrow (March 1). The cable will also act as a contingency power source for that area of the station if needed.

Bowen and Drew then moved one of the station cooling system's defunct pump modules that had been temporarily stowed on an attachment bracket on the station's exterior. The ammonia pump broke down in August, but two station residents at the time, Douglas Wheelock and Tracy Caldwell-Dyson, were able to replace it with a spare during a series of emergency spacewalks.

Bowen and Drew transfered the broken pump module to a separate storage platform adjacent to the Quest airlock. NASA is hoping to bring the module back to Earth on a future shuttle mission -- Atlantis' STS-135 flight scheduled to launch in June -- so that engineers can analyze the problem. In the meantime, it will remain stored on the station's exterior.

Upgrading the station

After the ammonia pump was completely secured to the storage platform, Drew removed two tool bags that had been left outside during the spacewalks to repair the station's failed cooling system. The bags contain tools that will be used to vent any leftover ammonia inside the pump during the mission's second spacewalk on Wednesday.

Bowen and Drew then installed a wedge under a camera on the station's truss that will tilt the camera to allow for better access when a spare part is installed in the area on a future mission.

The spacewalkers wrapped their mission by replacing a piece of track for the rail cart system that is used to move cargo along the station's backbone-like truss. Finally, once all those tasks were complete, Drew completed an experiment, called "message in a bottle" for Japan's space agency (JAXA). For this task, he captured some of the vacuum of space in a bottle to return to Earth.

The Associated Press and Space.com contributed to this story.