Col. Michael E. Fossum of the Air Force Reserve and Col. Ronald J. Garan Jr. of the Air Force took a space walk to unleash the laboratory, called Kibo -- Japanese for "hope" -- and then astronauts inside the station used a robotic arm to attach it to the station, The New York Times (NYSE:NYT) reported.

The lab is being built in three stages. The first part arrived in March and the final section will be brought up from Earth later, the newspaper said.

The astronauts also tested ways to clean a damaged part of the electrical system.

The space station crew will become plumbers Wednesday, trying to fix the station's toilet, which has had trouble with urine collection, the Times said.