STS-126 mission specialists Heide Stefanyshyn-Piper and Shane Kimbrough completed the second of the mission's four spacewalks at 7:43 p.m. EST Thursday. The two astronauts relocated two crew and equipment translation aid carts, lubricated the Canadarm2 end effector, and continued cleaning and lubrication of the starboard solar alpha rotary joint.

The Endeavour arrived at the ISS on Sunday on a 15-day "home improvement" mission. It delivered 6,538 kilograms of supplies and equipment to upgrade the space station's living space and prepare it for more residents on longer-term assignments, after the retirement in 2010 of the US fleet of aging reusable orbiters.

The astronauts had hoped to run a test batch of urine through the contraption Thursday, but a caution alarm usually caused by combustion delayed those plans. Flight controllers believe it was a false alarm.

"These are the growing pains we expect to see," said flight director Ginger Kerrick. "These are very complicated pieces of equipment with very complicated software to control them."

On Friday, the shuttle and station crews will hold a new conference, which is scheduled for 3:05 p.m.

After that they will start to prepare the third spacewalk that is set to occur on Saturday at 1:45 p.m.

The third and longest spacewalk of the mission will be completely devoted to work on the starboard SARJ. The mission specialists assigned for this mission are Heide Stefanyshyn-Piper and Steve Bowen.

Bowen is the first submarine officer selected by NASA as an astronaut. He joined the astronaut corps in 2000 and served technical duties in the space station operations branch.

Stefanyshyn-Piper served as a mission specialist on STS-115, logging more than 12 days in space. She also completed two spacewalks on her first mission.

During the third spacewalk Piper will open covers 13 and 14, remove TBA one, clean and lubricate the area, install a new TBA and close the covers.

She will repeat the process on TBA two under covers 15 and 16 and TBA three under covers 17 and 18. Bowen will do the same for TBA four under covers 19 and 20, TBA six under covers 22 and one and TBA seven under covers two and three. He also will remove TBA five under cover 20; however, it was replaced on a previous spacewalk, so he will simply clean and re-install it.