(Adds end of second spacewalk, details)

By Chris Baltimore

HOUSTON, Nov 20 (Reuters) - Shuttle Endeavour astronauts working outside the orbiting International Space Station faced glitches during a second spacewalk on Thursday, as one astronaut experienced high carbon-dioxide levels after his crew mate lost a tool bag on the mission's first spacewalk.

Lead spacewalker Heidemarie Stefanyshyn-Piper and rookie astronaut Shane Kimbrough returned to the space station's Quest airlock at 7:43 p.m. EST (0043 GMT) after a 6-hour, 45-minute outing.

The astronauts' main job was to work on one of the space station's two rotary joints, which are needed to pivot solar wing panels to face the sun for power.

The astronauts had to share grease guns and other tools after Stefanyshyn-Piper's tool kit, which contained $100,000 worth of gear, floated away on Tuesday.

During Thursday's spacewalk, levels of carbon dioxide levels in Kimbrough's space suit rose above NASA's safety limit, prompting controllers to order him back to the airlock just as the spacewalk was ending.

"It didn't represent a drastic change to our plan," said John Ray, NASA's lead spacewalk officer. Kimbrough was not in any danger and did not report any adverse symptoms, Ray said.

It was the second of four spacewalks planned for the 15-day mission, which had to be reorganized after Stefanyshyn-Piper lost the grease gun.

During Thursday's spacewalk, she used pre-lubricated wipes to trap metal particles, and Kimbrough used the one remaining grease gun to work on the station's robot arm.

The shuttle arrived at the station on Sunday to work on the station's truss joints and deliver equipment needed to prepare the station for a permanent six-person crew.

Currently, rotating groups of three astronauts live on the station, which Thursday marked the 10th anniversary of the launch of its first module -- the U.S.-financed, Russian-built Zarya compartment.

NASA had planned to finish construction in eight years, but delays after the 2003 Columbia accident postponed the station's completion until 2010.

"We've had a number of significant issues to deal with on the ISS, and yet always a solution to those has been with our partners pulling together," said NASA's deputy space station program manager, Kirk Shireman.

The station, which orbits about 212 miles (340 km) above the planet, is a $100 billion project of 16 nations. Since the arrival of Zarya, it has completed more than 57,300 orbits of Earth and hosted 167 people -- including six tourists -- from 15 nations.

The ongoing shuttle mission is NASA's 27th shuttle flight to the space station, with eight more remaining before the shuttle fleet is retired in 2010. NASA also plans a final servicing call to the Hubble Space Telescope next year. (Additional reporting by Irene Klotz)

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