(Adds percentage of space added, paragraph 5, new task, paragraph 8)

By Irene Klotz

CAPE CANAVERAL, Fla., Oct 26 (Reuters) - The shuttle Discovery astronauts added a room to the International Space Station on Friday, extending the orbital outpost so Europe and Japanese laboratories can be linked in as well.

The work, one of the primary jobs of the shuttle's 14-day mission, began with veteran spacewalker Scott Parazynski and rookie Douglas Wheelock slipping outside the space station's Quest airlock to prepare the module for installation.

Robot arm operators working inside the station's Destiny laboratory fished out the 31,500-pound (14,200-kg) Harmony module from the shuttle's cargo bay and hoisted it over the side of the shuttle and into a temporary position on the station's Unity connecting node.

Unity connects the Russian and American segments of the station.

Space station astronauts will reposition Harmony, which boosts the station's living space by 18 percent, to its permanent spot after the shuttle leaves the outpost on Nov. 4. The module, which has six attachment ports for future station expansion, needs to be where the shuttle is now docked.

"I don't know that anybody ever told our crew that we bring harmony with us, but we sure bring fun," joked Discovery commander Pamela Melroy as Parazynski and Wheelock relaxed in the airlock after finishing the first of five spacewalks planned during the shuttle's visit.

Before placing the Harmony connecting node onto the station, the spacewalkers worked on a massive solar power structure that will be repositioned during spacewalks on Sunday and Tuesday. They also retrieved a broken antenna that will be refurbished on Earth and returned to the station as a spare.

During Sunday's outing, the spacewalkers will inspect a huge rotary joint that spins a pair of the station's solar power panels to face the sun. Engineers have noticed a vibration and want to know if anything is physically interfering with the gear.

SUNRISE IN SPACE

At times during the space walk, the views of Earth spinning 212 miles (340 km) below and the wide horizons of space were too dramatic to be ignored.

"Beautiful sunrise coming," Parazynski told his partner, who gasped as he looked up from his work.

"You just can't recreate that color blue on Earth. I don't know why," Parazynski mused.

Later, the men enjoyed a bird's-eye view of Harmony being eased into its berthing port on the station.

"Hey Wheels, look down," Parazynski told Wheelock. "They've got the node about two meters out."

"Oh, my goodness," replied Wheelock.

"Isn't that great?" Parazynski said.

The men finished their jobs ahead of time and were back in the station's airlock about an hour early to begin decontamination procedures. Parazynski saw a few crystals of ammonia coolant leak out as he disconnected plumbing to prepare the solar power tower for its relocation.

Wheelock checked his partner's suit for contaminants and found none, but NASA wanted to perform the airlock purge as a precaution.

"We'll have you sit there quietly while the roast is baking," joked crewmate Paolo Nespoli, the European Space Agency astronaut who supervised Parazynski and Wheelock during their spacewalk.

Discovery's mission will pave the way for the arrival of Europe's Columbus laboratory to the station in December, followed by three missions to install the Japanese space agency's Kibo complex.

NASA plans 11 more construction flights to the outpost and two resupply missions, as well as a final servicing call to the Hubble Space Telescope, before retiring the shuttle fleet in 2010.

Discovery, which blasted off on Tuesday from the Kennedy Space Center in Florida, is due back on Earth on Nov. 6.

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