Stranded in space? Japan's space lab too roomy

The new Japanese laboratory on the International Space Station has one drawback: It's so spacious that astronauts floating in the middle of the room can get stranded, space shuttle Discovery's commander said on Friday.

"You have to be a little extra careful," commander Mark Kelly said during an inflight interview. "You can get out in the middle of it and you can't reach a handrail and you could possibly get stuck there for a little while."

When moving around in the weightlessness of space and the cramped confines of the space station, astronauts usually use handholds to pull themselves along or push off stationary objects and float a short distance to a new location.

The $1 billion Kibo lab, which was installed on Tuesday, is the largest component of the space station at 37 feet (11 metres) long and just over 14 feet (4.3 metres) wide.

Kelly said he and his crew, which delivered the Kibo laboratory during Discovery's ongoing mission to the space station, don't have much time for orbital antics.

The astronauts, who have been aboard since Monday, have conducted two spacewalks to install and outfit Kibo, and tackled a list of chores to help maintain and upgrade the $100 billion orbital outpost.

Kibo's storage room, which was delivered during the last shuttle mission in March, was due to be moved to its permanent hub on top of Kibo. A final spacewalk to work on the station's cooling system was planned for Sunday.

The work is not without its rewards.

"As a kid I used to dream of what it would be like to fly around like Superman," Kelly said. "That's one thing you can do here. ... You got to be careful because it's easy to get out of control. You can actually hurt yourself if you went too fast. But it's fun."