News : Debris briefly forces astronauts from space station

By Irene Klotz

CAPE CANAVERAL, Florida (Reuters) - A tiny piece of space junk smaller than a fingertip forced three astronauts to briefly evacuate the International Space Station on Thursday when the debris came too close for comfort.

The astronauts, Russian Yury Lonchakov and Americans Michael Fincke and Sandra Magnus, spent about nine minutes in the Soyuz escape ship before the potentially destructive space litter passed by.

NASA called the threat to the $100 billion space station "minimal" and said the astronauts were moved into the Soyuz capsule as a precaution.

The debris was a "very tiny piece" -- about 1/3 of an inch long -- of an old "payload assist motor" that was previously on either a Delta rocket or the space shuttle, NASA spokeswoman Laura Rochon said.

Being in the escape craft would have allowed the astronauts to "quickly depart the station in the unlikely event the debris collided with the station causing a depressurization," the U.S. space agency said in a statement.

Warnings of the close encounter came too late for flight controllers to maneuver the station out of the way, the statement said.

It was not immediately clear how close the debris came to the space station. But NASA officials recalled at least five other times station crews had taken refuge in the Soyuz as a precaution, NASA spokesman Kyle Herring said.

Space junk is considered a threat to the estimated 800 or so commercial and military satellites operating in space and the space station, which has been continuously manned since November 2000. There are more than 18,000 pieces of space debris cataloged.

DESTRUCTIVE FORCE

Small pieces of junk can pose a danger to the space station and the shuttle because of the speed at which they move. Pieces as small as a fleck of paint, hurtling along at about 17,000 miles an hour, have damaged the shuttle's windows.

A BB-sized chunk of aluminum traveling at orbital velocity would have the same destructive potential as a bowling ball moving at 60 mph, according to American University in Washington, D.C. In a research report, it said a marble-sized aluminum sphere could be as destructive as a 400-pound (180 kg) safe falling from the roof of a 10-story building.

The crash between a U.S. satellite and a defunct Russian military satellite over northern Siberia in February created more than 500 pieces of new space debris to be tracked by the U.S. Strategic Command, the arm of the Pentagon that monitors space junk.

The first of those pieces was expected to re-enter Earth's atmosphere on Thursday.

As a result of that accident, NASA calculated the chance of a catastrophic impact with orbital debris had been increased by 6 percent, to 1 in 318, for the next shuttle mission.

Thursday's incident occurred a day after NASA postponed until Sunday the scheduled launch of shuttle Discovery on a mission to the space station, because of a hydrogen leak during fueling.

The first of five shuttle flights planned this year is to deliver a final set of solar power panels to the space station and transport Japan's first astronaut to serve as a member of the station crew.

Sunday's liftoff is scheduled for 7:43 p.m. EDT/2343 GMT from the Kennedy Space Center in Florida.

The space station, a project of 16 nations, has been under construction 220 miles above Earth for more than a decade. NASA plans up to nine shuttle flights to complete assembly, as well as a final servicing call to the Hubble Space Telescope, before it retires the shuttle fleet next year.

(Writing by Jim Loney; Additional reporting by Tom Brown and Jane Sutton in Miami, Maggie Fox in Washington, Ed Stoddard in Dallas and Ludmilla Danilova in Moscow; Editing by Pascal Fletcher)