News : Space station crew poised for risky spacewalk

By Irene Klotz

CAPE CANAVERAL, Florida (Reuters) - Two cosmonauts aboard the International Space Station prepared for a spacewalk on Thursday to remove an explosive bolt from their Soyuz capsule in hopes of fixing a problem that led to rough landings for two previous crews.

The six-hour outing by Sergei Volkov, the station's commander, and Oleg Kononenk, lead flight engineer, was scheduled to begin at 2:21 p.m. EDT (1821 GMT).

"We have looked very carefully at the risks associated with removing a pyro-bolt," said NASA flight director Bob Dempsey. "We are very confident this is a safe operation to do."

It will be the first spacewalk for both cosmonauts, who have been aboard the $100 billion orbital outpost since April. Their crewmate, NASA astronaut Greg Chamitoff, will be inside the Soyuz during the spacewalk to avoid being cut off from an escape route to the ship during the spacewalk.

"We do not like to separate the crew from (the) escape vehicle," said Dempsey. "Therefore Greg will be staying in there. He will have some laptops, books and computers to work on while he's there."

The Soyuz has not been moved since former station commander Peggy Whitson and her crew endured a high-speed, off-course, hard landing aboard another Soyuz on April 19. It was the second consecutive troubled landing for a Soyuz capsule.

The cause of the problem remains under investigation. A leading suspect is an explosive bolt used to separate the section of the Soyuz holding the crew from a small equipment module that does not return through the atmosphere. There are five connections between the two compartments and all have redundant explosive charges.

Volkov and Kononenko's job is to disconnect one of the bolts, seal it in a blast-proof steel canister and bring it inside the space station so it can be returned with the crew in October.

"We dream of a lot of wild things to do and after much analysis, sometimes we do them and sometimes we don't," said station program manager Mike Suffredini. "This has been done with all the rigor we would expect for a system that was critical like this."

The bolt has an explosive blast about equivalent to an M-80 firework.

During a final review of spacewalk procedures on Wednesday, Russian flight director Vladimir Solovyov told the crew: "It cannot fire. You should not be concerned at all."

His comments were translated into English and broadcast on NASA Television.

Tests show the steel case that will hold the bolt can withstand an unexpected detonation, Dempsey added.

Explosive bolts have been safely used for decades on the space shuttle and other space vehicles, as well as on military aircraft. The bolts are usually handled by ground crews and safety experts, not by spacewalking astronauts and cosmonauts.

(Editing by Doina Chiacu)