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Space Station Exhaust Almost Contaminates US Astronaut in Recent Spacewalk

International space station controllers are changing some spacewalk procedures following the near contamination of the U.S. crew member last month when he came too close to station jet exhaust. The issue is related to a mysterious problem controllers are having steering the outpost with gyroscopes during spacewalks.

Officials say astronaut Leroy Chiao inadvertently entered an unsafe zone outside the space station during a spacewalk he conducted three weeks ago with Russian cosmonaut Salizhan Sharipov. He ventured too close to jet thrusters that help stabilize the station.

Russian mission controllers supervised the spacewalk. The chief U.S. flight director for the mission, Annette Hasbrook, says miscommunication caused the incident. She says the Russian controllers issued verbal warnings about the spacewalkers' location, but the crew did not understand them.

The U.S. space officials says there is no evidence exhust fumes contaminated astronaut Chiao's spacesuit. She points out that the incident emphasizes the need for better procedures whenever jet thrusters are fired during spacewalks, which she refers to as "extravehicular activities."

"Obviously from this, we need to go forward and improve our processes to prevent this from happening again," he said. "We are updating our flight rules to define a crew 'safe zone' where crew members can be located during extravehicular activities. We are also defining space-to-ground protocols that we will use that will be clearly understood by the crew and the ground team in order to move into specific zones."

Ms. Hasbrook says the new rules will be in effect by the next spacewalk in March, when the two crewmen install more hardware to prepare for the arrival later this year of a new unmanned European cargo ship.

Originally, jet thrusters were not fired during spacewalks. But when the last one took place in late January, the space station's stabilizing gyroscopes became overloaded and the outpost began to tilt, causing the need to fire the jets for repositioning. This mysterious problem has occurred during a previous spacewalk and puzzles the U.S. and Russian space agencies.

One theory is that an unexplained force is overtaxing the gyroscopes. Mission engineers have suggested it might be air escaping from a hatch door or from the spacesuits. Ms. Hasbrook says U.S. and Russian technicians are still trying determine the cause. "Folks are still continuing to isolate the causes that are creating the phantom torque. They do have a joint team in work with both Houston and Moscow specialists They are continuing to work it and as they get to a technical conclusion, then they can figure out what the fix is," she said.

U.S. space station officials also say they are considering the possibility of increasing the size of the space station crew to three again soon. They reduced it to two after the space shuttle fleet was grounded because of the loss of the orbiter Columbia in 2003. Russian cargo vehicles cannot carry the volume of supplies a big shuttle can, requiring the temporary decrease in station crew size. But the U.S. space agency is preparing to return shuttles to the outpost beginning in May or June, clearing the way for the extra station inhabitant.

A panel of independent safety experts advising NASA on the shuttle improvements says it sees no obstacles to a launch at that time.