Space Station Crew Returns After Alarm Scare Prompts Evacuation

Astronauts returned to the U.S. portion of the International Space Station after a false alarm triggered a partial evacuation of the orbiting laboratory.

All six crew members moved to the station’s Russian section early today after a warning suggested trouble with a coolant-pressure system on the American side that could have indicated a dangerous ammonia leak, the National Aeronautics and Space Administration said in a statement on its website. The agency later said an error message in the computer relay system may have triggered the alarm.

The crew members were never in danger, NASA said. While no ammonia was detected, the astronauts donned protective masks when re-entering the U.S. segment at 3:05 p.m. New York time, the agency said.

The precautions were taken because an ammonia leak in the cabin could lead to costly mission complications or loss of life, said Leroy Chiao, a former astronaut who served as commander of the space station for six months until early 2005. While an internal ammonia leak has not happened on the station, Chiao called it a “nightmare scenario.”

“If you’ve got ammonia coming into the cabin, you’ve got a toxic atmosphere,” Chiao, who now does consulting and teaching, said in a telephone interview. “If it was serious enough, you could have a situation where you need to evacuate the crew and the station is crippled. It could eventually cascade to where you could lose the station.”

After the alarm went off around 4 a.m., crew members sealed off the affected section and cut power to nonessential equipment, the agency said.

The crew includes two Americans, Commander Barry Wilmore and flight engineer Terry Virts. The scare may result in minor delays to some research activities, including an experiment involving fruit flies, but no research was jeopardized, NASA said.

While the station has 13,696 cubic feet of habitable space, or about the same as a six-bedroom house, fitting everyone into the Russian segment would be tight, Chiao said.

“It’s livable,” he said. “It’s nothing you want to do long term.”

While the sensors on the space station are generally reliable, they occasionally give false readings, Chiao said.