Miami - Astronauts at the International Space Station rushed to take shelter Wednesday after a system failure signalled a possible ammonia leak, but NASA said later it may have been a false alarm.
The six-member crew donned emergency masks and hurried to the Russian side of the orbiting lab two separate times after the problem was noticed at around 4 am (0900 GMT).
At first, it seemed that high pressure outside the space station could have led to ammonia leaking inside, so the crew put on breathing masks and moved to the Russian side for safety.
Ammonia is used in the cooling and heating systems at the orbiting outpost.
The crew was allowed to come briefly back to the US side, but when NASA noticed that pressure in the cabin was rising, the crew returned to the Russian side and closed the hatch behind them.
While the Russian space agency told news outlets in Moscow that the cause was a toxic ammonia leak, NASA said there was no data to confirm that, and stressed that the crew was safe.
"At this time the team does not believe we leaked ammonia," ISS program manager Mike Suffredini said.
"There was never any risk to the crew," he added.
"We were watching the data and trying not to isolate them, but we isolated them twice pretty fast."
Earlier, NASA's Jim Kelly at mission control in Houston said a review of the data appeared to show a sensor problem or a computer relay issue could have led to the alarm.
"It is becoming a stronger case that this is a false indication, which is great news," Kelly said to US astronaut and space station commander Barry Wilmore in an exchange broadcast on NASA television.
The six astronauts taking shelter in the Russian segment have enough food for at least a week, NASA said.
"Hey everybody, thanks for your concern. We're all safe & doing well in the Russian segment," European Space Agency astronaut Samantha Cristoforetti, who is from Italy, said on Twitter.
Suffredini said the goal is to get the two Americans and one European astronaut back to their regular quarters by this evening.
"While it is inconvenient for the crew to be in Russian segment it is certainly not unhealthy for them," he added.
- Problem in loop -
The problem became apparent when flight controllers in Houston "saw an increase in pressure in the station's water loop for thermal control system B then later saw a cabin pressure increase that could be indicative of an ammonia leak in the worst case scenario," NASA said on its website.
The International Space Station is a rare area of US-Russian cooperation that has not been hit by the crisis in Ukraine, which has prompted Washington to impose sanctions on Moscow.
In total 16 countries work on the ISS, whose cost is mainly shouldered by the United States.
Since NASA phased out the space shuttle system in 2011, it depends entirely on Russia to send its astronauts to the ISS.
The Expedition 42 crew had been awake for about two hours before the alarm sounded, and was at work unloading the SpaceX Dragon cargo carrier which arrived days ago with more than 2.5 tons of supplies and science experiments.
Suffredini said some freezers had to be temporarily turned off, but that no research had been lost.
Two women and four men are on board the space station, making up a crew that hails from Russia, the United States and Italy.
They include Wilmore, Cristoforetti, Elena Serova, Alexander Samoukutyaev, Terry Virts and Anton Shkaplerov.
AFP
