The crew of the International Space Station (ISS) housed in its U.S. segment received a most unwelcome wake-up call in the form of an alarm indicating a possible ammonia leak at 4 a.m. EST earlier today. According to NASA, at the same time the alarm sounded, “the station’s protection software shut down one of two redundant cooling loops (Thermal Control System Loop B).”
The space agency also announced, “Flight controllers in Mission Control at NASA’s Johnson Space Center 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.” However, these fears were put to rest during the day, as evidence of an ammonia leak was not present.
Expedition 42 commander Barry “Butch” Wilmore, NASA flight engineer Terry Virts, and European Space Agency (ESA) flight engineer Samantha Cristoforetti were directed to don protective masks as per emergency procedures and move into the space station’s Russian segment with cosmonauts Alexander Samokutyaev, Elena Serova, and Anton Shkaplerov.
The hatch between the U.S. and Russian segments was closed isolating the U.S. section, also as per emergency procedures, with non-essential equipment powered down. NASA stated that at no time was the crew in any danger, and they appeared to be in good shape despite the inconvenience. In a worst case emergency scenario, there are two Soyuz spacecraft docked to Russian segment; if a serious emergency arises, crew members are able to “abandon ship” with the Soyuz lifeboats and return to Earth if needed.
No evidence of an ammonia leak was found following the alarm. NASA’s ISS team, including its partners in Moscow and other centers, held a daily planning conference this afternoon and discussed the incident. They determined that the crew could move back into the U.S. segment before the end of the day. The crew re-entered the U.S. segment at 3:05 p.m. EST and took precautions, such as wearing protective masks, while Virts and Cristoforetti tested the station’s atmosphere for ammonia upon entry; no traces of ammonia were found, allaying fears of possible toxic contamination.
NASA stated: “The alarms this morning that initiated the movement of the crew out of the U.S. segment are suspected to have been caused by a transient error message in one of the station’s computer relay systems, called a multiplexer-demultiplexer. A subsequent action to turn that relay box off and back on cleared the error message and the relay box is reported by flight controllers to be in good operating condition.”
The crew and flight controllers will reactivate Thermal Control System Loop B tonight and into Thursday, while data concerning the spurious alarm will continue to be analyzed. According to NASA, the crew will resume their normal work schedule and space station science tomorrow, while continuing to keep an eye on any possible related situations.
In May 2013, an ammonia leak occurred externally on the ISS during Expedition 35. In a previous AmericaSpace article it was stated, “The leak was discovered … as flakes were visually observed (characterized as “ammonia snow”) trailing from the P6 (“P” meaning “port”) Truss Worksite in the 2B Photovoltaic Thermal Control System, which helps cool one side of the space station’s solar panels.” Astronauts Chris Cassidy and Tom Marshburn replaced a pump controller box on the P6 truss with a spare, stopping the leak. Then, as now, at no time were any crew members aboard the station in any danger. ISS crews are trained extensively in contingency procedures and damage control in the event of emergencies.
Stay tuned to AmericaSpace for updates if this situation changes.