NASA reverses evacuation alert for ISS crew after air leak assessment

NASA ordered five astronauts aboard the International Space Station (ISS) to take shelter in a docked SpaceX Crew Dragon spacecraft for nearly two hours on Friday after a worsening air leak was detected in a Russian section of the orbiting laboratory.

The order was issued at 9:04 a.m., directing the four members of NASA's Crew-12 mission – NASA astronauts Jessica Meir and Jack Hathaway, European Space Agency astronaut Sophie Adenot, and Roscosmos cosmonaut Andrey Fedyaev – along with NASA astronaut Christopher Williams, to enter the Dragon capsule, which serves as an emergency lifeboat in the event of an evacuation.

Roughly two hours later, NASA reversed the alert and told the astronauts they could return to the station as the agency and its Russian counterparts examined the rate of air leakage.

"NASA has instructed the crew members inside the Dragon spacecraft to end the safe haven procedures and return to planned operations aboard the International Space Station," NASA spokesperson Bethany Stevens said.

Safe haven procedures are rare aboard the ISS, though space debris that risks colliding with the ISS and smaller changes in air leak rates have triggered the process in recent years. Despite its 27-year operational history, astronauts have never had to evacuate the station.

The incident stemmed from ongoing concerns over small air leaks in the Russian-operated Zvezda service module, a critical component of the ISS. NASA and Roscosmos have spent months investigating the source of cracks and leaks in a transfer chamber known as PrK.

According to Roscosmos, two potential leak sites were identified during an inspection of the PrK. The first was promptly sealed using a two-component sealant called Germetall-1, while work is underway to repair the second leak located on the chamber's conical part.

There was no immediate threat to the crew and the spacecraft's systems, Roscosmos said.

The air leaks have been relatively minor in recent months but escalated on Friday from a pound of air per day to two pounds, according to a senior NASA official who asked not to be named.

The ISS is currently home to seven astronauts from two missions. In addition to the five astronauts who executed evacuation procedures, there are two cosmonauts, Sergey Kud-Sverchkov and Sergei Mikayev.

Kud-Sverchkov and Mikayev were planning to use a saw to reach an area where they believed they could access the crack leaking air, while NASA officials disagreed with this method, prompting mission control in Houston to order safe haven procedures.

Stevens had previously said that the affected transfer tunnel has experienced cracks and leaks for some time. "NASA and Roscosmos have been working to determine the root cause of the cracks, and Roscosmos manages the issue through operational mitigation measures and periodic partial repair efforts," she said.

The ISS has been continuously inhabited for more than 25 years. The aging orbital outpost is scheduled to be retired around 2030, when it will be guided into Earth's atmosphere before crashing into an isolated spot in the Pacific Ocean.

Meanwhile, legislation before the US Congress would extend the station's operational life by two years, until 2032, to allow more time for companies to develop a replacement.

(With input from agencies)