Microscopic cracks in Russian Zvezda module have vented more than two pounds of air daily since 2019 despite multiple repair attempts
An air leak on board the International Space Station (ISS) left astronauts sheltering in their lifeboats on Friday afternoon, fearing an evacuation might be required.
Nasa and the Russian space agency Roscosmos have been struggling to seal microscopic structural cracks in a transfer tunnel leading to the Russian Zvezda module since 2019.
At its peak, the leak was venting more than two pounds of air per day, but in recent months the astronauts thought they had the problem under control.
However, in May, Russian cosmonauts who were unloading cargo from the Progress 95 spacecraft noticed a slow pressure drop in the Zvezda module, and discovered the leak had returned.
On Friday, Nasa ordered five of the ISS crew to shelter inside the docked SpaceX Crew Dragon “Freedom” craft, while the remaining two Russian astronauts attempted another assessment and repair.
At around 3.30pm BST, mission control told Jessica Meir, a Nasa astronaut, that the Russian crew had decided to “perform only measurements” of the leaks and so the “safe haven configuration” – or the order for them to take shelter – was being cancelled.
“We are comfortable with backing out of the safe haven config,” astronauts were told from Houston. “With today’s operations, they wanted to be extra safe, extra precautionary, and have the crew move into the safe haven posture,” a Nasa spokesman later said.
A safe haven configuration is an emergency safety procedure where crew members retreat into their docked spacecraft to use them as “lifeboats” that can immediately evacuate to Earth should the space station suffer a catastrophic failure.
Astronauts close the hatches connecting different modules of the space station, isolating the compromised area to avoid a sudden depressurisation.
Crew members float into their respective docked transport vehicles and configure the spacecraft’s internal systems to stand-alone, independent operation such as activating life support systems and establishing ground communications.
