ISS air leak worsens, prompting astronauts to shelter in Dragon capsule

NASA has reported that a persistent air leak aboard the International Space Station recently worsened, prompting engineers to investigate fresh suspected crack locations and temporarily move astronauts into a safe haven. The development is the latest chapter in a long-running concern over the structural health of the orbiting laboratory, which has been in continuous operation for more than two decades.

The leak is centred on the PrK transfer tunnel within Russia's Zvezda service module, an area that has been seeping air since 2019. The rate increased to roughly two pounds of air per day during Progress 95 cargo operations in the week beginning 1 June. The transfer tunnel connects the Zvezda module to a docking port used by visiting Russian spacecraft, making it a critical piece of the station's plumbing.

Air leaks are a serious matter aboard a spacecraft, where every breath of atmosphere must be carried up from Earth or generated on board. While the rates involved here are small relative to the station's overall volume, any increase is closely watched, both for the resources it consumes and for what it reveals about the condition of the ageing hardware.

A precautionary move

As a precaution, SpaceX Crew-12 members and NASA astronaut Chris Williams were directed to shelter inside their Dragon spacecraft while the situation was assessed. The arrangement allows the crew to depart quickly should conditions deteriorate, in effect keeping a lifeboat ready and crewed while engineers on the ground worked through the data.

Sheltering in a docked spacecraft is a well-established contingency. The capsule that carried the astronauts to the station also serves as their ride home, and remaining within it during a period of uncertainty shortens the time it would take to evacuate. NASA stressed that the crew were safe throughout and that the measure was taken out of an abundance of caution rather than in response to any immediate danger.

Roscosmos had planned to cut a bracket to improve access to a potentially leaking area, but NASA cautioned that the approach could have increased the risk to the surrounding structure. The disagreement illustrates the delicate engineering judgements involved in repairing hardware that was never designed to be opened up and worked on in orbit, and which has already endured years of thermal cycling and micrometeoroid exposure.

Repair postponed

With the two agencies weighing competing assessments of the risk, the structural repair work was paused while engineers gathered more measurements. Officials said the decision reflected a preference for caution over speed, given the importance of not making the situation worse through a hasty intervention.

• The leak is centred on the PrK transfer tunnel in Russia's Zvezda module
• Air has been seeping from the area since 2019
• Leak rate rose to about two pounds of air per day during cargo operations
• Crew temporarily sheltered in the Dragon capsule
• Roscosmos paused the structural repair work
• Engineers are gathering more measurements before proceeding

“When you are working on hardware that has been in orbit for decades, the priority is always to avoid doing anything that could make a manageable problem worse.”

— A NASA engineer briefing on the issue

Background

The International Space Station has been continuously occupied since 2000 and is a joint venture between the United States, Russia, Europe, Japan and Canada. The Zvezda service module is one of the oldest pressurised elements still in use, and the transfer tunnel leak has been monitored and partially mitigated for years through a combination of patching and managing how often the affected area is exposed to vacuum.

The episode comes against the backdrop of wider discussions about the station's future. The outpost is approaching the end of its planned operational life, and agencies are already planning for its eventual retirement and for the commercial platforms expected to succeed it. Structural concerns such as this leak feed directly into those conversations about how much longer the station can safely fly.

What happens next

Officials said the repair effort was halted to allow further inspections and data review, underlining the challenges of maintaining an ageing orbital outpost. Engineers will continue to monitor the leak rate and evaluate options for a safe and durable fix, balancing the need to preserve the station's atmosphere against the risk of intervention. For now the crew have resumed normal operations, but the incident is a reminder that keeping a human presence in orbit demands constant vigilance over hardware operating far beyond its original design assumptions.