Worsening Air Leaks in the ISS Russian Zvezda Module Highlight Structural Integrity Disputes

Worsening Air Leaks in the ISS Russian Zvezda Module Highlight Structural Integrity Disputes

The aging infrastructure of the International Space Station (ISS) has faced escalating safety concerns due to a persistent and worsening air leak in the transfer tunnel (PrK) of the Russian-built Zvezda service module. The ongoing issue has sparked technical disagreements between NASA and Russia's space agency, Roscosmos, regarding the structural integrity of the station and appropriate repair protocols.

Worsening Leak Rates and Evacuation Drills

The air leak is occurring in the PrK transfer tunnel, which connects the Zvezda module's main living quarters to a docking port. The leak is caused by micro-cracks in the tunnel's aluminum hull. In June and July 2026, the leak rate fluctuated, prompting safety drills and temporary shelter procedures:

• During ongoing maintenance and diagnostic work on the leaky module, astronauts on the ISS were ordered to take shelter in their respective spacecraft (acting as emergency "safe havens") while the transfer tunnel was isolated.
• NASA views the worsening leak as a significant safety risk with the potential for catastrophic structural failure if cracks propagate, while Roscosmos has repeatedly characterized the leak as a slow, non-dangerous operational issue.

Disagreements Over Repair Methods and Isolation Plans

The technical divergence between the two space agencies has extended to the proposed repair methods:

• Roscosmos Proposals: Russian engineers initially proposed repairing the cracks by drilling into the hull. Following NASA objections, Roscosmos proposed having cosmonauts use saws to remove load-bearing brackets inside the PrK transport tunnel to access and patch the underlying structure.
• NASA Objections: NASA raised concerns that cutting load-bearing brackets could compromise the module's structural integrity. Roscosmos subsequently withdrew the bracket-sawing proposal, and the temporary shelter order was lifted.

Following these events, Roscosmos informed NASA that if the leak rate cannot be stabilized or permanently repaired, they are prepared to permanently isolate and "separate" the PrK transfer tunnel from the rest of the ISS.¹ While this would resolve the immediate atmospheric leak risk, it would permanently deactivate one of the Russian segment's primary docking ports, highlighting the challenges of maintaining the 25-year-old orbital laboratory ahead of its planned decommissioning in 2030.