NASA and Axiom Space have indefinitely postponed the launch of the Axiom Mission 4 (Ax-4) private astronaut mission to the International Space Station (ISS) following the detection of a “new pressure signature” in the Russian Zvezda service module, an area already known for a persistent air leak since 2019.

This decision, announced on June 12, 2025, aims to provide NASA and Roscosmos—the Russian space agency—additional time to investigate the new development and assess whether further troubleshooting is required before proceeding with the mission.

The Zvezda module’s vestibule, known as PrK, has been a longstanding concern due to recurring air leaks, with differing assessments of severity between NASA and Roscosmos. The latest issue emerged after recent repair efforts, prompting cosmonauts aboard the ISS to inspect the module’s interior, seal additional potential leak sites, and measure the current leak rate. Following these actions, NASA reported that the segment is currently holding pressure, but emphasized the need for further evaluation to ensure the safety of future crewed missions.

The Ax-4 mission, which was to be commanded by former NASA astronaut Peggy Whitson and include ISRO astronaut Shubhanshu Shukla (India’s first Gaganyaatri to the ISS), as well as mission specialists from Poland and Hungary, was scheduled to launch aboard a SpaceX Dragon spacecraft from Kennedy Space Center. However, the mission had already faced multiple delays due to unrelated technical and weather issues, including a liquid oxygen leak detected in the Falcon 9 rocket during pre-launch checks.

NASA has not set a new launch date for Ax-4, stating that the postponement is necessary to allow for a thorough investigation and to address any remaining risks. The agency also noted that a significant delay could impact the timeline for subsequent missions, such as Crew-11, which is currently scheduled for no earlier than late July 2025. SpaceX, for its part, has indicated it will coordinate closely with NASA and Axiom Space to determine a new launch opportunity once the situation is resolved.

The ongoing investigation into the Zvezda module’s integrity highlights the complexities and challenges of maintaining the aging ISS infrastructure, particularly as commercial and international crewed missions become more frequent. NASA and its partners have reiterated their commitment to crew safety and mission assurance as the top priorities in determining the path forward for Ax-4 and future flights.

Agencies