Following the discovery of a “new pressure signature” in the Russian Zvezda service module—an area already known for a persistent air leak since 2019—NASA and Axiom Space have decided to indefinitely postpone the launch of the Axiom Mission 4 (Ax-4) private astronaut mission to the ISS.
Announced on June 12, 2025, this move is intended to give NASA and Roscosmos, the Russian space agency, more time to look into the new development and determine whether extra troubleshooting is necessary before moving forward with the mission.
Recurrent air leaks in the Zvezda module’s vestibule, or PrK, have long been a source of concern; NASA and Roscosmos have varying opinions about how serious these leaks are. Following recent repairs, the most recent problem surfaced, leading cosmonauts on board the ISS to examine the interior of the module, seal up more possible leak locations, and gauge the current leak rate. After taking these steps, NASA stated that the segment is retaining pressure at the moment, but stressed the necessity of additional assessment to guarantee the security of upcoming crewed flights.
The Ax-4 mission was to launch aboard a SpaceX Dragon spacecraft from Kennedy Space Center. It was to be led by former NASA astronaut Peggy Whitson and include ISRO astronaut Shubhanshu Shukla (India’s first Gaganyaatri to the ISS), along with mission specialists from Poland and Hungary. A liquid oxygen leak found in the Falcon 9 rocket during pre-launch inspections was one of several other technical and weather-related delays the mission had previously experienced.
The postponement is required to allow for a comprehensive review and to remove any lingering concerns, according to NASA, which has not established a new launch date for Ax-4. A major delay might affect the scheduling for future missions, like Crew-11, which is presently planned for no early than late July 2025, the agency added. For its part, SpaceX has stated that once the matter is settled, it would work closely with NASA and Axiom Space to identify a new launch opportunity.
The ongoing inquiry into the integrity of the Zvezda module brings to light the difficulties and complications of maintaining the ISS’s old infrastructure, especially as the number of commercial and international crewed missions increases. When deciding how to proceed with Ax-4 and subsequent flights, NASA and its partners have reaffirmed their dedication to crew safety and mission assurance as the top concerns.
