NASA and Axiom Space have announced an indefinite delay of the Ax-4 private astronaut mission to the International Space Station (ISS) following the detection of a new pressure anomaly in a section of the station with a history of air leaks.
SpaceX Dragon spacecraft at the ISS during Axiom Space’s AX3 mission in 2024 Credit: NASA
In a statement released June 12, NASA confirmed the mission would be postponed to allow additional time for investigation into the situation aboard the Russian-built Zvezda service module, specifically in a vestibule area known as the PrK, which links a docking port to the rest of the module. This segment has been a point of concern since an air leak was first discovered in 2019. Despite several repair attempts by Russia’s space agency Roscosmos, the issue has persisted.
"As part of an ongoing investigation, NASA is working with Roscosmos to understand a new pressure signature, following recent repair efforts in the aft-most segment of Zvezda," the agency stated. While the precise nature of the pressure changes has not been disclosed, NASA noted that cosmonauts have conducted inspections and sealed additional suspect areas. For now, the module is reportedly maintaining pressure.
NASA emphasized that the postponement of Ax-4 provides critical time for both agencies to assess the safety of the station and determine whether further repairs or diagnostics are needed.
Long-standing concerns remain over the integrity of the PrK vestibule. Last year, a NASA ISS advisory panel highlighted discrepancies between NASA and Roscosmos over the severity and cause of the leaks, with NASA expressing worry over a potential "catastrophic failure." During an April 17 safety panel meeting, Rich Williams, a panel member, labeled the issue “one of our highest concerns.”
The vestibule is typically sealed off when not in use, especially when no Progress cargo spacecraft are docked. To minimize risk, NASA astronauts have occasionally closed the hatch between the American and Russian segments of the station when the area is accessed.
The Ax-4 mission was nearing launch readiness with SpaceX preparing a Falcon 9 rocket after a June 11 attempt was scrubbed due to a liquid oxygen leak. A tanking test was successfully conducted on June 12, shortly before NASA announced the indefinite delay.
SpaceX acknowledged the decision in a social media update, confirming it would collaborate closely with NASA and Axiom Space to identify a new launch window. Axiom Space Executive Chairman Kam Ghaffarian supported the delay, calling it "the right thing to do for Axiom Space, for NASA, and for our customers."
NASA had previously indicated that launch windows for Ax-4 would remain open through the end of June and resume in mid-July. However, a prolonged delay could potentially disrupt the planned schedule for NASA’s Crew-11 mission, currently slated for no earlier than late July.
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