A private astronaut mission has recently taken flight, revealing new complexities surrounding a persistent and potentially hazardous issue at the International Space Station (ISS), which is the most frequently visited destination in space. Axiom Space Mission 4, also known as Ax-4, successfully lifted off from NASA’s Kennedy Space Center in Florida at 2:32 a.m. ET on Wednesday. The launch faced delays due to concerns about leaks affecting the ISS, particularly a module controlled by Russia.
For several years, the ISS has been experiencing a slow air leak from a Russian module that typically remains isolated from the rest of the space station. Recently, however, operators of the space station noticed that the leak, which had been occurring gradually, appeared to have stopped. This development raised significant concerns, as it suggested that efforts to seal cracks in the module's exterior might have been successful. Nevertheless, NASA engineers have expressed worries that the module could instead be maintaining stable pressure due to a potential new leak forming on an interior wall. This scenario could allow air from the rest of the ISS to rush into the compromised area, raising alarms about the integrity of the entire station.
The full extent of this issue remains unclear. NASA first disclosed these concerns in a statement on June 14, which led to the decision to postpone the Ax-4 mission while station operators investigated the problem. “By changing pressure in the transfer tunnel and monitoring over time, teams are evaluating the condition of the transfer tunnel and the hatch seal,” the statement noted.
After a delay of over a week, NASA announced a new launch target for Ax-4 and revealed its collaboration with officials from Roscosmos, the Russian space agency, to further investigate the leak issue. The two space agencies agreed to lower the pressure in the transfer tunnel, and teams will continue to monitor the situation moving forward. However, NASA has deferred further comments about the leak to Roscosmos, which has not responded to inquiries regarding the matter.
The leaks were first detected in 2019 and are located in a tunnel connecting a Russian module called Zvezda to a docking port that accommodates cargo and supply spacecraft. The cracks are minuscule and often invisible, complicating repair efforts. The urgency of the situation escalated last year when the leak rate reached its highest level. Disagreements between technical teams in the U.S. and Russia have compounded the issue, with NASA's ISS Advisory Committee Chair Bob Cabana noting differing opinions on the safety of continued operations. “The Russians believe that continued operations are safe — but they can’t prove that to our satisfaction,” Cabana remarked. Conversely, he stated, “the US believes that it’s not safe, but we can’t prove that to the Russian satisfaction.”
As NASA and Roscosmos work to resolve the leak issue, the four crew members aboard Ax-4 have been in quarantine in Florida for approximately a month, awaiting their launch. This groundbreaking mission includes former NASA astronaut Peggy Whitson, who is now an employee of Axiom Space, alongside three spaceflight novices: Shubhanshu Shukla from India, Sławosz Uznański-Wiśniewski from Poland, and Tibor Kapu from Hungary. All three will be the first astronauts from their countries to visit the ISS. The Ax-4 crew is expected to spend around two weeks in space, conducting approximately 60 scientific experiments before their return.
It remains uncertain how the ongoing leak issue in the Zvezda transfer tunnel may impact broader operations on the ISS. While privately funded missions like Ax-4 are relatively rare, NASA and Roscosmos routinely send crews of astronauts and cosmonauts to maintain station operations. The upcoming Crew-11 mission, set to mark the 12th crew rotation for SpaceX on NASA’s behalf, is scheduled to launch as early as July. This mission will include NASA astronauts Zena Cardman and Mike Fincke, Japan Aerospace Exploration Agency astronaut Kimiya Yui, and Roscosmos cosmonaut Oleg Platonov. They are anticipated to spend approximately six months aboard the ISS, continuing the vital work necessary to support life in space.
