NASA postponed the launch of a commercial astronaut mission because another air leak occurred on the ISS. While the space agency has admitted to the problem by delaying Axiom Mission 4 which was meant to transport four private astronauts to the station, it has provided the public with limited information. NASA officials and engineers are becoming increasingly concerned about the situation behind closed doors.

This leak is not an isolated incident. Since 2019 the International Space Station has experienced a continuous slow air leak. The air leak originated from the Russian Zvezda service module which is the station’s oldest component after its launch in 2000. The transfer tunnel PrK that links Zvezda to its docking port for Soyuz crew vehicles and Progress resupply spacecraft is where the problem exists. Russian cosmonauts have conducted numerous repair operations to address the small cracks found in PrK throughout the years. While these efforts successfully lowered the leak rate they failed to achieve complete elimination of the problem. The space station experienced its highest air loss rate when it lost two pounds of air daily. Until now the most effective solution remains closing the PrK hatch whenever a spacecraft is not docking at that port.

The past few weeks saw the emergence of a breakthrough. The Russian space agency Roscosmos confirmed that PrK repair work had ended earlier this month and achieved full sealing of the module. NASA issued a similar statement. The two agencies confirmed that the past leak within the module had stopped. That news should have brought relief. But it didn’t.

Despite the PrK module being sealed, the overall air pressure aboard the ISS kept decreasing. Engineers are puzzled by the current situation as two insiders disclose fresh concerns. The station continued to lose air even though the module which had been leaking for nearly five years was now secure. Engineers suspect that the seals on the hatch leading into the PrK could be damaged. According to this scenario analysis air leakage occurs through the hatch seals from the station into the PrK. The module’s tight seal maintains stable pressure which falsely indicates no air loss while the entire station continues atmospheric depletion.

NASA is now closely monitoring the situation. The agency regards this matter as a serious concern within its internal discussions. According to a high-ranking official the atmosphere inside the ISS program is currently filled with worry. NASA postponed Axiom Mission 4 which was planned to launch this week due to growing concerns. According to the agency the delay provides extra time to assess the situation and decide if further troubleshooting measures are necessary. NASA has set June 18 as the new possible launch date but this is subject to changes based on the progression of the leak and the success of finding an effective solution.

There’s another reason this situation is so troubling: the risk of high cycle fatigue. Repeated stress over time causes structural fatigue in metals such as aluminum. The underlying principle here functions similarly to repeatedly bending a paperclip until it breaks. While in orbit for many years the ISS components have started to display deterioration with Zvezda’s older structures being the most affected. NASA has determined structural cracking to be the top severe threat on its 5×5 risk matrix that assesses potential hazards by their likelihood and severity.

The phenomenon of high cycle fatigue presents tangible dangers rather than theoretical possibilities. During 1988 Aloha Airlines Flight 243 endured a catastrophic failure when the fuselage tore apart mid-flight due to fatigue exposing passengers to open air. The safe landing of the aircraft did not diminish the fact that metal fatigue can lead to unexpected catastrophic failures.

NASA has provided limited information to the public despite growing concerns. The agency has neither held a press conference nor provided responses to numerous questions from journalists. NASA’s official statement says the ISS crew is performing their duties safely but the ongoing leak indicates possible serious structural weaknesses as the station ages and shows more signs of material fatigue.