On Friday, June 5, 2026, the crew of the International Space Station (ISS) was forced into a rare and frightening protocol, a “safe haven” order directing five of the seven astronauts to take shelter inside the docked SpaceX Crew Dragon spacecraft for roughly two hours. The trigger was a sudden and significant worsening of a long‑standing air leak in the Russian Zvezda service module, which had doubled its rate of air loss from approximately one pound to two pounds per day.
While the astronauts have since returned to their regular duties and the situation is under control, the incident has drawn renewed attention to a persistent problem that NASA’s inspector general has classified as the agency’s “top safety risk.”
The sequence of events began earlier in the week when ground controllers noticed a troubling trend. Although the Zvezda module’s transfer tunnel, designated PrK, had been leaking air at a manageable rate for years, the situation escalated significantly on Monday, June 1, when the leakage rate doubled. By Friday morning, the Russian space agency Roscosmos had identified two distinct leaks in the module. According to Roscosmos, the first leak was quickly sealed, and preparations were underway to address the second. However, the urgency of the repair attempt prompted a sharp disagreement between NASA and Roscosmos over the appropriate course of action. The two agencies have debated for months over the cause and potential fixes for the cracks, with NASA officials expressing concern that some proposed repair methods could pose additional risks to the station’s integrity. This tension came to a head on Friday when NASA mission control in Houston ordered five of the seven astronauts to take shelter inside the docked SpaceX Crew Dragon “Freedom” capsule, which serves as a designated “safe haven” in the event of an emergency. The order, issued at 9:04 a.m. ET, applied to the four astronauts of the Crew‑12 mission, two Americans, a French astronaut, and a Russian cosmonaut, plus one additional US astronaut. Notably, the two Russian cosmonauts who were performing the repair work did not evacuate; they remained inside the Zvezda module itself, continuing their efforts.
The shelter in place order was a precautionary measure, not a full evacuation. The astronauts inside the Crew Dragon did not don their spacesuits, but they were ready to seal themselves inside the capsule if the leak rate had continued to accelerate. After approximately two hours, NASA reversed the order, instructing the astronauts that they could return to the station. Roscosmos had paused its structural repair efforts to allow for further assessment of the situation, and the immediate threat had subsided. NASA spokesperson Bethany Stevens later stated that the agency looks forward to “working with Roscosmos on a collaborative approach to address the leaks.”
The Zvezda service module is a cornerstone of the ISS, having been launched in July 2000 as the third module of the station. It contains life‑support equipment, propulsion systems, and living quarters, and it also serves as the transfer tunnel connecting the station to Russian docking ports. The module has been plagued by air leaks since at least 2019, when a small crack was first detected. In March 2021, Russian cosmonauts used improvised methods, such as releasing tea leaves to visualise airflow, to locate and seal two cracks in the transfer tunnel. Those repairs, however, were only partially successful.
By 2024, the cracks had begun to open again, and the leak rate, while still low, had become a persistent concern. NASA’s inspector general has repeatedly highlighted the Zvezda module’s transfer tunnel as a “top safety risk,” warning that a catastrophic failure could lead to a rapid depressurization of the station. The two agencies have disagreed over the root cause: while Roscosmos has attributed the cracks to metal fatigue and micro‑meteoroid impacts, NASA has expressed concern that vibrations from docking and undocking operations may be contributing to the problem. Regardless of the cause, the issue has now become a recurring feature of ISS operations, with each new crack requiring careful monitoring and periodic repair.
What made Friday’s event notable was not the existence of a leak, but the sudden and unexplained doubling of the leak rate. According to a senior NASA official who spoke on condition of anonymity, the loss of atmospheric pressure had remained relatively stable for months, but on June 1, the rate abruptly increased from approximately one pound of air per day to two pounds. This escalation prompted Roscosmos to schedule a more aggressive repair attempt for June 5.
During that attempt, Russian cosmonauts used a saw to access an area where they believed the crack was located, a procedure that NASA officials viewed with concern. The disagreement over the method was reportedly the immediate cause of the safe haven order; NASA wanted to ensure that the astronauts were protected in case the repair inadvertently worsened the leak. Once Roscosmos paused its efforts, the shelter order was lifted.
The safe‑haven order on June 5 was not a full evacuation, but it was the closest the ISS has come to requiring its crew to leave the station since its first module was launched in 1998. While no astronauts were ever in immediate danger, the ISS can operate for extended periods with small leaks, the event has highlighted the importance of having a robust emergency plan. The five astronauts who took shelter inside the Crew Dragon “Freedom” were following a well‑rehearsed procedure.
In the event of a more serious leak, the ISS crew would split up, with some returning to Earth aboard the Crew Dragon and others using the Russian Soyuz capsule docked at the station. The current crew of seven includes two Soyuz cosmonauts, who would have their own evacuation path. Friday’s event has given the agencies an opportunity to test their procedures and refine their response. It also serves as a reminder that the ISS is an aging platform, and that while it remains the most sophisticated laboratory ever built, its long term viability will depend on continued investment and international cooperation.