NASA ordered astronauts aboard the International Space Station (ISS) to prepare for a possible emergency evacuation Friday after a worsening air leak in the station's Russian segment raised fresh concerns about the safety of the aging orbital outpost.Five crew members were directed to shelter inside a docked SpaceX Dragon spacecraft while Russian cosmonauts attempted repairs on the leak, which is located in the Zvezda service module transfer tunnel. NASA described the move as a precautionary measure while engineers assessed the situation.“The Zvezda service module transfer tunnel, known as PrK, has suffered from cracks and leaks for some time,” NASA spokesperson Bethany Stevens said. The space agency said it has been monitoring the problem closely alongside Russia's Roscosmos space agency.The leak is the latest in a series of structural concerns involving the Russian-built section of the ISS. Cracks and air leaks in the module have been reported since 2019, with NASA previously classifying the issue among its highest safety concerns.Roscosmos reported that two separate leak sites were discovered during efforts to pressurize the transfer chamber. One leak was quickly sealed with a specialized compound, while technicians continued investigating a second suspected leak. Russian officials insisted there was no immediate threat to the crew or station systems.The shelter order lasted roughly two hours before NASA instructed astronauts to return to normal operations after Roscosmos paused repair work to collect additional data..NASA emphasized the evacuation preparations were undertaken “out of an abundance of caution” while repair efforts were underway. The agency said it would continue working with its Russian counterparts on a permanent solution.The incident has renewed scrutiny of the 28-year-old space station, parts of which have been operating in orbit for nearly three decades. Engineers have struggled for years to identify the root cause of recurring cracks and leaks in the Russian segment.The ISS remains one of the largest international scientific collaborations ever undertaken, hosting astronauts and cosmonauts from multiple countries. However, repeated structural issues have fuelled debate over how long the station can safely remain operational before being replaced by newer commercial platforms.While Friday's incident ended without an evacuation, it provided a stark reminder that even after more than two decades of continuous occupation, the world's premier space laboratory remains vulnerable to the realities of aging infrastructure hundreds of kilometres above Earth.