A Russian-controlled segment of the International Space Station is leaking, allowing pressure and air to bleed out. The situation has reached a fever pitch as cosmonauts scramble to patch problem areas and officials from Russia's space agency, Roscosmos, and NASA disagree about the severity of the problem. The football field-size space laboratory must remain pressurized and filled with breathable gases to host a rotating crew of astronauts, which it has done since 2000 in separate but connected Russian and US sections. Problematic leaks were first identified in 2019 in a tunnel that connects a Russian module, called Zvezda, to a docking port that welcomes spacecraft carrying cargo and supplies. But the rate at which the module is bleeding air hit a new high this year. Oversight officials in the United States now consider this issue to be the most pressing problem facing the aging space station, one that could threaten the safety of the crew, according to a recent report from NASA's Office of Inspector General. The US space agency "has expressed concerns about the structural integrity of the (leaking module) and the possibility of a catastrophic failure," said former NASA astronaut Bob Cabana, chair of the agency's ISS Advisory Committee, during a meeting on the issue Wednesday. But while Roscosmos has directed its cosmonauts to search for and address problematic areas — which has reduced the leak rate — the Russian team "does not believe catastrophic disintegration ... is realistic," Cabana said. "The Russians believe that continued operations are safe — but they can't prove that to our satisfaction," Cabana added. "And the US believes that it's not safe, but we can't prove that to the Russian satisfaction." The disagreements persist despite a September meeting that Cabana said took place in Russia. Now, the US is pushing for independent experts from both sides to evaluate the issue and help the two space agencies reach a consensus on the root cause and severity of the leaks. The United States has already taken steps to create its own team of experts, Cabana said. Russia has not yet complied with the recommendation. Still, Cabana said the September meeting with Russia was "extremely successful." Roscosmos did not respond to an email request for comment. Meanwhile, astronauts and cosmonauts — the Russian term for astronaut — aboard the space station have been required to adopt precautionary measures, such as keeping the leaking segment sealed off at all times, except when it must be opened to unpack cargo from spacecraft that arrive at the nearby docking port. When astronauts must open that segment, they close the hatch that separates the US and Russian portions of the station, NASA astronaut Michael Barratt said during a November 8 news briefing. "We've taken a very conservative approach," Barratt said. "It's not a comfortable thing, but it is the best agreement between all of the smart people on both sides — and it's something that we as a crew live with." As the orbiting laboratory ages, both agencies currently face making crucial decisions about how and when to cease its operations and safely dispose of the station. The ongoing leak issue raises serious questions about the safety of the station — and the ability of NASA and Roscosmos to reach a consensus. NASA and Roscosmos have known for years that the Russian module was gradually leaking. The issue is exacerbated by the fact that the suspected cracks are "very small, not visible with the naked eye and have brackets and pipelines near them, making it difficult to get diagnostic tools into these areas," NASA said in a statement to CNN on Thursday. Efforts to mitigate the leaks have staved off the problem for now. However, the leak rate still "ranges from 2 to 2.5 pounds (of air) per day above space station baseline," according to NASA. For context, the space station aims to remain pressurized at 14.7 pounds per square inch absolute — which mimics the pressure of the atmosphere at sea level here on our home planet. The space agency did not respond to a request to compare the current leak rate with the peak recorded earlier this year. Technical teams in the US and Russia do not see eye to eye on what exactly might be causing the problem, according to Cabana. Russian experts believe vibrations — which could be caused by mechanical systems such as the ones used for energy storage — on the space station are stressing the walls, causing "high cycle fatigue," or a phenomenon in which a relatively gentle force begins to crack and wear a metal to the point of failure over long periods of time. NASA, on the other hand, believes the picture is more complicated, involving several factors such as mechanical stress, environmental exposure, and "residual stress" or potential issues that stem from manufacturing of materials used in the transfer module, according to Cabana. A report published in September from NASA's Office of the Inspector General also notes that, while NASA and Roscosmos agree that the problematic segment may need to be permanently shuttered if the leak rate reaches an "untenable" level — the two sides have not reached an agreement on exactly how to define "untenable." However, while the space agencies remain at odds about the severity of the problem, Cabana and Barratt — and NASA's ISS program manager Dana Weigel in a statement — all said that NASA and Roscosmos remain in close communication about the issue. "We have a very open and transparent relationship with our Russian cosmonaut compadres," said Barratt, who returned from a 232-day stay on the International Space Station in late October. "It's a very integrated crew." As NASA and Roscosmos work to address the leaks, the US space agency has taken some steps of its own to ensure astronaut safety. In addition to requiring astronauts to close off the entrance to the Russian section when the Zvezda transfer tunnel is open, the US agency is now putting an extra "pallet seat" aboard SpaceX Crew Dragon spacecraft. The pallet seat sits on top of an area in the spacecraft that is typically used to hold cargo, and it's essentially a piece of foam that an astronaut can strap themselves to if they need to ride a Crew Dragon capsule home in case of an emergency. Specifically, the pallet seats are reserved for NASA astronauts that hitch a ride to the space station on Russian Soyuz spacecraft, as they have done for years as part of a seat-swapping agreement between the US and Russia. NASA astronaut Don Pettit, for example, is currently on the space station after arriving aboard the Soyuz MS-26 spacecraft on September 11. If the space station is deemed unsafe, however, and Pettit can't access the spacecraft attached to the Russian module, NASA said he has the option to ride home via the visiting SpaceX Crew-9 vehicle on a pallet seat alongside the four astronauts assigned to that vehicle — NASA's Sunita Williams, Butch Wilmore and Nick Hague and Roscosmos cosmonaut Aleksandr Gorbunov. NASA has contingencies in place for crew safety, but the space agency is also grappling with the fact that the leaking Russian module may pose a threat to the safety and longevity of the space station. In its report, the Office of Inspector General notes, "While it is possible for the ISS to function if the hatch (to the affected area) is closed permanently, it could impact cargo delivery because there would be one less cargo delivery port," the report states. "Closing the hatch permanently would also necessitate additional propellent to maintain the Station's altitude and attitude (or orientation)." The space station routinely requires spacecraft attached to it to boost the orbiting outpost in order to maintain its trajectory, preventing Earth's gravity from dragging it back down. Typically, those boosts are performed by docked Russian spacecraft. But NASA has already been testing the use of US spacecraft for that task. The leak issue is flaring up at a critical time for the orbiting laboratory, which NASA hopes will continue to operate with its five partner agencies through at least 2030. In addition to Roscosmos, they include the Canadian Space Agency, European Space Agency and Japan Aerospace Exploration Agency. Russian officials, however, have not committed to the space station beyond 2028 and likely will not give firm answers on Roscosmos' involvement after that time frame until at least 2025, according to the OIG report. The goal for NASA is to continue carrying out essential research on the orbiting laboratory until an alternative space station comes online. The US space agency intends to hand over the duty of creating and operating that new space lab to the private sector — and currently a string of commercial outfits are designing and developing their own platforms. Those companies include the Jeff Bezos-funded Blue Origin and SpaceX partner Vast. The space agency intends to roll out lucrative contracts for the job in 2026. Still, it's not clear whether the commercial destinations will be ready before the space station is forced to retire. "The station is not young," Barratt said. "We will expect to see more wear and tear in various other places." — CNN
