The Russian module "Zvezda" on the International Space Station (ISS) continues to leak air, in spite of hope, that recent renovations in June 2025 solved the problem last year, which lasts from 2019 year. Module, launched in July 2000 year, is one of the oldest components of the ISS and provides living quarters and a docking port for the Russian Progress and Soyuz spacecraft.
Details of the problem
The leak is localized in the transition chamber (PrK) module "Zvezda", that connects the docking port to the rest of the module. The first signs of the leak were discovered in August 2019 year, and since then, Russian cosmonauts have repeatedly tried to remove it, using tapes, glue and other temporary solutions. In February 2024 year, the leak increased to 1,7 kg of air per day, and in April 2024 year reached its peak in 3,7 kg per day, prompting NASA to classify the problem as the highest risk (5×5 on a scale of probability and consequence). After repairs in June 2025 Roskomos announced the complete elimination of the leak, but long-term observations have shown, that it continues, although at a much lower speed - approx 1,2 kg per day.
NASA and Roskomos did not agree on the cause of the leak and its criticality. Russian experts believe, that the leak is caused by micro-vibrations, which lead to metal fatigue, while NASA points to a combination of factors, in particular residual stresses, properties of materials, pressure and influence of space environment. Both agencies focused on examining the internal and external welds of the module, but the ultimate cause remains unknown.
Impact and measures
The leak does not pose an immediate threat to the seven astronauts aboard the ISS, but forced NASA to delay the launch of the private Axiom Mission 4, scheduled for May 2025 year, due to the discovery of a "new pressure signature" in the Zvezda module after inspections. Now the hatch to the transition chamber is being closed, when access to Progress ships is not required, to minimize air loss. In case, if the leak becomes unmanageable, the hatch can be permanently closed, which will lead to the loss of one of the four docking ports of the Russian segment, making it difficult to deliver cargo and will require additional fuel to maintain the ISS orbit.
NASA and Roskomos are working together to solve the problem, involving independent experts from academia and industry. NASA is taking conservative measures, closing the hatch between the US and Russian segments during work in PrK, to isolate potential risks. In August 2024 year, the risk of leakage was assessed as the highest, but after the repairs, its influence decreased, although the problem remains serious.
The context and future of the ISS
ISS, which is in orbit at an altitude of about 400 km already over 25 years, faces numerous problems due to aging equipment. In addition to the leak in the Zvezda module, the Russian segment experienced other incidents, in particular, the coolant leak from the Soyuz MS-22 spacecraft in December 2022 year, ammonia from Progress 82 in February 2023 year and a leak in the "Science" module in October 2023 year. These events, along with geopolitical tensions over the war in Ukraine, made cooperation between NASA and Roskomos difficult. Russia plans to withdraw from the ISS program after 2028 year and develop its own orbital station, while NASA plans to remove the ISS from orbit at 2030 year with the help of SpaceX.
Source: https://spacenews.com