For when the International Space Station ceases to be operational in 2030they will have passed 32 years since the first module was put into orbit and 30 since the Zvezda service module joined the station. With the time that has passed since then, it is logical that the impressive 419-ton structure has some ailments. It’s what’s happening in the Russian orbital segment of the ISS with the Russian Zvezda module. But the main problem is that the POT and Roscosmosthe Russian space agency, They disagree on the causes and risks posed by the small air leaks Zvezda is experiencing. in the transfer tunnel for 5 years and which are increasing at an increasing rate.
‘US and Russian officials do not have a common understanding of what the most likely root cause is nor the seriousness of the consequences of these leaks‘, he recently pointed out Bob Cabanaretired NASA astronaut and president of the NASA International Space Station Advisory Committee since the beginning of this year.
The transfer tunnel, known by its Russian acronym PrKconnects the Zvezda module to a docking port used by manned spacecraft Soyuz and replenishment ships progress. The air leaks started in September 2019 and Russian cosmonauts have repaired the cracks and temporarily reduced its rate several times since then. In February, filtered air increased again to 1.09 kg per day and in April it increased to 1.68 kg per day.
This led NASA to raise to the highest level of riskin the risk management system of the space station program, the transfer tunnel leak. This ‘5×5’ system classifies the probability and consequences of risks. In June, it was reported that leaks are rated 5, the highest level, on both counts. In September, NASA said the latest round of repairs reduced the leak rate by a third, but without eliminating the problem.
‘The Russian position is that the most likely cause of the cracks in the PrK is the high cyclic fatigue caused by microvibrations. NASA believes that the cracks in PrK likely have multiple causes, including pressure and mechanical stress, residual stress, material properties and environmental exposures‘, Cabana explained.
Roscosmos has shared metal samples, welds and research reports with NASA to assist in the study of cracks and leaks. In a report released in September, NASA’s inspector general noted that the ISS Vehicle Office at the Johnson Space Center in Houston said the leaks ‘do not pose an immediate risk to the structural integrity of the station’. This is because they have implemented measures to protect the entire station in the event of a structural failure of the PrK.
How, module after module, the International Space Station was assembled in orbit.pic.twitter.com/xKFdLWdEJF
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space station crew keeps the hatch leading to the PrK closed when they do not need access to the Progress freighter docked at the other end of the transfer tunnel. Russian cosmonauts must open the hatch to disembark supplies from the Progress or load garbage onto the ship for disposal.
However, NASA and Roscosmos They disagree on when the leak rate would become unsustainable. When that happens, the space station crew will have to Permanently close the hatch to seal the PrK and prevent a major failure from affecting the rest of the complex.
This decision would prevent the use of one of the four Russian docking ports of the space station. As a precaution, the space station crew is also closing the hatch separating the American and Russian sections of the station when cosmonauts work in the PrK.
‘The Russians believe that continued operations are safe, but they cannot prove it to our satisfaction. And the Americans believe it is not safe, but we cannot prove it to the satisfaction of the Russians,’ Cabana said. ‘So, while the Russian team continues to search for and seal the leaks, (Roscosmos) does not believe that a catastrophic breakup of the PrK is realistic. And NASA has raised concerns about the structural integrity of PrK and the possibility of catastrophic failure.‘
Michael Barratta NASA astronaut who returned from the space station last month, has noted that ‘the way it has affected us, mainly, is that when they go in and open that to unload a cargo vehicle that is docked, They also take the time to inspect and attempt repairs when they can.. We have taken a very conservative approach in closing the hatch between the American and Russian sides during those periods. It’s not a comfortable thing, but it’s the best agreement between all the smart people on both sides, and it’s something we live with and adapt to as a crew.’
NASA has hired a team of independent experts to evaluate the cracks and leaks and help determine the cause of them. ‘This is an engineering problem, and good engineers should be able to agree on this’Cabana explained.