This undated handout photo taken by Russian cosmonaut Sergei Korsakov and released by Roscosmos State Space Corporation shows a Soyuz capsule of the International Space Station during its fly.Sergei Korsakov/The Associated Press
A coolant leak lasting for at least three hours Wednesday night aboard a Russian Soyuz space capsule docked to the International Space Station could have been caused by a tiny meteoroid strike, a senior Russian space official said Thursday.
NASA and Russia’s space agency, Roscosmos, said no astronauts were endangered by the leak, which forced mission control officers in Moscow to call off a planned spacewalk by two cosmonauts as fluid sprayed outward into space, as seen on live video during a NASA webcast.
“The cause of the leak in Soyuz MS-22 could be a micrometeoroid hitting the ship’s radiator,” Sergei Krikalev, head of human spaceflight at Roscosmos, said in a statement posted on Telegram.
Tiny micrometeoroids, or space rocks, most of them as small as a grain of sand, are a normal part of the space environment as they zip through the solar system in random directions and typically cause little or no substantive damage to the ISS and other spacecraft protected by advanced shielding.
Russian officials are leading an investigation into the cause of the leaky fluid, which spewed from a radiator cooling loop on the exterior of Russia’s Soyuz MS-22 spacecraft starting around 7:45 p.m. ET on Wednesday (0045 GMT Thursday), NASA said. The liquid coolant is used to regulate temperatures on the capsule.
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NASA said MS-22′s temperatures “remain within acceptable limits.” Neither the U.S. space agency nor Roscosmos explained the spacecraft’s temperature range, how close the vessel was to reaching those limits, how much coolant escaped or what time the leakage stopped.
The same Soyuz spacecraft ferried cosmonauts Sergey Prokopyev and Dimitri Petelin, along with NASA astronaut Frank Rubio, to the space station in September, marking the first joint U.S.-Russian flight under a renewed agreement between NASA and Roscosmos allowing commingled crews on journeys to and from the space station. Mr. Prokopyev and Mr. Petelin were the two suited up for a six-hour spacewalk when the coolant leak began.
The space station, a football-field-sized laboratory housing astronauts on a continuous basis for more than two decades, has a current crew of seven. The four other members of the latest expedition arrived in October aboard a SpaceX Crew Dragon capsule. That crew includes two NASA astronauts, a Japanese astronaut and one cosmonaut.
The leak raised immediate questions about whether MS-22 will be able to return its three-man crew to Earth in March, 2023, as originally planned, or if NASA and Roscosmos will need to pursue contingency plans.
The spacewalk planned for Wednesday night was postponed once before, in late November, because of faulty cooling pumps in the cosmonauts’ spacesuits. And in August, a Russian spacewalk was cut short by a battery issue with one of the cosmonauts’ spacesuits.