Four weeks ago, as two Russian cosmonauts were preparing to conduct a spacewalk, a Soyuz spacecraft attached to the International Space Station started to leak uncontrollably.

The spacewalk was canceled, and since then, Russian and US spaceflight engineers have been analyzing the cause of the leak and its implications for future travel to and from the large laboratory in low-Earth orbit. They have now deduced that a micrometeoroid or small piece of orbital debris struck the external cooling loop of the Soyuz spacecraft, causing all of its coolant to vent into space, and put a recovery plan into place.

Although there were no immediate threats to the seven astronauts on board the space station, there was the not-insignificant question of how the three people who had ridden on board this Soyuz MS-22 spacecraft into orbit— cosmonauts Sergey Prokopyev and Dmitri Petelin and NASA's Frank Rubio—would subsequently get home.

Now, we finally have an answer. On Wednesday, officials from NASA and the Russian state-owned space corporation, Roscosmos, said a replacement Soyuz spacecraft will launch to and autonomously dock with the station next month. The crew that would have flown in the damaged Soyuz MS-22 vehicle will instead fly home in this Soyuz MS-23 spacecraft later in 2023. The leaky Soyuz MS-22 vehicle will make an autonomous return to Earth, bereft of crew, likely in March.

The executive director for human spaceflight at Roscosmos, Sergei Krikalev, said during a teleconference with reporters Wednesday that he is confident the cooling system was damaged by an object approximately 1 mm in diameter. This assessment was based on high-resolution imagery of the damage site and ground tests to recreate the problem. It cannot be determined whether this was a tiny meteor fragment or one of the countless pieces of space junk whizzing around low-Earth orbit.

Russian officials believe Soyuz MS-22 is still flyable in an emergency. However, without an efficient way to radiate heat during a six-hour return to Earth, the interior of the spacecraft could overheat. This could damage the flight computers used to set a precise return trajectory and put the crew at risk. Krikalev said the temperature inside Soyuz MS-22 could reach the low 40s Celsius (105–110° F) during its return to Earth. The concern about crew member health is as much about humidity as it is temperature in such a scenario.

Russian and NASA officials have been looking at contingency plans in the event of an emergency on the space station between now and when Soyuz MS-23 arrives in February. In such a contingency, one or more of the MS-22 crew members could find safe harbor and potentially return to Earth inside the Crew-5 Dragon currently attached to the space station. That vehicle nominally carries four astronauts, but it could bring more people home.

"SpaceX has been extremely responsive," said NASA's International Space Station Program Manager Joel Montalbano. "But all of this is only for an emergency, only if we have to evacuate the ISS. We’re always looking at what we can do to ensure the safety of the crew. Nominally, the plan is for when Crew-5 comes home, they come home with four people."

The crew of Soyuz MS-22 launched to the space station in September. They had been due to return to Earth in March before the dramatic coolant leak. Now their mission will be extended for "several" months, Krikalev said. It's possible the three astronauts, including NASA's Frank Rubio, will now not return to Earth until September 2023, when Soyuz MS-24 is ready to bring the next Russian crew rotation to orbit. This likely means that the crew that had been due to launch this spring, Russia's Oleg Kononenko and Nikolai Chub and NASA's Loral O'Hara, will wait until this fall to fly their mission.

"The awesome thing about our crews is that they’re willing to help with whatever we ask," Montalbano said. "They will stay until a September launch date if necessary. The crews are excited to be in space."

Since the coolant leak, Russian and US engineers and managers have collaborated smoothly, Montalbano said. It's remarkable that NASA and Roscosmos are still working exceptionally well together when it comes to ISS operations, given all that has happened since Russia's invasion of Ukraine. This bodes well for the continued operation of the space station partnership for the remainder of the 2020s, despite hostilities on Earth.