As astronauts complete a delayed spacewalk outside of the International Space Station, NASA and Roscosmos officials said they continue to investigate whether the leaked coolant Soyuz spacecraft can safely return its crew home. On December 22, NASA astronauts Josh Cassada and Frank Rubio successfully completed a spacewalk that lasted seven hours and eight minutes. They installed the fourth of six ISS Roll-Out Solar Array or iROSA panels on the station, which will complement the station’s existing arrays.

The spacewalk was scheduled for December 21, but was delayed as Cassada and Rubio made their final preparations for launch. NASA delayed the spacewalk after concluding that a piece of orbital debris, part of the Frigate upper stage, would fly within half a kilometer of the station, causing a debris avoidance maneuver of the Progress cargo spacecraft docking at the station.

Previously, NASA delayed the spacewalk from 19 December so that Canadarm2’s robotic arm could be used to study the exterior of the Soyuz MS-22 spacecraft docked with the ISS. On December 14, a coolant leak occurred on this spacecraft, causing a delay in the separate spacewalks of Roscosmos cosmonauts Sergey Prokopyev and Dmytro Petelin.

The heads of NASA and Roscosmos said in a teleconference to the media on Dec. 22 during the spacewalk that the investigation into the leak was ongoing. A hole a few millimeters in diameter captures a coolant tube less than a millimeter in diameter, said Serhiy Krikalev, executive director of Roscosmos’ manned spaceflight programs.

“We are currently doing a thermal analysis to see if we can use this vehicle for a nominal crew entry or if we should send a recovery vehicle to the station in the future,” he said.

In the latter case, the Soyuz MS-23 spacecraft will be launched without a crew, which will replace Soyuz MS-22, which delivered Prokopiev, Petelin and Rubio to the station in September. This will serve as a rescue boat for the three ISS crews, while the Soyuz MS-22 will return to Earth without a crew.

Currently, the Soyuz MS-23 is scheduled to perform a crew rotation mission in mid-March. Krykalyov said its launch could be delayed by two or three weeks if necessary. But if it has to be launched without a crew, it’s unclear what this will mean for future crew rotation missions. Only those plans would have to be “corrected,” Krykalyov said.

The cause of the leak is still under investigation, but both Krikalyov and NASA’s ISS program manager, Joel Montalbano, denied a micrometeorite impact from the Geminid meteor shower. In the days following the search, Russian officials suggested that the leak may have been caused by a meteor shower that occurred in mid-December, but offered no evidence to support that conclusion.

Controllers in both Houston and Moscow concluded that the hole was not in the direction of the downpour, but they are still not sure what caused it. “We’re trying to get better video and images of this hole,” Montalbano said. “At this time, we have not confirmed that this is an MMOD, micrometeoroid debris, or any other type of failure.”

The direction of the leak meant that the coolant didn’t contaminate the station’s exterior surfaces, such as solar panels or windows, he said. This was something the controllers checked before Cassada and Rubio went into space.

Montalbano said NASA and Roscosmos coordinated the Soyuz leak investigation closely, including regular talks between them and at the study level. “Teams come and go. We are constantly exchanging data,” he said. “The teams worked together as always.” Source