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ISS Soyuz inspection
A robotic arm inspects the Soyuz MS-22 spacecraft after the Soyuz suffered a coolant leak December 14. (credit: NASA TV)

Persistent cooperation on the space station


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Ever since Russia started an all-out invasion of Ukraine last February, the space community has wondered what it would mean for the future of the International Space Station. Russia is an essential partner on the station, but at the same time Russia and the West were rapidly unwinding cooperation elsewhere, from commercial launch to the Russian-European ExoMars mission.

However, the real test of a relationship is not when things are going well but instead when they are not.

NASA officials, including administrator Bill Nelson, have emphasized it has been business as usual on the station, noting ongoing “professional” cooperation between Houston and Moscow. And, despite some statements that Russia would withdraw from the station as soon as 2024 (see “ISS in the balance,” The Space Review, August 1, 2022), that has been the case. Station operations have been, at least from the outside, unaffected by the conflict, and NASA and Roscosmos have even deepened their cooperation by bartering seats between Soyuz and Crew Dragon vehicles, flying a cosmonaut on Crew-5 in October in exchange for an astronaut on Soyuz MS-22 the previous month.

However, the real test of a relationship is not when things are going well but instead when they are not. That happened last month when that Soyuz spacecraft docked to the ISS suffered a coolant leak that made it unable to return its three-person crew to Earth. In the weeks that followed, that incident has not revealed cracks in the US-Russian relationship in space, as fraught as it is on Earth, but instead showed it to be remarkable strong.

The incident that triggered the problem had fortuitous timing. Russian cosmonauts Sergey Prokopyev and Dmitri Petelin were preparing for a spacewalk on the evening of December 14 (US time) that, like other Russian spacewalks at the station, would be carried on NASA TV. But when people tuned to NASA TV, they saw instead what appeared to fluid, later identified as coolant, spraying from the Soyuz. The spacewalk, of course, was called off.

Russian officials said in the days following the incident that an object likely struck the service module of the Soyuz, hitting the radiator and puncturing a coolant line. Some went so far to say the impact was caused by a micrometeoroid linked to the Geminid meteor shower peaking around that time, but offered little, if any, evidence to support that assertion.

A bigger question, though, was the state of the Soyuz spacecraft. The leak continued for hours, until all the coolant leaked out. Without it, it was not clear if the Soyuz could safely return home in March, as originally planned, with Prokopyev, Petelin, and NASA’s Frank Rubio. If not, Roscosmos and its ISS partners needed a plan B.

“The teams are going back and forth. We’re constantly exchanging data,” Montalbano said. “The teams have worked together as they always have.”

In a call with reporters December 22, top NASA and Roscosmos officials said they were still studying the health of Soyuz MS-22 and what to do if it could not safely return its crew. “Now we are doing thermal analysis to see if we can use this vehicle to do a nominal reentry with a crew,” said Sergei Krikalev, executive director of human spaceflight programs at Roscosmos, “or if we need to send a rescue vehicle to the station in the future.”

In the latter case, Russia would launch Soyuz MS-23 without a crew, while Soyuz MS-22 would return to Earth without the crew. That would mean, though, that Prokopyev, Petelin, and Rubio would have to extend their stay on the ISS, since their replacements had planned to launch on Soyuz MS-23 in March.

Joel Montalbano, NASA ISS program manager, emphasized that the NASA and Roscosmos teams were working well together as they figured out what happened to Soyuz MS-22 and what to do with it. “The teams are going back and forth. We’re constantly exchanging data,” he said when asked if he thought NASA has sufficient insight into the investigation. “The teams have worked together as they always have.” (The only issue was a poor audio connection on the call that made it difficult for reporters to hear Krikalev.)

Krikalev and Montalbano reconvened with the media January 11 to reveal the outcome of the investigation. They had concluded that a micrometeoroid—not linked to the Geminids, since it was from the wrong direction—hit the radiator and produced a hole two millimeters in diameter, allowing the coolant to leak out.

Krikalev said groundbased testing concluded the hole was made by an impact of an object one millimeter across traveling at a relative velocity of seven kilometers per second. That speed and direction, he said, ruled out an orbital debris impact. “Some other object on this orbit cannot exist because it has so high velocity that it couldn’t stay on this orbit,” he explained.

Montalbano, who in the earlier call said it was too soon to know what caused the leak, had accepted that explanation. “We’ve done a lot of imagery assessments of the area of interest, and everything does point to micrometeroid debris.”

More importantly, the investigation ruled out a manufacturing flaw with the Soyuz, which could also have been an issue with the next Soyuz spacecraft. Krikalev said that, to be sure, technicians “double-checked, triple-checked” the radiator on Soyuz MS-23 as it was being prepared for launch. “We don’t have any issues with the next Soyuz.”

“This particle was an extremely unlikely hit,” he said, hitting not just the radiator but the coolant pipe. Repairing it in orbit, he added, was not an option given the inaccessibility of the damage for spacewalkers and difficulty trying to repair it. “There’s much less risk to just replace the vehicle.”

That damaged radiator, Roscosmos concluded, could not keep a three-person crew safe on even the relatively short trip back to Earth. Temperatures inside the capsule would soar to more than 40 degrees Celsius, along with high humidity. “The crew may overheat with high temperature and high humidity,” Krikalev said.

At the briefing, officials laid out their plan B. On February 20, Soyuz MS-23 will launch to the station without a crew, docking two days later. (It will carry some cargo in place of people.) The Soyuz MS-22 crew will transfer equipment, like their custom-fitted seat liners, into Soyuz MS-23, while moving some cargo into Soyuz MS-22 that can return to Earth without being affected by high temperatures. About one to two weeks after arrival, Soyuz MS-22 will undock without a crew, returning to land in Kazakhstan.

“On the returning Soyuz, we’ll be taking some temperature measurements to measure how the vehicle does in this scenario such that, if we ever had a need in the future, we have some additional data,” Montalbano said Soyuz MS-22. “We’re going to fully use this vehicle all the way until it lands back on Earth.”

“At this point, we have calculations and thermal scenarios, but we want to prove these calculations with the result of a real test,” Krikalev added.

That decision, while not unexpected, does have implications for the ISS program. One is that it will extend the stay of Prokopyev, Petelin, and Rubio by several months. Soyuz MS-23 was to deliver Oleg Kononenko and Nikolai Chub of Roscosmos and Loral O’Hara of NASA to the station, but they will likely have to wait until the fall when Soyuz MS-24 was ready.

“This particle was an extremely unlikely hit,” Krikalev said.

Both NASA and Roscosmos were vague about schedules, saying only that the three Soyuz crewmembers would spend “several” more months. At a January 17 briefing about an upcoming spacewalk by NASA’s Nicole Mann and JAXA’s Koichi Wakata, NASA ISS operations integration manager Dina Contella said the three would likely be there until September, spending about a year in space.

Krikalev and Montalbano said they had talked with Prokopyev, Petelin, and Rubio about their extended stay and none had any issues about it. “I may have to fly some more ice cream to reward them,” Montalbano quipped.

Moving up Soyuz MS-23’s launch affected the Crew Dragon Crew-6 launch, which was scheduled to launch around February 20. NASA later announced that the mission is now scheduled to launch no earlier than February 26.

What if, though, something happened on the ISS between now and late February that required an evacuation of the station? Krikalev and Montalbano said in January that they looked at scenarios that might involve having one or more Soyuz crewmembers ride home in Crew Dragon. NASA had earlier acknowledged it had talked to SpaceX about roles it could play, but had left open whether that involved using the current Crew Dragon at the station or flying up a new one.

Montalbano said they had ruled out sending up another Crew Dragon, uncrewed, to return the Soyuz crew, citing the “tailored equipment” needed for each spacecraft. “The quickest way to get to a safe configuration is get that replacement Soyuz up there.” However, he said that NASA would look into a “launch on need” scenario once both Crew Dragon and Boeing’s CST-100 Starliner enter service such that, if there is a problem with one vehicle, another could be quickly launched.

Contella said that station officials ultimately decided to move Rubio’s Soyuz seat temporarily into Crew Dragon, placing in a cargo stowage area. In an emergency he would return on Crew Dragon while Prokopyev and Petelin use the Soyuz. “We think that will take out some of the heat load that’s in the Soyuz spacecraft and will help the overall posture for us,” she said. That will last only until Soyuz MS-23 arrives at the station.

Both NASA and Roscosmos said they did not consider Soyuz MS-23 a “rescue Soyuz” even though they had used similar terminology in an earlier call. “We’re not calling a rescue Soyuz. Right now the crew is safe on board space station,” Montalbano said. “I’m calling it a replacement Soyuz.”

“I completely agree with this terminology, saying ‘replacement Soyuz,’” Krikalev said.

“We’re not calling a rescue Soyuz. Right now the crew is safe on board space station,” Montalbano said. “I’m calling it a replacement Soyuz.”

The two appeared in complete agreement overall in the call, suggesting any differences in opinion had been worked out, or at least papered over, well in advance. The January 11 call took place from Moscow, with Montalbano visiting for the Russian state commission meetings into the incident and how to proceed.

That cooperation is hopeful, but looks increasing anomalous in today’s geopolitical environment. The war in Ukraine continues with no sign of a battlefield or negotiated settlement, and cooperation between Russia and the West in space is now largely nonexistent outside of the ISS.

That ISS cooperation remains strong, as the reaction to the damaged Soyuz shows. The question is whether it is a flickering candle of hope for a better future or a dying ember of a past era of cooperation that will die out when the station is retired by the end of the decade.


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