Updated 2:30 p.m. Eastern after NASA/Roscosmos briefing.
SEATTLE — Russia will launch a Soyuz spacecraft without a crew to the International Space Station in February after concluding a damaged Soyuz spacecraft docked there cannot safely return its crew to Earth.
In a statement Jan. 11, the Russian space agency Roscosmos announced that the Soyuz MS-23 spacecraft will launch to the ISS without a crew Feb. 20. It will replace the Soyuz MS-22 currently docked at the station, which will return to Earth uncrewed.
Soyuz MS-22 suffered a coolant leak Dec. 14 as Russian cosmonauts Sergey Prokopyev and Dmitri Petelin were preparing for a spacewalk. The spacewalk was called off as coolant spewed from the leak for hours.
During a call with reporters, NASA and Roscosmos officials said that a Russian state commission concluded that, because of the lost coolant, the spacecraft’s radiator could no longer cool the spacecraft on its own. During the spacecraft’s return to Earth, temperatures inside the spacecraft could rise to more than 40 degrees Celsius with high humidity, said Sergei Krikalev, executive director of human spaceflight programs at Roscosmos.
“The main problem to land the current Soyuz with a crew would be the thermal condition because we lost heat rejection capability,” he said. “The crew may overheat with high temperature and high humidity.”
Under the revised plan, Soyuz MS-23 will launch Feb. 20 without a crew but with some cargo. After docking with the station, the crew will spend one to two weeks transferring equipment, like customized seat liners, from Soyuz MS-22 to MS-23, while placing in Soyuz MS-22 other cargo that can be returned to Earth that is not sensitive to overheating. Soyuz MS-22 will then undock and attempt a landing back in Kazakhstan in automated mode.
Soyuz MS-23 was previously scheduled to launch in March to send Roscosmos cosmonauts Oleg Kononenko and Nikolai Chub and NASA astronaut Loral O’Hara to the station. Under the new plan, Prokopyev, Petelin and Rubio will remain on the ISS until later this year.
Krikalev said it was premature to estimate how long their stay on the ISS will be extended beyond “several” months. “What will be the exact date we will send replacements for them is not decided yet,” he said, and noted later that no future missions had been canceled, only delayed.
Joel Montalbano, NASA ISS program manager, said that NASA will review its schedule of upcoming missions, including the Crew-6 Crew Dragon mission scheduled to launch in February, in light of the change in Russian plans. He said it would be a “couple of weeks” before the agency decided how that schedule might change, but added there would be no changes to the crew for Crew-6.
Krikalev and Montalbano said they are looking at options of what to do if an emergency required an evacuation of the ISS before Soyuz MS-23 arrived. That could include flying one or more Soyuz crewmembers on the Crew Dragon spacecraft docked to the ISS in place of cargo. The rest could return on Soyuz MS-22, with less of a risk of overheating because of the recued crew size.
“SpaceX has been extremely responsive to this request,” Montalbano said of studies on accommodating additional personnel on the Crew Dragon. “All this is only for an emergency, only if we have to evacuate ISS. That’s not the nominal plan.”
Krikalev said an investigation concluded that the hole in the radiator was most likely caused by a tiny micrometeoroid hitting the spacecraft at about seven kilometers per second. Ground tests confirmed that hypothesis, he said, adding that it was unlikely to be an orbital debris impact because of the high relative speed of the impact meant that the object would have been traveling too fast to be in a stable orbit.
Montalbano agreed. “Everything does point to a micrometeoroid impact,” he said, although an impact linked to the Geminid meteor shower was ruled out based on the location of the impact versus the director of the shower. “Nothing was off-nominal in the manufacturing of the vehicle.”
Krikalev said that while a design flaw does not appear to be the cause of the hole, technicians “double-checked, triple-checked” the radiator on Soyuz MS-23 as a precaution. “We don’t have any issues with the next Soyuz.”
Engineers also ruled out attempting to repair Soyuz MS-22 in orbit. Krikalev said the Soyuz was not in a location that spacewalking cosmonauts could easily reach, and that attempting to refill the radiator with coolant and fixing the hole would be difficult and risky for spacewalkers. “There’s much less risk to just replace the vehicle.”
Krikalev and Montalbano said that they have been in regular contact with the ISS crew to inform them about the status and outcome of the investigation, and that Prokopyev, Petelin and Rubio were all in good health and able to handle and extended stay. “I may have to fly some more ice cream to reward them,” Montalbano said.