Uncrewed Soyuz MS-23 “rescue” mission arrives at ISS

by Tyler Gray

The Russian space agency, Roscosmos, docked an uncrewed Soyuz spacecraft to the International Space Station (ISS) as part of a plan to replace the stricken Soyuz MS-22 vehicle. The MS-23 mission launched atop a Soyuz-2.1a rocket from Site 31/6 at the Baikonur Cosmodrome in Kazakhstan on Friday, Feb. 24, at 00:24 UTC. It docked without issue on Saturday.

This was the second Soyuz rocket launch of 2023 and the first flight for the Soyuz spacecraft this year.

The primary aim of the Soyuz MS-23 mission is to replace the existing Soyuz MS-22 spacecraft, which suffered technical problems while docked to the Russian segment of the International Space Station.

Soyuz MS-22 launched from Baikonur on Sept. 21, 2022, with a three-person crew: Sergey Prokopyev and Dmitry Petelin of Roscosmos, and NASA’s Francisco Rubio. The addition of Rubio to the flight was done as part of a crew swap exchange agreement between the American and Russian space programs.

The launch took place with no apparent problems. A little over three hours later, the MS-22 spacecraft arrived at the International Space Station and docked at the nadir, or Earth-facing, port of the Rassvet cargo module. This began what had been planned as a nominal 188-day mission.

On Dec. 15, just before Prokopyev and Petelin were about to commence a scheduled spacewalk, a visible leak of particles from the Soyuz spacecraft’s aft instrument module was noticed by ISS mission controllers in both Houston and Moscow. An indication of pressure loss aboard the vehicle’s external radiator was also observed.

The spacewalk was subsequently canceled, and soon after, Russian cosmonaut Anna Kikina took control of the European Robotic Arm attached to the Nauka Multipurpose Laboratory Module. Using the arm, she was able to help controllers closely inspect the spacecraft and the site of the leak using a camera.

These investigations found a 0.8-millimeter-diameter hole in the external radiator on the Soyuz service module, which allowed coolant to flow out and escape into space. According to Roscosmos, the damage was caused by an MMOD (micro-meteorite/orbital debris) impact.

Working groups involving NASA and Roscosmos eventually determined that the Soyuz MS-22 spacecraft would be unable to perform a crew return safely and that the next available Soyuz vehicle would be launched to the ISS uncrewed as a replacement.

This Soyuz replacement procedure is similar in nature to one performed in 1979 when Soyuz 34 was launched without a crew to replace Soyuz 32 at the Salyut 6 space station. This came after the Soyuz 33 spacecraft had failed to dock with Salyut 6 and subsequently experienced propulsion issues during its return to Earth, which raised concerns about the Soyuz 32 spacecraft then in orbit. The uncrewed launch of Soyuz 34 gave the station’s crew a reliable means of return to Earth, while Soyuz 32 returned to Earth without its crew aboard.

Launch Preparations

Before the problems with the Soyuz MS-22 spacecraft became apparent, Soyuz MS-23 was to have flown the next crew rotation mission to the ISS and had arrived at the technical complex at the Baikonur Cosmodrome to begin processing in September 2022. The spacecraft passed vacuum chamber testing in late January and was successfully integrated with the third stage of its Soyuz-2.1a rocket in early February in preparation for launch.

Liftoff had been scheduled for no earlier than Feb. 20, but this was postponed due to an observed coolant leak aboard the Progress MS-21 cargo resupply vessel, then docked to the zenith, or space-facing, port of the station’s Poisk module.

Further inspections of the MS-23 spacecraft showed no defects, and preparations soon resumed. The vehicle was encapsulated within its payload fairing on Feb. 17, and integration with the rest of the Soyuz launch vehicle occurred three days later. Rollout to the launch pad at Site 31/6 took place the following day.

Since Soyuz MS-23 flre without crew on board, much like a Progress mission, the spacecraft is conducting its mission autonomously until its docking with the ISS. Roscosmos is using the opportunity to deliver 429 kg of equipment and supplies to the station’s crew.

Following the successful launch, the MS-23 spacecraft separated from its Soyuz launch vehicle and began a two-day journey to reach the ISS. This culminated in docking to the zenith port of the Poisk module — vacated by the departure of Progress MS-21 on Feb. 18 — at 01:01 UTC on Feb. 26.

Once the crew’s seat liners have been transferred to Soyuz MS-23, the Soyuz MS-22 spacecraft will undock and begin its return journey to Earth uncrewed. Its departure is expected in late March.

(Lead image: The Soyuz MS-23 mission lifts off from Baikonur. Credit: Roscosmos)

Related Articles