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Soyuz MS-27 arrives at ISS

The first of two Soyuz crew vehicles scheduled to go to the International Space Station, ISS, in 2025 launched from Baikonur Cosmodrome in Kazakhstan on April 8. Soyuz MS-27 docked to the station's Prichal module three hours later.

Previous mission: Soyuz MS-26

Soyuz MS-27 mission at a glance:

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The primary crew of the Soyuz MS-27 spacecraft inside the Descent Module during practice: Jonathan (Jonny) Kim, Sergei Ryzhikov, Aleksei Zubritsky.

The Soyuz MS-27 mission marked the extension of the Russian ISS shifts from around six months to roughly eight months in order to cut the number of Soyuz vehicles flying to the station from two per year to 1.5 annually.

The launch was originally planned on March 20, 2025, but by the end of November 2024, it was re-scheduled for March 16, 2025. Before the end of 2024, the mission shifted to April 8, 2025.

On Aug. 21, 2024, Roskosmos announced that Russian cosmonauts Sergei Ryzhikov and Aleksei Zubritsky would be accompanied by NASA astronaut Jonathan Kim aboard Soyuz MS-27. The US astronaut will fly under an exchange agreement which also put Roskosmos cosmonaut Kirill Peskov on NASA's Commercial Crew 10, then scheduled for launch aboard a Crew Dragon spacecraft in February 2025. Russian cosmonauts Sergei Kud'-Sverchkov and Sergei Mikaev, along with NASA astronaut Christopher Williams were assigned to a back-up crew.

Soyuz MS-27 launch campaign

Soyuz MS-27 was delivered to Baikonur in early December 2024 and its processing for launch started in mid-January 2025. The booster stages of the Soyuz-2-1a rocket for the mission were integrated into a cluster at the vehicle assembly building at Site 31 by the end of Jan. 31, 2025.

On March 4, 2025, Roskosmos reported completion of vacuum chamber tests with Soyuz MS-27 which was expected to be followed with checks of the Integrated Propulsion System, KDU (INSIDER CONTENT), the Descent Control System, SIOS, test activation of the onboard computers and radio system and filling of the Thermal Control System, SOTR (INSIDER CONTENT), with coolant fluids. The solar panels of Soyuz MS-27 were deployed and tested to exposure to light by March 17, 2025.

On March 24 in Baikonur, the primary and back-up crews tried their Sokol-KV2 pressure safety suits and conducted familiarization training inside the flight-ready Soyuz MS-27 spacecraft, after which it was sent to a fueling station. Fueling operations were completed on March 25 and the crew vehicle was returned to Site 254 for the loading of cargo, hatch pressure checks, installation of the exterior thermal protection layers and weighting. On March 27, 2025, the spacecraft was integrated with the launch vehicle adapter.

On April 2, 2025, members of Expedition-73 conducted their final training inside the flight-ready Soyuz MS-27, before the primary crew would board it on the launch day.

On April 3, the assembly of the payload section with the Soyuz MS-27 was completed and it was transported from spacecraft processing building at Site 254 to the vehicle assembly building at Site 31 for integration with the Soyuz-2-1a rocket, which was completed on April 4.

The launch vehicle with the spacecraft was rolled out to the launch pad at Site 31 on the morning of April 5, 2025.

Soyuz MS-27 lifts off

A Soyuz-2-1a rocket with the Soyuz MS-27 spacecraft lifted off as scheduled on April 8, 2025, at 08:47:15.039 Moscow Time (1:47 a.m. EDT) from Site 31 in Baikonur.

Propelled by the simultaneous thrust of the four engines of the first stage and the single engine of the second stage, the vehicle headed almost exactly east to align its ascent trajectory with an orbital plane inclined 51.6 degrees toward the Equator. Slightly less than two minutes into the flight (at L+113.50 seconds; 08:49:08 Moscow Time), at an altitude of around 45 kilometers and a velocity of 1.75 kilometers per second, the ship's main emergency escape rocket jettisoned, followed by the separation of the first stage one second later. The emergency escape rocket and the four boosters of the first stage were expected to impact the ground 330 and 350 kilometers downrange from the launch site respectively.

Around 40 seconds after the first stage separation, as the vehicle exited the dense atmosphere at an altitude of 79 kilometers and a velocity of 2.2 kilometers per second, the payload fairing protecting the spacecraft split into two halves and fell away at 08:49:48 Moscow Time. They were projected to fall 500 kilometers downrange from the launch site.

In the meantime, the second (core) stage of the rocket continued firing until 4.8 minutes into the flight (L+287.70 seconds). Moments before the second stage completed its work, the four-chamber engine of the third stage ignited, firing through the lattice structure connecting the two stages. The second stage then shot down its engine and separated at 08:52:00 Moscow Time. Moments after the separation of the core booster at an altitude of 157 kilometers and a velocity of 3.8 kilometers per second, the aft skirt of the third stage split into three segments and separated as well (at L+296.31 seconds). The second-stage booster and the sections of the aft skirt were projected to impact the ground 1,550 and 1,570 kilometers downrange from the launch site respectively.

Following the 8-minute 49-second climb to orbit, the propulsion system of the third stage was cut off (at L+526.22 seconds), releasing Soyuz MS-27 into an initial orbit three seconds later (at L+529.52 seconds; 08:56:05.769 Moscow Time). The launch targeted the 242 by 200-kilometer orbit with an inclination 51.67 degrees toward the Equator.

Rendezvous and docking operations

At the liftoff of Soyuz MS-27, the ISS was in a 415.139 by 437.870-kilometer orbit, 400 miles behind the crew vehicle, but the station flew over Baikonur just seconds later and overtook the transport ship by the time it reached orbit in less than nine minutes.

Soyuz MS-27 entered orbit just 14.6 degrees away from the ISS in the phasing angle or 1,008 miles behind the outpost, which made it possible to perform a rendezvous with the station after a more than three-hour, two-orbit autonomous flight of the crew vehicle.

According to the Russian mission control, between 09:01 and 09:08 Moscow Time, Soyuz MS-27 was scheduled to perform tests of the Kurs rendezvous system and the Motion Control and Navigation System, SUDN. Then, between 09:10 and 09:13, the ship's docking mechanism was expected to extend its probe into the operational position. Around 25 minutes after reaching orbit, the crew vehicle was to begin rendezvous maneuvers with the station to enter the 355.652 by 426.1-kilometer intercept orbit during the second revolution around the Earth.

As usual, the final autonomous rendezvous process included six firings of the propulsion system (INSIDER CONTENT), which had the following timeline during the Soyuz MS-27 mission:

According to the Russian mission control in Korolev, the autonomous rendezvous of Soyuz MS-27 on April 8, 2025, had the following timeline:

• 09:42:03 Moscow Time: Beginning of autonomous rendezvous with the ISS;
• 10:31:03 Moscow Time: Activation of the Kurs rendezvous system (INSIDER CONTENT) aboard the Zvezda Service Module, SM;
• 10:32:03 Moscow Time: Activation of the Kurs rendezvous system aboard Soyuz MS-27;
• 11:42 — 11:49 Moscow Time: Fly-around of the station;
• 11:49 — 11:53 Moscow Time: Station-keeping of the spacecraft near ISS before final approach;
• 11:53 – 12:04 Moscow Time: Final approach to the Prichal Node Module, UM;
• 12:04:27 Moscow Time: Contact.

Slightly ahead of schedule, Soyuz MS-27 began a 55-degree flyaround of the ISS from a distance of around 400 meters to align itself with the nadir (Earth-facing) docking port of the Prichal Node Module, UM, a part of the Russian ISS Segment.

Soyuz MS-27 was scheduled to dock with Prichal on April 8, 2025, at 12:04 Moscow Time (5:04 a.m. EDT), but the actual contact between the two vehicles took place at 11:57:45 Moscow Time (4:57 a.m. EDT) over Western Russia, according to NASA. The hooks in the docking interface between the spacecraft and the station were closed at 12:03:40 Moscow Time, completing the docking process.

The hatch opening was scheduled for 14:20 Moscow Time (7:20 a.m. EDT) on April 8, 2025, after the pressurization of the newly formed docking interface and a series of air leak checks. The hatch on the side of the Prichal module was opened around 14:10 Moscow Time and the hatch on Soyuz was opened at 14:27:31 Moscow Time (7:27 a.m. EDT) on April 8.

Aboard the station, the three members of the Soyuz MS-27 crew joined the seven other members of Expedition 72: NASA astronauts Nichole Ayers, Anne McClain and Don Pettit, a Japanese astronaut Takuya Onishi and three Roskosmos cosmonauts: Aleksei Ovchinin, Kirill Peskov and Ivan Vagner.

Following an 11-day handover operation, Soyuz MS-26 will depart the ISS on April 19, 2025, with Ochinin, Vagner and Pettit onboard, marking the end of Expedition 72 and the start of Expedition 73 on the station.

The Soyuz MS-27 crew is scheduled to remain aboard the ISS until December 2025.

Soyuz MS-27 crew members:

This page is maintained by Anatoly Zak; last update: April 11, 2025

Page editor: Alain Chabot; last edit: April 7, 2025

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Soyuz MS-27 during pre-launch preparations at the spacecraft processing building at Site 254 in Baikonur. Click to enlarge. Credit: Roskosmos

Soyuz MS-27 is being prepared for integration with its payload fairing. Click to enlarge. Credit: Roskosmos

Launch vehicle with Soyuz MS-27 rolls out from vehicle assembly building at Site 31 on its way to the launch pad. Click to enlarge. Credit: Roskosmos

Launch vehicle with Soyuz MS-27 shortly after installation on the launch pad at Site 31 in Baikonur. Click to enlarge. Credit: Roskosmos