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Descent Module, SA, of the Soyuz spacecraft

The reentry capsule of the Soyuz spacecraft is known by its Russian acronym "SA" for spuskaemy apparat or descent apparatus, which is officially identified as Descent Module. It is the only section of the vehicle, which returns to Earth at the end of the mission.

Previous chapter: Habitation module of the Soyuz spacecraft


Crew inside the descent module of the Soyuz MS-05 spacecraft.

The ball-shaped Descent Module of the Soyuz spacecraft is manufactured from the aluminum alloy and covered with ablative thermal protection on the exterior. The front bulkhead of the capsule and the main heat shield are made of a titanium alloy.

The Descent Module contains two or three personally contoured couches where the cosmonauts recline for ascent, descent and landing. Seats are facing controls and displays developed at OAO Fazotron-NIIR that are used for all critical flight activities.

The reentry capsule also contains life-support systems, batteries for the descent phase of the mission, primary and backup parachutes and solid-propellant engines for landing. The module is equipped with eight small attitude control thrusters, which are used exclusively during the descent phase of the flight. They rely on hydrogen peroxide as a one-component propellant which doesn't need oxidizer. However, the tendency of peroxide to degrade over time is considered as a limiting factor for the duration of the Soyuz missions normally planned for no more than six months.

The reentry capsule is also equipped with an independent guidance, navigation and control system that is less complex than the main flight control system in the PAO module.

A periscope extending from the Descent Module provides the pilot with a forward view toward the docking mechanism and a downward view for tracking the surface of the Earth.


Catherine Coleman, a member of Soyuz TMA-20 crew, inside the descent module, looking toward the right side of the capsule. The main flight control panel, sporting liquid-crystal displays is on the left. Credit: Roskosmos


Above: Members of Soyuz TMA-20 crew, Dmitry Kondratyev (left) and Paolo Nespoli inside the descent module, looking toward the left side of the capsule. Credit: Roskosmos

Ventilation of the Descent Module, SA (INSIDER CONTENT)

One critical sub-system providing thermal control inside the three pressurized compartments of the Soyuz crew vehicle is ventilation hardware. It is designed to operate not only in space, but also during pre-launch processing of the spacecraft, on the launch pad and after the completion of the flight on land or at sea.


Known technical specifications of the reentry capsule of the Soyuz spacecraft:

2,900 kilograms
Length 2.1 meters
Diameter 2.2 meters
Transfer hatch diameter 700 millimeters
Habitable volume 4 cubic meters
Retrievable payload with a crew of three

50 kilograms

Retrievable payload with a crew of two 150 kilograms



Next chapter: Instrument module of the Soyuz spacecraft

Page author: Anatoly Zak

Last update: January 5, 2024

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insider content

The reentry capsule of the Soyuz-3 spacecraft. The cover of the parachute container is in the foreground. The opening of the parachute container can be seen on the left side of the capsule. Copyright © 2001 Anatoly Zak

The reentry capsule of the Soyuz spacecraft. The entry hatch is in front. Two hatches of the parachute containers are on top. Copyright © 2001 Anatoly Zak

Bottom of the Soyuz reentry capsule, without its heat shield. Copyright © 2001 Anatoly Zak

A dissected Soyuz reentry vehicle (left) and habitable section (partially visible). Copyright © 2000 Anatoly Zak

A parachute container of the Soyuz spacecraft. Copyright © 2001 Anatoly Zak