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Docking systems


Kurs-NA rendezvous system


Soyuz MS power supply system


EKTS communications system


Propulsion system


"Black Box"


Despite being known for its cramped quarters, the Soyuz provides all critical functions of a manned space transport with minimal size, weight and cost, which made it the longest serving vehicle desinged to carry humans into space during its time. This section provides the summary of critical systems onboard a typical Soyuz vehicle.

Thermal Control System

Sistema Obespecheniya Teplovogo Rezhima, SOTR

The system is designed to maintain normal temperature (18 - 25 degrees C) and humidity ( 20 - 80 percent) inside habitable sections of the spacecraft and the nominal temperature (0 - 40 degrees C) for the vehicle's systems and structures. The system includes both active and passive elements, among them thermal insulation known by its Russian acronym EVI, for Ekranno-Vacuumnaya Izolyatsiya, EVI, a ventilation system, and internal and external liquid cooling loops.

A classic seven-ton Soyuz vehicle consists of three major components, providing for every stage of flight from orbital insertion to landing. To protect the ship's systems from extreme temperature swings in space, all its surfaces exposed to space, except for active elements of sensors, antennas, windows, the docking hardware, thruster nozzles and radiator panels, are blanketed by multilayer vacuum-screen thermal insulation.

Life Support System

Kompleks Sredstv Obespecheniya Zhiznideyatelnosti, KSOZh

This group of systems generates and maintains livable conditions onboard the spacecraft. It includes water supplies, food, toilet and emergency life support systems.

Pressure suits

After the loss of the Soyuz-11 crew in 1971, a Sokol (Falcon) safety pressure suits were introduced to protect the crewmembers in the event of the hull breach. The crew is supposed to wear the suits during the launch, docking, undocking and descent. The suit is formally considered a part of the Life Support System.

Power Supply System

Sistema Elektropitaniya, SEP

To provide 27 Volts of electricity throughout the spacecraft, the Soyuz is equipped with two solar panels, prime and backup batteries, a battery for the descent module, a battery for the habitation module and automation and monitoring hardware. The SEP system was upgraded on the Soyuz MS variant.

Communication and Tracking Systems

Communication and Tracking systems of the Soyuz are subdivided into five major elements:

The Rassvet (Dawn) radio communications system provides audio communication between the crew and the ground. Two-way voice communication between the crew and ground station is achieved via Very High Frequency, VHF radio. The cosmonauts can also talk to each other from all habitable compartments and with the crew onboard the station, as well as record and playback voice.

The Onboard Measurement System, SBI, conducts acquisition, processing, storing and downlinking telemetry data, which monitors health of the onboard systems and the crew. The network is fully automated and does not require any input from the crew.

The Kvant-V system provides two-way radio link and spacecraft control, during the active stage of orbital flight.

The Klyost-M television system, allows to downlink video from the reentry capsule, provides TV images of rendezvous and docking, as well as it allow data display and downlinking television data via the Kvant-V transmitters.

The Orbit Radio Tracking (RKO) provides trajectory determination for the Soyuz and Progress, when they are in the autonomous flight. The RKO receives an interrogation signal and then transmits a reply signal back to the ground station. The system is controlled by the Kvant-V radio system and works in concert with ground computers to determine vehicle velocity and position. Replaced with the EKTS system on the Soyuz MS variant.

Onboard Complex Control System

Sistema Upravleniya Bortovym Kompleksom, SUBK

This system encompasses a number of logic switches; Program Timing Device, APVU; the cosmonaut control panel; spacecraft module separation system and onboard cable network. The systems handles commands, which come from the cosmonaut panel, from ground control stations, from APV or even another spacecraft, using remote control.

Systems for propulsion and motion control

The Integrated Propulsion System (KDU) includes pressure-fed orbit correction engines and attitude control thrusters, DPO, all burning two-component propellant: nitrogen tetroxide as an oxidizer and unsymmetrical dimethylhydrazine as a fuel. Primary components include a pressurization system, a propellant supply system, an orbital maneuvering propulsion unit, approach and attitude control thrusters, DPU. The Progress cargo ship uses similar but not identical propulsion system.

The operational lifespan of the system is 180 days and it is certified for storage with propellant for one year. The KDU system upgraded on the Soyuz MS variant.

Beginning with the mission of Soyuz-4, the serial production of propulsion systems for the Soyuz spacecraft is conducted at the Ust-Katav Wagon-building Plant, which was initiated in 1964.

The Chaika-3 Motion Control System (SUD) is based on the use of inertial control system and an onboard digital computer complex. The system includes two control loops: a digital automatic control loop, serving as the primary system; and a backup analog control loop. The analog control loop is used for attitude control before descent, as well as for manual rendezvous and docking if the primary digital automatic control fails.

Optical/Visual Devices (OVP) is used by the crew for motion control functions. These include:

  • VSK-4 (Vizir Spetsialniy Kosmicheskiy-4);
  • Night Vision Device (VNUK-K, Visir Nochnogo Upravleniya po Kursu);
  • Docking light;
  • Pilot's Sight (VP-1, Vizir Pilota-1);
  • Laser Range Finder (LPR-1, Lazerniy Dalnomer-1);

Kurs rendezvous system

The Kurs ("course") system uses an active response radar for measurement of relative motion between two spacecraft, during automatic rendezvous, fly-around and berthing. The Soyuz and Progress vehicles are equipped with the "active" part of the Kurs system, when the space stations carry "passive" systems.

The Kurs-A system was upgraded to the Kurs-NA variant on the Soyuz MS variant.

Docking System

Sistema Stukovki i Vnutrennego Perekhoda, SSVP

The docking was the primary capability of the Soyuz spacecraft during both lunar landing program and numerous space station missions that followed. Several types and reincarnations of the docking hardware were tested between 1967 and 1975, before a long-lived design of the "drog-and-cone system" has emerged. Such mechanism involves a rod on the Soyuz spacecraft, which serves as an active spacecraft during the rendezvous, and a receptive cone, installed onboard the space station.

Teleoperator Control Mode

Teleoperatorniy Rezhim Upravleniya, TORU

During the mission of the Mir space station, cosmonauts first tested a flight control system, where a pilot onboard the station could remotely control the incoming transport ship to a rendezvous and docking, as if he/she was onboard that ship. The system was designed to give the operator onboard the station, the ability to dock the unmanned Progress cargo ship, in case the primary Automated Rendezvous and Docking System fails. The TORU control panel was installed near the main command post of the service module of the International Space Station, ISS.

Entry Actuators System

Sistema Ispolnitelnikh Organov Spuska, SIO-S

The SIO-S system is responsible for keeping the spacecraft properly oriented during the most critical phase of the flight -- the reentry into the Earth atmosphere.

Landing Aids Kit

Kompleks Sredstv Prizemleniya, KSP

This kit includes all the gear necessary for safe landing on land, in water, or in the aftermath of the launch failure. Primary components of the KSP system, include main and reserve parachute systems, soft-landing engines, the Kazbek shock-absorbing seats.

Portable Survival Kit

Nosimiy Avariyniy Zapas, NAZ

This kit includes all the survival gear, should the landing take place in unintended, hard-to-access area, requiring the crew to await rescue for a long time.

Soyuz Launch Escape System

Sistema Avariynogo Spaseniya, SAS

The SAS system is designed to carry the habitable compartments of the Soyuz spacecraft away from the rocket, in case of the emergency situation during a ride to orbit or on the launch pad.

Details here

This page is maintained by Anatoly Zak

Last update: July 8, 2016


A virtual reality model, illustrating exterior design of the Soyuz TM spacecraft. (Click and drag with your mouse to rotate the model in the window.) (QuickTime VR: 340 K)

The Soyuz spacecraft. Copyright © 2005 Anatoly Zak

The Soyuz TM spacecraft photographed by the Shuttle crew at the docking port of the Mir space station. Credit: NASA

Flight control panel inside original version of the Soyuz spacecraft. Click to enlarge Copyright © 2000 Anatoly Zak

The main control panel inside of the Soyuz TM simulator. Copyright © 2000 Anatoly Zak

A simulator of the Soyuz TM spacecraft used for cosmonaut training. Copyright © 2000 Anatoly Zak


Unflown APAS docking port next to the actual reentry capsule of the Soyuz-19 after its return from a joint mission with the US Apollo. Copyright © 2011 Anatoly Zak

Docking mechanism of the Soyuz spacecraft. Copyright © 2000 Anatoly Zak