Soyuz (Russian: Союз, IPA: [sɐˈjus], lit. 'Union') is a series of spacecraft which has been in service since the 1960s, having made more than 140 flights. It was designed for the Soviet space program by the Korolev Design Bureau (now Energia). The Soyuz succeeded the Voskhod spacecraft and was originally built as part of the Soviet crewed lunar programs. It is launched atop the similarly named Soyuz rocket from the Baikonur Cosmodrome in Kazakhstan. Following the Soviet Union's dissolution, Roscosmos, the Russian space agency, continued to develop and utilize the Soyuz. Between the Space Shuttle's 2011 retirement and the SpaceX Crew Dragon's 2020 debut, Soyuz was the sole means of crewed transportation to and from the International Space Station, a role it continues to fulfill. The Soyuz design has also influenced other spacecraft, including China's Shenzhou and Russia's Progress cargo vehicle. The Soyuz is a single-use spacecraft composed of three main sections. The descent module is where cosmonauts are seated for launch and reentry. The orbital module provides additional living space and storage during orbit but is jettisoned before reentry. The service module, responsible for propulsion and power, is also discarded prior to reentry. For added safety and aerodynamics, the spacecraft is encased within a fairing with a launch escape system during liftoff.
History The first Soyuz mission, Kosmos 133, launched unmanned on 28 November 1966. The first crewed Soyuz mission, Soyuz 1, launched on 23 April 1967 but ended tragically on 24 April 1967 when the parachute failed to deploy on reentry, killing cosmonaut Vladimir Komarov. The following flight, Soyuz 2 was uncrewed. Soyuz 3 launched on 26 October 1968 and became the program's first successful crewed mission. The program suffered another fatal setback during Soyuz 11, where cabin depressurization during reentry killed the entire crew. These are the only humans to date who are known to have died above the Kármán line, the conventional definition of the edge of space. Despite these early tragedies, Soyuz has earned a reputation as one of the safest and most cost-effective human spaceflight vehicles, a legacy built upon its unparalleled operational history. The spacecraft has served as the primary mode of transport for cosmonauts to and from the Salyut space stations, the Mir space station, and International Space Station (ISS).
Design
Soyuz spacecraft are composed of three primary sections (from top to bottom, when standing on the launch pad):
Orbital module: A spheroid compartment providing living space for the crew. Descent module: A small, aerodynamic capsule where the crew is seated for launch and return the crew to Earth. Service module: A cylindrical section housing propulsion, power, and other systems. The orbital and service modules are discarded and destroyed upon reentry. This design choice, while seemingly wasteful, reduces the spacecraft's weight by minimizing the amount of heat shielding required. As a result, Soyuz offers more habitable interior space (7.5 cubic metres, 260 cubic feet) compared to its Apollo counterpart (6.3 m3, 220 cu ft). While the reentry module does return to Earth, it is not reusable. A new Soyuz spacecraft is made for each mission. Soyuz can carry up to three crew members and provide life support for about 30 person-days. A payload fairing protects Soyuz during launch and is jettisoned early in flight. Equipped with an automated docking system, the spacecraft can operate autonomously or under manual control.
Launch escape system The Vostok spacecraft used an ejector seat to bail out the cosmonaut in the event of a low-altitude launch failure, as well as during reentry; however, it would probably have been ineffective in the first 20 seconds after liftoff, when the altitude would be too low for the parachute to deploy. Inspired by the Mercury LES, Soviet designers began work on a similar system in 1962. This included developing a complex sensing system to monitor various launch-vehicle parameters and trigger an abort if a booster malfunction occurred. Based on data from R-7 launches over the years, engineers developed a list of the most likely failure modes for the vehicle and could narrow down abort conditions to premature separation of a strap-on booster, low engine thrust, loss of combustion-chamber pressure, or loss of booster guidance. The spacecraft abort system (SAS; Russian: Система Аварийного Спасения, romanized: Sistema Avariynogo Spaseniya) could also be manually activated from the ground, but unlike American spacecraft, there was no way for the cosmonauts to trigger it themselves. Since it turned out to be almost impossible to separate the entire payload shroud from the Soyuz service module cleanly, the decision was made to have the shroud split between the service module and descent module during an abort. Four folding stabilizers were added to improve aerodynamic stability during ascent. Two test runs of the SAS were carried out in 1966–1967.
The basic design of the SAS has remained almost unchanged in 50 years of use, and all Soyuz launches carry it. The only modification was in 1972, when the aerodynamic fairing over the SAS motor nozzles was removed for weight-saving reasons, as the redesigned Soyuz 7K-T spacecraft carried extra life-support equipment. The uncrewed Progress resupply ferry has a dummy escape tower and removes the stabilizer fins from the payload shroud. There have been three failed launches of a crewed Soyuz vehicle: Soyuz 18a in 1975, Soyuz T-10a in 1983 and Soyuz MS-10 in October 2018. The 1975 failure was aborted after escape-tower jettison. In 1983, Soyuz T-10a's SAS successfully rescued the cosmonauts from an on-pad fire and explosion of the launch vehicle. Most recently, in 2018, the SAS sub-system in the payload shroud of Soyuz MS-10 successfully rescued the cosmonauts from a rocket failure 2 minutes and 45 seconds after liftoff, after the escape tower had already been jettisoned.
Orbital module
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