SOYUZ

Soyuz (Russian: Сою́з, IPA: [sɐˈjus]), Union) is a series of spacecraft initially designed for the Soviet space programme by the Korolyov Design Bureau in the 1960s, and still in service today. The Soyuz succeeded the Voskhod spacecraft and was originally built as part of the Soviet Manned Lunar programme.

The Soyuz spacecraft is launched by the Soyuz rocket, the most frequently used and most reliable Russian launch vehicle to date. The Soyuz rocket design is based on the Vostok launcher, which in turn was based on the 8K74 or R-7A Semyorka, a Soviet intercontinental ballistic missile. Soyuz spacecraft are launched from the Baikonur Cosmodrome in Kazakhstan.

The first unmanned Soyuz mission was launched November 28, 1966; the first Soyuz mission with a crew (Soyuz 1) was launched April 23, 1967, but the cosmonaut on board,Vladimir Komarov, died during the flight's crash-landing. Soyuz 2 was an unmanned mission, and Soyuz 3, launched on October 26, 1968, was the first successful Soyuz manned mission. The only other fatal mission, Soyuz 11, killed the crew of three also during re-entry due to premature cabin depressurization. Despite these early fatalities, Soyuz is presently widely considered the world's safest, most cost-effective human spaceflight system, as demonstrated by its unparalleled length of operational history.

Soyuz spacecraft were used to carry cosmonauts to and from Salyut and later Mir Soviet space stations, and are now used for transport to and from the International Space Station(ISS). At least one Soyuz spacecraft is docked to ISS at all times for use as an escape craft in the event of an emergency.

The Soyuz spacecraft is intended to be replaced by the six-person Prospective Piloted Transport System.

DESIGN

A Soyuz spacecraft consists of three parts (from front to back):

• A spheroid orbital module, which provides accommodation for the crew during their mission;
• A small aerodynamic reentry module, which returns the crew to Earth;
• A cylindrical service module with solar panels attached, which contains the instruments and engines

Orbital Module

The forepart of the spacecraft is the orbital module (Russian: бытовой отсек (БО); Bytovoi otsek (BO)), also known as Habitation section. It houses all the equipment that will not be needed for reentry, such as experiments, cameras or cargo. The module also contains a toilet, docking avionics and communications gear. Internal volume is 6 m³, living space 5 m³. On the latest Soyuz versions (since Soyuz TM), a small window was introduced, providing the crew with a forward view.

Reentry Module

The reentry module (Russian: спускаемый аппарат (СА); Spuskaemyi apparat (SA)) is used for launch and the journey back to Earth. Half of the reentry module is covered by a heat-resistant covering to protect it during re-entry; this half faces the Earth during re-entry. It is slowed initially by the atmosphere, then by a braking parachute, followed by the main parachute which slows the craft for landing. At one meter above the ground, solid-fuel braking engines mounted behind the heat shield are fired to give a soft landing. One of the design requirements for the reentry module was for it to have the highest possible volumetric efficiency (internal volume divided by hull area).

Service Module

At the back of the vehicle is the service module (Russian: приборно-агрегатный отсек (ПАО); Priborno-Agregatnyi Otsek (PAO)). It has a pressurized container shaped like a bulging can (Instrumentation compartment, PO (Priborniy Otsek)) that contains systems for temperature control, electric power supply, long-range radio communications, radio telemetry, and instruments for orientation and control. A non-pressurized part of the service module (Propulsion compartment, AO (Agregatniy Otsek)) contains the main engine and a liquid-fuelled propulsion system for maneuvering in orbit and initiating the descent back to Earth. The ship also has a system of low-thrust engines for orientation, attached to the Intermediate compartment (PkhO or Perekhodnoi Otsek).

Re-entry procedure

The Soyuz uses a method similar to the Apollo Command/Service modules to de-orbit itself. The spacecraft is turned engine-forward and the main engine is fired for de-orbiting fully 180° ahead of its planned landing site. This requires the least propellant for re-entry, the spacecraft traveling on an elliptical Hohmann orbit to a point where it will be low enough in the atmosphere to re-enter.

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