Soyuz > Overview
The introduction of Soyuz missions from Europe's Spaceport in French Guiana brings the industry's longest-operating launcher to the world's most modern launch base.
Arianespace flights with the medium-lift Soyuz began from the Spaceport in 2011, joining the ongoing operations of Arianespace's heavy-lift Ariane 5, which will be complemented by the new lightweight Vega vehicle – which will enter service at French Guiana in 2012.
Soyuz launchers flown from the Spaceport are evolved versions that include an updated digital flight control system, an increased-performance third stage and the larger Soyuz ST payload fairing.
The startup of Arianespace’s Soyuz missions from French Guiana opened a new chapter in the history of this robust vehicle, which introduced the space age with the launch of Sputnik – the world's first satellite – in 1957. Since then, Soyuz has been in continuous production, demonstrating its unmatched reliability with more than 1,700 manned and unmanned missions performed to date.
Soyuz is a four-stage launch vehicle, and is designed to extremely high reliability levels for its use in manned missions – which today support operations of the International Space Station.
Similar first and second stages
The Soyuz’ first stage is composed of four boosters that are assembled around the launcher’s central core. These boosters are tapered cylinders, with the oxidizer tank carried in the tapered portion and the kerosene tank installed in the cylindrical section. The boosters’ RD-107A engines are powered by liquid oxygen and kerosene – the same propellants used on each of the Soyuz’ three main stages. Each engine has four combustion chambers and nozzles. Three-axis flight control is carried out by aerofins (one per booster) and movable vernier thrusters (two per booster).
Following liftoff, the first-stage’s boosters burn for 118 seconds and are then jettisoned. The separation time is determined by comparing the velocity with a predefined value. Thrust is transferred through a ball joint located at the top of the boosters’ cone-shaped structure, which is attached to the central core by two rear struts.
The Soyuz vehicle’s central core second-stage is similar in construction to the four first-stage boosters, but with a hammer-head shape to accommodate the boosters’ integration around it. A stiffening ring is located at the interface between the boosters and the core stage.
Propulsion for the second stage is provided by a RD-108A engine with four combustion chambers and nozzles, along with four vernier thrusters. This core stage nominally burns for 290 seconds, and its verniers are used for three-axis flight control once the Soyuz’ first stage boosters have separated.
Both the second stage central core and first stage boosters are ignited 20 seconds before liftoff, and they initially operate at an intermediate level of thrust in order to monitor engine health parameters. The engines are then throttled up to liftoff thrust, and the vehicle leaves the pad.
Third stage upgrades for Soyuz at the Spaceport
The Soyuz’ centerline third stage is linked to the Soyuz launcher’s central core by a latticework structure. Ignition of the third stage's main engine occurs approximately two seconds before shutdown of the launcher’s central core. The third stage engine's thrust directly separates the stage from the central core, and its engine nominally burns for 240 seconds. After engine cut-off and separation from the Soyuz’ fourth stage, the third stage performs an avoidance maneuver by opening an outgassing valve in its liquid oxygen tank.
For the upgraded Soyuz version to be operated by Arianespace from the Spaceport in French Guiana, the third stage utilizes an RD-0124 engine. It replaces the third stage’s standard RD-0110 engine – adding an additional 34 seconds of specific impulse (Isp) to significantly increase the vehicle’s overall launch performance.
The RD-0124 is a staged-combustion engine powered by a multi-stage turbopump, which is spun by gas from combustion of the main propellants in a gas generator. These oxygen-rich combustion gases are recovered to feed the four main combustion chambers where kerosene – coming from the regenerative cooling circuit – is injected. Attitude control is provided by main engine activation along one axis in two planes. Liquid oxygen (LOX) and kerosene tanks are pressurized by the heating and evaporation of helium coming from storage vessels located in the LOX tank.
Avionics for the Soyuz launcher are carried in the vehicle’s third stage, and are located in an intermediate bay between the oxidizer and fuel tanks. As part of the Soyuz’ upgrades for its operations from the Spaceport, the launcher’s flight control system is modernized with a digital control system. This system incorporates a digital computer and inertial measurement unit that are based on proven technology – giving the Soyuz improved navigation accuracy and control capability.
The new digital control system provides a more flexible and efficient attitude control system, and it gives the additional flight control authority required when the new, enlarged Soyuz ST payload fairing is installed on the vehicle. In addition, it improves flight accuracy for the Soyuz' first three stages, and provides the ability to perform in-flight roll maneuvers as well as in-plane yaw steering (dog-leg) maneuvers.
Restart capability with the Fregat upper stage
Soyuz’ Fregat upper stage is an autonomous and flexible upper stage designed to operate as an orbital vehicle. Flight qualified in 2000, it extends the Soyuz launcher’s capability to provide access to a full range of orbits (medium-Earth orbit, Sun-synchronous orbit, geostationary transfer orbit, and Earth escape trajectories).
Fregat consists of 6 spherical tanks arrayed in a circle (four for propellant, two containing the avionics), with trusses passing through the tanks to provide structural support. The stage is independent from the Soyuz’ lower three stages, having its own guidance, navigation, control, tracking, and telemetry systems.
The Fregat uses storable propellants (UDMH/NTO) and can be restarted up to 20 times in flight – enabling it to carry out complex mission profiles. It can provide 3-axis stabilization or perform a spin-up of the spacecraft payload.
Payload fairing for a full range of spacecraft passengers
An enlarged payload fairing is one of the most visible changes for improved Soyuz launchers to be operated from the Spaceport. It is based on the proven configuration used for Arianespace’s Ariane 4 vehicles, with its length increased by approximately one additional meter.
The new Soyuz fairing has a diameter of 4.11 meters and an overall length of 11.4 meters – enabling it to accommodate the full range of payloads in the launch vehicle’s performance category.
Constellation dispensers and auxiliary platforms for “piggyback” passengers
For the European Galileo navigation satellites, a dispenser system was developed for Arianespace that carries two of the spacecraft side-by-side under the Soyuz payload fairing. This dispenser deploys the spacecraft by firing a pyrotechnic separation system to simultaneously release them in opposite directions. Its first use was on Soyuz’ October 21, 2011 maiden flight from the Spaceport.
Arianespace plans to further enhance the Soyuz’ mission flexibility with the development of a structure to accommodate small secondary payloads. Called the ASAP-S, this system continues the auxiliary platform concept previously developed for Ariane missions, which have enabled “piggyback” passengers to be flown for the past 20-plus years.
The ASAP-S has external positions for four micro-satellites, along with volume inside the center structure for a fifth payload. The ASAP-S' external configuration accommodates spacecraft weighing up to 200 kg., while the internal position is designed to accept a payload with a maximum mass of 400 kg. Arianespace’s initial use of the ASAP-S is planned for Soyuz’ second flight from the Spaceport, scheduled for December 2011, which will carry French CNES space agency’s Pleiades optical Earth observation satellite, along with five supplemental payloads: four French Elisa micro-satellites for a demonstration of defense-related orbital electronic intelligence gathering (ELINT); and the Chilean SSOT (Sistema satelital de Observación de la Tierra) optical satellite for civilian and defense Earth observation.