File image of Soyuz-Fregat rocket launching from Baikonur. Credit: ESA-Astrium

The Soyuz launch vehicle family has provided reliable and efficient launch services since the birth of the space program. Vehicles in this family, which launched both the first satellite and first man into space, have been credited with more than 1670 launches to this date. Today, this vehicle is used for manned and unmanned flights to the International Space Station and commercial launches managed by Starsem.

The Soyuz configuration introduced in 1966 has been the workhorse of the Soviet/Russian space program, achieving a high launch success rate in over 800 flights. As the only manned launch vehicle in Russia and the former Soviet Union, the Soyuz benefits from exacting standards in both reliability and robustness.

The addition of the restartable Ikar upper stage to the three-stage Soyuz in 1999 allowed Starsem to launch 24 satellites of the Globalstar constellation in 6 launches.

Following this success, Starsem introduced the flexible, restartable Fregat upper stage with significantly more propellant capacity than the Ikar, thus opening up a full range of missions (LEO, SSO, MEO, GTO, GEO, and escape).

The venerable Russian Soyuz rocket has been launching for decades. Credit: ESA-Astrium

In 2005, Starsem will introduce an upgraded version of the Soyuz launch vehicle, which adds increased payload volume (4.110-m fairing) and flexibility (digital control system) to this launch system and meets both the performance and payload accommodation needs of the customer.

The Samara Space Center continues to mass-produce the Soyuz in Samara, Russia. As a result of continued demand from the Russian government, International Space Station activity, and Starsem's commercial orders, the Soyuz is in uninterrupted production at an average rate of 10 to 15 launch vehicles per year with a capability to rapidly scale up to accommodate user's needs. In fact, peak production of the Soyuz in the early 1980's reached 60 vehicles per year.

The Soyuz is a reliable, efficient, and costeffective solution for a full range of missions from LEO to Mars. In its unequalled flight history, the Soyuz has already performed almost every mission profile, including orbiting satellites for telecommunications, Earth observation, weather monitoring, scientific missions and manned flights. It is a highly responsive and flexible launch vehicle.

The Soyuz currently offered by Starsem is a four-stage launch vehicle. The vehicles each consist of four boosters (first stage), a central core (second stage), a third stage, and the restartable Fregat upper stage (fourth stage). Each vehicle also includes a payload adapter/dispenser and fairing.

An illustration of Soyuz rocket with Mars Express. Credit: Astrium

Boosters (first stage)

The four boosters are assembled around the central core and are tapered cylinders with the oxidizer tank in the tapered portion and the kerosene tank in the cylindrical portion.

The booster's RD-107A engines are powered by liquid oxygen and kerosene, the same propellants which are used on each of the lower three 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 boosters burn for 118 seconds and are then discarded. 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 cone-shaped structure of the booster, which is attached to the central core by two rear struts.

Central Core (second stage)

The central core is similar in construction to the four boosters, with a hammer-head shape to accommodate the boosters. A stiffening ring is located at the interface between the boosters and the core.

This stage has a RD-108A engine with four combustion chambers and nozzles and four vernier thrusters. The verniers are used for three-axis flight control once the boosters have separated. The core stage nominally burns for 290 seconds.

Ignition of the central core and boosters occurs at an intermediate level of thrust on the launch pad 20 seconds before liftoff in order to monitor engine health parameters before the engines are throttled up and the vehicle leaves the pad.

Third Stage

The third stage is linked to the central core by a latticework structure. Ignition of the third stage's main engine occurs approximately 2 seconds before shutdown of the central core. The third stage engine's thrust directly separates the stage from the central core. In between the oxidizer and fuel tanks is an intermediate bay where avionics systems are located.

This stage uses a RD-0110 engine with four combustion chambers and nozzles. Four vernier nozzles provide three-axis flight control.

The third stage engine nominally burns for 240 seconds. After engine cut-off and separation of the fourth stage, the third stage performs an avoidance maneuver by opening an outgassing valve in the liquid oxygen tank.

Fregat Upper Stage (fourth stage)

Flight qualified in 2000, the Fregat upper stage is an autonomous and flexible upper stage that is designed to operate as an orbital vehicle. It extends the capability of the lower three stages of the Soyuz vehicle to provide access to a full range of orbits (MEO, SSO, GTO, escape).

In order to provide the Fregat with high initial reliability, several flight-proven subsystems and components from previous spacecraft and rockets are incorporated into the upper stage.

The upper stage consists of 6 spherical tanks (4 for propellant, 2 for avionics) arrayed in a circle, with trusses passing through the tanks to provide structural support. The stage is independent from the lower three stages, having its own guidance, navigation, control, tracking, and telemetry systems.

The stage uses storable propellants (UDMH/NTO) and can be restarted up to 20 times in flight, thus enabling it to carry out complex mission profiles. It can provide the customer with 3-axis stabilization or spin-up of their spacecraft.

Payload Accommodation

The current Soyuz flies the S-type fairing, with external diameter of 3.715-m and a length of 7.700-m. The Fregat upper stage is encapsulated in the fairing with the payload and a payload adapter / dispenser.

Starsem has already developed a series of adapters and dispensers, which may be used directly by the customer. Starsem can also carry out development of a new adapter or dispenser tailored to the customer's spacecraft.