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.

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 and to speed up the development process, 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.

Vehicle Telemetry, Tracking, and Range Safety

For the lower three stages of the Soyuz, launch vehicle tracking and telemetry is provided through systems in the central core and third stages. These two stages have their own radar transponders for ground tracking. Individual telemetry transmitters are in each stage. For the Fregat, two different systems provide tracking and telemetry information from launch, independent from the systems on the lower three stages.

Telemetry and tracking data is downlinked to ground stations along the flight path. This data is then transmitted to the mission control center, where it is recorded. Near real-time data processing and plotting is conducted to follow the flight and to determine an initial performance assessment. Flight data is analyzed and documented within a few hours after launch.

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.


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