Soyuz U – Launch Vehicle

Photo: NASA

Soyuz-U is the most flown of the historic Soyuz launcher family with more than 770 flights and a success rate of 97%.

The vehicle is a member of the Soyuz Rocket Family that has a history dating back to 1957. Soyuz launchers have been derived from the R-7 missile that was developed during the Cold War making 28 launches between 1957 and 1961. There have been various different versions of the Soyuz Launcher; currently a number of different configurations is available to serve a variety of purposes.

The Soyuz U Launcher Family is currently operating alongside the Soyuz-2 and FG Launcher. Soyuz-U is operated from the Baikonur Cosmodrome, Kazakhstan and Plesetsk Cosmodrome, Russia. Soyuz-U will be phased out starting in 2014 as the more advanced Soyuz-2 that uses modern flight control and guidance systems and improved manufacturing processes will take over from the venerable Soyuz-U that made its first flight in 1973.

Soyuz-U uses a large number of heritage components, some of which are hard to manufacture nowadays and come from contractors that were acquired back in Soviet times. The launch system is one of the most flown and most-robust systems in the world and many of its components will live on in the new Soyuz-2 series of vehicles.

Soyuz-U has launched a variety of payloads into a number of different orbits and trajectories over its career. It was also used to launch manned Soyuz spacecraft to the Salyut, Mir and ISS Space Stations starting in the 1970s as part of the Apollo-Soyuz Test Project. Soyuz-U itself is used to deliver Payloads to Low Earth and Sun-Synchronous Orbits, but the addition of an optional upper stage enables the launch vehicle to reach a variety of Orbits including Geosynchronous Transfer Orbit.

Photo: RSC Energia
Photo: RSC Energia

Briefly, Soyuz-U flew under the designation Soyuz-U2 which used the basic Soyuz-U hardware, but featured high-energy Synthin fuel on the first stage to increase launch vehicle performance. Soyuz-U2 made less than 90 launches in the 1980s and 90s. Launches reverted back to Soyuz-U when Synthin production ended in 1996.

Currently, Soyuz-U is used to transport unmanned Progress Resupply Spacecraft to Orbit for International Space Station Resupply Missions. Also, the vehicle is occasionally used to launch military reconnaissance payloads. Russian officials plan to fly the final existing Soyuz-U launch vehicles by 2014 or 2015 to have Soyuz-2 take over at that point.

Soyuz-U is manufactured by TsSKB-Progress of Samara, Russia.

Photo: RSC Energia
Photo: RSC Energia

Type Soyuz U
Manufacturer TSSKB-Progress
Index 11A511U
Height 46m
Diameter 2.95m
Launch Mass 313,000kg
Mass to LEO 6,900kg
Mass to GTO 2,900kg (Fregat)

Soyuz U Specifications

The Soyuz-U Launch Vehicle stands 46 meters tall (when flying with Progress) and has a main diameter of 2.95 meters and a pan from booster fin to booster fin of 10.3 meters.

All stages of the vehicle use Rocket Propellant 1 (Rocket-Grade Kerosene) and Liquid Oxygen as propellants. Liftoff mass is about 313,000 Kilograms. The U version of the Soyuz can deliver payloads of up to 6,900 Kilograms to Low Earth Orbit, making it suitable for cargo resupply flights to Space Stations as well as crewed Soyuz spacecraft launches. Topped with a Fregat Upper Stage, Soyuz U can loft nearly three metric tons into a Geostationary Transfer Orbit.


Photo: RSC Energia
Photo: RSC Energia
Boosters 4
Diameter 2.68m
Length 19.6m
Empty Mass 3,810kg
Fuel Rocket Propellant 1
Oxidizer Liquid Oxygen
Fueled Mass 43,410kg
Fuel Mass 11,250kg
Oxidizer Mass 27,900kg
Guidance From 3rd Stage
Tank Pressurization Nitrogen
Propulsion 1 RD-117
Propellant Feed Turbopump
Comb. Chambers 4
Total Thrust SL 838.5kN
Total Thrust Vac 1,021.3kN
Engine Length 1.58m
Engine Diameter 2.50m
Engine Dry Weight 1,250kg
Burn Time 119s
Specific Impulse 264s (SL) 310s (Vac)
Chamber Pressure 60bar
Throttle Capability Yes
Engine Start Spark
Restart Capability No
Ox to Fuel Ratio 2.47
Attitude Control 2 Vernier Thrusters
Shutdown Commanded Shutdown

Soyuz U is outfitted with four liquid fueled strap-on boosters providing extra lift during the initial phase of the flight.

All four boosters are ignited before liftoff to reach full thrust and are jettisoned once their fuel tanks are empty. The boosters are arranged around the central Core Stage and are tapered cylinders. The Oxidizer Tank is in the tapered portion of the booster while the fuel tank is inside the cylindrical portion. Each booster holds a total of 39,600 Kilograms of Propellants which are Liquid Oxygen and Rocket Propellant 1.

The LOX tank has a volume of 24,921 liters while the Kerosene tank can hold 14,017 liters. A Soyuz Booster is 19.6 meters in length and 2.68 meters in diameter.

An RD-117 Engine is installed on each booster providing a thrust of 838.5 Kilonewtons at Liftoff. RD-117 is an improved version with more efficient fuel injection, but it is very similar to the RD-107 and RD-107A engines of other Soyuz Launchers. The engine utilizes a spark ignition system and can not be re-started. RD-117 features four combustion chambers that are fed by a Turbopump transferring 91 Kilograms of Kerosene and 226 Kilograms of Oxygen every second.

Credit: NPO Energomash
Credit: NPO Energomash

Several auxiliary pumps are used to keep the Propellant Tanks at flight pressure by feeding them with Nitrogen. Another pump delivers Hydrogen Peroxide to the main pump that is used to power it. A total of 1,190 kilograms of Hydrogen Peroxide and 280 Kilograms of liquid Nitrogen are stored inside spherical tanks and are expended during ascent for the aforementioned purposes. The Turbopump spins at over 8,000rpm at flight speed.

The four nozzles of the RD-117 can not be gimbaled, but the engine is outfitted with two vernier jets that can be used for attitude control. Also, an aerofin is installed on the base of the booster and also contributes to attitude stability. The engine has a dry weight of 1,250 Kilograms and is 2.50 meters in length and 1.58 meters in diameter. All boosters ignite about 20 seconds before launch to allow the Turbopumps to spin up to flight speed. Also, the engines are being monitored during that period to make sure performance is nominal. The Boosters Burn for 118 seconds following liftoff before being separated from the launch vehicle and impacting downrange.

Photo: RSC Energia
Photo: RSC Energia


Core Stage

Type Core Stage
Inert Mass 6,550kg
Launch Mass 99,500kg
Diameter 2.95m
Length 27.8m
Fuel Rocket Propellant-1 (Kerosene)
Oxidizer Liquid Oxygen
Fuel Mass 26,300kg
Oxidizer Mass 63,800kg
Propulsion 1 RD-118 (4 Chambers)
Thrust at Sea Level 813.0kN
Thrust (Vacuum) 999.6kN
Throttling One Level Thrust Throttling
Impulse 245s (SL) – 311s (Vac)
Engine Length 2.87m
Engine Diameter 1.85m
Engine Dry Weight 1,155kg
Burn Time 286 sec
Chamber Pressure 54.4bar
Ox. To Fuel 2.39
Throttle Capability Yes
Engine Start Spark
Restart Capability No
Turbopump Prop Hydrogen Peroxide (2,600kg)
Attitude Control 4 Vernier jets
Stage Separation Pyronuts – 3rd Stage Ignition

The Core Stage of the Soyuz Vehicle acts as both, first and second stage. It is ignited prior to blastoff and continues to power the launcher after Booster Jettison as the second stage.

The Core Stage is 27.8 meters long and 2.95 meters in diameter. It is equipped with a large Oxidizer Tank and a Fuel Tank beneath it, both holding a total of 92,950 Kilograms of Propellants (32,350 liters of Kerosene, 57,441 liters of LOX).

Where the boosters interface with the core stage, a load carrying ring is installed to transfer loads from the boosters to the vehicle.

On top of the core stage is a Truss Segment that interfaces with the upper stage and includes stage separation mechanisms.

The core stage is powered by an RD-118 Engine which is similar to the Booster Main Engine (RD-117). It also features four combustion chambers and the same pump design. The main Turbopump is also powered by Hydrogen Peroxide. 2,600 Kilograms are consumed during the burn of the stage. 520 Kilograms of liquid Nitrogen are used to keep the Propellant Tanks at flight pressure during the ascent.

Credit: NPO Energomash
Credit: NPO Energomash

RD-118 provides 813 Kilonewtons of Thrust at Launch. Vacuum Thrust is 999.6Kilonewtons making the engine slightly more powerful than the RD-108A engine of the Soyuz FG. The Engine has a dry weight of 1,155 Kilograms and operates at a chamber pressure of 54.43 bar.

Four Vernier Engines can be gimbaled to provide three-axis-attitude control during the ascent phase of the mission. The first stage is ignited 20 seconds before liftoff for performance monitoring. The Stage burns for 290 seconds before separating from the third stage.

The two stages are separated by pyrotechnic bolts and by igniting the third stage to push the core stage away from the stack. During second stage flight, the protective Payload Fairing is jettisoned to increase launcher performance.

Photo: Roscosmos
Photo: Roscosmos


Block I Upper Stage

Diameter 2.66m
Length 6.74m
Empty Mass 2,410kg
Fuel Rocket Propellant 1
Oxidizer Liquid Oxygen
Fueled Mass 25,300kg
Fuel Mass 7,100kg
Oxidizer Mass 15,700kg
Tank Pressurization Oxygen Gas; Combustion Products
Propulsion 1 RD-0110
Engine Type Gas Generator
Propellant Feed Turbopump
Comb. Chambers 4
Total Thrust Vac 297.9kN
Engine Length 1.58m
Engine Diameter 2.24m
Engine Dry Weight 408kg
Nozzle Ratio 82.2
Thrust-to-Weight 74.5
Burn Time 230s
Specific Impulse 326s (Vac)
Chamber Pressure 68.2bar
Restart Capability No
Ox to Fuel Ratio 2.2
Attitude Control 4 Vernier Jets; Reaction Nozzle
Shutdown Commanded Shutdown

The third stage of the Soyuz-U is 6.74 meters in length and 2.66 meters in diameter. It also uses the conventional design with the Fuel Tank being placed on top of the Oxygen tank. The Avionics of the Soyuz Launcher are also installed on the Upper Stage. These present the main difference between Soyuz-U and other versions.

The control system features a digital onboard computer providing all vehicle commanding. The Guidance System of the Soyuz-U uses heritage components that have not been improved over several years and cause the Soyuz-U to be less flexible than modern launchers.

The outdated Guidance System does not allow Soyuz-U to perform a roll maneuver after liftoff which means that the launch table of the Soyuz has to be physically turned to set up the proper launch azimuth. Also, there are only a limited number of Payload Fairings for the Soyuz-U because the guidance system can not handle the instability caused by larger payload fairing.

The third stage tanks are capable of holding 22,845 Kilograms of Propellants. An RD-0110 Engine is installed on the upper stage. This engine is different from the other engine types used on the Soyuz Vehicle as it is a Gas Generator Type Main Engine. It also has four combustion chambers and provides a total thrust of 297.9 Kilonewtons.

Source: American Institute of Aeronautics and Astronautics
Source: American Institute of Aeronautics and Astronautics

The single Turbopump of the RD-0110 is powered by gas from combustion of the main propellants, Rocket Propellant 1 and Liquid Oxygen. The Gas Generator enables the main Turbopump to spin at up to 18,400rpm. After moving through the Turbopump, the gases from the generator are recovered and used in four attitude control thrusters. Each of the thrusters provides 6 Kilonewtons of Thrust and can be gimbaled to achieve three-axis control.

A reaction nozzle is mounted in the side of the stage and is used for collision avoidance maneuvers by venting the LOX Tank. Oxygen Tank pressurization is accomplished by evaporated and heated Oxygen while the RP-1 Tank is pressurized with combustion products from the Gas Generator. RD-0110 has dry weight of 408 Kilograms. It is 1.58 meters in length and 2.24 meters in diameter. It operates at a chamber pressure of 68.2 bar. The third stage of the Soyuz burns for 300 seconds before deploying the Orbital Unit or Payloads.

Photo: RSC Energia
Photo: RSC Energia


Fregat Upper Stage

Image: Arianespace
Image: Arianespace
Type Fregat Upper Stage
Diameter 3.35m (Fregat) to 3.38m (MT)
Length 1.55m (Fregat) to 1.85m (MT)
# Propellant Tanks 4
# Avionics Tanks 2
Fuel Unsymmetrical Dimethylhydrazine
Oxidizer Nitrogen Tetroxide
Inert Mass 930kg
Propellant Mass 5,250kg
Launch Mass 6,200kg
Inert Mass 960kg
Propellant Mass 5,750kg
Tanks Small Tank Extensions
Launch Mass 6,710kg
Inert Mass 1,050kg
Propellant Mass 7,100kg
Tanks Large Tank Extensions
Launch Mass 8,150kg
All Fregat Stages
Propulsion S5.92
Type Turbopump-fed
Thrust at Level 1 19.85kN
Thrust at Level 2 14.00kN
Impulse 331s
Dry Mass 80kg
Engine Length 1.03m
Engine Diameter 0.84m
Chamber Pressure 6.85 to 9.8 MPa
Startup Time 2.5 to 3.0sec
Burn Time Variable – Up to 900 sec
Restart Capability Up to 20 Restarts
Attitude control Main Engine Translation (Pitch, Yaw)
8 Hydrazine Thrusters (Pitch, Yaw)
4 Hydrazine Thrusters (Roll)
ACS Thrusters S5.221
ACS Thrust 50N
ACS Propellant 85kg
Separation Gas pressure Locks/Pushers
Shutdown Commanded/Depletion
Operation Lifetime Up to 48 hours
Flight Computer Biser 6
Navigation 3-axis Platform (Gyros, GPS)

To increase Launch Vehicle performance and provide precise injection capabilities, the Soyuz FG can be outfitted with a Fregat Upper Stage that is capable of performing several burns to target a variety of different orbital trajectories.

Fregat is an autonomous Upper Stage that is equipped with its own power, propulsion and control system to perform flights of up to 48 hours. The upper stage consists of six spherical tanks (four for propellant, two for avionics) arrayed in a circle, with trusses passing through the tanks providing structural support. NPO Lavochkin of Moscow is responsible for the production of Fregat.

The conventional Fregat upper stage measures 3.35 meters in diameter and is 1.55 meters in length with six propellant tanks. Four tanks hold propellants, two are filled with Unsymmetrical Dimethylhydrazine and two contain Nitrogen tetroxide Oxidizer.

The other two ‘tanks’ are used to facilitate the avionics including the Biser-6 flight computer and the batteries. This allows for a simplified manufacturing process and provides a simple solution for environmentally controlling the systems.

Fregat is available in several configurations – Soyuz uses the conventional Fregat, the Fregat-M and the Fregat-MT.

In the Fregat-M version, the upper stage features propellant tank extensions. Two spherical extensions are welded to each of the four main propellant tanks – these extensions add 30kg in mass to the stage and hold up to 500kg of additional propellant. The MT version uses larger extension tanks that weigh 120 Kilograms and carry 1,850kg of additional hypergolic propellant.

These tank extensions have been developed to allow Fregat to carry more propellant while maintaining its normal mass characteristics for easy flight program development. Anther version, Fregat-SB, is used on the Zenit Rocket carrying an additional toroidal propellant tank.

Fregat uses heritage components to provide high reliability during its missions. The S5.92 Main Engine has been in use for more than 30 years and the Control System of the Vehicle features redundant components and has been used on a number of missiles and launch vehicles.

Image: NPO Lavochkin
Image: NPO Lavochkin

Fregat uses heritage components to provide high reliability during its missions. The S5.92 Main Engine has been in use for more than 30 years and the Control System of the Vehicle features redundant components and has been used on a number of missiles and launch vehicles.

The S5.92 main engine of the Fregat upper stage is a hyperbolic turbopump-fed main engine that uses a staged combustion cycle. A small amount of propellant is burned inside a gas generator that drives the turbine powering the turbopumps for the oxidizer and fuel. The exhaust is expelled via two nozzles. Propellants injected into the main combustion chamber are responsible for generating the majority of the thrust of the engine.

Photo: Arianespace
Photo: Arianespace

S5.92 can be operated at a full thrust level of 19.85 Kilonewtons and a reduced thrust level of 14kN, allowing it to fly a variety of mission profiles. The engine is 0.84 meters in diameter and 1.03 meter long, with an inert mass of 80 Kilograms. Depending on the thrust setting, the engine operates at a chamber pressure of 6.85 to 9.8 MPa and generates a specific impulse up to 331 seconds. It can be re-started up to 20 times.

The main engine can be gimbaled to provide pitch and yaw control during operation. For roll control during burns and three-axis control in coast phases, Fregat is equipped with 12 S5.221 attitude control thrusters. These thrusters use Hydrazine monopropellant stored in two tanks that are installed on Fregat, containing up to 85kg of propellant.

The thrusters are installed in four pods – each pods contains two pitch/yaw thrusters and one roll thruster, each delivering 50 Newtons of thrust. The thrusters are also used for propellant setting burns ahead of main engine firings.

Pressurization of the main propulsion system and the attitude control system is accomplished using high-pressure Helium that is stored in spherical tanks, each with a volume of 23 liters. The number of tanks depends on the version of Fregat that is used and the chosen flight profile. Fregat is also used for pneumatics – valve and engine actuation.

Fregat, Fregat-M & Fregat-MT
Image: NPO Lavochkin
Image: NPO Lavochkin


Payload Fairing

Photo: RSC Energia
Photo: RSC Energia

The Payload Fairing is positioned on top of the stacked vehicle and its integrated payloads. It protects satellites or other spacecraft against aerodynamic, thermal and acoustic environments that the vehicle experiences during atmospheric flight. When the launcher has left the atmosphere, the fairing is jettisoned by pyrotechnically initiated systems. It is separated during second stage flight. At that point, aerodynamic and thermal loads are acceptable for the spacecraft to be exposed after the launcher has left the dense portion of the atmosphere.

For the Soyuz-U, there are two basic payload fairing sizes. One is used to launch the Progress Spacecraft while the other is used for flights with optional Upper Stages like Fregat.

Photo: RSC Energia
Photo: RSC Energia