Zenit-3SLB – Launch Vehicle

Photo: RSC Energia
Photo: RSC Energia

The Zenit-3SLB Launch Vehicle is an expendable carrier rocket that is part of the Zenit Rocket Family. Zenit 3SLB is operated by Land Launch – a subsidiary of Sea Launch which is owned by RSC Energia (40%), Boeing (25%), Aker Solutions (20%) and Yuzhnoye (15%). The Rocket was designed by the Yuzhnoye Design Bureau and is constructed by Yuzhmash, both Ukraine.

Development of the Zenit 3 Rocket Family began back in 1980 for two purposes. Its first stage was intended as booster for the Energia launch vehicle, and equipped with a second stage, the vehicle was designed as an independent launcher. Zenit 3SL made its maiden flight in 1999 while the SLB version first flew in 2008. Since then, 35 launches of the 3SL version have taken place to date with three failures and one partial failure. Land Launch has flown five Zenit Missions – all successful.

Zenit-3SLB is based on the Zenit-3SL launcher that is modified to launch from the Sea Launch Odyssey Platform. The SLB version differs from the SL version in its Upper Stage Design as it uses the Block DM-SLB and in its payload fairing provided by NPO Lavochkin. The vehicle is based on the Zenit-2SB launcher with the addition of a third stage to target a number of different orbits. Zenit-2SLB is also available for launches to low orbits.

For Government launches, the upgraded Zenit flies under the 2M and 3M designation.

Zenit-3SLB is operated from existing Zenit-2 facilities at Site 45, Baikonur Cosmodrome, Kazakhstan. The vehicle can reach a variety of orbits including Geosynchronous Transfer Orbit, Medium Earth Orbit and Geosynchronous Orbit.

Photo: RSC Energia
Photo: RSC Energia


Zenit-3SLB Specifications

Type Zenit-3SLB
Height 58.65m
Diameter 3.9m
Launch Mass 462,650kg
Stages 3
Stage 1 Zenit 2 First Stage
Stage 2 Zenit 2 Second Stage
Upper Stage Block DM-SLB
Mass to LEO 13,500kg
Mass to GTO 3,750kg
Mass to MEO 4,830kg
Mass to GSO 1,600kg

The Zenit-3SLB Vehicle consists of the basic two-stage Zenit 2 design with two lower stages fueled by Liquid Oxygen and Kerosene. The two integrated stages are 43.3 meters long and 4.1 meters in diameter. Atop the second stage, the Block DM-SLB Upper Stage is installed which is based on the Block-DM Upper Stage which in turn is a modification of the historic Block-D. The launch vehicle is topped by a 4.1-meter diameter Payload Fairing.

Major configuration improvements have been made distinguishing the Zenit-3SLB Vehicle from its predecessors, namely the Zenit-3. These modifications include new avionics, navigation computers as well as mass reductions and structural improvements.

Zenit-3SLB stands 59.65 meters high and has a diameter of 3.9 meters.

In its 3SLB configuration, the vehicle is almost exclusively used for launches to Geosynchronous Orbit or Geosynchronous Transfer Orbit. It can carry payloads of 1,600 Kilograms directly to Geosynchronous Orbit.

Image: RSC Energia
Image: RSC Energia


First Stage

Sea Launch First Stage = Land Launch First Stage - Photo: Sea Launch
Sea Launch First Stage = Land Launch First Stage – Photo: Sea Launch
Type Zenit 2 First Stage
Length 32.9m
Diameter 3.9m
Inert Mass 27,564kg
Launch Mass/Fueled 354,350kg
Fuel Rocket Propellant 1
Oxidizer Liquid Oxygen
Fuel Mass 90,219kg
Oxidizer Mass 236,567kg
Material Aluminum, Stiffeners
Guidance From 2nd Stage
Propulsion 1 RD-171
Engine Type Staged Combustion
Propellant Feed Turbopump
Comb. Chambers 4
Total Thrust SL 7.550MN
Total Thrust Vac 7.887MN
Engine Length 4.00m
Engine Diameter 3.57m
Engine Dry Weight 9,500kg
Nozzle Ratio 36.87
Thrust-to-Weight 82
Burn Time 150s
Specific Impulse 309s (SL) 338s (Vac)
Chamber Pressure 245bar
Throttle Capability 56%-100%
Engine Start Hypergolic
Restart Capability No
Ox to Fuel Ratio 2.63
Attitude Control Gimbaled Engine (Pitch, Yaw, Roll)
Max Gimbal 6.3deg
Shutdown Commanded Shutdown

The first and largest stage of the Zenit-3SLB Rocket has an inert mass of 27,564 Kilograms. It consists of the central tank containing 236,567 Kilograms of Oxidizer, Liquid Oxygen, and the fuel tank holding 90,219 Kilograms of Rocket Propellant 1 which is rocket-grade Kerosene.

The first stage tanks are made of aluminum and features stiffeners for structural integrity. The stage is 32.9 meters long and 3.9 meters in diameter.

The first stage is equipped with one RD-171 Main Engine. This single engine is powering the entire vehicle following liftoff.

RD-171 is the most powerful rocket engine of the world. It provides 7,550 Kilonewtons (770,000 Kilograms) of Thrust at Sea Level.

The Main Engine has four combustion chambers, all fed by a single, vertically mounted turbopump, powered by two gas generators feeding hot oxidizer-rich gas to a single turbine. RD-171 provides throttle capabilities ranging from 56% to 100% of rated performance which is used to limit stress on the vehicle during ascent.

The Engine weighs 9,500 Kilograms, is 4 meters long and has a diameter of 3.57 meters. First stage attitude control is provided by gimbaling each nozzle individually by a hydraulic system by a so-called BIM hydraulic pump.

The BIM pump assembly consists of two turbopumps, one is driven by high-pressure helium and one uses Kerosene provided by the RD-171 fuel subsystem. When being powered with helium, the BIM reaches an intermediate power level which is increased to full hydraulic pressure when BIM switches to the Kerosene pump.

Guidance data is provided to the first stage by the Navigation System that is installed on the second stage. The first stage is separated from the launch vehicle 150 seconds into the mission. Zenit uses a hot-staging technique – igniting the second stage and simultaneously firing pyro bolts to have the first stage pushed away by second stage exhaust.

Photo: NPO Energomash
Photo: NPO Energomash


Type Zenit Second Stage
Length 10.4m
Diameter 3.9m
Launch Mass/Fueled 90,794kg
Inert Mass 8,307kg
Fuel Rocket Propellant 1
Oxidizer Liquid Oxygen
Fuel Mass 23,056kg
Oxidizer Mass 59,431kg
Propulsion 1 RD-120 + 1 RD-8 (Vernier)
Engine Type Staged Combustion
Propellant Feed Turbopump
Total Thrust Vac 833kN
Engine Length 3.87m
Engine Diameter 1.95m
Engine Dry Weight 1,125kg
Thrust-to-Weight 75.6
Burn Time 315s
Specific Impulse 350s (Vac)
Chamber Pressure 162.8bar
Ox to Fuel Ratio 2.6
Attitude Control Gimbaled Engine (Pitch, Yaw, Roll)
Vernier Engine RD-8 – 4 Chambers
Propellant LOX/RP-1
Type Staged Combustion
Thrust 78.5kN
Specific Impulse 342s
Engine Length 1.67m
Engine Diameter 4.0m
Dry Weight 380kg
Max Burn Time 4,000s
Vernier Impulse 342.8s
Control Vernier Gimbal +/-33 Degrees
Braking Motors 4 15D4 (Solid Fueled)

Second Stage

The second stage of the Zenit closely resembles the first stage design with its fuel tank located above the oxidizer tank. The stage is 10.4 meters long and 3.9 meters in diameter with an inert mass of 8,307 Kilograms.

The second stage also uses Rocket Propellant 1 and Liquid Oxygen as propellants.

It holds 23,056kg of Kerosene and 59,431kg of LOX that are used during 315 seconds of powered flight before the stage is separated from the orbital unit consisting of payload and upper stage.

Stage 2 is powered by a RD-120 Main Engine and a RD-8 Vernier Thruster featuring four gimbaling nozzle that are used to provide three-axis control during the burn.

RD-120 provides 833kN (84,950kg) of thrust while the vernier engine has a nominal thrust level of 78.5kN (8,000kg).

RD-120 is a single chamber engine operating at a chamber pressure of 163 bar. It is fixed and can not be moved – requiring vernier engines to provide vehicle control. The engine can be throttled back to 78%.

During the second stage burn, the Payload Fairing is jettisoned to improve ascent performance – exposing the satellite as soon as thermal and aerodynamic loads are within limits. The second stage also houses the guidance system and flight computers of the vehicle that autonomously control all aspects of the flight.

Photo: Sea Launch
Photo: Sea Launch
Photo: NPO Energomash
Photo: NPO Energomash


Block-DM-SLB Upper Stage

Type Block DM-3SLB
Length 5.93m
Diameter 3.7m
Inert Mass 3,220kg
Launch Mass/Fueled 17,800kg
Fuel Rocket Propellant 1
Oxidizer Liquid Oxygen (Sub)
Propellant Mass 14,580kg
Propulsion 1 RD-58M
Total Thrust Vac 83.4kN
Engine Length 2.27m
Engine Diameter 1.17m
Engine Dry Weight 300kg
Thrust-to-Weight 37
Burn Time 650s
Specific Impulse 349s
Chamber Pressure 77.5bar
Ox to Fuel Ratio 2.48
Attitude Control Two Attitude Control Thrusters
4 Nozzles on each Thruster
Propellant Hydrazine
Oxidizer Nitrogen Tetroxide
Fuel Reserve 57kg

The Block DM-SLB Upper Stage represents a modification of the Block-DM Upper Stage that has first flown in 1974 and has undergone a number of major upgrades and re-designs over the decades. Originally, the Block-D originated in the Soviet Union’s lunar exploration plans. It was planned to serve as upper stage on the N1 Moon Rocket to perform burns during Earth-Moon transit.

Today, Block-D Upper Stages fly in a number of configurations, depending on the type of launch vehicle and the particular payload. Currently, Block DM-2, DM-2M, DM-03 are used on the Proton Rocket. Sea Launch uses modified Block-DM-SL Upper Stages on their Zenit 3SL launcher and Land Launch utilizes the Block DM-3SLB.

The Block-DM-SLB Upper Stage delivers payloads to a variety of orbits including low, medium and high Earth Orbits as well as supersynchronous trajectories and Earth Escape Flight Paths. Block-DM provides a precise injection capability and can support ascent missions of several hours.

The Upper Stage is built to be as small as possible to leave enough room for large payloads under the Payload Fairing. It has a dry mass of 3,220 Kilograms being 5.93 meters long and 3.7 meters in diameter.

Image: RSC Energia
Image: RSC Energia

The Upper Stage uses Liquid Oxygen as Oxidizer and Rocket Propellant 1 as Fuel. The Propellants are stored in two tanks that are part of the core module of the Vehicle. The LOX tank has a spherical shape; the kerosene tank is toroidal, inclined to 15 degrees for better fuel extraction. In total, 14,580 Kilograms of Propellants can be stored in the Block-DM-SLB’s Tanks – depending on the mission profile, the propellant load can be adjusted.

The Upper stage is powered by a single RD-58M Main Engine that provides 83.4 Kilonewtons of Thrust (8,500kg). The engine is a pump-fed engine that provides gimbaling capability. The Main Engine can be started up to 5 Times and has a fully redundant ignition system.

Attitude Control during cruise phases is provided by two Attitude Control Thrusters that are also used for ullage burns. Each attitude control engine has four nozzles that are grouped in clusters on either side of the main engine. The Attitude Control System uses Nitrogen Tetroxide and Unsymmetrical Dimethylhydrazine as propellants.

All aspects of the Block-DM-SLB Mission are controlled by the vehicle’s avionics and pre-flight commands/programs – uplink capability that was available on previous versions has been eliminated to save weight and increase performance. Block-DM-SLB has a passive and active thermal control system to keep all of its systems in operating condition during longer flights. After spacecraft separation, the Upper Stage performs Collision avoidance maneuvers or performs a deorbit maneuver, depending on the flight trajectory.

Photo: RSC Energia
Photo: RSC Energia

Block DM-SLB features several changes compared to the DM-SL Version used on Sea Launch Rockets. It uses the common Block DM infrastructure, but is outfitted with upgraded forward structural interfaces to be compatible with Russian payload fairings. Block DM-SL uses a large toroidal avionics bay while the SLB version features several smaller avionics modules to cut weight as sensors and avionics used on earlier models are removed. The telemetry system of the DM-SLB features a lighter communication system, replacing a deployable antenna with a lighter system similar to that on the Zenit launcher with fixed antennas.

The Block DM-SLB design also cut a set of Attitude Control System tanks as the system is constantly underfilled by the volume of those tanks. LOX tank pressurization is accomplished with pure Helium instead of a mixture of Helium and Oxygen. Additionally, the minimum allowable propellant mass for a stage re-start is reduced from 4,000kg to 1,500kg because propellant unsettling is prevented by two extra settling thrusters. Upper Stage mass is reduced further by cutting a thermal radiator as its function is assumed by the upper adapter structure.


Photo: Sea Launch
Photo: Sea Launch


Payload Fairing

Length 10.4m
Diameter 4.10m
Construction Bi-conic Aluminum Construction
Manufacturer NPO Lavochkin

The Payload Fairing is positioned on top of the stacked vehicle and its integrated Payload. It protects the 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.

The fairing is attached to the Block-DM-SLB Upper Stage. While the Sea Launch Version of the Zenit-3 uses a fairing provided by Boeing, the Land Launch variant uses a payload fairing manufactured by NPO Lavochkin.

The aluminum fairing is 4.1 meters in diameter and 10.4 meters long. About 1.03 meters of fairing length are required to encapsulate the Block DM-SLB upper stage.

Image: RSC Energia
Image: RSC Energia


Payload Adapter

Image: Land Launch
Image: Land Launch

Payload Adapters interface with the vehicle and the payload and are the only attachment point of the payload on the Launcher. They provide equipment needed for spacecraft separation and connections for communication between the Upper Stage and the Payload.

The separation system can be based on either the traditional pair of pyrotechnically-initiated bolt cutters or a low-shock Clamp Band Opening Device (CBOD). Several off-the-shelf adapters are available to accommodate various payloads. Also, custom made adapters can be fitted atop the Block-DM-SLB Upper Stage to accommodate a variety of different payload requirements.

Injection Accuracy
Circular GTO GEO
Perigee +/-25 km +/-40 km +/-200 km
Apogee +/-25 km +/-100 km +/-200 km
Inclination +/-0.06° +/-0.1° +/-0.2°





Photo: RSC Energia
Photo: RSC Energia