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Stage 2




Stage 2


Above: Artist rendering of Zenit's second stage. Copyright © 2011 Anatoly Zak

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Previous chapter: Zenit's first stage

In most missions of the Zenit rocket, its second stage would have a job of placing its payload into the low Earth orbit. The 11-meter rocket stage was equipped with the RD-120 main engine and the RD-8 steering engine, both burning a mix of liquid oxygen and kerosene.

Structurally, the stage consists (from top to bottom) of an avionics (or instrumentation) section, an oxidizer tank (for liquid oxygen), intertank section, fuel tank (for kerosene) and a tail section. In in addition, during the assembly of the Zenit launch vehicle, a truss connecting the second and the first stage is first attached to the second stage. However during the flight, this truss remains on the first stage following its separation.

The avionics/instrumentation section contains the launch vehicle's flight control system with all its components housed in pressurized containers. This section also bears loads from the hardware holding the spacecraft above and from the payload fairing. The intertank structure is welded out of components made out of the AMg-6 alloy. It is bolted to the both tanks of the stage.

The oxidizer tank of the second stage also contains helium tanks, which are used to pressurize the fuel tank below. The fuel tank has a thorus shape, which forms an opening for the RD-120 main engine developed at NPO Energomash in Moscow. The main engine is fixed to the stage, providing 249 seconds of thrust during a typical mission. All steering is achieved via four nozzles of the RD-8 engine developed at KB Yuzhnoe in Dnepropetrovsk. The steering engine is attached to the aluminum tail section of the rocket.

The active phase of the second stage flight lasts around 315 seconds. Upon completing its mission, links between the second stage and its payload are cut and the second fires four 15D4 solid-propellant motors installed at the tail of the rocket body to separate itself from its cargo.

Known specifications of the Zenit's second stage:

Weight (fueled)

89.5 tons

Dry weight

8.9 tons

11.047 meters
3.900 meters
Burn time
249 seconds (main engine)
2nd stage propulsion
  • 1 (one) one-chamber RD-120 engine (11D123)
  • 1 (one) four-chamber 11D513 steering engine
  • 4 (four) 15D4 solid-propellant braking motors

Next chapter: Zenit's flight history


Page author: Anatoly Zak; Last update: January 31, 2013

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Artist rendering of the Zenit's second stage drifting in orbit after the delivery of its payload. Copyright © 2001 Anatoly Zak


The RD-120 (11D123) engine powers the second stage of the Zenit launcher. Copyright © 2001 Anatoly Zak


An interstage structure connecting first and second stages of the Zenit-2 vehicle. Copyright © 2001 Anatoly Zak

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