Searching for details:
The author of this page will appreciate comments, corrections and imagery related to the subject. Please contact Anatoly Zak.
Above: Exterior design of Zenit's first stage.
Previous chapter: Zenit rocket
The architecture of Zenit's first stage, first of all its length and diameter, was dictated primarily by the requirement to fit it into the railway transporter. The price of this advantage was a less-than-optimal distribution of propellant components between two stages. Still, engineers went to a great length to pack maximum propellant volume into the minimal length of both stages.
The second stage is manufactured out of the AMg-6 alloy and welded together to form four main components: oxidizer tank, intertank structure, fuel tank and tail section. These are bolted together to form the first stage.
The long oxidizer tank is comprised of 11 ciclindrical rings and closed off by two hemispheres on both ends. Two rows of titanium tanks for helium gas are located inside the tank close to its bottom. After heating, this gas is used to pressurize both propellant tanks, in order to force their content into the engine. The bottom part of the oxidizer tank connects to the inter-tank ring, which has special hatches used during the rocket's assembly. An oxidizer supply line exits its tank and runs through the fuel tank to reach the engine below.
The lower fuel tank has inverted hemispherical ends designed to save some length of the stage by partially accomodating the end of the oxidizer tank above and the propulsion system below. (264) This volume-saving measures made Zenit one of the most "condensed" launch vehicles in the world. (630)
The tail section with a diameter of 3.7 meters and the fuel tank are connected via a load-bearing ring, which attaches to the launch pad. Launch pad mechanisms hold the rocket by this ring during the liftoff, until the diagnostics system confirms that the main engine had reached the nominal thrust for the flight. The tail section also carries four 8D84 solid-propellant braking motors, which fire as soon as links between two stages of the rocket are cut off in flight to ensure safe separation between two stages. (264)
Specifications of the first stage of the Zenit rocket:
Next chapter: Zenit's Stage II
This page is maintained by Anatoly Zak
Last update: February 4, 2013
All rights reserved
An early version of the Zenit rocket featured a skirt-like structure protecting combustion chambers on the first stage. Credit: KB Yuzhnoe
A tail section of the Zenit's first stage with a four-chamber RD-171 engine and four 8D84 solid-propellant motors. Copyright © 2000 Anatoly Zak
An interstage structure connecting first and second stages of the Zenit-2 vehicle. Copyright © 2000 Anatoly Zak