Tank pressure control of the S-IB stage

To obtain a proper flow of propellants towards the eight H-1 thrust engines, the tank pressure has to be kept within a certain range of pressure values. These conditions are achieved by using a pressure relief system and a gas supply system. Pressure sensors monitor the tank pressure and will trigger the relief system and the gas supply system respectively, when the pressure has become too high or too low.
During the first stage boost phase, the heart of both systems is formed by the pressure control modules. These modules are linked to the pressure sensors and a network of valves and make a proportional control of the tank pressure possible.
Prior lift-off, during pre-pressurization, the pressurization gas is supplied from separate regulated ground sources for each propellant tank.

The relief system is basically a vent system. Each propellant tanks has two vent valves.

The S-IB stage is has a cluster of nine tubular shaped propellant tanks. Four non cryogenic RP-1 fuel tanks and five cryogenic Oxygen tanks. Two modes of operation can be distinguished for the tank pressurization:

  1. Prior lift-off
    The pressurization process is called pre-pressurization. Helium gas is used as the pressurization gas and is supplied by the ground source equipment (GSE).
  2. During the the burn of the eight H-1 engines of the S-IB stage
    During these phases of the flight when liquid Oxygen and RP-1 fuel is consumed by the H-1 engines, a high flow rate of pressurization gas is required to achieve the proper tank pressure. The five cryogenic liquid Oxygen tanks are pressurized with gaseous Oxygen which is obtained by tapping off a small fraction of the liquid Oxygen routing it through heat exchangers which are mounted against the H-1 enigines. In order to pressurize the four non cryogeninc fuel tanks, Helium gas is used which is supplied by the two high pressure storage spheres, which are located on top of two fuel tanks.
Mode 1
Mode 2

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Copyright 2005 by   Sander Panhuyzen
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