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AUK_LIAR¥ PROPULSION SYST_

The S-1VB Auxiliary Propulsion System (APS) provides vehicle attitude control

_. ._,jringpowered flight in the roll axis only and durln B S_IVB coast provides

contzol in the pitch, yaw, and roll axes. Attitude corrections ar_ made by firing

the control englnes, indivld,:ally or in combination, in short bursts of approxl-

¢ -

mately 65 ms minimum duration, Commands from the Flight Control Computer actuate "

fuel and oxidizer solenoid valve clusters that admit hypergolic propellants to •

the control engine combustlon chambers. 4

The attitude control engines are located in two aerodynamically shaped ._.

i modules, 180 degrees apart, on the aft end of the S-IVB s_age (positions I and

I!I). Each module contains four hypergolic engines, three 150 pound thrust :

,; , ".- attitude control engines and one 70 pound thrust ul3age engine. The 70 pound

!. • thrust (ullage) engine £n each module is used to settle the main stage propel-

' I lants a§ter SrlVB cutoff and again prior to restart. One control engine of

_ each module is used to control the vehicles' attitude in pitch, while the other ,

two are used for yaw and roll control.

Each APS module contains its own propellant supply and pressurization system•

': _ The hypergolic propellanLs used by the engines are monomethyl hydrazine _)

i for the £uel and nitrogen tetroxide (N20_) for the oxidizer_ Helium is the

pressurant used in the system.

•

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Apollo Saturn Manual do Utilizador Página 71