Apollo Saturn User Manual download pdf (Page 57)

S-II STAGE THRUST VECTOR CONTKOL SYSTE_I

: The four outboard J-2 engines are gi_bal mounted to provide thrust vector ._

eontro] during powered flight. ,\t'_tude c_ntr61 is maintained by gimballing the

outboard engines in response to electrical control signals flora the IU flight _._

_'ontroi computer.

i The system consists of four independen_ closed-loop hydraullc control ,_

subsystems which provide power for engine gimballing. The primary components

of the subsystem are an auxiliary pump, a main pump, an accum,.,iator/_eservoir _

: manifold assembly and two servo actuators. The auxiliary pump is electrically . ._

driven from the GSE to prov.ide hydraulic fluid circulation prior to launch. The

, main pump is mounted to and driven by the engine LOX turbopump. The accumulator/ ._

.... _,_ .,o_,,,_j consisEs of _ pressure _cumu±_Lu_h_g,L which r_c,:iv_

' _ high pressure fluid from the pump and a low pressure reservoir which receives re-

_ turn fluid from the servo actuators. The servo actuator is a power control unit that

converts electrical signals and hydraulic power into mechanical outputs that gimbal

i the engine.

! During the preTaunch pcriod, the auxiliary hydraulic pump circulates the ._

i hydraulic fluid to preclude fluid freezing during propellant lo_ding. Circula-

tion is not required during the S-IC burn due to the short duration burn. After a

! S-IC/S-II separation, an S-II switch selector command unlocks the accumulator

I lock up val_,es, releasing high pressure fluid to each of Zhe servo actuators.

The accumulator_ provide gimballing power prior to the m.._inhydraulic pump

operation. During S-If mainstage operatiou, the m_lu hydraulic pump supplies

high pressure fluid to the servo actuators. The r_turn fluid from the actuators

! is routed to the reservoir which s_ores hydrarlic f_uid at sufficient pres_,,re

i to supply a positive pressure at the main pump inlet°

7; 6_

] 9700] ] 707-057

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Apollo Saturn User Manual Page 57