Apollo Saturn User Manual download pdf (Page 73)

S-IVB STAGE PROPELLANT MANA(;L'MENTSYSTE,_!

The propellant manap, er_ent system provides a means for _ontrolling and

monitoring prope]lant_ during ground loadin_., powered flight and engine shut-

down,

Continuous capacitance probes and point level sensors in the LOX and LH2 ,

tanks monitor propellant mass. During the propellant loading sequence, a signal . wmi

from each capacitance probe is transP._,ttcd from the on board propellant elec- •

' iron!c__ to GS£ +o _,',_-'_ _,_ level _ ..... 11.....in the _-"'....

; ................ v."r ................ Overfill pG_,_,.

level sensors are pxc.-,ided for LOX and LH 2 systems, k_en the propellant mass in the

; tanks re_ch a predetermil_ed _=.__t,-,- the GSE loading co_.,_uterautomatically stops ,

; the loading sequence.

J i

!_ The propellant utilization (PU) subsystem controls the mixture ratio (MR)

_' of the LOX/LH 2. The PU subsystem consists of a rotary valve, t_ control _ ,e

t : amount of LOX flowing to the engine, and electrical controls for th._valve.

The }LRis controlled by _he switch selector outputs wh'_ch are used to _perat_

: the PU valve.

Prior to engine start the PU valve is commanded to the neutral position to

= obtain a MR of 5.0:I. Th_ PU valve remains at the 5,0:I posltloll during the

: first burn. Prior to engine restart (first opportunity) the FU valve xs tom-

• mended by the switch selector to a MR of 4.5:1 and remains at this position for

_ _ appruxlnmtely one minute m:d 55 seconds of the S-IVB burn. The PU valve is then

commanded to the neutral position (5.0:I). If the S-IVB restart is delayed to

: the second opportunity, the MR is shifted from 4.5:1 to 5.0:1 when the engine

j, •

• reaches 90 percent thrust.

"__ Engine shutdown, during first burn, is initiated by a programmed command

2 (velocity) from the IU through the switch selector. Engine shutdown after

_ second burn is Init_e_.c_ by a programmed conma,,d (velocity) from the IU through

_ the S-IVB switch selector. Backup shutdown is provided by any two of the five

liquid level sensors in either, propellant tank indicating propellan ._ depletion.

_i ,"

] 9700] ] 707-076

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Apollo Saturn User Manual Page 73