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 SERVICE MODULE REACTION CONTROL SYSTEM PROPELLANT MANAGEMENT

This discussion of the Service Module RCS propellant management philosophy was not presented during the symposium due to lack of time. It is included in this report to illustrate how the maneuver requirements are being planned to provide maximum propellant reserves to accommodate contingencies.

The Service Module RCS system is used for spacecraft attitude control and for small velocity changes, such as providing main engine ullage.

Figure 1 shows the key points of the SM-RCS propellant usage philosophy. An austere baseline was developed in which only those maneuvers absolutely required were allowed. In addition, the maneuvers allowed are performed with minimum practical rates with maximum utilization of roll maneuvers instead of pitch or yaw to take advantage or the lower inertia. Planning to fly the mission in this way will assure maximum propellants for both expected and unexpected contingencies.

Expected contingencies, that is, contingencies for which ROS propellants have been specifically budgeted are loss or one quad, LM rescue and failure of the MSFN navigation loop. If no contingencies occur prior to the LM rejoining the CSM, then the propellant margin can be used for non—essential maneuvers to further enhance the mission accomplishments

Figures 2 and 3 show the key features of the austere baseline.

Maneuver requirements during earth orbit are provided by the S-IVB stage reaction control system; hence, these requirements are not included on these figures. Navigation sightings can be made in earth orbit using the S-IVB RCS should this prove to be desirable. The SM RCS is first used for transposition and docking, as described in the session on the general mission description.

MSFN is the prime source of navigation data and only two mid— course corrections are expected during the translunar and transearth phases: one near each end of the phase. The majority of the transit time is spent in a thermal roll mode in which the spacecraft is rolled about its longitudinal axis which is maintained within ± 20° of normal to the vehiclecsun line. In lunar orbit, MSF'N is again the prime source of navigation data; however, some sightings will he taken on the landing, area for altitude refinement and on a