DESCENT PROPULSION SYSTEM PROPELLANT BUDGET DESCENT PROPULSION SUBSYSTEM (DPS) - The DPS budget is shown in table 5-8 and the ground rules and assumptions in table 5-9. Previously, the uncertainty in the low-level sensor (68.7 lb) has been shown as a contingency allowance. This is now included as part of the unusables. Also, there has previously been a contingency allowance for manual hover to allow for 2 minutes of burn time from 500 feet to touchdown. The present budget shows a nominal ∆V which includes a manual allowance of 477 fps (90 sec) from 500 feet to touchdown. Any additional hover time will be used from the propellant margin (unassigned capability). The rate of use for hover is approximately 9.1 lb/sec. Propellant loads are those actually loaded on LM-5, and trapped and residual propellants are from Volume III, SODB. Engine performance data and ∆V requirements have been coordinated with LAB in MPAD. Three sigma dispersions represent total propellant cost due to 3 s uncertainties in propellant loading, trapped, Isp, ∆V, separation weight, non-∆V consumables weight, and mixture ratio. There is a total propellant margin of 669 lb or approximately 73 seconds of hover time. Table 5-8 – APOLLO 11 DPS PROPELLANT SUMMARY PROPELLANT PROPELLANT ITEM REQUIRED, LB REMAINING, LB Loaded a -- 18184.2 Trapped and unavailable 223.5 17960.7 Outage 14.0 17946.7 Low-Level Sensor Uncertainty 68.7 17878.0 Available for ∆V -- 17878.0 Nominal Required for ?V of 6728.6 fps 16799.7 1078.3 Dispersions (-3 σ) 224.7 853.6 Contingencies Engine Valve-Pair Malfunction (∆MR=±.016) 81.1 772.5 Redesignation (60 fps) 104.0 668.5 Margin (73 sec. hover) -- 668.5 a 6974.8 lb of fuel and 11209.4 lb of oxidizer this is loaded on the LM-5 spacecraft. 5 - 26