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Manned Lunar Missions: An Exercise in Propulsion Trades and Sensitivities
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Abstract
A recent study performed for the In-Space Propulsion Technology Office at the Marshall Space Flight Center investigated the effects of using different propellant types on the different stages required to perform a manned lunar mission. The original study included investigations into propellant type, propellant storage technology options and sensitivities to specific impulse variations for a lunar orbit rendezvous mission. The initial mission characteristics were based on previous work led by Langley Research Center. Outlined in this paper are the results of that study and the work that followed. A lunar direct return architecture was added to the analysis. Since both architectures required assembly of the various propulsive stages in low Earth orbit and multiple launches to deliver those stages, investigations of launch sequence and scheduling sensitivities were also included. Results show that lunar direct return architectures require more mass to complete missions when compared to lunar orbit rendezvous missions. Within the given architectures, trends in the results tended to be very similar with the architectures indicating very little sensitivity to launch sequence and specific impulse variations and indicating more sensitivity to the propellant choice made for each stage and the time between launches. Even though this study investigates a small subset of the possible lunar architecture trade space, it does begin to outline some of the issues that must be investigated and the characteristics of the mission and the mission elements that are of most importance to a full architecture assessment