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The NASA Exploration Systems Architecture Study (ESAS) produced a transportation architecture for returning humans to the moon affordably and safely, while using commercial services for tasks such as cargo delivery to low earth orbit (LEO). Another potential utilization of commercial services is the delivery of cryogenic propellants to LEO for use in lunar exploration activities. With in-space propellant re-supply available, there is the potential to increase the payload that can be delivered to the lunar surface, increase lunar mission durations, and enable a wider range of lunar missions. The addition of onorbit propellant re-supply would have far-reaching effects on the entire exploration architecture. Currently 70% of the weight delivered to LEO by the cargo launch vehicle is propellant needed for the TLI burn. This is a considerable burden and significantly limits the design freedom of the architecture. The ability of commercial providers to deliver cryogenic propellants to LEO may provide for lower cost and better performing lunar architecture.

The NASA Exploration Systems Architecture Study (ESAS) produced a transportation architecture for returning humans to the moon affordably and safely, while using commercial services for tasks such as cargo delivery to low earth orbit (LEO). Another potential utilization of commercial services is the delivery of cryogenic propellants to LEO for use in lunar exploration activities. With in-space propellant resupply available, there is the potential to increase the payload that can be put on the moon, increase lunar mission durations, and enable a wider range of lunar missions. The availability of on-orbit cryogenic propellants, either at a propellant depot or directly from a propellant transfer stage, would impact the sizing and reusability of many architecture elements, including the Earth Departure Stage (EDS), the Crew Launch Vehicle (CLV) upper stage, the Lunar Surface Access Module (LSAM), and the Service Module (SM). These vehicles are modeled to approximate the baseline established by ESAS. Methods and tools used include launch trajectory optimization with POST, vehicle aerodynamic analysis using APAS, weights and sizing using historical and physics based estimating relationships, and cost estimation using NAFCOM. Uncertainty in estimates of advanced technology performance is modeled using probabilistic methods, such as Monte Carlo simulation. The impact of propellant resupply capability on vehicle design and performance is investigated. The availability of propellant at LEO allows for many possible architecture changes, including increasing the payload delivered to the moon, decreasing the size of the heavy lift launch vehicle, or staging extra propellant in lunar orbit. Other elements could also be designed to be reusable with propellant resupply available, such as the LSAM, the CLV upper stage, and the Service Module. Several of these architecture changes are investigated, and compared via metrics such as mission reliability, cost, and the range of lunar and near-Earth mission capabilities (i.e. duration time, mission latitude, missions to Lagrange points) they allow.

This paper reports on an investigation of possible Launch and Trans-Mars Injection options using the Exploration Systems Architecture Study (ESAS) Cargo Launch Vehicle (CaLV) and Earth Departure Stages (EDS) for crewed Mars missions The purpose of such an investigation is to characterize some of the potential challenges and technological needs for modifying the present lunar architecture for transport to Mars. An analysis was performed to provide a relationship between the payload placed in orbit, usable propellant available in orbit, and the required propellant to perform the Trans-Mars Injection. This relationship was used to investigate several payload manifests and launch strategy options and to perform some trades to identify advantageous launch solutions. The Mars Design Reference Mission from 1998 was used to provide a representative Mars payload and mission architecture for the study. It was found that 6 and 5 launch solutions are possible without the implementation of any new technologies. It was also found that adding the ability to efficiently transfer propellants between Earth Departure Stages and developing boil-off elimination technologies improves performance to 4-launch solutions. Further reduction of launches exceeds constraints on the launch vehicle such as payload capacity and height constraints.

41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit July 10-13, 2005, Tucson, AZ.

41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit July 10-13, 2005, Tucson, AZ.