1. In 2004, the President announced the Vision for Space Exploration,2in which he detailed plans to develop the Crew Exploration Vehicle and return to the Moon and ultimately send humans to Mars. This announcement initiated several iterations of studies that are ongoing to evaluate how to get the Moon and what is necessary to sustain a human presence there. The first major study, the Exploration Systems Architecture Study (ESAS), established the initial designs for Orion, Ares I, Ares V, and Altair spacecraft as well as the beginning of the Iunar surface systems studies.3After the ESAS completed, the Lunar Architecture Team (LAT) was created to explore the surface architecture and its interactions with the transportation systems in more detail. The first iteration of the LAT studies focused on refining the ESAS results and was announced by NASA in December 2006.4The second iteration of LAT studies expanded the options to include a cargo lander and a mobile lander design. Its results were presented at AIAA Space 20075and other forums.6,7The LAT studies are ongoing and continue to both refine and expand the options in preparation for more detailed design efforts in the future. The latest results were presented in support of a milestone entitled the Lunar Capability Concept Review in June 20088and at other meetings as well.9NASA has also emphasized the opportunity for international and commercial partnerships in the lunar surface architecture.10
2. At the elevated polar sites, the solar illumination profile is governed more by the horizon terrain than by the orbital mechanics of the Sun-Earth-Moon system. The Sun is typically near the horizon at these sites and can be occulted by hills and other terrain a significant distance away. Detailed topographical maps and elevation models are lacking for the polar regions due the remote location and distance from past missions to the Moon. In the past decade there has been significant work in this area to interpret the available data and produce new elevation models. Summary of the past work has been documented in several papers by Fincannon.12-14These papers also produced digital elevation models for the north and south polar regions as well as horizon profiles for specific sites near the poles. This paper focuses on one site identified as Site 4RS13near the Shackleton Crater rim. Figure 1 shows an estimate of the horizon profile and Sun centerline position for January 2020 at Site 4RS. For this time period and location, the Sun is completely unocculted.
3. The hydrogen and oxygen tanks are based on composite overwrapped pressure vessel technology. The pressure of the tanks is assumed to be driven by the electrolyzer stacks and the maximum pressure most likely will be between 13.8 and 20.7 MPa (2000 and 3000 psi). The tanks are sized to hold the necessary hydrogen and oxygen including the amount needed to prevent greater than 90% ’depth-of-discharge,’ as in the battery case. For this study, the dry mass of the hydrogen tank is calculated from an assumed constant 10% hydrogen mass fraction. Similarly, the dry mass of the oxygen tank is calculated from an assumed constant 50% oxygen mass fraction. The equation used is mtank;dry =mfluid
4. 2020 2021 2022 2023 2024 2025 2026 202( 2028 2029 2030 0 0.2 0.4 0.6 0.8
5. Figure 9. Plot of state-of-charge for the battery subsystem for the entire 2020 - 2030 period. The total battery energy is 362 kWhr, the solar array area is 43.6 m2and the BOL solar array power is 11.7 kW. This system is Option 1 in Table 1. Adding another 9 m solar array is shown as Option 3. The battery subsystem is significantly reduced at the expense of two large solar arrays producing 33.9 kW of BOL power where only 5 kW is required for the daytime power load, which is probably unrealistic from an outpost perspective. Option 2 is chosen for further analysis. Figures 10 and 11 show the Option 2 state-of-charge detail for years 2020 and 2029. These plots show typical years and the changes over the decade for the battery subsystem. Figure 12 shows the estimated charge and discharge rates for the Option 2 battery subsystem.