In-situ lunar oxygen production has the potential to reduce the cargo mass launched from Earth necessary to sustain a lunar base. As research and development in lunar oxygen production continue, modeling tools are being used to help characterize the many possible system architectures and guide decisions for future plant designs. Using the previously built NASA In-Situ Resource Utilization (ISRU) System Model, an optimization tool was developed to facilitate exploration of the design space of the different system architectures represented in the model. For each architecture, an optimization of the continuous design space is performed using a gradient-based search. In instances when the gradient-based search cannot converge, the tool changes to simulated annealing, a heuristic method. Nine primary lunar oxygen production system architectures were optimized to minimize system mass for oxygen production levels from 500 kg/yr to 6000 kg/yr. Good designs minimized mass and maximized produced oxygen with system masses in the range of 100 kg to 700 kg. Preliminary results show that two particular architectures populate the Pareto-optimal front of best designs for most production levels, making them attractive for further investigation. An economy of scale of .837 was found using a power law regression, indicating that some economy of scale exists (values less than one have economy of scale) and that launching fewer, higher-capacity plants will be less massive overall than many small-capacity plants to achieve the same total production level. A simplified comparison of lunar-produced oxygen for crew breathing supply and ECLSS (environmental control and life support systems) technologies was performed with a space logistics planning tool, SpaceNet. For all but the most advanced ECLSS technologies, use of in-situ oxygen over a 10-year campaign resulted in more than 12,000 kg of consumables cargo launch mass savings.
Nomenclature
= economy of scale C = investment cost
Component and system sensitivities of some design parameters of ISRU system components are analyzed. The differences between terrestrial and lunar excavation are discussed, and a qualitative comparison of large and small excavators is started. The effect of excavator size on the size of the ISRU plant's regolith hoppers is presented. Optimum operating conditions of both hydrogen and carbothermal reduction reactors are explored using recently developed analytical models. Design parameters such as batch size, conversion fraction, and maximum particle size are considered for a hydrogen reduction reactor while batch size, conversion fraction, number of melt zones, and methane flow rate are considered for a carbothermal reduction reactor. For both reactor types the effect of reactor operation on system energy and regolith delivery requirements is presented.
This paper gives an overview of the National Aeronautics and Space Administration (NASA) Office of Chief Technologist (OCT) led Space Technology Roadmap definition efforts. This paper will given an executive summary of the technology area 07 (TA07) Human Exploration Destination Systems (HEDS). These are draft roadmaps being reviewed and updated by the National Research Council.
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