Architecture Modeling of In-Situ Oxygen Production and its Impacts on Lunar Campaigns

Abstract

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

Generalized Multicommodity Network Flow Model for the Earth–Moon–Mars Logistics System

“…The baseline problem assumes a linear ISRU resource production rate of 10 kg per year per unit plant mass. A previous study showed that ISRU plants follow economies of scale, meaning that larger plants would be less costly to achieve the same total production rate [8,10]. With that, a production rate of 10 kg/year/kg might be too optimistic especially for smaller plants, even with technological advancement in the future.…”

“…In this study it is assumed that the ISRU system is automated or teleoperated with robots and that both the maintenance requirement and the resource productivity are linearly scalable with respect to the size of the system. While a previous study showed that ISRU plants actually follow economies of scale [8,10], this study takes advantage of LP formulation by assuming linear scalability. Let α and β be the proportional constants for maintenance requirement (ISRU spares) and resource productivity, respectively.…”

“…Various lunar ISRU systems have been proposed such as hydrogen reduction, methane carbothermal reduction, molten electrolysis (electrowinning), volatile extraction, and polar water ice extraction [7][8][9][10][11][12]. ISRU options on Mars include the Sabatier reaction, reverse water gas shift reaction, and atmosphere electrolysis.…”

A Modeling Framework for Applying Discrete Optimization to System Architecture Selection and Application to In-Situ Resource Utilization

“…Oxygen is a consumable resource used to supply crew air and oxidizer in rocket propellant that can be extracted from the lunar regolith. Systems to perform lunar oxygen extraction are being studied and built by NASA, including the development of a system modeling tool that captures the many architecture alternatives in the system selection and design 2,3 . Several chemical processes can be used to produce oxygen from the metal oxides and glasses present in lunar soil, but because there is no historical data to draw from in the design of these systems, a detailed set of engineering models has been constructed to help assess the systemlevel trades of some of these processes.…”

Analysis of Water Surplus at the Lunar Outpost

“…Given the economy of scale analysis previously perform on the ISRU OPS using the ISRU modeling tool reported in Ref. 12, it would be more efficient to have fewer OPS with higher production rates. Hence, the smarter lower risk approach would be to have a series of OPS that progressively increase in capability as the system mature.…”