Technology Roadmapping of an ISRU System for NASA Using a Medium-Fidelity System Dynamics Simulation

Abstract

With the Artemis Program, NASA and its international and commercial partners are targeting not only a return to the Moon but also the development of technologies that would support a long-term sustainable presence. Technology development for In-Situ Resource Utilization (ISRU) of lunar water is currently in progress, with commercial actors proposing or developing alternative, competing architectures. From the point of view of NASA, as a central stakeholder in long-term roadmapping and development of space technologies, it is desirable to evaluate these competing ISRU architectures not only according to their stated or validated system-level performance and best available cost estimates, but also according to an objective assessment of their long-term potential for future performance improvement in the context of ongoing technology development. Therefore, investigations of the improvement potential of subsystems, in terms of Figures of Merit at the subsystem level, would be supportive of efforts to quantify the long-term improvement potential of alternative, competing architectures. Accordingly, we present a medium-fidelity dynamic simulation of a lunar water ISRU architecture for the purpose of quantifying potential system-level benefits of investing in the incremental improvement of subsystem performance. We used the System Dynamics framework to create a detailed technology performance model of Rocket-M, a proposed technology to produce water from ice-bearing regolith using a rocket engine to excavate to depths of 2-3 meters. The model handles feedbacks between stocks and the flows that influence their levels and can account for the levels of critical stocks over time, such as battery charge level, quantity of propellant remaining and quantity of water produced. Thus, the approach lends itself to the discovery of subtle feedbacks in complex systems which feature multiple interactions between components. Using a validated version of this model, it is possible to assess the sensitivity of the key system-level figures of merit to changes in the figures of merit of subsystems and accompanying systems. This modeling methodology also supports the exploration of alternative technology roadmapping and development questions, such as obtaining estimates of the net productivity and net specific efficiency of Rocket-M, which can then be compared like-with-like vs. different water ISRU architectures. It can also be used for the identification of the underlying technologies with high sensitivity to the system-level outcome and their potential prioritization for flight demonstration testing so as to predict their expected performance with more certainty. This work helps inform technology investment decisions.