Estimating the scale of Space Resource Utilisation (SRU) operations to satisfy lunar oxygen demand

Abstract

The production of oxygen from lunar regolith is analogous to metal production from ore in a terrestrial mine. The process flowsheets both include excavation, haulage and beneficiation of the regolith or ore to provide the feedstock for the chemical extraction of oxygen or metal. The production rate of oxygen depends on the mass rate of regolith treated and the efficiency of converting the regolith to oxygen. To date, the development of Space Resource Utilisation (SRU) has been concerned with the technological development of the process, particularly the excavation and oxygen extraction. However, the required operating mass rates of the mine operation and the oxygen extraction stage have not been considered in any great detail. Previous estimates of mining scale for lunar oxygen production are reviewed, and converted to a comparable regolith mining rate of kg/h. Beneficiation of the regolith before oxygen extraction is considered, and the effects of pre-sizing and removal of a specific component, agglutinates, are considered. The oxygen yield and operational availability are also included. It is estimated that the minimum mining rate to produce 1000 kg of oxygen per annum is at least five times higher than previous estimates, 30 kg/h, for equivalent efficiency assumptions. Monte-Carlo simulations were performed for statistical confidence in the estimates of the mining mass rate and the required oxygen extraction feedstock rate. To be 95% confident that the 1000 kg/y O2 will be met, the designed mining rate should be at least 65 kg/h, and the beneficiated feedstock rate 16 kg/h. This study has revised and increased the estimate of the lunar regolith mining scale required for the production of a given amount of oxygen. It has also estimated the mass rate of feedstock required for oxygen extraction, if the regolith is first beneficiated. The findings have a significant impact on the practical implementation of lunar mining and oxygen extraction, particularly the process design and whether the operation will be by batch- or continuous processing. The mass scale and beneficiation approaches bring terrestrial mining and processing concepts to SRU, and for the first time estimates the effect that regolith beneficiation and uncertainty have on the estimated scale of both the mining and extraction operations.