Filtration and measurement of aerosol for the In situ resource utilisation of planetary atmospheres

Abstract

In Situ Resource Utilisation (ISRU) has the potential to dramatically reduce the mass and cost of planetary science and exploration missions. The Mars Oxygen ISRU Experiment (MOXIE) on the Mars 2020 rover will demonstrate ISRU on Mars by producing oxygen from atmospheric carbon dioxide. Mars’ dust aerosol presents a risk to MOXIE and any future full-scale atmospheric ISRU plant. To mitigate this risk, MOXIE will filter the atmosphere of another planet for the first time. Although filtration of Earth’s atmosphere is well understood, filtration of Mars’ atmosphere is not. Additionally, the most important property of the aerosol for filtration, its particle size distribution, is not well constrained. This thesis addresses these problems by determining the dust loading rate and resulting pressure drop of the MOXIE filter by analysis, numerical simulation, and experimental investigation in simulated Mars conditions. The effects of suspended dust, saltated particles, dust devils and local, regional and global dust storms are considered. Atmospheric ISRU offers a high, continuous, and known flow rate, which an integrated science instrument to measure the aerosol particle size distribution could benefit from. Existing instrumentation is surveyed, and the feasibility of cascade impaction and inertial focusing is investigated. Cascade impaction offers a low mass, passive method of particle size measurement. Work on this thesis was carried out alongside operational support of the InSight mission, the unprecedented continuous horizontal wind speed measurements of which were used to observe saltation on the surface of Mars. Additionally, it is demonstrated that InSight’s Short Period (SP) seismometers have the capability of detecting micrometeoroid impacts during cruise.