Environmental sustainability of future proposed space activities

Miraux, Loïs and Wilson, Andrew Ross and Dominguez Calabuig, Guillermo J. (2022) Environmental sustainability of future proposed space activities. Acta Astronautica, 200. pp. 329-346. ISSN 0094-5765 (https://doi.org/10.1016/j.actaastro.2022.07.034)

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As actors in the space sector are proposing ever more ambitious plans for the future, it is important to evaluate their consequences on the Earth's environment, which are yet poorly known. To address this gap, this study presents a streamlined Life Cycle Assessment of future space activities over the period from 2022 to 2050 based on plans that would likely drive the environmental impacts of the space sector if they were realised. Large constellations of satellites, space tourism, Moon missions, and space-based solar power were considered in a first scenario, while rocket-based point-to-point travel on Earth and Mars colonisation were also included in two other scenarios. To this aim, the model is based on data from companies' declarations and actual space systems and uses life cycle inventory and impact assessment data from the Strathclyde Space Systems Database. In the first scenario, the study finds that by 2050 proposed plans would lead to an unprecedented surge in the impacts of the space sector (×9 on climate change) and in the number of satellites in orbit (∼112,000, all from large constellations). Ozone depletion from launch events could reach significant levels (6% of annual global impacts), while in a decade emissions of black carbon and aluminium oxide from rockets may alter the radiative balance of the atmosphere as much as present-day global aviation, although these effects are uncertain and poorly understood yet. Moreover, the mass injected into the atmosphere by re-entering artificial objects would become significant (∼27× the natural level for aluminium), while its environmental consequences remain largely unquantified. In the two other scenarios, results indicate that speculative plans of rocket-based point-to-point travel on Earth and Mars colonisation could deplete ozone several times as much as all other human activities combined, while air acidification and climate change could reach several percent of annual global impacts and planetary boundaries. The mitigation of these impacts using low carbon fuels would be limited by supply availability and by the emission of non-CO2 climate forcers and ozone-destroying compounds during launch and re-entry. Consequently, environmental sustainability is identified as a potential limiting factor to the development of intense space activities and to making humanity a multi-planetary species. Furthermore, political and social acceptability could play a major role in the development of recreational space travel since it exacerbates environmental inequalities due to an unparalleled combination of economic inaccessibility and high environmental footprints per passenger. Overall, results strongly suggest that there is a pressing need to include environmental considerations in addition to technical and economic analyses in space projects definition and space systems design.