Environmental limits to the space sector's growth

Space activities are now expanding at a fast pace and various ambitious projects have been proposed for the future, raising the question of their environmental sustainability. While the space debris situation has been widely recognized as a serious threat to space sustainability, other pressing environmental issues have received little attention yet, although they pose risks to the environment and actors of the space sector. Therefore, this paper first reviews the major environmental impacts of space activities and their potential growth, analyzed together in a comprehensive approach for the first time. The degradation of the orbital environment with space debris has already reached a threshold leading to a future increase of the number of objects even without additional launches, while the contribution of artificial space objects to night sky brightness may have already crossed the light pollution threshold defined by astronomers. Planned large constellations will likely deteriorate the situation significantly. In this context, the formulation of these thresholds within the planetary boundaries framework is proposed to support awareness-raising and policy-making. Furthermore, stratospheric ozone depletion and climate change resulting from rocket emissions could reach levels triggering regulatory responses in the next decades due to the coming surge in launch rates. This could also apply to particles from thousands of constellations' satellites burning while reentering Earth's atmosphere, although the magnitude of their effects is yet unknown. A common assumption is that limitations to the human enterprise in space are of a purely technical and economic nature. This paper challenges this assumption, by highlighting the existence of environmental limits to the currently planned development of space activities. Risks arising from these limits are explored, and the importance of ecodesign in the space sector is emphasized. Finally, the paper discusses the future sustainability of proposed space projects in the context of global ecological transition.