For over 50 years, hydrazine has been the industry standard for monopropellant propulsion systems, widely used in satellite attitude and orbit control systems. However, hydrazine’s toxicity necessitates expensive handling procedures and may lead to a future ban of the propellant in Europe. This has motivated the development of novel monopropellants, featuring reduced toxicity compared to hydrazine. Separately, life cycle assessments (LCAs) are becoming increasingly prevalent in the space industry. As very few assessments have been made so far for monopropellant systems, this thesis performs a comparative life cycle sustainability assessment (LCSA) of a hydrazine and three novel monopropellant systems for a single use case, evaluating the environmental, economic and social sustainability of each. This research provides new insights into the life cycle impact of the differences between the various propulsion systems and identifies hotspots in each sustainability dimension, informing a more sustainable development of novel monopropellant systems in the future.