In-Orbit Reusable Kick-Stage Enabled by a Sustainable Space Mobility Solution Harvesting Solar Energy for Onboard Fuel Production

Abstract

The EU-EIC Pathfinder project Green SWaP (Green Solar-to-Propellant Water Propulsion) develops a sustainable in-space mobility architecture that directly converts water into hydrogen (H₂) and hydrogen peroxide (H₂O₂) using solar energy. This approach enables a reusable propulsion system combining a 200 N chemical thruster for primary manoeuvres with 1 N solar-thermal thrusters (Isp ∼500 s) for attitude control. By harvesting energy in orbit and producing propellant onboard, the system enhances operational safety, supports water circularity in space, and reduces dependence on Earth-supplied resources. Such a capability extends spacecraft lifetime, enables in-orbit refueling and in-situ resource utilization (ISRU), and broadens the feasibility of reusable orbital stages. To evaluate this potential, a dedicated mission analysis was performed after a selection process, focusing on a reusable kick-stage concept as a case study. The results provide preliminary sizing of key enabling technologies, such as bi-modal propulsion, inflatable hydrogen storage, and solar-to-fuel conversion, and demonstrate the transformative impact of Green SWaP on sustainable space logistics and future mission architectures.