From Water and Sunlight to Thrust: New Propulsion Technologies Within the Green SWaP Project

In recent years, interest in developing propulsion technologies based on water as principal propellant has grown exponentially. Water is not only straightforward to manage and stored both on Earth and in space, but it is also abundantly available on numerous celestial bodies within the Solar System, including the Moon. This availability opens game-changing possibilities in the field of In Situ Resource Utilisation (ISRU). Furthermore, water allows for unique synergies with in-space human outposts by means of shared liquid storage and recycling processes. These aspects can significantly enhance the sustainability and feasibility of future space exploration. The Green SWaP project, an EU-EIC Pathfinder initiative, aims to develop the core technologies for future water-based propulsion systems by adopting an innovative approach distinct from previous efforts. The acronym stands for Green Solar-toPropellant Water Propulsion, reflecting the project’s primary objective: the development and validation of technologies that utilize solar energy to co-generate a new combination of propellants from water: hydrogen peroxide (H2O2) and hydrogen (H2). These propellants serve as starting point to enable the development of two pioneering propulsion technologies. The first is a high-thrust bipropellant engine that utilises concentrated liquid hydrogen peroxide (High Test Peroxide, typical oxidizer for space propulsion applications) and gaseous hydrogen, providing a powerful and efficient main propulsion method. The second is a low-thrust solar thermal propulsion system that employs gaseous hydrogen, offering a sustainable and efficient alternative for long-duration space missions or fine-tuning manoeuvres.