Green SWaP will prove and validate a technology that will use solar energy to produce propellants (H2O2/H2) from water for in-space green propulsion. It will be a crucial building block to enable innovative green propulsion solutions for in-space mobility, resulting in low-cost and eco-friendly innovative concepts. It is a novel approach, never developed for in-space mobility (thus beyond SoA). Studies exist for on-earth chemical applications, but many of the constraints are specific to terrestrial applications and do not apply to in-space systems (thus ambitious). The new technologies, based on innovative chemical processes, will harvest solar power to enable green propulsion. It is a plausible methodology because underlying technological concepts of producing/concentrating/storing H2O2/H2 using solar energy have been proven (separately) even though for different constraints and conditions of use than in-space applications. H2O2/H2 as propellants for in-space applications is known but must has never been investigated in detail and the utilization of H2 for solar thermal propulsion is theoretically proven to be the most promising but it has never been developed as technology. The combination of these technologies will drastically increase future spacecrafts’ capabilities, facilitating renewable and self-sustainable in-space mobility. Optimisation concerning the quality and quantity of  H2O2/H2 produced onboard and an efficiency improvement will be fully explored.