Towards a water-based space economy

Spacecraft life-extension capabilities have already and will continue to reshape space missions and their operations. New spacecraft capable of autonomous servicing and operations are prompting a rethink of spacecraft propulsion system requirements. With increased emphasis on propellant availability, low toxicity, and compatibility with refilling technologies, conventional propulsion systems may no longer offer an optimal solution. In the context of the Ice2Thrust project, this paper presents Water Electrolysis Propulsion (WEP) as a promising alternative, leveraging water’s storability and low toxicity to form the basis of a self-sustaining mobility architecture. By enabling space-based propellant production and distribution, WEP can facilitate the creation of a circular space economy centered around water.

To meet demand for increased performance and operational lifespan, mission flexibility, and to address pressing debris mitigation requirements, a propulsion system capable of hosting electric as well as hot and cold-gas thrusters is proposed. For the hot-gas thruster, a specific impulse of >370s is targeted as an immediate and clear benefit over contemporary chemical thrusters. By combining the functionality of a fill and drain valve with a docking port, mass is minimized to facilitate integration down to a CubeSat level, while ensuring a low barrier to entry for system integrators. A trade-off study is performed to quantify performance compared to conventional systems.

Water propellant production, including harvesting and purification, forms the foundation of a selfsustaining mobility architecture. In the frame of Ice2Thrust, the focus is on lunar water owing to the relatively high abundance of water on the Moon’s poles. Thermal ice mining is chosen as the harvesting method to minimize infrastructure and power requirements. The economic viability of Moon-based propellant distribution is assessed for a range of supply architecture concepts, with the possibility of supporting both commercial missions and human spaceflight. The present work demonstrates that WEP combined with thermal ice mining has the potential to become the first example of in-situ mined and processed propellants.

Industry trends indicate that successfully fostering an in-orbit servicing economy in a risk-averse industry must begin with offering an immediate value proposition to satellite integrators while simultaneously advancing servicing technologies. To this end, a comprehensive overview is presented of technical, commercial, and logistical considerations of not only enabling a WEP-based space economy but ensuring its long-term viability.