Design considerations for sustainable spacecraft water management systems

It is well recognized that water handling systems used in a spacecraft are prone to failure caused by biofouling and mineral scaling, which can clog mechanical systems and degrade the performance of capillary-based technologies. Long duration spaceflight applications, such as extended stays at a Lunar Outpost or during a Mars transit mission, will increasingly benefit from hardware that is generally more robust and operationally sustainable over time.This paper presents design strategies and testing considerations for improving the reliability of water handling technologies. Our application of interest is to devise a spacecraft wastewater management system wherein fouling can be accommodated by design attributes of the management hardware, rather than implementing some means of preventing its occurrence. Two representative boundary applications are presented. The first is a short term application where reduced gravity flight tests demonstrated a static phase separator prototype that achieved nearly 100% separation of gas from liquids under widely varying wetting conditions correlated to anticipated ranges of wastewater fouling. The second is a design concept for a lunar outpost water recovery system where wastewater is allowed to age and form biofilms and precipitates that can be filtered through lunar regolith media as the water is reclaimed. Both applications are supported by similar underlying principles of facilitating sustainable fluid handling in the presence of fouled surfaces.