Upgrades to the International Space Station Urine Processor Assembly

Since November 2008, the ISS Urine Processor Assembly (UPA) has successfully generated distillate from crew urine. Several rounds of modifications and upgrades have also been implemented to improve overall system performance throughout the years. The Distillation Assembly (DA) is the latest upgraded unit available, installed in September 2020. This unit has shown immediate performance improvements and redesign success. Most significant upgrades have been a redesigned drive train to eliminate belt slips, improved sealing to reduce leak paths and improve wear, and a redesigned liquid level sensor. The Purge Pump and Separator Assembly (PPSA) technology demonstration is the next available upgraded unit and has finished ground assembly and testing and is targeted for ISS delivery within the coming year. Most recent ground studies have identified areas to focus future UPA upgrade considerations with exploration missions in mind, specifically for better fault detection and isolations approaches as well as potential hardware redesigns to facilitate successful dormancy operations.