<div class="htmlview paragraph">The International Space Station (ISS) has served as an excellent test bed for the implementation and integration of several life support systems, and has offered many lessons that can be applied to future vehicles and program. This paper focuses on those lessons learned within the Environmental Control and Life Support (ECLS) Water Subsystem, which have dictated on-orbit system performance and forced many operational controls. These include lessons on the need for precise documentation and testing, pros and cons of different types of storage containers, and the need for designing systems to have accessibility and flexibility. This paper describes the issues encountered on ISS and suggests solutions for future systems in the form of recommendations and questions posed to the future designers.</div>

<div class="section abstract"><div class="htmlview paragraph">The United States Propulsion Module (USPM) is a pressurized element and provides reboost, propulsive attitude control, control moment gyro (CMG) desaturation, and collision avoidance functions for the International Space Station (ISS). The USPM will dock with Node 2 at the pressurized mating adapter-2 (PMA-2). After docking with PMA-2, the USPM will provide mechanical and structural interfaces to the Space Shuttle, along with facilities for crew transfer and receiving resupply oxygen, nitrogen, water, helium, and propellants from the Space Shuttle. It is essential that the USPM maintain a safe and functional life support system during crew member passage and maintenance activities. It is complex and costly to design an operational system to satisfy all ISS requirements. This paper details an innovative USPM environmental control and life support system (ECLSS) design that satisfies all ISS requirements at a reduced cost.</div></div>

The potable water dispenser (PWD) system plays a critical role as a source of drinking water for astronauts on the International Space Station (ISS). In this study, we examined the bioburden in the potable water produced by the PWD. The amount of extracellular polymeric substances (EPSs) in the PWD water was approximately 19 or 55 times greater than the bacterial count, and the EPS biomass accounted for approximately 24% or 86% of the bacterial biomass. <i>Ralstonia pickettii</i> consistently comprised approximately 70% or 80% of the bacteria for 3 years. Under simulated microgravity conditions, the isolated <i>R. pickettii</i> strains exhibited higher cell and EPS concentrations and higher total volume concentrations (average volume multiplied by concentration) of cell and EPS than under 1G conditions, whereas the average cell volume was smaller and the average EPS volume was larger. The ISS isolates showed higher EPS production and biofilm-formation abilities than terrestrial strains under nutrient-rich conditions and possessed high biofilm-formation ability comparable to those of terrestrial strains under nutrient-poor conditions. The ability of <i>R. pickettii</i> to produce EPS may play a crucial role in its adaptation to the water environment on the ISS.IMPORTANCEIn space habitation environments, the use of recycled water is indispensable, and ensuring its microbiological safety is essential. In this study, we elucidated the microbiological characteristics of water from the potable water dispenser (PWD) on the International Space Station (ISS). Our findings revealed that bacteria of the <i>Ralstonia pickettii</i> are the predominant species in PWD water and that extracellular polymeric substances (EPSs) constitute a large proportion of the biomass. Furthermore, the isolated <i>R. pickettii</i> was shown to possess high EPS production ability and strong biofilm-forming capacity. Since EPS plays a crucial role in biofilm formation, these abilities may be important factors enabling <i>R. pickettii</i> to adapt to the water environment of the ISS.