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Space Station Freedom (SSF) has an extended mission duration of 30 years. Trade studies for extended missions of manned spacecraft almost invariably show that large resupply weight and consequent cost savings can be achieved by recovering potable water from wastewater sources. This rationale has led to the present baseline Water Recovery and Management (WRM) system for the Permanently Manned Capability (PMC) phase of SSF. The baseline WRM includes the Vapor Compression Distillation (VCD) subsystem for recovering water from urine. This process serves as a preliminary processing step in achieving potable water from wastewater sources. The basic principle of the VCD is that water is evaporated from urine and then condensed in a zero-gravity device containing an evaporator and a condenser in a rotating drum. The VCD was selected for the baseline WRM following the assessment of test results from competitive urine processing subsystems obtained from the Comparative Test (CT) program.

Progressive development of Electrochemical Carbon Dioxide (CO2) Concentration (EDC) technology by Life Systems under the sponsorship of the National Aeronautics and Space Administration (NASA) has resulted in subsystem hardware and Control and Monitor Instrumentation (C/M I) that are ideally suited for application to the Space Station program. The development effort has simplified the mechanical assembly to where only seven Orbital Replacement Units (ORUs), including two integrated components, are required to perform the process function. This simplification results in subsystem weight, power and volume requirements that are less than those of competing technologies. Further, process simplification provides both superior reliability and enhanced maintainability. Control and Monitor Instrumentation development has focused on utilization of state-of-the art electronics and software features that enhance subsystem reliability through fault detection and isolation.

The Space Station Environmental Control and Life Support System (ECLSS) consists of 51 functions. These functions are mostly independent of interactions. One exception is the regenerative air revitalization functions of carbon dioxide (CO2) removal, carbon dioxide (CO2) reduction and oxygen (O2) generation. Integration of these interdependent functions and humidity control into a single system provides significant opportunities for process simplification and reductions in power, weight and volume requirements compared to the use of discrete subsystems. An example of the magnitude of the opportunities provided is given by the ARS-1 developed by Life Systems under the sponsorship of National Aeronautics and Space Administration (NASA). Information presented in this paper quantifies the savings achieved by this integration and identifies other advantages available through process integration.