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NASA is investigating the use of plant growth chambers (PGCs) for space missions and for bases on the moon and Mars. Key to successful development of PGCs is a system to recover and reuse the water vapor that is transpired from the leaves of the plants. In this paper a design is presented for a simple, reliable, membrane-based system that allows the recovery, purification, and reuse of the transpired water vapor through control of temperature and humidity levels in PGCs. The system is based on two membrane technologies: 1) dehumidification membrane modules to remove water vapor from the air, and 2) membrane contactors to return water vapor to the PGC (and, in doing so, to control the humidity and temperature within the PGC). The membrane-based system promises to provide an ideal, stable growth environment for a variety of plants, through a design that minimizes energy usage, volume, and mass, while maximizing simplicity and reliability.

For long-duration space missions, the mass of the initial stock of supplies (e.g., food, water, air, spare parts) must be limited and the number of items that require resupply during the mission must be minimized. Given these constraints, regenerative environmental control and life support systems (ECLSS) are a necessity. Membrane processes are ideal for regenerable ECLSS because membrane processes 1) operate reliably for long periods, 2) are simple to repair and maintain, and 3) do not require consumable or expendable materials. In this paper, the uses of membranes in a regenerable ECLSS are reviewed. System designs and experimental data are presented on the use of membranes for the purification and recycling of water (e.g., the treatment of hygiene water, urine, humidity condensate and phase-change distillate) and for the treatment and purification of air (e.g., removal of water vapor and carbon dioxide).

The development of a temperature and humidity control system that can remove heat and recover water vapor is key to the development of an Environmental Control and Life Support System (ECLSS). Large quantities of water vapor must be removed from air, and this operation has proven difficult in the absence of gravity. This paper presents the modeling results from a program to develop a novel membrane-based heat exchanger known as the condensate recovery heat exchanger (CRX). This device cools and dehumidifies humid air and simultaneously recovers water-vapor condensate. In this paper, the CRX is described and the results of an analysis of the heat- and mass-transfer characteristics of the device are given.

This paper describes the continued development of a non-phase-change waste-water subsystem for use in the planned manned space station. Comparisons of various membrane-based technologies when operated side by side on feed solutions of synthetic wash water are presented. The effects of soap type and operating temperature on membrane-module performance were determined. A preliminary ranking of these modules indicated that several of the reverse-osmosis and ultrafiltration technologies are excellent candidates for use in the subsystem. At this time, a hybrid system configuration consisting of a first-stage ultrafiltration module followed by a second-stage reverse-osmosis module appears to be the most appropriate for use in the subsystem.