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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.