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Developing advanced technology through the prototype phase on a system as complex as a Portable Life Support Subsystem (PLSS) for an Extravehicular Mobility Unit (EMU) is a time and resource consuming process. Experience has shown that most of the decisions controlling the life cycle cost of a system intended for operational use are made very early in the design process. By the preliminary design review most of the design-controlled cost drivers are locked into the design. To ensure a reasonable chance for the design to successfully meet mission requirements, it is best to choose the most promising, most likely-to-succeed technology available in the early stages of breadboard and preprototype development.

The device described in this paper is a flat sheet membrane module that removes humidity from the space suit breathing loop by venting it to the vacuum of space. The module consists of alternating vacuum layer assemblies and vent layer assemblies separated by solid polymer membrane sheets. The module is designed to optimize volume and pressure drop at a given vent flow rate and water removal rate. Both Hamilton Standard and the NASA Johnson Space Center tested the module under varying EMU flow and humidity conditions; the results of the testing are presented in the paper. The module met or exceeded all of the design goals set forth in the program statement of work, including volume, pressure drop and water removal rate.