Membrane Microgravity Air Conditioner Conceptual Design Progress and Long Duration Test Results

Date

2019-07-07

Journal Title

Journal ISSN

Volume Title

Publisher

49th International Conference on Environmental Systems

Abstract

The Membrane Microgravity Air Conditioner (MMAC) is a microgravity compatible condensing heat exchanger for removal of particulates, humidity, and heat from air, with production of clean condensate, leading to possible applications for Exploration Vehicles as a potential alternative to the current state of the art condensing heat exchangers and centrifugal water separators utilized on the International Space Station (ISS). The MMAC condenses water onto a cold nanoporous-hydrophilic-membrane where the condensate is drawn through the membrane by a negative air-to-water pressure differential into a cold water loop and delivered to a water purification system. A subscale MMAC was designed and tested, and the results were used to develop an ISS Technology Demonstration MMAC Concept and an Exploration MMAC Concept. These concepts addressed volume, mass, power, interfaces, operation and control, maintenance, specifications, redundancy, and reliability. Testing evaluated condensate production rates and the effects of hydrogen peroxide as a biocide under a variety of conditions for six months of continuous testing. The outside of the subscale MMAC condensing membrane was inoculated weekly with three specific skin and environmental microbes as well as a fungus, but they were not observed within the condensate loop fluid during weekly testing. Testing demonstrated the robustness of the MMAC after it experienced two inadvertent shutdowns which resulted in growth of existing condensate loop microbes which did not change the condensation production rate. It was concluded that the weekly hydrogen peroxide protocol was not an effective means of microbial control within the condensate loop as persisting strains of bacterium and fungus developed a resistance to hydrogen peroxide over the six month test. The test hardware and resulting data did not reveal any concerns with proceeding to an ISS Technology Demonstration MMAC. Additional short and long duration MMAC testing with siloxanes at Johnson Space Center is also reported.

Description

John Fricker, Oceaneering Space Systems, USA
Roger Lottridge, Oceaneering Space Systems, USA
Scott Hansen, National Aeronautics and Space Administration (NASA), Johnson Space Center, USA
ICES103: Thermal and Environmental Control of Exploration Vehicles and Habitats
The 49th International Conference on Environmental Systems was held in Boston, Massachusetts, USA on 07 July 2019 through 11 July 2019.

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Keywords

condensing heat exchanger, thermal control, membrane, biocide, siloxane

Citation