EMU Ventilation Loop Simulation and Assessment of Contamination of the EMU Sublimator Hydrophilic Coating

Date

2023-07-16

Journal Title

Journal ISSN

Volume Title

Publisher

2023 International Conference on Environmental Systems

Abstract

Controlling moisture is a critical function performed in the spacesuit during extra vehicular activity (EVA) missions. Currently, this function is carried out by a sublimator, which is coated with a hydrophilic material. Tests have shown that siloxane compounds can off-gas from the helmet absorption pad extender (HAP-E) and helmet absorption band (HAB) when they are at elevated temperatures, and initial testing indicated that siloxanes could damage the hydrophilic coating. Therefore, more representative testing was needed. Important test considerations were source and destination kinetics, system geometries, scrubbing efficacy by the activated charcoal from the MetOx canister, and other benefits that derive from active condensation occurring on the hydrophilic coating during exposure. A ventilation loop, which was originally constructed to test hardware for control of CO2 and trace contaminants under EVA conditions, was modified to conduct the siloxane off-gassing tests. A vacuum compatible acrylic chamber was installed to simulate the suit volume. A steel beaker located in the chamber contained the HAP-E and HAB materials and was heated with two band heaters. The flow exiting the chamber passed through a LiOH cannister, which contained carbon beds to simulate their function in the MetOx. The flow then was directed into a smaller volume that contained a coupon, which was coated with the hydrophilic material and was maintained at 50°F. Moisture was injected upstream of the suit volume simulator to maintain the dew point between 55°F and 65°F. The pressure was controlled to between 3.8 and 4.4 psia, and the flow was held at 6 acfm. The system was run for an equivalent of 25 10 h EVAs, where the HAP-E/HAB materials were changed out after each EVA. The effect of the potential off-gassing on the coupon was measured after each EVA period.

Description

Alex Wickham, Reaction Systems, Inc., USA
David Wickham, Reaction Systems, Inc., USA
Colin Campbell, NASA Johnson Space Center(JSC), USA
Michael Humbert, Collins Aerospace, USA
ICES408: ISS US EVA-80 Water Helmet Incident Investigation
The 52nd International Conference on Environmental Systems was held in Calgary, Canada, on 16 July 2023 through 20 July 2023.
ICES408: ISS US EVA-80 Water Helmet Incident Investigation
The 52nd International Conference on Environmental Systems was held in Calgary, Canada, on 16 July 2023 through 20 July 2023.

Keywords

space suit, siloxane, sublimator, hydrophilic, moisture, EVA

Citation