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Process Development for Removal of Siloxanes from ISS AtmosphereDimethylsilanediol (DMSD) has been identified as a problematic organic contaminant aboard the ISS. This contaminant was initially identified in humidity condensate and in the Water Processor Assembly (WPA) product water in 2010 when routine water quality monitoring an increasing total organic carbon (TOC) trend in the WPA product water. Although DMSD is not a crew health hazard at the levels observed in the product water, it can degrade the WPA catalytic reactor's effectiveness and cause early replacement of Multifiltration Beds. DMSD may also degrade the performance of the Oxygen Generation System (OGS) which uses the WPA product water for electrolysis. An investigation into the source of DMSD has determined that polydimethylsiloxane (PDMS) compounds are likely hydrolyzing in the Condensing Heat Exchangers (CHX) to form DMSD. PDMS compounds are prevalent aboard ISS from a variety of sources, including crew hygiene products, adhesives, caulks, lubricants, and various nonmetallic materials. PDMS compounds are also known to contribute to CHX hydrophilic coating degradation by rendering it hydrophobic and therefore adversely affecting its ability to effectively transmit water to the condensate bus. Eventually this loss in performance results in water droplets in the air flow exiting the CHX, which may lead to microbial growth in the air ducts and may impact the performance of downstream systems. Several options have been evaluated to address these concerns. Modifications to the Water Processor Multifiltration Beds and Catalytic Reactor for removal of DMSD were not considered viable, and did not address the issue with PDMS compound degradation of the CHX coating. Design concepts are now in development for removing PDMS compounds from the air stream before they can reach the CHX coating, thus preventing coating degradation and hydrolysis of the PDMS compounds to DMSD. This paper summarizes the current status of the effort to treat these contaminants on ISS.
Document ID
20150019534
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Carter, Layne
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Perry, Jay
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Kayatin, Matthew J.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Wilson, Mark
(Boeing Co. Houston, TX, United States)
Gentry, Gregory J.
(Boeing Co. Houston, TX, United States)
Bowman, Elizabeth
(Boeing Research and Technology Huntsville, AL, United States)
Monje, Oscar
(NASA Kennedy Space Center Cocoa Beach, FL, United States)
Rector, Tony
(United Technologies Corp. Windsor Locks, CT, United States)
Steele, John
(United Technologies Corp. Windsor Locks, CT, United States)
Date Acquired
October 20, 2015
Publication Date
July 12, 2015
Subject Category
Man/System Technology And Life Support
Report/Patent Number
ICES-2015-074
M15-4838
Meeting Information
Meeting: International Conference on Environmental Systems Conference
Location: Bellevue, WA
Country: United States
Start Date: July 12, 2015
End Date: July 16, 2015
Distribution Limits
Public
Copyright
Public Use Permitted.
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