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Microbial Characterization of Internal Active Thermal Control System (IATCS) Hardware Surfaces after Five Years of Operation in the International Space StationA flex hose assembly containing aqueous coolant from the International Space Station (ISS) Internal Active Thermal Control System (IATCS) consisting of a 2 foot section of Teflon hose and quick disconnects (QDs) and a Special Performance Checkout Unit (SPCU) heat exchanger containing separate channels of IATCS coolant and iodinated water used to cool spacesuits and Extravehicular Mobility Units (EMUS) were returned for destructive analyses on Shuttle return to flight mission STS-114. The original aqueous IATCS coolant used in Node 1, the Laboratory Module, and the Airlock consisted of water, borate (pH buffer), phosphate (corrosion control), and silver sulfate (microbiological control) at a pH of 9.5 +/- 0.5. Chemical changes occurred after on-orbit implementation including a decrease to pH 8.4 due to the diffusion of carbon dioxide through the Teflon hoses, an increase in nickel ions due to general corrosion of heat exchanger braze coatings, a decrease in phosphate concentration due to precipitation of nickel phosphate, and the rapid disappearance of silver ions due to deposition on hardware surfaces. Also associated with the coolant chemistry changes was an increase in planktonic microorganisms from less than 100 colony forming units (CFU) per 100 ml to approximately 1 million CFU per 100 ml. Attachment and growth of microorganisms to the system surfaces (biofilm) was suspected due to the levels of planktonic microorganisms in the coolant. Biofilms can reduce coolant flow, reduce heat transfer, amplify degradation of system materials initiated by chemical corrosion, and enhance mineral scale formation.
Document ID
20060047778
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Roman, Monsi C. (NASA Marshall Space Flight Center Huntsville, AL, United States)
Weir, Natalee E. (Boeing Co. United States)
Wilson, Mark E. (Boeing Co. United States)
Pyle, Barry H. (Montana State Univ. MT, United States)
Date Acquired
September 7, 2013
Publication Date
January 1, 2006
Subject Category
Exobiology
Report/Patent Number
Paper-2006-01-2157
Meeting Information
Meeting: 36th International Conference on Environmental Systems
Location: Norfolk, VA
Country: United States
Start Date: July 16, 2006
End Date: July 20, 2006
Funding Number(s)
CONTRACT_GRANT: NAS15-10000
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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