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Selection of an Alternate Biocide for the ISS Internal Thermal Control System Coolant, Phase 2The ISS (International Space Station) ITCS (Internal Thermal Control System) includes two internal coolant loops that utilize an aqueous based coolant for heat transfer. A silver salt biocide had previously been utilized as an additive in the coolant formulation to control the growth and proliferation of microorganisms within the coolant loops. Ground-based and in-flight testing demonstrated that the silver salt was rapidly depleted, and did not act as an effective long-term biocide. Efforts to select an optimal alternate biocide for the ITCS coolant application have been underway and are now in the final stages. An extensive evaluation of biocides was conducted to down-select to several candidates for test trials and was reported on previously. Criteria for that down-select included: the need for safe, non-intrusive implementation and operation in a functioning system; the ability to control existing planktonic and biofilm residing microorganisms; a negligible impact on system-wetted materials of construction; and a negligible reactivity with existing coolant additives. Candidate testing to provide data for the selection of an optimal alternate biocide is now in the final stages. That testing has included rapid biocide effectiveness screening using Biolog MT2 plates to determine minimum inhibitory concentration (amount that will inhibit visible growth of microorganisms), time kill studies to determine the exposure time required to completely eliminate organism growth, materials compatibility exposure evaluations, coolant compatibility studies, and bench-top simulated coolant testing. This paper reports the current status of the effort to select an alternate biocide for the ISS ITCS coolant. The results of various test results to select the optimal candidate are presented.
Document ID
Document Type
Conference Paper
Wilson, Mark E. (Boeing Co. Houston, TX, United States)
Cole, Harold (Boeing Co. Houston, TX, United States)
Weir, Natalee (Boeing Co. Houston, TX, United States)
Oehler, Bill (Hamilton Standard Space Systems International United States)
Steele, John (Hamilton Standard Space Systems International United States)
Varsik, Jerry (Hamilton Standard Space Systems International United States)
Lukens, Clark (Honeywell International, Inc. United States)
Date Acquired
August 23, 2013
Publication Date
March 30, 2004
Subject Category
Life Sciences (General)
Report/Patent Number
Meeting Information
2004 International Conference on Environmental Systems(Colorado Springs, CO)
Funding Number(s)
Distribution Limits