A report describes an adaptation of a filter assembly to enable it to be used to filter out microorganisms from a propulsion system. The filter assembly has previously been used for particulates >2 μm. Projects that utilize large volumes of nonmetallic materials of planetary protection concern pose a challenge to their bioburden budget, as a conservative specification value of 30 spores/cm3 is typically used.

Helium was collected utilizing an adapted filtration approach employing an existing Millipore filter assembly apparatus used by the propulsion team for particulate analysis. The filter holder on the assembly has a 47-mm diameter, and typically a 1.2-5 μm pore-size filter is used for particulate analysis making it compatible with commercially available sterilization filters (0.22 μm) that are necessary for biological sampling.

This adaptation to an existing technology provides a proof-of-concept and a demonstration of successful use in a ground equipment system. This adaptation has demonstrated that the Millipore filter assembly can be utilized to filter out microorganisms from a propulsion system, whereas in previous uses the filter assembly was utilized for particulates >2 μm.

This work was done by James N. Benardini, Robert C. Koukol, Wayne W. Schubert, Fabian Morales, and Marlin F. Klatte of Caltech for NASA’s Jet Propulsion Laboratory. NPO-48304

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Adaptation of a Filter Assembly to Assess Microbial Bioburden of Pressurant Within a Propulsion System

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This article first appeared in the September, 2012 issue of NASA Tech Briefs Magazine.

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