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
This Brief includes a Technical Support Package (TSP).
Adaptation of a Filter Assembly to Assess Microbial Bioburden of Pressurant Within a Propulsion System
(reference NPO-48304) is currently available for download from the TSP library.
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Overview
The document titled "Adaptation of a Filter Assembly to Assess Microbial Bioburden of Pressurant Within a Propulsion System" (NPO-48304) is a technical support package from NASA's Jet Propulsion Laboratory (JPL). It outlines a method for evaluating microbial contamination in pressurants used in propulsion systems, which is critical for ensuring the reliability and safety of spacecraft.
The primary focus of the document is the adaptation of a Millipore filter assembly, which employs a sterile filter with a pore size of 0.22 mm. This assembly is designed to capture microbial contaminants from helium, a common pressurant in aerospace applications. The process involves collecting helium at a controlled rate of 100 standard cubic feet per hour (SCFH) and extracting samples aseptically into sterile Corning bottles.
The methodology includes several key steps:
- Sonication: The collected samples undergo a 2-minute sonication process to dislodge microorganisms from the filter.
- Heat Shock: Following sonication, the samples are subjected to a heat shock treatment at 80°C for 15 minutes, as per NASA HDBK 6022 guidelines. This step is intended to enhance the recovery of viable microorganisms.
- Plating and Incubation: An aliquot of the sample (18 mL) is plated and incubated to allow for microbial growth, with counts taken at 24, 48, and 72 hours to assess bioburden levels.
- Rinsing and Vortexing: A rinse solution (20 mL of PP rinse solution) is added to the filters, which are then vortexed for 15 seconds to ensure thorough mixing and recovery of any remaining microorganisms.
The document emphasizes the importance of monitoring microbial bioburden in propulsion systems, as contamination can lead to system failures or compromised mission integrity. The described method serves as a proof-of-concept for assessing microbial presence in pressurants, contributing to the broader goal of maintaining clean and reliable spacecraft systems.
Overall, this technical support package not only details the experimental setup and procedures but also highlights the significance of microbial assessment in aerospace technology, showcasing NASA's commitment to innovation and safety in space exploration. For further inquiries or assistance, the document provides contact information for the Innovative Technology Assets Management at JPL.
