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Abstract:
HEPA-filtered purge air supplied by an environmental control system (ECS) is used to protect encapsulated spacecraft from particulate contamination. Therefore, it is imperative to acquire representative air samples from the ECS ducts in order to ensure that the air cleanliness requirements per mission specifications are achieved. Based on well-established work involving particle transport in the literature, this report quantitatively examines the particle sampling efficiency with respect to the sampling apparatus and conditions relevant to the routine ECS air quality verification procedures during launch processing operations. In brief, the low overall transmission efficiency indicates that the measurement of 5-micrometers and larger particles routinely done in the ECS air sampling procedures is highly unlikely to provide valid data due to the significant particle sampling losses. On the other hand, the measurement of 0.5-micrometers particles serves as a better indicator for the purge air quality verification owing to nearly 100% transmission efficiency for this particle size range.
| Limitations: |
 APPROVED FOR PUBLIC RELEASE |
| Pages: |
44 |
| Report Date: |
15 Jul 2009 |
| Contract Number: |
FA8802-09-C-0001 FA880209C0001 |
| Report Number: |
A931605 |
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