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Reverberant electromagnetic fields within launch vehicle payload fairings

Kabiri, Shabir

A launch vehicle payload fairing scale model has been designed, fabricated, and tested at Oklahoma State University to investigate the reverberant electromagnetic fields within launch vehicle fairings. The OSU fairing model uses a mechanical stirrer to attain statistically uniform fields within the fairing cavity. A removable payload model and a payload adapter model are included in the fairing to study the interactions of fields with these structures. Acoustic and RF absorbing foams and blankets are used in the fairing model to represent actual launch vehicle environments. Power balance model suggests that different regions of the fairing can be modeled as separate resonant cavities with energy transferring between them. This study investigates the quality factor (Q) measurement of the payload fairing sub-regions to verify the application of power balance model in payload fairings. The quality factor of the empty fairing measured from about 32 dB at 1 GHz to 41 dB at 6 GHz. Measurement in three different regions of the fairing when no absorber was added yielded quality factors similar to that of the empty fairing, indicating that the fairing behaves as single resonant cavity. After adding the absorbers, the quality factor measured in the fairing sub-regions were significantly reduced, indicating that the three regions of the fairing behave as separate but coupled cavities as expected from the power balance model.