Implementation of Acoustic Blankets in Energy Analysis Methods with Application to the Atlas Payload Fairing

Abstract

Energy analysis methods are commonly used to predict the vibroacoustic response of a spacecraft inside a launch vehicle payload fairing during liftoff. The payload fairing wall is often lined with acoustic blankets which can be difficult to model. This paper shows the development of a practical working method for accurately representing acoustic blankets in a VAPEPS statistical energy analysis model. A clear scaling relationship between the acoustic absorption coefficient and the blanket thickness is established. The scaling procedure is demonstrated using two sets of data for different absorption materials. The absorption data are implemented in VAPEPS by converting them to frequency-dependent damping loss factors. A post-processing procedure is derived to account for the increase in transmission loss due to the addition of the blanket layer. The entire process is used to predict the noise reduction in a VAPEPS model of the Atlas 14-ft-diameter payload fairing. Comparisons to ground-test and flight data for the blanketed fairing are presented to validate the procedure.