Post-flight acoustic analysis of Epsilon launch vehicle at lift-off

Abstract

Acoustic level both inside and outside the fairing is measured at the first Epsilon Launch Vehicle (Epsilon-1). The obtained data shows time-varying fluctuation due to the ascent of the vehicle. Equivalent stationary duration for such non-stationary flight data is determined based on the procedure described in NASA HDBK-7005. The launch pad used by the former M-V launcher is modified for the Epsilon based on the Computational Fluid Dynamics (CFD) and 1/42-scale model tests. Although the launch pad is compact and any water injection system is not installed, 10 dB reduction in overall sound pressure level (OASPL) is achieved due to the modification for the Epsilon, comparing with the M-V. Acoustic level inside the fairing satisfies the design requirement. Acoustic design of the launch pad developed here is revealed to be effective. Prediction of the acoustics level based on the Computational Fluid Dynamics (CFD) and subscale testing is also investigated by comparing with the flight measurement.