Effects of transonic buffeting on a hammerhead-shaped payload.

Abstract

An analytical and experimental program was conducted to improve the capability of determining the effects of transonic buffeting on pay loads of launch vehicles. An analytical method was developed to apply experimental data, using power spectral techniques, in the analytical prediction of vehicle structural loads. To solve the loads problem without unsupported assumptions, a wind-tunnel test was conducted on a hammerhead-shaped pay load to measure the needed power spectral and cross-power spectral density functions of the local buffeting forces or pressures. The reduced experimental data, circumferential correlations of unsteady pressures, longitudinal correlations of unsteady pressures and local normal force, power spectra and cross-power spectra of unsteady pressures, and local normal force for freestream Mach number 0.91, and angle of attack of 0° to 6° are illustrated. These data indicate large negative values of longitudinal correlation between fluctuating pressures and local normal force in the boattail region. Bending moment responses were computed on a launch vehicle using measured cross-correlation or cross-power spectra between the buffet disturbances. The responses were smaller than that computed using zero correlation between the disturbances, and larger than the calculated response caused by atmospheric turbulence.