A Methodology for Mapping Launch Vehicle Buffet Loads

Buffet loads represent the primary source of high frequency loading for launch vehicles during the ascent portion of flight. Currently, experimental techniques establish the nature of buffeting using a rigid scale model of the vehicle. The buffet forcing functions resulting from such tests are then applied to reduced finite -element models of the full-scale vehicle to determine the response and consequent loading. This paper discusses the techniques required to translate model-derived, empirical buffet forcing functions into responses for the full-scale launch vehicle, as used to determine the buffet loading for NASA's Ares I launch vehicle. I. Introduction UFFET loads have been a key consideration for launch vehicles since the earliest years of the U.S. space program. Indeed, launch vehicles have been lost due to the high-frequency vibrations and loading that may occur due to buffet. Buffeting is closely associated with the transonic time of flight, where oscillating shocks and regions of unsteady, separated flow produce random aerodynamic inputs on a vehicle over a wide range of frequencies. This results in excitation of a variety of modes ranging from the vehicle's primary bending modes to higher-frequency component and panel modes. 1