Identifying Slowly Varying and Turbulent Wind Features for Flight Loads Analyses

A methodology is developed to determine the spectral boundary between wind features that can be considered slowly varying and the more rapidly varying, or turbulent, features of measured wind profiles. Pairs of measured wind velocity vs altitude profiles from the Eastern and Western launch ranges of the United States were used to establish the vertical wavelengths, which could no longer be considered slowly varying over discrete time intervals. Analyses were performed for wind pairs that were 30, 60, 90, and 120 min apart. The wavelength boundary between slowly varying and turbulent wind features as a function of time interval is presented. The results of this work now make it possible to identify and extract the slowly varying and turbulent wind features at a particular launch site. Identifying slowly varying and turbulent wind features is important in that it permits a potential reduction in the predicted loads on launch vehicles using measured wind profiles taken just prior to launch.