Derivation of atmospheric gust-forcing functions for launch-vehicle loads analysis

A methodology is developed to derive gust-forcing functions from the turbulent components of measured wind profiles. Several large sets of forcing functions were developed by extracting the short-duration, random component of measured Jimsphere wind profiles. A database consisting of Jimsphere wind soundings measured over the past three decades at the Eastern and Western Ranges of the United States was used to derive the forcing functions. Validity of these forcing functions for heavy-lift and medium-lift launch vehicles was established by examining the error contributions from various sources within the wind measurement system and the application of a noise-reducing filter. A unique aspect of the method is the extraction of the relatively rapidly changing turbulent component associated with the nonpersistent wind features, which are expected over a given observation time period. The gust-forcing functions can be used in a Monte Carlo analysis to determine launch-vehicle loads for the Eastern and Western Ranges.