Idealized Modeling and Analysis of the Shuttle Orbiter Wing Leading Edge Impact Data

Some selected segments of the ascent and the on-orbit data from the Space Shuttle flight, STS114, as well as some selected laboratory test article data have been analyzed using wavelets, power spectrum and autocorrelation function. Additionally, a simple approximate noise test was performed on these data segments to confirm the presence or absence of white noise behavior in the data. This study was initially directed at characterizing the on-orbit background against which a signature due to an impact during on-orbit operation could be identified. The laboratory data analyzed here mimic low velocity impact that the Orbiter may be subjected to during the very initial stages of ascent. A high velocity impact to an RCC airfoil that could represent an impact in flight was modeled using the finite difference structural dynamic simulator, FiDDLE¹ Even though there are differences between the actual wing leading edge and the simple airfoil geometries as well as an essential difference between the characteristics of the flight impact and the modeled impact, a comparison between an ascent phase signature and this modeled signature has provided some useful insight. Indeed, the high frequency impact signature observed in the modeling results at a given numerical sensor location is similar to that present in the Orbiter ascent data as recorded on unit 1023. Also, the modeled stress signatures suggest that a single-axis accelerometer be oriented in a preferred direction, given the type of impact.