Metallic Thermal-Protection-System Panel Flutter Study

Abstract

Panel flutter analysis results of a reusable launch vehicle metallic thermal protection system [Ref.l] panel are presented in this paper. Panel flutter is a self-excited aeroelastic vibration. The unsteady aerodynamic theory used in this study is the first- and second-order piston theory. The analysis capability is incorporated into a commercial finite element code with the goal of providing a useful tool for aerospace engineers —MSC/MARC [Ref.6]. The capability consists of three parts: linear flutter analysis, linear flutter analysis with arbitrary flow direction, and nonlinear hypersonic flutter analysis. Structural nonlinearities are not considered. The current paper covers both panel flutter analysis tool development as well as parametric panel flutter study of a specific metallic TPS configuration. The resulting analytical tool was used to analyze a metallic TPS being built for the X-33 experimental vehicle. The results show that nonlinear, hypersonic aerodynamic terms were found to have an insignificant effect on the panel flutter predictions for the X-33 TPS. The honeycomb sandwich that comprises most of the outer surface of the X-33 TPS panel was found to have large margins of safety for panel flutter for all flight conditions. However, the outer overlapping, panel-to-panel seals were predicted