Flutter Analysis of the Thermal Protection Layer on the NASA HIAD

Abstract

A combination of classical plate theory and a supersonic aerodynamic model is used to study the aeroelastic flutter behavior of a proposed thermal protection system (TPS) for the NASA HIAD. The analysis pertains to the rectangular configurations currently being tested in a NASA wind-tunnel facility, and may explain why oscillations of the articles could be observed. An analysis using a linear flat plate model indicated that flutter was possible well within the supersonic flow regime of the wind tunnel tests. A more complex nonlinear analysis of the TPS, taking into account any material curvature present due to the restraint system or substructure, indicated that significantly greater aerodynamic forcing is required for the onset of flutter. Chaotic and periodic limit cycle oscillations (LCOs) of the TPS are possible depending on how the curvature is imposed. When the pressure from the base substructure on the bottom of the TPS is used as the source of curvature, the flutter boundary increases rapidly and chaotic behavior is eliminated.

In-Flight Aeroelastic Stability of the Thermal Protection System on the NASA HIAD, Part II: Nonlinear Theory and Extended Aerodynamics

“…Observations of oscillatory motion and failure of these samples during testing suggested that aeroelastic effects needed additional study, and theoretical model development was required. Goldman, Dowell, and Scott 6,7 developed several theoretical aeroelastic models for the TPS coupons, and agreement between theory and experiment for select cases was achieved. A rough prediction of in-flight stability can be made from these plate-like models; however, more precise predictions require structural models consistent with the in-flight TPS geometry, i.e.…”