Fundamental Modeling and Thermal Performance Issues for Metallic Thermal Protection System Concept

Abstract

A study was performed to develop an understanding of the key factors that govern the performance of metallic thermal protection systems for reusable launch vehicles. A current advanced metallic thermal protection system concept was systematically analyzed to discover the most important factors governing its thermal performance. A large number of relevant factors that influence the thermal analysis and thermal performance system were identified and quantified. Detailed finite element models were developed for predicting the thermal performance of design variations of the metallic thermal protection system concept mounted on a simple, unstiffened structure. The computational models were also used, in an automated iterative procedure, for sizing the metallic thermal protection system to maintain the structure below a specified temperature limit. A statistical sensitivity analysis method, based on orthogonal matrix techniques used in robust design, was used to quantify and rank the relative importance of the various modeling and design factors considered in this study. Thermal performance was shown to be sensitive to several analytical assumptions that should be chosen carefully. Of the design factors studied, the heat capacity of the underlying structure was found to have the greatest effect on thermal performance. Therefore the structure and thermal protection system should be designed concurrently. NomenclatureMach number N u = average Nusselt number Pr = Prandtl number Ra = Rayleigh number Re L = Reynolds number based on L c T init = initial temperature, • F T lim = allowable temperature limit, • F T max = maximum temperature, • F t = thickness, in. Z = altitude, kft α = angle of attack, deg η = calculated response in sensitivity analysis

Analysis of Reusable Integrated Thermal Protection Panel Elements with Various Insulating Core Options

“…21 So the parameter selection for design variables for sizing optimization is an issue. 22 FEA software is often utilized for analysis of the complex structures such as honeycombs and corrugated stiffeners. 23,24 In some cases, the thermal analysis model can be simplified from 3D to 2D and/or 1D after homogenization of the insulation layer, 18, 25-27 which is often followed by a static structural analysis only under the mechanical loading conditions separately.…”

Probabilistic Heat Transfer Problems in Thermal Protection Systems

“…In order to solve the connection difficulties, the outer honeycomb sandwich panel is connected to support structure at each corner of the panel box by the metal bracket. The pressure load is transmitted through the four flexible supports and the beam structure of the panel box, not only avoiding thermal interference but also to allow free thermal expansion of the outer surface [4,5].…”

Contact sensitivity analysis of a coupling pin for the nose cap of a launch re-entry vehicle

“…This means that such structures must tolerate the high temperatures engendered by aero-thermal re-entry fluxes but also resist the internal stresses related to such temperature fields. The TPS conceptssuccessfully tested on the Space Shuttle for over thirty years -have been proved to be quite ineffective with respect to the reusability requirement: in fact, the TPS tiles are subjected to a complex after flight inspection/reparation management, which is not very efficient from a time/cost point of view [3][4]. To overcome these limitations, for highly aero-thermally stressed structures the TPS concepts may be substituted by "hot structure" concepts, in which the structure itself is conceived to resist the aero-thermal fluxes without employing TPS tiles [2][3][4][5].…”

“…The TPS conceptssuccessfully tested on the Space Shuttle for over thirty years -have been proved to be quite ineffective with respect to the reusability requirement: in fact, the TPS tiles are subjected to a complex after flight inspection/reparation management, which is not very efficient from a time/cost point of view [3][4]. To overcome these limitations, for highly aero-thermally stressed structures the TPS concepts may be substituted by "hot structure" concepts, in which the structure itself is conceived to resist the aero-thermal fluxes without employing TPS tiles [2][3][4][5]. The present work refers to the SHS project and in particular illustrates the process performed in order to size the pin that has to guarantee the connection between two parts of the USV-SHS nose represented schematically in figure 1.…”