Preliminary Thermal-Mechanical Sizing of Metallic TPS: Process Development and Sensitivity Studies

PRELIMINARY THERMAL-MECHANICAL SIZING OF METALLIC TPS:PROCESS DEVELOPMENT AND SENSITIVITY STUDIESCarl C. Poteet*NASA Langley Research Center, Hampton, VirginiaandHasan Abu-Khajeel*, Su-Yuen Hsu*Lockheed Martin Space Operations, Hampton, VirginiaAIAA2002-0505AbstractThe purpose of this research was to performsensitivity studies and develop a process to performthermal and structural analysis and sizing of the latestMetallic Thermal Protection System (TPS) developed atNASA LaRC. Metallic TPS is a key technology forreducing the cost of reusable launch vehicles (RLV),offering the combination of increased durability andcompetitive weights when compared to other systems.Accurate sizing of metallic TPS requires combinedthermal and structural analysis. Initial sensitivitystudies were conducted using transient one-dimensionalfinite element thermal analysis to determine theinfluence of various TPS and analysis parameters onTPS weight. The thermal analysis model was then usedin combination with static deflection and failure modeanalysis of the sandwich panel outer surface of the TPSto obtain minimum weight TPS configurations at threevehicle stations on the windward centerline of arepresentative RLV. The coupled nature of the analysisrequires an iterative analysis process, which will bedescribed herein. Findings from the sensitivity analysisare reported, along with TPS designs at the three RLVvehicle stations considered.Copyright © 2002 by the American Institute ofAeronautics and Astronautics, Inc. No copyright isasserted in the United States under Title 17, U.S. Code.The U.S. Government has a royalty-free license toexercise all rights under the copyright claimed hereinfor Governmental Purposes. All other rights arereserved by the copyright owner.*Research Engineer, Metals and Thermal StructuresBranch, Structures and Materials Competency*Aeronautical Engineers, Lockheed Martin SpaceOperations.IntroductionThermal Protection Systems (TPS) on ReusableLaunch Vehicles (RLV) are required to be light weightwhile providing protection from heating during reentryand insulation to cryogenic fuel tanks during groundhold. Recent design goals for RLV have called for"Commercial Aircraft Like" operations, which furtherincreases the importance of the TPS. To meet thesegoals, TPS must not only be a good insulator capable ofwithstanding cryogenic and reentry temperatures, but itmust be durable and easily maintained. To increaseRLV operability, the TPS may be required to withstandexposure to rain and hail.ARMOR TPS is sized herein to meet the insulationand structural requirements resulting from thegroundhold cryogenic environment as well as the ascentand reentry aerothermal heating environments. Theanalysis focuses on sizing of the fibrous insulation layerand sizing of the honeycomb sandwich on the ARMORTPS outer surface. Dimensions for other componentsare based on work reported by Blosser, et al.3Insulation layers are sized by the aerothermal heatingand cryogenic conditions experienced in the threeenvironments, while the honeycomb sandwich panel onthe ARMOR TPS outer surface is sized consideringaerodynamic pressure, acoustic pressure, and thermalgradients. Since the thermal performance is dependenton the structure and the structural response is dependenton the temperatures in the TPS, the thermal andstructural analyses are coupled, requiring an iterativeanalysis alternating between thermal and structuralanalyses.This paper represents one of several reporting on thedevelopment of Adaptable Robust Metallic OperableReusable (ARMOR) TPS at NASA Langley ResearchCenter. 1-5 ARMOR TPS, as shown in Figure 1,employs a light weight metallic structure to encapsulatehigh efficiency fibrous insulation and reactaerodynamic pressure to the vehicle structure. The goalof ARMOR TPS development is to improve operationalfeatures, increase adaptability (by allowing attachmentto different tank and structural configurations), andAmerican Institute of Aeronautics and Astronautics