TCAT - A tool for automated thermal protection system design

Abstract

INTRODUCTION This paper outlines the development of a new computational heat transfer tool for generating 1-D temperature profiles within thermal protection system materials covering advanced reusable space launch vehicles. The Thermal Calculation Analysis Tool (TCAT) also contains an optimization capability to determine the minimum thickness of thermal protection materials required to prevent the vehicle substructure from exceeding its operating temperature limit. TCAT is designed to be used in the conceptual design environment with compatible aeroheating analysis tools and an external materials database. The code is very fast (executes in minutes) and easy to use. Both single TPS material constructs and multi-layer TPS can be analyzed. TCAT is written in FORTRAN 77. A World Wide Web interface has also been implemented to allow easy remote access to the code. The heat transfer assumptions and numerical techniques used to develop TCAT are discussed. The results of two test and validation cases are reported. The first test case involved TPS designs for a 10° half-angle cone, and the second analyzed TPS designs on a multiple angle wedge with angles of 5° and 10°. The designs involved sizing thermal protection systems from each of the material groups available from the WWW interface. The tile materials that were chosen for the design test cases produced unit weight values that ranged from 1.4-1.6 lbm/ft, and the blanket material TPS designs resulted in average unit weights between 0.4-0.6 lbm/ft. f Graduate Research Assistant, School of Aerospace Engineering, Student member AIAA. ' Assistant Professor, School of Aerospace Engineering, Senior member AIAA. Copyright © 2000 by Karl K. Cowart and John R. Olds. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. Thermal protection system (TPS) sizing requires the selection of materials and a configuration that effectively protects the launch vehicle and its cargo/passengers from the severe heating environment encountered during reentry and ascent. The overall design process involves several levels: conceptual, preliminary, and detailed design. At the conceptual level, a large number of TPS concepts and ideas are explored using engineering-level tools that must provide a reasonably accurate assessment of the materials needed and the individual acreage weights required.. In preliminary design, the design space is narrowed as the concept becomes more defined. Higher fidelity tools enable the designer to increase the level of analysis detail and explore key local heating phenomena. In detailed design, the external vehicle shape and flight trajectory are set, and time is available to setup a high fidelity fluid-structures analysis to very accurately account for the temporal and spatial heating characteristics within the TPS system. The work in this paper is targeted at the level of conceptual design. TCAT is meant to provide a quick-look analysis at several control points on the vehicle's surface and aid the TPS designer in selecting an appropriate acreage material and thickness with reasonable accuracy and speed. In a previous paper first introducing TCAT, Cowart discussed the differences between 'static, off-line' and 'dynamic, on-line' TPS sizing. The 'static, off-line' sizing process is commonly used in conceptual design organizations. It typically requires the TPS designer to make 'best guess' engineering assumptions in the early part of the design process that do not change as the vehicle subsequently changes size or the trajectory changes. For example, TPS unit weights and distribution of key materials types might be selected based on historical data before the vehicle design is even closed. For expedience, these estimates are often not revisited (c)2000 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization.