Simulation of a multilayer thermal protection system submitted to conditions representative of atmospheric reentry
- Paper number
IAC-06-C2.7.08
- Author
Dr. Gino Genaro, Instituto Nacional de Pesquisas Espaciais (INPE), Brazil
- Coauthor
Dr. José Bezerra Pessoa-Filho, CTA-IAE, Brazil
- Year
2006
- Abstract
Multilayer insulation systems (MLI) have been employed in the thermal control of cryogenic tanks, satellites and space vehicles submitted to severe heating during their reentry in the earth's atmosphere. MLI consists of several reflective foils separated from each other by spacers, made of semitransparent materials, with low thermal conductivity. The heat transfer process through such semitransparent media is a complex phenomenon, in which conduction and radiation heat occur simultaneously. The purpose of the present work is to perform a numerical analysis of these phenomena aiming at the development of a design tool capable of predicting the thermal behavior of MLI systems. After validation, the proposed technique is used to analyze the thermal protection system of a recoverable microsatellite. Formulation To investigate the problem, transient and steady state combined conduction-radiation heat transfer between parallel flat surfaces separated by semitransparent media is considered. The boundaries and interfaces (reflective foils) are assumed to be opaque and gray. The medium separating the foils (spacer) emits, absorbs and isotropically scatters thermal radiation. A transient heat flux is applied at one of the boundaries. Based upon the application of the overall energy and radiative conservation principles, a relationship between the two heat transfer modes, i.e., radiation and conduction, is established. The space and time derivatives are discretized according to the finite difference method. To solve the Radiative Transfer Equation - RTE, a novel discretization scheme is used, based on the discrete ordinate method concept, but with a mathematical treatment of the discontinuities in the radiative intensity. Results Based upon the obtained results, it was possible to investigate the feasibility of some of the proposed thermal protection designs, as well as of the importance of the number, optical properties and positioning of the reflective foils on the MLI systems. The effects of the optical thickness of the spacers on the MLI performance have also been investigated. The results have showed the high efficiency of the MLI thermal protection system in protecting the external structure of the microsatellite during atmospheric reentry. It was observed that, while external surface of the MLI experiments a sharply temperature growth, the temperature of internal surface is kept below 150°C. It was also confirmed the high performance of the MLI in reject part of the heat actuating on its external surface during atmospheric reentry.
- Abstract document
- Manuscript document
IAC-06-C2.7.08.pdf (🔒 authorized access only).
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