A Probabilistic Sizing Tool and Monte Carlo Analysis for Entry Vehicles Ablative Thermal Protection Systems
- Paper number
IAC-08.C2.7.5
- Author
Dr. Antonio Mazzaracchio, University of Rome "La Sapienza", Italy
- Coauthor
Prof. Mario Marchetti, University of Rome "La Sapienza", Italy
- Year
2008
- Abstract
An implicit ablation and thermal response software has been developed to perform the analysis and the sizing of charring ablative thermal protection systems for entry vehicles. The adopted thermo-physical model takes into account: heats of formation; decomposition kinetic; simplified surface chemistry; pyrolysis and surface recession effects; characteristics of the aeroshell substructure; dependence of thermal and physical properties from temperature, pressure and ablative material status. Moreover a variety of initial temperature distributions and a choice of inner/outer surfaces conditions can be selected as well mission type and entering heat fluxes, those latter via either engineering correlation equations or databases. A statistical monitor integrated in the tool, referring to a Monte Carlo technique, allows a simulation running over stochastic series in order to perform an uncertainty and sensitivity analysis aimed at estimating the probability of maintaining the temperature of the underlying material within specified requirements. The probability distribution function of the obtained thermal protection system thickness and the related uncertainty contributions from each input parameter - deriving from aerothermal environment and from ablative and substructure materials - are the most important outputs of interest in this approach. The determination of which material properties have the greater impact on heat shields sizing can address further experimental investigations and researches in order to improve material performances and to decrease heat shield mass fraction. This approach and the associated software are considered mainly helpful during the conceptual and the preliminary design phases of spacecraft thermal protection systems and they can be proposed as an alternative with respect to traditional approaches used till today as Root-Sum-Square method. Verification of the developed tool is performed through the comparison with some results of previous works on thermal protection system probabilistic sizing methodologies based on industry-standard, high-fidelity ablation and thermal response program. It points out that the resulting thickness probability distribution function, for forebody thermal protection system of Mars Exploration Rovers and Stardust entry systems, obtained in this work and the relevant uncertainty contributions are successfully compared with respect to the corresponding probabilistic results of Chen, Laub et al. (AIAA Paper 2006-2951), based on the “Fully Implicit Ablation and Thermal” (FIAT) NASA Ames Research Center response code. New study cases have been analyzed in order to establish the margins on sizing heat shields currently proposed for vehicles, using rigid aero shells, devises for aerocapture missions at Neptune and to identify the major sources of uncertainty in the material response.
- Abstract document
- Manuscript document
IAC-08.C2.7.5.pdf (🔒 authorized access only).
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