Design of thermal protection based on open cell carbon foam structure optimization

Abstract

Open cell carbon foams with porosity ranging between 82 and 98% can be used as efficient thermal insulation in many high-temperature applications including solar and planetary probes, whose structures and systems are exposed to extreme heat loads. Physical properties of cellular materials are determined not only by thermal and optical properties of solid phase but also significantly by their morphology and fabrication technology. This implies the possibility to create open-cell materials with desirable properties, optimal for specific operating conditions. The paper presents a methodology for optimal design of multilayer thermal protection based on high porosity open cell carbon foam, taking into account the carbon foam morphology. The traditional thermal design problem statement implies the determination of layers thickness for multi-layer thermal insulation, ensuring required operational temperature on the boundaries of layers and minimum of total mass of system. In this work the cell diameter and porosity, that characterize the material’s morphology, are chosen along with thickness of layers in order to obtain an additional weight advantage of thermal insulation. The optimization problem is solved using the algorithm based on the projected Lagrangian method with the quadratic subproblem. To illustrate the implementation of the developed algorithm and the corresponding software, the problem of choosing of the optimal layer thickness for the multilayer heat shield of the solar probe along with the cell diameter and porosity of carbon foam, forming one of the layers, is considered.