Multiscale Modeling Including Micromechanical Failure Prediction

The temperature constraints of current thermal protection system (TPS) materials limit the flight path and thus the mission flexibility of existing and new hypersonic and spacecraft reentry vehicles, such as the Military Space Plane (MSP). Lightweight materials with increased TPS operational temperature to over 3000 degreeF and improved surface durability and erosion resistance will create numerous opportunities for these applications. The shortcomings of current insulating materials (e.g. AETB, FRCI, SIRCA) include lack of structural stability at temperatures below=2800degrees F, high density (=12-20 lb/ft3/), and high cost (+$2.50-3.00/in3). The innovative TPS proposed in this project will provide an unequaled combination of structural and thermal properties, including temperature capability to >4500 degree F with outstanding erosion resistance. This TPS will combine Ultramet's lightweight, low-cost, low thermal conductivity (low-k) reticulated vitreous carbon (RVC) foam with aerogel insulation to reduce high temperature thermal conductivity and a frontside facesheet coating of refractory Ultra2000 TM, Ultramet's patented hafnium carbide/silicon carbide (HfC/SiC) coating system. Previous work has shown that the low-k RVC foam has comparable thermal conductivity to the current best insulators (AETB-12 and FRCI-12) with twice the compressive strength at temperatures of <1830degress F. At higher temperatures, radiative heat transfer within the foam results in rapid increases in thermal conductivity. The addition of low-density, low radiative heat transfer aerogels produced by Lawrence Livermore National Laboratory presents a novel approach to reducing radiative heat transfer with minimal increase in density and conductive heat transfer. In the proposed project, aerogels with be integrated with foam structures, and high temperature thermal conductivity will be measured to assess the feasibility of this novel concept.