A UNIQUE SILICON-CARBIDE REUSABLE THERMAL PROTECTION MATERIAL NOVEL THERMAL PROTECTION MATERIALS

A NEW AND UNIQUE PROCESS (CHEMICAL VAPOR REACTION; CVR) TO CONVERT GRAPHITE STRUCTURES TO LOW DENSITY SIC STRUCTURE WILL BE INVESTIGATED TO PRODUCE HIGH TEMPERATURE THERMAL PROTECTION MATERIALS. AVAILABLE HEAT SHIELDS INCLUDE CARBON PHENOLICS WHICH OCCUPY A LOT OF SPACE AND MORE RECENTLY DEVELOPED REUSABLE SURFACE INSULATION UTILIZING RIGID FIBROUS STRUCTURE OF SILICA AND ALUMINA HAVE A LIMITED TEMPERATURE CAPABILITY TO ABOUT 2500 DEGREES FAHRENHEIT. BOTH OF THESE HEAT SHIELD INSULATORS HAVE EXTREMELY LOW MECHANICAL PROPERTIES. IN THIS PROPOSED PROGRAM NET SHAPE LOW DENSITY SIC, WITH EXCELLENT STRENGTH, EXCELLENT THERMAL SHOCK RESISTANCE, HIGHEMISSIVITY, HIGH TEMPERATURE CAPABILITY AND LOW THERMAL CONDUCTIVITY WILL BE DEVELOPED. THE PROPERTIES OF THE SIC WILL BE OPTIMIZED BY INVESTIGATING THE EFFECT OF GRAPHITE PRECURSOR'S DENSITY AND MICROSTRUCTURE AND THE EFFECT OF CVRPROCESS OPERATING PARAMETERS. THE CVR-SIC MATERIALS WILL ALSO BE CVD SIC COATED TO IMPROVE ABLATION RESISTANCE. TESTSPECIMENS WILL BE FABRICATED AND FULLY CHARACTERIZED AND SAMPLES WILL BE DELIVERED TO NASA FOR EVALUATION.