The purpose of this program was to develop two thermal-shock- resistant composite carbide systems that could be reliably used with high-flame temperature solid rocket propellants. The selected systems were: (1) a microcomposite consisting of a tantalum/hafnium monocarbide and tantalum/hafnium alloy, and (2) a tantalum-carbide coated, tantalum carbide/graphite hypereutectic. Fabrication procedures were developed, and ambient and elevated temperature properties were characterized for both the microcomposite and TaC/C hypereutectic systems. The composites were evaluated for thermal shock and chemical corrosion resistance in a hyperthermal environmental simulator using subscale inserts. Scale-up of the fusion casting of the TaC/C hypereutectic composite to produce 4.2-in.-dia by 3.0-in.-long billets was demonstrated. Two solid propellant motor firings using 6500F propellant were conducted on nozzles containing TaC/C hypereutectic throat inserts.