Low-Cost, Ultrahigh Temperature Zero-Erosion Ceramic Matrix Composite for SM-3 TDACS Divert Valve Pintles, Phase II

Future performance goals for ballistic missile defense systems necessitate the development of zero-erosion throat materials for boost and tactical solid rocket motors. Increasing demands imposed by advanced solid propellants used in systems such as throttling divert and attitude control systems (TDACS) require zero-erosion materials for pintles and throats capable of surviving ultrahigh temperature thermal, chemical, and mechanical environments. The use of robust materials with broad operational capability leads to simpler and lower cost designs. Current Aerojet TDACS divert valve pintle designs employ a Novoltex silicon carbide (SiC) composite. As the system is upgraded and higher temperatures, pressures, and burn times are required, a refractory ceramic matrix composite (CMC) with a use temperature well beyond that of SiC will be needed. In previous work for DoD and NASA, Ultramet has fabricated a variety of carbon fiber-reinforced refractory CMC engine and airframe components using a rapid and low-cost melt infiltration process. CMCs based on various combinations of SiC, zirconium carbide, and hafnium carbide have been subjected to ultrahigh temperature testing in liquid and solid propellant combustion environments at NASA Glenn Research Center, the Air Force LHMEL facility, and ATK-GASL with surface temperatures as high as 5200°F. In each case, the material exhibited high structural integrity and virtually no erosion while at a substantially lower density than refractory metals such as tungsten and rhenium. The potential exists to adapt and optimize this technology for fabrication of components used in advanced TDACS under development by Aerojet. In Phase I, Ultramet established the initial feasibility of a melt infiltrated carbon fiber-reinforced zirconium-silicon carbide (Zr Si C) matrix composite for use as a TDACS divert valve pintle that offers substantial use temperature, manufacturing, and cost advantages over conventionally fabricated composites based on SiC. The project combined detailed structural and thermal analysis of the pintle by Materials Research and Design (MR&D), design support and guidance from Aerojet, and advanced composite material development at Ultramet. In Phase II, pintle materials and processing optimization will be expanded, in conjunction with comprehensive thermostructural analysis at MR&D and Aerojet design requirements input. The ultimate Phase II objectives are to demonstrate cost-effective manufacturing of zero-erosion Cf/Zr-Si-C composite divert valve pintles and establish their performance through two stages of hot-fire testing at Aerojet in a 5-inch pressure-controlled end-burning test motor under anticipated SM-3 Block IB and/or Block IIA TDACS operating conditions. Following successful Phase II results, Aerojet intends to rapidly transition to Phase III testing of full-scale pintles under the Block IIA program, quickly bringing the technology to TRL 6.