High Temperature, High-Strength Refractory CMC Pintles for Controllable Solid Propulsion Systems, Phase II

Improved solid propulsion systems for missile defense interceptors require higher performance, including enhanced acceleration, extended flight duration, and greater aerothermal heating capability, all of which lead to requirements for higher performance materials with combined structural and insulating capabilities. Pintles in controllable solid propulsion systems, such as divert and attitude control systems (DACS), face a challenging operating environment that includes very high temperatures and large thermal gradients. Increasing the performance of these systems makes that environment even more challenging, as pintles in a DACS motor are attached to or near sensitive electrical components that cannot be exposed to high temperatures. In the Phase I project, Ultramet addressed the MDA pintle material requirement through the development of two pintle material systems. The first was made entirely with UltrametÆs carbon fiber-reinforced zirconium carbide matrix (Cf/ZrC) ceramic matrix composite (CMC), and the second comprised a Cf/ZrC CMC shaft with a chemical vapor deposited (CVD) rhenium tip for the sealing surface. Baseline pintle models were developed, based on existing Cf/ZrC CMC and rhenium properties, for a full-scale DACS pintle in a representative solid rocket motor environment. The models showed that both configurations could be manufactured to meet DACS material and performance requirements. The rhenium-tipped pintle with a Cf/ZrC CMC shaft was downselected for further development, as the design meets MDAÆs DACS material and performance requirements, showed good promise in both the modeling and fabrication demonstration efforts, and provides significantly more potential for increased pintle performance in future design iterations. In Phase II, design and analysis will be updated to include enhancements to the Cf/ZrC CMC material model, to the pintle model design, and to the pintle model and geometry for a full-scale DACS motor. The goal will be to architect a pintle component with reduced thermal conduction into the actuator system. Full-scale pintle fabrication will be performed for hot gas testing that will validate the material system and fabrication process. The fabrication process will be designed as a production process that is ready for transition to a program of record after Phase II completion. To support and anchor the Cf/ZrC CMC modeling effort, a detailed temperature-dependent thermal and mechanical properties database will be collected for the new variations of the CMC material developed for the pintle design. To validate the pintle design and anchor its model, a full-scale pintle will be tested in a full-scale solid motor in a representative DACS environment. Approved for Public Release | 23-MDA-11635 (9 Nov 23)