3D-Reinforced Melt-Infiltrated Pintle Material

Current and future missile platforms employ throttling solid propulsion systems to navigate and maneuver to target. At the heart of these types of throttling divert attitude control systems (TDACS), is a pintle which can be actuated in relation to the throat and exit nozzle to regulate the thrust of the motor. By pulsing on and off at different thrust levels for varying durations during flight, a missile can be maneuvered along a precise trajectory. Future missile systems will place increased thermostructural demands on pintle materials by employing hotter burning propellants, increased combustion chamber pressures, and longer burn times. Such extreme operating environments are beyond the capability of the current needled carbon silicon carbide (C/SiC) pintle material. Specifically, novel pintle materials will need to have higher tensile strength and lower thermal conductivity properties than the current material. High tensile strength is needed to withstand the large thermomechanical stresses imposed on the pintle during operation and low thermal conductivity to prevent heat from soaking into the internal components of the motor. MR&D is proposing to build upon the results of a successful Phase I effort to optimize, manufacture, and test full-scale TDACS pintles. The pintles will be machined from 3D woven carbon fiber preforms which will be fully densified using a quick, and low-cost melt infiltration process to form a SiC matrix. Material characterization and analytical modeling results gathered during the Phase I effort indicate that the novel pintle material can meet both the strength and thermal conductivity requirements. In this Phase II effort, MR&D proposes to use in-house micromechanics models, characterization data measure during Phase I, and lessons learned during weaving trials to optimize the weave geometry and maximize thermomechanical material performance. High temperature coatings and integration of metallic nose tips will be studied as ways to extend the high temperature capability of the pintles beyond 4000░F. To further validate and develop the material, a full database of thermomechanical material properties will be generated at temperatures ranging from 75-3500░F. In addition, subscale thermal shock testing will be conducted on pintle specimens using an induction heating apparatus. The subscale tests will characterize material performance under rapid heating conditions like those in an operational motor environment. Near the end of the Phase II program, MR&D will test one or more full-scale pintles in solid rocket motor ground tests. If successful, this highly flexible process for producing TDACS pintles can be optimized and transitioned to quickly and reliably manufacture the materials needed to meet the ever-increasing demands of evolving missile systems. Approved for Public Release | 23-MDA-11635 (9 Nov 23)