Non-Eroding Sonic Throat (NEST)

Renewed efforts to increase Divert Attitude Control System (DACS) performance by increasing flame temperature will inevitably cause current state-of-the-art non-eroding materials to fail. Without the oxygen scavenging, motor performance Industrial Solid Propulsion (ISP), is limited to lower performance propellants. This approach gives up substantial ISP. New solutions for throats and pintles are needed to address current material shortcomings and move beyond the physics-based limitations facing all-metallic solutions. Ceramic matrix composites (CMC) composed of carbide-based ceramics show promise in providing non-eroding performance with high performance non-Aluminized propellants based on their high melting points (MP), their oxidation resistance at elevated temperatures, and the melting points / low vapor pressure of their respective oxides. In addition, the CMC fiber architecture provides a robust mechanical solution for thermal shock that monolithic ceramics, sintered refractory alloy powders, cermets or other non-continuous fiber material designs simply cannot provide. In Phase II, EXO, working with its fabrication partner, and a materials analysis subcontractor will continue development of its innovative refractory melt infiltrated material created in Phase I. The proposed Phase II program will refine, optimize, scale-up, and verify that the Non-Eroding Sonic Throat (NEST) material can withstand the extreme DACS environment with a series of ground, laboratory, and hot-fire tests. First, EXO will continue the systems engineering work started in Phase I. The results from the combustion simulations will be used to develop a kinetics model to correlate oxidative erosion. These tools will also be used to perform Computational Fluid Dynamics (CFD) to define the thermomechanical and aerothermal loads on the NEST inserts. Based on the results from Phase I, our fabrication partner will work to develop and simulate advanced, woven preform architectures while also optimizing and develop their processing techniques. Finally, multiple throat inserts will be fabricated for testing. With the fabricated throat inserts, EXO will conduct multiple hot-fire test campaigns. The first campaign will utilize existing Phase I NEST assets. This testing will help provide test data used to build the surface reaction database used for the erosion model. The second phase of testing will incorporate the lessons learned from the first phase and test up to two lbf inserts using a modified reusable motor system. This testing will verify and validate that the NEST HfC material development program can accomplish the primary Phase II technical objective: Provide non-eroding performance for pintles and throat inserts with oxidizing propellants. The inserts will be analyzed after hot-fire using microscopy and other optical diagnostics. Approved for Public Release | 25-MDA-12220 (23 Sep 25)