Conceptual Design and Optimization of a Scramjet with Ablative Thermal Protection

The design of supersonic-combustion ramjet (scramjet) engines requires approaches that account for both the system performance and the complex interactions of the engine components. At the system level, the propulsor must meet the inherent performance needs such as specific-impulse (I_sp) or propulsion efficiency (\eta_p) for a given vehicle geometry and flight trajectory. Simultaneously, each subsystem--including the inlet, combustor, and nozzle--must operate efficiently to contribute to the system-level behavior while each adhering to its own physical and operational constraints. Thermal management is a critical aspect of the engine, that we particularly address by introducing novel ablative materials used as thermal protection systems (TPS), capable of withstanding the extreme heat loads typical of supersonic combustion. This work presents the development and coupling of reduced models that balance fidelity with computational efficiency for early-stage design and eventual multidisciplinary design optimization (MDO) of scramjets. The proposed models predict critical failure modes such as unstart and thermal overload. In particular, we implement quasi-one-dimensional models to characterize the gas thermodynamics along the engine flowpath, coupled with a low-dimensional unsteady model of gas-wall interactions in the combustor to evaluate the ablative materials performance. The model reproduces key propulsion and material performance parameters to support the analysis of trade-offs for design and it provides a foundation for optimizing scramjets due to its modularity and moderate accuracy.