Tuning the pressure exponent for adaptive solid rocket motors via molecular perovskite energetic materials: a comparative evaluation of DAP-4 and HMX-based propellant

Conventional nitramine energetic ingredients (e.g., HMX) suffer from complex tuning methods and limited effectiveness in regulating the high-pressure exponent of solid propellants. In this study, the molecular perovskite energetic material DAP-4 was employed to achieve a stepwise enhancement of the pressure exponent through systematic comparison with HMX‑based propellants and formulation optimization. Thermal analysis and combustion performance tests reveal that, compared with the HMX system, DAP‑4 exhibits stronger reactivity with AP, reducing the reaction interval by 40% relative to pure AP and significantly lowering the activation energy of thermal decomposition. Combustion performance data show that HMX‑based propellants exhibit a pressure exponent below 0.39 within 1–7 MPa with a mild burning rate. In contrast, the DAP‑4‑based propellant achieves a pressure exponent as high as 0.96 in the range of 1–3 MPa and maintains 0.93 in the 5–9 MPa range, demonstrating a remarkable stepwise increase in pressure exponent over a broad pressure range. A wide tunability of the pressure exponent is realized simply by adjusting the DAP‑4 content, an effect that the HMX system cannot attain. This study provides a new material choice and theoretical basis for the development of high‑pressure‑exponent propellants.