ABSTRACT The design of man‐portable, shoulder‐fired rocket systems necessitates a delicate balance between manufacturing safety and controlled internal ballistics stability to ensure operator protection. This study quantitatively evaluates the influence of varying Dibutyl Phthalate (DBP) concentrations (0%–8% wt.) on the rheological processing and combustion characteristics of modified double‐base (MDB) propellants. Rheological characterization using a Brabender Plasti‐Corder revealed that the absence of DBP (0%) resulted in a high‐viscosity melt with an equilibrium torque ( T e ) of 38.4 Nm and a significant viscous heating rise (∆ T ) of 14.2 ° C, posing substantial risks of thermal runaway during extrusion. The introduction of 8% DBP reduced these values by 60%, yielding a T e of 15.5 Nm and mitigating processing risks with a temperature rise of only 3.4°C. Ballistic characterization through Small‐Scale Test Motor (SSTM) firings revealed that the 0% DBP formulation produced hazardous, regressive pressure‐time profiles with peak chamber pressures ( P max ) reaching 47 MPa. Mechanistic analysis suggests DBP acts as both a thermal coolant and chemical deterrent; by diluting reactive intermediates in the Fizz Zone and expanding the Dark Zone induction period, DBP increases the flame stand‐off distance to decouple high‐intensity heat feedback from the propellant surface. This mechanism facilitates a stable plateau burning regime ( n ∼ 0.12) at a 6% DBP concentration. Although the overall specific impulse ( I sp ) decreased from 247 to 204 s, the 6% DBP batch optimized the trade‐off, providing a 50% improvement in processability and a safe 37 MPa pressure profile while maintaining a tactical I sp of 225 s.
Fahd et al. (Fri,) studied this question.