The course will be devoted to the analysis and modelling of solid rocket motors and the complex phenomenology that characterizes these propulsion systems. Theoretical and mathematical models will be provided for analyzing the operation and performance in the quasi-steady regime with both zero-dimensional and one-dimensional approaches. Combustion of energetic materials will be analyzed with attention to the various solid propellant formulations. Specific aspects such as ablation phenomena of thermal protection materials in the nozzle, two-phase flow phenomena, grain geometry and burn-back analysis, as well as ignition transient, will be analyzed in detail. Hints on hybrid rocket propulsion systems and their main characteristics will be given. Finally, attention is given to recent efforts devoted to developing solid propellants using green oxidizers, which demonstrate less hazards and environmentally friendly chlorine free combustion products.