Hybrid Roc. Analysis (Chemical Equilibrium Analysis is used inside the combustion chamber) Flow is proceeded inside a convergent divergent nozzle and the outputs of the study is to determine the variation of the pressure inside the engine with time also to determine the variation of the Mach number at the exit of the nozzle as the rocket engine life time decay (As traveled in the atmosphere- max. Range 3 Km, max. Height 900 m, Max. Mach number of the travelling engine is 0.78)