This model for the rocket motor was developed by Probert, Williams and Tanasawa. It is reasonable to neglect Q j , Γ Γ j , for distances not very close to the spray atomizer, where major portion of combustion occurs. Consider a one-dimensional liquid-propellent rocket motor situated at x = 0 , where fuel is sprayed. Neglecting E j (density function is defined without the temperature so accordingly dimensions of f j changes) and due to the fact that the mean flow is parallel to x axis, the steady spray equation reduces to