The model describing the movement of a flying object introduced by Dimitriesky, Lusenko and Bogodistov has been applied to study the spatial movenment of rockets. The model consists of an additional equation system which determines angle direction of flying objects in a coordinate system to calculate force and aerodynamic momentum. However, the additional equation system is unable to be transferred to the variable-separation form
thus to be solved, the equation system must be lineararized and the gradual approximation method must be used. The article introduces an additional equation system which is the same to the above mentioned equationt system but it does not have such weak points. This helps external balistic learners and researchers in programing and calculating.