Abstract
In this paper is presented a method for solving the interior ballistics model when is used a charge of propellant grains composed of different energetic materials and obtained through additive manufacturing. Starting from the premise that the burning of these types of propellant grains is carried out in several phases, at different moments of time and using a more vivacious propellants for secondary phases, leads to a good approximation of the ideal ballistic cycle which represents a rapid increase of the pressure up to the maximum value and maintaining it until the entire propellant charge is completely burned.