The aim of this work is to develop a new and robust numerical calculation program to determine the trajectory of supersonic earth-to-earth missiles based on 17 different physical parameters; 6 of which are related to the supersonic nozzle design, and the remaining 11 are related to various missile design physical parameters itself. The calculation includes the effect of nozzle friction and effect of aerodynamics external pressure and viscous drag. The trajectory is modeled by solving a system of four ordinary first order differential equations with initial conditions combined with analytical equation, whose unknowns are (x, y, u, v and ¿). The resolution is done numerically by using the sixth order Runge Kutta method. The execution of the elaborate numerical program stops when a point (x, y) of the trajectory is found whose ordinate will be equal to zero. This result means that the missile has returned to the earth after launching from earth point and reaching a maximum altitude. The results are limited by the determination of the missile range, the maximum missile altitude, and the complete mission time.