A versatile computer program is coded, using MATLAB (SIMULINK), to compute the trajectory elements of the rocket assisted projectiles (range flight velocity and inclination angle). The inputs of the code, are the projectile parameters (mass, caliber, muzzle velocity, drag coefficient and firing angle) and the assisting rocket parameters (mass, time of function, delay time and propellant specific impulse). The code is used to study different design factors affecting the range of the rocket assisted projectiles. It is found that the range can be significantly extended by using an assisting rocket. The range extension increases by using greater propellant mass, smaller delay time and smaller time of function. The angle of the maximum range is a function of the propellant to total projectile mass ratio. In the investigated case, this angle does not depend on the delay time or the time of function.