The invention discloses a free trajectory construction method with a specified launching
elevation angle. The method comprises the steps of firstly, orderly calculating the earth-fixed rectangular coordinate vectors of a launching point and a target point, the difference between the earth
latitude and the geocentric
latitude, a horizontal included angle and the difference between the ratio of geocentric radial
modes of the point A and the point B and 1; solving the variables, such as the launching speed of a forward trajectory or a reverse trajectory in an
orbit coordinate
system, the launching speed of the forward trajectory or the reverse trajectory in an earth-fixed coordinate
system, the number sigma of trajectories / orbits,
flight time and the like in the iterative initial state and the two-body motion model, wherein the newly solved
flight time is T *; enabling T to be equal to T *, repeatedly iteratively calculating the launching speed of the
missile and the like, ending iteration until the absolute value of (T-T *) is smaller than a set threshold St, finally obtaining the launching speed and
flight time T of the
missile under the two-body motion model, and outputting the design parameters vp, vr, T and sigma. According to the present invention, the forward trajectory and the reverse trajectory can be constructed at the specified launching elevation angles under a two-body motion model and a
kinetic model considering the J2 perturbation of an earth
gravitational field respectively, and then all trajectories from the launching points to the target points are obtained by traversing the launching elevation angles.