Study on stage optimization and PIP prediction of anti-ballistic missiles considering midcourse guidance

Abstract

This dissertation deals with a stage optimization and a calculation of predicted intercept point of anti-ballistic missiles. Conceptually, stage optimization is a two-loop optimization problem for which the inner loop determines control inputs for trajectory optimization while the outer loop minimizes the stage weights. In practice, the optimal control inputs are replaced by guidance commands produced by some practical guidance laws, resulting in some degradation of the system performance. In this paper, stage optimization considering practical guidance laws for the launch and mid-course guidance phases is proposed to precisely assess the stage weights required for the mission. Guidance parameters, virtual target positions, coasting time, and the stage weights are defined as the objective parameters of stage optimization, and the co-evolutionary optimization method is used to find the optimal solution. Applying the proposed method to the stage optimization of a realistic anti-air missile system demonstrates that the missile system needs an extra weight compared to the classical two-loop optimization, to meet the same system requirements. But the difference is less than five percent. This paper also deals with the calculation of predicted intercept point for ballistic missile interception. Above all, various methods are summarized to estimate the trajectory of ballistic missiles and anti-ballistic missiles. Then, time-to-go estimation method is described. By using them, a method for updating the predicted intercept point at the current time is suggested. Based on a virtual target approach suggested in the stage optimization method, the altitude and collision angle of the missile, which are the guidance parameters, are stored for various PIP candidates. The guidance commands are generated by interpolating the values for the changed PIP. To verify the proposed method, simulation studies are conducted and prevail that the ZEM at the end of flight is reduced to a sufficiently correctable level.