BPI = Boost Phase Intercept

The paper presents a near-optimal guidance law that has been developed using the direct method of calculus of variations. By the direct access to controlling the shape of the trajectory, this guidance law seeks to maximize the kinetic energy transfer upon interception from a surface launched medium range interceptor missile to a ballistic missile target during the boost phase of flight. Mathematical models of a two-stage liquid-fueled medium-range ballistic missile and a velocity-limited endo-atmospheric interceptor missile with onboard active radar guidance are used to demonstrate the guidance law’s performance. This law will utilize the interceptor's onboard computer and active radar sensors to independently predict an intercept point, solve the two-point boundary-value problem, and determine the best feasible flight path to that point. While determining a truly optimal flight path would require significant computing power and therefore cannot be realized online, the proposed near-optimal flight path can be calculated onboard the interceptor in fractions of a second and updated in multiple times during the intercept without significant technological advancements in the interceptor’s onboard hardware. That near-optimal guidance path is then converted into a set of command functions and fed back into the control system of the interceptor. By modifying just a few parameters affecting the higher-order derivatives at the intercept point, the optimization algorithm varies th