An optimal control framework is presented that provides an endgame guidance scheme for the exo-atmospheric interception of hostile intercontinental missiles. Therein, a receding horizon optimization strategy is deployed, using a multiple shooting discretization of the dynamic system. The control parameterization is based on a specific endgame heuristic, so that acceleration commands can be approximated by a tangens hyperbolicus formulation to emulate the discrete structure of impulsive thruster acceleration commands. As a result, the number of optimization variables is significantly reduced, potentially enabling closed-loop control schemes. As a closed-loop algorithm, a modified nonlinear model predictive control approach is proposed. Numerical investigations are presented that address the endgame problem in the simplified environment of an interception plane.
Nomenclature= acceleration vector of the kill vehicle = maximum acceleration of the kill vehicle = steepness of the tangens hyperbolicus approximation = correction angle, i.e. the angle between relative position and relative velocity = error compensation term = objective function of the nonlinear optimization problem = multi-dimensional ordinary differential equation for the system's state variables = equality constraint function of the nonlinear optimization problem = inequality constraint function of the nonlinear optimization problem = performance index of the optimal control problem = Lagrange term of the performance index = relative position vector of kill and reentry vehicle = position vector of the kill vehicle = position vector of the reentry vehicle (target) = position of the predicted intercept point (PIP) = control vector of the optimal control problem = relative velocity vector of kill and reentry vehicle = differential system state variables = maneuver angle, i.e. the angle between acceleration and relative position