A re-entry guidance method for vehicle using virtual displacement concept

A new guidance law for reentry vehicle is presented in this paper. The proposed approach is based on the fact that lateral force is formed in a plane which is perpendicular to the reentry vehicle velocity. Particularly, the nominal impact point is defined as the impact point generated by zero lift trajectory. The virtual displacement is defined as the tiny change of the nominal impact point, which is caused by any instantaneous lateral force at the beginning of the trajectory. The optimal direction of the lateral force is obtained by the solution of optimal virtual displacement, in which the optimal virtual displacement should point to the target. The analytical solution of reentry trajectory and the linear quadratic gauss (LQG) method are used to design this guidance law. The simulation results demonstrate the effectiveness of the proposed method.