Theory Of Predictive Guidance With Application To Reentry And Exoatmospheric Interception

It is well-known that the performance of the guidance law plays an important role in the modern space applications. This dissertation proposed a practical study on the predictive guidance law in the application of the exo-atmospheric interception as well as the reentry guidance engagements, and the main contribution of this dissertation is devote to avoiding the computational burden involved in the practical predictive guidance problem.Firstly, the theory of predictive guidance is introduced. Moreover, the predictive guidance scheme is theoretically shown to be an optimal solution to the interception problem. Also, the proportional navigation is a particular form of the predictive guidance law. Furthermore, simulation results show that the predictive guidance law has the tremendous advantages in saving fuel consumption as well as improving the guidance performance. However, from the point of implementation, the predictive guidance requires real time determination of the actual functions through integrating the actual nonlinear vehicle state equations forward, which involves huge computational burden, and how to avoid this is the main focus in this dissertation. Finding rapid and analytical solution to the calculation of zero effort miss (ZEM) has helped to improve the calculation speed of the predictive guidance law. For the exo-atmospheric short range interception engagement, the difference of gravity for interceptor and target is predigested equal to the orbital angular speed, and a new analytical expression of ZEM is derived, because the difference of gravity for interceptor and target is taken into account in this case, so the expression has a better fidelity than the case where the gravitational accelerations acting upon both vehicles are assumed to be equal. For the exo-atmospheric long-range interception engagement, Newman's linearized inverse square gravity model is modified in this case, and the obtained rapid expression of ZEM has higher accuracy than others since small items with long-term impact is considered in this matter, the influence of navigation errors on predictive accuracy of ZEM are also analyzed in the Monte Carlo sense.For the development of exo-atmospheric midcourse guidance law, an optimal midcourse guidance law is introduced and analyzed. For long-range targeting applications with significant ballistic coasting after burnout, the difference between the gravitational accelerations must be taken account. In this dissertation, a near-optimal midcourse guidance law is presented, which has higher guidance accuracy than the optimal guidance law. Especially, with the introduction of the residual acceleration, it improves the guidance performance, and does not increase the computer's computational burden as well. Moreover, shot-range and long-range interceptions are performed in simulations.One of the important contributions of this dissertation is the development of guidance law for Kinetic Kill Vehicle (KKV) which is released by the exoatmospheric interceptor. With the purpose of eliminating the predicted ZEM, and in accordance with KKV structural characteristics and detection of target features as well, a guidance law for KKV is presented in this dissertation. Moreover, the thrusters with variable thrust by Pulse-Width Modulated (PWM) technique are examined and applied to the numerical simulations of intercepting a non-maneuvering target and a maneuvering target. The results show that the proposed guidance law achieves the purpose of hit-to-kill.A predictive guidance method for reentry vehicle in the case of attacking the stationary target on the surface is also investigated. The classical Gauss equation as well as the two-point boundary value problem (TPBVP) is introduced so as to improve the performance provided by the conventional nominal trajectory guidance method and the existing predictive guidance scheme. In particular, the Gauss equation is introduced to provide a rapid algorithm for predicting the trajectory of the vehicle, the TPBVP is utilized to compute the minimal corrections of the velocities for the reentry vehicle. Furthermore, a predictive guidance algorithm is presented in order to control the vehicle by adjusting its attitude. The Monte-Carlo simulation results indicate that the presented algorithm is robust to atmospheric disturbances.