Endgame Guidance Law Design And Analysis Of Deep Space Impact Exploration

Endgame guidance is one of the key technologies of asteroid impact mission. Based on systematic review of the endgame and midcourse guidance strategy of tactical and strategic missiles and guidance law of exploration mission of small bodies, several suitable endgame guidance strategies are designed according to the specific constraint. The main contents of this dissertation are as follows:First, several coordinates and dynamic equation of the approach stage which would be used in the following guidance law design are developed.Then, based on the parameters offered by navigation system, according to the requirement of zero Zero-Effort-Miss, if the impactor hits the target asteroid directly, an endgame guidance law is presented. And taking the impulse trajectory thrustors into account, an on-and-off command curve is developed in association with error ellipse of navigation system. The simulation results show that this guidance law works well.Third, based on the characteristics of impact asteroid mission and take advantages of proportional guidance which basically is based on control sight-line rate to zero, an endgame strategy is established, which also take Zero-Effort-Miss into account in order to get a better precision. In this guidance method, we again establish an on-and-off condition of divert firings. Results indicate the validity of this strategy.In addition, guidance law of predicting finally impact position is studied and which is applied in the deep space kinetic impact mission. According to the dynamic and kinematics equation of impactor, the guidance thrust can be easily derived to satisfy hitting directly. Two form predictive, impulse guidance laws are presented. To one strategy, the time of correcting trajectory is fixed, while in another form, the time of divert firing is according to the ZEM magnitude. The results show that the latter can serve an better precision and consume less fuel.Finally, taking the predictive fixed time guidance law as an example,analyze the influence of the bias of subsystem to the guidance law.