Lunar return entry guidance based on virtual landing point strategy

An adaptive skip entry guidance algorithm for vehicles with low lift-to-drag ratios is presented. The algorithm is based on the Apollo entry guidance algorithm and upgraded by using numeric predictor-corrector in planning and modulating the linear parameterized bank angle profile. Based on the virtual landing point strategy, a simple and effective bias targeting feed forward procedure is developed for precision landing in large entry range case. The upgraded algorithm is tested against various entry scenarios including perturbations in initial entry conditions as well as extensive dispersion in vehicle mass, aerodynamic properties, and atmospheric density. The algorithm is shown to be sufficiently robust and general enough to allow precision landing with a delivery error of less than 3 km in the entire range between 3000 km and 10000 km.