Improving lunar return entry range capability using enhanced skip trajectory guidance

The impending development of NASA's Orion crew exploration vehicle will require a new entry guidance algorithm that provides sufficient performance to meet all requirements. This study examined the effects on entry footprints of enhancing the skip trajectory entry guidance used in the Apollo program. The skip trajectory entry guidance was modified to include a numerical predictor-corrector phase during the atmospheric skip portion of the entry trajectory. A 4-degree-of-freedom simulation was used to determine the range capability of the entry vehicle for the baseline Apollo entry guidance and the predictor-corrector enhanced guidance with both high and low lofting at several lunar return entry conditions. The results show that the predictor-corrector guidance modification significantly improves the entry range capability of the crew exploration vehicle for the lunar return mission. The performance provided by the enhanced algorithm is likely to meet the entry range requirements for the crew exploration vehicle.