Enhancements to Space Shuttle Powered Explicit Guidance for Planetary Ascent and Descent

A number of enhancements to Space Shuttle Powered Explicit Guidance (PEG) algorithm are developed in this work that increases its validity and accuracy for various planetary ascent and descent trajectory problems. The specific PEG enhancements studied in this work include precise targeting of the line-of-apsides for elliptical orbit insertion, range and burn ignition time control for precision landing, and compensation for atmospheric drag. Additionally, a new general predictor-corrector formulation of PEG is presented that can compute effects due to any arbitrary force model on the guided trajectory by using numerical quadrature. Two different simulations for lunar and Mars descent and ascent vehicles are implemented to validate these PEG modifications.