Constrained Predictor-Corrector Entry Guidance

A fully constrained predictor-corrector entry guidance algorithm for horizontal landing X-33 vehicles is investigated. The quasi-equilibrium-glide condition (QEGC), a zeroth-order solution in an asymptotic expansion of the trajectory about a equilibrium-glide path, is used in entry flight mechanics. The three-degree-of-freedom dynamics for an entry vehicle over a spherical rotating Earth are described by dimensionless equations of motion. The bank-angle histories reveal that for missions with small cross-ranges, the guidance algorithm commands two bank reversals. The impact of these significant dispersions can be seen from the wide spread of the terminal area energy management (TAEM) velocity azimuth angle in a range of 40 deg, which indicates very different ground tracks near the TAEM interface, due to the large dispersions.