Optimal Range Capabilities for Low-Lift-to-Drag Ratio Mars Entry Vehicles

Abstract

Optimal solutions for maximizing the range of low-lift-to-drag ratio entry vehicles at Mars are explored. Optimal control problems are formulated to consider both vehicles using bank-angle steering as well as alpha-beta steering during entry. Both the maximum downrange and maximum crossrange problems are considered. Results are combined to determine an overall range capability and facilitate comparison to suboptimal constant bank or angle-of-attack and sideslip-angle commands. The resulting optimal control inputs often differ significantly between bank-angle steering and alpha-beta steering vehicles, the latter of which can extend range by lowering drag through sideslip-angle reversals during entry. While control over the in-plane and out-of-plane motion is found to be more decoupled for alpha-beta steering than bank-angle steering, control over the longitudinal and lateral motion is still not completely decoupled for vehicles using alpha-beta steering.