ESA GNC Conference Papers Repository
New Guidance schemes for the Terminal Area Energy Management of Atmospheric Re-entry
New guidance schemes for the Terminal Area Energy Management (TAEM) of atmospheric re-entry have been developed for both lifting bodies and space planes, with the purpose of improving the overall TAEM and landing performance in terms of energy management and positioning accuracy with respect to existing designs. The proposed TAEM guidance scheme for space planes builds on the Shuttle heritage and addresses its shortcomings by adding an on-board trajectory planning with downrange Heading Alignment Cone control. Trajectory is defined three-dimensionally using mathematically well-defined geometric segments designed to be flown at the vehicles centre-of-capability (maximum robustness to uncertainties) and in quasi-trimmed flight conditions. The path controller features analytical feedforward commands to track the on-board generated trajectory. The proposed guidance scheme for lifting bodies is similar to the supersonic guidance mode of the scheme proposed for the space planes but with a few modifications, namely the inclusion of a homing phase for establishing the proper dynamic conditions for the parafoil deployment while minimizing the distance-to-target, and an optional S-turn phase for increasing the energy management capability. An X-38 like vehicle model and the HL-20 model were implemented and used as templates for the lifting body and space plane configurations respectively. Both guidance schemes were tested extensively via Monte Carlo simulations using a high-fidelity simulator, and considering dispersions at the initial state conditions, vehicle mass and aerodynamic uncertainties, and environment uncertainties (atmospheric density and wind variability). The guidance schemes were first evaluated in 4 DOF simulations. The enhanced guidance scheme for the space plane was benchmarked against the original Space Shuttle strategy and studies were extended to the landing phase (i.e., inclusion of guidance for the initial approach, pre-flare, final approach and final flare), culminating in the evaluation in a 6 DOF high-fidelity simulation tool, in nominal and off-nominal initial state conditions. The simulation campaign for both vehicles confirmed the adequacy of the proposed guidance schemes for the Terminal Area Energy Management of lifting bodies and space planes, showing promising results in terms of both performance and robustness to uncertainties and winds.