Attitude control system design for return of the Kistler K1 orbital vehicle

An attitude control system design is presented that provides the maneuver c apability and aerodynamic angle maintenance necessary for the atmospheric r eentry and return to launch site of an unmanned reusable launch vehicle. Th e primary functions are categorized into those that perform bank maneuvers about the air-relative velocity vector and those that are responsible for t he tracking and control of the vehicle aerodynamic trim conditions. The con trol system is supported by an onboard aerodynamic estimation function. The estimator uses measurements of vehicle states from navigation in combinati on with analytic models in a gain-scheduled filter environment to provide c ontrol with current trim angle information, The control system uses this in formation to minimize actual vehicle deviations from the trim. Also, contro l is provided with bank commands from a guidance function. As this paper is concerned only with the control and estimation functions, the guidance str ategies are discussed only to the extent that is necessary to justify/clari fy control or estimator designs, The algorithms developed here are applied to the Kistler K1 Orbital Vehicle and tested in the Kistler Integrated Vehi cle Simulation at Draper Laboratory. Results indicate that the approach to entry/return control is both fuel efficient and effective from a landing ac curacy perspective.