Optimization methodology for ascent trajectories of lifting-body reusable launchers

A simulation and optimization methodology, created by the authors to optimize the trajectories of airbreathing spaceplanes and already tested and validated, has been improved and applied to a new concept of single-stage-to-orbit lifting-body spaceplane in order to search for optimal ascent trajectories for a typical mission profile. After a brief discussion on preliminary assumptions concerning the available data set, we first present the analysis procedure and the calculation method, which allowed us to simulate the ascent trajectory of a single-stage spaceplane model, able to connect the Earth-launch pad to the International Space Station. The optimization technique, belonging to the class of direct optimization methods and dealing with a wide number of independent parameters, is then described in detail, and specific results ensuring a better payload/liftoff weight ratio are widely shown. Shape and size of the vehicle as well as integrated propulsion system and weight distribution are derived from a complete data set, whereas the aerodynamic performances have been directly generated via a Navier-Stokes code. Finally, a sensitivity analysis by varying launch-pad location and final orbit inclination and altitude has been performed, and the influence of each guidance and control parameter on the optimal ascent trajectory has been emphasized.