Initial Guess Generation for Rocket Ascent Trajectory Optimization Using Indirect Methods

An approach for generating an initial guess for a direct optimization method in the field of rocket ascent trajectories is described. An indirect optimization approach is used to calculate a trajectory that neglects atmospheric effects, path constraints, and several other more complicated boundary constraints. Once this trajectory is generated, it is used as an initial guess for a direct optimization method, which includes all atmospheric effects, path, and boundary constraints. The indirect method also generates a switching function, which is used to analyze the nominal mission profile in order to identify possible improvements by adding coast arcs. Such an analysis is presented on an example mission of the European Ariane 5 launcher. For this mission the payload mass can be increased by 66% by adding one additional coast arc. Finally, the flexibility of the direct optimization method allows for various complicated boundary constraints such as dynamic pressure, heat flux, or empty stage splashdown constraints. In the example mission presented, enforcement of those constraints within the direct optimization is demonstrated.