Creation of an Upper Stage Trajectory Capability Boundary to Enable Booster System Trade Space Exploration

Multidisciplinary design optimization is a complex process requiring many iterations of a high fidelity analysis environment to reach an optimum design. Launch vehicle design complicates this process by requiring inner optimization loops necessary for trajectory simulation. Multi-stage vehicles add complexity to this analysis process as changes in vehicle properties in one stage propagate to the other stages and change the optimal trajectory. These effects can cause an increase in analysis time as more variables are added and convergence of the optimizer to system closure requires more analysis iterations. An approach to simplifying this multi-stage problem though the creation of an upper stage capability boundary is presented. With application to trade space exploration for the advanced booster system of NASA’s new Space Launch System (SLS), the approach developed leverages surrogate modeling techniques to create a predictive model of the SLS upper stage performance. Through the creation of a surrogate model, which takes staging conditions as inputs and predicts payload mass delivered to orbit by the SLS upper stage as the response, a “surface” of staging conditions is identified which all satisfy the SLS requirement of placing 130 metric tons into low Earth orbit (LEO). With the surrogate model created, design and analysis of advanced booster concepts is streamlined, as optimization of the upper stage trajectory is no longer required in every design loop.