Staging and trajectory optimization of rockets during conceptual design

Abstract

The conceptual design phase is critical because most of a launch vehicle's life cycle cost is determined during this phase. Therefore, the objective of this thesis is to facilitate the automated generation of rocket concepts. This is achieved by reducing the launch vehicle design problem to the optimization of staging and trajectory. The goal is to maximize the rocket's total payload ratio for a given payload mass and target orbit. The staging characteristics are optimized by extending the classical staging algorithm, which is based on the Tsiolkovsky rocket equation. The new algorithms take velocity losses and fairing separation into account. In addition, they are also applicable to configurations containing boosters and reusable stages. Trajectory optimization is facilitated by providing a trajectory approximation method that generates initial guesses and can also be used to estimate a rocket's payload capacity. A coupled optimization of staging and trajectory for models of Ariane 40 and Falcon Heavy resulted in increases of payload ratio by 12 and 34%, respectively. The methods developed in this work can be used to initialize a more detailed multidisciplinary design optimization.