Mass Budgeting for Hybrid Rocket Engines Optimization

Abstract This Thesis work focuses on the optimization of engine design and trajectory for Hybrid Rocket Engines (HREs). In particular, the optimal choices of tank geometry and material are analyzed. HREs are well suited for many applications, among which small satellite launchers are here considered. In this Thesis work, each stage of a three-stage launcher is equipped with the same hybrid rocket engines, organized in different numbers: six, three, and one respectively in the first, second and third stage, in order to minimize the costs by means of a high system commonality. A simple blow-down feed system and an airborne launch are taken into account. First, the optimization process compares the launcher performance for several engine geometries and materials, to find out the best couple aiming at the maximization of the payload mass for a reference engine design point. In this way, a kind of Database is created to group these several scenarios and, through a comparison of them, the best match is selected. At this point, the real optimization process begins: the optimization procedure fixes one by one the couple of geometry-material and optimizes the engine design by adjusting the design parameters, which are the initial mixture ratio and the initial pressurizing gas volume in this application. A direct method optimizes the engine design, while an indirect procedure evaluates and optimizes the corresponding ascent trajectory. Once this process is completed for all geometry-material couples, a new database is created and the optimal couple is found, together with the corresponding optimal engine design and trajectory. The information collected in the databases could be useful in future works on the same or analogous topic to lead an early design phase, because of the functional relationship established between geometries, materials and engine designs.