Optimal Design of Hybrid Rocket Motors for Launchers Upper Stages

摘要

A hybrid rocket is considered as the third stage of a three-stage launcher. The design of the hybrid rocket motornand the trajectory are simultaneously optimized by means of a nested direct/indirect procedure. Direct optimizationnof the parameters that affect the motor design is coupled with indirect trajectory optimization to maximize thenlauncher payload for assigned characteristics of the first and second solid-propellant stages and final orbit.Amissionnprofile based on the Vega launcher is considered. The feed system exploits a pressurizing gas, namely, helium, withnhydrogen peroxide as the oxidizer and polyethylene as the fuel. The simplest blowdown design is compared with anmore complex pressurizing system, which has an additional gas tank that allows for a phase with constant oxidizerntank pressure. The optimization provides the optimal values of the main engine design parameters (pressurizing gasnmass, nozzle expansion ratio, and initial values of tank pressure, mixture ratio, and thrust), the corresponding grainnand engine geometry, and the control law (thrust direction during the ascent trajectory and engine switching times).nResults show that a hybrid rocket may be a viable option for small launchers.