Design of an optimization tool for Contamination and Collision Avoidance Manoeuvre of Vega-C launcher

The Contamination and Collision Avoidance Manoeuvre (CCAM) is the flight phase of Vega-C missions directly after the Payload (PL) release, critical for the insurance of the integrity of the released PL. Its main objectives are to avoid the collision of the upper stage with the separated PL in a mid and long-term and to minimize the pollution of the PL by the plume of the launcher’s motors (Main Engine and ACS Attitude Control System thrusters). Several aspects of the PL separation greatly affect this manoeuvre, above all the launch vehicle’s attitude, PL release direction and the separation mechanism. These aspects, together with specific PL requirements and the possibility of multiple releases on the same orbit, make high variability one of the main characteristics of this flight phase, forcing the mission designer to look for an efficient solution in a custom-made way and making this missionization process highly time-consuming. This work is aimed at presenting a new tool for speeding up the missionization process and for making it more efficient. The core of this tool is an open-loop simulator simplified with ad hoc models of the fourth stage of the Vega-C launcher and able to perform Monte Carlo-like campaigns that randomly generate a significant number of manoeuvres that are evaluated and fed to an evolutionary algorithm (Differential Evolution) for the research of one or more optimal solutions. After requesting a set of user-defined inputs and constraints, the tool integrates Hill’s equations to simulate the PL trajectory in a local orbital frame, while the attitude of the launcher is computed through quaternion integration. The evaluation of the manoeuvres is based on the requirements of collision and contamination avoidance defined in a cost function. Once generated, the manoeuvres can be plotted and compared with each other. Furthermore, the user can save both inputs and outputs as well as the mission data to be used in the main simulator. Among other features, the tool can simulate multiple PL separations, both simultaneous and sequential, leaving to the user the freedom to define each release independently from the others.