Optimization of Active Debris Removal Missions with Multiple Targets

Mission design for multiple debris removal is performed by selecting the most favorable sequences of objects to be removed. Debris items among a population with similar inclination values are considered. The chaser rendezvouses with the objects and attaches a removal kit. An approximate analysis, based on the use of the J2 effect to minimize propellant consumption, provides estimations of transfer times and Delta V between any object pair in order to evaluate the costs of any possible sequence. Estimations, which are verified by using an evolutionary optimization of four-impulse transfers that take J2 perturbation into account, are fast and accurate; and they permit evaluation of all available sequences when the number of objects to be removed is limited. The object sequence determination problem is converted to a traveling salesman problem, and an ant colony optimization algorithm is introduced to analyze longer sequences. The mass of the removal kit for any debris item is then evaluated, depending on the selected removal method. The overall mission mass budget is finally computed, and the best opportunities in terms of the mass and mission time are selected. Different removal techniques exploiting chemical and electric propulsion are compared. The results prove that removal of four to eight objects in less than a year is feasible with current technologies.