Analysis of low-thrust interplanetary missions

The planets of our Solar System move in a complex way around the Sun, and this causes the performances of any interplanetary spacecraft to be dependent on the launch opportunity and, once the latter has been chosen, on the exact launch date. The precision required in the computation of the spacecraft trajectory is such that the approximation obtained assuming that the planets move along circular and even elliptical orbits is not sufficient for the analysis of an interplanetary mission, and the knowledge of detailed ephemerides is required. In case of high-thrust mission, the well-known pork-chop plots are effective tools to design interplanetary missions, providing a graphical overview of the relationship between the fundamental parameters of the mission design: the launch date, the duration and the energy requirements. If low-thrust missions are considered, a graphical tool similar to the pork-chop plot but suitable for electric propulsion systems is here introduced. Such tool is called J-plot and it can be computed by using different types of optimization techniques (i.e., direct or indirect methods or evolutionary approach). An open-source software named IRMA (InteRplanetary Mission Analysis) for the preliminary design of interplanetary missions is presented. Several choices can be made regarding the type of propulsion system (chemical or electric), the actual capability of the thruster, the desired optimization procedure and the type of departure and arrival orbits (circular or elliptical). The computation can be performed considering a specific launch opportunity (in this case the J-plot is provided) or a precise launch date. If solar electric propulsion is considered, a more detailed analysis can be carried out taking into account the shadow effect on the overall performances of the thruster. Moreover, part of this work focused on the study of possible scenarios for human missions to Mars based on the existing technologies.