Earth-Moon Transfer Orbits

This work is part of the ESA-project, that wants a preliminary study about the feasibility of building a permanent base on the south pole of the Moon, before July 1st 2020. Moreover after having completed the building phase, the maintenance has to be guaranteed for at least another ten years during the operational phase. The problem is tackled considering only the orbit design point of view. The Space Trajectory Analysis (STA) software has to be used to perform the entire mission, which is a requirement imposed by ESA. Actually this is a thesis group work, that has been split in three different parts, one per student: ascent (since the launch until the parking orbit is reached), transfer (until a lunar parking orbit is obtained) and landing phase. In this thesis the central part is investigated. Since the best transfer orbit has to be found, all the possible options to go from the Earth to the Moon have been studied and analyzed: two-body problem, three-body problem and low-thrust trajectories. Therefore the Lambert’s problem has been tackled by using impulsive manoeuvres and low-accelerations arcs (modelled by the Exposins theory). In both cases a global optimizer has been used to find the best orbit transfer. For these two kinds of trajectories the STA Interplanetary Module and the STA Interplanetary Low-thrust Module have been used respectively. The third option is represented by heteroclinic manifolds trajectories, able to connect the Sun-Earth and the Earth-Moon 3-body systems. To that purpose the STA 3-Body Module has been developed to compute trajectories exploiting this model. Also in this case a global optimizer has been used to get the best solution. In all cases the total ?V has been the objective function. Actually to build a lunar base the most relevant parameter is the payload mass that cab be delivered into a lunar orbit per each launch. The TOF has been strongly considered only for the trajectory design of manned missions, and, in case of similar performance, for cargo missions too. The computations turned out that the Ares V launcher is the only one able to transfer enough mass per launch in order to build the lunar base, and both high-thrust and 3-body trajectories can be selected. Actually 3-body trajectories allow to transfer circa 4 tons more per launch, for this reason they have been widely used for the building phase. Furthermore the Ares V is the only launcher that can accomplish successfully manned missions. In this case only high-thrust trajectories have been considered, since the TOF becomes an important factor to take into account. Low-acceleration trajectories seemed to be well-promising, but a numerical integration of the trajectory (not included in the STA Interplanetary Low-thrust Module) is required in order to better evaluate this kind of orbit. This was outside the scope of this particular study.