New techniques in astrodynamics for moon systems exploration

ESA and NASA scientific missions to the Jupiter and Saturn systems will answer fundamental questions on the habitability of icy worlds. The missions include unprecedented challenges, as the spacecraft will be placed in closed, stable orbits near the surface of the moons. This thesis presents methods to design trajectories that tour the moons and ultimately insert the spacecraft into orbits around them, while mitigating the mission costs and/or risks.;A first technique is the endgame, a sequence of moon flyby preceding the orbit insertion. Historically, the endgame is designed with two approaches with different results: the vinfinity-leveraging transfer (VILT) approach leads to high-Deltav (hundreds of m/s), short time-of-flight (months) endgames, while the multi-body approach leads to low-Deltav (tens of m/s), long time-of-flight (years) endgames. This work analyzes and develops both approaches.;We introduce a fast design method to automatically compute VILT endgames, which were previously designed in an ad-hoc manner. We also derive an important simple quadrature formula for the minimum Deltav attainable with this approach. This formula is the first important result of this work, as it provides a lower bound for assessment studies.;We explain and develop the complex multi-body approach introducing the Tisserand-Poincare (T-P) graph, which is the second important result of this work. It provides a link between the two approaches, and shows the intersections between low-energy trajectories around different moons. With the T-P graph we design a five-month transfer between low-altitude orbits at Europa and Ganymede, using almost half the Deltav of the Hohmann transfer.;We then focus on missions to low-mass moons, like Enceladus. We show that nontangent VILT (an extension of the traditional VILT) significantly reduce the Deltav while maintaining a satisfactory transfer time (< 4 years in the Saturn system). With a new design method we compute a 52 gravity-assist trajectory from Titan to Enceladus. The time of flight is 2.7 years, and the Deltav is almost 10 times better then the Titan-Enceladus Hohmann-like transfer. This trajectory and the design method are the third important contribution of this work; they enable a new class of missions which were previously considered unfeasible.;Finally we study the capture problem, which seeks chaotic trajectories with multiple orbit insertion opportunities. We explore the solution space extending the design techniques used by ESA for the BepiColombo mission capture to Mercury. Such problems are better modeled in the spatial, elliptic, restricted three-body problem, which we analyze in detail. We define new regions of motions and to compute new families of periodic orbits and their stability properties. This analysis is the fourth important contribution of this work. Finally we show that capture trajectories shadow the manifolds of special periodic and quasi periodic orbits. This is the last important contribution of this report, as if both explains the complex dynamics of capture trajectories, and suggests new ways to design them.