Applications of gravity assists in the bicircular and bielliptic restricted four-body problem

We explore two ways of gravity assists concerning three-body energy and twobody energy in the planar restricted four-body problem. The first is concerned with changing dynamical objects of the restricted three-body problem such as energy of orbits and energetically forbidden region via gravity assists within the framework of the restricted four-body problem. As an application, we propose a method of finding nominal transfer trajectories between Lyapunov orbits of different energies without fuel consumption. The second is concerned with revealing time-dependent analogues of invariant manifolds of resonant orbits directly in the restricted four-body problem. For this purpose, we employ the method of Lagrangian coherent structures as a visual aid. We then identify homoclinic and heteroclinic connections of resonant orbits in the restricted four-body problem, which could be applicable to the low-energy exploration of the moons of Jupiter.