The purpose of this thesis is to describe and analyze a particular evasion maneuver with double lunar gravity assist (LGA) for interplanetary missions. Lunar flybys are a means to free increase the hyperbolic escape energy (C3) of an escape maneuver for a modest increase in flight time. Two approaches are applied: 1) the first one is the approximate analytical approach; 2) the second one gives the exact numerical solutions, because it takes into account all the main perturbations. The approximate model, it is easier than the other because is based on simplifying as- sumptions such as: no gravitational influence of Sun and Moon on the spacecraft, no solar radiation pressure, no eccentricity of Moon’s orbit (i.e.