Interplanetary Travel: Impulsive Approximation

Chemical rockets, and also nuclear thermal rockets, supply large thrusts for a short time: the simplest way to compute the trajectories which can be obtained using this type of propulsion is the so-called “patched conics approximation”, in which propulsive phases, reduced to instant changes of velocity, are alternated to phases in which the spacecraft proceeds under the effect of the gravitational attraction of the solar system bodies. Assuming that only one celestial body acts at a time, these coasting arches are conic sections. Idealized solutions obtained by assuming that planetary orbits are circular and coplanar, are first described; while more realistic solutions in which the departure and arrival planets follow elliptical and non-coplanar orbits, are then considered.