# Astrodynamics/Interplanetary Trajectories

Since the 1960's, unmanned spacecraft have been sent to planetary bodies outside of the Earth-moon system. These missions present unique problems in astrodynamics.

## Patched Conic Approximation

editThe patched conic approximation is a method used to simplify trajectory calculations by assigning each body their own "sphere of influence". When an object is inside the sphere of influence of a bigger body, only the gravitational force between the object and the bigger body is accounted for. This simplifies a complex n-body problem into a bunch of much simpler two-body problems, whose solutions are the simple conic sections of kepler orbits.

While this approximation can be useful for things like interplanetary trajectories, it fails to model things like lagrangian points.