This package provides the interface for force models that will be used by the
{@link org.orekit.propagation.numerical.NumericalPropagator} and the
{@link org.orekit.propagation.numerical.NumericalPropagatorWithJacobians}, as well as
some classical spacecraft models for surface forces (spherical, box and solar array ...).
@author Luc Maisonobe
@author Pascal Parraud