  In the framework of the fluctuation-dissipation approach to dynamical
friction, we derive an expression giving the orbital energy exchange
experienced by a compound body as it moves interacting with a non homogeneous
discrete background. The body is assumed to be composed of particles endowed
with a velocity spectrum and with a non homogeneous spatial distribution. The
Chandrasekhar formula is recovered in the limit of a point-like satellite with
zero velocity dispersion and infinite temperature moving through an homogeneous
infinite medium. In this same limit, but dropping the zero satellite velocity
dispersion ($\sigma_S$) condition, the orbital energy loss is found to be
smaller than in the $\sigma_S=0$ case by a factor of up to an order of
magnitude in some situations.
