A cooling system using one or more heat pipes rotating about a central axis to transfer heat energy from one medium to another. The heat pipes are oriented within a rotating member such that the axis of the heat pipe is non-coaxial with that of a central axis of the rotating member. Centrifugal forces are used to assist the movement of the working fluid within the heat pipe. The cooling system also includes heat pipes associated with a planetary carrier assembly and supplemental heat exchangers for use in aircraft and other machinery.