This paper evaluates an ASD tug’s main control parameters in terms of: the propeller thrust, a direction thereof (the thruster angle), and the hull drift angle for given escort speed and required push force. Such a relation is sometimes referred to as the tug performance diagram. A simplified model of tug hydrodynamics is used to arrive at the qualitative and most representative relations of the above variables. This model is rather generic that can also suit any type of tug hydrodynamics, including even that related to a conventional tug