Effects of Comprehensive Added Masses Modeling on Airship Equations of Motion and Dynamic Stability

The increasing interest in the use of airships for several applications highlighted the need for accurate modeling, simulation and analysis tools of these vehicles’ dynamics. One of the issues to face with when setting up these tools is the handling of the added masses’ phenomenon. This paper presents a method to correctly include added masses in the airship flight dynamics equations without introducing any assumptions in the modeling of the phenomenon, such as simplified airship geometric shape or coincident centers of added mass, usually applied in the literature. It also provides a rule for the computation of the position of the centers of added mass and of the added mass matrix in any coordinate frame, which is required for the accurate writing of the equations of motion, and validates the effectiveness of this rule through a numerical approach based on the boundary element method for a potential flow problem. Finally, the effects of added masses are assessed with reference to a high-altitude airship, by evaluating the dynamic stability and the linearized matrix poles with and without the presence of the added masses.