Stability of a towed body

This paper presents a mathematical model for the efficient computation of the stability of bodies subject to fluid-dynamic forces while constrained by a flexible, extensible cable. The way the cable is represented permits the body to be heavier or lighter than air and to have a steady-state lift. The model is applied to the case of a pendant vehicle towed by a cable attached to an aircraft, a case of considerable practical interest. It is shown that inherent instabilities are present and that they can be eliminated by the correct method of fable attachment. The paper emphasizes the physics of the system and the reasons for the instabilities.