Optimization of Circularly Towed Cable System in Crosswind

Abstract

The dynamics of aerial tethers towed in circular paths by an orbiting aircraft have been studied extensively. Typically, the atmosphere is assumed to be stationary with respect to the ground so that stable steady-state solutions are possible for certain combinations of system parameters. This paper presents a numerical approach for minimizing the disturbance of a crosswind on the periodic solution of the cable tip using a combination of towpoint manipulation and tether reeling. A discrete lumped parameter cable representation is used to simulate the physics of the cable system. Periodic solutions are generated for a range of towpoint motions including elliptical orbits. The required angular velocity of the aircraft to maintain constant airspeed is derived. Numerical results show that steady-state wind effects can be compensated for by flying the aircraft in an elliptical orbit upwind of the target point in combination with reeling the cable or flying on an inclined orbit.