Attitude dynamics of coupled spacecraft undergoing fuel transfer

This paper represents an explicit analytical solution for attitude dynamics of spacecraft combination during on-orbit refueling. Due to the fuel transfer from the servicer to the client, the inertia tensor of the spacecraft combination varies in time, which evidently leads to an inner disturbance torque on the attitude motion. Firstly, the variation of the inertia tensor matrix is formulated in terms of fuel transfer rate, and the refueling disturbance torque associated with the variation of inertia tensor is analyzed. Secondly, with an additional consideration of the effect from gravity gradient, the behavior of attitude dynamics during and after fuel transfer is investigated. Finally, different scenarios are simulated to demonstrate the efficiency of the proposed model. The result in this work is important and allows for evaluations on the attitude disturbance and stability for an on-orbit refueling mission.