Attitude dynamics model of on-orbit refueling spacecrafts

Because the spacecraft moment-of-inertia changes obviously during the on-orbit propellant refueling process, this paper provides a detailed analysis of the change of moment-of-inertia. Based on some reasonable assumptions, the paper proposes an effective algorithm for computing the moment-of-inertia. Including only one variable, the propellant flow velocity, the proposed algorithm can compute the moment-of-inertia on-line. As a natural result, the time-varying attitude dynamic model for the on-orbit refueling spacecraft is established. Finally, the numerical simulation illustrates the algorithm correctness and the effect of the spacecraft related parameters on the moment-of-inertia. This result provides theoretical foundations for attitude control system design of on-orbit refueling spacecrafts.