An attitude stabilization approach integrated of passive and active scenarios for on-orbit refueling considering liquid transfer

Servicer spacecraft supply fuel to a client via on-orbit refueling technology, which can extend the lifespan of the client. However, during refueling, the inertia of the combined spacecraft varies continuously due to the liquid fuel flow, which risks disrupting the attitude motion. To guarantee the attitude stabilization of the combined spacecraft in various on-orbit refueling mission scenarios, an attitude stabilization approach integrated of a passive scenario for conditional self-stability and an active scenario for the non-self-stable case is presented in this paper. The passive stabilization criteria are proposed via analyzing the long-term effect of the gravity gradient. For missions in which the criteria are not satisfied, an active control strategy structured by the dynamic pole assignment controller and the uncertainty estimator is activated. The dynamic pole assignment controller ensures the stability of attitude under the influence of refueling disturbance based on refueling pressure measurement, and the uncertainty estimator compensates for the uncertain inertia parameters by measuring the angular velocity. Numerical examples are provided to demonstrate the effectiveness of the attitude stabilization approach.