EQUIVALENT DYNAMICS MODELING AND ANALYSIS OF LIQUID-FILLED SPACECRAFT WITH FUEL CONSUMPTION 1)

The liquid in the tank of in-orbit spacecraft may experiences different types of motion, mainly including the overall rigid motion of liquid respect to the tank, the lateral sloshing of the liquid free surface, and the liquid rotation starting which will maybe eventually graduate into the rotary sloshing of the liquid free surface and/or the spinning motion of liquid, etc. The composite 3DOF-rigid-pendulum sloshing model is able to describe all of these main motion types of liquid, and it has been validated to be effective for the analysis of the liquid sloshing dynamics during the rotation-starting period. In this paper, the composite rigid-pendulum model is developed to investigate the large motion coupling dynamics of a variable-mass liquid-filled spacecraft with nonlinear liquid slosh and fuel consumption, by taking account of the variation of equivalent model parameters over liquid-fill ratio. Based on the Lagrangian equations, the orbital-attitude-slosh coupling dynamics model of a liquid-filled spacecraft is equivalently established by using the composite rigid-pendulum model to replace the liquid in a spherical tank. Then, simulations of a three-axis stabilized large angle attitude maneuver and a zero-impulse orbital maneuver of spacecraft are given for the coupling dynamics response analysis of the liquid-filled spacecraft system. Simulation results show that the liquid motion with respect to the tank will cause the position offset of spacecraft, and the orbital velocity of spacecraft will not converge to zero when the spacecraft executes zero-impulse maneuvers with fuel consumption; and that the liquid is likely to experience violent and complicated sloshing motion, which may cause the instability in the rigid-body motion of spacecraft, during the orbital maneuvering when the tank is eccentrically installed in the rigid hub.