Abstract: For a full-size low-temperature on-orbit tank,a numerical model describing the movement of microgravity two-phase fluid was established.The transient simulation was carried out to discuss the fluid movement characteristics under the excitation of initial liquid level tilt,lateral sine wave,and slow rotation under 10^-3g₀overload,and the effect of the antislosh baffle was discussed.The study found that:(1)When experiencing variable overloads,the time for initial inclined liquid surface reaching a new equilibrium takes less than 80 s.When the inclination angle is large,the baffle can accelerate the recovery process of liquid surface;(2)For lateral excitation,when the liquid level is near and below the baffle,the baffle can always exert the anti-sloshing effect regardless of gravity.In addition,the effect has a linear drop relationship with the liquid level.Under the same excitation,the sloshing range of the 2.6 m liquid level can be suppressed by about 2.6 cm,while that of 3.2 m is only 0.3 cm.(3)The response of hydrogen and oxygen is different during lateral excita-tion.The sloshing amplitude of hydrogen can reach 6.5 cm,accounting for 43.3% of the maximum allowable value,while that of oxygen is 4.0 cm,accounting for only 16.0%.However,the different types of propellant when the liquid surface is inclined and the slow rotation excitation do not cause obvious differences in fluid behavior.(4)Both lateral excitation and slow rotation may expose the bottom of the tank to the ullage,which should be considered and limited in the propellant management,and the angular velocity should be reasonably designed.The work of this paper helped to understand the law of cryogenic propellant flow motion during variable excitations in space,and provides theoretical guidance for the fluid control scheme and aircraft timing.