Speaker
Description
In spacecraft such as liquid-propellant rockets and satellites, the liquid propellant in the tank oscillates due to disturbances caused by engine thrust fluctuations and attitude control. This is called sloshing, and the change in the center of gravity of the liquid caused by sloshing interferes with guidance and control of spacecraft. As a conventional countermeasure against sloshing, baffle plates are employed to damp liquid surface oscillation. Together with thrusters and reaction wheels on the airframe side, center of gravity is controlled. However, it has been pointed out that when large-amplitude sloshing occurs in a microgravity environment, the liquid may collide the baffle plates and deteriorate the behavior of the aircraft. The force generated by large-amplitude sloshing cannot be absorbed by thrusters or reaction wheels, and there is a high risk that the aircraft will tip over. Therefore, technology is necessary to quantitatively predict the effects of large-amplitude sloshing in a tank equipped with baffle plates on propellant and aircraft attitude. The purpose of this study is to propose an improved mechanism to suppress liquid behavior while reducing the adverse effects on the aircraft attitude when large-amplitude sloshing occurs, through microgravity experiments and coupled liquid-fuselage analysis. This paper presents experiment and numerical computations for a hypothesis of free-fall and vertical landing of the aircraft on a microgravity astral body. The experiment was conducted in cooperation with JAXA at Uematsu Electric's drop tower. Sloshing in a microgravity environment was generated by moving the tank vertically upward during free fall, and the liquid surface deformation was recorded and data was collected. In the experiment, the tank move was performed after waiting 1 second after the start of the fall. As a result, it was observed that after the tank wall surface was wetted, the liquid column rose significantly and impacted the tank ceiling. Numerical computation was also performed under the same conditions as in the experiment. As a result, the tank wall surface is wetted and liquid column rose in the same way as the experiment, as well as the force exerted by the liquid on the tank is evaluated. In addition, Numerical computation about the tank with baffle plate was performed. It was found that the baffle plates prevent the liquid level from rising in a microgravity environment, thereby suppressing the behavior of the liquid and the forces exerted by the liquid on the tank walls. The above results are for the ideal case where the spacecraft lands vertically and all legs of the spacecraft are grounded at the same time. In a real case, it is possible that all the legs do not touch the ground at the same time and the aircraft can rotate. If this situation happens, the liquid can impact the baffle plates and adversely affect the aircraft's attitude. In the future, we plan to evaluate the case of rotation by calculating the moments.
| Keywords | Liquid sloshing, Drop tower, CFD, Baffle plate |
|---|
