The ISS SPHERES-Slosh Experiment: Slosh Data Acquisition and Analysis

Accurate prediction of liquid propellant slosh coupled with rocket launch vehicle or spacecraft dynamics requires computational fluid dynamics (CFD) models validated with long-duration, low-gravity slosh data. In a low-gravity environment, space vehicle disturbances, such as residual accelerations, orbital maneuvers, and docking, can induce propellant slosh. The sloshing propellant can couple with the vehicle dynamics to cause unintended motions. Tank propellant management and control system design requires accurate prediction of slosh dynamics, for which CFD is typically employed. However, the CFD must be validated using physically relevant test data. In pursuit of this objective, the SPHERES-Slosh Experiment (SSE) was developed and utilized to acquire long-duration, low-gravity slosh data while operating on the International Space Station (ISS). The SSE consisted of a slosh tank propelled by two SPHERES free-flying robots, or the SSE was maneuvered by an ISS crewmember. The SSE simultaneously captured video of slosh events from two cameras and motion data from inertial measurement units. The test sessions yielded a dataset of correlated inertial measurements and images that can be used by engineers and mission planners to benchmark CFD models. The design, qualification, ISS operations, and slosh data analysis for the SSE, along with CFD simulations, are presented.