ESA GNC Conference Papers Repository

Recent changes in space regulation around end-of-life disposal (french <i>'Loi relative aux opérations spatiales'</i> for instance) strongly impact satellite design, in particular for LEO missions with a need to prove safe re-entry of the spacecraft. One of the most obvious technical solutions consists in carrying a larger amount of propellant to ensure a significant margin for controlled or semi-controlled re-entry operations. For agile earth observation missions, this necessarily leads to an increased impact of sloshing, directly disturbing the satellite pointing performance. For this reason, detailed knowledge and modeling of the sloshing phenomena has become crucial to ensure mission performance through all development stages of the satellite. Sloshing models range from complex CFD to simple mass spring models (based on Abramson theory, see paper 'The dynamic behavior of liquids in moving containers NASA-SP-106'), and whatever their complexity, are an important step when assessing closed loop AOCS performances. A common weakness of all those models is the lack of validation in the 0g domain, when capillary forces start dominating inertial effects. Indeed, while CFD tools can be validated on ground for 1g applications without much effort, obtaining test results in 0g calls for long duration tests in very clean micro-gravity conditions. Airbus Defence and Space in cooperation with CNES has therefore developed FLUIDICS (FLUId DynamIC in Space), an experimental setup to get experimental data of fluid dynamics in micro gravity, enabling thus CFD codes validation as final goal. The FLUIDICS experimental setup will be operated on the International Space Station in the frame of the PROXIMA mission of Thomas Pesquet. The overall FLUIDICS apparatus is more or less a slow rate centrifuge that can establish specific micro-gravity conditions on a sample tank. Two camera offer video recording capability and a dedicated sensor monitors the force generated by the fluid motion. First experimental run consist in several acceleration and speed profiles representative of typical satellite slew maneuvers and tranquilization phases. Two tanks will be used to study the impact of the filling ratio representative of the evolution during the satellite lifetime. The chosen fluid (Novec 2704) has been selected to have properties (wetting, viscosity,…) close to usual satellite propellants (hydrazine) while being compliant to ISS safety rules. Eventually, this experimental setup will provide in 2017 nowadays unavailable or confidential experimental data to validate sloshing models in microgravity. Innovative perspectives are also foreseen to study new tanks design mitigating the sloshing impact that can be used on the same FLUIDICS setup.