ISS Utilization: FLUIDICS (FLUId DynamICs in Space) Experiment
The sloshing of fluids inside tanks is one of the most important disruptions of satellite stability in microgravity conditions. A satellite tank is filled with liquid propellant and gas to maintain a sufficient pressure during the lifetime of the satellite. During a maneuver,the motion of the satellite leads to the motion of the fluids within the tanks. The center of mass of the fluids evolves and this generates forces and torques on the satellite structure which can deteriorate the pointing performances. For satellites requiring important accuracy on the attitude,the sloshing phenomenon have to be anticipated and technical solutions to limit its effects must be considered. Several studies have been conducted on the prediction of sloshing in microgravity conditions. 1)
The FLUIDICS experiment was a part of the Proxima mission of the CNES, the French space agency, lead by the ESA astronaut Thomas Pesquet in the International Space Station (ISS). The FLUIDICS experiment, represented in Figure 1, is basically a slow rate centrifuge able to reproduce the fluids motion inside a satellite tank in orbit. It consists of a spherical tank containing a safe substitute of propellant and air, connected by an arm to a motor.
Two spherical tanks with the same diameter Dt have been used in microgravity conditions. They are made of two polycarbonate half spheres glued together. These tanks are respectively filled with 50% and 75% of 3M Novec 2704 liquid. Figure 2 is a photograph taken on Earth of the tank half filled with orange Novec liquid. The liquid is an electronic card coating which has the same range of physical properties (viscosity µl and density ρl)as propellants used in the space industry and complies with the ISS safety guidelines. The perfectly wetting property of these propellants is still respected with the Novec fluid. This will enable us to consider a zero contact angle condition in the simulations presented hereafter. The other fluid contained in these tanks is air, the physical properties of which are denoted by µg and ρg. The surface tension between the liquid and the gas is symbolized by σ.
Launch: The FLUIDICS experiment was launched in 2016 to the ISS and was first installed and run by ESA astronaut Thomas Pesquet during his Proxima mission in 2016.
Orbit: Near circular orbit, altitude of ~400 km, inclination = 51.6º.
• September 15, 2020: The International Space Station is an exciting place for experiments. This one in particular was making waves in space. Called FLUIDICS, the experiment studies fluid dynamics in microgravity and recently performed another successful round of science on board the Space Station. 2)
Figure 3: Developed by French space agency CNES and co-funded by Airbus Defense and Space, the FLUIDICS experiment is probing how fluids behave in weightlessness (image credit: ESA/NASA)
- Have you ever tried walking while carrying a full cup of water? Your steps invariably cause the water to slosh about, making spills hard to avoid. Now imagine a satellite turning – the fuel inside will slosh, affecting the satellite’s stability. The experiment will help improve the performance of satellite propellant systems, extending their working lives by using every last drop in their tanks.
- A second part of the FLUIDICS experiment will look at capillary wave turbulence in liquids. On Earth, gravity and surface tension influence how energy dissipates in waves or ripples. In space, scientists can observe how surface forces behave without gravity.
- By looking at capillary wave turbulence without gravity interfering, researchers can single out non-linear interactions. This could help us improve climate models forecasting the sea states and better understand wave formation on Earth, like rogue waves for example.
- The experiment is made up of five small, transparent spheres housed in a black centrifuge seen here. Three spheres hold water for the wave-turbulence research; the other two carry a special liquid with low viscosity and little surface tension for sloshing.
- FLUIDICS was first installed and run by ESA astronaut Thomas Pesquet during his Proxima mission in 2016. The most recent session was completed by NASA astronaut Chris Cassidy in the European laboratory on board the Space Station.
• June 11, 2019: ESA astronaut Thomas Pesquet works on the FLUIDICS experiment inside the Space Station's European Columbus laboratory. 3)
Figure 4: Posting on social media, Thomas wrote: "The spheres for the Fluidics experiment. One liquid is to help get every drop of fuel out of satellite fuel-tanks, the other liquid is to understand surface turbulence in liquids. By looking at surface turbulence without gravity interfering researchers can single out what influences behavior that forms ripples. This could help us better understand ocean currents and wave formation on Earth"(image credit: ESA/NASA)
- Thomas' Proxima mission was the ninth long-duration mission for an ESA astronaut. It was named after the closest star to the Sun, continuing a tradition of naming missions with French astronauts after stars and constellations.
- During Proxima, Thomas performed around 50 scientific experiments for ESA and France’s space agency CNES, as well as took part in many research activities for the other Station partners. The mission was part of ESA’s vision to use Earth-orbiting spacecraft as a place to live and work for the benefit of European society while using the experience to prepare for future voyages of exploration further into the Solar System.
Alexis Dalmon, Mathieu Lepilliez, Sébastien Tanguy, Romain Alis,
Elena R. Popescu, Rémi Roumiguié, Thomas Miquel, Barbara
Busset, Henri Bavestrello, Jean Mignot, ”Comparison Between the
FLUIDICS Experiment and Direct Numerical Simulations of Fluid Sloshing
in Spherical Tanks Under Microgravity Conditions,” Microgravity
Science and Technology, Volume 31, Published: 17 January2019, pp:
123-138, ISSN 0938-0108, https://doi.org/10.1007/s12217-019-9675-4, URL: https://hal.archives-ouvertes.fr
2) ”Making waves in space,” ESA Science & Exploration, 15 September 2020, URL: https://www.esa.int/ESA_Multimedia/Images/2020/09/Making_waves_in_space
3) ”Thomas with Fluidics,” ESA Science & Exploration, 11 June 2019, URL: https://www.esa.int/ESA_Multimedia/Images/2019/06/Thomas_with_Fluidics
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (firstname.lastname@example.org).