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'SPHERES' Project Successfully Completes Tether Slosh Science Session 3
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'SPHERES' Project Successfully Completes Tether Slosh Science Session 3

The Synchronized Position Hold, Engage, Reorient, Experimental Satellites (SPHERES) project successfully completed Tether Slosh Science Session 3. In this session the International Space Station (ISS) crew ran a total of 17 tests with two different fluid tanks: a liquid-filled tank and a solid tank of same mass. The objective of this test session was to run and compare a consistent series of tests in two tethered setups: first with a 40% full liquid-filled tank, and then with a solid tank of the same mass. The comparison of system dynamics obtained using the two different tanks will demonstrate and evaluate how mechanical energy is dissipated in the fluid and how the fluid affects the control of the tethered system.

The telemetry and video data acquired during Tether-Slosh Science 3 will be analysed and compared with Computational Fluid Dynamic (CFD) simulations to highlight in the experimental setup the presence of effects already predicted in simulation. The evaluation of how the fluid and solid tanks affected the closed-loop control of the tethered system will inform future development of control strategies for the fourth and final test session of the program.

BACKGROUND: SPHERES are bowling ball-sized spherical satellites with power, propulsion, computers, and navigation that can be used for inspections, maintenance, spacecraft assembly, and other intravehicular operations. The ISS has been using three of them to conduct science and test a diverse array of hardware and software for more than a decade.

The SPHERES Tether Demonstration project onboard ISS will help with understanding tethering dynamics to capture loose objects and “space tug” chase vehicles in zero gravity. With this new capability, researchers will be able to improve computer programs and modeling needed for free-flying satellites to remove space debris and capture scientific samples from planetary objects on future deep space missions. The SPHERES Tether is a new integrated payload designed and developed by Airbus Defense & Space (Airbus DS) in collaboration with NASA and the Massachusetts Institute of Technology (MIT).

The SPHERES Slosh investigation examines the way liquids move inside containers in a microgravity environment. The phenomena and mechanics associated with such liquid movement are still not well understood and are very different than our common experiences with a cup of coffee on Earth. Rockets deliver satellites to space using liquid fuels as a power source, and in order to increase the safety and efficiency of future vehicle designs this investigation plans to improve our understanding of how propellants within rockets behave.

NASA PROGRAM FUNDING: Advanced Exploration Systems (AES) program, Human Exploration and Operations Mission Directorate (HEOMD)

ARC SPHERES TEAM: Jonathan Barlow, Jose Benavides, Jose Cortez, Robert Hanson, Simeon Kanis, Aric Katterhagen, Don Soloway, and Andres Vargas

POINT OF CONTACT: Jose Benavides, jose.b.benavides@nasa.gov

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