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SPHERES Team to Continue Propellant "Slosh" Experiments in Microgravity
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SPHERES Team to Continue Propellant "Slosh" Experiments in Microgravity

On September 6th and 10th, the Synchronized Position Hold, Engage, Reorient, Experimental Satellites (SPHERES) Slosh investigation will continue onboard the International Space Station (ISS). The Slosh Experiment is examining 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 this investigation plans to improve our understanding of how propellants within rockets behave in order to increase the safety and efficiency of future engine designs.

Objectives for the upcoming Slosh Experiment sessions (Science 6 and 7) are:

  • Quantify the transition point from the surface tension-dominated fluid motion to inertial-dominated fluid motion
  • Use SPHERES thrusters to get better control of acceleration levels for low-g slosh testing
  • Investigate slosh dynamics associated with a 180 degree flip in low g
  • Investigate slosh dynamics associated with payload separation impulse events

All of the maneuvers included are based on input from industry partners, including the Orbital Sciences Corporation, SpaceX, and the United Launch Alliance. Each of these entities has expressed interest in the type of data collected by the Slosh Experiment on the ISS and have contributed to the development of the test plan. The data collected in these sessions will be used by these partners to anchor critical computer models that are used to design the latest generation of launch vehicles and spacecraft. Thanks to this one-of-a-kind data gathered on the ISS, NASA and private industry are working together to ensure the success of future missions, paving the way for a journey to Mars.

BACKGROUND: To explore the coupling of liquid slosh with the motion of an unconstrained tank in microgravity, NASA has teamed up with the Florida Institute of Technology (FIT) and the Massachusetts Institute of Technology (MIT) to perform a series of slosh dynamics experiments in the ISS using the SPHERES platform. The SPHERES testbed provides a unique, free-floating instrumented platform on the ISS that can be utilized in a manner that would solve many of the limitations of the current knowledge related to propellant slosh dynamics on launch vehicle and spacecraft fuel tanks. The Six Degrees Of Freedom (6-DOF) motion of the SPHERES free-flyer satellites are controlled by an array of cold-flow CO2 thrusters, supplied from a built-in liquid CO2 tank. Thus, the SPHERES can independently navigate and reorient themselves within the ISS. The intent of this project is to design an externally mounted tank to be driven inside the ISS by a set of two SPHERES devices. The tank geometry simulates a launch vehicle upper-stage propellant tank, and the maneuvers replicate those of real vehicles. The design includes inertial sensors, data acquisition, image capture, and data storage interfaces to a single-board computer onboard the flight article assembly. The design also includes mechanical and electronic interfaces to the existing SPHERES hardware, which includes self-contained packages that can operate in conjunction with the existing SPHERES electronics.

PROGRAM FUNDING: SPHERES is funded by the Advanced Exploration Systems (AES) program, Human Exploration and Operations Mission Directorate (HEOMD).

The Slosh Experiment is funded by the Launch Services Program, Kennedy Space Center.

ARC SPHERES TEAM: Jonathan Barlow (TI), Jose Benavides (TI), Jose Cortez, Robert Hanson, Simeon Kanis, Aric Katterhagen, Darryl LeVasseur, Ken Oyadomari (TI), and Cedric Priscal (TI)

POC: Jose Benavides, jose.v.benavides@nasa.gov

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