Microgravity Experiment of Granular Materials on International Space Station
Microgravity Experiment of Granular Materials on International Space Station
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Hosei O, Soichi Tatsumi
The University of Tokyo, Kyoto Institute of Technology
Abstract
Abstract
In this study, we present findings from a granular gas experiment conducted under microgravity conditions on the International Space Station in February 2023. Granular gas, comprised of dilute systems of granular particles in micro- gravity, exhibit unique dynamic behaviors that diverge from those of molecular gases, primarily due to their inelastic collision properties. Although simulations have extensively explored this process, empirical studies are rare, attributed to the necessity of a sustained, high-quality microgravity environment. Nonetheless, experimental verification is crucial, given the significant role of granular physics in space science, such as in the formation of celestial bodies, aerospace engineering, and potential space mining operations. Our experimental setup consisted of approximately 4,000 copper spheres, each with a diameter of 1.5mm, contained within a plastic sphere with a diameter of 100mm. To initiate particle movement, the system was shaken for 10 seconds, followed by a 1-minute observation period to monitor the cooling process. This cooling phase was meticulously recorded from both front and side perspectives for subsequent analysis. The outcomes of our experiment reveal that the decay of the average velocity of the granular gas closely matched the velocity decay predicted by simulations based on Haff’s law. Additionally, the velocity distribution of the granular gas exhibited a distribution different from the Maxwell-Boltzmann distribution. However, contrary to expectations, we did not observe clustering in the final state of cooling due to the influence of static electricity. This paper provides a detailed analysis and report of the experimental results.
Haff's Law
Haff's Law
We consider an infinitely extended granular gas com- posed of identical particles. Assuming that the number of particles per unit volume is sufficiently large, methods from statistical mechanics can be applied. When the system is homogeneous, by analogy with thermodynamics, the granular temperature T is defined by the following equation:
It is predicted that T(t) decays over time according to the following equation, known as Haff's Law.
Experimental Setup
Experimental Setup
Two cameras were positioned at perpendicular an- gles. A white background was used to enhance the visi- bility of the particles. All the equipment was set up on the experiment table in the Kibo module.
Analysis
Analysis
Created synthetic data for particle detection. Implemented 3D Tracking through Hough 3D Transform.
Result
Result
We observed the velocity decay and long-tail velocity distribution which is predicted from Haff's Law.
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