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Introduction
Unlike the physics of liquids and solids, granular mechanics are not well understood. Predictions of granular response to applied forces have proven unreliable. In terrestrial gravity, impact cratering is a simple way to understand the effects of these forces. In previous experiments, depth of craters formed by projectile impact is used to analyze granular dissipation mechanics, as crater depth relates to the force exerted by the medium onto the projectile. Two competing hypotheses and equations have been generated: the penetration depth (d) scales as the 1/2 power of projectile density (p) and the 2/3 power of projectile diameter
(D) according to the equation: (where u= the tangent of draining response angle), independent of gravity (g), and the equation for the stopping force, where k is proportional to g and b is independent of g. We propose to investigate granular mechanics in microgravity conditions and compare our results with those acquired in the laboratory. In particular, we choose to focus on the depths of craters formed by projectile impact at a range of accelerations of gravity to test the two existing competing hypotheses to determine the nature of the stopping force and the role of gravity in setting the resistance of the sand to penetration. As granular materials are simultaneously ubiquitous and problematic in everyday life and industry, probing the nature of granular mechanics will provide very practical and useful insight.The Purpose (Mission)
(D) according to the equation: (where u= the tangent of draining response angle), independent of gravity (g), and the equation for the stopping force, where k is proportional to g and b is independent of g. We propose to investigate granular mechanics in microgravity conditions and compare our results with those acquired in the laboratory. In particular, we choose to focus on the depths of craters formed by projectile impact at a range of accelerations of gravity to test the two existing competing hypotheses to determine the nature of the stopping force and the role of gravity in setting the resistance of the sand to penetration. As granular materials are simultaneously ubiquitous and problematic in everyday life and industry, probing the nature of granular mechanics will provide very practical and useful insight.The Purpose (Mission)
Determine the validity of two competing hypotheses:
[1] independent of g [2]
, where k is proportional to g and b is independent of g.
Understand the role gravity plays in granular mechanics
Objectives
Objectives
Our team would like to investigate the role of gravity in granular mechanics. Previous work has determined that gravity is not a factor in penetration depth; our work seeks to determine the validity of this claim, and more specifically to test two competing hypotheses devised in terrestrial gravity. Our overarching goal is to determine the nature of the stopping force and the role of gravity in setting the resistance of the sand to penetration. Our experiment would examine penetration depth of craters in granular material formed by projectile impact of spheres with systematically varied densities and diameters, in 0.16g, 0.38g, g, and 1.8g. If the microgravity environment alters penetration depth of impact craters, this experiment could redefine understandings of granular mechanics.
Our team would like to investigate the role of gravity in granular mechanics. Previous work has determined that gravity is not a factor in penetration depth; our work seeks to determine the validity of this claim, and more specifically to test two competing hypotheses devised in terrestrial gravity. Our overarching goal is to determine the nature of the stopping force and the role of gravity in setting the resistance of the sand to penetration. Our experiment would examine penetration depth of craters in granular material formed by projectile impact of spheres with systematically varied densities and diameters, in 0.16g, 0.38g, g, and 1.8g. If the microgravity environment alters penetration depth of impact craters, this experiment could redefine understandings of granular mechanics.
Experimental Setup in Microgravity
Experimental Setup in Microgravity
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