NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Microgravity Experiments to Evaluate Electrostatic Forces in Controlling Cohesion and Adhesion of Granular MaterialsThe bulk behavior of dispersed, fluidized, or undispersed stationary granular systems cannot be fully understood in terms of adhesive/cohesive properties without understanding the role of electrostatic forces acting at the level of the grains themselves. When grains adhere to a surface, or come in contact with one another in a stationary bulk mass, it is difficult to measure the forces acting on the grains, and the forces themselves that induced the cohesion and adhesion are changed. Even if a single gain were to be scrutinized in the laboratory, it might be difficult, perhaps impossible, to define the distribution and character of surface charging and the three- dimensional relationship that charges (electrons, holes) have to one another. The hypothesis that we propose to test in microgravity (for dielectric materials) is that adhesion and cohesion of granular matter are mediated primarily by dipole forces that do not require the presence of a net charge; in fact, nominally electrically neutral materials should express adhesive and cohesive behavior when the neutrality results from a balance of positive and negative charge carriers. Moreover, the use of net charge alone as a measure of the electrical nature of grain-to-grain relationships within a granular mass may be misleading. We believe that the dipole forces arise from the presence of randomly-distributed positive and negative fixed charge carriers on grains that give rise to a resultant dipole moment. These dipole forces have long-range attraction. Random charges are created whenever there is triboelectrical activity of a granular mass, that is, whenever the grains experience contact/separation sequences or friction. Electrostatic forces are generally under-estimated for their role in causing agglomeration of dispersed grains in particulate clouds, or their role in affecting the internal frictional relationships in packed granular masses. We believe that electrostatic, in particular dipole-mediated processes, are pervasive and probably affect, at some level, everything from astrophysical-scale granular systems such as interstellar nebulae, protoplanetary dust and debris disks, planetary-scale systems such as debris palls from meteorite impact, volcanic eruptions, and aeolian dust storms, all the way to industrial-scale systems in mining, powder and grain processing, pharmaceuticals, and smoke-stack technologies. NASA must concern itself with the electrostatic behavior of dust and sand on Mars because of its potentially critical importance to human exploration. The motion and adhesion of martian surface materials will affect the design and performance of spacesuits, habitats, processing plants, solar panels, and any externally exposed equipment such as surface rovers or communication and weather stations. Additionally, the adhesion of dust and sand could greatly enhance contact with the potentially toxic components of the martian soil.
Document ID
20000025374
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Marshall, J.
(Search for Extraterrestrial Intelligence Inst. Moffett Field, CA United States)
Weislogel, M.
(NASA Lewis Research Center Cleveland, OH United States)
Jacobson, T.
(NASA Lewis Research Center Cleveland, OH United States)
Date Acquired
August 19, 2013
Publication Date
September 1, 1999
Publication Information
Publication: Studies of Mineralogical and Textural Properties of Martian Soil: An Exobiological Perspective
Subject Category
Space Processing
Meeting Information
Meeting: Microgravity Fluid Physics and Transport Phenomena
Location: Cleveland, OH
Country: United States
Start Date: January 1, 1998
Funding Number(s)
CONTRACT_GRANT: NCC2-926
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
Document Inquiry

Available Downloads

There are no available downloads for this record.
No Preview Available