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Experimental exploration of granular motion on low-gravity planetary surfaces

Author: 
Adrienne Dove
Topic: 
Asteroid Population Characterization
Delivered As: 
Oral
Abstract Text: 

Exploration of small Solar System bodies such as asteroids and moons is essential to understanding the origins of our Solar System, and extending our reach beyond the Earth. Successful construction and operation of impact, landing, or sample return missions will require knowledge of the terrain on the surface of interest. We are developing a series of experiments that will support a more complete characterization of the regolith covering the surfaces of small Solar System bodies, for which the current knowledge is predominantly based on observational data. Observations of the behavior of granular matter in low-gravity environments will be achieved by placing different types and sizes of regolith-analog material into experiment cells that will be designed to reproduce the microgravity and vacuum environments present on the surfaces of small Solar System bodies. Our first experiments will be designed for parabolic airplane flights in order to maximize the number of experiment parameters that can be varied per flight campaign. Subsequent experiments will take advantage of the longer duration flights available from other suborbital and orbital providers. For parabolic flights, each experiment cell will be outfitted with mechanical components to enable a) changes in inclination of the cell wall, which will allow exploration of the dynamics of granular materials on sloped surfaces; b) vibration of sloped cell walls to induce seismic shaking of the granular bed; or c) small inlets that will be used to create puffs of gas that will simulate subsurface jets or surface disturbances due to rocket exhaust. We will utilize the variable flight profiles provided by parabolic airplane flights to produce relevant acceleration levels, from microgravity (i.e. asteroidal surfaces, ~0.01 g) to low-gravity (i.e. the Moon, 0.16g). We will also explore a variety of simulant types, including those meant to mimic both lunar and a variety of asteroidal compositions and size distributions. Further experiments will modify the chamber designs to enable the use of other microgravity platforms, such as suborbital flights, where a centrifuge-like device can be used to vary the gravitational levels for each experiment cell. Through these experiments, we will gain insight into the cohesive properties, particle size, and layer depth of the regolith on the surface of target asteroids or moons, which will be crucial to the success of science and exploration missions, as it will clarify choices for appropriate landing and exploration sites as well as the design requirements for exploration and ISRU hardware.

Co-Authors: 
Joshua Colwell, Adrienne Dove, Julie Brisset, Roberto Cruz, Zachary Foster, Merritt Robbins, Meghan Keough, Tyler Cox, and Kristen Brightwell
SSERVI Identifier: 
NESF2016-042

About SSERVI
Recognizing that science and human exploration are mutually enabling, NASA created the Solar System Exploration Research Virtual Institute (SSERVI) to address basic and applied scientific questions fundamental to understanding the Moon, Near Earth Asteroids, the Martian moons Phobos and Deimos, and the near space environments of these target bodies. As a virtual institute, SSERVI funds investigators at a broad range of domestic institutions, bringing them together along with international partners via virtual technology to enable new scientific efforts."