California Institute of Technology

MECHANICAL RESPONSE OF SOIL IN REDUCED GRAVITY (2015)

Researchers in the Department of Civil and Mechanical Engineering at the California Institute of Technology (Caltech) and collaborators from the Jet Propulsion Laboratory (JPL) flew out of Melbourne, FL on Zero-G’s November 2015 Weightless Lab research program. A custom experimental apparatus was designed and built in a collaboration among researchers at Caltech, MIT, and JPL. Design choices were made based on observations from a previous research mission with Zero-G in November 2013.

The experiment was used to capture data at different microgravities to quantify soil (regolith) strength parameters. Results were gathered on each of the 25 parabolas (3 Martian gravity, 2 Lunar gravity, 20 zero gravity), while 5 additional tests were performed during normal plane operation at Earth’s gravity level. During each test, the experiment deformed a simulated regolith using a pushing block inside of an enclosure with a glass face. Force and displacement data were captured for the push block, while the deformation of the simulated regolith on the glass face was continuously captured with a high resolution camera for later analysis using digital image correlation (DIC).

With the combined datasets, regolith properties like the angle of restitution and the internal friction angle can be calculated. These results will be used to enhance our understanding of regolith properties in a variety of different environments important to future NASA missions on comets, asteroids, and Mars.

Researchers Dan Arthur (left), Jose Andrade (center), and Jason Marshall (right) conduct experiments on a simulated regolith at Martian gravity.

Jason Marshall (left), Jose Andrade (center), and Brian Trease (right) work on the experimental setup between parabolas.

Front face of the experimental setup including a camera to capture the deformation of the sand in the enclosure, power supplies, and various electronic components and wiring.

Experimental data being collected while Jason Marshall (left) and Jose Andrade (center) watch during a zero gravity parabola.