Probing regolith-covered surfaces in low gravity

Jonathan E Kollmer,Sean Shefferman,Adrienne Dove,Robert Bullard,Anna Jackson,Joshua Colwell,Karen E Daniels,Riley Reid,Tristan Emm,Jack Featherstone,M.A Aguirre,S Luding,R Soto,L.A Pugnaloni

doi:10.1051/epjconf/202124902005

Abstract

The surfaces of many planetary bodies, including asteroids, moons, and planets, are composed of rubble-like grains held together by varying levels of gravitational attraction and cohesive forces. Future instrumentation for operation on, and interacting with, such surfaces will require efficient and effective design principles and methods of testing. Here we present results from the EMPANADA experiment (Ejecta-Minimizing Protocols for Applications Needing Anchoring or Digging on Asteroids) which flew on several reduced gravity parabolic flights. EMPANADA studies the effects of the insertion of a flexible probe into a granular medium as a function of ambient gravity. This is done for an idealized 2D system as well as a more realistic 3D sample. To quantify the dynamics inside the 2D granular material we employ photoelasticity to identify the grain-scale forces throughout the system, while in 3D experiments we use simulated regolith. Experiments were conducted at three different levels of gravity: martian, lunar, and microgravity. In this work, we demonstrate that the photoelastic technique provides results that complement traditional load cell measurements in the 2D sample, and show that the idealized system exhibits similar behaviour to the more realistic 3D sample. We note that the presence of discrete, stick-slip failure events depends on the gravitational acceleration.

Highlights

Understanding how grains rearrange when probed is inte- crogravity ) were achieved during a parabolic flight camgral to developing safe and efficient techniques for sample paign conducted by Zero Gravity Corporation
While the dynamics of a driven flexible probe have yet to be extensively explored in a low gravity environment, there has been recent interest in the insertion of flexible probes into granular materials on Earth [6, 7]
We show that globally averaged parameters taken from photoelastic response images, such as the brightness of each frame, exhibit the same response as the load cell

Summary

Introduction

Understanding how grains rearrange when probed is inte- crogravity ) were achieved during a parabolic flight camgral to developing safe and efficient techniques for sample paign conducted by Zero Gravity Corporation. While the dynamics of a driven flexible probe have yet to be extensively explored in a low gravity environment, there has been recent interest in the insertion of flexible probes into granular materials on Earth [6, 7]. We show that globally averaged parameters taken from photoelastic response images, such as the brightness of each frame, exhibit the same response as the load cell.

Results

Conclusion