Using physics-based simulation towards eliminating empiricism in extraterrestrial terramechanics applications

TL;DR

This paper introduces a physics-based simulator for extraterrestrial terramechanics, challenging the reliance on Earth-based tests with gravitational offsets, and demonstrates its effectiveness through comparison with physical tests for lunar rover prototypes.

Contribution

The authors developed and open-sourced a physics-based simulator that accurately models low-gravity terramechanics, improving upon traditional Earth-based testing methods.

Findings

Simulator correlates well with physical test results

Challenges the necessity of gravitational offset in testing

Enables studies beyond trafficability, including resource utilization

Abstract

Recently, there has been a surge of international interest in extraterrestrial exploration targeting the Moon, Mars, the moons of Mars, and various asteroids. This contribution discusses how current state-of-the-art Earth-based testing for designing rovers and landers for these missions currently leads to overly optimistic conclusions about the behavior of these devices upon deployment on the targeted celestial bodies. The key misconception is that gravitational offset is necessary during the \textit{terramechanics} testing of rover and lander prototypes on Earth. The body of evidence supporting our argument is tied to a small number of studies conducted during parabolic flights and insights derived from newly revised scaling laws. We argue that what has prevented the community from fully diagnosing the problem at hand is the absence of effective physics-based models capable of simulating terramechanics under low gravity conditions. We developed such a physics-based simulator and utilized it to gauge the mobility of early prototypes of the Volatiles Investigating Polar Exploration Rover (VIPER), which is slated to depart for the Moon in November 2024. This contribution discusses the results generated by this simulator, how they correlate with physical test results from the NASA-Glenn SLOPE lab, and the fallacy of the gravitational offset in rover and lander testing. The simulator developed is open sourced and made publicly available for unfettered use; it can support principled studies that extend beyond trafficability analysis to provide insights into in-situ resource utilization activities, e.g., digging, bulldozing, and berming in low gravity.