The Need for and Feasibility of Alternative Ground Robots to Traverse Sandy and Rocky Extraterrestrial Terrain

Abstract

Robotic spacecraft have vastly increased our ability to explore extraterrestrial surfaces. [1][2][3][4][5][6] Mobile robots have enabled exploration beyond a static landing site and allowed discovery-driven investigations on both the Moon and Mars. They have helped us understand the geologic history and surface environments of both bodies, conducting scientific campaigns analogous in many ways to that of a terrestrial field geologist.Since the first deployments on the Moon nearly half a century ago, mobile planetary exploration robots have progressively increased in their capabilities and enabled us to access a range of scientific targets on extraterrestrial surfaces. [2][3][4][5] To date, all of the successfully landed lunar and Martian mobile exploration robots, as well as the majority of those being developed, have adopted a conventional wheeled rover platform with a variety of architectures. [5,7] This is not surprising because one of the highest priority considerations for space applications is to maximize mechanical reliability, where wheeled platforms have excelled. [2,3,7,8] These missions have been hugely successful, often exceeding mission design lifetime and traverse distance. The 6-wheel Mars Exploration Rover Opportunity currently holds the planetary rover distance record, driving over 45 km across Meridiani Planum. [9] Similarly, the Soviet Union's 8-wheel Lunokhod 2 rover traversed 39 km across the surface of the Moon in 1973. [10] The recent 6-wheel Chinese Yutu and Yutu-2 lunar rovers have travelled hundreds of meters on the surface of the Moon. [11] Although these rovers have had an impressive track record exploring both the Moon and Mars, their missions have revealed significant limitations faced by wheel-based mobility systems, which hinder scientific exploration. For example, the Spirit Mars Exploration Rover ultimately reached the end of its mission due to a low power state after becoming embedded in a patch of loose soil at a location known as "Troy." The ferric sulfate dominated soil at this site had very low cohesion, thus being mechanically weak, and extended to a depth comparable to the wheel radius. [12] Unfortunately, this deposit was hidden beneath a weakly indurated soil crust, rendering the hazard hidden until the rover was already embedded. [9] The challenge of extricating Spirit was made more difficult due to the failure of one of its six wheels earlier in the mission, requiring modified driving strategies. [12] The Opportunity rover had similar challenges navigating ubiquitous large aeolian ripples in Meridiani Planum. In particular, it was stuck for an extended time embedded in the loose sand of the "Purgatory" ripple [13] (Figure 1A).More recently, the Curiosity Mars rover has incurred significant wheel damage along its traverse due to angular rocks protruding from the surface, which punctured the thin aluminum

Environmental force sensing helps robots traverse cluttered large obstacles

“…Sensors like cameras, radars, and LiDAR are used to create a geometric map of the surroundings, then a collision-free path is planned to avoid physical contact with obstacles [3][4][5][6][7]. However, for search and rescue through earthquake rubble [8,9], environmental monitoring through dense vegetation [10], and extraterrestrial exploration through Martian and lunar rocks [11], robots often need to traverse complex 3D terrain with densely cluttered obstacles as large as themselves by physically interact with the obstacles. In these situations, geometry-sensing based obstacle avoidance faces difficulties.…”

Maneuvering on non-Newtonian fluidic terrain: a survey of animal and bio-inspired robot locomotion techniques on soft yielding grounds

“…The problem of locomotion in deformable grounds is important to solve because it would facilitate new robotic applications such as search and rescue in wet forests, muddy fields, avalanches, and mudslides ( Schneider and Wildermuth, 2016 ); for the agricultural vehicles operating on wet soils (e.g., rice fields) ( Duckett et al., 2018 ; Oliveira et al., 2021 ); for exploration or excavation of materials (e.g., wood and ore) with a minimal environmental impact ( Billingsley et al., 2008 ; Lopes et al., 2020 ); for environmental monitoring in high-biodiversity areas (e.g., river estuaries, bogs, and shores) ( Dunbabin and Marques, 2012 ); or for extra-terrestrial exploration ( Li and Lewis, 2022 ).…”

Granular Resistive Force Theory Extension for Saturated Wet Sand Ground

“…The resistive force theory for GM was studied in this case, the challenge was solved, and the athletic ability of NASA's rover was dramatically improved [2,3]. The way the field robot interacts with the granular media in the working process plays a vital role in the motion performance of the robot [4]. The ground of beach and seabed formed by sand and water is SWGM.…”