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Relatively recent discoveries have shown that large quantities of water can be found on moons of some of the planets among the gas giants in our solar system. Robotic mobility systems can study the varied geology and origins of these bodies if they are able to navigate the complex terrains of ocean worlds. The topographical features of ocean worlds present a unique combination of challenges for mobility. These include cryogenic ice, penitentes, salt evaporites, chaotic regions, and regolith with uncertain shear and sinkage properties. Uncertainty in both terrain properties and geometry motivates design of a platform that is mobile within a large range of obstacle geometries and terrain properties. This article reports on a research effort to study the requirements and numerically optimize the kinematic parameters of the rover to satisfy these goals. The platforms selected in the process were further verified via simulation. A simulation and analysis of grousers generated suitable designs for interaction with similar ledges and rough terrain. From this analysis, a prototype was developed and tested to meet the wide range of topography and terramechanics conditions expected on these bodies.

Energy absorbing materials, like foams used in protective equipment, are able to undergo large deformations under low stresses, reducing the incoming stress wave below an injury or damage threshold. They are typically effective in absorbing energy through plastic deformation or fragmentation. However, existing solutions are passive, only effective against specific threats and they are usually damaged after use. Here, we overcome these limitations designing energy absorbing materials that use architected lattices filled with granular particles. We use architected lattices to take advantage of controlled bending and buckling of members to enhance energy absorption. We actively control the negative pressure level within the lattices, to tune the jamming phase transition of the granular particles, inducing controllable energy absorption and recoverable deformations. Our system shows tunable stiffness and yield strength by over an order of magnitude, and reduces the transmitted impact stress at different levels by up to 40% compared to the passive lattice. The demonstrated adaptive energy absorbing system sees wide potential applications from personal protective equipment, vehicle safety systems to aerospace structures.

PUFFER (“pop-up flat-folding explorer robot”) is an expendable, two-wheeled NASA/JPL rover that is meant to explore the less-accessible regions of Mars. This paper presents the UC Berkeley prototype of PUFFER that was used to inform the mechanical design of the folding chassis for the ensuing NASA/JPL version. PUFFER is so named because it can fold itself to fit into tight spaces; its chassis consists of a 3-D linkage that can vary the sprawl angle of its wheels. This ability to sprawl, besides letting multiple PUFFERs fit into a parent rover, improves PUFFER’s slope-climbing ability by allowing it to lower its center of mass. To further improve slope climbing, each wheel is fitted out with nitinol brushes that serve to enhance ground traction. Together, these two features allow the Berkeley prototype of PUFFER to climb 47 deg rock inclines that have a surface roughness of about half its folded height. Other qualities of PUFFER are that it has a collapsible tail, is able to flip itself over, and requires only three actuators.