A rover trundles over rocky terrain, its four metal wheels clattering along until they encounter a seemingly insurmountable hazard: a steep slope. Down below is a potential trove of science targets. With a typical rover, the operators would need to find another target, but this is DuAxel, a robot built for situations exactly like this.
The rover is actually made of a pair of two-wheeled rovers, each called Axel. To divide and conquer, the rover stops, lowers its chassis and anchors it to the ground before essentially splitting in two. With the rear half of DuAxel (short for “dual-Axel”) firmly in place, the forward half undocks and rolls away on a single axle. All that connects the two halves now is a tether that unspools as the lead axle approaches the hazard and rappels down the slope, using instruments stowed in its wheel hub to study a scientifically attractive location that would normally be out of reach.
This scenario played out last fall during a field test in the Mojave Desert, when a small team of engineers from NASA’s Jet Propulsion Laboratory in Southern California put the modular rover through a series of challenges to test the versatility of its design.
“DuAxel performed extremely well in the field, successfully demonstrating its ability to approach a challenging terrain, anchor, and then undock its tethered Axel rover,” said Issa Nesnas, a robotics technologist at JPL. “Axel then autonomously maneuvered down steep and rocky slopes, deploying its instruments without the necessity of a robotic arm.”
The idea behind creating two single-axle rovers that can combine into one with a central payload is to maximize versatility: The four-wheeled configuration lends itself to driving great distances across rugged landscapes; the two-wheeled version offers a nimbleness that larger rovers cannot.
“DuAxel opens up access to more extreme terrain on planetary bodies such as the Moon, Mars, Mercury, and possibly some icy worlds, like Jupiter’s moon Europa,” added Nesnas.
The flexibility was built with crater walls, pits, scarps, vents, and other extreme terrain on these diverse worlds in mind. That’s because on Earth, some of the best locations to study geology can be found in rocky outcrops and on cliff faces, where many layers of the past are neatly exposed. They’re hard enough to reach here, let alone on other celestial bodies.
The rover’s mobility and ability to access extreme locations is an