Pasadena, CA – On a bleak stretch of the Colorado Desert in Southern California, a compact four-wheeled rover recently trundled about 16 miles (26 kilometers) with minimal intervention from the team of engineers trailing it. Called ERNEST (Exploration Rover for Navigating Extreme Sloped Terrain), this prototype is being used by NASA to advance both robotic autonomy and the ability to traverse challenging landscapes.
Developed at NASA’s Jet Propulsion Laboratory in Southern California, ERNEST is 4 feet (1.2 meters) long. Not only can it lift each of its mesh wheels to get past obstacles that would stymie Curiosity and Perseverance, NASA’s six-wheeled Mars rovers, but the prototype also has enhanced independent decision-making capabilities. These mobility and autonomy advances could be infused into future missions that will venture to previously inaccessible areas of the Red Planet or the Moon.
In the field, ERNEST served as a testbed for a potential future lunar mission requiring higher speeds and much greater mileage than can be accomplished by current rovers. This technology could be used to inform future designs for exploration efforts on the Moon and beyond.
“This testing is helping us refine the mobility hardware and autonomy software to navigate extreme distances across a wide range of terrain and lighting conditions anticipated on the Moon,” said Issa Nesnas, a principal technologist at JPL who led the recent testing as head of autonomy for a NASA mission concept for a potential future long-range lunar rover.
Nesnas’ team is using ERNEST to demonstrate it is possible to build a rover that’s twice as big as the prototype and capable of a long-distance Moon mission. During the recent campaign, ERNEST traveled at speeds up to 0.6 mph (1 kph) over 37 hours of driving, across seven days of intermittent testing. That’s an order of magnitude above the top speed Perseverance and Curiosity can navigate.
“You could do a science road trip across the Moon — or Mars — with this vehicle,” said James Keane, a JPL planetary scientist working on lunar missions.
The initial goal of the team that developed ERNEST was mechanical: to design a relatively simple, low-cost rover that advances the trusted rocker-bogie suspension system featured on every Mars rover since NASA’s Sojourner. This passive system keeps relatively constant weight on all six wheels, thanks to pivot points and struts that enable each one to adapt to the changing surface.
On ERNEST, the active suspension lets the rover manage weight distribution among its wheels. Two powered joints in front articulate a gimbal that allows the rover to drive using different gaits like squirming, wheel-walking, and obstacle-climbing.
With a clutch mechanism, it can switch between active and passive suspension, which is less terrain capable but more energy efficient. With four steerable wheels, it can drive in any direction, including sideways.
