2/12/2025
Assistant Professor Justin Yim, who joined the Department of Mechanical Science and Engineering in 2023, was recently awarded Phase I funding from the NASA Innovative Advanced Concepts (NIAC) program for his jumping robot proposal. The grant marks his first major funding award as a faculty member.
Per its description, NIAC “nurtures visionary ideas that could transform future NASA missions with the creation of breakthroughs—radically better or entirely new aerospace concepts.” NIAC recently announced its 2025 award winners, for which Yim’s project received mention.
Yim’s proposed robot, Legged Exploration Across the Plume (LEAP), presents a novel sampling concept for exploration of Saturn’s moon Enceladus—which is known to have an icy, oceanic surface characterized by numerous ice volcanoes.
“Enceladus has liquid water underneath an icy crust,” Yim described. Most of Enceladus’s surface is covered by water, which presents the possibility of an ocean world. Investigating the water’s composition could be invaluable to scientists’ understanding of life in space, and Enceladus itself provides a unique means of gathering data samples—its volcanoes regularly release molecules at the surface, negating the need to break through several feet of icy crust.
However, the crust may present extremely rough or slippery terrain, posing a significant obstacle for surface travel. Rockets are also less than ideal, as landing on the surface could compromise data samples through propellant pollution. Furthermore, Enceladus has virtually no atmosphere at its surface, ruling out the possibility of flying vehicles.
Enter Yim’s expertise in jumping robots. “Unlike conventional ground robots, jumping robots can cover large distances—they can get over big ravines or other obstacles,” he said. “Unlike flying robots, they don’t need an atmosphere, and unlike rockets, they don’t release propellant.”
A jumping robot on Enceladus would experience the additional benefit of lower gravity—approximately 80 times less than that of Earth’s.
During his doctoral studies at the University of California-Berkeley, Yim developed a one-legged robot called Salto that demonstrated precise jumping capability. With an approximate maximum jumping height of four feet, Salto utilizes a reaction wheel to control its pitch and a pair of propellers to control its roll.
Yim’s nine-month Phase I study, which will begin in April, will use Salto’s platform as a basis for developing LEAP, with a focus on enabling the robot to right itself from falls and calibrating its jumping mechanism for Enceladus’s reduced gravity.
(Above: While performing a sequence of hops, Salto is able to recover energy on each bounce, enabling more efficient motion.)
“We’re thinking of adding two angled reaction wheels to control the pitch and roll while also assisting the robot when it hits the ground,” Yim said, noting that absorbent wheels could act as bumpers to prevent damage to the robot. “The robot could also use the wheels on the ground for fine maneuvering.”
Yim’s research explores the feasibility of a jumping robot extension to NASA’s proposed mission concept Enceladus Orbilander, in which a probe would orbit and then land on Enceladus to deploy a robotic vehicle for data collection.
His doctoral student, Neil Wagner, will assist in developing components for LEAP. The pair will collaborate with Dr. Ethan Schaler, Dr. Morgan Cable, Ryan McCormick, and Stephen Gerdts from NASA’s Jet Propulsion Laboratory (JPL), which is managed for the agency by Caltech in Pasadena, California. The JPL team will focus on investigating materials for the robot that can withstand a cryogenic environment as well as characterizing potential behavior of the surface’s icy particles—i.e., how the ice will behave when the robot jumps on it. Schaler is Yim’s former lab mate.
“[Schaler] had the idea for LEAP in the back of his mind as something we could work on together,” Yim said. “He reached out to me and we put this concept together.”
Yim’s grant also presents opportunity to add value to jumping robot technology.
“I’m really excited to figure out the feasibility for jumping robots in a condition that’s really challenging for other platforms,” he said. “This could be the place where jumping robots can really shine.”