NASA’s Jet Propulsion Laboratory (JPL) has created a self-propelled, autonomous robotic snake designed to explore extreme extraterrestrial terrain. Its first-of-its-kind propulsion system means it can boldly go where a robotic snake has never gone before.
Dubbed the Exobiological Existing Life Investigator (EELS), the robotic snake was inspired by a desire to search for life deep inside Saturn’s icy moon Enceladus.
In the mid-to-late 2000s, when the Cassini spacecraft sent images of Enceladus, one of Saturn’s 83 moons, back to Earth, scientists discovered that it was active, hiding a sea of salty liquid water beneath its crust, and only a few worlds Known to have. What’s unique about Enceladus — it’s small enough to be the length of the United Kingdom — is that it continually spews icicles from the ocean, mixing with water and simple organic chemicals, into space.
Studying these plumes and the narrow vents through which they escape is what prompted the development of EELS. Construction of the prototype started in 2019 and is regularly updated. Since 2022, the JPL team has been conducting monthly field tests to improve the robot’s hardware and software so it can operate autonomously.
The current iteration of the EELS is 13 feet (4 meters) long and weighs about 220 pounds (100 kilograms). Its 10 identical rotating parts use screw heads for propulsion and grip. The EELS team experimented with different screws for different terrains: 3D-printed plastic screws for looser terrain and sharper metal screws for ice.
The team tested EELS using a snowy “robot playground” at a Southern California ski resort, an indoor ice rink, and a sandy field. The testing process is instructive as they have entered new areas of EELS.
“Our concept of robot development is different from traditional spacecraft, with many rapid test and correction cycles,” said JPL principal investigator Hiro Ono. “There are dozens of textbooks on how to design a four-wheeled vehicle, but none on how to design a four-wheeled vehicle.” How to design an autonomous snake robot to boldly go where no robot has gone before. We have to write our own.”
Given the communication lag between Earth and deep space, EELS’ ability to operate autonomously is important. If it encounters a problem, it needs to be able to recover on its own without relying on human assistance.
“Imagine a car driving itself, but there are no stop signs, no traffic lights, not even any roads,” said Rohan Thakker, the project’s autonomous driving lead. “The robot has to figure out what the path is and try to follow it. Then it needs to descend from a height of 100 feet (30 meters) without falling.”
To assist autonomy, EELS uses four pairs of stereo cameras and LiDAR (Light Detection and Ranging) to generate a 3D map of its surroundings. LiDAR determines distance by aiming a laser at a surface or object and measuring the time it takes for the reflected light to return to the receiver. EELS uses this information to create navigation algorithms so that it can more easily traverse challenging spaces.
Last year, to test the mapping capabilities of EELS, the JPL team lowered the robot’s head — the part containing the camera and LiDAR — into a vertical shaft in the Athabasca Glacier in the Canadian Rockies. They will return to the glacier in September with an updated version of EELS to see how it performs.
In its final form, EELS will consist of 48 small electric motors (actuators), allowing greater flexibility. Many have built-in force-torque sensing, which will allow the EELS to “feel” how much pressure it is exerting on the terrain. This will help it navigate uneven surfaces in tight spaces like a rock climber, swinging up or down by pushing against opposing walls.
The next step is to integrate scientific instruments.
“So far our focus has been on autonomous capabilities and mobility, but ultimately we will look at what science instruments can be integrated with EELS,” said EELS project manager Matthew Robinson. “Scientists tell us where they want to go, what they’re most interested in, and we’ll provide a robot to take them there.”
The adaptability of EELS means that, in addition to Enceladus, the robotic snake could also be used to explore the polar ice caps of Mars, or the deep ice crevasses on our planet.
It will be a while before EELS glides over the terrain of other planets, though. Scientists hope to have the robot ready by next fall, but expect to have to wait 10 years for the spacecraft to glide EELS to Enceladus.
The video below from NASA’s Jet Propulsion Laboratory shows EELS being tested in different environments.
(embed) https://www.youtube.com/watch?v=ifCIDT4X9AM (/embed)
Testing JPL’s new snake-like robot