NASA: Snake-like robot EELS to explore Saturn moon

The US space agency NASA’s Jet Propulsion Laboratory (JPL) has tested a snake-shaped, versatile robot that is intended to autonomously explore inaccessible areas. The Exobiology Extant Life Surveyor (EELS) can independently map difficult terrain, as the JPL announced on Monday. The long-term plan is for the robot to explore Saturn’s moon Enceladus.

Enceladus is one of Saturn’s 83 moons. Freezing conditions prevail there. Beneath the ice crust, the EELS will be used to weave through small fissures and search for life in the oceans there. In order to achieve this, the robot must meet certain requirements. This is the only way he can get to places other robots can’t. Snakes, for example, can do this and so EELS is also designed based on the reptiles in terms of construction and movement.

screw drive

The JPL has been working on the robot since 2019. Since then it has undergone many revisions and tests. In the current version EELS 1.0 it is around 4 m long and weighs 100 kg. It consists of ten identical segments. They can turn and drive a screw-like thread that is used for locomotion. The construction has several advantages: It has good traction even on loose surfaces such as snow and at the same time it can hold on to the screw drive. To do this, the developers tested different types of screws – including plastic screws from the 3D printer with a diameter of 20 cm for loose ground and narrower, sharper metal screws for moving on ice.

For the past few months, the researchers have been testing the EELS monthly in field tests: at JPL’s Mars Yard, in the mountains of a Southern California ski resort, and at a local ice rink. The robot was tested on icy, snowy and sandy surfaces. The EELS must be able to move around autonomously and find the “right” path through the terrain on its own. In doing so, he has to calculate risks on his own and at the same time collect data with scientific instruments. If something goes wrong, the robot must be able to get itself out of the jam. Because human help is far away due to the communication delay between Earth and its intended area of ​​operation.

For this purpose, EELS has a sensor head equipped with lidar and stereo cameras. He can use it to create a 3D map of his surroundings. Using this data, EELS determines the safest way forward. Depending on the terrain, he uses a library of different gaits. It can squeeze through narrow gaps, move sideways and even curl up on itself.

development and testing

In order for locomotion to work, the final version of EELS will include 48 actuators in the form of small electric motors. Some of these have a force-torque sensor that gives the robot feedback on how much force it is applying to the ground. As a result, he can support himself in gaps on opposite walls and move vertically up or down.

The development team successfully tried this out in 2022 in a vertical shaft of the Athabasca Glacier in British Columbia. In September 2023 they plan to repeat the test with a revised version of EELS and test other forms of subglacial mobility in preparation for the ice moon Enceladus. The robot should also collect some physical and chemical data about the glacier. To do this, the researchers are equipping it with suitable sensors.

In developing the EELS, the team deviated from traditional methods, such as those used to create spacecraft. With robots, the philosophy is to carry out many rapid development steps with many test and correction cycles. “There are dozens of textbooks on how to construct a four-wheeled vehicle, but there is no textbook on how to construct an autonomous snake robot that boldly goes where no robot has gone before. We must write our own book. And that’s what we’re doing now,” says Hiro Ono, lead scientist at the EELS project.

(olb)