The robot inspired by Dad’s long legs could one day weave through Martian caves

Robot engineers are no strangers to turning to nature for inspiration. In recent years, birds, dogs, extinct sea creatures, and even humans themselves have all served as a starting point for new mechanical designs. Now, researchers at Stanford are citing the Harvestman spider, better known as the long legs of a daddy, as inspiration for a new robot design that they think could be better equipped at navigating uneven rocky caves and lava tubes. One day, they hope this spider-like design could even help robots navigate the icy caverns of the moon and Mars.

How does the spider robot work?

The researchers introduced their new machine called the “ReachBot”. an article published today in the magazine Science Robotics. ReachBot has multiple extendable boom arms that it can use to reach for rocks and propel itself forward. Each limb is attached with a three-finger gripper that grips the rocks and uses them as anchor points. The long-leg design could potentially allow the robot’s limbs to access the floor, ceiling, and walls of a lava tube or cave, which in turn provides greater leverage. This unique positioning, the researchers write, allows the ReachBot to “adopt a wide range of possible configurations, support positions, and force application options.”

ReachBot attempts to fill the form factor gap between existing exploration robots. Small robots, the researchers say, are useful for navigating tight hallways, but typically have limited range. Larger robots, on the other hand, may be able to reach a larger area but may become bogged down by their weight and mechanical complexity. ReachBot offers a compromise by relying on a small main body with limbs that can expand and reach as needed.

The robot uses a series of built-in sensors to scale the area in front of it and look for hollow rocks or other signs that point to a graspable area. Like a physical spider. ReachBot does not immediately assume that rock surfaces are flat, but instead looks for “rounded features that the gripper can partially enclose.” Researchers say they tested the robot in simulation to help it improve its ability to correctly identify graspable surfaces and help plan footsteps. After the simulation, ReachBot was tested in the real world in an unmanned lava tube near Pisgah Crater in the Mojave Desert.

“The field test results confirm predictions of maximum grip forces and underscore the importance of identifying and directing toward convex rock features that provide strong grip,” the researchers write. “They also highlight a feature of grab planning with ReachBot, which is that identifying, pursuing, and extending booms involves a higher level of involvement than grabbing objects in production scenarios.”

ReachBot can help researchers explore deep caverns and caverns on other planets

Researchers believe the ReachBot’s spider-like design could have extraterrestrial applications. Lava tubes like those found in the Mojave Desert where the robot was tested remove some of the area on the surface of the moon and Mars. In the latest example, researchers say the ancient subterranean environments on the Red Planet remain relatively unchanged during the time when some believe the planet was habitable. These sheltered cave areas, they write, “may provide sites for future human habitation.”

In theory, future exploratory space robots could use a design like ReachBot’s to explore more deeply into areas that contemporary robots might find inaccessible. Elsewhere, researchers are exploring how three-legged jumping machines and four-legged dog-inspired robots could similarly help scientists learn more about undiscovered areas of our solar system neighbors.