The University of California, Santa Barbara, and the Georgia Institute of Technology have been collaborating on a robot that isn’t a million miles away from the Graboids — an invertebrate species of monstrous gigantic worms that travel underground, pushing aside dirt as they dig — from the classic comedy Tremors.
It’s a tunneling, snake-inspired concept that can burrow through soil or soft sand, albeit it’s currently much smaller and considerably less prone to nibbling on unwary cattle and humans. And, according to its designers, it may one day be used to create surface regolith on other worlds. Is this the way space rovers will be in the future?
“We developed a type of burrowing robot that takes a new approach to burrowing by trying to reduce resistive forces rather than combating them,” said Nicholas Naclerio, a graduate mechanical engineering student researcher at UC Santa Barbara. “The three principles [that] enable it are tip extension to eliminate drag along its sides, air fluidization to reduce the resistive force of granular media, and asymmetry to control lift forces produced in horizontal burrowing.”
Surprisingly low-tech is the robot itself. Its body is made of ripstop nylon fabric that is airtight. As it wends its underground way, a nylon tube delivers air to its tip, which blows aside the particulate in front of it to create a route. A carbon fiber braid increases torsional rigidity, while a Teflon sheath lowers friction. The robot can move beneath the surface since its movement is pneumatically propelled by compressed air or nitrogen.
Naclerio admitted that he had never heard of the Tremors Graboids (although the Sandworms of Dune are another story.) While the robot was clearly inspired by nature, it did not appear to be patterned on worms or snakes.
“Our robot is directly inspired by plant roots, which grow from their tips to extend deep into the soil,” said Naclerio. “By extending from its tip, the robot avoids friction along its sides, and can turn in any direction. We also took inspiration from the southern sand octopus which expels a jet of water to help burrow into the seafloor. Our robot blows air from its tip to fluidize the sand near its tip, reducing the force it needs to burrow into the ground. Lastly, we used an asymmetric airflow direction and angled wedge at the tip of the robot to help control lift forces. This was inspired by the sand fish lizard, which uses its wedge-shaped head to help it burrow into sand.”
The team was able to overcome the “challenge of lift” in horizontal burrowing thanks to this one-of-a-kind design. “When we first tried to burrow horizontally, our robot always surfaced,” he continued. “It turns out that a symmetric object moving horizontally through a granular media experiences lift, because it’s easier to push material up and out of the way than it is to compact it down. We addressed this by blowing air straight down, to reduce the strength gradient that causes lift, and by adding [the] wedge to the tip of the robot.”
So, what may this burrowing snake/vine robot’s uses be? Could it, more importantly, be scaled up to move vast amounts of sand or earth? “We believe that the principles presented in this paper could be used to expand the capabilities of conventional burrowing methods, particularly in horizontal and steerable burrowing,” added Naclerio.
It may seem far-fetched to use this technology to study low-gravity conditions in space. However, the team is currently working with NASA on a project that will address some of these specific applications. Who knows, maybe worm robots in space aren’t as insane as they seem!