Floating in space in orbit around Earth are millions of pieces of debris.
This space junk ranges from specks smaller than a marble to old, defunct satellites. The question is: how do we clean it all up?
Enter Stanford University’s “gecko gripper,” a mechanical attachment for a robot that can grasp surfaces using adhesive inspired by the pads of a gecko’s feet. The technology could be especially useful in space for the unique fact that the gecko adhesive does not require any force to attach to a surface.
“The texture of it is too fine to see, but if you were to look at it under a microscope, you would see a forest of little tiny, sharp wedges,” explained mechanical engineering professor Mark Cutkosky, whose lab co-developed the gripper with professor of aeronautics and astronautics Marco Pavone. “Like the actual gecko itself, most of the time it’s not sticky. But when you pull in just the right direction it grabs and it grabs pretty hard. So that gives us a controllable adhesive.”
Previous tests of the gecko adhesive alone have shown it can withstand radiation and extreme temperatures in a vacuum, and that it can be manually attached to surfaces in the International Space Station (ISS). The full gripper headed up to the station in 2019 and this April, after waiting for its turn in the experiment line-up, astronauts carefully unpacked the gecko gripper, installed it on one of the station’s free-flying Astrobee robots and tested how it performs in a microgravity environment.
Upon sending the gecko gripper up to the ISS, Tony Chen, graduate student in the Biomimetics and Dexterous Manipulation Laboratory, was intensely aware that the team only had one shot to get it there in working order.
“Every step of the way it was exciting and nerve-wracking at the same time,” said Chen of the experience.
But even through the nerves and uncertainty one thought remained: “Oh man, I’m sending something to space,” he said.
NASA astronauts Kate Rubins, PhD ’06, and Victor Glover assisted with two rounds of testing on April 9 and April 15. For the duration of the experiment, the team had the gecko-inspired adhesive gripper installed on Astrobee. NASA plans to one day have the cube-shaped robot be a helper onboard, performing tasks such as taking inventory or retrieving items from other parts of the station. Currently, Astrobee is used as a platform for guest scientists to run their experiments aboard the ISS.
For the test, Chen and Abhishek Cauligi, a graduate student in the Autonomous Systems Lab, set up a ground station in Pavone’s lab. From there, Chen communicated with NASA while Cauligi spoke with the team controlling Astrobee. Using a live video feed, the researchers watched Rubins and Glover inspect the gripper and run the experiments. The tests included manually attaching the gripper to a surface to measure the force of its hold and attempting to have Astrobee fly to a wall and perch using only the gripper. Throughout the process, Chen and Cauligi gave feedback – such as whether the gripper was properly installed or when the astronaut could commence testing – which was relayed to the astronauts and Astrobee via their collaborators.
“We think gecko-inspired adhesives are a technology that can assist and augment the capabilities of astronauts, whether it be being able to pick up tools or record live astronaut activities,” said Cauligi. “The idea is to really be able to automate a lot of the activities that are done on board.”
Overall, the tests were successful, including one instance of Astrobee attaching to and perching upon the wall inside the ISS.
According to Pavone, this success is just the first stage in a three-phase plan of experiments to showcase the use of gecko-inspired adhesives in a variety of space-based applications focused on the eventual goal of cleaning up space.
“Now that we have mastered this capability we can move to the next phase,” he said, explaining that next they hope to add a perception capability to Astrobee so the robot can autonomously figure out where and how to attach itself to the wall.
After that, “The next big move would be to do all of that but outside of the International Space Station in the very harsh environment of space.”