Gripping technology inspired by the force that geckos use to climb even vertical, smooth surfaces has been tested in microgravity. Researchers want to see if it might one day be used to get work done in outer space, and clean up the increasing amount of debris floating in orbit around the Earth.
"The system could grapple objects in space that are spinning or tumbling, and would otherwise be hard to target," said Aaron Parness, NASA's principal investigator for the grippers. Parness was in graduate school at Stanford in the program that tested early prototypes of the gripper technology. It was put through over 30,000 "on" and "off" cycles without losing its adhesive strength.
Gecko feet have branched systems of tiny hairs that use a type of molecular attraction known as the van der Waals force to stick to a surface with minimal effort, and can easily turn the force on or off. The grippers are not an exact replica of the structures on actual geckos' feet, but they have synthetic hair structures called stalks that mimic the real thing. The tip of each stalk basically acts like a tiny suction cup. When force is applied to the stalks, adhesiveness is activated, whereas relaxing the force turns the stickiness off.
The temporary adhesive characteristics of the van der Waals force are credited to unevenly-spaced electrons creating a slight electrical charge, a phenomenon that occurs regardless of environmental variations in temperature, pressure or radiation levels. "The reliability of van der Waals forces, even in severe environments, makes them particularly useful for space applications," Parness said.
Earlier this year, researchers tested the grippers in weightless conditions aboard NASA's C-9B parabolic flight aircraft, where they were able to grapple not only a 20-pound (9-kg) cube as it floated around, but also one of the researchers wearing a special suit made of spacecraft material panels, standing in for a 250-pound (113-kg) object.
The grippers are being developed as part of NASA's Phoenix program, to work on new technologies that could allow for components from non-functioning satellites still in orbit to be harvested and re-used.
In addition to perhaps someday cleaning up and recycling components from some of the estimated more than 21,000 pieces of orbital debris larger than 10 centimeters, NASA says the grippers could also be helpful for inspecting spacecraft or helping small satellites dock with the ISS.
You can watch the grippers being tested under simulated weightless conditions in the video below.
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