NASA flexes its artificial muscles

When the MUSES-C mission spacecraft reaches the small near-Earth asteroid 4660 Nereus and begins its landing sequence sometime in 2003, it will drop a palm-size nanorover to the surface before touching down. This small NASA vehicle will view the surface with both a visual and an infrared camera. NASA scientists anticipate that, from time to time, dust will accumulate on the viewing window. To forestall viewing difficulties, they plan to install two tiny windshield wiper mechanisms Mounted on each side of the viewing window to wipe away the dust. Weighing less than 18 mg, each mechanism will have to rely on tiny artificial muscles about 13 mm long for movement. About 0.2 W of power applied to the muscles will cause them to contract or extend and move the wiper blades to clean off the window. This tiny vehicle, called MUSES-CN (the N indicates it was built by NASA), will be the smallest rover ever to fly on a space mission. The diminutive robot has a mass of about I kg and carries instruments that observe in both the visual and near-infrared wavelengths. Its window wiper system will provide the first space test for artificial muscles. Success with these muscles could lead to space robots with animal-like flexibility and manipulation ability. The wiper blade, which is being built by Energy Science Laboratories (ESLI) in San Diego, Calif., is made of lightweight conductive material (aluminum and graphite) with a fiberglass microhair brush. Finger-like function The artificial muscles have been under development by Yoseph Bar Cohen of NASA-JPL for the past three years. They are based on a simple, lightweight strip of highly flexible plastic that bends and functions much like human fingers when electrical voltage is applied to it. Bar Cohen and a small team of scientists and engineers in the U.S. and Japan are working to turn these strips into grippers and strings that can grab and lift loads, among many other potential uses. Known as artificial muscles or electroactive polymers (EAPs), these strips and strings could greatly simplify robotic spacecraft tasks. Conceivably, these devices could replace damaged human muscles. "My hope is someday to see a handicapped person jogging to the grocery store using this technology, employing A dust wiper employs an ESLI-designed blade actuated by a bending EAP to remove dust from window. a joy stick to operate his leg," says Bar Cohen, leader of JPL's Nondestructive Evaluation …