Muscle Wires for Planetary-Exploration Robots

A report proposes the use of muscle wires as mechanical actuators for planetary-exploration robots. Muscle wires are commercially available in kit form in the hobby market, and have been described (though not explicitly called "muscle wires") in previous articles in NASA Tech Briefs. A muscle wire is made of a shape-memory alloy. By sending a sufficient electric current along the wire, one can heat the wire above its transition temperature, causing it to change length. When the current is turned off, the wire cools, returning to its original length. The aspects of muscle wires that make them attractive for planetary-exploration robots are low mass, simplicity, and the ability to exert large tensile forces (thousands of times their own weights); in these aspects, muscle wires are superior to conventional electric motors. Moreover, because of their low thermal masses, muscle wires would respond to turn-on and turn-off of currents rapidly enough for the actuation frequencies needed in planetary-exploration robots.