Mechanical engineers at Vanderbilt University are showing off a working prototype of a prosthetic arm whose "monopropellant rocket motor system" allows it to lift up to 25 pounds, more than three times as much as today's prosthetic limbs.
The device, whose research and design was funded by the Defense Department, runs on a miniature version of the same motor system used to maneuver the Space Shuttle in orbit; the system works by mixing a chemical catalyst with hydrogen peroxide, producing steam, which is then pushed through a series of valves to cause the arm to move.
The researchers say their fuel system is superior to the traditional method of powering prostheses, batteries. Batteries are heavy relative to the power they produce; the rocket-powered arm, says Michael Goldfarb, the professor who led the team, produces more power with less weight than limbs that use other power sources.
The prototype also produces more natural movement that conventional prosthetic arms. Instead of two joints -- typical arms only move at the elbow and at the "claw" -- the new device has fingers that can open and close independently of each other, and a wrist that twists and bends.
The Vanderbilt engineers are competing with teams at several other universities and corporations in a program that the Defense Advanced Research Project Agency calls "Revolutionizing Prosthetics 2009," an effort to build an advanced bionic arm to help soldiers who've been injured at war perform the sort of daily tasks most of take for granted.