Military tests rocket-powered bionic arm

A rocket-powered bionic arm has been successfully developed and tested by a team of mechanical engineers at Vanderbilt University as part of a $30 million military program to develop advanced prosthetic devices for next generation of super-soldiers.The mechanical arm mechanical arm with a miniature rocket motor can lift (curl) about 20 to 25 pounds, three to four times more than current commercial arms, and can do so three to four times faster. “That means it has about 10 times as much power as other arms despite the fact that the design hasn’t been optimized yet for strength or power,” Michael Goldfarb, the professor of mechanical engineering who is leading the effort, said.Tests show that the mechanical arm also functions more naturally than previous models.Conventional prosthetic arms have only two joints, the elbow and claw, but the prototype’s wrist twists and bends and its fingers and thumb open and close independently.The Vanderbilt arm is the most unconventional of three prosthetic arms under development by the Defense Advanced Research Project Agency (DARPA) program.The other two units, powered by batteries and electric motors, are being designed by researchers at the Advanced Physics Laboratory at Johns Hopkins University in Baltimore who head the program.The military is funding neuroscientists at the University of Utah, California Institute of Technology and the Rehabilitation Institute of Chicago who are developing advanced methods for controlling the arms by connecting them to nerves in the users’ bodies or brains.“Battery power has been adequate for the current generation of prosthetic arms because their functionality is so limited that people don’t use them much,” Goldfarb says. “The more functional the prosthesis, the more the person will use it and the more energy it will consume.” At a certain point, the weight of the batteries required to provide the energy to operate the arm for a reasonable period becomes a problem, and it was this poor power-to-weight ratio of the batteries that drove Goldfarb to look for alternatives while working on an exoskeleton project for DARPA.Goldfarb’s power source is about the size of a pencil and contains a special catalyst that causes hydrogen peroxide to burn produce pure steam which is used to open and close a series of valves.The valves are connected to the spring-loaded joints by belts made of a special monofilament used in appliance handles and aircraft parts and a small sealed canister of hydrogen peroxide that easily fits in the upper arm can provide enough energy to power the device for 18 hours of normal activity.By covering the hottest parts with special insulating plastic, they were able to reduce surface temperatures enough so they are safe to touch and the steam exhaust is vented through a porous cover, where it evaporates like natural perspiration.“The amount of water involved is about the same as a person would normally sweat from their arm in a warm day,” Goldfarb says.Goldfarb denies he is creating a superman for the military.“Our design does not have superhuman strength or capability, but it is closer in terms of function and power to a human arm than any previous prosthetic device that is self-powered and weighs about the same as a natural arm,” he said.Source: Press Esc

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