Rocket-Fuelled Bionic Arm not Just for Sportsmen

A team at Vanderbilt University has come up with a prototype of a prosthetic arm powered by a miniature rocket motor that is as close to a bionic arm as you are going to get. "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," says Michael Goldfarb, the professor leading the research. You can see more from him in the video below.

Conventional prosthetic arms do not have the strength of their flesh-and-blood counterparts, the reason being the batteries. In order to lift comparable weights, a prosthetic arm would need a massive battery, too large for the prosthesis itself. So Goldfarb started thinking about other ways to power the artificial limbs, and came up with the idea of using the monopropellant rocket motor system that the space shuttle uses to maneuver in space.

The first attempt used a "cold gas", compressed nitrogen, which allowed the researchers to test for control, leakage and noise of the arm, which consists of a series of valves and belts made out of a monofilament usually used in aircraft parts. Once fine-tuned, the engineers reworked the arm to operate on "hot gas," or steam that is heated to 450 Farenheit.

The arm even "sweats" when it is in use. In order not to burn the wearer, the steam is vented through a porous cover, where it condenses and turns into water droplets—about the same amount as the sweat from a person's arm on a hot day.

Last month, the engineers got the second prototype working properly, and the arm, which is part of a $30 million project funded by DARPA's Revolutionizing Prosthetics program, should make it to the second stage of development. But Goldfarb is not worried, should DARPA pull out. "We have made so much progress and gotten such positive feedback from the research community that I'm certain we'll be able to keep going," he says. [Exploration]