Robot Hand Powered by Rocket

The new rocket-powered robotic arm, shown in this diagram, is stronger and faster than the ones on the market. Here's how it works: The propellant cartridge contains pressurized liquid hydrogen peroxide, which is routed through two flexible lines (not shown) across the elbow joint and into two catalyst packs. The catalyst burns the hydrogen peroxide, generating steam that pushes pistons up and down — allowing the arm to move.

Michael Goldfarb, a professor at Vanderbilt University, has led the development of a prosthetic arm that, get this, is powered by miniature rocket motor systems! The fuel, hydrogen peroxide, is burnt in a catalytic reaction generating steam that opens and closes valves connected to the joints of the arm. The mechanical parts that make up the arm were precision machined to avoid any leaks. A small canister of hydrogen peroxide loaded into the arm provides sufficient energy to allow 18 hours of normal arm movement! At 450°F (232°C) one would think the super-heated steam would cause a tincy mincy discomfort to the user. Fortunately, the researchers thought of end-user comfort and insulated the really (really) hot parts of the arm. Look at the video.. the motion is quite amazing. The thumb and fingers are controlled independently. It probably sounds really cool too!

"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," said researcher Michael Goldfarb, a roboticist at Vanderbilt University in Nashville.
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 (project leader) Michael 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 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.