A group of researchers at Vanderbilt have built a mechanical arm that outperforms traditional battery-powered prosthetics the old-fashioned way: by strapping on a couple rocket motors. The arm, which the team built for DARPA's Revolutionizing Prosthetics 2009 program, relies on a modified miniature version of the same rocket motors the space shuttle uses to reposition itself in space: hydrogen peroxide is burned in the presence of a catalyst to produce pure steam, which is then used to move the arm. Unlike the batteries in traditional arms, which die quickly, a small canister of hydrogen peroxide concealed in the arm can last up to 18 hours, and provides about the same power and functionality of a human arm. Cooler still is the method the arm deals with waste heat and steam: just like a regular arm, it's allowed to filter up through a permeable skin, producing "sweat" -- the same amount of perspiration you'd get on a warm summer day, according to the team. Check a video of the arm in action at the read link -- it's even niftier than it sounds.