Science-fiction fans have long become accustomed to the idea of steely commandos clad in robotic exoskeletons taking on huge, vicious, extraterrestrial beasts, shadowy evil cyborgs, or even each other. Supersoldiers encased in sleek, self-powered armor figure memorably in such works as Robert A. Heinlein's 1959 novel Starship Troopers, Joe W. Haldeman's 1975 The Forever War, and many other books and movies. In 1999's A Good Old-Fashioned Future, for example, Bruce Sterling writes of a soldier dying after crashing in his "power-armor, a leaping, brick-busting, lightning-spewing exoskeleton."

Today, in Japan and the United States, engineers are finally putting some practical exoskeletons through their paces outside of laboratories. But don't look for these remarkable new systems to bust bricks or spew lightning. The very first commercially available exoskeleton, scheduled to hit the market in Japan next month, is designed to help elderly and disabled people walk, climb stairs, and carry things around. Built by Cyberdyne Inc., in Tsukuba, Japan, this exoskeleton, called HAL-5, will cost about 1.5 million yen (around US $13 800).

Meanwhile, in the United States, the most advanced exoskeleton projects are at the University of California, Berkeley, and at Sarcos Research Corp., in Salt Lake City. Both are funded under a $50 million, five-year program begun by the Defense Advanced Research Projects Agency, or DARPA, in 2001. During the past several months, each group has been working on a second-generation exoskeleton that is a huge improvement over its predecessor. Little information about the new models had been officially released by press time, but IEEE Spectrum has learned that the Berkeley unit was successfully tested in a park near the campus this past summer and the latest Sarcos model was demonstrated to a panel of military observers at Fort Belvoir, Va., last April.

HAL-5, in Japan, and the systems by Berkeley and Sarcos, in the United States, appear to be the first of a platoon of considerably more capable exoskeletons aimed at real-world uses that may soon, quite literally, be walking near you [see tables of exoskeleton projects "Projects in the United States", "Projects in Asia" and "Projects in Europe"]. Most of these systems are designed to help physically weak or injured people gain more mobility or perform rehabilitation exercises. But researchers are quick to mention other commercial possibilities for their creations: rescue and emergency personnel could use them to reach over debris-strewn or rugged terrain that no wheeled vehicle could negotiate; firefighters could carry heavy gear into burning buildings and injured people out of them; and furniture movers, construction workers, and warehouse attendants could lift and carry heavier objects safely.

At long last, exoskeletons, the stuff of science fiction, are on the verge of proving themselves in military and civilian applications. Strap-on robotic controls for the arms and hands—used to remotely operate manipulators that handle nuclear material, for example—have been around for quite a while. But the new anthropomorphic, untethered, and self-powered exoskeletons now strutting out of labs aren't just a bunch of wearable joysticks. They marry humans' decision-making capabilities with machines' dexterity and brute force. They've got the brains to control the brawn.

Biologically speaking, an exoskeleton is the hard outer structure of an insect or crustacean that provides support or protection. But in military research labs, popular fiction, and movies, the term has come to mean a "supersuit," a system that can greatly augment a person's physical abilities.

Now, if exoskeletons are so attractive, why aren't ports, construction sites, and warehouses—not to mention war zones and nursing homes—teeming with them? The reason is that the basic technologies haven't been available. Indeed, all attempts to build exoskeletons in the United States failed until recently. At General Electric's facilities in Schenectady, N.Y., in the 1960s, engineers built a two-armed, bipedal exoskeletal machine dubbed Hardiman, but they could only get one arm to work. At Los Alamos National Laboratory, in New Mexico, in the mid-1980s, scientists envisaged the Pitman suit, a full-body exoskeleton for the infantryman, but it stayed on the drawing board. And at the U.S. Army Research Laboratory at the Aberdeen Proving Ground, in Maryland, in the early 1990s, researchers planned to build a suit that bore some resemblance to the comic-book hero Iron Man; the project never went forward.

These efforts ran into fundamental technological limitations. Computers weren't fast enough to process the control functions necessary to make the suits respond smoothly and effectively to the wearer's movements. Energy supplies weren't compact and light enough to be easily portable. And actuators, which are the electromechanical muscles of an exoskeleton, were too sluggish, heavy, and bulky. "Exoskeletons were always thought of as—you just can't do it," says John A. Main, manager of DARPA's Exoskeletons for Human Performance Augmentation program and a mechanical engineering professor at the University of Kentucky, in Lexington.