Meet the army's newest recruit

The US Defense Department is spending millions of dollars on the development of an exoskeleton for hi-tech combat. But, asks Owen Dyer, is this really the future of warfare?

It's nearly 500 years since the armoured knight was chased from the European battlefield by gun-wielding commoners. But if the US Army gets its way, the men in the iron pyjamas may soon be back, and this time they will have technology on their side. The US Department of Defense is currently handing out grants to develop powered suits of armour that boast superhuman capabilities.

"Exoskeletons for human performance augmentation" is the title that has been given to a research programme that seeks to enhance the infantryman's strength, speed and endurance. According to the programme outline, applicants looking for a slice of the $50m (£35m) research pie must design an outfit that will "increase locomotive speed, augment human strength, and leap extraordinary heights and/or distances." Like Superman, the wearer should be faster than a speeding bullet, more powerful than a locomotive, and able to leap tall buildings in a single bound.

On the face of it, the logic of the exoskeleton is impeccable. There are dozens of available technologies that can increase the infantryman's ability to fight and survive – night vision, satellite navigation using the global positioning system (GPS), chemical and biological protection, even electronic translators – but together, they are simply too heavy for one man to carry. An infantryman in a powered suit could carry all of this equipment, plus better armour and a bigger gun.

The proposed exoskeleton springs straight from the pages of science fiction. Robert Heinlein's 1959 classic Starship Troopers described a similar piece of equipment, with the additional accessory of backpack-launched nuclear missiles. The big screen has brought us Robocop, Star Wars' stormtroopers, and the famous final scene in the movie Aliens, in which Sigourney Weaver dons a powered, human-shaped forklift to shove the evil alien queen through an airlock.

In fact, Sigourney Weaver's suit bears a startling resemblance to the US military's last attempt to make a powered exoskeleton. Named Hardiman 1, this 1,500lb monster was developed by General Electric in the Sixties, but the project was soon abandoned. The inventors were unable to make more than one arm work, and any attempt to move both legs produced a "violent and uncontrolled motion".

Crude and dangerous as it was, Hardiman came closer to fruition than any of the current crop of projects has managed as yet. The exoskeleton project is being handled by Darpa, the Defense Advanced Research Projects Agency. This is the institution that gave birth to the internet in the Seventies. So far, they have awarded four major research contracts under the exoskeleton programme. One of these, at the University of California at Berkeley, has produced a legs-only model powered by a chainsaw engine.

Two other contractors, Oak Ridge National Laboratory and Utah-based Sarcos Research Corporation, have developed slave limbs of extraordinary strength. The Oak Ridge lab's device lets the user lift a 2,200kg bomb as if it weighed 4kg. But neither has produced a wearable suit. A fourth contractor, California's Millennium Jet Corporation, is working on a rotor-powered one-man flying harness.

The scientists working on these projects admit that production models are years away. Surprisingly, the flying harness is probably the closest to reality, precisely because it is not an exoskeleton, but a rigid frame. The developers do not have to worry about mirroring the fantastic complexity of human movement, and the control system relies on simple joysticks.

Exoskeletons are more difficult, because Darpa has specified that it does not want a machine that is controlled by buttons and levers, but a suit that reads muscle movements and translates them into mechanical motion. This is known as a "haptic interface". It has been used for years by remote arms for handling radioactive materials, but wearable body suits will require major breakthroughs in the field.

Among themselves, haptic interface researchers generally believe that external touch-sensing devices are less practicable than wiring the suit directly to the muscles' electrical signals. But the army doubts that the prospect of major surgery is likely to entice people to join up.

As well as the hardware issue, there is the thorny question of the control algorithm. A software model of human movement that works for every soldier will have to be phenomenally complex, and a minor bug could easily lead to broken bones.

All of these problems pale into insignificance compared with the question of the power supply. Ephrahim Garcia, the Darpa scientist co-ordinating the project, is the first to acknowledge that without a power supply significantly better than anything available today, the whole question of exoskeletons will remain academic.

The Army wants a suit that can operate autonomously for four to 24 hours. The chainsaw motor that powers Berkeley's lower extremity enhancer (Lee) runs for about 15 minutes on a one-litre tank of petrol. That's for a legs-only machine that doesn't provide the degree of strength enhancement that the army is looking for.

Add on the sensory and communications equipment a finished suit would demand, and the power problem becomes even more acute. Pound for pound, the internal combustion engine is the most efficient means of generating power, but it's a dead end for exoskeletons. One of Darpa's primary requirements is a silent power source. There's also the question of thermal signature and the problem of insulating the wearer from heat.

Some of the proposed solutions include chemical reactors, flywheels that turn at half a million revolutions per minute, and fuel cells feeding supercapacitors that can release bursts of energy. But none of these ideas is near fruition.

All of this begs the question of why the US army is so loudly trumpeting a gizmo that even optimists admit is decades away. Retired US army Colonel Daniel Smith, now a Washington defence analyst, doubts the exoskeleton can be an effective use of funds, since large numbers of soldiers will always be more effective than a few armoured supermen. He is also sceptical about Darpa's cost forecasts, which predict that this technological wonder will one day cost no more than a motorbike.

"I can see how it could have tactical uses. But it has to work first, and I don't think they can do it anytime soon. In any case, combat soldiers don't want extra weight. As soon as it's time to march or fight, the first thing they do is ditch this extra equipment."

Another military analyst, Edward Luttwak, is more scathing. "The people at Darpa aren't developers, they're projecteers. Most people, when they finish a research project, move on to tooling, debugging and production. At Darpa they say 'that was fun, what project shall we do next?' This exoskeleton idea comes from the Army Materials Command, who have a long tradition of ignoring the needs of the infantry. The soldiers have been asking for a load-bearing harness since Vietnam, and the AMC is just now issuing a few to one unit. Instead of improving the equipment people actually use, they come up every 10 years or so with some sci-fi, blue-sky project that belongs in the far future."

But the army may not be quite as clueless as it seems. It is faced with a chronic shortage of recruits, and those they get mostly want to avoid the infantry. Indeed, one of the reasons for the exoskeleton project is to get more mileage out of fewer infantry. But maybe a sexy armoured suit, or the promise of one, could actually help them keep infantry numbers up. A recruitment ad shows a soldier wearing what looks like a motorbike helmet and skateboard elbow pads, but the grainy image lets the imagination conjure up a Robocop outfit. It reads: "What you see is a soldier system that gives me 360 degree vision in pitch black. Makes me invisible to the naked eye. Lets me walk up a mountainside. And run in a desert. You've never seen anything like me. But don't worry. They haven't either. I am an army of one. And you can see my strength."

"The airforce offers hi-tech," says Col Smith, "the navy lets you see the world, and the marines have their élan. The army has always had trouble competing. Now they can say 'sign up with us and you can become a pseudo-Superman.' " Fifty million dollars in research grants is peanuts compared with the money disbursed in cash incentives for new soldiers. If this analysis is true, the exoskeleton is probably the first weapon created not to fight the enemy, but to stimulate recruitment.