By Lewis Page
Two rival firms in the USA are vying to develop military exoskeletons - powerful motorised robotic suits intended to endow soldiers of the future with superhuman strength and other abilities. The XOS inventors from Utah, generally seen as running second to California's HULC*, have now rolled out a new "second generation" version of their powered suit.
The XOS was originally developed by Salt Lake City firm Sarcos, now bought by US arms mammoth Raytheon. (The rival HULC super-soldier suit, now in tests with the US Army, was bought by Lockheed.) Company executives, showing off the XOS 2 in an event specifically timed to coincide with the release of Iron Man 2 on DVD, say the 2nd-gen XOS is lighter, faster and stronger yet uses 50 per cent less power. Flexible hoses have been replaced with hard hydraulic pipes, allowing an increase in pressure and greater efficiency.
“With the popularity of the Iron Man movies, people wonder if I feel like Iron Man when I suit up," said XOS test pilot Rex Jameson. "I usually tell them that I can’t speak for Tony Stark, but when I’m in the suit I feel like me, only a faster, stronger version of me. Given that his character lives in a California mansion and owns a stable of very fast race cars, that’s probably as close as we’ll come to a shared experience.”
According to Raytheon, the XOS "can do the work of two or three soldiers" when it comes to lifting and carrying heavy objects - more the sort of work intended for the exoskeletons in the film Aliens than the ones in Iron Man, in fact. Unlike the rival HULC, which offers only over-shoulder lifting straps to assist its wearers' arms, the XOS has fully powered and articulated upper limbs as well as legs and back.
But its greatest Achilles heel remains: the XOS still needs to be plugged into a trailing power cable to work. The designers' ultimate plan is to fit an internal-combustion engine, the only form of portable power potentially capable of running the XOS, but they admit that this is a long way off.
"With a tethered power source, you could likely see it [in service] within five years," says Sarcos veep Dr Fraser Smith. "For a suit that operates on its own power, it's probably more like a decade away."
It seems that the snag is the relatively low efficiency with which the XOS' hydraulics handle the power of the engine. At present, the engine needed to drive the suit is too heavy for it to carry usefully.
"XOS 2 uses 50 per cent less power than its predecessor, while doing more," says Smith, "and we believe we can get that power consumption down to 20 per cent."
Until then, however, the XOS will need to trail a power line behind it wherever it goes. Not so the rival Lockheed HULC, whose slimmed-down hydraulics are powered by li-ion batteries. Asked why he doesn't use li-ion, Smith said:
"We ruled it out because we believe they are extremely dangerous. If one gets breached, it can explode and cause a fireball that's similar to a magnesium flare. So we opted instead to focus on the internal combustion engine and explore ways to increase the efficiency of the utilization of hydraulic energy in the exoskeleton."
That's understandable, though high-pressure hydraulics are pretty dangerous things to be wearing too. And frankly, to a soldier who will routinely be carrying not just flares but grenades, ammo, handheld rockets etc, the danger from exploding or burning li-ion batteries might not seem a big deal.
All that said, li-ion may not be an exoskeleton panacea. The li-ion powered HULC suffers from limited endurance, and Lockheed have assigned funds to investigate ways of powering it using fuel cells.
In one respect at least, then, the Iron Man movies are accurate. It isn't so much the building of a powered exoskeleton suit that's hard, as both Raytheon and Lockheed have shown - it's the development of a power source both lightweight and puissant enough to drive it.
"Of course, if we had a real live version of an arc reactor, that time [to a mobile XOS] would be substantially compressed," comments Dr Smith mournfully.