On the big screen, films like Robocop, Universal Soldier and forthcoming release Iron Man show man-machines with superhuman powers. But in Utah they are turning science fiction into reality.
We are at a research facility on the outskirts of Salt Lake City, ringed by beautiful snow-capped mountains. Once they held the Winter Olympics here; now they are testing endurance in other ways.
The aluminium limbs gleam in the brilliant sunshine, as the strange metal skeleton hangs from a safety harness at the outdoor testing site. It seems to be treading water; actually its programme is telling it to keep the hydraulic fluid in its joints moving.
Rex Jameson, a software engineer here at laboratories run by Sarcos, the robotics firm which designed the XOS exoskeleton, steps up and into the suit.
Stephen Jacobsen, Sarcos
The lightweight aluminium exoskeleton, called XOS, senses Rex's every move and instantly moves with him; it is almost like a shadow or a second skin. It is designed for agility that can match a human's, but with strength and endurance that far outweigh our abilities.
With the exoskeleton on and fully powered up, Rex can easily pull down weight of more than 90 kilos, more than he weighs.
For the army the XOS could mean quicker supply lines, or fewer injuries when soldiers need to lift heavy weights or move objects around repeatedly. Initial models would be used as workhorses, on the logistics side.
Later models, the army hopes, could go into combat, carrying heavier weapons, or even wounded colleagues.
The XOS in action
There are still problems to solve, not least how to create a mobile power supply that can last an effective length of time.
But the US military expects to take delivery of these early prototypes next year, and hopefully deploy some refined versions within eight years.
It is a long way off before we see robot soldiers that can fly or fire missiles - like in the movies - but the designers are already imagining future versions more reminiscent of Hollywood.
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