DALLAS -- Wearable machines that enhance human muscle power are poised to leave the realm of science fiction and help factory workers hoist heavier tools, lighten soldiers' loads and enable spinal patients to walk.Lockheed Martin and Parker Hannifin are joining a handful of startups in finding practical uses and, more important, paying customers for bionic suits inspired by novelist Robert Heinlein's 1959 Starship Troopers and Stan Lee's Iron Man comic-book character.Sales of mechanical exoskeletons cap decades of scientific tinkering that included a 1,500-pound General Electric clunker in the 1960s. Strapped to users' bodies and powered by lithium-ion batteries, the emerging technology has led to some models that sell for about $70,000, weigh less than 50 pounds and are nimble enough to dance the Macarena."We're now seeing a golden age in which we can produce this technology and derive benefit from it," said Keith Maxwell, business development manager for Lockheed's program. "There's a host of industries where this works."The first commercial sale of a medical unit - not for lab or hospital tests - was in September, pioneering a field that may produce $400 million in annual revenue by 2020, according to technology consultant ABI Research. Lockheed says it hasn't estimated the value of any contracts for its under-development military version, known by the acronym HULC, or for the nascent industrial market its Mantis device will enter this year.The machines may follow a classic arc from Pentagon research project to fixture on an assembly line, similar to the development of lasers, said Paul Saffo, managing director of foresight at investment advisory firm Discern in San Francisco."The medical devices get the most attention, the military funds it and the first mass application is industrial," Saffo said in a telephone interview.Developing technology for both civilian and military use would be a boost for Lockheed, the world's largest defense contractor, as it confronts reductions in U.S. arms spending. Parker Hannifin, the biggest manufacturer of motion and control devices, is seeking to expand into the medical industry.Commercial exoskeletons are just echoes of Hollywood's take on Iron Man's bulletproof garb and the armor that Heinlein envisioned for his futuristic warriors.Ekso Bionics' device for spinal patients looks like the lower half of a black metal skeleton able to stand by itself on foot pads. Parker Hannifin's medical model breaks into five pieces and resembles elongated, plastic football thigh pads worn on the sides of users' legs.Human augmentationElectric motors amplify the strength in their wearers' limbs or, in the case of those who use wheelchairs, to supply motive power. Computers and sensors help provide balance and guidance."There's a huge wave of human augmentation coming," said Ekso Bionics CEO Nathan Harding, whose Richmond, Calif.-based company has devices in operation at New York's Mount Sinai Hospital, the Kessler Institute for Rehabilitation in New Jersey and other spinal cord injury centers. "It's in its infancy."Argo Medical Technologies entered the market last year, with an exoskeleton to assist patients who have lost the use of their legs. Parker Hannifin's Indego model also targets those users and will go on sale in 2014 at a price the company says is competitive with Argo's $67,230 unit.In between those introductions will come Lockheed's Mantis, which the Bethesda, Md.-based company envisions as finding a home in any industry in which workers must hold heavy equipment that can cause fatigue and back injuries.Mantis has a mechanical extension for a wearer's arm and absorbs the strain from hefting a grinder or sander, Maxwell said. Tests found productivity gains of more than 30 percent, he said, and wearers showed their Macarena footwork to demonstrate the suits' flexibility."It turns workers away from being a weightlifter and into a craftsman," Maxwell said.While Ekso Bionics' Harding sees exoskeletons on an evolutionary path toward ever-greater sophistication -- much as large portable phones of the early 1990s morphed into today's smartphones -- it may not be that easy to cut costs, simplify the technology and ensure widespread adoption."Even though there are processors and sensors, there's still a lot of physical matter that has to be machined and built," said Discern's Saffo, who is also a consulting associate professor at Stanford University's engineering school.The other limitation is battery life."Until you have higher-density power storage, you're always going to be looking for a plug for your exoskeleton," Saffo said.The exoskeleton industry is attractive because the potential is vast and the large competitors are few, according to Lockheed and Cleveland-based Parker Hannifin.Lockheed's HULCLockheed envisions a leap forward in battlefield mobility with its Human Universal Load Carrier - whose HULC acronym evokes images of Marvel Comics' Incredible Hulk, a green, superstrong mutant and sometime ally of Iron Man. HULC is intended to let a soldier lug a 200-pound pack with minimal effort over a 12.4-mile hike, Maxwell said.Back strain is the most common noncombat injury because of the heavy packs soldiers carry, Maxwell said. Lockheed licensed some technology from Ekso Bionics to produce the HULC, which is set to enter a second development phase this year as the system is refined so it can be worn under a uniform.Exoskeletons hold "tremendous potential" to ease those burdens, said David Accetta, a spokesman for the Army Natick Soldier Research, Development and Engineering Center in Massachusetts. A field demonstration is planned for May, he said by email. Lockheed said the program hasn't been affected by mandated budget cuts that began March 1.Parker Hannifin, which has been working with Vanderbilt University in Nashville, is targeting Indego at the estimated 700,000 Americans with spinal cord injuries, said Achilleas Dorotheou, the program's business unit manager.