The military problem
Foot soldiers have carried heavy loads for as long as there have been armies, and modern equipment such as body armor, radios, water and ammunition can add up to a heavy burden over long distances. Excess load is associated with fatigue and with injuries to the back, knees and feet. A wearable machine that took some of that load, or let a soldier keep up a strong pace, has therefore been an attractive goal for defense planners for well over half a century.
Hardiman and the 1960s
The earliest well-known military-backed exoskeleton was Hardiman, developed by General Electric in the second half of the 1960s with U.S. Army and Navy interest. The engineer Ralph Mosher is most often named in connection with it. It was a master-slave design, in which an outer frame followed an operator’s motion and multiplied it. The result was extremely heavy, and by the accounts usually cited it never functioned as a complete, safe, walking suit. The project is remembered as an early demonstration of both the promise and the difficulty, and it ended without a deployed product.
Science fiction of the same era, including Robert Heinlein’s 1959 novel Starship Troopers, popularized powered armor. How closely real engineers followed it is uncertain, but the image shaped public expectations of what the technology should do.
DARPA’s performance augmentation program
After a long quiet period, the U.S. Defense Advanced Research Projects Agency began a program on exoskeletons for human performance augmentation around 2001. The goal was a suit that would let a soldier carry heavy gear with less effort, and it funded several teams. At the University of California, Berkeley, Homayoon Kazerooni’s group built a suit often called BLEEX, which carried its own power and could support a load while the wearer walked. A company called Sarcos worked on a full-body design, and Berkeley technology was later licensed and developed by Lockheed Martin into a load-carrying system known as HULC.
Test results from this period suggested that suits could reduce effort in some conditions, but there were consistent difficulties. The power source added weight and limited endurance. Hydraulic systems could be loud, which is a drawback for soldiers who need to avoid detection. Rough ground, mud, water and dust were all harder than a flat laboratory floor.
Lighter ideas and Warrior Web
The experience prompted a shift in thinking. If a heavy powered frame could not be made practical, perhaps a lighter system could help in smaller ways. Around 2011 DARPA started a program called Warrior Web to develop light undergarment-style systems that could reduce injuries and fatigue. The work contributed to research on soft exosuits and to understanding of how people use energy while walking with loads. The aim was more modest than superhuman strength: reduce injury risk and strain.
TALOS and the limits of the dream
A more ambitious program was announced in 2013 by the U.S. Special Operations Command: the Tactical Assault Light Operator Suit, abbreviated TALOS. It envisioned a suit offering armor, sensors, communications and powered assistance. Prototypes were developed and demonstrated in parts, and several industrial and academic partners took part. Publicly, the effort was later wound down without producing a fielded suit, partly because integrating all the planned features into a single wearable system proved too difficult. Details of what was tested are limited, so any account is necessarily incomplete.
Other uses within the armed forces
Not every military project aimed at combat. Defense agencies and several armed forces have explored passive and powered exoskeletons for logistics and maintenance work, such as lifting heavy items or holding tools. These applications avoid some of the combat problems: workers operate in controlled settings and can recharge power. Some of this work overlapped with commercial products, a movement discussed in the history of commercial exoskeletons. Military-funded research has also contributed to rehabilitation devices, as some knowledge developed for soldiers fed into medical products.
Why the gap remained
Looking across the decades, several recurring problems explain why prototypes seldom became standard equipment:
- Power: batteries and fuel limit how long a suit runs, and carrying spare power adds weight.
- Weight and fit: a suit that weighs more than it saves is of no use, and it must fit different bodies and move naturally.
- Reliability: field conditions are harsh, and a failed suit becomes dead weight.
- Cost and training: new equipment must justify its price against simpler options, such as better-designed packs.
- Safety: a suit that moves strongly could hurt its wearer if control fails.
Improvements in lithium-ion batteries, electric motors and sensors have eased some of these constraints, but not all. A current assessment, necessarily cautious because much information is not public, is that exoskeletons remain mainly experimental in combat roles, and more established in logistics and rehabilitation.