The human body is unsurpassed in the complexity of its design, performance and efficiency, but there are definite limitations to what we can achieve with a frame that's around 6ft high - we can only carry so much weight, jump so far or run so fast before we reach our physical boundary. Machines that overcome these limitations have been with us for centuries, but we are only beginning to explore the possibilities of augmentation - extending our existing capabilities through wearable robot exoskeletons to create superhuman strength, speed and stamina.

In a push to turn the science fiction of exoskeletons - like the one used by Sigourney Weaver in Aliens - into a military reality and deliver the advantages of such technology to soldiers in combat environments, the US Defense Advanced Research Projects Agency (DARPA), is funding a US$50 million project known as "Exoskeletons for Human Performance Augmentation".

The scope of the program includes the development of actively controlled exoskeletons that not only increase strength and speed, but enable larger weapons to be carried, provide a higher level of protection from enemy fire or chemical attack, allow wearers to stay active longer and carry more food, ammunition and field supplies. Exoskeletons may eventually even be programmed to bring injured soldiers back to base by themselves.

Systems will range from un-powered mechanical devices that assist a particular aspect of human function to fully-mechanised exoskeletons relying on chemical or hydrocarbon fuels for totally independent operation by soldiers in the field.Several different projects under the DARPA umbrella are underway including SARCOS Research Corporation's Wearable Energetically Autonomous Robots (WEAR). Designed for on-foot combat, WEAR will include a base unit configured like legs, torso and arms that mimic human movement using complex kinematic systems and contain energy storage, power systems, actuators and everything needed for an autonomous wearable system.

ASP's (Application-Specific Packages) will provide additional protection against specific threats like radiation and biological agents or give expanded functionality for communications, surveillance or night operations. SARCOS is on track to have a legs only version of the exoskeleton ready for trial by 2003 and a working full-body prototype is expected around 2005.

The problems of actuation, power supply and energy storage are being tacked on several fronts with M-DOT Aerospace working on a META(Mesoscopic Turboalternator ) engine capable of acting as a viable electric power source for human exoskeletons and Quoin International developing a unique power supply and actuation system for anthropomorphic exoskeletons using hydrocarbon fuels and high-pressure pneumatic systems to mimic human movement.Adding flight to the equation, Millenium Jet's Solo Trek XFV (Exo-skeletor Flying Vehicle) is another DARPA associated project that will deliver exceptional three-dimensional transportation for individuals in combat situations.

The VTOL SoloTrek has a range of 200 kilometres, a cruising speed of 70 knots and is able to hover dead still at any altitude up to a maximum of 8000 metres. Delivery of a working unit for field testing by the US military is expected in late 2003 and the advantages combined with a small footprint and shrouded rotor blades gives access to tight spaces and makes the SoloTrek - like many other wearable robotics devices - suitable for an array of potential non-military applications from search and rescue to herding livestock on large properties.

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