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Developed for Darpa, the Leapp paragliders are slow-flying, long-endurance UAVs for surveillance and delivering payloads. The MicroLeapp version (below) is small enough to be carried in a backpack. Its big brother can carry up to a 250-lb payload and is powered by a turbo diesel engine. For a ground launch, soldiers unfurl the paraglider wing behind the vehicle. Takeoff is in 100 ft or less and need not be from a paved runway.

The servos run from a custom-designed motor controller using a potentiometer as a position-feedback device. The motor controller gets commands from a navigation-control computer that, besides a GPS unit, also contains a barometric sensor, three-axis gyro, three-axis accelerometer, and three-axis magnetometer. The navigation controller can make dead-reckoning calculations if the GPS blacks out or there is jamming.

The parafoils on Atair UAVs must be small and light. One development that makes such chutes practical is special superlight but superstrong material.

Conventional parachutes typically have wing loadings of 1 to 2 lb/ft². A 20ton tank would need a 40,000-ft² parachute, nearly an acre of material. But Atair parafoils get nearly 5 lb/ft² on wings that can generate positive lift in a flare maneuver, and 22 lb/ft² on wings that don't need to lift.

The material that makes this possible is a composite fabric created by bonding high-strength Dyneema fibers between two layers of ultrathin polymer. The material is three times stronger and less than one third the weight of standard parachute nylon. It also stretches just one-sixth as much.