Vulture Heads for
Full-Scale Demo: "Improbable as it sounded when first kicked off, DARPAs Vulture program to demonstrate technology for an unmanned aircraft able to stay aloft, uninterrupted, for at least five years is finally moving into Phase 2 - flight demonstration of a vehicle that will be the size of the objective system, but with an endurance of a minimum 30 days - long enough to show it can stay on station at extreme latitudes through the winter solstice, when sunlight is at its minimum.
Concept: Lockheed Martin (click on image to enlarge)
Aurora Flight Sciences, Boeing/Qinetiq and Lockheed Martin completed Phase 1 conceptual design work, and Vulture had been expected to progress to the next phase before now. But Aurora threatened to protest when it was not selected, and DARPA decided to re-open Phase 2 to competition.
The goals of the new $155 million 'Vulture II' program include flying a full-scale demonstrator with the same wing span and aeroelastic responses as the objective system. That's important because, as the in-flight disintegration of NASA's Helios solar-powered long-endurance UAV in 2004 showed, maintaining the integrity of large lightly-loaded structures is a technical challenge.
DARPA expects bidders to propose solar-electric UAVs, as studied in Phase 1, The Vulture demonstrator goals are to carry a 200lb, 1kW payload for a minimum 30 days (objective 90+ days), and keep station by maintaining a minimum westerly airspeed of 28m/s through the winter solstice at a design latitude of 35deg. The objective system would carry a 1,000lb, 5kW payload and stay aloft for 5-10 years at latitudes up to 40-45deg.
Concept: Aurora Flight Sciences (click to enlarge)
Phase 1 concepts included Aurora's Odysseus - three UAVs that dock in flight to form a single vehicle that assumes a Z-wing shape during the day, to maximize solar-energy capture, and folds flat at night, to minimize drag and preserve battery power. Boeing's design is essentially a scaling up of Qinteq's Zephyr, while Lockheed's is designed to be carried aloft under a balloon and released."