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44 A s processors and electronics continue to shrink in size, many unmanned aerial solutions are also becoming smaller (and lighter). The perception of unmanned aircraft as unwieldy devices requiring their own aviation infrastructure has been dispelled over time by the utility gained from using them as tools that can be quickly deployed, recovered and stowed away. Naturally, this raises further concerns about how to structure regulations to maintain or improve aviation safety while allowing unmanned vehicles to reach their full potential, particularly as technology continues to grow that potential at an accelerating rate. Persistent operations Project AlphaLink is centred on an alternative design approach to high- altitude long-endurance (HALE) unmanned aircraft, and aims to tackle a key problem with typical approaches to ‘pseudo- satellite’ aircraft construction. Its solution involves the use of multiple smaller solar-powered aerial systems that would be launched as separate vehicles before connecting and locking onto each other, wing to wing, while in flight. This would then approximate the high aspect ratio solar airfoil of other, single- wingspan-body HALE configurations. “Current solutions are built mainly on aircraft designs with a single-wingspan body, with a very long span to reduce the drag,” says Dr Daniel Cracau of Project AlphaLink. “The problem with this approach is that when you pull up a very long wing relative to the wing chord, you habitually run into some structural problems. Chiefly, the more the wing extends from the centre of gravity [CoG] and the propulsion source, the greater the bending moment on the wing that occurs. “Additionally, you risk making the wing structure less stiff, potentially leading to increased oscillation unless you enhance the structure, such as by integrating more ribs or shifting more mass into the wing spar. With the resulting heavier aircraft, you need to angle the craft more to generate more lift, which then has the effect of increased lift-induced drag. “And by having each aircraft with its own CoG and propulsion source, the Advances in a range of technologies are enabling UAV designers to develop ever-smaller craft. Rory Jackson reports Size matters August/September 2018 | Unmanned Systems Technology Project AlphaLink aims to solve the issue of excessive bending moments in HALE UAV wingspans by launching multiple small vehicles and coupling them in mid-air (Courtesy of Project AlphaLink)