68 Insight | UAVs transport vehicle resembling a flying motorbike (one of two systems the company has in development). A second solution Electrafly is working on is a UAV intended to fly as far as possible while carrying as much weight as possible. Electrafly’s COO John Manning comments, “Batteries are essentially the Achilles heel of flight endurance. With gravimetric energy density being what it is, you quickly get diminishing returns when you repeatedly try to increase endurance by adding more battery packs. “And as bad as that problem is now, it was even worse 5 years ago when we first started r&d for a UAV, so we quickly decided we should create a hybridelectric system, replacing battery energy storage with fuel as potential energy. “On top of that, we’re planning to design our UAV with wing-like arm structures between the hub and rotors. Having those surfaces to generate lift for you is much more efficient than trying to sit on a pillar of thrust, as you would with a helicopter or multi-rotor.” In addition to combining fixed wings with distributed lift motors, the powertrain uses a small turbojet engine that burns fuel to generate forward thrust as well as drive an electricity generator via its shaft power, the latter enabling the battery to be recharged in-flight. Although it currently develops its prototypes as hybrid-electric, the company’s ultimate aim is to produce all-electric multi-rotor UAVs for delivering packages, with an engineering focus on maximising payload and range, and operating in urban environments of about 20 miles (32 km) in radius. Its propulsion systems in particular will be designed for bridging the endurance gap between longer range fixed-wing vehicles, and shorter range multi-copters. Coastal missions By their nature, naval vessels and their crews have to operate in dangerous locations that are prone to territorial disputes, piracy, traffickers and occasionally warfare. Creating UAVs fit for service aboard such vessels is hence a considerable challenge, as Alpha Unmanned Systems understands only too well. We previously visited the company in issue 20, (June/July 2018) to investigate its A800 UAV, a 14 kg, 1.7 m-long uncrewed helicopter capable of carrying 3 kg of payload for up to 2.5 hours. In the intervening 5 years, the Spanish OEM has unveiled the successor to the A800, which it calls the A900 UAV. It has a MTOW of just under 25 kg, a standard cruising speed of 60 kph, a maximum continuous cruise of 100 kph, and an endurance of up to 4 hours. “The A900 has been designed inhouse to comply fully with STANAG 4738, which means all critical onboard systems are redundant,” says Eric Freeman, CEO of Alpha Unmanned Systems. Some of the company’s new customers for the A900 include the Indonesian Coast Guard, the Spanish Air Force and the US DoD. Regarding the improvements in the A900 over its predecessor, Freeman says, “Many customers are finding that its 4 hours of autonomous flight time, the payload capacity of up to 4 kg and the ability to perform automatic take off from – as well as automatic landing on – a moving vessel can be particularly valuable in coastal and maritime survey work, among other applications.” The A900 also comes with an automatic autorotation capability, which enables it to ‘glide’ to safety in the event of an engine or rotor failure, something previously only trained helicopter pilots could perform. This, along with UAV Navigation’s Visual Navigation System (VNS01) which enables camera-powered geolocation in the event of GNSS failure or jamming, are further capabilities of the A900. August/September 2023 | Uncrewed Systems Technology The A900 from Alpha Unmanned Systems has an EFI system that can be reconfigured for running on gasoline or heavy fuels – a major draw for naval users (Courtesy of Alpha Unmanned Systems)
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