Most Unmanned Aerial Vehicles (UAVs) employ a fixed wing design like that of a traditional plane. But these designs offer limited maneuverability and payload capacity, require a runway to takeoff and land, and are unable to hover. Vertical Take Off and Landing (VTOL) UAVs get around these problems, usually by employing rotors like a helicopter. Now UK-based company AESIR has developed a VTOL UAV that has no external rotating parts, instead relying on a phenomenon known as the Coanda effect to generate lift.
The Coanda effect is the tendency of a fluid jet to become ‘attached’ to a nearby curved body instead of following its original path. The effect can be seen by placing a can in front of a lit candle. If you blow directly at the can, the air will bend around it and extinguish the candle – that’s the Coanda effect. It was used in the design of the pedal powered submarine we looked at earlier this year and, because the fluid jet can be a liquid or a gas, AESIR have been able to utilize the effect in the UAV.
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The DesignIn the case of the AESIR UAV, air velocity is created in the center of the craft using a fan and then directing the air flow through an outlet so it follows over the curved surface. The amount of lift generated is dependent upon the velocity, mass and density of the air. To help reduce the weight of the craft and maximize durability the craft are made from carbon fiber.
Since the rotation of the fan causes the body of the UAV to rotate in the opposite direction, AESIR placed a series of vanes in the airflow around the outside of the body to neutralize this effect. Moveable flaps on sections of the lifting surface provide yaw control to allow the UAV to turn left or right. And flaps on the outside of the craft use the lift airflow to provide directional control, causing the craft to tilt and move in the direction of the tilt.
AESIR say their designs have inherent stability as a surveillance platform, thanks to a sustained hover capability, and can survive low speed impact with the ground, buildings and other fixed objects. They also have a large payload capacity when compared to similar sized fixed wing craft and have been designed to be flexible using “plug-and-play” payloads.
The RangeThe AESIR family of craft range from a 300mm diameter craft called Vidar, through Odin which is a 1m diameter craft with a payload capability of 10kg, to Hoder which is a multi-engine craft with the capability to lift a payload of 1 tonne.
Vidar is a highly portable craft designed to provide surveillance and situational awareness inside buildings, and in close confined spaces. It has an electric engine powered by Lithium Polymer batteries to provide up to 15 minutes of flight time. It weighs 400g and is capable of carrying a 100g payload.
Odin is fitted with a Wankel Rotary internal combustion engine fueled by JP-8 jet fuel. It weighs 10kg and can carry a 10kg payload for up to an hour. Fitted with an autonomous flight control system and managed through a simple to operate ground control system, it can be adapted to a range of tasks including Intelligence, Surveillance, Target Acquisition and Reconnaissance (ISTAR), communications relay and electronic warfare, asset protection, IED detection and can be used as a weapon or loitering munition.
Hoder is a heavy lift craft that weighs 1.5 tonne and is capable of carrying a one tonne payload for up to eight hours. It is primarily intended for cargo transport and resupply vehicle for front line forces, but can be adapted to become a long endurance craft by reducing the payload and increasing the fuel. Hoder is in the early stages of development but AESIR expect that it will be multi-engined.
AESIR’s Marketing Director Mark Broughton told Gizmag that the company has initially targeted its range of VTOL UAVs at the defense market, but plans to explore civil and commercial markets in the coming weeks.
AESIR was exhibiting its wares at the Defence Systems and Equipment International Exhibition 2009 (DSEi) in London earlier this month. Given that the VTOL UAV’s have applications beyond the military, it may not be long before there's an explosion in UFO sightings that can be attributed to the AESIR craft.