‘Flying saucer’ cleared for take-off

Written by: Tom Shelley | Published:

Tom Shelley reports on state of the art in saucer-shaped aircraft using the Coanda effect



A UK aeronautics specialist has developed a saucer-shaped aircraft that can take to the air without any of the stability problems that have bedevilled previous attempts to get this kind of vehicle to work.
Since it uses a ducted fan, it can be safely operated close to, or inside, buildings. And, because it uses the Coanda effect, it is aerodynamically efficient.
Intended applications are mainly as Unmanned Aerial Vehices for civilian, police and military work. However, unlike many of the plethora of UAVs presently on the market, it should also be relatively cheap to manufacture.
Engineers in different countries have been trying to get saucer-shaped aircraft to fly
successfully ever since the Second World War. Obvious advantages are vertical take-off and extreme manoeuvrability when aloft, as well as relatively small sizes. Machines have been built in the US, Canada and Russia, while model versions have been tried out in a host of other countries, including the UK. But controlling them, and keeping them stable in the air, has proved an immense problem. The best known, the Avro Avrocar, is said to have been beyond control when more than three feet above the ground.
The stability of the saucer-shaped UAVs being developed by GFS Projects of Peterborough is therefore quite remarkable. These machines, invented by Geoff Hatton – the GFS in the company’s name stands for Geoff’s Flying Saucers – have ducted fans on top, which blow air down over their curved outer surfaces to create lift by the Coanda Effect. Discovered by Romanian aerodynamicist Henri Marie Coanda in 1930, this is the tendency of fluid to stay attached to a convex surface, so that air blown down over the top of a saucer shape tends to be bent downwards over the periphery, lifting the machine. Also, because it is travelling faster than the surrounding air when it moves over the top surface, it has a lower pressure and creates lift, in the same way as an aircraft wing.
Hatton built hovercraft for many years. “They always had to go round an object, but I wanted to go over it,” he says. “However, it has taken more than 20 years to get from thought to product. From first model to making it fly properly has been a seven-year trip.”
GFS Projects started its current development programme in 2002, supported by a DTI Smart grant award and a group of private investors. The aerodynamic formulae were developed by Dr Holger Babinsky in the Aerodynamics Group in the Acoustics, Fluid Mechanics, Turbomachinery and Thermodynamics Division of the University of Cambridge Department of Engineering. GFS Projects has five patent applications in place and anticipates filing many more.
Eureka watched a 600mm diameter prototype being flown round one of the quadrangles at Churchill College. The machine had anti-torque vanes all round, plus two sets of vanes for yaw control on opposites sides and four flaps extending downwards, positioned at the four points of the compass. It looked very stable. A 2kW brushless motor, using power supplied by seven 2200mAh 7.4V lithium polymer batteries – providing a maximum theoretical endurance of just over three minutes – powered the model. Maximum payload is about 0.5 kg.
“We want to get into internal combustion engines,” says Hatton, the intention being to increase endurance. “We now need to engineer and carbon fibre it. We are still at least two years away from commercialisation.”
Meanwhile the company and its partners in Team Mira have been selected as one of six teams to receive funding for the Ministry of Defence’s. Grand Challenge Programme. The Team, led by Mira, is a consortium comprising GFS Projects, BAE System ATC, ERA Technologies, Warwick University and Guildford High School. The Grand Challenge aims to produce an autonomous or semi-autonomous technology system that can detect, identify, monitor and report a comprehensive range of physical threats in a complex urban environment. There are four categories of targets: an improvised explosive device; a sniper; a 4x4 vehicle with a gun on it; and foot soldiers dressed in semi-military uniform carrying arms.
The challenge culminates in a grand finale in August 2008 at Cope Hill Down, a bespoke uninhabited training village on Salisbury Plain. The mock-up settlement, originally built during the Cold War, will be swept by each of the teams for possible threats. The competition winner will receive the R J Mitchell trophy, named after the father of the Spitfire fighter, and a potential follow-on contract to conduct further proving tests on its design against MoD requirements. More information from www.challenge.mod.uk
GFS Projects is also in discussion with the agricultural market about how the UAV could be used to undertake airborne spectral analysis of plants in fields. The idea, which was extensively researched by Silsoe Research, among others, is to establish which crop plants need fertiliser, and where weeds and pests are so that fertiliser, herbicides and pesticides can be applied selectively, reducing waste and costs, and minimising chemical impact on the environment.
A version of the saucer that can support the weight of a human being – it would need to be about 10m across – is a real possibility.

Pointers

* The UAV currently exists as a 600mm diameter electric-powered prototype

* It is now completely stable in the air and flies without problem in wind speeds up to 10mph, but maximum duration is currently only just over three minutes

* Its main advantages over small helicopters are its higher stability, ease of control, and simplicity of construction and maintenance. Its flight is also not terminated, if it touches the side of a building


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