A HOVERING spy craft only 23 centimetres across could soon be flying behind
enemy lines to conduct surveillance, or darting about inside buildings to help
police find hostage-takers.
Micro Craft, an aerospace development company in San Diego, California, last
week successfully tested the miniature vehicle (www.microcraft.com/UAV01.htm).
It consists of little more than a ducted fan that rotates inside a protective
cylinder. The fan is pitched at an angle so that its wash counteracts the slight
spin the fan imparts.
鈥淚t performed great. It鈥檚 very stable,鈥� says programme manager Allen Zwan.
Even in high winds, the 1.4-kilogram craft managed to take off, hover, and move
around at slow and medium speeds.
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A small two-stroke petrol engine drives the fan. This provides enough lift to
get the craft off the ground and allow it to hover and move from side to side.
To travel at top speed, the vehicle turns sideways so that the fan points almost
horizontally and the aerofoil-shaped edges of the duct provide lift. It can fly
for about an hour on the 200 grams of fuel it carries. The aircraft was
developed with funding from the US Defense Advanced Research Projects Agency
(DARPA). The idea is that soldiers will carry the small, lightweight
reconnaissance aircraft in their backpacks.
A remote controller tells the drone where to go and how fast to fly. On-board
electronics keep the craft flying, adjusting the speed of the fan and the angle
of the control vanes. The test vehicle last week carried a video camera that
transmitted images back to the ground. But it could also support communications
relays, or even a laser that would 鈥減aint鈥� a target with light to guide in
missiles from larger craft.
