British researchers aim to make aircraft the size of a bee that could be used to spy inside buildings or monitor dangerous environments such as nuclear reactors.
The micro-aircraft would weigh between 5 and 50 grams (2oz), take their power from tiny batteries and use methods adapted from natural bird or insect flight to propel themselves, Dr Ismet Gursul, head of the aerospace sub-group at the University of Bath's department of mechanical engineering, said.
The work is being carried out with funding from the Ministry of Defence. "The idea is that they would be able to fly into buildings some distance away and report back," Dr Gursul said. "Ideally, you would want it to come back to base, but the idea is that it will be so cheap to make these that if you lose one then you haven't invested millions of pounds in it."
The idea has been pursued by US military strategists for more than a decade. Such micro-aircraft "will save lives" by removing the need to put pilots in danger, said Major John Cane, who is overseeing the development of the Dragon Eye at the Marine Corps Warfighting Lab in Quantico, Virginia.
Many projects to make unpiloted aircraft have run into the problems of making the aircraft small enough to avoid detection, light enough to fly, and with sufficient battery power to reach their targets. But now they are beginning to break through those limitations, using new knowledge about how insects flap their wings, allied to lighter, stronger materials and tiny cameras. Prototypes are now being used in some military applications.
In the US, a company called AeroVironment has demonstrated a tiny fixed-wing aircraft called the "Black Widow" that weighs just over 50 grams and measures 15cm (6in) across its wings. That can fly at up to 40mph, beam back live video, and fly up to 1.8km (more than a mile).
Dr Gursul, who is working with an eight-strong team, said there was plenty of room for progress. "The larger the aircraft, the more difficult it is to make it fly because you have to move larger surfaces," he said. "At small sizes the aerodynamics are very different, so we are looking to learn from the flight of bees and dragonflies."
Battery capacity is another problem. Dr Gursul said that most current systems "can only fly for 10 to 15 minutes. You need more power to get further."
To succeed, the project will need to master nanotechnology fabrication techniques: making materials which bond almost at the atomic scale.
The department plans five research projects over the next two years, funded by the Ministry of Defence, BAE Systems, the Engineering and Physical Sciences Research Council and the US Air Force Office of Scientific Research.
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