Flying like a bat

The myth of Icarus revisited

Could the flight of the bat be of interest to the aeronautical industry? In Greek mythology, Icarus attempted to escape the palace of Knossos on the island of Crete by air, sticking bird feathers to his arms with wax. Flying too close to the sun, the wax melted, the feathers fell off one after another and he plunged into the sea. Just like this classical myth, the first “flying” machines flapped their wings, but all of them broke owing to one fact: man is too big to take off through the power of his arms alone, even if they are transformed into wings. In nature, moreover, there aren’t any birds of the size and weight of a human being (fossil birds such as the Argentavis weighed probably 80kg but it is not known if they could flap their wings or just glided) . By inventing the reciprocating engine, engineers found a sufficiently powerful method of propulsion for man to defy the earth’s gravity without flapping a pair of wings. All the studies in progress on the flight of birds, bats or insects are therefore of no use for the development of tomorrow’s aircraft, whether military or civil, a fighter plane or a transport plane. But the race for miniaturisation over the past few years has changed things. The standard aeronautical model, with static wings and propellers, is becoming less efficient as the size of the aircraft becomes smaller. And below a certain size, no object can fly efficiently without flapping its wings. Furthermore, in nature, the smaller the winged creature, the faster its wings have to flap to stay airborne: those of a large bird flap less than 10 times a second, while those of a hummingbird flap up to 80 times and those of a fly hundreds of times!

Bat Drone model

In the coming years, the development of drones could benefit from new research on wing flapping. Drones are small, pilotless aircraft that can perform military or civil tasks (territorial surveillance, spying, surveillance of polluted sites, etc.). The existing models are one to two metres long. But the drones of tomorrow may not be any bigger than a hand. And to develop such small drones, researchers have to reintroduce flapping wings into the design. Researchers working for NASA have thus developed an “entomopter”, a sort of large mechanical insect suitable for a trip to Mars, where the atmosphere has so little density that a traditional aircraft couldn’t fly. It would require wings ten times bigger than on earth and it would be impossible for a spacecraft to transport such an aircraft.

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