Future Drones Will Fly as Silent as Owls, as Steady as Bees

Want to know what drones of the future will look like?

So does David Lentink, editor of Interface Focus, a journal that, as its title suggests, looks at the interface of different scientific disciplines. Each issue zeroes in on a particular intersection of physical sciences and life sciences and invites the world's top scholars to publish their latest work.

The latest issue of Interface Focus brings together biologists and engineers to discuss a topic that's relatively straightforward and, well, pretty empirically cool:

"It's completely focused on how animals fly and how that can help us build flying robots," said Lentink, assistant professor of mechanical engineering at Stanford.

Can't argue with that.

The new issue features 18 newly published papers on various ways that engineers are borrowing ideas from nature to make the next generation of drones and aerial robots. Several of the papers detail prototype drones that have already been built and tested.

For instance, the bio-inspired drone pictured below uses synthetic feathers that make it easier to fly and maneuver in high winds. Designed by a team of researchers at EPFL's Laboratory of Intelligent Systems, the drone can dodge obstacles, make sharp turns and move through tight spaces by dynamically altering its wingspan in flight.

"We were inspired by birds," said researcher Matteo di Luca in press materials. "They can radically transform the size and shape of their wings because they have an articulated skeleton that is controlled by muscles and covered in feathers that overlap when the wings are folded."

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The drone's synthetic wings do much the same, folding and overlapping like a fan depending on conditions. This could make the drone particularly good at flying among skyscrapers in urban environments where winds change rapidly.

Another prototype drone, from Imperial College London, is inspired by waterfowl who can dive from significant heights into water, grab a fish, and then fly back out again.

The AquaMAV - or Morphing Aquatic Micro Air Vehicle - is also able to dive directly from the air into water at high speeds. According to the paper abstract, the real trick is getting back into the air: "After a dive, the robot uses a powerful water jet to accelerate free of the water and return to flight, allowing it to return water samples and data for analysis."

Some of the most potentially groudbreaking research in the new issue is in very early stages, said Lentink, who spent more than a year assembling and editing the new issue. For instance, biologists and engineers at Aachen University in Germany are looking into how owls are able to fly in near silence when stalking prey.

The paper goes into great detail measuring owl feather characteristics like "leading-edge serrations" and "trailing-edge fringes" that alter airflow and allow for stealthy flight. This detailed information from the world of biology can provide a mathematical framework for future engineers trying to build quieter aerial robots.

"Drones make lots of noise," Lentink said. "But owls are very silent. So engineers would like to make drones very silent. Especially for things like delivery drones. Nobody wants to have hundreds of buzzing delivery drones flying around the city, like bees."

Speaking of which, other papers in the journal look to flying insects for inspiration. One study out of Harvard looks at how small flying robots could mimic bumblebees to effectively navigate turbulence.

Other research projects included in the new issue study how insects jump off surfaces for take off, or how some birds can stay aloft for weeks or months at a time.

"We ended up publishing 18 papers, so that's a lot of work," Lentink said. "But it's great because you get to see a lot of good research and gather all the exciting stuff together."

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