Propellers? They're overrated.

Powerless Flight

To engineer an efficiently flying drone, what better inspiration than birds?

In keeping with that spirit, researchers in the Netherlands say that by mimicking the techniques of nature's flying creatures, they've designed a winged drone that can soar near effortlessly compared to its peers, almost never requiring powered flight to stay airborne.

According to their yet-to-be-peer-reviewed study, their birdlike drone, which weighed roughly 1.5 pounds, only needed to use its propellers 0.25 percent of the time it spent hovering in place in a wind tunnel, compared to the 38 percent it needed for normal flight. Put another way, that's just over 150 times less the use of powered throttle — a pretty hefty boost in efficiency.

The researchers call this specific form of flight "orographic soaring." Essentially, what birds do to soar: riding on an updraft of wind, and to maintain a steady position, descending at just the right rate.

You can see an earlier version of the experiment below, which impressively didn't use propellers at all.

Bird Brained

Imitating the complex mechanics of biology is rarely easy. Birds like the condor have flying down to an art, and one has been observed soaring for over five hours without flapping its wings once. In comparison, high quality consumer drones can fly for maybe a half hour at a time.

Storing enough power for constant output from propellers — or "flight endurance" — is a drone designer's worst enemy. Beyond that, the biggest edge that birds have over machines is an intuitive understanding of the wind, able to harness mercurial gusts as a captain does the sails of their schooner.

This intuitive edge was the point of focus for the researchers, who designed an autonomous algorithm to adjust the drone it controls to changing winds. The algorithm takes in its airborne environment through a suite of sensors, including one for airspeed, a GPS system, and a camera.

"When the wind field changes, it adapts to the environment and changes its position autonomously," study lead author Sunyou Hwang, an aerospace engineer at Delft University of Technology in the Netherlands, told New Scientist. "It always tries to find a new position if its current position doesn't work — it's very flexible."

Though the flight times achieved here weren't longer than 30 minutes, it's still an impressive duration for how simple the drone was, and for how little propulsion and intervention was needed.

The drone will need to cut its teeth, however, beyond a wind tunnel. Jonathan Aitken, a professor of automatic control and systems at the University of Sheffield, told New Scientist that the results are promising for use in small drones — but the algorithm will need to respond faster to keep up with real world winds.

More on drones: This New Delivery Drone Could Be Our Adorable, Awesome Future

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