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First jellyfish aircraft simple yet efficient

AFP-JIJI

Inspired by nature and by the aviation pioneers of the early 20th century, scientists in the United States have built the world’s first jellyfish aircraft.

The tiny, ultralight lab machine, weighing just 2.1 grams, is the first man-made flying object to hover and move with a motion like that of the jellyfish in water, the inventors believe.

“We were interested first of all in making a robotic insect that would be an alternative to the helicopter,” said Leif Ristroph, who works alongside Stephen Childress at New York University’s Applied Math Lab.

“Our interest ended up being a little bit weird — it was the jellyfish.”

The jellyfish has long been admired by engineers for a simple yet efficient motion, sculpted by millions of years of evolution, that requires just a simple muscle and no brain power, just a primitive nervous system.

It has a bell-like translucent skirt that first billows out and then closes tightly, squirting water out from the small opening to provide itself with movement.

In this case, the aircraft uses four petal-shaped wings, each 8 cm long, that when folded together form a downward-facing “cone.”

A tiny motor, attached to a crankshaft, causes the wings to push outward and then downward 20 times a second, forcing out air through the bottom of the cone.

The result is an “ornithopter,” or flying machine that hovers with great stability without the need for constant, energy-draining correction.

“If it’s knocked over, it stabilizes by itself,” Ristroph said in a telephone interview.

The craft can change direction by making one of the four wings work harder than the others.

The materials to make the machine are all over-the-counter components — light carbon-fiber ribs to hold the motor and provide the frames of the wings, which are covered by transparent Mylar film — bought at ordinary modeling stores.

Ristroph said he and Childress had been intrigued by film footage of aviation pioneers who had tried to mimic insects to build ornithopters, but lacked the knowledge or materials at the time.

“We were inspired in part by videos from the 1900s, in the early experimental days of flying. They were very creative in those days. They had lots of very good ideas, but also some bad ones,” he said.

In its present state, the jellyfish aircraft is a “proof-of-concept” device aimed at testing that the idea works. New York University has already filed a patent, said Ristroph.

The next step will be to add a battery — the prototype is powered by a fine electrical wire — and remote control.

The invention is reported in the Journal of the Royal Society Interface, published by the Royal Society, Britain’s de facto academy of sciences.

A lot of work is needed on maneuverability and energy efficiency, but ultimately, perhaps not too many years down the road, flapping unmanned aircraft could be a common sight, Ristroph hopes.

“There’s definitely some military use for things like this, such as in surveillance, but I hope that it has a civilian outlet too,” said Ristroph.

“I can imagine a cluster of 100 of these being thrown out and fanning out across in a city to monitor air pollution.”

The featherweight craft still needs an official name.

“We usually call it our flying jellyfish,” said Ristroph. “But the name AeroJelly would be cool!”