US scientists make aircraft that can fly like jellyfish swim


Thu, Jan 16, 2014 - Page 7

Inspired by nature and by the aviation pioneers of the early 20th century, scientists in the US yesterday said they had built the world’s first jellyfish aircraft.

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

“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 is admired by engineers for its simple yet efficient motion that only requires a simple muscle and no brain power, just a primitive nervous system.

The animal has a bell-like translucent skirt that first billows out and then closes tightly, squirting water out from the small opening to move. Similarly, the aircraft uses four petal-shaped 8cm-long wings, that when folded together form a downward-facing “cone.”

A tiny motor attached to a crankshaft pushes the wings 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 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 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.

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

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

“There’s definitely some military use for things like this, such as in surveillance, but I hope that it has a civilian outlet too,” Ristroph said. “I can imagine a cluster of a hundred of these being thrown out and fanning out across in a city to monitor air pollution.”