New silent underwater propulsion system inspired by octopods

Fraunhofer’s prototype silent underwater propulsion system was inspired by octopods. It uses four 3D-printed elastomer balls to pump water and provide the required thrust.
Date:3 July 2013 Tags:, , ,

Time and time again, biomimicry (that is, the study and imitation of nature’s systems) has provided the answer to many of our technological dilemmas. This makes perfect sense. After all, our planet’s had over 4,5 billion years of trial and error experimentation to discover what works best. This time around, scientists from Germany’s Fraunhofer Institute for Manufacturing Engineering and Automation have drawn on inspiration from octopods to develop a silent underwater propulsion system that could work for recreational watercraft and submarines.

As far as silent, fast manoeuvring goes, it’s damn hard to beat an octopus or squid. The Institute’s Andreas Fisher explains: “Octopods rely on high-pressure water jets to flee their enemies. To do this, they take water into their mantles, which are then closed by contracting their sphincter muscles. The water is then squirted back out at a high pressure via a funnel. By changing the position of the funnel, they can precisely control their direction of travel. The system is simple, but highly effective. We have integrated this propulsion principle into our underwater actuators: four small elastomer balls with mechanical inner workings that create propulsion by pumping water.

”Here’s how their prototype propulsion system, which has just successfully passed initial laboratory tests, works: Water is first sucked into each actuator (or elastomer ball) through an opening fitted with a recirculation valve to prevent reflux. A hydraulic piston then contracts the integrated cable structure like a muscle. In this way, water is pushed out of all four 20 x 6 cm balls to generate thrust. And, just as octopods steer themselves by positioning their funnels, the system uses a motor to selectively point the balls in the desired direction.

Best of all, this system can be produced in a single step with a 3D printer. Production can reportedly be easily scaled up to produce large, two metre-diameter spheres. It’s also proven itself to be capable of withstanding extreme levels of pressure without showing any signs of breakage.

For more information visit www.fraunhofer.de