Condom robot is fastest underwater vehicle ever

John Hopton for redOrbit.com – Your Universe Online

It may look like a swimming condom, but this new octopus-inspired robot achieves propulsion and acceleration never before seen in man-made underwater vehicles. Mimicking the way in which octopuses propel themselves away from predators, the robot provides a great opportunity to improve underwater technology.

Cephalopods, such as the octopus, can escape danger (or possibly just impress their buddies) by filling their bodies with water and ejecting it to dart away at high speeds. This inspired scientists from the University of Southampton, Massachusetts Institute of Technology (MIT), and the Singapore-MIT Alliance for Research and Technology to build a robot with a 3D printed skeleton that can replicate the action.

The 30cm long self-propelling robot is inflated with water and then rapidly deflates by shooting the water out through its base to power itself along. It starts from a non-streamlined shape, but as the rocket contracts, it can achieve more than 2.6 times the thrust of a rigid rocket performing the same action.

The University of Southampton website explains that: “It works like blowing up a balloon and then releasing it to fly around the room. However, the 3D printed polycarbonate skeleton inside keeps the balloon tight and the final shape streamlined, while fins on the back keep it going straight.”

Dr Gabriel Weymouth, Lecturer for the Southampton Marine and Maritime Institute at the University of Southampton and lead author of the study, says:

“Man-made underwater vehicles are designed to be as streamlined as possible, but with the exception of torpedoes, which use massive amounts of propellant, none of these vehicles achieve speeds of even a single body length per second… despite significant mechanical complexity.” By contrast, the new octopus robot is capable of accelerating up to ten body lengths in less than a second.

Weymouth adds that: “Rigid bodies always lose energy to the surrounding water, but the rapidly shrinking form of the robot actually uses the water to help propel its ultra-fast escape, resulting in 53 per cent energy efficiency, which is better than the upper estimates for fast-starting fish.”

The researchers explain that in recent laboratory tests, the robot accelerated a one kilogram payload to 6mph in less than a second. “This is comparable to a mini-cooper carrying an additional 350kg of weight (bringing the total weight of the car to 1,000kg) accelerating from a standstill to 60mph in one second – underwater.”

They predict that scaling up the robot would improve its acceleration. Furthermore, the octo-bot could have applications in the development of artificial underwater vehicles that can match the speed, manoeuvrability, and efficiency of underwater animals

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