Few sights in nature are majestic as a whale or dolphin jumping out of the water, but these graceful-looking manoeuvres are technically challenging to pull off. So a group of researchers set out to understand how jumping out of the water actually works by building a robot to do it.
The researchers, from Cornell University, studied simpler and more common animals like frogs and small crustaceans that perform a breaching manoeuvre. These smaller animals tend to breach either to catch prey or to escape from predators, and their small size and predictable behaviour make them ideal study subjects.
While examining these small animals, the researchers found that one of the key factors determining how high an animal can jump out of the water is called its “entrained water mass.” This is essentially the amount of water that the animal brings with it when it leaves the water. That extra mass is typically a significant percentage of the animal’s total weight, and the best jumpers find ways to minimize it.
These jumpers tend to be streamlined so they can cut through the water as smoothly as possible. The robot the researchers built to mimic the behaviour, however, was much less streamlined. The design the researchers chose was simple, with only a hinge and a rubber band to provide the jumping force. Still, their device was unable to reach the heights achieved by actual jumping animals.
“When we made and tested a robotic system similar to jumping animals, it didn’t jump as much as animals,” says study author Sunghwan Jung. “Why? Our robot isn’t as streamlined and carries a lot of water with it. Imagine getting out of a swimming pool with a wet coat—you might not be able to walk due to the water weight.”
For the next iteration of their robot, the researchers want to design it so it moves more easily in water and jumps higher. In the future, this research could help design more complex robots to breach into and out of the water. Combined with research on robots spying on real animals and a communications system to coordinate them, we could soon see fleets of small, breaching robots exploring the oceans.