Drones: like it or not, these intriguing little flying machines seem to be here to stay. Also known as unmanned aerial vehicles or UAVs, drones are controlled either by pilots located on the ground or inside another vehicle or autonomously, via onboard computers, they are used for an increasing variety of missions including firefighting and police work, surveillance of all kinds, and many other applications including delivering goods ordered online. So what does a drone have to do with the ocean, other than maritime patrol? Let’s take a look.
Drones - New Propulsion Methods Considered
Most drones are based on proven aircraft designs, while many others are designed to mimic flight activities found in nature – many tiny flying machines are modeled using the aerodynamics employed by birds and insects.
Moving through air is a lot like moving through water; both actions require thrust. Just like birds and insects, jellyfish generate thrust energy, but they do it in a different way entirely. Instead of flapping, they contract their umbrella-shaped bells, squeezing water out behind themselves and creating a ring-shaped vortex of water that pushes their bodies forward through the water column.
Larger jellyfish use an additional movement called rowing, which relies on the loose edges of the bell’s structure to create additional vortices which in turn help to increase the amount of thrust the animal is able to generate. The loose edges of the bell then push against the fluid in a way that’s similar to the action generated by a human rowing an oar through water. The newly designed drone relies on almost identical mechanics to move itself through the air.
Leif Ristroph, who is an applied mathematician at New York City’s New York University, was trying to think outside the box when he and a team of researchers came up with the new design. “Insects have built-in sensors and feedback that help them stay upright, and drones based on insect wings require the same support,” he said. “But motors, sensors, and batteries add weight, which is problematic for designers looking to create smaller drones.” Ristroph wanted to design a drone that had the same stability as those based on insects, but without the increased burden of the weight auxiliary parts add.
He came up with a drone which is propelled via four wings that point downward rather than off to the sides. These wings generate plenty of thrust, making liftoff a snap for the little UAV. The design is also quite stable, with the ability to right itself so that it remains upright while moving through the air – and this is accomplished without the need for additional sensors.
Interestingly, it wasn’t until after the drone had been built that Ristroph came to the realization that it moved much like a jellyfish – he works hard to create brand new designs no one has already thought of. “I’m personally interested in schemes that no one in nature or the engineering laboratory has thought of,” he told reporters. He is still working to improve his design so it can be used for practical purposes.