UFO shape keeps "flying snake" airborne

There are five species of snakes in Southeast Asia that are able to fly -- or at least glide through the air, up to 100 feet at a time. The snakes do not have wings or fins of any sort, so how they stay airborne has long puzzled researchers.

Now, a team of biomechanists at Virginia Tech University is offering new clues into the aerodynamic mystery of the “flying snake,” thanks in part to a 3D-printed replica of its body.

“When gliding, the flying snake Chrysopelea paradisi morphs its circular cross-section into a triangular shape by splaying its ribs and flattening its body in the dorsoventral axis,” the study authors wrote. The dorsoventral axis refers to a line stretching from the back to the belly. Their research is published in The Journal of Experimental Biology.   

“It looks like someone's version of a UFO,” lead researcher Jake Socha tells the journal's Kathryn Knight.

To determine how the splayed shape helps the snakes glide through the air, the researchers 3D printed a rod in the same UFO shape. Next, they placed the rod in a water-filled tank, studying how the water flowed over it and measuring drag and lift at various angles. 

Most of the angles produced enough lift to keep the snake afloat. But “when the team tilted the model at 35 degrees, there was a massive spike in the lift generated by water flowing at higher speeds. More surprisingly, when the model was held level with the flow, instead of generating upward lift, the fluid pushed the rod down,” Knight explained.

Adding microscopic beads to the water, Socha and his team could see a spinning vortex directly beneath the UFO shape when the rod was not tilted. The finding shows that the snake holds its body strategically, in order to maintain flight. 

“Maybe the snake does hold part of its body flat at some point, using it as a mechanism for control,” Socha added.

The next step is to determine how closely the experiments in the water tank mimic real life.

“If you make a rough estimate of the lift to drag ratio for the real animal, it appears to do better than what we got from this study. So even though this shape produced more lift than we were expecting, it doesn't get us the glide performance that snakes can attain, giving us a hint that there is something in what the animal is doing aerodynamically that is not captured by the cross-sectional shape alone,” he said.

The mildly venomous snake is also known as the Paradise tree snake.