How do you build the world’s fastest human-powered submarine? Engineering student teams from around the globe have been vying to come up with the answer – and clinch the title at the international competition held annually at the Carderock Naval Warfare Center in Maryland.

Last fall, a team of California Polytechnic Institute engineering students took up the challenge and sought inspiration from nature.

The quest began when aerospace engineering student Rylie Bryant, now a project engineer at Lockheed Martin, approached then-assistant professor Graham Doig in the Prototype Vehicles Lab and discussed her interest in biomimicry – creating something that imitates what animals do in the wild. Doig mentioned his interest in creating a submarine that captured the swimming prowess of a leopard seal, whose movements he’d observed when working in a zoo in Australia. “How is it producing so much thrust?’” he recalls wondering.

By the end of their discussion, Bryant decided she would pursue Doig’s idea for a human-powered submarine, with the goal of competing in the International Submarine Races held this past June.

The engineering challenge was huge. As Bryant explained in the CalPoly news article about the BioSub project, the team had to “minimize the volume as much as possible to minimize the drag.” A person had to be able to fit inside comfortably – necessitating foam cushioning. And since the sub wasn’t watertight, the sub also needed a way to pump air to the driver operating a makeshift pedaling device.

“We decided to do a race because it’s a good hard deadline to motivate us to get this done,” Bryant explained. “And it’s a good benchmark: There’s a set record to beat.” The record: 5.3 mph.

After researching the leopard seal, it soon became clear that there was no way to mimic the two fins it uses to create speed. So Bryant researched other fast swimmers whose body shape they could replicate. The short-fin mako shark, the cheetah of the seas, “had the most optimized geometry to be able to fit a person inside,” she said.

CalPoly aerospace engineering student Rylie Bryant takes video of teammate Annie Borland as she simulates the movement and position of a person inside a human-powered submarine.

While Bryant built a team to fund, design, and build the project, an obvious question loomed: Who would actually get in it?

Mechanical engineering graduate student Cullen Goss, a member of the triathlon team and avid cyclist, proved the perfect fit. “The chance to do something that crazy appealed to me,” he said.

The sub’s tail will be made of natural gum rubber, so it can oscillate back and forth like a mako shark’s. The body will be made of a carbon fiber shell, similar to material used for a lightweight aircraft. It will be a tight fit: The entire 13-foot-long submarine is being completely fitted to Goss’s body, with oxygen tanks that can fit under his prone body.

The BioSub may not have been among the winners of the 2019 International Human-Powered Submarine contest, but the students learned a lot about designing from nature.

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Tags: Aerospace Engineering, bioinspired design, Biomimicry, Cal Poly, Carderock Naval Warfare Center International Submarine Races, engineering education, human-powered submarine, Mechanical engineering, STEM education