The robot now being tested in Virginia is the first major step in learning exactly how the ray does that. Work is already underway on second and third generation mechanical rays, and that will give the researchers greater flexibility. They should be able to determine how the rays react to a change in current, for example, and how it gets that forward thrust by flapping its wings.
But going from a creature made of cartilage and muscles to a device made of rods and cables and actuators is a challenge. It would be easy to add a forward thrust mechanism to the robot, but that would defeat the purpose of the research. In the end, the robot has to perform exactly like a live ray, somehow moving forward as it flaps its wings up and down in an amazingly efficient manner.
The process is called bio-mimicry: creating machines that copy nature.
"It's an amazing species to watch swimming," said Bart-Smith, who has also swum with wild rays. "It just looks effortless. It's a fast, efficient swimmer that can operate in many ocean environments from open ocean to close to shore, from near the surface to on the bottom."
The researchers didn't know if their first attempt to build a mechanical ray would be successful.
"We were excited when we took it to the pool to test it out," she said. "It was our first attempt to see what was going on. Have we got something that could actually swim? We were amazed at how life-like it looked."
She said she took the video home and showed it to her husband and her daughters.
"They said, 'That looks like a real ray,'" she recalled.
The next step will be to find a pool that's more than 14 feet deep -- the maximum depth of the university's swimming pool -- and free the robot from its tether. They will also need to develop a communication system so they can control the device remotely, even at great distances.
Then it will really look like a ray. And that could pose a new problem. Build a mechanical ray, paint it realistically, let it loose in the ocean, and it may look so realistic that sharks will try to prey on it .
"If it looks like a ray and swims like a ray there's a potential for a predator thinking it would be a tasty morsel," she said.