Catching a Sea Perch

by Eric Bender

The underwater remotely operated vehicles (ROVs) run by offshore industry or the Navy or scientists are usually big brawny fellows, designed to grab a valve on an oil platform at the bottom of the Gulf of Mexico or scan remote areas of the Pacific sea floor or pluck cargo from the Titanic. But you can build a model ROV that fits inside a milk crate and zooms through water in basically the same ways.

That's exactly the role of MIT's Sea Perch project, which builds these small educational wet wanderers, and exactly what teams of middle and high schoolers accomplished Wednesday at the MIT Museum.

At the start, about half the kids said they were enthusiasts for science and engineering, and the other half cheerfully said they had been forced to come by their parents. Ably led by Kathryn Shroyer, mechanical engineer and Sea Grant educator, they all plunged together into designing and building their own Sea Perches.

To keep the exercise within three hours, Shroyer had painstakingly pre-assembled the most complicated components. Each team received a set of four motors tucked into film canisters, waterproofed, topped with propellers, and hooked up via a long thin power cable to a battery and a control box. That let the groups focus on creating their own frames, and connecting the motors and floats.

Most teams came up with a similar design theme for their pocket submersibles: small, fast and

maneuverable. Pieces of PVC and flotation were soon flying through the air. The kids rethought and rebuilt their frames, and bandied about names like Hot Dog Mark 1 and Magical English Kangaroo.

Each team then marched its contender down to first floor of the museum, which was awash in a Dive into Ocean Science exhibition for Earth Day. Here, the team members would work their way through the crowd, gently lower their contraption into a large aquarium tank and smile

and puzzle as it bumped and scuttled around the tank. After a few minutes, each team would pluck the ROV from the tank and head back to the lab to fiddle with flotation and weights and make other tweaks.

Back down into the tank again, the kids would look again to spot what now worked and what didn't really. And like the operators of fullscale ROVs, they got splashed sometimes.

 Photos courtesy Kathryn Shroyer, MIT Sea Grant