Repackaging the computer parts will be the latest in a long list of modifications and redesigns that began with Shadow I in 1998. Shadow has become an annual senior design project in UA’s Mechanical Engineering Department, and is entirely designed and built by undergraduates, with the exception of some computer programming done by a graduate student a couple of years ago.

The project received NSF funding in 2000 and has made great progress since then. Vincent anticipates that it will be ready to track octopuses next year.

Before that happens, this year’s student design team will build a wireless communications system to free Shadow from the mother boat. Currently the sub and a computer on the mother boat are linked by a 100-foot-long coaxial cable. “We want to get rid of that tether from the boat and have it come to the surface at a buoy,” Vincent said. “Then there will be a wireless link between the buoy and the boat.”

The team also will modify Shadow’s buoyancy system. Water flows into a ballast ring that circles the center of the sub. The amount of water that it takes on determines the sub’s buoyancy, allowing it to submerge to any depth. Compressed air tanks on the sides of the sub blow this water out to bring Shadow to the surface.

“Right now the buoyancy system is under manual control, but we hope to have it under automatic control next time,” Vincent said. “We’ll just type in the depth we want on the computer and Shadow will automatically submerge to that depth.”

Sub Will be Operational Next Year
Although the submarine will begin shadowing octopuses next year, Vincent has plenty of ideas to keep senior design teams busy for a long time.

“The way it is now, we’ll still be on the surface watching images from Shadow’s video camera and waiting for something to happen,” Vincent said. “We’ll manually control the video camera. But farther in the future we hope to make it totally autonomous.”

In autonomous mode, the submarine would operate on its own, following an octopus using its hydrophone sensors. It would decide when to turn on its video camera, transmitting video to a remote receiver.

“This would require the submarine to know something about the topography of the ocean bottom in its area so it wouldn’t run into a big rock or other obstacle while following the octopus,” Vincent said.

The advantage of fully autonomous tracking is that octopuses spend a lot of time in their dens vegging out, which is pretty boring for researchers. Instead of waiting for hours on the surface, biologists could set up the robot to wait quietly for an octopus to emerge from its den. Then the submarine could become their eyes and ears underwater, recording the octopus’ movements for later retrieval.

With that goal in mind, Vincent figures there’s plenty of engineering work to keep senior design teams occupied for several years to come.