A small fleet of drone submarines sits in drydock at a Virginia Tech engineering building.
They’re autonomous underwater vehicles, AUVs for short, and they come in multiple sizes. Among them are three bright yellow ones called 690 AUV. They’re as tall as an NBA forward but as big around as a stove pipe.
Their target: microplastics.
Virginia Tech scientists from the Center for Marine Autonomy and Robotics launched a 690 last summer at Claytor Lake, testing the AUV for eventual deployment in Chesapeake Bay waters. There, a filter on its bow might gather microplastics, which researchers hope to use to explore the plastics’ effects on people and the environment.
Dan Stilwell, an electrical and computer engineering professor, and Charles Watson, a research associate, both are from Autonomy and Robotics. They’re working with a larger Virginia Tech College of Science team called the Seale Coastal Zone Observatory.
“There’s probably nothing exciting with microplastics and Claytor Lake,” said Stilwell, the center’s co-director. “But it’s a fantastic place to turn things on and to test equipment, and then we can take things out of the Chesapeake Bay, where the hypothesis is that we’ll find more interesting things.”
From water bottle to salmon to human body
Plastic is part of most consumer items, and plastic waste is endemic. Most marine debris is plastic, according to the National Oceanic and Atmospheric Administration. Degraded to smaller than a quarter-inch, it becomes microplastic, NOAA says.
Those tiny pieces break down from a variety of sources, said John Morris, associate dean for research at Virginia Tech’s College of Science. Aging car tires slough off pieces everywhere they roll. Someone throws a plastic bottle on the ground, where the sun, wind and other weather elements break down the plastic and move the micros around.
“So they start out macroscopic, then move to microscopic, then nanoscopic, and all of that affects their rates of transport throughout the environment,” Morris said. “The plastics move into the sediment. They move into the air that we breathe.”
And into water sources. But what happens from there? What effect are they having on the people who make them, use them, waste them, and then, unwittingly, consume them? These are among many pollution-related questions that scientists with the Coastal Zone Observatory hope to answer.
“Eventually, we’d like to understand how that water bottle makes its way into the salmon you bought last night, and then how we might be able to affect the manufacturer, or the processing … of the plastic initially,” Morris said.
“We might be able to slow down that process or eliminate that process, or how we process the waste, how we can better recycle that material such that it does not affect our food supply.”
First, researchers have to harvest some microplastics. From there, the team might learn where they reside in the Chesapeake Bay, what makes them flush out into the bay and how long they stay there, Stilwell said.
A spokesman for Annapolis, Maryland-based Choose Clean Water Coalition said that his office was not aware of anyone conducting a similar experiment in the bay that Maryland shares with Virginia and other states.
“While not always visible to the naked eye, microplastics present a direct threat to clean water throughout the Chesapeake Bay region,” said Choose Clean Water Coalitions Director Kristin Reilly, in a prepared statement. “With clean water at the heart of every healthy community, we applaud efforts to study and remove this hazard from our waterways.”
Studying underwater robots in Appalachia
Watson, the research assistant, designs and builds the 690 AUVs, with a bit of outside help from vendors. Desktop computer design, 3D printing and final assembly happen in a lab at Tech’s Torgersen Hall.
“They are the generic workhorse of our lab,” Watson said.
The team conducted two lake-area tests in the summer. One showed that the sub worked underwater, Watson said. An electronics hiccup inside the AUV halted a late August excursion, and the team was unable to successfully operate the microplastics sampler that would have gathered material from the water, Stilwell said.
The team will continue to learn from its prototype system during the next year, Stilwell said in a recent meeting at the Center for Marine Autonomy and Robotics.
Watson and Stilwell have been updating and enhancing the 690s since 2018. These AUVs perform “significantly better” than anything available on the commercial market, Stillwell said. And the cost is low enough that they can build teams of the vessels to work together and autonomously underwater.
Sonar and other sensing devices can get the teams around in murky waters, and communication devices can help the subs search and gather information, Stilwell said.
While the microplastics project is fairly new, Stilwell and Virginia Tech got their first grant for drone subs about 20 years ago, Stilwell said. He came to the school in 2001, after getting his Ph.D. from Johns Hopkins University. He has a master’s degree from Virginia Tech.
For the last 15 years, they’ve been working with funding from sources including the U.S. Navy, he said.
Virginia Tech has exactly the right expertise to do what seems illogical — underwater robotics in Appalachia, Stilwell said. The school has a graduate program in naval architecture and experts in marine propulsion. The land-grant institution historically has supported the shipyards in Norfolk, he said.
“We’ve got all this expertise on how to put things into the ocean,” he said. “I came along 20 years ago and got some grants … and we started building things, and we were horrible at it.”
In the ensuing years, the team improved its building, and it now studies systems in which multiple autonomous subs communicate with each other and collaborate on decision-making. About half of its research portfolio is contracts with the U.S. Navy, to build new classes of underwater robots, Stilwell said.
The 690 AUV weighs 91 pounds and can descend 500 meters, moving at a maximum of 4 knots for up to 24 hours, according to university data. It communicates via satellite, radio frequency, Wi-Fi and acoustic modem, which translates digital data into sound signals that travel underwater.
Stilwell envisions a possible commercial need, particularly for companies that want to map the oceans. Undersea maps are less complete than those of interstellar objects. The marine robotics center is working toward a submersible that can reach depths sufficient to map the ocean floor, he said.
Microplastics, though, rank high among the more immediate goals. Once the marine robotics center’s submersible is able to snag microplastic samples from the bay, it will be up to other Virginia Tech scientists to analyze them. Like a map of the ocean, that is a great unknown.
“I think it’s really now well-established that microplastics make their way into human bodies,” said Morris, the associate dean. “What’s not well established, though, is the effect on health. We don’t know yet. That’s another open question and an interesting aspect of this project.”
Looking ahead to the bay
After the botched test run from late summer, the marine robotics team redesigned and tested power and data subsystems in the AUV and was planning this week to test their fix with the microplastics sampler.
After that, they will head back to Claytor Lake, where Hurricane Helene’s mess lingers.
“Unlike anything I have ever seen at the lake, and it has definitely affected our fieldwork,” Stilwell said. “There is a large ongoing effort to clean it up.”
Watson expected that the team would have two vehicles running in the lake before year’s end, with the bay on the schedule for 2025.
