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The Oldest Crewed Deep Sea Submarine Just Got a Big Makeover

In early March, a gleaming white submarine called Alvin surfaced off the Atlantic coast of North Carolina after spending the afternoon thousands of feet below the surface. The submarine’s pilot and two marine scientists had just returned from collecting samples around a methane seep, an oasis for carbon-munching microbes and the larger species of bottom dwellers that feed on them. It was the final dive of a month-long expedition that had taken the crew from the Gulf of Mexico up the East Coast, with stops along the way to explore a massive deep sea coral reef that had recently been discovered off the coast of South Carolina.

For Bruce Strickrott, Alvin’s chief pilot and the leader of the expedition, these sorts of missions to the bottom of the world are a regular part of life. Since he first started working on Alvin as an engineer nearly 25 years ago, Strickrott has logged more than 2,000 hours in the deep ocean, where he learned to expertly navigate the seabed’s alien landscape and probe for samples with the submarine’s spindly robotic arms. Alvin makes dozens of trips to the seabed every year, but the mission to the methane seep this spring marked a milestone in Strickrott’s career as an explorer: It was the last time that the sub would have meaningful limits on how deep it could dive.

Since the end of that expedition, Alvin has been ashore getting a major upgrade at the Woods Hole Oceanographic Institution in Massachusetts, which operates the submersible on behalf of the US Navy. By the time Alvin’s makeover is wrapped up in late 2021, the storied submarine will rank among the most capable human-rated deep sea submersibles in the world. When Alvin hits the water again next autumn for a trip into abyssal trenches near Puerto Rico, Strickrott will be among the first to pilot what is effectively a brand new vessel. During that trip, he and a team of oceanographers and US Navy observers will push the submarine to 6,500 meters—far deeper than it has ever gone before.

Earlier this month, Strickrott and a small team from Woods Hole presented the progress on Alvin’s upgrades at the annual meeting of the American Geophysical Union, which was held remotely as a precaution against the pandemic. Arguably the most important improvement is Alvin’s new titanium ballast spheres and a pressurized crew compartment that will enable the submarine to carry up to three occupants just over four miles below the surface. This upgrade alone will extend Alvin’s maximum depth by more than a mile and put approximately 99 percent of the seafloor within its reach. “We’ll have access to almost the full ocean,” says Strickrott. “It really opens up a lot of opportunities.”

Alvin is a cross between a robotic laboratory and excavator. It has a portly white hull with a metallic crew sphere protruding from the front of its belly, and a bright red fin up top. Two jointed sampling arms—the upgrade will give it a third—extend from the front of the crew sphere and are used to shovel up to 500 pounds of sediment and other material into a sample hold on the craft. As part of the upgrade, Alvin will get some more powerful thrusters mounted to its back end, a suite of sophisticated imaging systems, and an acoustic transmission system so that its occupants can wirelessly send images and metadata from the bottom of the ocean to a ship on the surface.

To upgrade Alvin, engineers had to tear the sub down to its metal skeleton at the National Deep Submergence Facility, a federally funded research space hosted at Woods Hole. This is a regular occurrence for Alvin, which gets stripped to its nuts and bolts every five years even when there’s not a major upgrade planned. The vessel is made almost entirely from custom components designed to withstand the uniquely hostile environment in the deep ocean, and the regular teardowns ensure that everything is in good shape.

Adam Soule, the Chief Scientist for Deep Submergence at Woods Hole, says it’s this meticulous attention to detail that’s helped Alvin avoid having even a single serious accident after more than 5,000 dives. “We’re not developing prototypes,” Soule says. “All the technology we develop has to be bulletproof, so there’s a lot of engineering that’s done before anything makes it onto the sub.” Still, there have been some close calls. Only a few years after Alvin was commissioned, a mechanical failure on its carrier ship caused it to fall into the ocean and it began to sink with three crew members inside. The crew narrowly escaped, but it took a year to recover Alvin from the bottom of the ocean.

Alvin has been in service for nearly six decades, but due to regular teardowns and rebuilds, the submarine piloted by Strickrott has little more than a name in common with its progenitor. For the philosophically inclined, Alvin calls to mind the Ship of Theseus, an ancient thought experiment in which the boards of a ship are torn out and replaced one by one until nothing of the original remains. Over the years, Alvin has been upgraded several times so it can carry researchers ever deeper into the ocean, spend more time at depth, and carry more samples plucked from the seabed. But until its most recent remodel, Alvin’s depth rating only gave it access to around two thirds of the seabed. There was a lot more ocean to explore.

Alvin’s current upgrade is the second and final phase of an overhaul that began nearly a decade ago. Funded by a $40 million grant from the National Science Foundation, the first phase laid the foundation for subsequent improvements that would extend the sub’s maximum depth from 4,500 to 6,500 meters, which is deep enough to cover 99 percent of the world’s seabed. By the time that phase was finished in 2013, many of Alvin’s components were already rated to the full 6,500 meter depth, including the sub’s personnel carrier, a cramped titanium alloy sphere. But Alvin has had to wait to venture into those depths until after the final improvements were completed during the second and final phase of the upgrade this year. “Back in 2013, about 70 percent of the sub was replaced,” says Strickrott. “We knew that we were going to operate for a period before we finished the last bits and pieces, which is what we’re doing now.”

Once engineers at Woods Hole have put the finishing touches on Alvin in the spring, it will undergo a rigorous testing process to prepare for its first dive to 6,500 meters. The first tests of the full vehicle will be uncrewed and will demonstrate that Alvin can run its life support systems for 24 hours without creating any harmful gases that would endanger its passengers. Next, a three-person crew will spend 12 hours inside Alvin on the shore to test its life support system again. If everything goes well, the Navy will give the Woods Hole team the go-ahead to begin tests in the water.

Next September, Alvin will be transported by ship to Puerto Rico, where it will begin its first wet tests. Over the course of a week, Alvin and its crew will dive progressively deeper in roughly 500 meter increments. By the end of the week, Alvin will have reached its maximum depth and touched the seafloor in the abyssal trenches off the Puerto Rican coast. If the tests go well, the Navy will officially authorize Alvin for regular crewed expeditions to that depth, and the submarine will spend most of the next five years in the water around the US conducting scientific research until its dragged back to Massachusetts for its regular tuneup.

The expedition in Puerto Rico will be the first time that Alvin has ventured into the hadal zone, the deepest and least understood region of the ocean. The hadal zone is dark, cold, and the ambient pressure is up to 1,000 times higher than on the air pressure at the surface. Life is scarce here. A few species of fish can exist up to around 8,000 meters below the surface, but the deepest regions of the hadal zone are occupied entirely by invertebrates and microscopic organisms.

Altogether, the world’s hadal trenches occupy an area larger than Australia, but scientists have only just begun to discover what lurks in their depths. The hadal zone extends from 6,000 to 11,000 meters below the surface, and only a dozen people in history have made it to the very bottom. The deepest spot in the ocean, known as the Marianas Trench, received its first visitors in 1960 and wasn’t visited again until the last decade, when filmmaker James Cameron and the adventurer Victor Vescovo made independent dives to the end of the abyss. Although Alvin will only be skimming the surface of the hadal zone, it will be one of only a handful of human-rated crafts that are capable of going that deep.

When it comes to learning about the deep ocean, Alvin’s upgrade couldn’t come soon enough. Marine scientists are in a race to study the bottom of the ocean before it’s irreparably damaged by human activity. The deep ocean absorbs a significant amount of Earth’s carbon dioxide and heat, but the process is poorly understood. It’s still unclear how rising emissions and temperatures will affect the Earth’s feedback loops with the deep ocean, so gathering data from the bottom of the ocean today will be critical for understanding how it will change in the future.

“Our knowledge of this abyssal zone is minimal,” Soule said during a presentation at the annual AGU meeting earlier this month. “We can almost count on discoveries of novel species and new processes each time we venture to these newly accessible depths.”

But the seabed harbors more than just knowledge. It is a treasure trove of valuable metals like cobalt and manganese that go into our electronics; there is likely more of these metals on the seabed than on all of the Earth’s surface. Deep sea mining companies are already doing exploratory work to prepare to harvest these valuable substances at scale. But current approaches to deep sea mining are incredibly destructive, and the detrimental effects of this activity on deep sea ecosystems are not fully understood. The UN-led International Seabed Authority is still hashing out regulatory frameworks that will serve as the rule book for the deep sea gold rush, which buys scientists some valuable time to study the ocean floor before it’s dredged up. Now that it can reach most of the seabed, Alvin will be able to play an even greater role in that scientific mission.

“You can’t possibly manage a resource or protect its environment if you don’t know what’s there,” says Strickrott. “In the big picture I think it’s pretty important that we get to the deep ocean to understand the biodiversity. If we don’t go there, we won’t know what to do, or have a stake in those decisions with respect to mineral resources.”

Despite Alvin’s promise, it’s reasonable to wonder why Woods Hole, the National Science Foundation, the US Navy, and their many collaborators want to go to all the time and effort of sprucing up a 60-year-old submarine. These days, updating a vehicle usually means looking for ways to take humans out of the loop—we have autonomous cars, self-landing planes, and smart ships. Ocean explorers have also leaned into autonomous and remotely operated submarines that can explore the ocean floor for a fraction of the cost of Alvin and with none of the risk to human life. Why not let robots do the dirty work of collecting data and leave the humans to pursue pure science?

Uncrewed submarines have been diving into the hadal zone for decades, but Brennan Phillips, an ocean engineer at the University of Rhode Island who specializes in remotely operated and autonomous deep sea robotics, says it’s hard to beat a human when it comes to exploring the seabed. For starters, humans can see more. Our eyes are amazing sensors and modern underwater cameras—or any cameras, for that matter—can’t come close to matching their resolution, especially in the low light of the deep ocean. “I’ve been in a manned submersible in the deep ocean and seen things with my own eyes that you can’t repeat yet with a camera,” says Phillips. “They’re still a long way short of what the human eye can do.”

Humans are also important for discovery. Scientists cruising the seabed in Alvin are better equipped to recognize something they’ve never seen before and take a sample of it to study once they’re back on the surface. While this can also be done with a remotely operated sub that is connected to a human controller on the surface via a long tether, it’s more challenging for remote operators to identify promising sample sites. The miles-long tether can also create problems for the robot and limit where it can travel. Untethered autonomous robots have a harder time still, since they don’t have access to GPS for guidance and can struggle to recognize promising sample sites on their own.

Phillips thinks that relying on robots might also compromise what scientists can see in the deep ocean. They tend to be much louder than subs built for humans, and they use much brighter lights because of the limited resolution of their cameras. Phillips says this likely frightens bottom dwellers, which makes it harder for researchers to make new discoveries. He suggests that part of the reason the hadal zone appears so desolate is because by the time these lumbering robots get to the bottom, they’ve scared away all the inhabitants.

“There’s only been a handful of dives to these depths, so we really need to go more often,” says Phillips. “The hadal zone is considered to be basically featureless, but some of that might be coming down to our methodology. If you just make it a bit more stealthy, you can probably find things down there that we’ve been missing this whole time.”

After 25 years of roaming the seafloor in Alvin, Strickrott isn’t afraid of a robot taking his job anytime soon. He acknowledges the important scientific reasons for keeping humans in the loop, but for Strickrott, human-driven deep sea exploration taps into something more profound. While many people might not relish the idea of being trapped in a cramped metal bubble in the pitch blackness of the deep ocean, Strickrott says that’s his “happy place.” He can still recall the thrill he had working on Alvin as a young ocean engineer, and he relishes accompanying budding marine scientists on their first trip to the bottom of the ocean.

“There is, without a doubt, this really aspirational part of oceanography that involves humans exploring these parts of our planet that have never been seen before,” says Strickrott. “In order to keep the science of oceanography vibrant, we need to ensure that there are lots of people who are excited by the science.”

Strickrott feels that establishing that connection with the ocean—by immersing yourself in it, by going as deep as you can in this alien environment, by seeing how life can thrive in an environment that would kill land dwellers instantly—is critical to its future and our own. We may need cutting edge technology to survive a trip into its depths, but the ocean and life on land are deeply intertwined. It's that connection that Strickrott channels each time he climbs into Alvin. “Once you’re underwater, you get into this place in your mind that’s sort of Zen,” he says. “You're part of the system.”

Update 12.21.2020 5:43 PM: This story has been updated to correct the number of people who have traveled to the bottom of the hadal zone.

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