Our amazing planet.

US Deep-Sea Submarine Gets Makeover

Alvin submersible personnel sphere test.
Alvin's new titanium sphere, wired up for a pressure test in June 2012. (Image credit: Jeff McDonald, Woods Hole Oceanographic Institution.)

The crews rebuilding Alvin, the United States' deepest-diving manned vehicle, recently celebrated a significant milestone in the submersible's years-long upgrade with the unveiling of a newly tested titanium sphere that will one day ferry three people 21,325 feet (6,500 meters) deep into the ocean.

Before the upgrade, Alvin could travel to a maximum depth of 14,760 feet (4,500 meters), and the vessel's makeover will extend its reach into the ocean's unexplored depths.

"Right now it reaches about two-thirds of the ocean. At 6,500 meters [21,325 feet] it will reach 98 percent of the ocean," said Susan Humphris, leader of the upgrade project and a geologist at the Woods Hole Oceanographic Institution, Alvin's operator.

Testing, testing…

Engineers tested Alvin's new 11,000-pound (5,000-kilogram) personnel sphere on June 22 at a Northrop Grumman facility in Annapolis, Md., to ensure that the silvery capsule can withstand the crushing pressures of the deep sea.

Safety standards require that the sphere can survive a trip to 26,250 feet (8,000 meters), — a full 24 percent deeper than Alvin will ever dive — where the pressure is 12,000 pounds per square inch.

Designers beefed up the capsule's walls to withstand the additional pressure, increasing them from 2- to 3-inches thick (6 to 8 centimeters). They also added two more windows, for a total of five, to allow greater visibility for passengers, who will also get a bit more leg room.

"The diameter is 6 inches [15 cm] greater than the old one, so we hope it will be a little more comfortable," Humphris told OurAmazingPlanet.

Company in the deep

The announcement comes at a busy time for deep-sea exploration. In recent days, China's manned submersible, the Jiaolong, has claimed the mantle of deepest-diving state-owned vehicle on Earth.

On June 27, in the fifth of a series of progressively deeper dives into the Mariana Trench, the vessel carried a three-person crew 23,170 feet (7,062 meters) down into the ocean. The Jiaolong has now plunged more than 1,640 feet (500 meters) deeper than the previous deep-diving champion, Japan's Shinkai 6500 submersible, which can reach 21,325 feet (6,500 meters).

However, the Jialong is not the deepest-diving craft in existence. In late March, filmmaker James Cameron piloted a submersible to the Mariana Trench's Challenger Deep, 35,756 feet (10,890 meters), or nearly 7 miles (11 km), beneath the surface of the sea. Cameron's craft, the Deepsea Challenger, is one he helped design, and is privately owned. [Images: Cameron's Dive to Earth's Deepest Spot]

Humphris said the Chinese venture is certainly interesting. "They will be able to go a little bit deeper, so they will be able to go to parts of the seafloor that we can't," she said. "Since the seafloor is so poorly explored, we don't know what they'll find."

Alvin's upgrade is happening in two phases, and the submersible won't be ready to dive to 21,325 feet (6,500 meters) for several years, Humphris said. She said that even though robots, monitored by video from ships, can explore the ocean depths, it's important to send humans, too.

"It's sort of like, why do you go to the Grand Canyon if you can go buy a video of it?" Humphris said. "Putting an eye and a brain at the bottom of the ocean gives you a very different perspective than looking at a TV monitor."

Reach Andrea Mustain at amustain@techmedianetwork.com, or follow her on Twitter @AndreaMustainFollow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook & Google+

Andrea Mustain was a staff writer for Live Science from 2010 to 2012. She holds a B.S. degree from Northwestern University and an M.S. degree in broadcast journalism from Columbia University.