WHOI’s Submersible Alvin Gets Upgrades

The Woods Hole Oceanographic Institutions submersible Alvin began undergoing a series of pressure tests at a facility in Annapolis, Maryland this week. The tests are being conducted to see how it reacts to pressures simulating depths from 6,500 to 8,000 meters or 4-5 miles. To build in a safety factor, one test dive will put the sphere under pressure of 12,000 pounds per square inch, simulating a depth of about 8,000 meters, or 5 miles. If all goes according to plan, the new sphere will be transported to WHOI, arriving sometime during the first week of July. There, engineers will reassemble the newest incarnation of Alvin. It will have five viewports, compared with the three that previous Alvins had. The two hemispheres of titanium were forged in Wisconsin to create the new personnel sphere. Built in 1964 as one of the world’s first deep-ocean submersibles, Alvin has made more than 4,400 dives. It can reach nearly 63 percent of the global ocean floor. 

The sub's most famous exploits include locating a lost hydrogen bomb in the Mediterranean Sea in 1966, exploring the first known hydrothermal vent sites in the 1970s, and surveying the wreck of RMS Titanic in 1986. Alvin carries two scientists and a pilot as deep as 4,500 meters (about three miles) and each dive lasts six to ten hours. Using six reversible thrusters, Alvin can hover, maneuver in rugged topography, or rest on the sea floor. Diving and surfacing is done by simple gravity and buoyancy—water ballast and expendable steel weights sink the sub, and that extra weight is dropped when the researchers need to rise back up to the surface. The sub is equipped with still and video cameras, and scientists can also view the environment through three 30-centimeter (12-inch) viewports. Because there is no light in the deep, the submersible must carry quartz iodide and metal halide lights to illuminate the seafloor. Alvin has two robotic arms that can manipulate instruments, and its basket can carry up to 680 kilograms (1,500 pounds) of tools and seafloor samples.