In August 2004, the Woods Hole Oceanographic Institution (WHOI) and the National Science Foundation jointly announced a $21.6-million program that will replace the venerable manned submersible Alvin. The yet unnamed vehicle will be able to dive to 21,320 feet compared to the Alvin's 14,764 feet, a depth increase of 31%.
The new submersible will join four others in this depth class: Russia's two Mirs (20,000 feet), France's Nautile (20,000 feet), and Japan's Shinkai 6500 (21,500 feet). Also in 2007 the People's Republic of China will put a 23,000-foot-capable submersible into service. Under construction now, she will be the world's deepest-diving manned submersible.
What is important about the 20,000-foot depth? A submersible capable of reaching this depth can access 97-98% of the oceans' seafloor. Thus, only 2-3% of the seafloor is between 20,000 and 36,000 feet at the oceans' deepest point. From engineering and cost points of view, designing for this depth makes sense.
In the early 1960s, the Woods Hole Oceanographic Institution and the Office of Naval Research (ONR) worked together to procure a manned submersible for the institution. The original idea was to lease the large, all-aluminum submersible Aluminaut that was to be built by Reynolds Aluminum Company.
ONR sent advance planning and procurement money to WHOI to help support the Aluminaut program's startup. The balance of the lease funds had to be allocated in 1962. At this point, however, Reynolds and the Navy could not agree on the terms for a long-term lease. ONR had a serious problem. Part of the Navy's money had been spent and the balance had to be allocated soon or it would be lost.
In 1961-62, the Bathyscaph Trieste group at Navy Electronics Laboratory in San Diego concluded they needed a shallower depth submersible for operations to 6,000 feet. Trieste could operate at any depth in the ocean, but she was fragile. The electronics laboratory team, together with a contract engineer from General Mills, produced a submersible design concept, "Sea Pup," which was proposed to ONR.
The head of ONR's Undersea Warfare Branch received the Sea Pup concept papers with excitement. Here was the solution to his dilemma. A Sea Pup-type submersible would be procured by ONR and sent to Woods Hole to be used as a trainer to show the Navy's determination to proceed without the Aluminaut. Then perhaps Reynolds would become more reasonable with the lease terms.
The rest is history. An expert WHOI team used the Sea Pup conceptual design as a starting point to develop a much improved and more capable submersible that was put into service in 1964. She was named Alvin in honor of the distinguished Woods Hole scientist Allyn Vine who had a major role in the Aluminaut and Alvin program developments.
As built, the Alvin was a 6,000-foot-capable submersible, but in 1972-73 she was converted to a 12,000-foot vehicle by the addition of a titanium pressure hull and the hardening of other external components. This depth capability let the vehicle access 34.5% of the seafloor of the World Ocean. Subsequent upgrades increased depth to 14,764 feet, or 58% seafloor coverage.
After 44 years and an estimated 4,400 dives, the most famous manned submersible in the world will cease diving in early 2008. It long had been recognized that an Alvin replacement was needed, but it was not until recently the National Science Foundation was able to fund this project.
To reduce technical and financial risks, the procurement program for the Alvin's replacement will be in two stages. The first will be for the design and construction of the pressure hull (the most difficult technical task). Titanium is favored for the hull, but other options are being considered. The two Russian Mir vehicles, built in Finland, use maraging (martensitic aging) steel, a carbonless iron-nickel alloy.
The immediate concern is to find a U.S. company that can successfully build this large titanium structure. Titanium currently is preferred over maraging steel. Initial queries by the WHOI project team indicate that at least three U.S. companies may be qualified. There also is at least one company in Russia that has this capability; it is building the titanium pressure hull for the new Chinese manned vehicle.
Once the hull structure project is progressing successfully, the final design and construction of the rest of the submersible will be initiated. If the development program stays on schedule, the new WHOI submersible should be in service in 2008.
At that time the Alvin will be fully retired. Hopefully, her final resting place will be a museum.