Launched in 1996, ABE-Vne Autonomous Benthic Explorer-is a strange looking triple-hull submersible developed and operated by the Woods Hole Oceanographic Institution (WHOI). Since its maiden voyage, the autonomous unmanned vehicle (AUV) that can operate independently to depths as great as 20,000 feet has successfully completed more than 200 unattended dives in the Atlantic and Pacific Oceans.
It has been nearly a half-century since the first deep-diving submersibles entered service. These were the primitive manned vehicles such as the Navy's bathyscaph Trieste. By the end of the 1970s, more than 250 different designs had been built for a wide variety of underwater tasks. Today, there are perhaps four dozen employed, mostly for oceanographie research and tourism.
It was 1964 when Woods Hole began operating a manned submersible, the Navy-owned Alvin. Arguably the bestknown scientific submersible, the Alvin's 4,200 dives have added much to our knowledge of the deep ocean to depths as great as 14,500 feet. Now, at the age of 40, the Alvin will be replaced by an updated manned vehicle, financed by the National Science Foundation and able to dive to 21,500 feet.
In the mid-1970s, a second family of submersibles became operational. First developed by the Navy in the 1960s, these are the remotely operated unmanned vehicles (ROV), which have many advantages over manned submersibles. They do not have to be certified to carry humans, logistic support at sea is greatly reduced, and operating costs are considerably less. These factors are especially important when doing work that does not require human presence at depth. And, while manned vehicles' mission times run 14 to 16 hours, this is not a factor for unmanned submersibles.
Controlled from a surface ship by way of an umbilical cable and on-board television cameras, vehicle pilots maneuver them from a control console thousands of feet above the submersible. Today, thousands of ROVs-ranging from large work vehicles costing millions of dollars to simple swimming TV cameras for less than a few tens of thousands-have been successfully deployed. They are the most common undersea vehicles used by governments, academe, and industry.
The world's most complex vehicle system was Japan's Kaiko, put into service in the mid-1990s. Costing more than $50 million, it was able to dive into the deepest parts-almost seven miles down-of the world ocean. Regrettably, the system vehicle was lost a few years ago when its umbilical broke. The Japanese plan to replace it.
Autonomous unmanned vehicles (AUV) are the third and newest family of submersible work platforms. The Navy first experimented with them in the 1960s; however, the first operational vehicles were not in service until the early 1990s, with the ABE entering service at WHOI in 1996.
Because AUVs are untethered, they must be programmed prior to each mission. There are no umbilicals for electric power, control, and data transmission to the mother ship. Everything is contained on board.
It was difficult for early AUV developers to dump expensive prototypes into the ocean and hope for the best, but operational experience has shown that they are reliable and do return to base. As operators gained confidence, more extensive missions were added to the repertoire.
WHOI, for example, has recently learned how to operate more than one submersible-ROV and AUV-concurrently to increase productivity. This is especially helpful in doing research studies at seafloor hydrothermal vent complexes. These are the areas where new seafloor materials are being created and could be a resource for metallic minerals.
It remained for WHOI's talented and experienced underwater engineering group and a few private companies to develop some of the first practical AUVs. Now, progress is being rapidly made, and several companies are selling and operating commercial AUVs worldwide.
For nearly a half century, Woods Hole's underwater engineering group has worked on design, construction of submersibles, and the work systems fitted to them. Over the years, as ROVs and AUVs were added to WHOI's capabilities for deep ocean research, and with the government establishing the National Deep Submergence Facility there, they have become an international center for underwater work systems. The three families of submersibles represent a set of complementary tools with the user being able to pick and choose for the best research results.
Now at the age of 11, the ABE is facing partial retirement. An improved design, Sentry, is undergoing tests at Cape Cod and should be operational in late 2007 or 2008.
Dr. Walsh, a marine consultant, is a retired naval officer and oceanographer. During his naval career he served at sea in submarines and ashore In oceanrelated research-and-development assignments.