Robots of the Briny Deep
As a marine archaeologist based in Louisiana, Robert Church often studies grainy, black-and-white images of the ocean bottom for signs of a shipwreck or prehistoric site. Church does such survey work for oil and telecom companies that want to avoid obstacles when building underwater pipelines or laying cable. But one day earlier this summer, Church found himself staring at an image that seemed to highlight a large, cigar-shaped object. He telephoned his buddy Martin Morgan, a maritime World War II buff and said, "I think we found it."
What Church and colleague Daniel Warren discovered was a World War II German U-boat that sank nearly 60 years ago. Lying in silt under 5,000 feet of water, it rests about 45 miles south of the mouth of the Mississippi River. On July 30, 1942, U-166 sank the American passenger freighter Robert E. Lee with about 400 souls on board, many of them construction workers returning with their families to Louisiana and Florida from Trinidad. Twenty-five of those aboard perished when the ship went down.
It was only after the sub's wreckage came to light in that survey photo that Church and other experts could conclude that a Navy ship sank the U-166 just minutes after the sub launched its torpedo attack on the Robert E. Lee. Up until then, it had been assumed that a U.S. Coast Guard seaplane sent the sub to the bottom days after U-166's assault on the freighter.
For history buffs and maritime enthusiasts, U-166's discovery rewrote the story about the only German sub known to have been sunk in the Gulf of Mexico during the war. The U-166 was among 15 German subs that prowled the Gulf and intercepted unarmed U.S. tankers and freighters carrying crude oil from Louisiana and Texas.
But the oil industry also took note of the sub's discovery. That's because Church and Warren at C&C Technologies, a surveying-and-mapping outfit based in Lafayette, La., used a new kind of technology -- an autonomous underwater vehicle (AUV) -- to unlock the secret of U-166's fate. If the AUV concept catches on, it could help oil companies save a great deal of time and money when conducting ocean-bottom surveys of the sort that precede the construction of oil and natural gas pipelines. Moreover, it could scan the sea floor at much greater depths than previously thought possible.
Church and Warren were studying the Gulf of Mexico for a proposed joint pipeline project by British oil giant BP and Houston-based Shell Oil Co., part of the Royal Dutch/Shell Group. Using the AUV technology, the survey was completed in one-fifth the usual time (three days vs. 15 days before), and at roughly one-third to one-half the usual cost associated with traditional techniques, says Andy Hill, BP's geohazards team leader. "The beauty of the AUV is that it allows us to be able to do the types of surveys that we've never been able to do in deeper water before, except at exorbitantly high cost," says Hill.
The survey is part of a multiyear effort to build the proposed 100-mile-long Okeanos pipeline -- the Gulf's first gas pipeline in water depths exceeding 6,000 feet. BP has an agreement with C&C Tech to use its AUV system. The Okeanos pipeline eventually will connect with other pipelines and serve the eastern U.S., transporting at least 1 billion cubic feet of natural gas per day from large fields in deep water. Construction of the pipeline is scheduled to begin in 2002.
Most underwater surveys use the traditional towing method -- not AUVs. Equipment that helps create rough images of the ocean bottom is loaded on a boat. Out at sea, the equipment, tethered with a cable, is dropped into the water. Once the equipment sinks low enough, the boat is moves back and forth, "mowing the lawn," while dragging the equipment behind.
This is the tried-and-true method, but there are drawbacks. The deeper the water, the less sharp the acoustic signals -- and the fuzzier the images. The mowing-the-lawn technique is also time-consuming and can be brought to a virtual standstill by rough seas. And then there are the cables. They are easy to tangle, so surveys must be made in straight lines rather than in more efficient arcs.
By contrast, the AUV operates with remote controls -- in other words, no cables required. The vehicle is launched from a boat to survey along preprogrammed lines. Since the vessel is unmanned -- operators on the surface control it -- it can survey for roughly two days, instead of mere hours, as it draws operating power from a fuel cell battery. Plus, more advanced underwater imaging equipment on board the AUV allows for clearer snapshots of the sea bottom, and at much deeper levels than the traditional tow method. Enthuses marine archeologist Church of C&C Technologies, "The detail you can see is incredible."
Church says that the U-boat would not have gone unnoticed by a traditional tow-method survey. The U-166 was found 130 miles east of its original, assumed location. In fact, historians for years believed the German sub's wreckage was that of a cargo freighter, based on previous survey work, which turned out to be inaccurate. Meanwhile, the German sub, along with the likely remains of its 52 German crewmembers, will remain untouched. The wreckage is considered a war grave site and cannot be disturbed, according to an international treaty. And the Okeanos pipeline was rerouted.
So if the AUV is so great, why are BP and Shell Oil among the first -- if not the first -- oil companies to use a commercial AUV, equipped with a full arsenal of advanced underwater imaging equipment? A key reason is cost. C&C Tech so far has invested more than $6 million in one AUV and associated research and development.
Another company, Kongsberg Simrad of Norway, manufactured the orange AUV, which is roughly 3 feet in diameter and as long as a full-sized pickup. AUVs built for commercial sale cost a minimum of several million dollars for a lower-end version with little sophisticated survey equipment. And only a handful of companies now manufacture commercial AUVs.
OFFSETTING HIGH COSTS.
Because of their high cost, most AUVs are being used by universities for research and by the U.S. military for defense purposes. In addition to cost, there's also the fear of losing an expensive AUV. Jeff Fortenberry, a spokesman for C&C Technologies, acknowledges the risk but adds that the company also has invested in numerous safety devices that would bring the AUV to the water's surface if a problem should arise.
AUVs seem likely to become far more versatile as the technology advances. Hybrid versions are being developed that would not only to survey the ocean floor, but also visit remote subfloor wells to conduct inspections and turn valves on and off. "It could become an underwater working mechanic for you," says Timothy Runyan, director of the Maritime Studies Program at East Carolina University in Greenville, N.C.
So while there are skeptics, others anticipate seeing more commercial AUVs in use as costs come down. Besides, "It's saving the oil companies too much money" not to be put into more frequent use, adds Church. And that's an important factor as more oil and gas continues to come from deeper waters. History buffs, meanwhile, will be watching AUV developments closely. "I can't wait to find out what else is out there," says Morgan of the National D-Day Museum in New Orleans, La. Neither can a lot of big oil and telecom companies.
By Heesun Wee in New York
Edited by Thane Peterson