CARDEROCK -- When an airliner crashes, investigators scour the wreckage for that scorched wire or mangled engine fragment that can explain what went wrong.
Accidents at sea are different.
Fifteen-hundred people have been lost since the 1970s on ships that have vanished at sea without a trace. "Why are ships sinking like this?" asked Philip A. Dent, a naval architect at the British Embassy.
Dent is honorary chairman of a panel assembled by the Society of Naval Architects and Marine Engineers (SNAME) to develop investigative strategies for solving such mysteries -- a new science they call marine forensics.
Their hope is that the infant science will one day be reliable enough for use in modern marine accidents. For now, however, they're testing their tools and techniques on historic wrecks to avoid entanglement in litigation.
During the past year, the panel has focused on the White Star liner Titanic, which sank after striking an iceberg in April 1912, killing 1,507 people. It plunged out of reach, 2 1/2 miles down in the North Atlantic.
In August, the forensic panel took its submersibles and digital cameras to the North Atlantic to assemble detailed photos of the ship's remains.
Last month, members gathered at the Naval Surface Warfare Center here in Montgomery County to study the Titanic's plunge to the bottom by sinking a 5-foot model in a huge Cold War-era naval research tank.
The group hopes to apply its knowledge to the wreckage of the liner Lusitania, sunk in 1915 by a German torpedo with 1,200 lives lost; and the Britannic, sunk in 1916 by a mine.
The Titanic project is sponsored by RMS Titanic Inc., which holds salvage and exploration rights to the ship, and financed by the Discovery Channel, which is filming a television documentary on the panel's research. Gregory Andorfer, executive director of the Maryland Science Center, is the project's executive producer.
The Surface Warfare Center's maneuvering basin is a dark, eerie indoor lake beside the Potomac River near Washington. There, stealth submarines and America's Cup racers can be developed in miniature, and in secrecy.
In a dank concrete basement there recently, Dent stooped before a thick underwater window, peering into the basin's murky green water. He was waiting for a yellow model of the Titanic's bow section to take its first 35-foot plunge. Beside him was William H. Garzke Jr., a naval architect at Gibbs & Cox Inc. of Arlington, Va., and founder of SNAME's forensic panel.
Analyzing shipwrecks requires "reverse engineering," Garzke said. That means getting a look at the wreck and distinguishing the damage caused by its plunge and collision with the bottom from what triggered the sinking.
Vast ocean depths once made that impossible. By 1985, advances in remote imaging and robotic submersibles led to the discovery of the Titanic's North Atlantic resting place.
Investigators learned that the liner had broken in two. "Prior to 1985, it was thought that the ship sank intact," said Garzke.
Evidently, the weight of the water that flooded the ship after it struck the iceberg stressed the ship's steel beyond the breaking point. It snapped at the surface, and bow and stern sections sank separately to the bottom.
Armed with the Titanic's lessons, British government investigators went to the Pacific in 1997 to solve the 17-year-old mystery of the Derbyshire, a 90,000-ton British bulk carrier that disappeared in a 1980 typhoon off Okinawa. No trace of the ship or its 44 crew members had been found.
Hatch covers ripped
Robot cameras revealed that mountainous waves had ripped open the Derbyshire's hatch covers, allowing water to rush in. The water's weight broke up the ship. The findings led to demands for stronger deck hatches.
"If we hadn't done the Titanic, we wouldn't have understood the Derbyshire," Dent said.
But what happened to the Titanic after it snapped in two and sank beneath the waves?
During a four-week Discovery-financed expedition in August, the engineering panel used robotic submersibles to gather digital photos of the wreck site. Assembled into photomosaics, the pictures revealed stark differences between Titanic's bow and stern halves.
The bow end seemed nearly intact, but the photomosaic "shows the utter carnage in the stern," said Robin Williams, a British naval architect and co-chairman of the forensic panel. The deck has been peeled back, and "everything has moved from its expected position," he said.
From the picture and the ship's plans, the panel concluded the damage was caused by 90,000 cubic feet of air that had been trapped in the ship's 18 nearly airtight refrigeration rooms.
As the stern sank, water pressure increased and imploded the rooms. Huge bubbles of the compressed air stormed out, alternately squeezed by rising water pressure and released by progressive damage. It's called a pressure wave, and "it's what sinks submarines," Williams said.
Tearing through the ship, the air caused enormous damage, all of it during the first 100 feet of the stern's 2 1/2-mile descent. Williams compared it to "a few pounds of Semtex," a powerful plastic explosive, in each refrigeration room.
When the shattered stern section hit bottom, it collapsed like a rotted melon.
On the Titanic's bow section, photos revealed deck structures that a speedy rush to the bottom should have torn away. But could Titanic's bow section have drifted gently to the bottom like a leaf?
"Nothing very much is known about how a ship behaves under the surface," Williams said.
The answers could help investigators learn to distinguish between damage caused by explosions or huge storm waves and that done during a ship's rush to the seafloor.
At Carderock, the marine panel repeatedly sank a 5-foot scale model of the Titanic's bow section, recording its descent with cameras and a three-dimensional echo-location system.
The tests suggest the real Titanic fell at almost 20 mph, faster than some had guessed but slow enough to explain the survival of such things as deck railings.
The model also fell in a stable pattern. "We had been concerned that it would have tumbled or rolled or done some weird things," Williams said.
Instead, almost like a glider, it fell first with its nose tilted down. Then the bow slowed, and the model drifted down and backward in a "tail slide," with its nose up. "It did that three or four times in the depth of water we had," Williams said. "Very stable. Very predictable. It was quite exciting."
Scaled up, the scientists calculated, a 2 1/2-mile plunge like that would have carried the Titanic's bow section 1,800 to 2,000 feet away from the stern half, which fell nearly straight down. And that's just how they were found in 1985.
'Science comes first'
"This is the first brick in the wall in understanding what happens to a ship when it is tracking from the surface to the seabed," Williams said.
But was it real science or was the investigation staged for Discovery's cameras?
"The science comes first," said producer David Elisco of Stardust Visuals, the independent film company hired by Discovery to make the documentary. "The visuals inherent in this production are quite spectacular but it's the science that's critical."
Without Discovery, Williams said, the Titanic project would not have happened. But "if we were doing it as a proper scientific exercise, we would have spent a lot more money to do more tests and a more serious investigation."
Though not rigorous enough for more than a "technical note" in a scientific journal, he said, "it is good enough for other people to take up and pursue."
"It has already said things to me which will add to my knowledge," he said. "If we go to contemporary wrecks in the future and analyze them, this is information we need."
The Discovery Channel's documentary on the Titanic research is scheduled to air April 25.
Pub Date: 1/10/99