The following article appears in the journal JOM, 53 (3) (2001), pp. 12-14

Feature: Archaeotechnology

Raising the Hunley: Archaeology Meets Technology

TABLE OF CONTENTS
THE HISTORY RAISING THE HUNLEY STABILIZING THE RELIC THE NEXT MOVE
Figure a. An animated illustration of how the H.L.Hunley was retrieved from the floor of Charleston Harbor.
Figure b. Time-lapse photography shows the submarine being lifted from the water and placed on a barge, to be transported to a laboratory.

No one knows how it felt to be a Civil War soldier crammed into the submersible iron cylinder called the H.L. Hunley. But Robert Neyland can guess that physical comfort was not a priority. On its final voyage, eight men, seated elbow to elbow, strained to crank a manual propeller, moving the submarine through the currents of South Carolina’s Charleston Harbor. A ninth man stood hunchbacked, steering the vessel. The ceiling was no higher than 1.4 m above the floor, the walls no more than 1.1 m apart (Figure 1). “The walls were probably sweating from condensation,” said Neyland, the U.S. Navy’s chief underwater archaeologist. “If anyone got sea sick, there was no escape.” Neyland hopes to take the guesswork out of the story of the Hunley, its construction, and why it sank in 1864. He is project manager of a diverse team of scientists, archaeologists, and conservators who are using groundbreaking technology to investigate the submarine, which was rescued from the floor of Charleston Harbor in August 2000. The experts are poised to study everything from the rivets of the sub to the DNA of its crew. “It’s a great scientific mystery to solve, applying all the modern techniques of science,” Neyland said.

Author's Notes: See Figure a for an animated illustration of how the H.L. Hunley was retrieved from the floor of Charleston Harbor. Figure b uses time-lapse photography to show the submarine being lifted from the water and placed on a barge, to be transported to a laboratory. To best experience these presentations, you should employ the latest version of RealPlayer.

THE HISTORY

Encrusted with iron oxide and carbonates in a lumpy, greenish coating known as concretion, the Hunley after 136 years under water looks little like an engineering marvel. Yet it is surprisingly hydrodynamic, Neyland said, with both ends coming to “almost a razor edge” to cut efficiently through the water. Rivets were sanded, almost flush with the submarine’s exterior, to reduce friction. “We were expecting something stocky and crude-looking,” Neyland said. “What we got is something very graceful and sleek-looking” (Figure 2).

The vessel was equipped with two ballast tanks that could be filled with water to submerge the sub, and pumped to raise it again. “Some of the best engineering of the south had been applied to the sub,” Neyland said. The vessel was constructed in 1863 for the Confederate army based on plans of Horace Lawson Hunley, James R. McClintock, and Baxter Watson. With U.S. Navy ships blockading Charleston Harbor, the Hunley was planned as a stealth weapon that would approach the navy ships undetected and ram them with a spar torpedo attached to a long pole on its bow (For images of the sub, visit the U.S. Navy website). After planting explosives in the enemy ship, the Hunley was to back off and detonate them with a rope. That mission was ultimately achieved, earning the Hunley its place in history as the first submarine to sink a ship in wartime, but not before the sub sank twice, killing 14 crewmembers including Horace Lawson Hunley.

The night she sank, on February 17, 1864, the Hunley was on a mission to torpedo the USS Housatonic, a Federal war ship. For safety’s sake, the sub was to stay on the water’s surface. It did, and successfully rammed its spar into the ship’s wooden side, retreated, and detonated 41 kg of explosives. The Housatonic sank, but the Hunley never returned (For details on the Hunley's military accomplishments, from a U.S. Navy perspective, see the Navy website). Not for another 50 years would a submarine sink another warship, according to Archaeology, a publication of the Archaeology Institute of America.

RAISING THE HUNLEY

Figure 1. A cutaway drawing of the Confederate submarine H. L. Hunley. (Image provided by U.S. Navy.)

Figure 2. Early artist’s rendering of the Hunley’s exterior. (Image provided by U.S. Navy.)

For 131 years the submarine remained undetected, entombed in sand and sediment 6.4 km off the coast of South Carolina’s Sullivan Island. Then, in 1995, author and adventurer Clive Cussler, with a team from his National Underwater and Marine Agency, was rewarded for persistence after a 15-year search. That search was conducted in partnership with the South Carolina Institute of Anthropology and Archaeology. Dragging a magnetometer through the water, the explorers located the sub preserved under one meter of silt, in water 8.5 m deep. The vessel, covered in concretions from 6.4 mm to 19 mm thick, was found intact, lying on its starboard side at a 45-degree angle.

Its cold, dark environment had blocked out oxygen, warding off deterioration not only of the metal, but also of organic materials, Neyland said. But that preservation posed a problem: “Once we expose (the sub) to oxygen, the deterioration rate is going to accelerate,” he said.

Raising the Hunley without damaging it would require years of expensive preparation. The U.S. Navy became involved, assigning Neyland, a seasoned archaeologist, to oversee the project. The state of South Carolina established the Hunley Commission to acquire, recover, and preserve the sub and its contents. Warren Lasch, a South Carolina businessman, became chairman of Friends of the Hunley, a fund-raising arm of the Hunley Commission.

Those groups and others investigated the sub extensively under water and concluded that, thanks to its sturdy construction, the protective layer of concretion, and available technology, the Hunley and its contents could be raised and kept intact.

To bring the sub to the surface, a cradle of 32 nylon belts was developed in which the vessel would snugly nest. The belts were designed to hang from a bridgelike truss, providing precisely the same support as existed in the Hunley’s underwater home. Each belt had a bag attached, which was injected with a quick-setting, self-sealing foam that was used previously on space shuttle missions, Neyland said, but adapted for underwater use. As the bag filled, it conformed to the contours of the submarine.

“In effect, we captured the sub with the same support the seabed was providing for it,” he said.

The belts were also equipped with load cells to gather data such as load and strain, determining how tightly each should be pulled to accurately replicate underwater conditions. In addition, sensors on the belts would continually monitor oxygen levels.

On August 8, 2000, the system was attached to a crane, and before a cheering crowd, truss, belts, and sub were moved from the water to the former Charleston Naval Base, where a special tank had been constructed to contain the relic in a new laboratory (Figure 3).

STABILIZING THE RELIC

The Warren Lasch Conservation Center had been built at the old naval base specifically for the Hunley. It was equipped with a 16.8 m × 5.5 m × 2.75 m metal tank filled with chilly water. The water temperature is kept at around 10°C to reduce the rate of corrosion, said Paul Mardikian, senior conservator for the project. Mardikian’s job is to protect the integrity of the archaeological find. “I’m responsible for everything that could go wrong on the project, from the time it was found under water to the time it is going to be in the museum,” he said. With this project, plenty can go wrong. Mardikian, whose resume includes conservation work on wreckage of the Titanic luxury liner and the Confederate war ship C.S.S. Alabama, said the Hunley is the most challenging job he has faced, and will set a new standard for maritime archeology.

“From the scientific standpoint…raising, excavating, and conserving the Hunley is one of the most interesting endeavors of the 21st century,” Mardikian said. “I think this project would not have been possible 10 or 20 years ago.”

Figure 3. The submarine was carefully secured with nylon straps and foam cushioning, and raised from the floor of Charleston Harbor in August 2000. (Photo provided by Fujifilm.)

Figure 4. A close-up view of the sub’s concretion-covered hatch. A sensor is attached to the hatch’s lower right side, monitoring the conditions of the conservation lab tank. (Photo provided by Fujifilm.)

A challenge will be to excavate the sub without destroying any artifacts. Because the oxygen-free environment is likely to have preserved some human remains, along with a variety of materials such as weapons, tools, navigational instruments, paper, clothing, and personal items, that mission is especially delicate. For example, a key to preserving an artifact of any size is neutralizing corrosion. Normally, when an iron object is under water, that goal can be accomplished by adding chemicals to maintain a high pH level in the water. Because such chemicals may be harmful to the human remains inside the sub, Mardikian had to devise an alternative system to fight corrosion. Maintaining a cold water temperature was an easy first step, he said. “If you reduce the temperature, you reduce most of the reactions…bacterial, corrosion rates, enzymatic—everything’s going to slow down.”

Mardikian further slowed the corrosion rate with cathodic protection, bringing electrons to the submarine with an impressed current in a system designed by Corrosion Control Inc., a Georgia firm specializing in cathodic protection and corrosion control. An iron object losing electrons is similar to a human losing blood, Mardikian said. By adding electrons, the bleeding is prevented and the corrosion slows down. “If you turn off the power the corrosion literally jumps,” Mardikian said.

One of the simplest ways to protect the iron is to protect the concretion coating, which blocks out oxygen. Fortunately, the Hunley was raised so carefully that the outside layer was never cracked, Mardikian said (Figure 4). In this controlled environment—the water chemistry in the tank is monitored continuously for pH, temperature, chlorides, conductivity, oxygen, and corrosion potential measurements—the sub has been investigated without ever disturbing its walls or contents.

Using a new three-dimensional (3-D) laser-scanning technique supplied by another private company, Pacific Survey Supply, the sub’s exterior has been mapped digitally “down to millimeters,” Neyland said. “It’s brand new,” he said of the technology. “Most people I’d known had never seen this before.”

When the time comes to investigate the interior of the sub, the 3-D mapping will be used again. Neyland has made enough low-tech drawings of ships to appreciate the 3-D technique.

“I think this is going to have an impact on archaeology,” he said. “I’ve done these painstaking drawings of ships and shipwrecks. Even if you’re the best at it you still get a little human error. We would use techniques people have been using for a hundred years.”

Questions about the sub’s construction will be answered using computed radiography technology provided by Fujifilm. That technique, normally used to inspect for structural flaws in equipment such as jet engines and pipelines, will help determine the details of the Hunley’s exterior and its contents.

Before the radiography could begin to examine the sub’s contents, though, the Hunley team had to be assured that the use of x-rays or gamma rays would not harm the human DNA believed to be on the sub. Degraded human remains were subjected to high radiation in the lab, and forensic expert Dr. Jamie Dawn checked the DNA before and after. That testing was recently completed, and because the Hunley team was convinced no DNA damage would result, excavation began in early January.

At that time, access to the interior was gained through a hole in the sub’s stern ballast tank. Using that opening, information can be carefully gathered about the hull’s construction, Neyland said, such as how the hull plates are fastened together, and, in turn, how they can be removed. By removing several of the hull plates, the archaeologists can investigate the interior of the sub and retrieve its artifacts, according to Neyland (For the most recent update on the Hunley's excavation, visit the Friends of the Hunley site).

In case human remains are recovered, the conservation lab is equipped with a morgue where they can be stored, awaiting forensic analysis and eventual burial. Other organic materials, such as wood and textiles, will be freeze dried to prevent decomposition.

THE NEXT MOVE

With each step carefully calculated to preserve the Hunley and its contents, the excavation work is not expected to be complete for as many as ten years. The cost of the project has been estimated at nearly $20 million.

While the investigation continues, Mardikian and his crew will likely be using techniques such as electrolysis or gaseous reduction to remove iron chlorides that developed from the iron’s exposure to salt water. When the choride in sodium chloride binds with iron, the iron becomes unstable and the object is permanently unstable.

“We’ve got to track them down and remove them,” Mardikian said of the iron chlorides.

When all the work is done, the sub will be moved to a permanent home in the Charleston Museum, a tribute to the cutting-edge technology of 1863, uncovered and preserved with the cutting-edge technology of the 21st century.

Maureen Byko is managing editor of JOM.

For more information visit the Friends of the Hunley web site at www.Hunley.org. or send e-mail to info@hunley.org.