More clues of the H.L. Hunley mystery are being revealed during conservation of the American Civil War submarine. Researchers in a North Charleston, South Carolina, laboratory on Wednesday June 7, 2017 unveiled the crew compartment -- which had been sealed by more than 130 years of ocean exposure and encrusted sediment.
New details of Civil War sub's past uncovered
01:36 - Source: CNN
CNN  — 

A broken pipe may help explain why a famous Civil War submarine sank off of Charleston, South Carolina, more than 150 years ago.

The H.L. Hunley became the first submarine to successfully attack an enemy ship in combat when it sank the wooden ship USS Housatonic on February 17, 1864. The Confederate vessel disappeared with all its eight crew members.

More than 130 years later the Hunley was discovered on the ocean floor. The sub was raised and taken to a laboratory in North Charleston in 2000.

Since then, conservators and archaeologists have been working to preserve the vessel and study its contents in hopes of finally figuring out what happened.

They found the broken intake pipe at the front of the Hunley while cleaning away the thick, rock-hard coating of sand, shells, sea life and other materials – known as concretion – that built up on it over time. The pipe carried water to a ballast tank that helped the sub submerge and surface.

There was a 1-inch gap where the pipe was supposed to mount to the side wall.

A pipe running from the Hunley's ballast tank to the outside hull broke around the time the submarine sank in 1864.

“It left a crescent-shaped opening in the hull which would be a great place to flood and sink your submarine,” said Clemson University archaeologist Michael Scafuri, who’s been working with the Hunley team since 2000.

The evidence is interesting, but not conclusive.

Scafuri said researchers can tell that the pipe broke around the time the Hunley sunk because of the amount of concretion that covered the break, but they can’t yet tell whether the pipe broke during the attack or came apart after it sank.

“Obviously, with something like this, it’s important (to know) if it happened the night of the attack and thereby might have caused the sinking, or if it happened two weeks later from some other reason after the submarine has already sunk,” he said.

Researchers at the University of Michigan found it would have only taken 50-75 gallons of water to drag the Hunley to the ocean floor, according to a news release from the Friends of the Hunley organization. It would have only taken minutes for that much water to flow in through the hole.

The hole was small enough that a crew member could have stuffed something in it to slow the flow of water, or pumped the water, but that doesn’t seem to have happened.

“They weren’t trying to escape or taking other actions to save the sub,” Scafuri said. “There’s no sign of panic on board.”

On the night of the attack, Scarfuri said that the captain’s single candle would have been the only light in the cramped, 25-foot long crew area. If the candle went out, or was lost, they would have been working in the dark. There also would have been a fair amount of noise from the ocean around them.

“I don’t know if he could see it, I don’t know if he could hear it,” he said.

The crew members’ skeletal remains were found at their stations and their bodies had no obvious physical injuries.

Conservators work to clean away the layer of sand, shells and sea life that collected on the Hunley during the almost 136 years the submarine spent on the sea floor.

A number of theories have tried to explain the mystery of the Hunley. Maybe the crew went too deep, misjudged their oxygen supply and got trapped by the current. Maybe a nearby ship collided with the sub, throwing it off balance into chaotic waters. Maybe a bullet made it through a porthole, killing the captain and leaving the crew adrift at sea.

The Hunley used a 135-pound bomb that was attached to a 16-foot long pole to sink the Housatonic Some scientists think the shock waves from the explosion could have killed or incapacitated the crew, but a US Navy study determined that they would have survived the blast.

“It’s kind of a mystery,” Scarfuri said.

He compared the archaeology to a crime scene investigation, but said it’s now a very cold case.

“All of the evidence that was fresh at the time of the sinking is now blurred,” Scarfuri said.

Scarfuri said each new piece of evidence gives researchers a better understanding of this important naval battle. He hopes they will one day get to the truth, but said he can’t make any promises.

“It’s not up to us,” he added. “It’s up to the evidence.”