H.L. Hunley: New report addresses 6 theories on how Confederate submarine was lost

(U.S. Navy -- 1902 drawing by R.G. Skerrett)

A new report that calls the recovery of the H.L. Hunley in 2000 “part archaeology, part engineering and part spectacle” details six fascinating theories about the loss of the first submarine to sink an enemy vessel.

The archaeological report by the U.S. Navy, South Carolina Hunley Commission and Friends of the Hunley coincides with today’s 153^rd anniversary of the bold attack off Charleston Harbor that took down the USS Housatonic but also doomed the Hunley and its eight crew members.

Up front, we need to say no one knows for sure why the Confederate sub vanished on the moonlit, cold evening – as the report says, it could be a combination of factors. The Friends of the Hunley, in a Facebook post marking the Feb. 17, 1864, anniversary, said, “An international team of scientists (is) working to save the vessel and solve the mystery of her disappearance.”

The theories are at the end of the extensive report on the recovery of the Hunley, from planning stages to execution.

(USS Housatonic / Wikipedia -- public domain)

The hand-cranked Hunley left its base on Sullivan’s Island and placed a torpedo in the Housatonic, one of many blockade vessels on the edge of the harbor. Those on board desperately opened fire on the attackers. Five U.S. sailors were killed in the explosion and a chaotic scene ensued as other Federal ships came to the rescue. The Hunley vanished.

Robert S. Neyland of the Naval History and Heritage Command Underwater Archaeology Branch summarized the theories on what may have happened.

THEORY 1: Sub’s hull breached as a result of the explosion

Neyland writes that of the three “significant” breaches, only the missing viewport in the forward conning tower appears to have occurred close to the time of the attack -- but it is still possible this occurred after the sinking. He says the damage may have come from gunfire by the Housatonic crew or explosion debris. The forward hatch was found to be slightly ajar.

He writes: “The conning tower was above the surface of the water and (Lt. George) Dixon would have had time to block the hole to prevent water from flooding the submarine. 

(Courtesy of Friends of the Hunley)

"However, weather and sea state could also have been a contributing factor. With the wind building from the northwest at the time of the attack and immediately afterwards, and the tide setting to the northeast, seas would have been building with waves that could have thus been lapping over the conning towers. The damage to the forward conning tower alone should not have been sufficient to sink the submarine, provided it stayed above the surface. The hole could have been plugged with a garment or rag to prevent water …. If water did get in, it could have been removed with the pumps.”

Experts wrote in the hull analysis that that Hunley was streamlined and better balanced than its predecessors. “Still, there was a fragile balance between safety and disaster that required expert, careful handling.”

THEORY 2: Crew saw another Union vessel, decided to submerge

This scenario said the Hunley’s skipper saw the USS Canandaigua and took the boat to the seafloor to wait for enemy forces to disperse. The crew, ostensibly, died because of the lack of oxygen.

Neyland questions this theory: “If the damage to the forward conning tower occurred at the time of the submarine’s attack, Dixon would not have been able to take the boat down to the bottom to wait or to run the submarine fully submerged. Although the damage might not be a serious problem on the surface it was too large for Dixon to have sealed it securely enough to prevent flooding when underwater.”

(Friends of the Hunley)

“ … Hiding on the bottom until things quieted down on the surface or the tide changed might have been a short-term strategy but an attempt to hide on the bottom could only have been a momentary escape. He had conditioned his crew to submerge until they ran low of oxygen and he knew the limits of their endurance, which would be only an hour or two at most."

The report says the Hunley’s final location, so close to Housatonic seems to indicate that the submarine had not navigated away from the site underwater.

THEORY 3: A Federal vessel struck the Hunley on the surface

Neyland writes: “The least likely scenario is that Hunley was struck by Canandaigua as it came to render assistance. Had this been the case, the submarine would likely have suffered massive damage to the hull, possibly even been cut in half.”

THEORY 4: Damage to conning tower caused by small weapons fire, causing the sub to flood

The report states: “The recovery did not reveal a large breech caused by the explosion that led to catastrophic flooding … the damage to the forward conning tower could have been caused by gunfire or shrapnel from the explosion, but should not have been enough to sink the vessel. However, the concussion resulting from the detonation of the torpedo would have created an underwater shock wave and the force could have been severe enough to damage the hull or the crew. … It is possible this could have caused distortion or fracturing of the metal components of the hull, allowing water to enter around rivets or seams, and physical injuries to the crew.”

Damage to forward conning tower (Friends of the Hunley)

Neyland argues a slow leak would be consistent with a report that Hunley remained at the surface after the explosion. “It seems likely the crew would have attempted to stop the leaks and man the pumps, and, if unable to do so, they would have had sufficient time to unfasten both hatches and abandon the submarine to escape. If, on the other hand, the crew was disoriented or disabled by the shock wave, there is a chance slow leaks went unchecked and the boat slowly sank without an attempt to stop it.”

The report indicates an examination of Dixon’s remains showed no evidence he was hit by enemy fire.

THEORY 5: Crew tried to use grapnel anchor

Facial reconstructions (Picket photo)

This theory holds the discovery of a grapnel anchor at the wreck site indicates the Hunley’s crew used to the anchor to combat the outgoing tide until the tide change “but were inadvertently pulled under due to the low freeboard of the submarine and lack of buoyancy.”

Neyland writes no historic accounts mention the deployment of an anchor and he said the one found was too light for the purpose. It’s possible another vessel lost the anchor while the U.S. Navy dragged the waters for Hunley.

THEORY 6: The crew was rendered unconscious

That scenario contends the men were unable to man the pumps or respond to any damage

Some of that argument is covered in Theory 4, but Neyland writes there’s a possibility “that the crew was sufficiently disoriented from the explosive shock wave that they were unable to respond efficiently to the danger of hull leakage. If they lost their interior light and were unable to relight the candle or lantern soon after the explosion, their situation would have been compounded.”

Interestingly, the Navy also this week released findings of a team looking into the effects of the explosion on the crew; it’s known the torpedo was attached to a spar connected to the Hunley when it went off.

(U.S. Navy)

It found the “imparted load” of the blast to the submarine was “relatively modest.” The primary response of the Hunley to the explosion was a rapid vertical motion resulting from the flow of water around the bubble.

“While the occupants may have experienced some bumps and bruises, it does not appear there was enough force to cause concussion or other forms of complete incapacitation."

That report cites a broken outlet pipe in the forward ballast tank. It would have allowed water to flow into the crew compartment. “Tests revealed that the vessel would sink in approximately 3 minutes from the initial failure of the pipe.”

But, like much of the report, this team found mysteries remain. It said examination of drift models show something more than the pipe alone may be responsible for the sinking.

In his summary, Neyland discounts the Hunley being struck, the grapnel anchoring and damage alone to the forward conning tower.

“Given the lack of a proverbial ‘smoking gun,’ it is possible that several smaller problems occurred simultaneously that, when combined, could not be overcome.”

The research and conservation of the vessel at the Warren Lasch Conservation Center in North Charleston, S.C., continue. Reports documenting the excavation of the interior, including crew remains, personal effects and hull components will be published later, the Navy said.