While Becky (my wife) and I were in South Carolina for the educator’s fall break, we made arrangements for visiting the recovered H.L. Hunley in Charleston. 

    The H. L. Hunley, often referred to as Hunley, was a submarine of the Confederate States of America that played a small part in the American Civil War. Hunley demonstrated the advantages and the dangers of undersea warfare.

          H. L. Hunley was an experimental submarine built by Confederate civilian engineers during the Civil War. Powered by a hand crank operated by seven men with one pilot, the 40-foot long boat was built of wrought iron boiler plate with custom cast iron fittings.

     It was designed to submerge beneath an enemy vessel while towing a torpedo behind, which would strike the hull and detonate. After several fatal accidents, the military authorities working with the submarine in Charleston, South Carolina, ordered the boat be operated only at the surface, with a spar-mounted torpedo at the bow.

       On the night of 17 February 1864, the crew, under the direction of Lt. George Dixon, left their base on Sullivan’s Island on the four mile journey to the outer ring of ships blockading the entrance to Charleston Harbor. Their target was the 1240-ton steamship USS Housatonic.  

     Approaching silently in darkness, witnesses reported seeing something at the surface that resembled a floating log that was moving against the current. Raising the alarm, they began firing with rifles and muskets, but it was too late – the intruder made contact and, shortly thereafter, an explosion shook the Union vessel. Within minutes it was resting on the seabed. Five men were killed in the attack; however, most of the crew was able to cling to the rigging, which remained above water, until rescue arrived. From that vantage point, one witness reported seeing a light at water level in Hunley’s position. That is the last surviving potential sighting of the submarine and its crew of eight.

     Hunley, nearly 12 m long, was built at Mobile, Alabama, and launched in July 1863. She was then shipped by rail on 12 August 1863, to Charleston. Hunley sank on 29 August 1863, during a test run, killing five members of her crew. She sank again on 15 October 1863, killing all eight of her second crew, including Horace Hunley (the founder)  himself, who was aboard at the time, even though he was not a member of the Confederate military.  Both times Hunley was raised and returned to service.

Hunley did not survive the attack on the USS Housatonic, and also sank, taking with her all eight members of her third crew, and was lost.  Finally located in 1995, Hunley was raised in 2000, and is on display in North Charleston, South Carolina.  This is where Becky and I visited the recovered craft.

     From the recovered Hunley, archaeologists learned a great many interesting things about the design of the submarine and the lives of the people on board, but they still could not explain why the boat sank in the first place. Could the explosion have led to hull distortion allowing water in at the seams? Was the crew incapacitated by the explosion effects? Was the vessel so unstable that taking on a small amount of water from the conning tower hole could become an unrecoverable event?    Apparently the answers to all these questions was a “NO!” 

     Scientists performed numerical simulations of the explosion, the imparted load to Hunley, and the loads imparted by Hunley’s hull to the crew.  It was found that while the loads to the Housatonic would have been devastating, the loads to Hunley are relatively modest, despite the small amount of standoff to the explosion.  This is due to Hunley’s location from the explosion (7m).  The submarine would have been just far enough away to not be impacted by this explosive pressure wave.

     It was noted that the Hunley had traveled 360m from the explosion and the USS Housatonic wreckage.  If Hunley were drifting under no power, it would have taken approximately 13 minutes to reach a point 360 m from Housatonic. Given that this is much longer than the time necessary to sink the vessel, it suggests that something more than just the pipe alone may have been responsible for the loss of the vessel. Perhaps some of the crew were still turning the crank to move the vessel, or attempting to stem the flooding. At the vessel’s higher sprint speed, it could cover the estimated distance in time. However, if the crew was able to maneuver the vessel, why did they make no effort to escape?   

     A possible hypothesis from an Archeologist working at the site told Becky and I that Hunley crew probably survived the explosion and  stopped to celebrate their success without coming to the surface. This may have caused a Carbon Dioxide poisoning of the crew.  The result was that the H.L Hunley sank without the propulsion of the passed out 8 man crew of Carbon Dioxide poisoning .