The HL Hunley – one of the world’s first submarines, and the first to sink a battleship – sank on 17 February 1864 in mysterious circumstances after torpedoing the USS Housatonic near Charleston Harbour, South Carolina, during the American Civil War, but now the mystery has finally been solved.
It was always assumed the blast of the torpedo hitting the battleship had ruptured the hull of the submarine, drowning the crew, but when the Hunley (which was only discovered in 1995) was raised by salvage experts in 2000, they were amazed to find the eight-man team onboard sitting at their posts and ready for action, as if they had been caught completely unawares and made no attempt to escape the stricken vessel.
Now researchers at Duke University believe they have discovered the truth – that the crew accidentally killed themselves – after spending three years experimenting on a mini test sub. These tests have shown that the blast of the torpedo would have created a shockwave that was great enough to instantly rupture the blood vessels in the lungs and brains of the submariners and instantly kill them.
Unlike modern torpedoes, the Hunley's was not a self-propelled bomb, but instead comprised of a copper keg of 135lbs of gunpowder that was held ahead and slightly below the sub’s bow on a five-metre pole called a spar. The idea was that the submarine would ram this spar into the enemy ship's hull and the bomb would explode, but this meant the furthest any of the crew was from the resulting blast was only 12 metres or so. The blast’s shockwave would have travelled about 1,500 metres per second in water, subjecting the Hunley’s crew members to some 60 milliseconds or more of trauma (a normal shockwave blast through air lasts less than ten milliseconds) and the subsequent catastrophic injuries would have killed the crew instantly.