Civil War submarine mystery solved

Nature reports on researchers who have determined that the Confederate Navy’s Hunley – the first submarine to sink an enemy warship – probably sank itself when its own torpedo-ram exploded:

The Confederate craft famously disappeared with all its crew on 17 February 1864, just after destroying the USS Housatonic in Charleston Harbour. The Hunley’s wreck was not found until 1995. When it was raised from the seabed in 2000, the skeletons of its eight-man crew were still at their stations, with no evidence of escape attempts.

Since then, archaeologists and conservationists have pored over the submarine, which is kept at Clemson University Restoration Institute in South Carolina, for clues to its destruction.

“The pressure wave from the explosion was transmitted into the submarine. It was sufficiently large that the crew were killed,” [says Rachel Lance, a graduate student in injury biomechanics at Duke].

Lance and other researchers simulated the explosive forces the crew experienced by blowing up a scale model dubbed the USS Tiny, one-sixth the size of the Hunley, while it was submerged in a farmer’s pond.

The Hunley’s only weapon was a black gunpowder-filled copper cylinder — “about the size of a beer keg”, says Lance – attached to a 6.7-metre pole mounted on the bow.

In 2013, the theory that the explosion from this cylinder had affected the Hunley’s own crew gained credence when researchers established that the submarine was still attached to the explosive charge when it went off.

Lance and other researchers blasted the Tiny with increasingly large black-powder charges, and used sensors to measure the peak pressure experienced inside the midget submarine. Lance then used equations to scale up the blast to match that which struck the crew of the Hunley, which had a much thinner hull than modern submarines do.