Mysterious disappearance of a civil war sub solved

On a winter night off the coast of South Carolina, towards the end of the American civil war, eight men got into a prototype submarine called the H.L. Hunley. The sub had already sunk twice, killing 13 members of its crew. And this time, as if it weren't dangerous enough, they had attached a torpedo — really just a bomb on a pole — to the front of the sub.

They moved just at the surface of the water, using hand cranks to turn the propeller. They pressed the torpedo against the hull of the Union ship the USS Housatonic, and set it off.

The Hunley became the first submarine to sink an enemy ship, but it never came back. What happened to the sub was a mystery.

When the sub was finally found and then raised, the wreck didn't immediately provide any answers. The remains of the crew didn't show any broken bones or injuries, and the only holes in the sub were from a hundred years of rust. 

Researchers from Duke University, including lead author Dr. Rachel Lance from the Department of Biomedical Engineering, now think they've solved that mystery. 

Dr. Lance says that the lack of apparent injuries and that they remained in their positions pointed to blast injuries. The shock from the exploding torpedo would have killed the men instantly, causing bleeding in their lungs and brain, but leaving them otherwise unharmed. Since no soft tissue remained of the men on the sub, their skeletons would show no sign of the blast that killed them.

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Dr. Lance also tested two other theories. One suggested that they men may have suffocated, but found that to be unlikely since they would experience the effects of lack of oxygen long before it knocked them out. The other, called the "lucky shot theory", suggested that a Union soldier on the Housatonic could have shot the sub and caused it to sink. But the only holes in the sub were from rust and the fact the sub drifted away from boat, rather than sinking straight down, were evidence again that the blast theory was right.

Paper in the journal PLOS ONE, "Air blast injuries killed the crew of the submarine H.L. Hunley"