In February of 1864, eight Southern soldiers climbed into an iron tube fitted with a propeller that was designed to go underwater as the first real attempt at a military submarine used in combat.

At the front end of that iron tube was mounted a 135-pound keg of gunpowder attached to a 16-foot pole called a spar. The idea was to move in stealth under the waves to ram an unsuspecting ship, attach the bomb, then reverse direction, whereupon eventually a rope would trigger the bomb and explode the ship. 

On the 17th of that month those eight men carried out their mission, and The Hunley successfully sank the Union steamer Housatonic in Charleston Harbor, the first-ever submarine to sink an enemy ship.

However, the submarine and her crew were never seen again — at least until the craft was raised from the bottom of the harbor in 2000. 

Upon inspection, researchers were stunned to discover all eight crewmen still at their respective posts with no evidence of panic or even an attempt to escape the doomed vessel by any of them. The craft was remarkably intact, with minimal damage overall. 

For now 19 years scientists and historians have painstakingly worked to solve the mystery of the sinking of the Hunley and the death of her crew. Initially, the discovery of the submarine only seemed to deepen the mystery. The crewmen’s skeletons were found still at their stations along a hand-crank that drove the cigar-shaped craft.

They suffered no broken bones, the bilge pumps had not been used and the air hatches were closed. Except for a hole in one conning tower and a small window that may have been broken, the sub was remarkably intact. Speculation about their deaths has included suffocation and drowning.

In fact, all kinds of theories have been offered, each eventually dismissed. 

But finally, the answer of what happened to the Hunley and her crew may have finally been found.

After three years of experiments on a mini-test sub, researchers at Duke University have shown that the torpedo blast would have created a shockwave great enough to instantly rupture the blood vessels in the lungs and brains of the submariners.

“This is the characteristic trauma of blast victims, they call it ‘blast lung,’” said Dr. Rachel Lance. “You have an instant fatality that leaves no marks on the skeletal remains. Unfortunately, the soft tissues that would show us what happened have decomposed in the past hundred years.”

When the explosion occurred, the furthest any of the crew was from the blast was about 42 feet. The shockwave of the blast travelled about 1,500 meters per second in water, and 340 m/sec in air, the researchers calculated.

While a normal blast shockwave traveling in air should last less than 10 milliseconds, Lance and her researchers calculated that the Hunley crew’s lungs were subjected to 60 milliseconds or more of trauma.

“That creates kind of a worst case scenario for the lungs,” added Lance. “Shear forces would tear apart the delicate structures where the blood supply meets the air supply, filling the lungs with blood and killing the crew instantly. It’s likely they also suffered traumatic brain injuries from being so close to such a large blast.”

The new study involved repeatedly setting blasts near a scale model, shooting authentic weapons at historically accurate iron plating, and calculating human respiration and the transmission of blast energy.

“All the physical evidence points to the crew taking absolutely no action in response to a flood or loss of air. If anyone had survived, they may have tried to release the keel ballast weights, set the bilge pumps to pump water, or tried to get out the hatches, but none of these actions were taken,” Lance concluded.

For many sailors, the theory makes perfect sense, as depth charges have been used effectively to cripple submarines since World War I. A depth charge is merely an explosive device that is set to detonate at a depth near that which a submarine would occupy — almost precisely what happened with the Hunley. 

The damage an underwater explosion inflicts on a submarine comes from a primary and a secondary shock wave. The primary shock wave is the initial blast wave from the depth charge, and will cause crippling if not catastrophic damage to personnel and equipment inside the submarine if detonated close enough. The secondary can cause enough structural damage to the craft to sink it. 

All added up, the stunning conclusion is that in detonating the bomb that sunk the Housatonic the Hunley crew essentially killed themselves. 

It has been said that desperate times call for desperate measures. These men allowed themselves to become human guinea pigs, climbing into a crude submergible iron tube built to plant a bomb to explode beside them, a mission with no historical precedence that was almost certainly going to bring them to a cold, watery grave. 

Yet they did so — apparently not only willingly but eagerly. 

Here 155 years removed, it would be understandable to question whether those eight men climbing into that crude submarine constituted an act of bravery or foolishness. You could argue either stance. 

But I would further argue that depending on the circumstance, the dividing line between brave and foolish might become quite thin — if not outright indiscernible. 

Probably much like it did on February 17, 1864.