(CN) – After an exhaustive three-year analysis by a team of researchers, the mysterious fate of the crew that manned the first combat submarine to sink an enemy ship has been revealed.
A research team from Duke University’s biomedical engineering doctoral program say the H.L. Hunley, a Confederate submarine active during the Civil War, saw its entire eight-man crew killed due to the force of a blast wave created by the ship’s “torpedo.”
“All the physical evidence points to the crew taking absolutely no action in response to a flood or loss of air,” said Rachel Lance, a 2016 graduate of Duke Engineering.
The H.L. Hunley managed to use its ship-mounted torpedo on February 17, 1864, sinking the U.S. Navy sloop-of-war the USS Housatonic in about 30 feet of water just outside Charleston Harbor, South Carolina.
The large crew of the Housatonic rescued themselves as the sloop sank, by waiting in the riggings and deploying lifeboats. The minor naval battle is less interesting for its strategic importance in the overarching direction of the Civil War, than for the mysterious fate of the submarine that became the first in human history to sink an enemy ship.
Light was shed on the mystery when the H.L. Hunley was finally located in 1995 by a dive crew. Subsequently, the vessel was raised in 2000 and that was when researchers noticed that all eight skeletons of the crew were not only largely intact, all were manning their stations as if frozen in the moment of battle.
This positioning of the crew, combined with the fact they suffered no broken bones, the bilge pumps were unused and the air hatches were closed meant it was unlikely they were struck by an enemy ship. Furthermore, the submarine was found largely intact.
Instead, Lance and her team believe a blast wave, created when the H.L. Hunley fired a torpedo, created an acute lung ailment in all 8 of the crew that killed them more or less instantly.
The Hunley’s torpedo was not a self-propelled bomb as we think of them now. Instead, the vessel held a copper keg of gunpowder on a 16-foot spear-like apparatus that extended from just below the bow. The explosion was caused by ramming ships, meaning the farthest the crew could get from the explosion was about 42 feet.
This proximity to the blast ultimately proved fatal for the Hunley’s crew as the shockwave acted on their soft tissue, especially their lungs and brains. With the crew incapacitated, the submarine drifted out to sea several hundred feet, took on water and sank.
“This is the characteristic trauma of blast victims, they call it ‘blast lung,'” said Lance, who worked as a biomechanist at the U.S. Navy’s base in Panama City, Florida, for three years before entering graduate school at Duke. “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.”
Blast lung is unique to the underwater environment, as the shockwave travels 1,500 meters per second in water, and 340 meters per second in air.
“When you mix these speeds together in a frothy combination like the human lungs, or hot chocolate, it combines and it ends up making the energy go slower than it would in either one,” Lance said.
This slowing of the wave extends the amount of damage to soft tissue like lungs and brains. Lance said that when it crossed the lungs of the crewmen, the shockwave was slowed to about 30 meters per second, resulting in about 60 more milliseconds of trauma.
“That creates kind of a worst-case scenario for the lungs,” Lance said. “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.”
The proximity of the crew to the blast also meant they likely suffered traumatic brain injuries, most of which were likely to be fatal.
Lance and her researchers used scale models placed next to repeated explosions, shot weapons at historically authentic iron plates and did copious amounts of mathematical equations relating to human respiration to come to their conclusion.
The submarine appeared fated for some kind of disaster from the beginning. It sank twice during testing, killing 13 crewmen including the inventor H.L. Hunley, who designed the vessel from a defunct boiler.
Furthermore, it is likely those involved with the submarine knew that the powder keg was too close to the vessel and its crew. Lance found historical records that showed people stayed hundreds of feet away from the powder kegs during testing.
Most of those powder kegs were significantly smaller than the one that eventually sank the Housatonic.
“Blast travels really far underwater,” Lance said. “If you’re practicing 200 yards away, and then you triple the size of your bomb and put it 16 feet away, you have to be at least aware that there’s a possibility of injury.”
Unlike the many and varied hypotheses that have sprouted after the raising of the submarine in 2000, Lance’s theory accounts for the unusual arrangement of crew members still manning their stations with no discernible injuries.
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,” she said.