 Around 6:30 p.m. on February 17, 1864, eight men crammed into the Confederate submarine H. L. Hunley, a self-propelled metal tube attached to a bomb, and slipped quietly into the freezing black water off the coast of Charleston, South Carolina. By 9:00 p.m., it was over: The Hunley had thrust its spar-mounted torpedo into the Housatonic’s hull and within seconds, 60 kilograms of black powder had caved in the ship. Its demise has baffled scores of researchers and Civil War buffs for more than a century. If she’s right, the mystery of the Hunley may finally be put to rest. “It’s quiet there so we can talk.” 
 
 Lance was modeling an underwater explosion at a computer in Duke’s Injury Biomechanics Lab, where she studied blast injuries, when her adviser had the epiphany that set her Hunley obsession in motion. But while the sub’s fate was finally revealed, it still wasn’t clear what transpired during the military engagement, and what led to the death of its eight seamen. Then, she remembered thumbing through a newsletter published by Friends of the Hunley, a nonprofit in Charleston that handles outreach, fundraising, and development for the Hunley Project and runs tours at Clemson’s Warren Lasch Conservation Center where the Hunley is being restored. Suffocation was not a plausible explanation for why the Hunley sank. Through her research, Lance learned of the damage to the conning tower and the so-called lucky shot theory: a stray bullet fired by Housatonic sailors during the attack punctured the tower, causing the sub to fill with water and sink. At the other end of a hinged 16-foot spar was firmly bolted the Hunley’s torpedo, a copper torpedo of the common Singer’s design type filled with 61.2 kg (135 lbs) of black powder and fitted with a pressure-sensitive trigger ( S1 Fig )[ 4 ]. Therefore, test data were only used for the analysis of scaling if they had the same charge orientation and depth as the tests with the scale boat model, and gauge locations that would fall along the length of the submarine hull. The Tiny model was blasted with black powder charges of three sizes: 283 g and 455 g charges, corresponding to 1/6 and 1/5 size scale of the 61.4 kg (135 lb) Hunley torpedo, and 1 kg charges, which were the maximum size as requested by the ATF. Key physical design properties of the Hunley were incorporated in the scale model construction, including ballast tanks that could be filled with water and ballast weighting by lining the keel with lead. "Initially, when she was talking about blasting, I was a little concerned," said Pitt, 65, a sixth-generation family farmer, whose grandchildren now make eight generations. Without a trace 
 
 Suspended inside the CSS Tiny was a small pressure gauge, which revealed how the sub's own torpedo blast could have killed the Hunley crew without leaving a lasting mark: the shock wave created by the blast. "Something traumatic -- perhaps water, a shock wave, or some other intervening force -- caused it to stop at that precise time." Once it was determined that the bow of the vessel transmitted negligible blast effects into the main cabin, and the perpendicular component of the blast was responsible for blast transmission into the cabin, the transmission tests were performed by directing the shock tube perpendicularly at the side of the hull. The blast produced likely caused flexion of the ship hull to transmit the blast wave; the secondary wave transmitted inside the crew compartment was of sufficient magnitude that the calculated chances of survival were less than 16% for each crew member. Taylor’s dimensional analysis and subsequent studies by other groups concluded that the amount of momentum transferred into a structure by a blast wave can be scaled by size if the time-relevant parameters of the blast wave are also scaled [ 22 , 23 ].
– For more than 150 years, researchers have scratched their heads over a Civil War mystery—and now a Navy engineer says she's solved it. Rachel Lance has been diving deep into the 1864 sinking of the Confederate submarine HL Hunley, which mysteriously went down shortly after sinking the Union's USS Housatonic sloop with a torpedo, reports a Hakai Magazine article posted at Smithsonian.com. Over three years, Lance—a Duke grad student with no experience in forensics, no help from experts who'd long been on the case, and no access to the excavated sub itself—carried out what Gizmodo calls an "exhaustive … analysis" and finally arrived at a conclusion published in PLOS ONE: that the torpedo created blast waves that pierced the Hunley's hull and instantly killed the eight crew, whose skeletons were found intact during the sub's excavation near Charleston, SC, in 2000. Lance looked at other theories swirling around the Hunley's fate, including low oxygen or a bullet fired by the Housatonic that punctured the sub. She became obsessed, to the point she'd zone out during meals. "There was something viscerally terrifying about the fact that eight people died that night, and we had no idea how or why," she tells Hakai. Her injury biomechanics background finally led her to her shock wave theory. "When blast waves hit an air space, they slow down like a car hitting a wall," she says. "Except in this case, the wall is the surface of the lungs." A mini replica of the Hunley she dubbed the CSS Tiny and a series of test explosions in a rural pond helped her prove her theory, per CNN. Other researchers remain unconvinced, but Hakai says now Lance's theory is "their theory to disprove." More on her project here. (The Hunley looks a lot better these days.)