Researchers uncovered clues that suggest the H.L. Hunley, a Confederate submarine during the Civil War, was less than 20 feet from its Union ship target when its torpedo exploded. The find suggests that crew members were intentionally detonating the weapon and not on a suicide mission. Researchers say it helps explain why the Hunley disappeared after successfully sinking the Union ship in 1864. "You have to remember, what these guys were trying to do had never been done before. They were constantly improving their new weapon as they learned during testing," said senior Hunley archaeologist Maria Jacobsen.