A decade after the raising of the Confederate submarine Hunley off the South Carolina coast, scientists are edging closer to finding out how the first sub in history to sink an enemy warship was, in turn, itself destroyed.

On Friday, scientists announced one of the final steps that should help explain what happened after the hand-cranked sub and its eight-man crew rammed a spar with a powder charge into the Union blockade ship Housatonic off Charleston in February, 1864.