NORTH CHARLESTON, SC (AP).- A decade after the raising of the Confederate submarine Hunley off the South Carolina coast, the cause of the sinking of the first sub in history to sink an enemy warship remains a mystery. But scientists are edging closer. 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. Early next year the 23-ton sub will be delicately rotated to an upright position, exposing sections of hull not examined in almost 150 years. When the Hunley sank, it was buried in sand listing 45 degrees to starboard. It was kept that way as slings were put beneath it and it was raised and brought to a conservation lab in North Charleston a decade ago. Sunday