The story of military history is full of brilliant technological innovations. From the recurve bow to the main battle tank, humans have continued to come up with increasingly efficient ways of killing one another. Yet for every great invention there are dozens of duds - technological dead ends, creations ahead of their time, and all-round bad ideas. Today we're looking at one of those more ignominious creations, a submarine that killed more of its own crew than the enemy: the Confederate States of America's H. L. Hunley.