(2 of 2)
If Trieste proves the case for a 12,000-ft. sub, its design may be strange. Since only the crew and controls need protection from pressure, all the power and ordnance equipment of such a sub could ride "outside" them in an outer hull filled with oil. Like the thin steel of the bathyscaphe's gasoline float, which feels no appreciable pressure, the sub's outer hull need not be thick and pressurized. It could be made of lightweight aluminum or lithium for greater speed.