The Navy's submarine force is in trouble. A shrinking number of boats is struggling to meet steady demand from regional commanders. Meanwhile, the cost of the only U.S. submarine currently in production, the super-high-tech Virginia-class attack boat, has risen to $2.3 billion apiece. At that price, the Navy can afford to buy only one per year. Do the math: since attack boats last only 30 years, building one boat per year means your fleet is eventually going to shrink to 30 boats from the current 55. Long-range plans call for 48 attack subs, so how is the Navy going to...