Sailors and their families have grown accustomed to Washington, D.C., showdowns. But this latest one may be the gravest, as the shuttered American government lurches closer to a possible default on its national debt – now about 12 hours away. A default imperils the government’s ability to pay its bills, including military pay and veterans’ benefits. Economists believe it will throw the world economy into a crisis, as the U.S. is the world’s largest economy and holds the largest debt. And long term it would likely diminish the military’s size and power, as the nation would no longer be able…