What will the threats be over that period of time? How many of these $12 billion fighting machines does the United States need? Does the carrier fleet get sized for peacetime or for war? Does their mere presence in an area deter war? Are the president and Congress taking a long-enough view in making their decisions?

At Monday’s Senate Armed Services Committee hearing, Defense Secretary Leon E. Panetta said of the proposed fiscal 2013 budget: “We’ve maintained the 11 carriers in the Navy in order to ensure that we have sufficient forward presence. There’s nothing like a carrier to be able to allow for quick deployment. . . . And that’ll give us a great capacity to be able to show our force structure in the Pacific.”

But as Navy experts say, you need that number just to keep one in the Indian Ocean, another in the Western Pacific, and enough in reserve for contingencies, such as today’s need to keep two available for South Asia/Middle East use. The general standard for carriers is seven months on station and 25 months at home port or dry dock.

The nuclear ones also must have their power generators refueled. For example, the new budget contains $1.6 billion to refuel the reactor of the USS Abraham Lincoln, which just days ago passed through the Strait of Hormuz after weeks in the Persian Gulf aiding in the Afghan war. Refueling beginning in the next 12 months will keep the Lincoln out of action for a year.

The new fiscal 2013 budget contains no money for CVN78, the USS Gerald R. Ford, although the Navy has identified the need for another $881 million for cost overruns in what has become a $12.3 billion ship. Its funding began in 2001, and money to pay off the overruns has been pushed into the fiscal 2014 and 2015 budgets.

The first of a new class of nuclear-powered carriers, the Ford is projected to save money in the long run by having a new reactor power plant that requires 50 percent fewer people to run it while generating far more electricity than the previous class of nuclear carriers. Overall, including the flight crews, the Ford will have some 3,800 personnel. That’s almost 1,200 less than the current carriers.

Of course, the Ford has had its problems. It became a test bed for new equipment and construction techniques. Along with the new power-generating nuclear reactor, the Ford will have a new electromagnetic catapult-launching system and a new phased-array radar to replace five radars on the earlier carriers.

The catapult-launching system had to be built and then tested on land, since there was no ship deck built that could handle it. Those tests are ongoing at a site in Lakehurst, N.J., while parts of the finished system have begun to be installed in the Ford, which is being built at the Huntington Ingalls shipyard at Newport News, Va.