There is a saying in the Navy that there are only two types of ships: submarines; and, targets.

The US Civil war marked the sudden obsolescence of the wooden sailing warship, and so they were replaced – against the will of most senior naval staff. The arrival of the aircraft carrier marked the end of the iron clad battleship. They too were replaced – against the will of most senior naval staff. Inevitably, the time will come when the carriers also become obsolete due to technological change making them too vulnerable.

In the absence of naval war on a scale large enough to involve these capital ships and demonstrate their vulnerability, we may not notice when their time has come, and it is unlikely that the senior naval staff will tell us. These ships look so magnificent and invulnerable, and they are a great place for the Admiral commanding to give a dinner party. So were the battleships, and the wooden ships of the line!

For some years now there have been leaks from various naval exercises that cheap but very quiet diesel submarines from friendly countries have been able regularly to “sink” our largest supercarriers. It is not uncommon for them to be able to get so close as to take a trophy under-water photograph of the carrier’s propellers through the periscope. This happens in spite of all the sonar technology these battle groups can deploy.

Submaries may not be the greatest threat. Increasingly missiles and UAVs can guide themselves, or be directed remotely, over long distances to home in on a small target. It would be optimistic to assume that our naval enemies will not have that capability. Missiles can often be knocked down, especially if they come in one by one and don’t over tax the radars, but will the enemy cooperate like that?

Mines are getting more sophisticated. There are torpedoes now that can lie dormant on the sea floor for months, waiting to hear the sonar signature of a particular ship. When they hear it they will activate, and home in on it at very high speed.

When so much is invested in human lives, money and national security, we need to ask these questions. If this country ever came to a conflict in which these mega ships were deployed, the effect on morale of them being quickly sunk would be devastating. We might have been better prepared, and the oportunity cost could lose us the war.

The cost. Modern super carriers generally price at about $6 billion each, but this is only the beginning. There is also an equally costly air wing to consider (about 90 planes at $50 million each for the US ships), plus 3-5 escorts ships and at least 1 attack submarine at $2 billion each for protection, plus 6000 crewmen, and $300 million per year on upkeep. And they wonder why our fleet has sunk from 600 ships to less than half since the last decade.

Here are five reasons why the aircraft carrier was obsolete (in 2007).

This article was edited after publication by the author on 24 Aug 2009. View changes.