The U.S. Navy is going back to the breakers (where ships are broken up for scrap). Four retired aircraft carriers (USS Constellation, USS Forrestal, USS Independence and USS Saratoga) are to be scrapped instead of sunk, or simply allowed to rust away while tied up. These ships were taken out of service between 1993-2003, and have been waiting since then while a decision was made on their disposition.
For over a decade, sending warships to the scrap yard was not considered a viable alternative. It's all about pollution, bad press and cost.
For thousands of years, unneeded ships were "sent to the breakers" (a shipyard that broke the ship up for scrap and reusable parts). However, this is now considered environmentally harmful if done the old fashioned way (as it is still done in countries like India), and too expensive if it is done in an environmentally (and politically) acceptable way. In other words, it could cost more to scrap warships than you would recover from the value of the recycled metals.
Another use for retired ships is as museum ships. Two years ago, the U.S. Navy retired its last non-nuclear aircraft carrier, the USS John F. Kennedy. The navy offered the ship to any government or non-profit organization that wants to maintain it as a museum ship. The navy is still waiting for a response. Entering service in 1968, the Kennedy is 321 meters (1052 feet) long and displaces 82,000 tons. It would be the largest museum ship ever. The ship is currently docked in Philadelphia, and there is much enthusiasm in Boston for taking the carrier, named after a native son, and establishing a museum ship. The big problem, for whoever takes the ship, is money. Lots of money. Hundreds of millions to outfit the ship as a museum and maintain it.
The navy has long been willing to donate old ships to groups that were willing to maintain the retired vessels as museum ships. But the navy attaches some very expensive strings. That is, the navy expects the ship to be kept in decent shape. This is a problem with many old metal ships, as they rust. And eventually they rust so much that the hull is breached, and ultimately will collapse.
For example, one museum ship, the World War II era, Essex class carrier USS Intrepid, in New York City, returned to its display berth in 2009, after a two year refurbishment, costing $120 million. The entire hull was examined, in dry dock, for decay, and over a hundred square meters (nearly a thousand square feet) of hull had to be replaced. A sister ship of the Intrepid, the Yorktown, requires a similar refurbishment. Since 1975, the Yorktown has been on display in Charleston, South Carolina, with several other museum ships. The Yorktown, which entered service four months before the Intrepid, needs the same kind of work. The navy is insisting on it, with the alternatives being sending the ship to the breakers or a lawsuit. The naval museum in South Carolina is in a bad situation, as $120 million is hard to find, even when the economy (and wealthy donors) are doing well. The big donors are much harder to find these days.
Another popular option is to use old ships for target practice. For example most of the 30 decommissioned Spruance class destroyers were used for target practice. Some old warships are sunk closer to the shore, to provide reefs for fish and scuba divers. Running a SINKEX (sinking exercise) enables the navy to test some theories on how vulnerable, or invulnerable, modern warships are. But environmentalists oppose these two methods as well, because it puts toxic materials into the ocean.
Going to the breakers is now seen as viable because of more efficient breaking techniques, and higher prices for recycled metals. For the moment, anyway.