Undertaking a fundamental change in the way its ships are powered, the Navy announced a $25 billion plan yesterday to build a new class of destroyers propelled with stealthy yet efficient electric motors and capable of generating enough wattage for futuristic weapons such as lasers or electromagnetic launchers.

Comparing the development of the "electric drive" to the switch from sail to steam, Navy Secretary Richard Danzig told a news conference the new propulsion system will "change the character and power of our forces" and allow a destroyer to operate with a crew of fewer than 100--compared with 300 today--each of whom will have a private stateroom instead of a rack in sleeping quarters shared by as many as 60 sailors.

With an investment of $3 billion to $5 billion in research and development on the DD 21 class of destroyers over the next five years, Danzig said, the Navy hopes to perfect an entirely new approach to shipbuilding and design, which will then be applied to other vessels.

The key change involves the way in which power is delivered to a ship's propeller. In today's destroyer, an engine, usually a gas turbine, is linked to a long drive shaft and reduction gears that convert the engine's revolutions to the right number of turns for the propeller. This requires the main engines to be placed low in the ship, as well as large air intake and exhaust ducts to pass through the middle of the ship. Separate engines run generators to produce electricity for all other equipment, from radar to gun turrets.

Electric-drive ships will have conventional engines connected to new, highly efficient generators. Electrical power will travel by cables to motors connected by short drive shafts to the propellers, or perhaps in the future, thruster systems. In addition, the same generators will feed the rest of the ship with a supply of electricity far more abundant than is available from auxiliary generators today.

Similar technology is at work today in huge cruise ships, making them roomier and more fuel-efficient, said Rear Adm. Joseph Carnevale, executive officer of the DD 21 program. The Navy, however, must boost the wattage significantly and make the engines and generators rugged enough for battle. The new destroyer, with a 12,000-ton displacement, will need more than twice the electrical power now consumed by a 100,000-ton electric-drive cruise ship, Carnevale said.

Although no systems capable of delivering this kind of power exist, the Navy is so confident that electric drive is the way of the future that Danzig said delivery of new destroyers, now slated for 2008, might be allowed to slip and other ship-building programs might be trimmed to keep the DD 21 fully funded.

Plans call for the production of 32 destroyers, each equipped with a pair of large guns and a cluster of missile-launching tubes primarily intended for land attack missions, such as the Kosovo air campaign or the bombardment of Iraq during the Gulf War. Those sorts of missions, carried out in coastal waters, expose surface ships to mines and submarines, said Adm. Michael G. Mullen, director of the Navy's surface warfare division.

"For ships at sea, quieter is better," Mullen said. The elimination of the reduction gear and the long drive shaft will make the DD 21 much quieter than current surface combatants, and thus better able to avoid damage from mines and submarines, which often use noise to locate targets, Mullen said.

"I'll be able to proceed into areas where I can remain undetectable because of that significant noise reduction," Mullen said.

In current designs, engines and generators are located low in the ship. With an electric drive, they could be anywhere because they will be connected to the motor that propels the ship by cables. Moreover, the engines and generators can perform interchangeable functions.

"If I do take a hit, I will be able to instantaneously, in ways that I have not been able to accomplish thus far, reroute my power, reconfigure my ship, in a way that allows me to survive better and to handle that damage, as well as to continue to fight," said Mullen.

Under a new acquisition system authorized by Congress, two competing teams of defense contractors--one led by Bath Iron Works and Lockheed Martin Corp. and the other by Ingalls Shipbuilding and Raytheon Corp.--have been working since 1998 on designing the ship with the Navy guiding them separately with specifications.

The Navy will pick one of the designs, a decision that could come as early as this summer, and then eventually both teams will participate in the production of the new ships.