The U.S. Navy's new aircraft carrier design, to be designated CVN-21, will contain a number of new features. It will automate a lot of jobs, reducing crew size by 800. A new nuclear power plant design will generate three times as much electricity as older ones. The new carrier will make extensive use of computer networking and flat screen computer displays. PDAs and portable CD-ROM readers will replace most manuals and reference works sailors use while doing maintenance. Construction will begin in 2007. One future weapon planned for the CVN-21, a electromagnetic rail gun, will not be ready when the carrier is built. But space, and electrical capacity, will be available on the ship for the rail gun, which uses magnetism to propel projectiles some 300 kilometers. The carrier will probably also make heavy use of unmanned aircraft (UAVs).