web site with general information about CVN-21
The USS Bush started as CVNX-1, and was to be the first "Next Generation" aircraft carrier. Budget, schedule, and technical realities set in (complicated by geopolitics), and it was decided the Bush would be that LAST of the Nimitz class, and the new class was renamed CVN-21. The list of new technologies for the Bush has dwindled every year. Here is a brief summary:
http://www.globalsecurity.org/military/systems/ship/cvx.htm .