NGB demonstrator may be a twin-engine aircraft resembling an X-47B. Initial version will be piloted, but an unmanned endurance version is a probable follow-on.
It is likely that the prototype will build on technology under development for the Navy's X-47B Unmanned Combat Air System Demonstrator (UCAS-D), putting within reach USAF's goal of a 2018 initial operational capability date for the bomber.
http://www.aviationweek.com/aw/gener...ltra%20Stealth