>>63974488
>Do you know if any of those went beyond wind tunnel/RCS mock-ups?
These programs are direct predecessors to NGAD. Boeing made a demonstrator that flew in 96, see picrel. X-36 was a pair of subscale prototypes that flew in 97. X-45 and X-47 were both derived from this research.
>and possibly into production
Still a few years out from that, don't get ahead of yourself.