SPACEPLANE SHELVED? For 16 years, Aviation Week & Space Technology has investigated myriad sightings of a two-stage-to-orbit system that could place a small military spaceplane in orbit. Considerable evidence supports the existence of such a highly classified system, and top Pentagon officials have hinted that it's "out there," but iron-clad confirmation that meets AW&ST standards has remained elusive. Now facing the possibility that this innovative "Blackstar" system may have been shelved, we elected to share what we've learned about it with our readers, rather than let an intriguing technological breakthrough vanish into "black world" history, known to only a few...