NASA studied this North American Rockwell concept for a two-stage, fully reusable space transportation system during the Shuttle research effort in 1969-1972. It featured two piloted fly-back vehicles--a large booster and a smaller orbiter, both with delta wings and pop-up jet engines for powered return to landing. The booster would lift the orbiter to a set altitude, then separate and depart as the orbiter ignited its engines to continue ascent into space. All liquid propellants were carried inside each vehicle. NASA transferred a variety of concept models to the Museum after settling on the final Space Shuttle design.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.