NASA studied this Grumman/Boeing concept for a partially reusable space transportation system during the Shuttle research effort in 1969-1972. This two-stage system featured two piloted fly-back vehicles, a booster and an orbiter, both using liquid propellant. The orbiter was mounted on a large external tank above the booster. Powered by five F-1 engines, the booster would carry the orbiter to a set altitude, then detach to return to base. After separation, the orbiter's engines, fed from the tank, would ignite for final ascent into orbit. Moving all the orbiter's propellants into a disposable external tank made the orbiter smaller and lighter-weight. 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.