NASA studied this Martin Marietta concept for a fully reusable space transportation system during the Shuttle research effort in 1969-1972. It featured two piloted fly-back vehicles - a twin-fuselage booster craft and a delta-wing orbiter - in a two-stage configuration. The liquid-propellant booster would carry the orbiter to a set altitude, then detach and be piloted back to land. After separation the orbiter would ignite its own engines to reach orbit. Both vehicles had retractable air-breathing jet engines for powered airplane-like flight during descent to landing. NASA transferred a variety of concept models to the Museum after settling on the final Space Shuttle design.
This object is on display in James S. McDonnell Space Hangar at the Steven F. Udvar-Hazy Center in Chantilly, VA.