NASA studied this North American Rockwell original concept for a fully reusable space transportation system early in the Shuttle research effort in 1969-1972. This two-stage system featured two fly-back, straight-wing vehicles, a booster and an orbiter, both using liquid propellants stored internally. The large rocketplane would boost the orbiter to a set altitude, where the orbiter would detach and ignite its engines for the ascent into space. The winged booster was powered by multiple rocket engines for ascent plus retractable jet engines for returning and landing like an airplane. The orbiter, sized for two pilots and ten passengers on roundtrip flights to space, also had jet engines for descent to landing. NASA transferred a variety of concept models to the Museum after settling on the final Space Shuttle design.