NASA studied this Grumman concept for a partially reusable space transportation system during the Shuttle research effort in 1969-1972. This two-stage system featured a reusable orbiter and disposable external fuel tank attached to a recoverable booster similar to the Saturn V launch vehicle used to send astronauts to the Moon. After the booster burned out and was jettisoned, the orbiter's engines, fed from the attached disposable tank, would ignite for final ascent into orbit. The booster would land in the ocean and be retrieved; the orbiter would return from space to a runway landing. This concept sought to reduce cost by making use of proven, existing booster technology rather than developing a new launch vehicle for the orbiter. NASA transferred a variety of concept models to the Museum after settling on the final Space Shuttle design.