Early Program Development. NASA public domain image colelction.

In this 1986 artist's concept, the Orbital Maneuvering Vehicle (OMV), undergoes changeout of the Propulsion Module outside the Space Shuttle Cargo Bay. As envisioned by Marshall Space Flight Center plarners, the OMV would be a remotely-controlled free-flying space tug which would place, rendezvous, dock, and retrieve orbital payloads.