Abstract: A spacecraft system that includes a primary space vehicle and a secondary space vehicle, both of which are designed to optimize payload capacity and launch weight of the primary space vehicle. The primary and secondary space vehicles combine to form an on-orbit space vehicle capable of performing functions and maneuvers that exceed the physical capabilities of the primary space vehicle at the time of its launch. The spacecraft system is designed to minimize propellant containment-related disturbances while maintaining a standard level of functionality. The primary space vehicle is designed to be incapable of independently performing a propellant-intensive orbit change maneuver. Instead the primary space vehicle is designed to couple to a secondary space vehicle having propellant and thrust capability sufficient to perform an orbit change maneuver when the primary and secondary space vehicles are coupled.