The unpiloted Russian Progress 7 supply ship departs from the Zvezda Service Module's docking port on the International Space Station. Carrying its load of trash and urneeded equipment, it will be deorbited and burned up in the atmosphere. The undocking paves the way for the arrival of the new Progress 8, filled with fresh supplies. Soviet designers realized that long-duration missions in space would demand a constant supply of consumable materials from Earth. The cost-effective Progress spacecraft made possible an almost permanent presence in space and stands out as a single biggest contribution to this achievement. Propulsion and service systems were installed in the tail section of the vehicle and the cargo ship was inseparable during its entire flight. Upon conclusion of its supply mission to the Station, it would be directed into the atmosphere to burn up.