Salyut 6 represented the major step forward in space station operations that the Soviets had been planning for some time. Launched on 29 September 1977, it featured a second docking port, as well as an Extravehicular Activity (EVA) hatch. The second docking port was a significant addition because it allowed the station to be resupplied by Progress cargo spacecraft, an essential capability for long-term habitation. It would also allow for the possibility of visiting crews who would dock with the station, stay for about a week, and then return in the older Soyuz leaving the new one for the long-duration crew.