Skylab

This August 1971 interior photograph of Skylab's Multiple Docking Adapter (MDA) flight article, undergoing outfitting at the Martin-Marietta Corporation's Space Center facility in Denver, Colorado, shows the forward cone area and docking tunnel (center) that attached to the Apollo Command Module. Designed and manufactured by the Marshall Space Flight Center, the MDA housed the control units for the Apollo Telescope Mount, Earth Resources Experiment Package, and Zero-Gravity Materials Processing Facility and provided a docking port for the Apollo Command Module.