Docking Module, ASTP Backup

In 1971, the US and the USSR agreed to carry out a docking in orbit of the Apollo and Soyuz spacecraft. This project was called the Apollo-Soyuz Test Project (ASTP). An airlock was needed to transition from the American cabin pressure system of 5 pounds per square inch pure oxygen to the Soviet mixed oxygen/nitrogen system at normal atmospheric pressure (about 14.7 psi). NASA contracted with North American Rockwell, the CSM contractor, to build the Docking Module (DM). On the front was mounted the three-leaf androgynous docking system, which was jointly designed by US and Soviet engineers. It could be used in either a passive (retracted) or active (extended) docking configuration. The DM launched with the Apollo on July 15, 1975 and was used in the historic docking with Soyuz 19 two days later. After undocking on July 19, the American crew of Stafford, Brand and Slayton performed scientific experiments in the DM.

The Smithsonian's DM is the backup to the flight DM. It was transferred from NASA to the Smithsonian in 1980.