In 1971, the US and the USSR agreed to carry out a docking in orbit of an Apollo CSM and a 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). Moreover, a common docking system was a necessity. NASA contracted with North American Rockwell, the CSM contractor, to build the Docking Module quickly. On the front was mounted the three-leaf androgynous docking system, which was jointly designed by US and USSR engineers. It could be used in either a passive (retracted) or active (extended) docking configuration. The DM was launched with the Apollo on July 15, 1975 and 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, which was finally discarded on July 23. This mockup DM was part of a complex of equipment installed at the NASA Johnson Space Center in Houston in 1973 for the training of the American and Soviet crews.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.