1.0 ABSTRACTThe Space Station Freedom (SSF) airlock Depressurization/Repressurization (D/R) subsystem designed by McDonnell Douglas Aerospace Space Station Division is used to depressurize the airlock to allow egress from SSF by two pressure suited crewmembers to perform extravehicular activity (EVA), and to repressurize the airlock at the conclusion of EVA. The D/R subsystem utilizes vacuum, or D/R Equalization (D/RE), lines to accomplish the functions of venting airlock gas to space during depressurization and equalizing pressures between airlock and SSF chambers during repressurization. Categories of D/RE line requirements include performance; safety, reliability, and maintainability; and control and operations. For the development of the SSF airlock, McDonnell Douglas Aerospace has performed analysis and developed design solutions that meet these requirements while optimizing performance and cost. This paper will describe results of this analysis, including system performance data.