The Space Station Freedom (SSF) configuration evolved during the past decade in response to changing requirements and resources. Early space station studies determined that an on-orbit U.S. Laboratory (Lab) module was required to accomplish mission goals. A Habitation (Hab) module was needed to support the objective of a permanently manned presence on the station. Operational requirements were met by providing resource nodes, pressurized logistics (Log) elements, and airlocks. These five elements are the basic pressurized building blocks used to construct SSF.
As the SSF design matured, requirement changes were made to accommodate such considerations as launch capability, extravehicular activity (EVA) assembly time, intravehicular activity (IVA) outfitting and checkout, and other program resource constraints. These considerations resulted in design changes that were incorporated into a restructured design that will be finalized and become the SSF baseline by mid-1991.
The baselined restructured program is planned to be conducted in three phases: (1) a man-tended capability (MTC) phase that provides a U.S. Lab element and node to enable early support of scientific experimentation; (2) a permanently manned capability (PMC) phase with a Hab and an additional node to support four crew members on orbit for 90 days; and (3) the eight-man crew capability (EMCC) phase, which will be implemented when funds become
available. The European and Japanese laboratory elements will be installed at PMC.
This paper presents a design overview for each of the three restructured program phases with respect to the U.S. Lab, Hab, and pressurized logistics element topologies. An outline of the capabilities for the primary subsystems is also included. The described configuration summarizes all changes that are approved and incorporated in Restructure through April 1991.