Space Station Thermal Control During On-Orbit Assembly 881070
The U.S./International Space Station will be assembled incrementally using nineteen flights of the National Space Transportation System (NSTS) Space Shuttle to complete the configuration. This process will produce nineteen different spacecraft configurations, each of which must perform as a fully functional, independent space vehicle. This results in unique design requirements on station distributed systems necessary to allow incremental system buildup while providing some minimum capability early in the assembly sequence. The Thermal Control System (TCS), like electrical power, attitude control, and communications must be present on the initial flight configuration and must grow in capability as assembly continues. This paper summarizes the Space Station program requirements for the TCS, and outlines the capabilities of the TCS for each assembly configuration. The TCS architecture for the completed assembly configuration is described, consisting of an Active TCS (ATCS) and a Passive TCS (PTCS). The four ATCS subsystems are described, including the two-phase ammonia Central ATCS, Photovoltaic Power Module (PVM) ATCS, and Attached Payload Accommodation Equipment (APAE) ATCS, along with the single phase water Internal ATCS. Station external and internal heat loads are summarized as a function of assembly flight configuration and flight mode. The impacts of assembly sequence phasing and growth requirements on the TCS architecture is described. Special emphasis is placed on the results of trade studies performed to date to assess the options for thermal control of the first three station assembly configurations prior to activation of the Central ATCS. Results of these studies relevant to an Early Man-Tended Capability (EMTC) station assembly sequence are summarized.