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Future human space exploration missions present significant challenges for life support system (LSS) development. These life support systems will require incorporation of regenerative technologies to reduce or eliminate expendables and be low risk, demonstrating high reliability and long-term performance capability. A regenerative LSS for Space Station is a key step toward meeting these future space exploration requirements. In the development of the Space Station regenerative LSS, the challenges have been both technical and budgetary. Currently, the International Space Station Alpha (ISSA) program will consist of three Phases. Phase I will be MIR/Shuttle Orbiter flights with United States (US) crews attending to the various US flight experiments on-board the MIR. Phase II will consist mostly of Russian launched modules and the United States (US) Laboratory module. Phase III will launch the US Habitat module to implement US regenerative LSS.

The Flash Evaporator System (FES) is part of the Shuttle Orbiter Active Thermal Control Subsystem. The FES provides total heat rejection for the vehicle Freon Coolant Loops during ascent and entry and supplementary heat rejection during orbital mission phases. This paper reviews the performance of the FES during the first two Shuttle orbital missions (STS-1 and STS-2). A comparison of actual mission performance against design requirements is presented. Mission profiles (including Freon inlet temperature and feedwater pressure transients), control temperature, and heat load variations are evaluated. Anomalies that occurred during STS-2 are discussed along with the procedures conducted, both in-flight and post-flight, to isolate the causes. Finally, the causes of the anomalies and resulting corrective action taken for STS-3 and subsequent flights are presented.

Both Centralized and Distributed approaches are being evaluated for the installation of Environmental Control and Life Support (ECLS) equipment in the Space Station. In the Centralized facility concept, integrated processing equipment is located in two modules with plumbing used to circulate ECLS services throughout the Station. The Distributed approach locates the ECLS subsystems in every module of the Space Station with each subsystem designed to meet its own module needs. This paper defines the two approaches and how the advantages and disadvantages of each are tied to the choice of Space Station architecture. Other considerations and evaluations include: crew movement, Station evolution and the ducting impact needed to circulate ECLS services from centrally located processing equipment.