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Technical Paper

Shuttle Orbiter Environmental Control and Life Support System-Flight Experience

The Orbiter Environmental Control and Life Support System (ECLSS) functioned successfully on 76 Shuttle missions to date. The ECLSS consists of six subsystems which provide both a habitable environment for the crew and active vehicle thermal control. The Orbiter ECLSS design is reviewed in this paper and the operational flight experience is summarized. Significant flight problems are described, along with the design or procedural changes implemented to resolve the problems. The design and flight experience is summarized for recent enhancements to the ECLSS to meet extended duration missions and to accommodate visits to the Mir Space Station and to the International Space Station.
Technical Paper

Development, Performance and Flight Test Results of the Cabin Air Cleaner (CAC) for the Shuttle Orbiter

Debris and particulate filtration problems have been persistent during flights on the Space Shuttle Orbiter since STS-6. Analysis of the Orbiter Environmental and Life Support System (ECLSS) indicated that both the volumetric flows and velocities were essentially designed for ventilation, heat removal, and gas blending with minimal consideration for debris removal. The baseline Orbiter filtration system consisted of a single 300 micron filter at the inlet of the cabin fan primarily to protect the cabin fan hardware. This filter was increased to 70 microns and additional filters added after some hardware failures occurred. However, these changes did not clean the environment as expected. An evaluation of the size and type of debris in the cabin air determined that the debris is able to “short-circuit” the cabin filtration system and remains in the cabin air causing the crew discomfort.
Technical Paper

Design of a Shuttle Air and Water Prefilter for Reduced Gravity Operation

The Space Shuttle humidity separator prefilter was developed to remove debris from the air/water stream that flows from the cabin condensing heat exchanger to the humidity separator. Debris in this flow stream has caused humidity separator pitot tube clogging and subsequent water carryover on several Shuttle flights. The first design concept of the prefilter was flown on STS-40 in June, 1991. The prefilter was installed on-orbit. Video footage of its operation revealed that the prefilter did not pass water at a constant rate, resulting in a tendency to slug the humidity separator. The results from this flight test have resulted in a complete redesign of the prefilter. In this paper the first prefilter design is described, the flight results from STS-40 are examined, and the on-orbit performance of the prefilter is explained. The redesigned prefilter is described with emphasis on the features that should allow successful reduced gravity operation.