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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.

This paper presents two quite different solid amine carbon dioxide removal systems that have progressed to manned chamber testing status. The first is a carbon dioxide concentrator that was tested as part of a NASA sponsored 90 Day Manned Test in 1970. It provided a 99+% carbon dioxide stream for further processing. The second system is the Regenerable Carbon Dioxide Removal System (RCRS) currently flying on the extended mission duration version of the Shuttle Orbiter. This system uses an amine that is tailored for overboard venting. It was chamber tested as part of its Certification process. Both chamber test series are discussed and performance data presented.

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.

A regenerable carbon dioxide (CO2) removal system has demonstrated its capability for Extended Duration Orbiter (EDO) missions during Shuttle Columbia flights STS-50, STS-52 and STS-55. The EDO requirements of missions up to 18 days and the capability for future missions up to 30 days necessitated the development and implementation of the regenerable CO2 removal system. The designed system offers a substantial weight and stowage volume reduction for missions beyond eight (8) days as compared to the baseline, nonregenerable, Lithium Hydroxide (LiOH) CO2 removal unit. 1 The system, referred to as the Regenerable CO2 Removal System (RCRS) was designed and developed by Hamilton Standard Division of United Technologies Corporation under contract to Rockwell International and NASA-Johnson Space Center. This paper presents an overview of the design characteristics and system performance.

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.

A new carbon dioxide scrubber system is undergoing development for extended duration orbiter (EDO) missions. The EDO requirements of missions up to 18 days and the capability for future missions up to 30 days necessitated the development and implementation of a regenerative CO2 removal process. This new system will reduce the launch weight and stowage volume as compared to the present method of CO2 removal, lithium hydroxide, which is stowed in canisters. The selected design, called the Regenerable CO2 Removal System (RCRS), uses a solid amine material to adsorb carbon dioxide and water vapor and periodically desorb these to space vacuum. The RCRS, which is located below the middeck floor, interfaces with the orbiter's cabin Atmospheric Revitalization System (ARS) and is adjustable from four to seven crewmembers. The RCRS is designed to automatically cycle the beds from adsorb to vacuum-desorb every 30 minutes.