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Hyperbaric Environmental Control Assembly for the Space Station Freedom Airlock
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English
Abstract
The hyperbaric environmental control assembly (HECA) monitors and controls temperature, humidity, and CO2 levels in the Space Station Freedom airlock when the airlock is used for EVA prebreathing campouts and as a hyperbaric treatment facility. Prebreathing is required prior to extravehicular activity due to the differential between the station nominal pressure and the EVA suit pressure. Hyperbaric treatment is required in the event of decompression sickness.
The HECA consists of an atmosphere recirculation circuit which provides air circulation and temperature control, and a separate CO2 and humidity control circuit. Temperature is controlled by transferring heat from the airlock to the station thermal control system through a compact heat exchanger. CO2 and humidity are removed using a dual-bed, regenerable, molecular sieve system. While one bed is adsorbing, the other bed is being desorbed by venting to space vacuum. Air is circulated by redundant foil-bearing fans in both circuits. The system includes sensors to monitor CO2 and water vapor partial pressures and temperature, and provides an interface to the airlock multiplexer demultiplexer (MDM) microprocessors for control of these parameters within prescribed ranges.
CO2 and latent water production rates have been calculated from established metabolic profiles for both the campout and hyperbaric protocols. An analytical model has been used to predict carbon dioxide and humidity levels as functions of initial crewlock conditions and the specified loads. This model has demonstrated the suitability and robustness of the dual-bed molecular sieve system for the HECA.
Authors
Citation
Rubly, R. and Schimenti, D., "Hyperbaric Environmental Control Assembly for the Space Station Freedom Airlock," SAE Technical Paper 932109, 1993, https://doi.org/10.4271/932109.Also In
References
- Buck C.A. Stolle M.F. “Hyperbaric Treatment Operations Aboard Space Station Freedom,” Paper 921142 22nd ICES 1992
- “EVA for Space Station,” Waligora J. M. NASA Medical Sciences Division Space Hyperbaric Medicine Working Group September 1991
- Requirements of an In-Flight Crew Health Care System (CHeCS) for Space Station JSC 31013, Rev. C.
- Breathing Mask Duty Cycle Effect on Latent Water and CO 2 Loads to HECA During Hyperbaric Treatment–Patient and Observer LMSC EM 2-EVA-AL-062 Julian R. Schimenti D. November 1991
- Latent Water and CO 2 Production Rates Per Person During 10.2-psia Campout Protocol in the Airlock for Space Station EVA LMSC EM 2-EVA-AL-059 Julian R. Schimenti D. June 1991