Performance and Endurance Testing of a Prototype Carbon Dioxide and Humidity Control System for Space Shuttle Extended Mission Capability

A regenerative carbon dioxide (CO₂) and humidity control system which uses a polyethyleneimine sorbent material (designated HS-C) is being developed for potential uses in extended duration Space Shuttle missions. The system design offers a substantial weight saving over the baseline Shuttle lithium hydroxide (LiOH) CO₂ removal system for a mission beyond four men and 7 days. Performance and endurance testing of a flight prototype HS-C system was recently conducted by NASA Johnson Space Center to evaluate its capability and reliability under simulated Shuttle cabin conditions. The testing included 10 days of performance evaluation, 60 days of endurance, at 101,325 N/m² (14.7 psia), and 5 days of performance at a 70,300 N/m² (10.2 psia) cabin pressure.

This paper describes the objectives, approach, System configuration, and test condition matrix/timeline of the testing. The results of the testing are summarized and compared with the performance data obtained in 1978 for the same flight prototype system. Analysis of the testing results shows that the system has experienced 25 to 30 percent degradation in CO₂ removal capacity, but only slight degradation in humidity removal capacity in more than 5 years of sealed storage. The observed dependency of the HS-C system CO₂ and humidity control capacity on the cabin conditions and operating parameters is discussed with computer model predicted performance maps of the system. The findings of the 60-day endurance and 70,300 N/m² (10.2 psia) cabin pressure tests are also reported.