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The Space Shuttle Orbiter Pressure Control System uses an electrochemical oxygen partial pressure (PPO2) sensor with an amplifier to provide continuous monitoring and control signals to maintain oxygen concentrations in a two gas cabin atmosphere. Due to manufacturing complications, the need for a replacement sensor was identified. A program was initiated by NASA/Johnson Space Center (JSC) to develop a longer life sensor which would satisfy all of the existing interface requirements without modifications to the remainder of the system. As a result, a low cost, high accuracy, replacement sensor has been developed and is planned for use on future Shuttle Orbiter missions. In addition to the oxygen sensor, a redesign of the amplifier assembly has been proposed which will provide higher accuracy and greater output signal gain adjustment. The increase in gain adjustment will provide increased sensor utilization time.

The Atmospheric Revitalization Pressure Control Subsystem (ARPCS) provides oxygen partial pressure and total pressure control for the habitable atmosphere of the Shuttle for either a one atmosphere environment or an emergency 8 PSIA mode. It consists of a Supply Panel, Control Panel, Cabin Pressure Relief Valves and Electronic Controllers. The panels control and monitor the oxygen and nitrogen supplies. The cabin pressure relief valves protect the habitable environment from overpressurization. Electronic controllers provide proper mixing of the two gases. This paper describes the ARPCS, addresses the changes in hardware that have occurred since the inception of the program; the performance of this subsystem during STS-1 and STS-2; and discusses future operation modes.