The Orion Air Monitor (OAM), a derivative of the International Space Station's Major Constituent Analyzer (MCA) (1–3) and the Skylab Mass Spectrometer (4, 5), is a mass spectrometer-based system designed to monitor nitrogen, oxygen, carbon dioxide, and water vapor. In the Crew Exploration Vehicle, the instrument will serve two primary functions: 1) provide Environmental Control and Life Support System (ECLSS) data to control nitrogen and oxygen pressure, and 2) provide feedback the ECLSS water vapor and CO2 removal system for swing-bed control. The control bands for these ECLSS systems affect consumables use, and therefore launch mass, putting a premium on a highly accurate, fast-response, analyzer subsystem.
This paper describes a dynamic analytical model for the OAM, relating the findings of that model to design features required for accuracies and response times important to the CEV application. The application of the model to the optimization of water response time is discussed, with data showing that the CEV's requirements are met at inlet temperatures above 90°C.