Chemical Sensor Testing for Space Life Support Chemical Processing: Part I. Moisture Sensors 941263
In support of the National Aeronautics and Space Administration(NASA), a laboratory has been established at the Jet Propulsion Laboratory (JPL) to evaluate the characteristics of chemical sensors which are candidates for use in a controlled chemical processing life support system. Such a facility is required for characterizing those sensors under development as well as those commercially available but whose functional properties are typically based upon operating in industrial environments that will not be completely synonomous with space operations. Space environments, such as an orbiting station or lunar base, will generally have different sensor requirements than terrestrial applications with respect to size, multifunctionality, sensitivity, reliability, temperature, ruggedness, mass, consumables, life, and power requirements.
Both commercially available and developmental moisture sensors have been evaluated. These sensors have been evaluated under conditions which simulate the process stream environment of a four bed, molecular sieve, carbon dioxide removal operation. Selected sensors were also tested in an environment simulating an Advanced Carbon Formation System. Sensor technologies include electrochemical(both conductometric and capacitive) and surface acoustic wave (SAW) types. Parameters of interest over repeated cyclic life testing included particular conditions of flowrate and temperature. A computer-controlled data acquisition and control system allows programmable and repeatable cycles operating over the specific moisture-time profile measured from air processing operations. Test results are presented for various commercially available moisture sensors.