The NASA Glenn Chemical Species Gas Sensors Team is developing gas sensing technology for aeronautic and space applications. The same technology also has a variety of commercial applications. The sensors presently being developed will allow the detection of hydrogen, hydrocarbons, nitrogen oxides, carbon monoxide, oxygen, and carbon dioxide in a variety of ambient gas conditions and temperatures. The sensors are microfabricated and micromachined using Microelectromechanical Systems (MEMS) based technology to minimize size, weight, and power consumption. Nanomaterials are used to improve the sensor response and stability. A temperature detector and a heater are also included in the structure to allow stable sensor operation at a variety of temperatures. The sensor technology development also depends on the use of nanomaterials and [Silicon carbide (SiC)] as an electronic semiconductor. Mass fabrication of the sensors using silicon-processing technology is envisioned to minimize the cost per sensor.

The program develops three different types of sensor platforms for chemical sensing. One platform is a Schottky diode sensor structure for use in very sensitive measurements. The detection of low concentrations of hydrogen and hydrocarbons can be achieved by using this basic structure. Two other platforms, resistive-based techniques and electrochemical cells, are used depending on the gas and concentration range to be detected. The use of these platforms to produce sensor arrays is an on-going activity of this group. For example, one goal of this gas sensor research is to create a microfabricated gas sensor array operable at high temperatures such as an emissions stream. Since one sensor will not be able to characterize a multiple species in such an environment, an array of high temperature sensors is necessary. This array, effectively a high temperature electronic nose, would be a dramatic step in allowing the monitoring/control of emissions produced by an aeronautic or automotive engine. The signals produced by this nose could be analyzed to determine the constituents of the emission stream. This information could then be used to control those emissions.

The development of the sensors described below involves significant cooperation with the [Electronics Design Center] at Case Western Reserve University (CWRU), whose research goals in chemical sensors often coincide with those of NASA Glenn. The NASA Glenn/CWRU collaboration has been internationally recognized by a 1995 R&D 100 Award for its contribution of an [Automated Hydrogen Leak Detection System]. Other collaborators include [Makel Engineering, Inc.] and [Ohio State University].

AN EXCELLENT EXAMPLE OF DUAL-USE TECHNOLOGY:

The gas sensors being developed by the Chemical Species Gas Sensors team at NASA Glenn were designed with NASA’s primary objective of advancing aeronautic and aerospace technology in mind but can be used in a variety of commercial applications. For example, the hydrogen sensors were originally developed for use on the launch pad of the space shuttle. However, these sensors have been applied to the automotive industry through an interaction with GenCorp Aerojet Corporation. In conjunction with NASA Marshall Space Flight Center, GenCorp previously developed hardware and software to monitor and control the NASA Glenn/CWRU sensors. The system can be customized to fit the user’s needs (e.g. to monitor and display the condition of the tank of a natural gas vehicle). Several of these systems have been purchased for use on the Ford Motor Company assembly line for natural gas vehicles (NGV). It is this complete system that has received the 1995 R&D 100 Award

Makel Engineering, in an STTR is commercializing a next generation hydrogen sensor and oxygen sensor technology for use in space based leak monitoring applications and as well as a variety of commercial applications. Makel Engineering has a second STTR to commercialize the high temperature gas sensors for emission sensing applications. Other applications for the sensors being developed include fuel cell monitoring, combustion process and catalytic reactor monitoring, alarms for high-temperature pressure vessels and piping, polymer production, and volatile organics detection. NASA Glenn, Makel Engineering, Inc., Case Western Reserve University, and NASA Kennedy recently received a Turning Goals into Reality Award for developing and application of Smart Leak Sensor Technology in applications, as varied as the NASA Helics Vehicle, the X43, and the Ford U car.

IN SUMMARY:

The NASA Glenn Chemical Species Gas Sensors Team is actively involved in developing chemical species gas sensor technology for a variety of aeronautic and aerospace applications which can be used in commercial applications. The sensors being developed include hydrogen, hydrocarbon, nitrogen oxides, carbon monoxide, oxygen, and carbon dioxide sensors. These sensors are used in a variety of sensor arrays for leak, fire, and emission sensor applications. A number of commercial applications exist and the combination of these sensors with actuators and miniature power supplies, for example, is envisioned. For more information, feel free to contact any member of the NASA Glenn Chemical Species Sensors Team.