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The application of Smart Sensor Systems for aerospace applica-tions is a multidisciplinary process consisting of sensor element development, element integration into Smart Sensor hardware, and testing of the resulting sensor systems in application environments. This paper provides a cross-section of these activities for multiple aerospace applications illustrating the technology challenges in-volved. The development and application testing topics discussed are: 1) The broadening of sensitivity and operational range of sili-con carbide (SiC) Schottky gas sensor elements; 2) Integration of fire detection sensor technology into a "Lick and Stick" Smart Sensor hardware platform for Crew Exploration Vehicle applica-tions; 3) Extended testing for zirconia based oxygen sensors in the basic "Lick and Stick" platform for environmental monitoring ap-plications. It is concluded that that both core sensor platform tech-nology and a basic hardware platform can enhance the viability of implementing smart sensor systems in aerospace applications.

Soot formation in laminar ethylene inverse diffusion flames has been investigated experimentally and modeled. Soot volume fraction and temperature measurements have been made and compared to numerical predictions using a soot formation model previously applied to normal diffusion flames. The inverse flame configuration serves as a good test of the applicability of the model and is relevant to practical combustor designs. Comparisons ofthe predictions and data show good agreement. The model reasonably predicts several features of the inverse flame, including flame length. the locations of soot-bearing regions of the flow, and the evolution of the soot volume fraction profile.

Leaks on the space shuttle while on the launch pad have generated interest in hydrogen leak monitoring technology. Microfabricated hydrogen sensors are being fabricated at Case Western Reserve University (CWRU) and tested at NASA Lewis Research Center (LeRC). These sensors have been integrated into hardware and software designed by Aerojet. This complete system allows for multipoint leak monitoring designed to provide leak source and magnitude information in real time. The monitoring system processes data from the hydrogen sensors and presents the operator with a visual indication of the leak location and magnitude. Although the leak monitoring system was designed for hydrogen propulsion systems, the possible applications of this monitoring system are wide ranged. This system is in operation in an automotive application which requires high sensitivity to hydrogen.

Breath analysis techniques offer a potential revolution in health care diagnostics, especially if these techniques can be brought into standard use in the clinic and at home. The advent of microsensors combined with smart sensor system technology enables a new generation of sensor systems with significantly enhanced capabilities and minimal size, weight and power consumption. This paper discusses the microsensor/smart sensor system approach and provides a summary of efforts to migrate this technology into human health breath monitoring applications. First, the basic capability of this approach to measure exhaled breath associated with exercise physiology is demonstrated. Building from this foundation, the development of a system for a portable asthma home health care system is described. A solid-state nitric oxide (NO) sensor for asthma monitoring has been identified, and efforts are underway to miniaturize this NO sensor technology and integrate it into a smart sensor system. It is concluded that base platform microsensor technology combined with smart sensor systems can address the needs of a range of breath monitoring applications and enable new capabilities for healthcare.

As rocket engine components experience wear or failure, anomalous materials may be entrained in the plume. Historically, visible plume anomalies have preceded many rocket engine failures, some of which have been catastrophic. Development of a small, rugged, high-speed, high resolution Fabry-Perot interferometer (FPI) based spectrometer capable of detecting the spectral signatures of eroding engine components during rocket engine test and/or flight operations is described. An operational plume spectrometer fabricated with miniaturized optics has been successfully tested. An extensive test series was conducted to define the limits of the spectrometer with respect to time-response and resolution. The data collected during testing were correlated with measurements obtained using sensitive ground equipment in order to benchmark the spectrometer's performance against a known device. The FPI demonstrated the reliability required for a flight instrument by functioning satisfactorily at or near the rocket engine test stand environment. Several of the optical components are interchangeable, allowing collection of a greater variety of plume signals. Also, the FPI's high resolution capabilities suggest it is suitable for application to both absorption and emission spectroscopy.

Planar light scattering has been used to investigate the turbulent mixing in a multi-element triplet injector at mixture ratio conditions typical of liquid rocket engine gas generators. Experiments were conducted at atmospheric pressure using air seeded with smoke particles to simulate the oxidizer flow and unseeded air to simulate the fuel. Data sets of 200 images (containing 122,000 simultaneous measurements each) of the instantaneous distribution of the scattered light were acquired at several positions throughout the flow. These images have been processed digitally to produce local distributions of the average and rms fluctuation of the mixture fraction. In addition, the spatial autocorrelation of the images has been calculated and analyzed to determine a mean length scale related to the large scale structures in the flow.

Two important improvements in a new technique for measuring and mapping local heat transfer coefficients are described. The first improvement involves the use of a new encapsulated thermochromic liquid crystal which has better stability and a narrower bandwidth than the cholesteric crystals previously used. The second important improvement is in the packaging arrangement. In this new arrangement, useful for gas flows, the liquid crystal is applied directly on the surface of an electrically conducting gold coating used as an electric heater, and is essentially in direct contact with the fluid. The encapsulated liquid crystal used in this study was applied directly to the gold surface without affecting the electrical characteristics of the gold coating. This new packaging arrangement has two advantages. First, no correction for the temperature drop across the plastic substrate is required. Second, a significant increase in the maximum detectable frequency is predicted.