Physical Sensors Instrumentation Research at NASA Glenn

Two Columns

RESEARCH

Novel Thin Film Sensors

Developing Robust Thin Film Sensors with Ceramic, Laminate and Nanostructured Materials

A Multilayered Ceramic Sensor for reading multiple parameters in extereme environments. Credit: NASA GRC

To advance knowledge in fundamental aeronautics and develop technologies for safer, lighter, quieter, and more fuel efficient aircraft, instrumentation technologies are being developed by the National Aeronautics and Space Administration (NASA) in support of its mission to pioneer the future in space exploration, scientific discovery, and aeronautics research. These technologies also enable the capabilities for long duration, more distant human and robotic missions for the Vision for Space Exploration.

The Sensors and Electronics Branch of the NASA Glenn Research Center (GRC) has an in-house effort to develop thin film sensors for surface measurement in propulsion system research. The sensors include those for strain, temperature, heat flux and surface flow, which will enable critical vehicle health monitoring and characterization of components of future space and air vehicles. The need for sensors to operate in harsh environments is illustrated by the need for measurements in the turbine engine hot section. The degradation and damage that develops over time in hot section components can lead to catastrophic failure. At present, the degradation processes that occur in the harsh hot section environment are poorly characterized, which hinders development of more durable components, and since it is so difficult to model turbine blade temperatures, strains, etc, actual measurements are needed.

The use of sensors made of thin films has several advantages over wire or foil sensors. Thin film sensors do not require special machining of the components on which they are mounted, and, with thicknesses less than 10 µm, they are considerably thinner than wire or foils. Spray-on sensors with total thicknesses greater than 10 µm are believed to cause increased turbulence and heating of turbine components, thus causing erroneous measurements. Thin film sensors are much less disturbing to the operating environment, therefore having a minimal impact on the physical characteristics of the supporting components.

The need to consider ceramic sensing elements is brought about by the temperature limits of metal thin film sensors in propulsion system applications. Longer-term stability of thin film sensors made of noble metals has been demonstrated at 1100°C for 25 hrs. The capability for thin film sensors to operate in 1500°C environments for 25 hours or more is considered critical for ceramic turbine engine development. For future space transportation vehicles, temperatures of propulsion system components over 1650°C are expected.

+ Download presentation given at AeroMat 2007, Baltimore, Maryland, June 2007 [4.9 Mb].
+ Download presentation given at Aging Aircraft 2008, Phoenix, Arizona, April 2008 [3.0 Mb].

Advanced Embedded Sensors

Improving Application of Thin Film Sensors onto Complex Structures and Ceramic Components

Thin film strain gauge on an engine valve.

A Thin Film Metal Strain Gauge on an Engine Valve. Credit: NASA

A range of thin film sensor technology has been demonstrated enabling measurement of multiple parameters either individually or in sensor arrays including temperature, strain, heat flux, and flow. Multiple techniques exist for refractory thin film fabrication, fabrication and integration on complex surfaces, and multilayered thin film insulation. The current challenges of instrumentation technology are to further develop systems packaging and component testing of specialized sensors, further develop instrumentation techniques on complex surfaces, improve sensor durability, and to address needs for extreme temperature applications. Technology research and development is ongoing at NASA Glenn Research Center for applications to future launch vehicles, space vehicles, and ground systems.

A particular challenge that is being examined at NASA GRC is the deposition and patterning of thin film sensors on curved and/or complex surfaces. The most straightforward method is to fabricate metal shadow masks with the pattern cut into them, and then wrap them around the component. For complex shapes, such as small turbine blades, castings can be made of the components for fabricating the metal masks for the sensors. Sensors from shadow mask patterns are appropriate for large feature sensors and minimize the component exposure to etching chemicals. Flexible plastic film masks can allow fine-lined sensor patterns to be fabricated using standard lift-off processes, and currently is our standard method of fabricating sensors on complex surfaces. The use of laser trimming equipment is being examined to cut fine-line features on components covered with thin sputtered films, but the focal field of the laser limits the allowed curvature of the components.

+ Download overview given at 52nd IIS, Cleveland, Ohio, May 2006 [3.4 Mb].
+ Download overview given at 55th IIS, League City, Texas, June 2009 [2.3 Mb].

MEMS Radiation Detectors

Miniaturizing Radiation Detector Technology and Examining Revolutionary Concepts

5-minute Exposure of Multibubble Sonoluminescence in Water.

Multibubble Sonoluminescence in Water imaged in a 5-minute exposure. Credit: NASA GRC

New instrumentation and sensing capabilities are required for pursuing NASA’s Vision for Space Exploration. Recently, NASA’s Science Mission Directorate (SMD) outlined specific needs for compact space radiation particle detectors with improved energy range and resolution, angle coverage and resolution, and particle species/charge identification. Miniaturizing and integrating instrumentation is a key aspect to enabling both unmanned and manned space missions due to the limited resources available for power and space for payloads.

Technology limiters are primarily detector size, noise floor and detection geometry. Enabling technology solutions for these limitations are the development of low noise, integrated solid state detectors allowing spherical geometry. NASA Glenn Research Center (GRC) is developing radiation detector technology that allows improved energy range and resolution, angle coverage and resolution, particle species and charge identification for space radiation. These sensors use optical components and wide band-gap semiconductors for small, personal-size sensors for radiation detection.

New, robust compact detectors allow future detector packages more options in satisfying specific mission goals. Multi-aspect radiation detectors will also provide a valuable real-time tool as the cornerstone of an active crew personal dosimetry system, improving astronaut safety and providing better awareness than currently available of the external radiation situation for future lunar explorers.

+ Download presentation from LEAG Conference on Lunar Exploration in Oct. 2005 [4.3 Mb].

Sonoluminescence has risen in the last decade to be a source of interest to those outside of the ultrasonic community in an effort to either understand the effect or to utilize some of its more interesting properties. The phenomena is defined as being the generation of light energy from sound waves, first discovered in the 1930’s as a by-product of early work on sonar. Originally thought to be a form of static electricity, this glow recently was found to be generated in extremely short duration flashes of much less than a billionth of a second by collapsing microscopic bubbles of air. The temperature generated in the collapsing bubbles is at least four times that of the surface of the sun.

Theories for the cause of the glow from a collapsing bubble range from black-body radiation, plasma ionization, quantum vacuum fluctuations, or coherent optical lasing. Even as these theories are being explored, applications for the effect are taking shape, from fusion containment to thin film deposition systems. NASA Glenn Research Center conducted an in-house examination of sonoluminescence for instrumentation and measurement technique development to formulate an application of the effect in its mission to enable safer, lighter, quieter, and more fuel efficient vehicles for aeronautics and space transportation & exploration

+ Download presentation given at JPC2007, Cincinnati, Ohio, July 2007 [6.9 Mb].

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