2016 NASA Glenn Technology Day Panel Presentation on May 24, 2016. The panel description is: Environmental Impact: NASA Glenn Water Capabilities Both global water scarcity and water treatment concerns are two of the most predominant environmental issues of our time. Glenn researchers share insights on a snow sensing technique, hyper spectral imaging of Lake Erie algal blooms, and a discussion on non-equilibrium plasma applications for water purification supporting human spaceflight and terrestrial point-of-use. The panel moderator will be Bryan Stubbs, Executive Director of the Cleveland Water Alliance.

A High Temperature Fiber Optic Sensor (HTFOS) has been developed at NASA Glenn Research Center for aircraft engine applications. After fabrication and preliminary in-house performance evaluation, the HTFOS was tested in an engine environment at NASA Armstrong Flight Research Center. The engine tests enabled the performance of the HTFOS in real engine environments to be evaluated along with the ability of the sensor to respond to changes in the engine's operating condition. Data were collected prior, during, and after each test in order to observe the change in temperature from ambient to each of the various test point levels. An adequate amount of data was collected and analyzed to satisfy the research team that HTFOS operates properly while the engine was running. Temperature measurements made by HTFOS while the engine was running agreed with those anticipated.

An underwater dielectric barrier discharge (DBD) plasma jet excited by a repetitively pulsed nanosecond pulsed power modulator was used to study plasma-induced decolorization of a 1.4 × 10 -4 M solution of methylene blue (MB). Past plasma decolorization studies have focused on spectrophotometry as the main diagnostic to assess decomposition. Because spectrophotometry is a measure of changes in the structure of molecular color, it is not an absolute measure of decomposition. In this paper, high-pressure liquid chromatography is used in parallel with spectrophotometry for comparison purposes and to assess the degree of true decomposition. Spectrophotometry results were found to be in agreement with chromatography measurements, suggesting that, at least in the case of MB, spectrophotometry is an adequate measure of decomposition. Additionally, the utility of a dual plasma jet applicator for rapid contaminant decomposition was explored.

This paper reviews the effects of varying gravitational levels on functional Near-Infrared Spectroscopy (fNIRS) headgear. The fNIRS systems quantify neural activations in the cortex by measuring hemoglobin concentration changes via optical intensity. Such activation measurement allows for the detection of cognitive state, which can be important for emotional stability, human performance and vigilance optimization, and the detection of hazardous operator state. The technique depends on coupling between the fNIRS probe and users skin. Such coupling may be highly susceptible to motion if probe-containing headgear designs are not adequately tested. The lack of reliable and self-applicable headgear robust to the influence of motion artifact currently inhibits its operational use in aerospace environments. Both NASAs Aviation Safety and Human Research Programs are interested in this technology as a method of monitoring cognitive state of pilots and crew.

The paper reviews potential applications of functional Near-Infrared Spectroscopy (fNIRS), a well-known medical diagnostic technique, to monitoring the cognitive state of pilots with a focus on identifying ways to adopt this technique to airborne environments. We also discuss various fNIRS techniques and the direction of technology maturation of associated hardware in view of their potential for miniaturization, maximization of data collection capabilities, and user friendliness.

Fiber Bragg gratings (FBGs) embedded in conventional fibers may serve as temperature sensors over a wide temperature range and withstand temperatures around 1200 K. A variety of linearly polarized (LP) modes for the wavelengths between 400 and 700 nm may be sustained in fibers with and without FBGs. The composition of the LP modes and their competition is instrumental for understanding physics of thermo-optics and thermal expansion effects in silica-based fibers. The first objective of this work was to model mathematically the competition between LP modes and modal distribution using the solutions of Bessel equations for the fibers with and without the gratings. Computer generated modes were constructed and the cut-off V-numbers (and Eigen values W and U) were determined. Theoretical results then were compared with experimental observations of LP modes for two separate ranges of temperatures: 77-300 K and 300-1200 K. To study the formation of LP modes over the first temperature range, liquid nitrogen was used to cool down the fiber and a thermocouple was used to monitor the temperature of the fiber. Real time recording of the modal structure was performed using digital imaging and data acquisition instrumentation. To study LP modes between 300-1200 K, the fibers were inserted into a tube furnace with temperature control. The wavelength of the infrared radiation was reflected by a FBG and detected by an optical spectrum analyzer. Radiation at the visible wavelength propagated through the fibers, and transmitted visible light was collected, analyzed and recorded with a CCD camera to monitor distribution of the LP modes in the samples with and without the FBGs.

A 15- by 15-cm supersonic wind tunnel application of a one-dimensional laser beam scanning approach to shock sensing is presented. The measurement system design allowed easy switching between a focused beam and a laser sheet mode for comparison purposes. The scanning results were compared to images from the tunnel Schlieren imaging system. The tests revealed detectable changes in the laser beam in the presence of shocks. The results lend support to the use of the one-dimensional scanning beam approach for detecting and locating shocks in a flow, but some issues must be addressed in regards to noise and other limitations of the system.

Plasma production or plasma injection in liquid water affords one the opportunity to nonthermally inject advanced oxidation processes into water for the purpose of purification or chemical processing. Such technology could potentially revolutionize the treatment of drinking water, as well as current methods of chemical processing through the elimination of physical catalysts. Presented here is an overview of current water treatment technology, its limitations, and the future, which may feature plasma-based advanced oxidation techniques. As such, this field represents an emerging and active area of research. The role that plasma-driven water chemistry can play in addressing emerging threats to the water supply is discussed using case study examples. Limitations of conventional plasma injection approaches include limited throughput capacity, electrode erosion, and reduced process volume. At the University of Michigan, we are investigating two potential approaches designed to circumvent such issues. These include direct plasma injection using an underwater DBD plasma jet and the direct production of plasmas in isolated underwater bubbles via a pulsed electric field. These approaches are presented here, along with the results.

Direct experimental measurements of the thermo-optic for fixed temperature intervals (20-200 degrees C, 200-500 degrees C C, 500-660 degrees C, 660-780 degrees C) in fused silica fiber containing fiber Bragg gratings (FBGs) were conducted. The diffraction efficiency of a FBG fluctuated with temperature between 2.01 x 10(-4) and 0.17 x 10(-4) while the temperature shift of the Bragg's peak was monitored between 1300 and 1311 nm with sub-Angstrom precision. Numerical simulations were focused on FBG's diffraction efficiency calculations accounting for the temperature drift of the gratings, and found to be in excellent agreement with obtained experimental data.It was found that the first-order thermo-optic coefficient changes between 1.29 and 1.85 x 10(-5) K-1 for the linear fit and at T=0 degrees C its value was found to be close to 2.37 x 10(-5) K-1 for the polynomial fit of experimental data. The average thermo-optic coefficient undergoes a minimum in the vicinity of 440 degrees C. Additional observation indicates a negative sign of the second-order thermo-optic coefficient. The value of thermal expansion coefficient was much less (0.5 x 10(-6) K-1) than that for the average thermo-optic coefficient. Based on the energy dispersive spectroscopy it was determined that thermal erasing of the FBGs at a temperature around 780 degrees C corresponds to germanium monoxide diffusion out of core in silica-based fibers. (C) 2011 Elsevier B.V. All rights reserved.

In this paper techniques used to manufacture thermally stable fiber Bragg gratings capable to operate at extreme temperatures for long durations of time are analyzed. Results on packaging and long durability tests performed on sensor units comprised of chemical composition grating or CCG-type fiber Bragg gratings are also reported. The tests included exposure of the packaged sensors to 1000 °C thermal environments for up to 1000 hours and thermal cycling at rates up to 400 °C/min.

Develop Advanced Sensor Technology and rotordynamic structural diagnostics to address existing Aviation Safety Propulsion Health Management needs as well as proactively begin to address anticipated safety issues for new technologies.

Measurement tools for high speed air flow are sought both in industry and academia. Particular interest is shown in air flows that exhibit aerodynamic shocks. Shocks are accompanied by sudden changes in density, pressure, and temperature. Optical detection and characterization of such shocks can be difficult because the medium is normally transparent air. A variety of techniques to analyze these flows are available, but they often require large windows and optical components as in the case of Schlieren measurements and/or large operating powers which precludes their use for in-flight monitoring and applications. The one-dimensional scanning approach in this work is a compact low power technique that can be used to non-intrusively detect shocks. The shock is detected by analyzing the optical pattern generated by a small diameter laser beam as it passes through the shock. The optical properties of a shock result in diffraction and spreading of the beam as well as interference fringes. To investigate the feasibility of this technique a shock is simulated by a 426 m diameter optical fiber. Analysis of results revealed a direct correlation between the optical fiber or shock location and the beam s diffraction pattern. A plot of the width of the diffraction pattern vs. optical fiber location reveals that the width of the diffraction pattern was maximized when the laser beam is directed at the center of the optical fiber. This work indicates that the one-dimensional scanning approach may be able to determine the location of an actual shock. Near and far field effects associated with a small diameter laser beam striking an optical fiber used as a simulated shock are investigated allowing a proper one-dimensional scanning beam technique.

The paper describes phenomena observed as a result of laser pencil beam interactions with abrupt interfaces including aerodynamic shocks. Based on these phenomena, a novel flow visualization technique based on a laser scanning pencil beam is introduced. The technique reveals properties of light interaction with interfaces including aerodynamic shocks that are not seen using conventional visualization. Various configurations of scanning beam devices including those with no moving parts, as well as results of proof-of-concept tests, are included.

New light-driven actuators based on films of polymer polyvinylidene fluoride are described. The actuators employ the photomechanical bending of the polymer film caused by low power (10mW and less) laser radiation. The photomechanical effect combines various physical mechanisms, such as anisotropic thermal expansion, converse piezoelectric mechanism along with photovoltaic and pyroelectric ones, while the mechanism of thermal expansion is dominant for slow motion. Mechanical vibrations of the strips of the photomechanical polymer were observed with periodic pulsed laser excitation. The resonance frequency is inversely proportional to the square of the length of the strip, in full agreement with the theory. Resonance frequency measurements were used to determine the modulus of elasticity of the films, which was close to 3.0x10 9 Pa. Two possible applications were discussed: photonic switch and adaptive mirror. The proposed actuators have a potential of being used as the components of future light-driven micro/nano systems.

We describe new light-driven actuators based on films of polymer polyvinylidene fluoride, known as PVDF. The actuators employ the photomechanic bending of the polymer film caused by low-power (10 mW and less) laser radiation. The photomechanic effect combines various physical mechanisms, such as thermal expansion, the converse piezoelectric mechanism, and the photovoltaic and pyroelectric mechanisms, while the mechanism of thermal expansion is dominant. The force applied by the actuators to external objects is measured with a torsion balance. It is proportional to the power of laser beam and could be as high as 10(-4) N for a 50-mu m film illuminated with a 10-mW laser beam. We demonstrate mechanical vibrations of a 1 x 7-mm strip actuator at a frequency of 0.3 kHz. As examples of possible applications, a photonic switch and an actuator with a closed-loop motion that could drive the inner workings of a conventional mechanical clock were demonstrated. The proposed actuators have a potential of being used as propulsion components of future light-driven micro/nano systems. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

The development of a sensitive oxygen sensor suitable for deployment in the ullage of an aircraft fuel tank is discussed here. Instead of using plain optical fibers, a long period grating is utilized for achieving a light weight optical sensor that strongly couples the core guided light into the cladding and vice versa. The detection principle is based on the quenching of the luminescence of a ruthenium complex, which is incorporated to the optical fiber using sol-gel techniques. Data are shown on sensitivity enhancement, and performance of the sensor splashed with jet fuel.