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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Effect of Inductive Coil Geometry on the Operating Characteristics of an Inductive Pulsed Plasma Thruster

Operational characteristics of two separate inductive thrusters with conical theta pinch coils of different cone angles are explored through thrust stand measurements and time- integrated, unfiltered photography. Trends in impulse bit measurements indicate that, in the present experimental configuration, the thruster with the inductive coil possessing a smaller cone angle produced larger values of thrust, in apparent contradiction to results of a previous thruster acceleration model. Areas of greater light intensity in photographs of thruster operation are assumed to qualitatively represent locations of increased current density. Light intensity is generally greater in images of the thruster with the smaller cone angle when compared to those of the thruster with the larger half cone angle for the same operating conditions. The intensity generally decreases in both thrusters for decreasing mass flow rate and capacitor voltage. The location of brightest light intensity shifts upstream for decreasing mass flow rate of propellant and downstream for decreasing applied voltage. Recognizing that there typically exists an optimum ratio of applied electric field to gas pressure with respect to breakdown efficiency, this result may indicate that the optimum ratio was not achieved uniformly over the coil face, leading to non-uniform and incomplete current sheet formation in violation of the model assumption of immediate formation where all the injected propellant is contained in a magnetically-impermeable current sheet.

Hallock, Ashley K.↗
NASA NTRS1994

Ground and space flight experiments of the effects of light, sound and/or temperature on animals

Papers on the following topics are presented: (1) rat long term habitability and breeding under low light intensity (5 lux); (2) effects of low light intensity on the rat circadian system; (3) effects of sound/noise on the circadian system of rats; (4) temperature related problems involving the animal enclosure modules (AEM) lighting system; and (5) NASA AEM filter test 92/93 (Rats).

Holley, Daniel C.↗
DOE OSTI2025

Redox Couples Control Band Bending, Photovoltage, and Quasi-Fermi Levels in Tungsten Oxide (WO 3 ) Photoanodes

Tungsten oxide (WO 3 ) is a well-known photoanode and photocatalyst for photoelectrochemical (PEC) water oxidation. Because the compound has a deep valence band, it can facilitate the oxygen evolution reaction without added cocatalysts, and it can drive the oxidation of species with much higher electrochemical potentials, including the conversion of water to hydrogen peroxide, sulfate to persulfate, and iodate to meta-periodate. Here, we use the liquid vibrating Kelvin probe surface photovoltage (liquid VK-SPV) technique in combination with open circuit potential (OCP) and photoelectrochemical (PEC) scans to assess the possibility of reaching such oxidizing potentials in aqueous electrolytes and at open circuit. Here, this is done by mapping the quasi-Fermi levels of electrons and holes at the interfaces as a function of the light intensity. Nanostructured WO 3 photoelectrodes for this purpose were fabricated by thermal annealing of a tungstic acid solution on fluorine-doped tin oxide. Electrochemical measurements are conducted at open circuit and 400 nm LED light illumination in electrolytes containing fast (O 2 /H 2 O 2 ), slow (O 2 /H 2 O), and very oxidizing (NaIO 4 /NaIO 3 ) redox couples. Photovoltage values scale with the light intensity and with the built-in potential for each redox couple and reach values up to 0.61 V under 20 mW cm –2 illumination for the NaIO 4 electrolyte. This shows that the photoelectrodes behave like Schottky-type diodes whose maximum possible energy output is determined mainly by the built-in voltage of each junction. For slow redox couples, the quasi-Fermi level of the holes increases with light intensity due to hole accumulation at the WO 3 –liquid interface. For example, for the O 2 /H 2 O electrolyte, interfacial hole accumulation and removal occur on the 90–300 s time scale. For the fast hole acceptor H 2 O 2 , on the other hand, the quasi-Fermi level of the photoholes is pinned to the electrochemical potential of the O 2 /H 2 O 2 couple. This limits the energy conversion efficiency of the electrode. Overall, these results reveal the influence of charge transfer thermodynamics and kinetics on the photovoltage of WO 3 . Furthermore, the work further establishes VK-SPV as a contactless method to observe the photovoltage, carrier dynamics, and quasi-Fermi levels of semiconductor-liquid junctions.

Electrodes↗
NASA NTRS1972

High intensity portable fluorescent light

Eight high intensity portable fluorescent lights were produced. Three prototype lights were also produced, two of which were subsequently updated to the physical and operational configuration of the qualification and flight units. Positioning of lamp apertures and reflectors in these lights is such that the light is concentrated and intensified in a specific pattern rather than widely diffused. Indium amalgam control of mercury vapor pressure in the lamp gives high output at lamp ambient temperatures up to 105 C. A small amount of amalgam applied to each electrode stem helps to obtain fast warm-up. Shrinking a Teflon sleeve on the tube and potting metal caps on each end of the lamp minimizes dispersion of mercury vapor and glass particles in the event of accidental lamp breakage. Operation at 20 kHz allows the lamps to consume more power than at low frequency, thus increasing their light output and raising their efficiency. When used to expose color photographic film, light from the lamps produces results approximately equal to sunlight.

Kendall, F. B.↗
DOE OSTI2026

Operando Spectroscopic Analysis of Photovoltage Generation in Hematite Photoanodes

Solar-driven water splitting requires sufficient photovoltage to drive both water oxidation and proton reduction. Understanding the factors driving and limiting photovoltage generation is therefore crucial to optimizing photoelectrode design but has proven challenging to determine under operando conditions for photoanodes driving slow multiredox reactions such as water oxidation. In this work, operando optical spectroscopy is employed to measure the hole quasi-Fermi level (E F,p ) position in model hematite photoanodes as a function of applied bias and light intensity. The quasi-Fermi level splitting determined from these data are shown be in excellent agreement with the directly measured photovoltages, demonstrating the primarily electrochemical rather than primarily electrostatic origin of photovoltage in these photoelectrodes. E F,p pinning is observed at low light intensities and biases, indicative of hole trap states lying ∼0.2 eV above the valence band edge with a density of ∼1 nm −2 . Hole accumulation in these trap states is correlated with first order water oxidation. At higher light intensities and/or more anodic bias, E F,p becomes unpinned, assigned to saturation of these trap states, and correlated with the onset of third order water oxidation to molecular oxygen. Comparison with rate law analyses for other photoanodes indicates that such hole trap states may be a ubiquitous feature of metal oxides and suggests that materials processing strategies to suppress the density of such states would be a promising strategy to enhance photoanode performance.

Hematite↗
NASA NTRS2005

An Automated Flying-Insect-Detection System

An automated flying-insect-detection system (AFIDS) was developed as a proof-of-concept instrument for real-time detection and identification of flying insects. This type of system has use in public health and homeland security decision support, agriculture and military pest management, and/or entomological research. Insects are first lured into the AFIDS integrated sphere by insect attractants. Once inside the sphere, the insect's wing beats cause alterations in light intensity that is detected by a photoelectric sensor. Following detection, the insects are encouraged (with the use of a small fan) to move out of the sphere and into a designated insect trap where they are held for taxonomic identification or serological testing. The acquired electronic wing beat signatures are preprocessed (Fourier transformed) in real-time to display a periodic signal. These signals are sent to the end user where they are graphically displayed. All AFIDS data are pre-processed in the field with the use of a laptop computer equipped with LABVIEW. The AFIDS software can be programmed to run continuously or at specific time intervals when insects are prevalent. A special DC-restored transimpedance amplifier reduces the contributions of low-frequency background light signals, and affords approximately two orders of magnitude greater AC gain than conventional amplifiers. This greatly increases the signal-to-noise ratio and enables the detection of small changes in light intensity. The AFIDS light source consists of high-intensity Al GaInP light-emitting diodes (LEDs). The AFIDS circuitry minimizes brightness fluctuations in the LEDs and when integrated with an integrating sphere, creates a diffuse uniform light field. The insect wing beats isotropically scatter the diffuse light in the sphere and create wing beat signatures that are detected by the sensor. This configuration minimizes variations in signal associated with insect flight orientation.

Vann, Timi↗
NASA NTRS2007

An Automated Flying-Insect Detection System

An automated flying-insect detection system (AFIDS) was developed as a proof-of-concept instrument for real-time detection and identification of flying insects. This type of system has use in public health and homeland-security decision support, agriculture and military pest management, and/or entomological research. Insects are first lured into the AFIDS integrated sphere by insect attractants. Once inside the sphere, the insect s wing beats cause alterations in light intensity that is detected by a photoelectric sensor. Following detection, the insects are encouraged (with the use of a small fan) to move out of the sphere and into a designated insect trap where they are held for taxonomic identification or serological testing. The acquired electronic wing-beat signatures are preprocessed (Fourier transformed) in real time to display a periodic signal. These signals are sent to the end user where they are graphically. All AFIDS data are preprocessed in the field with the use of a laptop computer equipped with LabVIEW. The AFIDS software can be programmed to run continuously or at specific time intervals when insects are prevalent. A special DC-restored transimpedance amplifier reduces the contributions of low-frequency background light signals, and affords approximately two orders of magnitude greater AC gain than conventional amplifiers. This greatly increases the signal-to-noise ratio and enables the detection of small changes in light intensity. The AFIDS light source consists of high-intensity Al-GaInP light-emitting diodes (LEDs). The AFIDS circuitry minimizes brightness fluctuations in the LEDs and when integrated with an integrating sphere, creates a diffuse uniform light field. The insect wing beats isotropically scatter the diffuse light in the sphere and create wing-beat signatures that are detected by the sensor. This configuration minimizes variations in signal associated with insect flight orientation. Preliminary data indicate that AFIDS has sufficient sensitivity and frequency measuring capability to differentiate between male and female mosquitoes (Figure 1, bottom panel) and fruit flies (data not shown). Similar studies show that AFIDS can be utilized to detect discrete differences between two mosquito species, Aedes aegypti and Aedes albopictus. When fully deployable, a wireless network of AFIDS monitors could be used in combination with other remotely sensed data and visually displayed in a geographic information system (GIS) to provide real-time surveillance (see Figure 2). More accurate and sensitive insect population forecasts and effective rapid response and mitigation of insect issues would then be possible.

Vann, Timi↗
NASA NTRS1994

Management of fluorescent lamps in controlled environment chambers

Management of fluorescent lights is recommended to (1) maintain uniformity of light intensity over time and (2) permit reproducibility of lighting conditions during experimental replications. At the McGill Phytotron, the lighting intensity can be controlled to desired level because any individual pair of the 40 lamps in each chamber can be set to be 'on' at any particular time. A lamp canopy service history is maintained for each experiment permitting accurate replication of lighting conditions for subsequent replicate trials.

Romer, Mark↗
DOE OSTI2024

Coupling strongly correlated electron systems to a tunable electronic reservoir

Here, we study the effect of coupling an electronic reservoir to a Hubbard model and to a dimer Hubbard model. This is motivated by recent experiments on the effect of illumination on the insulator-metal transition in a vanadium oxides and photoconductive cadmium sulfide heterostructure. We model the system as an electronic reservoir hybridized to the correlated system. We assume that the light intensity controls the hybridization coupling strength. We find that the light intensity acts similarly as the temperature in the weak interaction regime. This is consistent with the role played by electronic reservoirs in out-of-equilibrium systems. In contrast, qualitative differences appear at strong coupling. We show that modeling the V 2 ⁢O 3 compound with a Hubbard model, our results describe qualitatively well the observed illumination-driven suppression of the insulator-metal transition. In contrast, in the DHM results fail to capture the mild suppression observed in the case of VO 2 . This indicates that the lattice may play an important role in this case.

Materials Science↗
NASA NTRS2000

Facility Designed and Built to Investigate the Combined Effects of Contaminant and Atomic Oxygen on a Light-Transmitting Surface

A need exists to investigate changes in the transparency of a light-transmitting surface during simultaneous exposure to a contaminant and an atomic oxygen (AO) flux. This mechanism may be responsible for the degradation of the light-transmitting surfaces of both photovoltaic cells and photodiodes currently in use on many low-Earth-orbit spacecraft. To address this need, researchers from the Electro-Physics Branch of the NASA Glenn Research Center at Lewis Field built such a test system within their AO beam facility. This facility produces an effective AO flux of 1.4 10(exp 16) atoms/sq cm/sec and contains a three-axis positioning system that provides the motion capability necessary for test operations. During testing, a target surface is held directly within the AO beam and close to two contaminant effusion cells. The effusion cells are shielded from the AO beam, and the outgassing contaminant is constrained to move across the target surface when heat is applied to either of the reservoirs. A light source is periodically moved over the target surface, and the transmitted light intensity is checked with a photodiode located below the target. This light source is also periodically checked with a separate photodiode, which is protected from contamination and AO exposure, to allow adjustments necessary to maintain a consistent light intensity.

Sechkar, Edward A.↗
NASA NTRS2013

Trace Contaminant Control: An In-Depth Study of a Silica-Titania Composite for Photocatalytic Remediation of Closed-Environment Habitat Air

This collection of studies focuses on a PCO system for the oxidation of a model compound, ethanol, using an adsorption-enhanced silica-TiO2 composite (STC) as the photocatalyst; studies are aimed at addressing the optimization of various parameters including light source, humidity, temperature, and possible poisoning events for use as part of a system for gaseous trace-contaminant control system in closed-environment habitats. The first goal focused on distinguishing the effect of photon flux (i.e., photons per unit time reaching a surface) from that of photon energy (i.e., wavelength) of a photon source on the PCO of ethanol. Experiments were conducted in a bench-scale annular reactor packed with STC pellets and irradiated with either a UV-A fluorescent black light blue lamp O max=365 nm) at its maximum light intensity or a UV-C germicidal lamp O. max=254 nm) at three levels of light intensity. The STC-catalyzed oxidation of ethanol was found to follow zero-order kinetics with respect to CO2 production, regardless of the photon source. Increased photon flux led to increased EtOH removal, mineralization, and oxidation rate accompanied by lower intermediate concentration in the effluent. The oxidation rate was higher in the reactor irradiated by UV-C than by UV-A (38.4 vs. 31.9 nM s-1 ) at the same photon flux, with similar trends for mineralization (53.9 vs. 43.4%) and reaction quantum efficiency (i.e., photonic efficiency, 63.3 vs. 50.1 nmol C02 ~mol photons-1 ). UV-C irradiation also led to decreased intermediate concentration in the effluent compared to UV -A irradiation. These results demonstrated that STC-catalyzed oxidation is enhanced by both increased photon flux and photon energy. The effect of temperature and relative humidity on the STC-catalyzed degradation of ethanol was also determined using the UV-A light source at its maximum intensity.

Coutts, Janelle L.↗
NASA NTRS1973

A study of phycophysiology in controlled environments

In an attempt to understand the responses of CHLORELLA to various quantities and qualities of light in space flight life support system, studies were designed to give the maximum rates of growth as well as maximum yields at different densities of algae under different light intensities, and under light of different wave lengths. The results of studies on the effects of light on algal growth revealed that the effect was not only positive, as had been assumed in the case of photosynthesis, but that light had a negative action also. Light at the blue end of the spectrum was clearly inhibitory to cell division and vegetative reproduction. Carbon dioxide also limited growth by inhibition of cell divisions in CHLORELLA as well as in the colorless yeast SACCHAROMYCES.

Krauss, R. W.↗
NASA NTRS2000

Intensity Biased PSP Measurement

The current pressure sensitive paint (PSP) technique assumes a linear relationship (Stern-Volmer Equation) between intensity ratio (I(sub 0)/I) and pressure ratio (P/P(sub 0)) over a wide range of pressures (vacuum to ambient or higher). Although this may be valid for some PSPs, in most PSPs the relationship is nonlinear, particularly at low pressures (less than 0.2 psia when the oxygen level is low). This non-linearity can be attributed to variations in the oxygen quenching (de-activation) rates (which otherwise is assumed constant) at these pressures. Other studies suggest that some paints also have non-linear calibrations at high pressures; because of heterogeneous (non-uniform) oxygen diffusion and c quenching. Moreover, pressure sensitive paints require correction for the output intensity due to light intensity variation, paint coating variation, model dynamics, wind-off reference pressure variation, and temperature sensitivity. Therefore to minimize the measurement uncertainties due to these causes, an in- situ intensity correction method was developed. A non-oxygen quenched paint (which provides a constant intensity at all pressures, called non-pressure sensitive paint, NPSP) was used for the reference intensity (I(sub NPSP)) with respect to which all the PSP intensities (I) were measured. The results of this study show that in order to fully reap the benefits of this technique, a totally oxygen impermeable NPSP must be available.

Subramanian, Chelakara S.↗
NASA NTRS2000

Intensity Biased PSP Measurement

The current pressure sensitive paint (PSP) technique assumes a linear relationship (Stern-Volmer Equation) between intensity ratio (I(sub o)/I) and pressure ratio (P/P(sub o)) over a wide range of pressures (vacuum to ambient or higher). Although this may be valid for some PSPs, in most PSPs the relationship is nonlinear, particularly at low pressures (less than 0.2 psia when the oxygen level is low). This non-linearity can be attributed to variations in the oxygen quenching (de-activation) rates (which otherwise is assumed constant) at these pressures. Other studies suggest that some paints also have non-linear calibrations at high pressures; because of heterogeneous (non-uniform) oxygen diffusion and quenching. Moreover, pressure sensitive paints require correction for the output intensity due to light intensity variation, paint coating variation, model dynamics, wind-off reference pressure variation, and temperature sensitivity. Therefore to minimize the measurement uncertainties due to these causes, an insitu intensity correction method was developed. A non-oxygen quenched paint (which provides a constant intensity at all pressures, called non-pressure sensitive paint, NPSP) was used for the reference intensity (I(sub NPSP) with respect to which all the PSP intensities (I) were measured. The results of this study show that in order to fully reap the benefits of this technique, a totally oxygen impermeable NPSP must be available.

Subramanian, Chelakara S.↗
NASA NTRS2017

Cosmic Infrared Background Fluctuations and Zodiacal Light

We performed a specific observational test to measure the effect that the zodiacal light can have on measurements of the spatial fluctuations of the near-IR (near-infrared)background. Previous estimates of possible fluctuations caused by zodiacal light have often been extrapolated from observations of the thermal emission at longer wavelengths and low angular resolution or from IRAC (Infrared Array Camera) observations of high-latitude fields where zodiacal light is faint and not strongly varying with time. The new observations analyzed here target the COSMOS (Cosmic Evolution Survey) field at low ecliptic latitude where the zodiacal light intensity varies by factors of approximately 2 over the range of solar elongations at which the field can be observed. We find that the white-noise component of the spatial power spectrum of the background is correlated with the modeled zodiacal light intensity. Roughly half of the measured white noise is correlated with the zodiacal light, but a more detailed interpretation of the white noise is hampered by systematic uncertainties that are evident in the zodiacal light model. At large angular scales (greater than or approximately equal to 100 arcseconds) where excess power above the white noise is observed, we find no correlation of the power with the modeled intensity of the zodiacal light. This test clearly indicates that the large-scale power in the infrared background is not being caused by the zodiacal light.

cosmology: observations aEuro" diffuse radiation a↗
DOE OSTI2024

Discovery of Multiple Light-Harvesting States of the Photosynthetic Protein PE545

Cryptophytes are photosynthetic microalga that flourish in a remarkable diversity of natural environments by using pigment-containing proteins with absorption maxima tuned to each ecological niche. While this diversity in the absorption has been well established, the subsequent photophysics is highly sensitive to the local protein environment and so may exhibit similar variation. Thermal fluctuations of the protein conformation are expected to introduce photophysical heterogeneity of the pigments that may have evolved important functional properties in a manner similar to that of the absorption. However, such heterogeneity is averaged out in ensemble measurements and, therefore, has not yet been probed. Here, we report single-molecule measurements of phycoerythrin 545 (PE545), the prototypical cryptophyte antenna protein, in its native dimeric form. A conformational ensemble was resolved consisting of distinct photophysical states with different light-harvesting properties. Proteins that did not quench, partially quenched, or fully quenched absorbed light were observed. Light intensity increased the quenched-state population of the dimer, potentially as a mechanism to deal with the extreme light intensities found in aqueous environments. Cross-linking, which mimics local interactions, introduces this light-dependent functionality while also suppressing other conformational dynamics. The cellular organization can, therefore, actively modulate the protein conformation and dynamics, selecting for distinct levels of light harvesting. Furthermore, the complex conformational equilibrium provides an additional mechanism for cryptophytes and likely other photosynthetic organisms to optimize solar energy capture and conversion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRSDate not supplied

Noise Reduction and Calibration for Aeroacoustic Loads from Unsteady Pressure-Sensitive Paint

Unsteady pressure-sensitive paint (uPSP) is a significant new technology for high spatial resolution measurement of complex dynamic surface pressure loading on a wind tunnel model, to better define flight vehicle buffet and aeroacoustic loads. Compared with the very sparse surface pressure measurements of traditional sensors, the pressure sensitivity of uPSP light reflectivity provides a visual measure of surface pressure fluctuations over a wide area illuminated by high intensity light, captured by a high-speed digital camera. Panda et al (AIAA Journal, May 2019) have shown good data is recoverable up to 10 kHz. In cases where available uPSP luminescence is low for a painted wind tunnel test model, significant noise levels have been observed primarily due to the discrete photon arrival variability of low intensity light (termed “shot noise”). In this case, uPSP measurements can exhibit unusually low signal to noise ratio (SNR of 0.1 or less). This paper will report on latest work to recover calibrated uPSP measurements which are noise free over a useful dynamic range of 10-15 dB. It will be shown how the distinct spatial correlations of both the shot noise and the underlying aeroacoustic surface pressure play an important role in obtaining a reliable measurement.

pressure-sensitive paint↗