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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 325 records · Page 18

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NASA NTRS1994

Circular electrode geometry metal-semiconductor-metal photodetectors

The invention comprises a high speed, metal-semiconductor-metal photodetector which comprises a pair of generally circular, electrically conductive electrodes formed on an optically active semiconductor layer. Various embodiments of the invention include a spiral, intercoiled electrode geometry and an electrode geometry comprised of substantially circular, concentric electrodes which are interposed. These electrode geometries result in photodetectors with lower capacitances, dark currents and lower inductance which reduces the ringing seen in the optical pulse response.

Mcaddo, James A.↗

NASA NTRS1995

Circular electrode geometry metal-semiconductor-metal photodetectors

Mcadoo, James A.↗

NASA NTRS2000

Ensemble Diffraction Measurements of Spray Combustion in a Novel Vitiated Coflow Turbulent Jet Flame Burner

An experimental investigation is presented of a novel vitiated coflow spray flame burner. The vitiated coflow emulates the recirculation region of most combustors, such as gas turbines or furnaces; additionally, since the vitiated gases are coflowing, the burner allows exploration of the chemistry of recirculation without the corresponding fluid mechanics of recirculation. As such, this burner allows for chemical kinetic model development without obscurations caused by fluid mechanics. The burner consists of a central fuel jet (droplet or gaseous) surrounded by the oxygen rich combustion products of a lean premixed flame that is stabilized on a perforated, brass plate. The design presented allows for the reacting coflow to span a large range of temperatures and oxygen concentrations. Several experiments measuring the relationships between mixture stoichiometry and flame temperature are used to map out the operating ranges of the coflow burner. These include temperatures as low 300 C to stoichiometric and oxygen concentrations from 18 percent to zero. This is achieved by stabilizing hydrogen-air premixed flames on a perforated plate. Furthermore, all of the CO2 generated is from the jet combustion. Thus, a probe sample of NO(sub X) and CO2 yields uniquely an emission index, as is commonly done in gas turbine engine exhaust research. The ability to adjust the oxygen content of the coflow allows us to steadily increase the coflow temperature surrounding the jet. At some temperature, the jet ignites far downstream from the injector tube. Further increases in the coflow temperature results in autoignition occurring closer to the nozzle. Examples are given of methane jetting into a coflow that is lean, stoichiometric, and even rich. Furthermore, an air jet with a rich coflow produced a normal looking flame that is actually 'inverted' (air on the inside, surrounded by fuel). In the special case of spray injection, we demonstrate the efficacy of this novel burner with a methanol spray in a vitiated coflow. As a proof of concept, an ensemble light diffraction (ELD) optical instrument was used to conduct preliminary measurements of droplet size distribution and liquid volume fraction.

Cabra, R.↗

NASA NTRS2007

Milli-Arcsecond Infrared Observations of the Nova RS Ophiuchi

We report on infrared interferometric measurements of the 2006 outburst of Nova RS Oph in H, K, and N bands. These measurements, conducted using the Infrared and Optical Telescope Array, the Palomar Testbed Interferometer, and the Keck Interferometer, show a small variation in the 3 mas size if this resolved source during the first 65 days of the outburst. Additionally, using interferometric closure phases, these observations show an unambiguous departure from point symmetry of the object. We also describe simultaneous N-band observations of the nova in two separate milli-arcsecond spatial regimes on day four in which we detect line emission indicating onset of the optically thin phase. These data represent the first science from the Keck Interferometer's nulling mode.

Barry, Richard K.↗

NASA NTRS2013

Phoenix Telemetry Processor

Phxtelemproc is a C/C++ based telemetry processing program that processes SFDU telemetry packets from the Telemetry Data System (TDS). It generates Experiment Data Records (EDRs) for several instruments including surface stereo imager (SSI); robotic arm camera (RAC); robotic arm (RA); microscopy, electrochemistry, and conductivity analyzer (MECA); and the optical microscope (OM). It processes both uncompressed and compressed telemetry, and incorporates unique subroutines for the following compression algorithms: JPEG Arithmetic, JPEG Huffman, Rice, LUT3, RA, and SX4. This program was in the critical path for the daily command cycle of the Phoenix mission. The products generated by this program were part of the RA commanding process, as well as the SSI, RAC, OM, and MECA image and science analysis process. Its output products were used to advance science of the near polar regions of Mars, and were used to prove that water is found in abundance there. Phxtelemproc is part of the MIPL (Multi-mission Image Processing Laboratory) system. This software produced Level 1 products used to analyze images returned by in situ spacecraft. It ultimately assisted in operations, planning, commanding, science, and outreach.

Stanboli, Alice↗

NASA NTRS2019

Evaluation of Brightness Temperature Sensitivity to Snowpack Physical Properties Using Coupled Snow Physics and Microwave Radiative Transfer Models

There are multiple existing microwave radiative transfer models (RTMs) to simulate the brightness temperature (Tb) of snowpacks. It is still challenging to have consistent Tb responses from RTMs due to individual physical formulations of the snowpack scattering process. This article examines three of the widely-used multi-layer RTMs: 1) the microwave emission model of layered snowpacks (MEMLS); 2) the dense media radiative transfer based on the quasi-crystalline approximation (QCA) of Mie scattering of densely packed sticky spheres (DMRTQMS); and 3) the Helsinki University of Technology (HUT) model. Interestingly, these models yield slightly different Tb responses when driven by the same physical snowpack properties. Tb variations, dependent on the choice of RTMs, are then evaluated to improve the understanding of model differences in microwave emission from a snowpack. We first perform a sensitivity study of the Tb predictions from the three RTMs as a function of snow grain sizes, densities, and depths. While Tb from all three RTMs decreases with increasing snow grain sizes, it is found that a scaling factor is required to have the same amount of Tb attenuation for small grain sizes within the Rayleigh scattering regime. For larger grain sizes, however, a scaling coefficient is not enough to match the model outputs due to the different scattering assumptions of the RTMs. For a single snow layer with increasing snow depths and densities, all three RTMs exhibit Tb attenuations arising from the increase in path lengths and optical depths. Further evaluations are conducted by feeding the three RTMs with the output of a snow physics model driven by in situ weather forcing in a coupled simulation. Outputs of this coupled model include snowpack physical properties and Tbs. By using snow stratigraphy observations, another set of Tb simulation is also conducted with RTMs driven by in situ snowpit observations. The snow physics outputs from the coupled case are compared against in situ snow stratigraphy observations.

Do Hyuk Kang↗

DOE OSTI2024

Cellulosic gels, films and composites including the gels, and methods of forming same

Disclosed are cellulose-based 5 flexible aerogels and xerogels containing bacterial cellulose nanorods, ribbons, fibers, and the like, wherein the gels have tunable optical, heat transfer, and stiffness properties. Further disclosed are highly transparent and flexible cellulose nanofiber-polysiloxane composite aerogels featuring enhanced mechanical robustness, tunable optical anisotropy, and low thermal conductivity.

Smalyukh, Ivan I.↗

DOE OSTI2025

Characterization of Flashback and Flame-Holding in a Jet-in-Crossflow Mixing Configuration with Methane-Hydrogen Fuel Blends

An approach that combines experimental and numerical analyses has been implemented to characterize the fundamentals of flashback events and flame-holding phenomena during high-hydrogen combustion in a jet-in-crossflow (JICF) configuration. Such flame dynamics are visualized experimentally using nanosecond (ns)-based hydroxyl planar laser-induced fluorescence (OH-PLIF) and chemiluminescence diagnostics techniques. The JICF burner has an optically accessible pre-mixing tube allowing the optical diagnostics. The testing was conducted for varied pre-mixer velocities (V) and equivalence ratio (ϕ) for 90%-100% (H2, by mole) H2/CH4 reactant mixtures at atmospheric temperature and pressure conditions. Two distinct flashback events were identified – conventional rich flashback and lean flashback, recorded while increasing ϕ and decreasing ϕ, respectively. The cause of lean flashback was attributed to the lower momentum flux ratio which bends the jet sharply, closer toward the injection plane. The mean OH-PLIF images characterized the flame-holding behavior where the flame was found to be stabilized on the leeward side only or on both windward and leeward sides as a lifted flame near the fuel port. A Large Eddy Simulation (LES) with detailed chemistry combustion modeling approach was implemented along an OH* sub-mechanism, and it showed qualitative agreement with the integrated line-of-sight chemiluminescence results as well as the planar OH-PLIF measurements.

flame holding↗

DOE OSTI2025

Characterization of Flashback and Flame-Holding in a Jet-In-Crossflow Mixing Configuration with Methane-Hydrogen Fuel Blends

An approach that combines experimental and numerical analyses has been implemented to characterize the fundamentals of flashback events and flame-holding phenomena during high-hydrogen combustion in a jet-in-crossflow (JICF) configuration. Such flame dynamics are visualized experimentally using nanosecond (ns)-based hydroxyl planar laser-induced fluorescence (OH-PLIF) and chemiluminescence (CL) diagnostics techniques. The JICF burner has an optically accessible pre-mixing tube allowing the optical diagnostics. The testing was conducted for varied pre-mixer velocities (V) and equivalence ratio (ϕ) for 90%-100% (H2, by mole) H2/CH4 reactant mixtures at atmospheric temperature and pressure conditions. Two distinct flashbacks were identified – conventional rich flashback and lean flashback, recorded while increasing ϕ and decreasing ϕ, respectively. The cause of lean flashback was attributed to lower flux ratio which bends the jet sharply, closer toward the injection plane. The flashback was found to occur along the boundary layer, assisted by the inner wall of the pre-mixer tube. The mean OH-PLIF images characterized the flame-holding behavior where the flame was found to be stabilized on the leeward side only or on both windward and leeward sides as a lifted flame near the fuel port.

flame holding↗

NASA NTRS2011

Design for On-Sun Evaluation of Evaporator Receivers

A heat pipe designed for operation as a solar power receiver should be optimized to accept the solar energy flux and transfer this heat into a reactor. Optical properties of the surface, thermal conductance of the receiver wall, contact resistance of the heat pipe wick, and other heat pipe wick properties ultimately define the maximum amount of power that can be extracted from the concentrated sunlight impinging on the evaporator surface. Modeling of solar power receivers utilizing optical and physical properties provides guidance to their design. On-sun testing is another important means of gathering information on performance. A test rig is being designed and built to conduct on-sun testing. The test rig is incorporating a composite strip mirror concentrator developed as part of a Small Business Innovative Research effort and delivered to NASA Glenn Research Center. In the strip concentrator numerous, lightweight composite parabolic strips of simple curvature were combined to form an array 1.5 m x 1.5 m in size. The line focus of each strip is superimposed in a central area simulating a point of focus. A test stand is currently being developed to hold the parabolic strip concentrator, track the sun, and turn the beam downward towards the ground. The hardware is intended to be sufficiently versatile to accommodate on-sun testing of several receiver concepts, including those incorporating heat pipe evaporators. Characterization devices are also being developed to evaluate the effectiveness of the solar concentrator, including a receiver designed to conduct calorimetry. This paper describes the design and the characterization devices of the on-sun test rig, and the prospect of coupling the concentrated sunlight to a heat pipe solar power receiver developed as part of another Small Business Innovative Research effort.

Jaworske, Donald A.↗

NASA NTRS1980

Investigation of direct integrated optics modulators

Direct modulation techniques applicable to integrated optics data preprocessors were investigated. Several methods of modulating a coherent optical beam by interaction with an incoherent beam were studied. It was decided to investigate photon induced conductivity changes in thin semiconductor cladding layers on optical waveguides. Preliminary calculations indicate significant changes can be produced in the phase shift in a propagating wave when the conductivity is changed by ten percent or more. Experimental devices to verify these predicted phase changes and experiments designed to prove the concept are described.

Batchman, T. E.↗

NASA NTRS1999

Near-Infrared Laser Pumped Intersubband THz Laser Gain in InGaAs-AlAsSb-InP Quantum Wells

We investigate the possibility of using InGaAs-AlAsSb-InP coupled quantum wells to generate THz radiation by means of intersubband optical pumping. We show that large conduction band offsets of these quantum wells make it possible to use conventional near-infrared diode lasers around 1.55 micron as pump sources. Taking into account the pump-probe coherent interaction and the optical nonlinearity for the pump field, we calculate the THz gain of the quantum well structure. We show that resonant Raman scattering enhances the THz gain at low and moderate optical pumping levels. When the pump intensity is strong, the THz gain is reduced by pump-induced population redistribution and pump-probe coherent interactions.

Liu, An-Sheng↗

NASA NTRS1982

Detection of radio emission from optically identified supernova remnants in M31

The Very Large Array was used to conduct a radio search at a wavelength of 20 cm for ten optically identified supernova remnants (SNRs) in M31. Five SNRs were detected, and for the other objects, upper limits to the emission were determined. On the average, the surface brightness of an SNR in M31 appears to be fainter than that of an SNR in the Galaxy. It is suggested that the median surface brightness at a given diameter is higher in late-type spirals than in Sb systems.

Dickel, J. R.↗

NASA NTRS2006

Integrated Modeling of Advanced Opto-Mechanical Systems

The design of optical hardware for space applications is particularly challenging when developing high performance, novel systems that have no precedent. Integrated modeling and analysis of such opto-mechanical systems seeks to describe the end-to-end performance of the hardware using mission-relevant metrics. This multidisciplinary analysis might start with thermal disturbances from observation maneuvers, compute the system temperatures, compute the distorted positions and shapes of the hardware and compute the resulting optical performance. Dynamic disturbances such as reaction wheel imbalance or inertia imbalance of optical delay lines might be applied to a structural dynamic model and used in a guidance and control analysis. Mission-relevant science metrics might include wavefront quality, pointing error or imaging stability. Assembling a tool chain that can be both nimble and effective when scaled to the high fidelity models of detail design has been challenging. An integrated thermal, mechanical and optical analysis capability suitable for detail design has been developed and verified through experimental measurement. This capability was used in the design of flight-like breadboard hardware and development of a test apparatus that established both the level of performance of the hardware and the validity of the analysis. The analysis includes prediction of the thermal environment of the test chamber, detailed temperature distributions on the breadboard hardware, fine scale deformations of the optical elements, and computation of the wavefront quality using geometric optics. A battery of tests were conducted to assess the experiment data acquisition, measurement and control system and to establish the performance of the hardware design and accuracy of the integrated modeling. Thermal loads that represent operational observing maneuvers were imposed and the hardware optical performance was measured and compared to analytical predictions.

optomechanical analysis↗

NASA NTRS2026

Influence of Processing Parameters on the Mechanical Properties of 3D Printed Borosilicate Particulate Reinforced Polymer Composites

Emerging composite materials are expanding the potential of additive manufacturing and enabling applications previously restricted by traditional manufacturing methods. The multi-phase nature of these composite materials combined with the complex in-ternal geometry of additively manufactured parts have enabled unique behavior, and potentially new applications. Additionally, these materials can be pyrolyzed to create dense metal, ceramic, and glass parts with geometries typically not achievable by tra-ditional processes. Additive manufacturing of borosilicate glass-based systems can open new applications in nuclear engineering, astronomy, and bone regrowth therapy. To elucidate the process-parameter relationship of borosilicate-polylactic acid (PLA) composites, mechanical testing was conducted and compared with a pure polylactic acid polymer baseline. Test specimens were fabricated by fused-filament fabrication with minimal post-processing. Yield strength, ultimate strength, and elastic modulus were calculated from stress-strain curves. Optical and scanning electron microscopy were conducted to observe the specimen microstructure before and after testing. The highest compressive yield strength for the composite was 28.22 MPa, and the highest compressive yield strength for PLA was 49.30 MPa. Print orientation was found to benefit the composite material but have a detrimental effect on the pure matrix material. An elastic modulus of 2.66 GPa was recorded for the borosilicate-PLA composite at 100% infill, 1 shell wall, and layer lines parallel to compression axis. Microscopy revealed that lower modulus composite specimens had the particulates re-distributed within the matrix. Tensile testing was done according to a polymer testing standard, which caused difficulties obtaining consistent fracture within the gauge length.

mechanical testing↗

NASA NTRS1992

Development of a fiber optic high temperature strain sensor

From 1 Apr. 1991 to 31 Aug. 1992, the Georgia Tech Research Institute conducted a research program to develop a high temperature fiber optic strain sensor as part of a measurement program for the space shuttle booster rocket motor. The major objectives of this program were divided into four tasks. Under Task 1, the literature on high-temperature fiber optic strain sensors was reviewed. Task 2 addressed the design and fabrication of the strain sensor. Tests and calibration were conducted under Task 3, and Task 4 was to generate recommendations for a follow-on study of a distributed strain sensor. Task 4 was submitted to NASA as a separate proposal.

Rausch, E. O.↗

NASA NTRS2004

Poco Graphite Inc. SuperSiC 0.25m Mirror Cryogenic Test Result

SuperSiC, a low areal density material, developed by POCO Graphite, have been used as mirror substrate for high energy lasers, laser radar systems, surveillance, telescopes, scan mirrors and satellites. SuperSiC has excellent thermal properties and cryogenic stability. It exhibits exceptional polishability for reflective optics with high strength, stiffness, and excellent thermal conductivity. A lightweighted 0.2-diameter polished SuperSic mirror was tested at cryogenic temperature at NASMSFC. Optical test results showed 6nm cry0 deformation from ambient to 30 degrees Kelvin and little to no change in its surface figure due to cry0 cycling.

Eng, Ron↗

NASA NTRS1999

Research for Electronic Fiber Optics Technologists

The intent of this project was to provide research experiences for socially and economically disadvantaged students in networking via fiber optics. The objectives of this project were: 1) To provide knowledge and skills needed by students to use the tools and equipment essential to networking NASA's and the university's topologies; 2) To provide the student researchers with needed mathematical skills and concepts to progress in fiber optic technology; 3) To afford the principal investigator an opportunity to become certified in fiber optics; 4) To build a transmitter and receiver circuit that will be linked by fiber-optic cable to demonstrate mastery of concepts; and 5) To conduct research for NASA and the University in the fiber-optic system. The research will attempt to develop applications for THUNDER (Thin-layer Composite Unimorph Ferroelectric Driver and Sensor) and LARC-SI (Langley Research Center- Soluble Polyimide), (inventions at NASA/LaRC) and fiber-optic technology that will be beneficial to NASA, the university and the consumer. This research has the potential of improving the nation's manpower in the area of fiberoptic technology. It will allow students the opportunity to participate in visible research at NASA and in industry.

Lawrence, Ellis E.↗