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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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NASA NTRS2005

Mid-IR interband cascade lasers

Efficient mid-IR interband cascade (IC) lasers are developed based on 111-V semiconductor materials to cover wavelength range from 2.7 to 5.6 (mu)m. These IC lasers reuse injected electrons in cascade stages for photon generation with high quantum efficiency to achieve high output powers. Also, IC lasers have low threshold current density with very efficient use of applied voltage, resulting in reduced power consumptions. Single-mode distributed feedback lasers have been made, and integrated into aircraft and balloon instrument which made measurements of CH4 and HCI. In this work, the characteristics of IC lasers and their recent development are reviewed.

mid - infrared↗

NASA NTRS2006

3-D Mixed Mode Delamination Fracture Criteria - An Experimentalist's Perspective

Many delamination failure criteria based on fracture toughness have been suggested over the past few decades, but most only covered the region containing mode I and mode II components of loading because that is where toughness data existed. With new analysis tools, more 3D analyses are being conducted that capture a mode III component of loading. This has increased the need for a fracture criterion that incorporates mode III loading. The introduction of a pure mode III fracture toughness test has also produced data on which to base a full 3D fracture criterion. In this paper, a new framework for visualizing 3D fracture criteria is introduced. The common 2D power law fracture criterion was evaluated to produce unexpected predictions with the introduction of mode III and did not perform well in the critical high mode I region. Another 2D criterion that has been shown to model a wide range of materials well was used as the basis for a new 3D criterion. The new criterion is based on assumptions that the relationship between mode I and mode III toughness is similar to the relation between mode I and mode II and that a linear interpolation can be used between mode II and mode III. Until mixed-mode data exists with a mode III component of loading, 3D fracture criteria cannot be properly evaluated, but these assumptions seem reasonable.

Reeder, James R.↗

NASA NTRS2022

On the Existence of Fast Modes in Compressible Magnetohydrodynamic Turbulence

We study the existence and properties of fast magnetosonic modes in 3D compressible MHD turbulence by carrying out a number of simulations with compressible and incompressible driving conditions. We use two approaches to determine the presence of fast modes: mode decomposition based on spatial variations only and spatio-temporal 4D fast Fourier transform (4D FFT) analysis of all fluctuations. The latter method enables us to quantify fluctuations that satisfy the dispersion relation of fast modes with finite frequency. Overall, we find that the fraction of fast modes identified via the spatio-temporal 4D FFT approach in total fluctuation power is either tiny with nearly incompressible driving or ∼2% with highly compressible driving. We discuss the implications of our results for understanding the compressible fluctuations in space and astrophysical plasmas.

Zhaoming Gan↗

NASA NTRS1992

High power singlemode edge-emitting master oscillator power amplifier

An edge-emitting monolithically integrated master oscillator power amplifier (M-MOPA) has been fabricated by integrating a distributed Bragg reflector laser with a 500 microns long single mode amplifier. The M-MOPA contains a strained InGaAs quantum well in the active region and operates at about 981.5 nm in an edge-emitting fashion with maximum powers in excess of 175 mW. Single longitudinal and transverse mode operation is maintained to powers in excess of 110 mW CW.

O'Brien, S.↗

NASA NTRS1992

Modulation characteristics of a high-power semiconductor Master Oscillator Power Amplifier (MOPA)

A semiconductor master oscillator-power amplifier was demonstrated using an anti-reflection (AR) coated broad area laser as the amplifier. Under CW operation, diffraction-limited single-longitudinal-mode powers up to 340 mW were demonstrated. The characteristics of the far-field pattern were measured and compared to a two-dimensional reflective Fabry-Perot amplifier model of the device. The MOPA configuration was modulated by the master oscillator. Prior to injection into the amplifier, the amplitude and frequency modulation properties of the master oscillator were characterized. The frequency response of the MOPA configuration was characterized for an AM/FM modulated injection beam, and was found to be a function of the frequency detuning between the master oscillator and the resonant amplifier. A shift in the phase was also observed as a function of frequency detuning; this phase shift is attributed to the optical phase shift imparted to a wave reflected from a Fabry-Perot cavity. Square-wave optical pulses were generated at 10 MHz and 250 MHz with diffraction-limited peak powers of 200 mW and 250 mW. The peak power for a given modulation frequency is found to be limited by the injected power and the FM modulation at that frequency. The modulation results make the MOPA attractive for use as a transmitter source in applications such as free-space communications and ranging/altimetry.

Cornwell, Donald Mitchell, Jr.↗

NASA NTRS2013

Quasi-Linear Circuit

This work involved developing spacequalifiable switch mode DC/DC power supplies that improve performance with fewer components, and result in elimination of digital components and reduction in magnetics. This design is for missions where systems may be operating under extreme conditions, especially at elevated temperature levels from 200 to 300 degC. Prior art for radiation-tolerant DC/DC converters has been accomplished utilizing classical magnetic-based switch mode converter topologies; however, this requires specific shielding and component de-rating to meet the high-reliability specifications. It requires complex measurement and feedback components, and will not enable automatic re-optimization for larger changes in voltage supply or electrical loading condition. The innovation is a switch mode DC/DC power supply that eliminates the need for processors and most magnetics. It can provide a well-regulated voltage supply with a gain of 1:100 step-up to 8:1 step down, tolerating an up to 30% fluctuation of the voltage supply parameters. The circuit incorporates a ceramic core transformer in a manner that enables it to provide a well-regulated voltage output without use of any processor components or magnetic transformers. The circuit adjusts its internal parameters to re-optimize its performance for changes in supply voltage, environmental conditions, or electrical loading at the output

Bradley, William↗

NASA NTRS1990

HgCdTe for NASA EOS missions and detector uniformity benchmarks

Important NASA Earth Observing System (EOS) missions, Atmospheric Infrared Sounder (AIRS) and Moderate Resolution Imaging Spectrometer (MODIS-N), which require detector spectral response in the range of 14 to 17 microns at medium background flux levels and operation in the range of temperatures between 65 to 95 K, will be flown beginning in the next few years. Currently, a prime candidate detector technology for these missions is trapping-mode photoconductive HgCdTe devices. These devices can be tailored to the exact cutoff wavelengths required by those missions, and thus offer the performance advantages of an intrinsic detector which is ideally matched to the mission wavelength. Under the long wavelength-background-temperature conditions of these EOS missions, any detector will at best be thermal generation-recombination noise limited. Photoconductive devices are generally preferred under these circumstances, since at elevated temperatures their performance degrades with n(sub i) while for photovoltaic detectors performance degrades as n sub i(exp 2) n sub i is the intrinsic carrier concentration which is a function of alloy composition and temperature, but not doping. Very high performance trapping-mode photoconductive HgCdTe detectors have been developed which can be reproducibly fabricated. Detectivity (D asterisk) at 80K and 16 micron cutoff wavelength in excess of 10(exp 11) Jones has been measured for these devices. Power dissipation is at least two orders of magnitude less than conventional HgCdTe photoconductors - on the order of 0.12 W/cm(exp 2) compared with 12 W/cm(exp 2). EOS missions define thermal noise limited conditions for the long wavelength operating bands. Trapping-mode photoconductive HgCdTe detectors are linear under such conditions and responsivity is independent of background flux. At lower temperatures or high flux conditions in which background flux limits detector performance, trapping-mode detectors have a responsivity which varies with background flux. Internal calibration must be provided for radiometric measurements under the latter conditions (not an EOS mission concern). Liquid phase epitaxy is used to grow these HgCdTe device structures. This technique has been shown to give control of the cutoff wavelength on the order of 16 plus or minus 1 micron or less, both from run to run and across wafer dimensions of several centimeters on a side.

Norton, Paul R.↗

NASA NTRS1965

Tiny biomedical amplifier combines high performance, low power drain

Transistorized, portable, high performance amplifier with low power drain facilitates biomedical studies on mobile subjects. This device, which utilizes a differential input to obtain a common-mode rejection, is used for amplifying electrocardiogram and electromyogram signals.

Deboo, G. J.↗

NASA NTRS1979

Hybrid ECG signal conditioner

Circuit with high common-mode rejection has ability to filter and amplify accepted analog electrocardiogram (ECG) signals of varying amplitude, shape, and polarity. In addition, low power circuit develops standardized pulses that can be counted and averaged by heart/breath rate processor.

Rinard, G. A.↗

NASA NTRS1987

An overview of DREV's activities on pulsed CO2 laser transmitters: Frequency stability and lifetime aspects

After introducing the desired features in a transmitter for laser radar applications, the output characteristics of several configurations of frequency-stable TEA-CO2 lasers are reviewed. Based on work carried out at the Defence Research Establishment Valcartier (DREV), output pulses are examined from short cavity lasers, CW-TEA hybrid lasers, and amplifiers for low power pulses. It is concluded that the technique of injecting a low-power laser beam into a TEA laser resonator with Gaussian reflectivity mirrors should be investigated because it appears well adapted to producing high energy, single mode, low chirp pulses. Finally, a brief report on tests carried out on catalysts composed of stannic oxide and noble metals demonstrates the potential of these catalysts, operating at close to room temperature, to provide complete closed-cycle laser operation.

Cruickshank, James↗

NASA NTRS1988

High-power AlGaAs channeled substrate planar diode lasers for spaceborne communications

A high power channeled substrate planar AlGaAs diode laser with an emission wavelength of 8600 to 8800 A was developed. The optoelectronic behavior (power current, single spatial and spectral behavior, far field characteristics, modulation, and astigmatism properties) and results of computer modeling studies on the performance of the laser are discussed. Lifetest data on these devices at high output power levels is also included. In addition, a new type of channeled substrate planar laser utilizing a Bragg grating to stabilize the longitudinal mode was demonstrated. The fabrication procedures and optoelectronic properties of this new diode laser are described.

Connolly, J. C.↗

NASA NTRS1993

The free-electron laser in a symmetrical confocal resonator

A tapered wiggler is used in a FEL oscillator to improve the saturation efficiency. During signal buildup the tapered wiggler does not provide optimum phase synchronism between the electron beam and the electromagnetic wave, resulting in an appreciable loss in small-signal gain. This problem can be ameliorated by using a multicomponent wiggler, which is a combination of a uniform wiggler and a tapered section. During buildup, gain is primarily contributed by the linear element, and at high power levels the gain and efficiency are enhanced by the taper. Ideally, one would like to have the optical waist location near the linear section at small-signal levels and at near the tapered section at high power levels. Placing the FEL in a symmetrical confocal resonator approaches this desired effect automatically since it has the unique characteristic that a stable mode exists for all locations of the waist of a Gaussian beam along the axis of the interferometer.

Ozcan, Meric↗

NASA NTRS1999

The Photospheric Convection Spectrum

Spectra of the photospheric cellular flows are determined from Solar and Heliospheric Observatory/Michelson Doppler Imager (SOHO/MDI) observations. Spherical harmonic decompositions are obtained from the full-disc observations. Fourier decompositions are obtained from the high-resolution observations. The p-mode oscillation signals and instrumental artifacts are reduced by temporal filtering of the Doppler data. The resulting spectra give power (kinetic energy) per wavenumber for effective spherical harmonic degrees from 1 to about 3000. The spectra show distinct peaks representing granules and supergranules but no distinct features at wavenumbers representative of mesogranules or giant cells.

Hathaway, David H.↗

NASA NTRS1999

The Photospheric Convection Spectrum

Spectra of the cellular photospheric flows are determined from observations acquired by the MDI instrument on the SOHO spacecraft. Spherical harmonic spectra are obtained from the full-disk observations. Fourier spectra are obtained from the high-resolution observations. The p-mode oscillation signals and instrumental artifacts are reduced by temporal filtering of the Doppler data. The resulting spectra give power (kinetic energy) per wavenumber for effective spherical harmonic degrees from 1 to over 3000. The spectra show distinct peaks representing granules and supergranules but no distinct features at wavenumbers representative of mesogranu;es or giant cells. The observed cellular patterns and spectra are well represented by a model that only includes granules and supergranules.

Hathaway, D. H.↗

NASA NTRS2012

NASA Tech Briefs, August 2012

Topics covered include: Mars Science Laboratory Drill; Ultra-Compact Motor Controller; A Reversible Thermally Driven Pump for Use in a Sub-Kelvin Magnetic Refrigerator; Shape Memory Composite Hybrid Hinge; Binding Causes of Printed Wiring Assemblies with Card-Loks; Coring Sample Acquisition Tool; Joining and Assembly of Bulk Metallic Glass Composites Through Capacitive Discharge; 670-GHz Schottky Diode-Based Subharmonic Mixer with CPW Circuits and 70-GHz IF; Self-Nulling Lock-in Detection Electronics for Capacitance Probe Electrometer; Discontinuous Mode Power Supply; Optimal Dynamic Sub-Threshold Technique for Extreme Low Power Consumption for VLSI; Hardware for Accelerating N-Modular Redundant Systems for High-Reliability Computing; Blocking Filters with Enhanced Throughput for X-Ray Microcalorimetry; High-Thermal-Conductivity Fabrics; Imidazolium-Based Polymeric Materials as Alkaline Anion-Exchange Fuel Cell Membranes; Electrospun Nanofiber Coating of Fiber Materials: A Composite Toughening Approach; Experimental Modeling of Sterilization Effects for Atmospheric Entry Heating on Microorganisms; Saliva Preservative for Diagnostic Purposes; Hands-Free Transcranial Color Doppler Probe; Aerosol and Surface Parameter Retrievals for a Multi-Angle, Multiband Spectrometer LogScope; TraceContract; AIRS Maps from Space Processing Software; POSTMAN: Point of Sail Tacking for Maritime Autonomous Navigation; Space Operations Learning Center; OVERSMART Reporting Tool for Flow Computations Over Large Grid Systems; Large Eddy Simulation (LES) of Particle-Laden Temporal Mixing Layers; Projection of Stabilized Aerial Imagery Onto Digital Elevation Maps for Geo-Rectified and Jitter-Free Viewing; Iterative Transform Phase Diversity: An Image-Based Object and Wavefront Recovery; 3D Drop Size Distribution Extrapolation Algorithm Using a Single Disdrometer; Social Networking Adapted for Distributed Scientific Collaboration; General Methodology for Designing Spacecraft Trajectories; Hemispherical Field-of-View Above-Water Surface Imager for Submarines; and Quantum-Well Infrared Photodetector (QWIP) Focal Plane Assembly.

Source record↗

NASA NTRS2016

Status of the Development of Flight Power Processing Units for the NASAs Evolutionary Xenon Thruster - Commercial (NEXT-C) Project

A pathfinder prototype unit and two flight power processing units (PPUs) are being developed by the Aerojet Rocketdyne Corporation in Redmond, Washington and ZIN Technologies in Cleveland, Ohio, in support of the NEXT-C Project. This project is being led by the NASA Glenn Research Center in Cleveland, Ohio, and will also yield two flight thrusters. This hardware is being considered to be provided as Government Furnished Equipment for the New Frontiers Program, and is applicable to a variety of planetary science missions and astrophysics science missions. The design of the NEXT-C PPU evolves from the hardware fabricated under the NEXT technology development project. The power processing unit operates from two sources: a wide input 80 to 160 V high-power bus and a nominal 28 V low-power bus. The unit includes six power supplies. Four power supplies (beam, accelerator, discharge, and neutralizer keeper) are needed for steady state operation, while two cathode heater power supplies (neutralizer and discharge) are utilized during thruster startup. The unit in total delivers up to 7 kW of regulated power to a single gridded-ion thruster. Significant modifications to the initial design include: high-power adaptive-delay control, upgrade of design to EEE-INST-002 compliance, telemetry accuracy improvements, incorporation of telemetry to detect plume-mode operation, and simplification of the design in select areas to improve manufacturability and commercialization potential. The project is presently in the prototype phase and preparing for qualification level environmental testing.

NASAaEuro(TM)s Evolutionary Xenon Thruster↗

NASA NTRS2018

A W-Band Spatial Power-Combining Amplifier using GaN MMICs

In this paper, we describe a miniature powercombiner for monolithic millimetre-wave integrated circuit (MMIC) chips using spatial power-combining with cavity modes. We have designed GaN MMIC power amplifier chips for 94 GHz, and illustrate the concept of the W-Band Spatial Power Combining Amplifier (WSPCA). Using 1 Watt, 94 GHz MMIC chips in a two-way cavity mode combiner, we were able to achieve 2 Watts of output power with 9 dB gain and 15 % PAE. This technique could be extended to high power MMICs and larger numbers of chips to achieve higher output power in a compact size. The applications include earth science radar, but may be extended to other applications requiring wider bandwidth.

Gawande, Rohit↗

NASA NTRSDate not supplied

SPIKE-Dx : A Low-Power High-Throughput Fault Diagnostics Tool using Spiking Neural Networks for Constrained Systems

Diagnostic systems are important for many aerospace systems, which are severely limited in available power, like cubesats or UAVs. Therefore, traditional diagnostics systems cannot be used due to their substantial footprint and constraints. In this paper, we present our very low power diagnostic tool SPIKE-DX to monitor critical systems with constrained computational and energy resources. This is made possible through spiking neural networks (SNNs), which are executable within optimized simulation environments and further implemented on on cutting-edge neuromorphic hardware. Based upon FMEA (Failure Mode and Effect Analysis) framework, Diagnostic Bayesian Networks (DBNs) can be constructed that provide powerful means for diagnostic reasoning. In this paper, we describe such DBNs and a method to automatically translate the DBN into highly structured networks of spiking neurons for execution in SPIKE-DX.

Spiking Neural Networks↗