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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Coherent communication link using diode-pumped lasers

Work toward developing a diffraction limited, single frequency, modulated transmitter suitable for coherent optical communication or direct detection communication is discussed. Diode pumped, monolithic Nd:YAG nonplanar ring oscillators were used as the carrier beam. An external modulation technique which can handle high optical powers, has moderate modulation voltage, and which can reach modulation rates of 1 GHz was invented. Semiconductor laser pumped solid-state lasers which have high output power (0.5 Watt) and which oscillate at a single frequency, in a diffraction limited beam, at the wavelength of 1.06 microns were built. A technique for phase modulating the laser output by 180 degrees with a 40-volt peak to peak driving voltage is demonstrated. This technique can be adapted for amplitude modulation of 100 percent with the same voltage. This technique makes use of a resonant bulk modulator, so it does not have the power handling limitations of guided wave modulators.

Kane, Thomas J.↗
NASA NTRS1994

Unstable-Resonator Oscillator/Amplifier Diode Laser

Fabricated as single-chip integrated circuit. Device based partly on concept proved in commercial solid-state lasers: using unstable-resonator oscillator to define electromagnetic mode and, following oscillator, traveling-wave amplifier to generate high power. Mode-definition and power-amplification functions optimized separately. Hyperbolic-grating, unstable-resonator oscillator/amplifier diode laser produces single-longitudinal-mode, broad, laterally coherent, diffraction-limited, high-power beam.

Lang, Robert J.↗
NASA NTRS1947

Wind-Tunnel Investigation of a 1/5-Scale Model of the Ryan XF2R Airplane

Wind-tunnel tests on a 1/5-scale model of the Ryan XF2R airplane were conducted to determine the aerodynamic characteristics of the air intake for the front power plant, a General Electric TG-100 gas turbine, and to determine the stability and control characteristics of the airplane. The results indicated low-dynamic-pressure recover3- for the air intake to the TG-100 gas turbine ~rith the standard propeller in operation. Propeller cuffs were designed and tested for the purpose of imp~oving the dynamic-pressure recovery. Data obtained with the cuffs installed and the gap between the spinner an& the cuff sealed indicated a substantial gain in dynamic pressure recovery over that obtained with the standard propeller and with the cuffed propeller unsealed. Stability and control tests were conducted with the sealed cuffs installed on the propeller. The data from these tests indicated the following unsatisfactory characteristics for the airplane: 1. Marginal static longitudinal stability. 2. Inadequate directional stability and control. 3. Rudder-pedal-force reversal in the climb condition. 4. Negative dihedral effect in the power-on approach and wave-off conditions.

Wong, Park Y.↗
NASA NTRS2009

Empirical Constraints on Proton and Electron Heating in the Fast Solar Wind

This paper presents analyses of measured proton and electron temperatures in the high-speed solar wind that are used to calculate the separate rates of heat deposition for protons and electrons. It was found that the protons receive about 60% of the total plasma heating in the inner heliosphere, and that this fraction increases to approximately 80% by the orbit of Jupiter. The empirically derived partitioning of heat between protons and electrons is in rough agreement with theoretical predictions from a model of linear Vlasov wave damping. For a modeled power spectrum consisting only of Alfvenic fluctuations, the best agreement was found for a distribution of wavenumber vectors that evolves toward isotropy as distance increases.

Cranmer, Steven R.↗
NASA NTRS2001

Terahertz-Regime, Micro-VEDs: Evaluation of Micromachined TWT Conceptual Designs

Summary form only given. The Terahertz (THz) region of the electromagnetic spectrum (approx.300-3000 GHz) has enormous potential for high-data-rate communications, spectroscopy, astronomy, space research, medicine, biology, surveillance, remote sensing, industrial process control, etc. The most critical roadblock to full exploitation of the THz band is lack of coherent radiation sources that are powerful (0.01-10.0 W continuous wave), efficient (>1 %), frequency agile (instantaneously tunable over 1% bandwidths or more), reliable, and relatively inexpensive. Micro-machined Vacuum Electron Devices (micro-VEDs) represent a promising solution. We describe prospects for miniature, THz-regime TWTs fabricated using micromachining techniques. Several approx.600 GHz conceptual designs are compared. Their expected performance has been analyzed using SD, 2.51), and 3D TWT codes. A folded waveguide (FWG) TWT forward-wave amplifier design is presented based on a Northrop Grumman (NGC) optimized design procedure. This conceptual device is compared to the simulated performance of a novel, micro-VED helix TWT. Conceptual FWG TWT backward-wave amplifiers and oscillators are also discussed. A scaled (100 GHz) FWG TWT operating at a relatively low voltage (-12 kV) is under development at NGC. Also, actual-size micromachining experiments are planned to evaluate the feasibility of arrays of micro-VED TWTs. Progress and results of these efforts are described. This work was supported, in part by AFOSR, ONR, and NSF.

Booske, John H.↗
NASA NTRS2012

Radar Scattering and Block Size Properties of Lunar Crater Ejecta From Mini-RF and LROC NAC Data

A major objective of the Mini-RF experiment is to distinguish lunar surfaces that may contain water/ice deposits [1,2]. Better understanding of the backscattering properties of craters of varying age and size is crucial for interpreting data received from the Mini-RF. The Mini-RF transmits a circularly polarized RF electromagnetic energy and coherently receives orthogonal linear polarization echoes [1]. The Mini- RF maps in two separate bands ( =12.6 and 4.5 cm) at a high resolution mode of 30 m/pixel [1]. Given the variables mentioned, the four stokes parameters are reconstructed. The Circular Polarization Ratio (CPR) is calculated for the purposes of understanding subsurface and surface roughness. The CPR is determined from reflections acquired from the ratio of power of the transmitted radio wave in same sense to the reflected radio wave in the opposite sense [1]. Ice in the permanently shadowed regions (PSRs) would be transparent to radar, but the inclusions of materials and imperfections would cause the radio wave to reflect multiple times [3], enhancing the number of same sense reflections and increasing the CPR. In addition, ice also displays the coherent backscatter opposition effect (CBOE), an interferrometric addition of same sense backscatter that further increases the CPR of ice targets [7]. High CPR values also correlate to multiple reflections and are typically associated with very rough surfaces [3]. The average dry lunar surface has a CPR in the range of 0.2-0.4 at 48deg incidence [3]. The purpose of this study is to begin to quantify degrees of surface wavelength-scale roughness with CPR and to understand how such surface roughness is created and gradually destroyed by erosion on the lunar surface. Another goal is to identify and isolate the possible causes of high CPR within the shadowed areas of anomalous polar craters [3]. All the studied craters are non-polar, so that we can see into their interiors in NAC images. The idea is to understand what controls blockiness in these craters so that we can rule out rocks (and rule in ice) for the anomalous polar dark ones [3].

Spudis, P. D.↗
NASA NTRS2013

NASA Tech Briefs, April 2013

Topics covered include: Fully Integrated, Miniature, High-Frequency Flow Probe Utilizing MEMS Leadless SOI Technology; Nanoscale Surface Plasmonics Sensor With Nanofluidic Control; Advanced Dispersed Fringe Sensing Algorithm for Coarse Phasing Segmented Mirror Telescopes; Neural Network Back-Propagation Algorithm for Sensing Hypergols; Bulk Moisture and Salinity Sensor; Change-Based Satellite Monitoring Using Broad Coverage and Targetable Sensing; Circularly Polarized Microwave Antenna Element with Very Low Off-Axis Cross-Polarization; Ultra-Low Heat-Leak, High-Temperature Superconducting Current Leads for Space Applications; Flash Cracking Reactor for Waste Plastic Processing; An Automated Safe-to-Mate (ASTM) Tester; Wireless Chalcogenide Nanoionic-Based Radio-Frequency Switch; Compute Element and Interface Box for the Hazard Detection System; DOT Transmit Module; Composite Aerogel Multifoil Protective Shielding; Li-Ion Electrolytes with Improved Safety and Tolerance to High-Voltage Systems; Polymer-Reinforced, Non-Brittle, Lightweight Cryogenic Insulation; Controlled, Site-Specific Functionalization of Carbon Nanotubes with Diazonium Salts; Regenerable Sorbent for CO2 Removal; Sprayable Aerogel Bead Compositions With High Shear Flow Resistance and High Thermal Insulation Value; Lexan Linear Shaped Charge Holder with Magnets and Backing Plate; Robotic Ankle for Omnidirectional Rock Anchors; Wind, Wave, and Tidal Energy Without Power Conditioning; An Active Heater Control Concept to Meet IXO Type Mirror Module Thermal-Structural Distortion Requirement; Waterless Clothes-Cleaning Machine; Integrated Electrical Wire Insulation Repair System; LVGEMS Time-of-Flight Mass Spectrometry on Satellites; Surface Inspection Tool for Optical Detection of Surface Defects; Per-Pixel, Dual-Counter Scheme for Optical Communications; Certification-Based Process Analysis; Surface Navigation Using Optimized Waypoints and Particle Swarm Optimization; Smart-Divert Powered Descent Guidance to Avoid the Backshell Landing Dispersion Ellipse; Estimating Foreign-Object-Debris Density from Photogrammetry Data; Adaptive Sampling of Spatiotemporal Phenomena with Optimization Criteria; Building a 2.5D Digital Elevation Model From 2D Imagery; Eyes on the Earth 3D; Target Trailing With Safe Navigation for Maritime Autonomous Surface Vehicles; Adams-Based Rover Terramechanics and Mobility Simulator - ARTEMIS; ISTP CDF Skeleton Editor; Uplink Summary Generator (ULSGEN) Version 1.0; Robotics On-Board Trainer (ROBoT); Software Engineering Tools for Scientific Models; Automatic Data Filter Customization Using a Genetic Algorithm; Tracker Toolkit; Towards Efficient Scientific Data Management Using Cloud Storage; On a Formal Tool for Reasoning About Flight Software Cost Analysis; A Nanostructured Composites Thermal Switch Controls Internal and External Short Circuit in Lithium Ion Batteries; Spacecraft Crew Cabin Condensation Control; and Functional Near-Infrared Spectroscopy Signals Measure Neuronal Activity in the Cortex.

Source record↗
NASA NTRS2013

Magnetostrictive Alternator

This innovation replaces the linear alternator presently used in Stirling engines with a continuous-gradient, impedance-matched, oscillating magnetostrictive transducer that eliminates all moving parts via compression, maintains high efficiency, costs less to manufacture, reduces mass, and eliminates the need for a bearing system. The key components of this new technology are the use of stacked magnetostrictive materials, such as Terfenol-D, under a biased magnetic and stress-induced compression, continuous-gradient impedance-matching material, coils, force-focusing metallic structure, and supports. The acoustic energy from the engine travels through an impedancematching layer that is physically connected to the magnetostrictive mass. Compression bolts keep the structure under compressive strain, allowing for the micron-scale compression of the magnetostrictive material and eliminating the need for bearings. The relatively large millimeter displacement of the pressure side of the impedance-matching material is reduced to micron motion, and undergoes stress amplification at the magnetostrictive interface. The alternating compression and expansion of the magnetostrictive material creates an alternating magnetic field that then induces an electric current in a coil that is wound around the stack. This produces electrical power from the acoustic pressure wave and, if the resonant frequency is tuned to match the engine, can replace the linear alternator that is commonly used.

Dyson, Rodger↗
NASA NTRS2016

Free-Space Quantum Key Distribution with a High Generation Rate Potassium Titanyl Phosphate Waveguide Photon-Pair Source

A high generation rate photon-pair source using a dual element periodically-poled potassium titanyl phosphate (PP KTP) waveguide is described. The fully integrated photon-pair source consists of a 1064-nanometer pump diode laser, fiber-coupled to a dual element waveguide within which a pair of 1064-nanometer photons are up-converted to a single 532-nanometer photon in the first stage. In the second stage, the 532-nanometer photon is down-converted to an entangled photon-pair at 800 nanometer and 1600 nanometer which are fiber-coupled at the waveguide output. The photon-pair source features a high pair generation rate, a compact power-efficient package, and continuous wave (CW) or pulsed operation. This is a significant step towards the long term goal of developing sources for high-rate Quantum Key Distribution (QKD) to enable Earth-space secure communications. Characterization and test results are presented. Details and preliminary results of a laboratory free-space QKD experiment with the B92 protocol are also presented.

photons↗
NASA NTRS2016

Quantum Communication with a High-Rate Entangled Photon Source

A high generation rate photon-pair source using a dual element periodically-poled potassium titanyl phosphate (PP KTP) waveguide is described. The photon-pair source features a high pair generation rate, a compact power-efficient package, and continuous wave (CW) or pulsed operation. Characterization and test results are presented. Details and preliminary results of a laboratory free-space QKD experiment with the B92 protocol are also presented.

quantum key distribution↗
NASA NTRS2020

Ignition and Burn in a Hybrid Nuclear Fuel for a Pulsed Rocket Engine

This work explores the parameter space of a cylindrical hybrid nuclear fuel in support of a z-pinch driven pulsed fission-fusion (PuFF) engine. 0D power balance and 1D burn wave calculations have been performed to explore the parameter space of hybrid cylindrical nuclear fuels. The boundary of minimal initial conditions needed to reach breakeven are found within the context of the model. The effects of initial conditions upon the yield at the end of burn wave expansion are also determined. The model is used to examine the minimum initial energies predicted to result in yields of a few MJ. The goal of this work is to guide fuel design, inform future models and experiments as well as look for the most efficient parameter space for ignition in a z-pinch driven hybrid nuclear reaction. The impact of initial parameters upon ignition, burn, and gain are discussed. It is found that a hybrid cylindrical target may breakeven with initial energy near the axis of approximately 4 to 6 MJ in lithium deuteride/uranium 235 fuel. It is also found that magnetic field can lower the threshold further of which the magnitude changes across the parameter space. The dual fusion/fission reactions are found to boost each other leading to lower initial driving energies needed to reach breakeven in the hybrid cylindrical nuclear fuel.

fission↗
NASA NTRS2025

Laser Cutting of Anorthosite and Norite in Vacuum

Lasers have previously been evaluated to cut and drill through rock in high pressure and atmospheric conditions to support deep drilling for oil & gas, as well as breaking or cutting rock near the surface. This research evaluates using lasers to cut rocks in a lunar environment. Anorthosite and norite samples were cut in a rough vacuum (<1 Torr) environment using a continuous wave (CW) 2 kW laser. Power and cutting speed are varied to control the total power input. In total 30, 38mm cuts are performed with power levels ranging from 25% (525 W) to 100% (2100 W) and total energy inputs from 0.090 – 4.34 kJ/cm. The cuts are bisected and inspected with optical and scanning electron microscopy. The bisected areas are measured to determine the specific energy for material removal (J/mm 3 ) and the extent of the heat affected zone.

Laser Cutting↗
NASA NTRS1994

Screech tones from free and ducted supersonic jets

It is well known that screech tones from supersonic jets are generated by a feedback loop. The loop consists of three main components. They are the downstream propagating instability wave, the shock cell structure in the jet plume, and the feedback acoustic waves immediately outside the jet. Evidence will be presented to show that the screech frequency is largely controlled by the characteristics of the feedback acoustic waves. The feedback loop is driven by the instability wave of the jet. Thus the tone intensity and its occurrence are dictated by the characteristics of the instability wave. In this paper the dependence of the instability wave spectrum on the azimuthal mode number (axisymmetric or helical/flapping mode, etc.), the jet-to-ambient gas temperature ratio, and the jet Mach number are studied. The results of this study provide an explanation for the observed screech tone mode switch phenomenon (changing from axisymmetric to helical mode as Mach number increases) and the often-cited experimental observation that tone intensity reduces with increase in jet temperature. For ducted supersonic jets screech tones can also be generated by feedback loops formed by the coupling of normal duct modes to instability waves of the jet. The screech frequencies are dictated by the frequencies of the duct modes. Super resonance, resonance involving very large pressure oscillations, can occur when the feedback loop is powered by the most amplified instability wave. It is proposed that the observed large amplitude pressure fluctuations and tone in the test cells of Arnold Engineering Development Center were generated by super resonance. Estimated super-resonance frequency for a Mach 1.3 axisymmetric jet tested in the facility agrees well with measurement.

Tam, C. K. W.↗
NASA NTRS2002

Changes in gastric myoelectric activity during space flight

The purpose of the present study was to examine postprandial myoelectric activity of the stomach and gastric activity associated with space motion sickness using electrogastrography. Three crewmembers participated in this investigation. Preflight, subjects exhibited normal postprandial responses to the ingestion of a meal. Inflight, crewmembers exhibited an abnormal decrease in the power of the normal gastric slow wave after eating on flight day 1, but had a normal postprandial response by flight day 3. Prior to and during episodes of nausea and vomiting, the electrical activity of the stomach became dysrhythmic with 60-80% of the spectral power in the bradygastric and tachygastric frequency ranges. These findings indicate that gastric motility may be decreased during the first few days of space flight. In addition, changes in the frequency of the gastric slow wave associated with space motion sickness symptoms are consistent with those reported for laboratory-induced motion sickness.

STS Shuttle Project↗
NASA NTRS2002

Advances in Time-Distance Helioseismology

Time-distance helioseismology is a way to measure travel times between surface locations for waves traversing the solar interior. Coupling the travel with an extensive modeling effort has proven to be a powerful tool for measuring flows and other wave speed inhomogeneities in the solar interior. Problems receiving current attention include studying the time variation of the meridional circulation and torsional oscillation and active region emergence and evolution, current results on these topics will be presented.

Duvall, Thomas L., Jr.↗
NASA NTRS1972

Operating features of an ion-cyclotron-wave plasma apparatus running in the RF-sustained mode

An experimental study has been made of an ion-cyclotron-wave apparatus operated in the RF-sustained mode. This is a mode in which the Stix RF coil both propagates the waves and maintains the plasma. Problems associated with this method of operation are presented. Some factors that are important to the coupling of RF power are noted. In general, the wave-propagation and wave-damping data agree with theory. Some irregularities in wave fields are observed. Maximum ion temperature is 870 eV at a density of 5 times 10 to the 12th power per cubic centimeter and RF power of 90 kW. Coupling efficiency is 70 percent.

Swett, C. C.↗
NASA NTRS2002

Digital Distortion Caused by Traveling- Wave-Tube Amplifiers Simulated

Future NASA missions demand increased data rates in satellite communications for near real-time transmission of large volumes of remote data. Increased data rates necessitate higher order digital modulation schemes and larger system bandwidth, which place stricter requirements on the allowable distortion caused by the high-power amplifier, or the traveling-wave-tube amplifier (TWTA). In particular, intersymbol interference caused by the TWTA becomes a major consideration for accurate data detection at the receiver. Experimentally investigating the effects of the physical TWTA on intersymbol interference would be prohibitively expensive, as it would require manufacturing numerous amplifiers in addition to acquiring the required digital hardware. Thus, an accurate computational model is essential to predict the effects of the TWTA on system-level performance when a communication system is being designed with adequate digital integrity for high data rates. A fully three-dimensional, time-dependent, TWT interaction model has been developed using the electromagnetic particle-in-cell code MAFIA (Solution of Maxwell's equations by the Finite-Integration-Algorithm). It comprehensively takes into account the effects of frequency-dependent AM (amplitude modulation)/AM and AM/PM (phase modulation) conversion, gain and phase ripple due to reflections, drive-induced oscillations, harmonic generation, intermodulation products, and backward waves. This physics-based TWT model can be used to give a direct description of the effects of the nonlinear TWT on the operational signal as a function of the physical device. Users can define arbitrary excitation functions so that higher order modulated digital signals can be used as input and that computations can directly correlate intersymbol interference with TWT parameters. Standard practice involves using communication-system-level software packages, such as SPW, to predict if adequate signal detection will be achieved. These models use a nonlinear, black-box model to represent the TWTA. The models vary in complexity, but most make several assumptions regarding the operation of the high-power amplifier. When the MAFIA TWT interaction model was used, these assumptions were found to be in significant error. In addition, digital signal performance, including intersymbol interference, was compared using direct data input into the MAFIA model and using the system-level analysis tool SPW for several higher order modulation schemes. Results show significant differences in predicted degradation between SPW and MAFIA simulations, demonstrating the significance of the TWTA approximations made in the SPW model on digital signal performance. For example, a comparison of the SPW and MAFIA output constellation diagrams for a 16-ary quadrature amplitude modulation (16-QAM) signal (data shown only for second and fourth quadrants) is shown. The upper-bound degradation was calculated from the corresponding eye diagrams. In comparison to SPW simulations, the MAFIA data resulted in a 3.6-dB larger degradation.

Kory, Carol L.↗
NASA NTRS1985

Waves In Space Plasmas (WISP)

Waves in space plasmas (WISP) utilizes powerful radio transmitters and sensitive receivers to probe the secrets of the magnetosphere, ionosphere and atmosphere. The scientific objective is to achieve a better understanding of the physical processes occurring in these regions. For example, audio frequency radio waves will be radiated from the long WISP antenna, will travel to the outer reaches of the magnetosphere, and will interact with Van Allen belt particles, releasing some of their energy which amplifies the waves. Study of this interaction will give us a better understanding of a major magnetospheric process, wave particle interactions. Radio waves from WISP at higher frequencies (AM radio and beyond) will be reflected by the ionosphere and will, for example, advance our understanding of bubbles in the equatorial ionosphere which affect satellite communications.

Taylor, W. W. L.↗