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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Role of Intact Hydrogen-Bond Networks in Multiproton-Coupled Electron Transfer

The essential role of a well-defined hydrogen-bond network in achieving chemically reversible multiproton translocations triggered by one-electron electrochemical oxidation/reduction is investigated by using pyridylbenzimidazole–phenol models. The two molecular architectures designed for these studies differ with respect to the position of the N atom on the pyridyl ring. In one of the structures, a hydrogen-bond network extends uninterrupted across the molecule from the phenol to the pyridyl group. Experimental and theoretical evidence indicates that an overall chemically reversible two-protoncoupled electron-transfer process (E2PT) takes place upon electrochemical oxidation of the phenol. This E2PT process yields the pyridinium cation and is observed regardless of the cyclic voltammogram scan rate. In contrast, when the hydrogen-bond network is disrupted, as seen in the isomer, at high scan rates (~1000 mV s –1 ) a chemically reversible process is observed with an E 1/2 characteristic of a one-proton-coupled electron-transfer process (E1PT). At slow cyclic voltammetric scan rates (<1000 mV s –1 ) oxidation of the phenol results in an overall chemically irreversible two-proton-coupled electron-transfer process in which the second proton-transfer step yields the pyridinium cation detected by infrared spectroelectrochemistry. In this case, we postulate an initial intramolecular proton-coupled electron-transfer step yielding the E1PT product followed by a slow, likely intermolecular chemical step involving a second proton transfer to give the E2PT product. Insights into the electrochemical behavior of these systems are provided by theoretical calculations of the electrostatic potentials and electric fields at the site of the transferring protons for the forward and reverse processes. Furthermore, this work addresses a fundamental design principle for constructing molecular wires where protons are translocated over varied distances by a Grotthuss-type mechanism.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Strong-field QED limitations on TeV-class plasma wakefield accelerators

We demonstrate that quantum and classical radiation effects can become non-negligible for TeV-class beams propagating through plasma channels typical of staged plasma accelerators. Although the quantum nonlinearity parameter χ e remains small under currently envisioned experimental conditions, the cumulative influence of radiation over long acceleration distances can lead to significant modifications to the beam’s energy spread, emittance, and polarization. Our analytic models, validated by particle-in-cell simulations, highlight that for standard Gaussian beams, the orbit-induced energy spread dominates over quantum stochastic effects but can be mitigated by tailoring the beam profile, for example, through ring-shaped transverse distributions. In regimes where the radiation reaction approaches the accelerating force, the emittance may be cooled, forming distinctive ring-shaped phase-space structures. Finally, we analyze the influence of the radiation effect on spin transport inside the wakefield. These findings underscore the importance of considering both classical and quantum radiation dynamics in the design and optimization of future high-intensity plasma accelerators.

accelerator↗
DOE OSTI2023

WISDOM project – XVIII. Molecular gas distributions and kinematics of three megamaser galaxies

ABSTRACT The co-evolution of galaxies and supermassive black holes (SMBHs) underpins our understanding of galaxy evolution, but different methods to measure SMBH masses have only infrequently been cross-checked. We attempt to identify targets to cross-check two of the most accurate methods, megamaser, and cold molecular gas dynamics. Three promising galaxies are selected from all those with existing megamaser SMBH mass measurements. We present Atacama Large Millimeter/sub-millimeter Array (ALMA) 12CO (2–1) and 230-GHz continuum observations with angular resolutions of ≈0${_{.}^{\prime\prime}}$5. Every galaxy has an extended rotating molecular gas disc and 230-GHz continuum source(s), but all also have irregularities and/or non-axisymmetric features: NGC 1194 is highly inclined and has disturbed and lopsided central 12CO (2–1) emission; NGC 3393 has a nuclear disc with fairly regular but patchy 12CO (2–1) emission with little gas near the kinematic major axis, faint emission in the very centre, and two brighter structures reminiscent of a nuclear ring and/or spiral; NGC 5765B has a strong bar and very bright 12CO (2–1) emission concentrated along two bisymmetric offset dust lanes and two bisymmetric nuclear spiral arms. 12CO (2–1) and 12CO (3–2) observations with the James Clerk Maxwell Telescope are compared with the ALMA observations. Because of the disturbed gas kinematics and the impractically long integration times required for higher angular resolution observations, none of the three galaxies is suitable for a future SMBH mass measurement. None the less, increasing the number of molecular gas observations of megamaser galaxies is valuable, and the ubiquitous disturbances suggest a link between large-scale gas properties and the existence of megamasers.

Liang, Fu-Heng (ORCID:0000000324961247)↗
NASA NTRS1971

Shock transmission in coupled beams and rib stiffened structures

Shock transmission in a simple coupled beam structure and in a ring-stringer stiffened cylinder is investigated experimentally and analytically using wave transmission and statistical energy analysis concepts. The use of the response spectrum to characterize the excitation provided to a simple beam by a force pulse is studied. Analysis of the transmission of a dilatation wave in a periodically stiffened plate indicates that the stiffeners are fairly transparent to the wave, but some of the dilatational energy is scattered into bending at each support.

Pope, L. D.↗
NASA NTRS1974

Variable beamwidth monopulse feed for Tracking and Data Relay Satellite (TDRS)

The Tracking and Data Relay Satellite with a set of circularly-polarized, amplitude-sensing monopulse patterns suitable for acquiring and tracking user spacecraft at Ku-band (15.0 GHz) is discussed. The possibility of increasing the less than 0.4-degree half-power beamwidth of the data beam to almost 1.0 degree during the acquisition phase is predicated on the use of feeds situated in the first bright-ring of the Airy diffraction structure. A complex-vector simulation equivalent to the Kirchhoff-Kottler or Franz formulations is used to compute transmitted and received field information for a dual-reflector (Cassegrain) antenna configuration in a three-dimensional space.

Schmidt, R. F.↗
NASA NTRS1977

Planetary astronomy program

A program was developed in which asteroids and two planets, namely, Saturn and Uranus, were investigated. This included: (1) asteroid spectrophotometry; (2) the nature of the Trojan asteroids; (3) an investigation to determine asteroid masses; (4) the photometry, structure, and dynamics of the rings surrounding the planet Saturn; and (5) aerosol distribution in the atmosphere of Uranus. Plans were finalized to obtain observations of the nucleus of the dying comet P/Arend-Rigaux. Further work was accomplished in asteroid data reduction. Data were entered into the TRIAD data file and a program generated classifications for over 560 different asteroids. A photoelectric area scanner was used to obtain UBV scans of the disk of the planet Saturn on several winter and spring nights in 1977. Intensity profiles show pronounced limb brightening in U, moderate limb brightening in B, and limb darkening in V. Narrow band photoelectric area-scanning photometry of the Uranus disk is also reported. Results are given.

Source record↗
NASA NTRS1982

Marine applications of HCMM satellite data

Results of a limited comparison of HCMM sea surface temperature data with in situ data suggest that the HCMM data can provide a rather accurate representation of the sea surface temperature and temperature pattern. In the Nantucket Shoals region, the HCMM analysis provided data on the surface heating and on transport south of Nantucket Island and Nantucket Sound. The analyses also revealed the sea surface temperature structure of an anticyclonic warm ring.

Vukovich, F. M.↗
NASA NTRS1985

Particle and field stress balance within a planetary magnetosphere

A technique is developed for experimentally estimating the local tensor stresses within a planetary magnetic field configuration characterized by local spacecraft measurements. Key to the technique is the determination of the shapes of field lines using the symmetry properties of the system coupled with local and instantaneous measurements of the field line inclination angles. The technique is applied here to the inner and middle Saturnian magnetosphere using data returned by the Magnetic Field Experiment on the Voyager 1 spacecraft. It is concluded that the ring current has substantial radial structure, heretofore not shown. Outside about 13 R(s) the newly derived field stresses match remarkably well the funtional variation of the centrifugal corotation stresses of the cool particle population measured previously by the Plasma Science Experiment. Inside about 13 R(s) the key structure in the derived field stresses, a prominent local maximum, matches the approximate position of an apparent strong pressure gradient in the energetic particles characterized by the Low-Energy Charged Particle detectors.

Mauk, B. H.↗
NASA NTRS1986

Plasma universe

Traditionally the views on the cosmic environent have been based on observations in the visual octave of the electromagnetic spectrum, during the last half-century supplemented by infrared and radio observations. Space research has opened the full spectrum. Of special importance are the X-ray-gamma-ray regions, in which a number of unexpected phenomena have been discovered. Radiations in these regions are likely to originate mainly from magnetised cosmic plasmas. Such a medium may also emit synchrotron radiation which is observable in the radio region. If a model of the universe is based on the plasma phenomena mentioned it is found that the plasma universe is drastically different from the traditional visual universe. Information about the plasma universe can also be obtained by extrapolation of laboratory experiments and magnetospheric in situ measurements of plasmas. This approach is possible because it is likely that the basic properties of plasmas are the same everywhere. In order to test the usefulness of the plasma universe model it is applied to cosmogony. Such an approach seems to be rather successful. For example, the complicated structure of the Saturnian C ring can be accounted for. It is possible to reconstruct certain phenomena 4 to 5 billions of years ago with an accuracy of better than 1%.

Alfven, H.↗
NASA NTRS1987

Uranus

Observations and theoretical investigations of the Uranus (U) system from the period 1983-1986 are reviewed, with an emphasis on the Voyager 2 encounter with U on January 26, 1986. Topics addressed include the bulk U composition, structure, and heat flux; the U atmospheric composition, structure, and circulation; the U rings; the major and minor U satellites; the U magnetosphere; and the Lyman-alpha 'electroglow' observed on the sunlit hemisphere of U.

Bergstralh, Jay T.↗
NASA NTRS1988

Non-isothermal elastoviscoplastic analysis of planar curved beams

The development of a general mathematical model and solution methodologies, to examine the behavior of thin structural elements such as beams, rings, and arches, subjected to large nonisothermal elastoviscoplastic deformations is presented. Thus, geometric as well as material type nonlinearities of higher order are present in the analysis. For this purpose a complete true abinito rate theory of kinematics and kinetics for thin bodies, without any restriction on the magnitude of the transformation is presented. A previously formulated elasto-thermo-viscoplastic material constitutive law is employed in the analysis. The methodology is demonstrated through three different straight and curved beams problems.

Simitses, G. J.↗
NASA NTRS1988

A precision pointing system for space telescope class optical trackers

This paper reports on the results of a study effort whose main objective was to develop a conceptual design for a space based, large-payload (3000 kg) pointing system capable of both rapid slew maneuvers (0.35 rad/sec-squared) and very stable tracking (1 microrad, 1 sigma, each axis). The key features of the resulting solution are: (1) cross elevation over elevation gimbal system, (2) closed cross elevation gimbal ring, (3) graphite-epoxy structure, (4) two-motor reactionless joint torquers, (5) payload mounted vernier reaction wheel, and (6) gyrostabilized model following control system.

Sevaston, George E.↗
NASA NTRS1991

Planetary astronomy

The authors profile the field of astronomy, identify some of the key scientific questions that can be addressed during the decade of the 1990's, and recommend several facilities that are critically important for answering these questions. Scientific opportunities for the 1990' are discussed. Areas discussed include protoplanetary disks, an inventory of the solar system, primitive material in the solar system, the dynamics of planetary atmospheres, planetary rings and ring dynamics, the composition and structure of the atmospheres of giant planets, the volcanoes of IO, and the mineralogy of the Martian surface. Critical technology developments, proposed projects and facilities, and recommendations for research and facilities are discussed.

Morrison, David↗
NASA NTRS1990

Color maps of Arp 146

Four color maps of Arp 146 are given. The structure and color of the ring galaxy and its companion show evidence of a bridge of material between the companion and the remnant nucleus of the original galaxy now forming the ring. Broad band spatial coverage clearly defines regions of starburst occurrence.

Schultz, A. B.↗
NASA NTRS1992

Effects of low Earth orbit environment on the Long Duration Exposure Facility thermal control coatings

One of the benefits of the Long Duration Exposure Facility (LDEF) was the opportunity to study the before and after effects of low earth orbit space environment on the spacecraft thermal control coatings. Since the LDEF's thermal control was totally passive by design, the selection of the external surface absorptivity to emissivity ratio (alpha/epsilon) and the ability for the coating to retain the alpha/epsilon over time was an important consideration in the thermal design of the LDEF. The primary surface coating chosen for the LDEF structure was clear chromic anodized aluminum with an average design alpha/epsilon of 0.32/0.16. External surface absorptivity (alpha) and emissivity (epsilon) were measured on all intercostals, longerons, tray mounting flanges, thermal control panels, and a limited number of experiment surface coatings after the experiment trays were removed from the LDEF structure. All surface alpha/epsilon measurements were made using portable hand held infrared and solar spectrum reflectometers. The absorptivity measurements were taken with a Devices and Services SSR-ER version 5.0 solar spectra reflectometer which has a stated uncertainty of +/- 0.01, and all normal emissivity measurements were made using the Gier Dunkle DB-100 infrared reflectometer also with a stated uncertainty of +/- 0.01. Both instruments were calibrated in the laboratory by LaRC instrumentation personnel before being used in the field at KSC. A combined total of 733 measurements were taken on the anodized aluminum hardware which included the structure (intercostals, longerons, and center ring), earth and space end thermal control panels, and experiment tray mounting flanges. The facility thermal control coatings measured in this survey cover 33 percent of the total exposed LDEF surface area. To correlate low earth orbit environmental effects on the anodized coatings, measurements were taken in both exposed and unexposed surfaces and compared to quality assurance (QA) measurements taken on the new surfaces at the time of hardware fabrication in 1978. The results of investigation are presented.

Sampair, Thomas R.↗
NASA NTRS1996

Noise Reduction in an Aircraft Fuselage Model Using Active Trim Panels

An experiment was conducted to evaluate the use of force actuators on a model aircraft interior trim panel as the control element for active control of interior noise. The trim panel, designed specifically for this study, was constructed in three large identical sections and hard mounted to the ring frames of the primary structure. Piezoceramic actuators were bonded to the outer surface of the trim panels. Studies of the interior pressure response due to both the primary source alone and control sources alone were conducted as well as the control cases. A single acoustic loudspeaker, centered at the axial midpoint, generated the acoustic field to be controlled.

Silcox, Richard J.↗