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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

High spatial resolution atmospheric wind measurements with the edge technique

The edge technique is a new and powerful method for measuring small frequency shifts such as the Doppler shift of an atmospheric backscattered signal from a pulsed laser. The edge technique can be used for high spatial resolution, high accuracy ground and airborne wind measurements as well as high accuracy spaceborne wind measurements. We have recently made our first ground based wind measurements. These have a spatial resolution of 15 m and an accuracy of 25 cm/s and these measurements are presented in this paper. This is a unique capability and provides valuable information for studies of turbulent processes in the lower atmosphere. It could also be used for high sensitivity detection of wind shear and microbursts in the vicinity of airports. In addition, global wind measurements can be made with the edge technique from space with an accuracy of 1 m/s and a vertical resolution as high as 150 m in the boundary layer and 1 km through the troposphere. Such a system could make eyesafe wind measurements using well developed diode pumped solid state laser technology at 1.06 micron. Multi-pulse averaging would provide a spatially representative wind measurement.

Korb, C. Laurence↗
NASA NTRS1978

The solar probe and coronal dynamics

The discovery of coronal holes led to basic changes in ideas about the structure of the low corona and its expansion into the solar wind. The nature of the energy flux is not understood. Current ideas include enhanced thermal conductivities, extended MHD wave heating, and wave momentum transfer, all in rapidly diverging geometries. There is little feel for the relative importance of these processes. The Solar Probe, with its penetration deep into the solar corona, could lead to observational constraints on their relative importance, and thus to an understanding of the origin of the solar wind. Observations from the Solar Probe will also bear on such questions as to whether small scale "intrastream" structure is common close to the Sun in open field-line regions, whether the properties of the wind are pronouncedly different over closed and open field-line regions at five solar radii, and many others. The resolution of these questions requires measurements of the magnetic field and of the proton and electron distribution functions.

Belcher, J.↗
NASA NTRS1999

Atmospheric Dynamics of Venus: Scales Large and Small

Over the past 30 years, Gerald Schubert has made significant contributions to the understanding of Venus atmospheric dynamics. His research of Venus' atmosphere spans spatial scales both large and small, including: Venus westward atmospheric superrotation, Planetary scale waves and the global "Y" ultraviolet feature, Wind streaks and the global circulation of the lower atmosphere, Mesoscale convection in the clouds of Venus, Vertical propagation of small-scale internal gravity waves, and Interaction between small-scale dynamics and the large-scale mean flow. Furthermore, his role as Principal Investigator of the Pioneer Venus Working Group on Structure and Circulation in the late 1970's and early 1980's was instrumental in the advancement of our understanding of Venus' atmosphere. The Pioneer Venus work serves as the cornerstone of our view of Venus atmospheric dynamics today. This paper will review Jerry's extensive research on Venus' atmosphere. In addition, recent results on convectively generated internal gravity waves will be presented that combine his lifelong, interest in both large-scale and small-scale dynamics. It will be shown that small-scale internal gravity waves generated by convection within the clouds of Venus decelerate the westward superrotation below the clouds. Thus, mechanisms that support the Venus westward superrotation must overcome the influence of small-scale dynamics in the lower atmosphere.

Baker, R. David↗
NASA NTRS2023

Self-Similar Outflows at the Source of the Fast Solar Wind: A Smoking Gun of Multiscale Impulsive Reconnection?

We present results of a quantitative analysis of structured plasma outflows above a polar coronal hole observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) spacecraft. In a 6 hr interval of continuous high-cadence SDO/AIA images, we identified more than 2300 episodes of small-scale plasma flows in the polar corona. The mean upward flow speed measured by the surfing transform technique is estimated to be 122 ± 34 km s−1, which is comparable to the local sound speed. The typical recurrence period of the flow episodes is 10–30 minutes, and the mean duration and transverse size of each episode are about 3–5 minutes and 3–4 Mm, respectively. The largest identifiable episodes last for tens of minutes and reach widths up to 40 Mm. For the first time, we demonstrate that the polar coronal-hole outflows obey a family of power-law probability distributions characteristic of impulsive interchange magnetic reconnection. Turbulent photospheric driving may play a crucial role in releasing magnetically confined plasma onto open field. The estimated occurrence rate of the detected self-similar coronal outflows is sufficient for them to make a dominant contribution to the fast-wind mass and energy fluxes and to account for the wind's small-scale structure.

jets↗
NASA NTRS1990

Magnetically striped relativistic magnetohydrodynamic winds - The Crab Nebula revisited

Previous relativistic pair plasma MHD wind models of the Crab Nebula indicate that the ratio of the wind's Poynting flux to particle kinetic energy flux must be very small. However, many current theories of pulsar magnetospheres and pulsar observations suggest that the spin-down luminosity should be primarily electromagnetic in origin and outward transport. For an oblique rotator, the asymptotic wind magnetic field near the rotational equator should consist of stripes of alternating toroidal field. A simple model of an initially high-sigma striped MHD wind is developed which describes the reconnection annihilation of the opposite polarity stripes as the wind flows radially outward. The initially dominant Poynting flux is converted into particle thermal and directed kinetic energy well within the inner standing shock which terminates the superfast wind.

Coroniti, F. V.↗
NASA NTRS1980

Monitoring and control requirement definition study for Dispersed Storage and Generation (DSG). Volume 3, appendix B: State of the art, trends, and potential growth of selected DSG technologies

Present and future relatively small (30 MW) energy systems, such as solar thermal electric, photovoltaic, wind, fuel cell, storage battery, hydro, and cogeneration can help achieve national energy goals and can be dispersed throughout the distribution portion of an electric utility system. Based on current projections, it appears that dispersed storage and generation (DSG) electrical energy will comprise only a small portion, from 4 to 10 percent, of the national total by the end of this century. In general, the growth potential for DSG seems favorable in the long term because of finite fossil energy resources and increasing fuel prices. Recent trends, especially in the institutional and regulatory fields, favor greater use of the DSGs for the future.

Source record↗
NASA NTRS2013

Constraints on Decreases in Eta Carinae's Mass-loss from 3D Hydrodynamic Simulations of Its Binary Colliding Winds

Recent work suggests that the mass-loss rate of the primary star Eta-A in the massive colliding wind binary Eta Carinae dropped by a factor of 2-3 between 1999 and 2010. We present result from large- (+/- 1545 au) and small- (+/- 155 au) domain, 3D smoothed particle hydrodynamics (SPH) simulations of Eta Car's colliding winds for three Eta-A mass-loss rates ( (dot-M(sub Eta-A) = 2.4, 4.8 and 8.5 × 10(exp −4) M(solar)/ yr), investigating the effects on the dynamics of the binary wind-wind collision (WWC). These simulations include orbital motion, optically thin radiative cooling and radiative forces. We find that dot-M Eta-A greatly affects the time-dependent hydrodynamics at all spatial scales investigated. The simulations also show that the post-shock wind of the companion star Eta-B switches from the adiabatic to the radiative-cooling regime during periastron passage (Phi approx.= 0.985-1.02). This switchover starts later and ends earlier the lower the value of dot-M Eta-A and is caused by the encroachment of the wind of Eta-A into the acceleration zone of Eta-B's wind, plus radiative inhibition of Eta-B's wind by Eta-A. The SPH simulations together with 1D radiative transfer models of Eta-A's spectra reveal that a factor of 2 or more drop in dot-M EtaA should lead to substantial changes in numerous multiwavelength observables. Recent observations are not fully consistent with the model predictions, indicating that any drop in dot- M Eta-A was likely by a factor of approx. < 2 and occurred after 2004. We speculate that most of the recent observed changes in Eta Car are due to a small increase in the WWC opening angle that produces significant effects because our line of sight to the system lies close to the dense walls of the WWC zone. A modest decrease in dot-M Eta-A may be responsible, but changes in the wind/stellar parameter of Eta-B, while less likely, cannot yet be fully ruled out. We suggest observations during Eta-Car's next periastron in 2014 to further test for decreases in dot-M Eta-A. If dot-M Eta-A is declining and continues to do so, the 2014 X-ray minimum should be even shorter than that of 2009.

Eta Carinae↗
NASA NTRS1989

Discrete events and solar wind energization

Based on a multiple-magnetic-reconnection picture, an estimation of the energy flux suggests that small-scale EUV exploding events may contribute a significant amount of energy (of order of 100,000 erg/sq cm sec) to solar atmospheric heating and solar-wind acceleration. Most of the dissipated magnetic energy is converted into thermal energy and plasma turbulence. On a related aspect, a numerical study based on the nonlinear one-fluid hydrodynamic equations shows a self-smoothing effect, whereby a multistream structure of the solar wind formed near the sun can be gradually smoothed during its propagation through interplanetary space. This calculation gives support for the possible contribution of discrete energetic events to high-speed solar wind streams.

Yang, W.-H.↗
NASA NTRS1994

Simple atmospheric perturbation models for sonic-boom-signature distortion studies

Sonic-boom propagation from flight level to ground is influenced by wind and speed-of-sound variations resulting from temperature changes in both the mean atmospheric structure and small-scale perturbations. Meteorological behavior generally produces complex combinations of atmospheric perturbations in the form of turbulence, wind shears, up- and down-drafts and various wave behaviors. Differences between the speed of sound at the ground and at flight level will influence the threshold flight Mach number for which the sonic boom first reaches the ground as well as the width of the resulting sonic-boom carpet. Mean atmospheric temperature and wind structure as a function of altitude vary with location and time of year. These average properties of the atmosphere are well-documented and have been used in many sonic-boom propagation assessments. In contrast, smaller scale atmospheric perturbations are also known to modulate the shape and amplitude of sonic-boom signatures reaching the ground, but specific perturbation models have not been established for evaluating their effects on sonic-boom propagation. The purpose of this paper is to present simple examples of atmospheric vertical temperature gradients, wind shears, and wave motions that can guide preliminary assessments of nonturbulent atmospheric perturbation effects on sonic-boom propagation to the ground. The use of simple discrete atmospheric perturbation structures can facilitate the interpretation of the resulting sonic-boom propagation anomalies as well as intercomparisons among varied flight conditions and propagation models.

Ehernberger, L. J.↗
NASA NTRS1993

Superfluid turbulence

At low temperatures (below 5 Kelvin), helium is a liquid with a very low kinematic viscosity. It was proposed that wind tunnels could be built using liquid helium as the test fluid. The primary advantages of such wind tunnels would be a combination of large Reynolds numbers and a relatively small apparatus. It is hoped that this combination will allow the study of high Reynolds number flows in an academic setting. There are two basic types of liquid helium wind tunnels that can be built, corresponding to the two phases of liquid helium. The high temperature phase (between approximately 2 to 5 Kelvin) is called helium 1 and is a Navier-Stokes fluid. There are no unanswered scientific questions about the design or operation of a wind tunnel in the helium 1 phase. The low temperature phase (below approximately 2 Kelvin) of liquid helium is called helium 2. This is a quantum fluid, meaning that there are some properties of helium 2 which are directly due to quantum mechanical effects and which are not observed in Navier-Stokes fluids. The quantum effects that are relevant to this paper are: (1) helium 2 is well described as a superposition of two separate fluids called the superfluid and the normal fluid. The normal-fluid component is a Navier-Stokes fluid and the superfluid is an irrotational Euler fluid; and (2) circulation in the superfluid exists only in quantized vortex filaments. All quantized vortex filaments have identical circulations kappa and core size a. The objective of the research at CTR was to develop an understanding of the microscopic processes responsible for the observed Navier-Stokes behavior of helium 2 flows.

Samuels, David C.↗
NASA NTRSDate not supplied

Probing the Lower-Thermosphere-Ionosphere In-situ with Small Spacecraft

The LTI at Earth spans the altitude range of about 90km to 200km. These altitudes do not lendthemselves easily to exploration by neither balloons nor orbiting spacecraft. As a consequence,only few in-situ measurements from the region exist, provided by sounding rocket campaignsand a few low-dipping Atmospheric Explorer missions in the 1970s. This has left a critical needfor simultaneous and co-located measurements of comprehensive sets of physical parametersto characterize both the neutral and plasma constituents. Such observations with extensivecoverage in time and space are crucial to advancing our understanding of the energetics, dy-namics, and chemistry of this complex region of the Earth’s atmosphere. Not all observablesare accessible through remote sensing so novel approaches and technological solutions are calledfor to obtain the needed in-situ measurements.Over the last decade, small spacecraft systems have proven their capability to provide someof these observations. Miniaturized instruments for electric and magnetic fields as well as forplasma and neutral gas densities, composition, and winds have been developed and proven inspace along with a large number of small satellite systems. Huge progress is also seen in thedevelopment of small satellite technology in support of large constellations. This paper willreview some of the main developments and discuss their relevance and potential for explorationof the LTI.

Aeronomy↗
DOE OSTI2022

Aqueous organic flow batteries for sustainable energy storage

Aqueous Organic Redox Flow Batteries (RFBs) have the potential to address the large-scale need for storing electrical energy from intermittent sources like solar- and wind-based generation. Unlike metal-based redox systems, small organic molecules present the prospect of achieving sustainability, by being synthesizable from abundantly available carbon dioxide, water, nitrogen, sulfur, and renewable energy. This mini-review focuses on the progress and challenges in designing water-based RFBs based on small organic molecules that can address the requirements of large-scale energy storage. Further, much of the recent research in this area involves discovering new molecular architectures via computational screening, understanding degradation, and cell configurations to address the techno-economic challenges of extraordinary electrochemical durability, recyclability, low cost of precursor materials, and good solubility. Redox materials for the positive side of the cell are notably few. Future research must continue to focus on these techno-economic challenges through rapid materials discovery.

25 ENERGY STORAGE↗
NASA NTRS1973

Zonal drifts of irregularities imparted by meridional winds.

In a uniform ionosphere, meridional winds cause only meridional motions of irregularities. It is shown, however, that, if F-region irregularities are considered in a real ionosphere in which there is a highly conductive E-layer, zonal motions occur. During the day a substantial westward drift takes place, while at night the drift is eastward but smaller, owing to the much smaller E-layer conductivity. Thus, the effect of meridional winds is to impart a net westward drift to small irregularities in the ionization, provided such irregularities persist long enough.

Waldman, H.↗
NASA NTRS1973

Acoustic emission produced during burst tests of filament-wound bottles.

Acoustic emission was recorded during burst tests of filament-wound, composite pressure vessels. Organic and graphite fibers were tested, and two different epoxy resin systems were used: one with a low and another with a relatively high cure temperature. Acoustic emission was studied for the effects of different winding patterns, artificial flaws, winding-induced fiber fraying, different resins, and different fibers. Small effects produced in the vessels by changes in these variables were greatly magnified when they appeared as changes in acoustic emission. They would, in fact, be difficult or impossible to detect by other test means.

Hamstad, M. A.↗
NASA NTRS1975

A study of coronal structures in a non-magnetic star

Convective instability in the solar corona growth, especially linear growth, was studied. An investigation was also made of nonlinear instability development on a computer. The computer was used to follow a growing perturbation from a small local enhancement in the density of the solar wind to a large increase in the density which would look like one of the rays seen in the sun's corona.

Source record↗
NASA NTRS1979

Martian meteorology

Viking mission results concerning the structure and dynamics of the Martian atmosphere are reviewed. The large-scale variability of pressure, temperature, and zonally averaged wind at the Lander sites is described, and small-scale phenomena involving the boundary layer and internal gravity waves are discussed. Observational evidence for the existence of transient planetary-scale waves, forced quasi-stationary waves, and thermal tides on Mars is examined. Atmospheric dynamics and properties of dust storms are considered, with emphasis on dust properties and distribution, the time evolution of planetwide dust storms, and dust-storm genesis and decay. Attention is also given to the nature of past Martian climates, the sizes and composition of volatile reservoirs, and volatile escape from the atmosphere.

Leovy, C. B.↗
NASA NTRS1980

Laser angle measurement system

The design and fabrication of a laser angle measurement system is described. The instrument is a fringe counting interferometer that monitors the pitch attitude of a model in a wind tunnel. A laser source and detector are mounted above the mode. Interference fringes are generated by a small passive element on the model. The fringe count is accumulated and displayed by a processor in the wind tunnel control room. Optical and electrical schematics, system maintenance and operation procedures are included, and the results of a demonstration test are given.

Pond, C. R.↗
NASA NTRS1979

Solar cycle variations in IMF intensity

Annual averages of logarithms of hourly interplanetary magnetic field (IMF) intensities, obtained from geocentric spacecraft between November 1963 and December 1977, reveal the following solar cycle variation. For 2-3 years at each solar minimum period, the IMF intensity is depressed by 10-15% relative to its mean value realized during a broad 9-year period centered at solar maximum. No systematic variations occur during this 9-year period. The solar minimum decrease, although small in relation to variations in some other solar wind parameters, is both statistically and physically significant.

King, J. H.↗