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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Analysis of Properties of the North Polar Layered Deposits: THEMIS Data in Context of MGS Data

One of the many questions of Martian exploration is to uncover the history of Mars, through analysis of the polar layered deposits (PLD). Martian polar ice caps hold most of the exposed water on the surface on Mars and yet their history and physical processed involved in their formation are unclear. We will attempt to contribute to our knowledge of the composition and stratigraphy of the polar deposits. In this work we present the latest imaging data acquired by the Mars Odyssey THermal EMission Imaging System (THEMIS) and place it into context of the Mars Global Surveyor (MGS) data. THEMIS provides capabilities for imaging in both thermal IR and visible color wavelengths. These observations are affected by atmospheric scattering and topography. The Mars Orbiter Laser Altimeter (MOLA) and Thermal Emission Spectrometer (TES) instruments on board of the MGS spacecraft can provide context information for THEMIS data. Of particular interest are Mars Orbiter Camera (MOC) images, which provide high resolution data. We are primarily interested in the seasonal evolution of ice cap temperatures during the first northern summer of THEMIS observations. Morphology, stratigraphy and composition of the layered deposits can be addressed by THEMIS VIS color images, along with MOC high resolution data and MOLA Digital Elevation Models (DEM). This work is intentionally descriptive. Based on the knowledge obtained by the orbiting spacecraft and described here, we will attempt to expose major directions for modeling and further understanding of of the physical processes involved in the formation of the polar layered terrain 2 Available data 2.1 THEMIS IR The THEMIS IR camera has 10 bands from 6 to 15 m. Due to to signal-to-noise restrictions the most useful band for polar observations is band 9 (12.57 m ). Band 10 (14.88 m ) data can be used for atmospheric calibration. An example of seasonal evolution observed by the THEMIS IR subsystem is shown in Figure 1. We have projected all IR images, covering a small area near 86N and 90E into a polar stereographic projection and then sampled time dimension in order to look at temperature evolution over the course of the summer. We are plotting averaged temperature data over two 1km2 regions of interest: layered material inside the trough and the surface of the residual ice cap. High resolution THEMIS IR data allows us to distinguish properties of bulk of layered terrain and ice. We were not able yet to distinguish properties of individual layers.

A B Ivanov↗
NASA NTRS1984

Analysis of physical-chemical processes governing SSME internal fluid flows

The efforts to adapt CHAM's computational fluid dynamics code, PHOENICS, to the analysis of flow within the high pressure fuel turbopump (HPFTP) aft-platform seal cavity of the SSME are summarized. In particular, the special purpose PHOENICS satellite and ground station specifically formulated for this application are listed and described, and the preliminary results of the first part two-dimensional analyses are presented and discussed. Planned three-dimensional analyses are also briefly outlined. To further understand the mixing and combustion processes in the SSME fuelside preburners, a single oxygen-hydrogen jet element was investigated.

Singhal, A. K.↗
NASA NTRS1989

Comments on the observability of coronal variations

The observable variability of spectral lines in the soft X-ray and XUV region is discussed. Rapid variability of coronal emission, both in flaring and non-flaring structures, has been reported and is particularly prominent when high spatial resolution is available. Examination of the ionization and recombination time-scales for the formation and removal of ions with prominent solar emission lines shows that, even though ionization equilibrium generally prevails, the observable variability time-scales are often limited by these atomic processes, independent of the physical process which is causing the change in the solar atmosphere. Future observations of Mg X 609 A should be augmented by simultaneous observation at another wavelength, such as 63 A. In addition, with the ability to produce images in isolated spectral lines it becomes possible to select those for which rapid variability is observable, such as O VII, rather than lines which were selected on the basis of previous hardware constraints, such as O VIII.

Golub, L.↗
NASA NTRS1991

Electrification in winter storms and the analysis of thunderstorm overflight

The emergence of 24 hr operational lightning detection networks has led to the finding that positive lightning strokes, although still much fewer in number than the normal negative strokes, are present in summer and winter storms. Recent papers address the importance of understanding the meteorological conditions which lead to a dominance of one polarity of stroke over another; the appearance of positive strokes at the end of a storm appeared to presage the end-of-storm downdraft and subsidence leading to downburst activity. It is beginning to appear that positive strokes may be important meteorological indicators. Significant research accomplishments on the following topics are addressed: (1) a study to verify that the black boxes used in the lightning networks to detect both negative and positive strokes to ground were accurate; (2) the use of slow tails to determine the polarity of distant lightning; (3) lightning initiation in winter vs. summer storms; (4) the upgrade of sensors for the measurement of electric field signals associated with lightning; (5) the analysis of lightning flash records from storms between 40 and 125 km from the sensor; and (6) an interesting aspect of the initiation process which involves the physical processes driving the stepped leader. The focus of current research and future research plans are presented.

Brook, Marx↗
NASA NTRS2002

The Evolution of Interstellar Dust

The abundance, composition and site distribution of interstellar dust is determined by a large number of physical processes in the sources and the Interstellar Medium (ISM). In this talk, we will give an overview of the evolutionary processes that determine the physical properties of dust in the ISM.

Dwek, Dr. Eliahu↗
NASA NTRS2002

Self-Consistent Magnetosphere-Ionosphere Coupling and Associated Plasma Energization Processes

Magnetosphere-Ionosphere (MI) coupling and associated with this process electron and ion energization processes have interested scientists for decades and, in spite of experimental and theoretical research efforts, are still ones of the least well known dynamic processes in space plasma physics. The reason for this is that the numerous physical processes associated with MI coupling occur over multiple spatial lengths and temporal scales. One typical example of MI coupling is large scale ring current (RC) electrodynamic coupling that includes calculation of the magnetospheric electric field that is consistent with the ring current (RC) distribution. A general scheme for numerical simulation of such large-scale magnetosphere-ionosphere coupling processes has been presented earlier in many works. The mathematical formulation of these models are based on "modified frozen-in flux theorem" for an ensemble of adiabatically drifting particles in the magnetosphere. By tracking the flow of particles through the inner magnetosphere, the bounce-averaged phase space density of the hot ions and electrons can be reconstructed and the magnetospheric electric field can be calculated such that it is consistent with the particle distribution in the magnetosphere. The new a self-consistent ring current model has been developed that couples electron and ion magnetospheric dynamics with calculation of electric field. Two new features were taken into account in addition to the RC ions, we solve an electron kinetic equation in our model, self-consistently including these results in the solution. Second, using different analytical relationships, we calculate the height integrated ionospheric conductances as the function of precipitated high energy magnetospheric electrons and ions as produced by our model. This results in fundamental changes to the electric potential pattern in the inner magnetosphere, with a smaller Alfven boundary than previous potential formulations would predict but one consistent with recent satellite observations. This leads to deeper penetration of the plasma sheet ions and electrons into the inner magnetosphere and more effective ring current ions and electron energization.

Khazanov, G. V.↗
NASA NTRS1991

Plasma processes in the inner coma

The physical processes that determine the plasma behavior in the inner coma region of active comets are reviewed. Results of observations of the plasma and fields inside the cometopause of Comets Halley and Giacobini-Zinner by instruments on board several spacecraft are presented. Several plasma populations are found to exist in the inner coma. The characteristics of a particular population are largely determined by how far upstream the population was created. All particle populations in the inner coma are strongly affected by collisional processes, such as charge-transfer, ion-neutral chemistry, ion-neutral friction, and thermal cooling. Plasma processes, in the form of magnetohydrodynamics, are also important in the inner coma.

Cravens, T. E.↗
NASA NTRS2002

Convective Systems during the South China Sea Monsoon Onset and Post-Onset Simulated by a Cloud Resolving Model Using SCSMEX Data

South China Sea Monsoon Experiment (SCSMEX, 1998), one of several major TRMM field experiments, has successfully obtained a wealth of information and observational data on the summer monsoon onset and evolution in the South China Sea region. The primary goal of the experiment is to provide a better understanding of the key physical processes for the onset and maintenance of the monsoon over Southeast Asia and southern China leading to improved predictions. In this paper, our objective is to investigate the major physical and microphysical processes involved in the convective systems that developed during the onset and post-onset of the South China Sea monsoon - for both the similarities and differences between these two phases. There are two episodes simulated in this study, one of the onset period (May 18-26, 1998) and one of the post-onset period (June 2-11, 1998). The focus of this paper is to study four major aspects between these two different episodes. First, characteristics of rainfall such as rainfall amount and occurrence in the convective and stratiform regions are investigated, as well as the propagation of convective systems. The numerical precipitation fields are also validated against both the TRMM Microwave Imager (TMI) soundings and Precipitation Radar (PR) observations. Second, the domain-averaged heat and moisture budgets are analyzed to comprehend the essential roles played by physical processes such as the large-scale forcing and latent heat flux. Third, the microphysical processes associated with warm rain or ice are also closely examined during these two episodes. Finally, vertical distributions of Q1 and Q2 budgets are presented to perform a detailed discussion on the energy and moisture cascade in the vertical direction.

Shie, C.-L.↗
NASA NTRS2016

Aerosol Complexity and Implications for Predictability and Short-Term Forecasting

There are clear NWP and climate impacts from including aerosol radiative and cloud interactions. Changes in dynamics and cloud fields affect aerosol lifecycle, plume height, long-range transport, overall forcing of the climate system, etc. Inclusion of aerosols in NWP systems has benefit to surface field biases (e.g., T2m, U10m). Including aerosol affects has impact on analysis increments and can have statistically significant impacts on, e.g., tropical cyclogenesis. Above points are made especially with respect to aerosol radiative interactions, but aerosol-cloud interaction is a bigger signal on the global system. Many of these impacts are realized even in models with relatively simple (bulk) aerosol schemes (approx.10 -20 tracers). Simple schemes though imply simple representation of aerosol absorption and importantly for aerosol-cloud interaction particle-size distribution. Even so, more complex schemes exhibit a lot of diversity between different models, with issues such as size selection both for emitted particles and for modes. Prospects for complex sectional schemes to tune modal (and even bulk) schemes toward better selection of size representation. I think this is a ripe topic for more research -Systematic documentation of benefits of no vs. climatological vs. interactive (direct and then direct+indirect) aerosols. Document aerosol impact on analysis increments, inclusion in NWP data assimilation operator -Further refinement of baseline assumptions in model design (e.g., absorption, particle size distribution). Did not get into model resolution and interplay of other physical processes with aerosols (e.g., moist physics, obviously important), chemistry

Predictability↗
NASA NTRS1981

Solar Corona Explorer: A mission for the physical diagnosis of the solar corona

Mission objectives and spacecraft requirements for the Solar Corona Explorer (SCE), a proposed free flying, unmanned solar research craft to be tenatively launched in 1987, were defined. The SCE's purpose is to investigate structure, dynamics and evolution of the corona, globally and in the required physical detail, to study the close coupling between the inner corona and the heliosphere. Investigative objectives are: (1) to understand the corona as the source of varying interplanetary plasma and of varying solar X-ray and extreme ultraviolet fluxes; (2) to develop the capabilities to model the corona with sufficient precision to forecast the Earth's variable environment in space, on the scales from weeks to years; (3) to develop an understanding of the physical processes that determine the dynamics and physical state of the coronal plasma, particularly acceleration processes; and (4) to develop insight and test theory on the Sun applicable to stellar coronae and winds, and in particular, to understand why cool stars put such a large fraction of their energy into X-rays. Considered related factors are: (1) duration of the mission; (2) onboard measuring instrumentation; (3) ground support equipment and procedures; and (4) programs of interpretation and modeling.

Source record↗
NASA NTRS2011

Model-Based Diagnostics for Propellant Loading Systems

The loading of spacecraft propellants is a complex, risky operation. Therefore, diagnostic solutions are necessary to quickly identify when a fault occurs, so that recovery actions can be taken or an abort procedure can be initiated. Model-based diagnosis solutions, established using an in-depth analysis and understanding of the underlying physical processes, offer the advanced capability to quickly detect and isolate faults, identify their severity, and predict their effects on system performance. We develop a physics-based model of a cryogenic propellant loading system, which describes the complex dynamics of liquid hydrogen filling from a storage tank to an external vehicle tank, as well as the influence of different faults on this process. The model takes into account the main physical processes such as highly nonequilibrium condensation and evaporation of the hydrogen vapor, pressurization, and also the dynamics of liquid hydrogen and vapor flows inside the system in the presence of helium gas. Since the model incorporates multiple faults in the system, it provides a suitable framework for model-based diagnostics and prognostics algorithms. Using this model, we analyze the effects of faults on the system, derive symbolic fault signatures for the purposes of fault isolation, and perform fault identification using a particle filter approach. We demonstrate the detection, isolation, and identification of a number of faults using simulation-based experiments.

Daigle, Matthew John↗
NASA NTRS1982

Rayleigh, Raman and particulate scattering

Analysis of the visible and near infrared spectra of planetary atmospheres and the multiple scattering of photons within the atmosphere are discussed. Photons detected within the spectral region are solar photons which were scattered by the gas and particles in the planetary atmosphere. An example is given for the incident and emitted fluxes for a hypothetical planet with an effective temperature of 100 K. The absorption spectrum of the planetary atmosphere is discussed in terms of the various scattering processes photons undergo within the atmosphere. Three different physical processes are considered. Rayleigh scattering and Raman scattering by the gas molecules, and scattering by any cloud or dust aerosol particles in the atmosphere. The physics of each of these processes is examined.

Cochran, W. D.↗
NASA NTRS1987

NASA's solar maximum mission: A look at a new Sun

As part of the ongoing process of trying to understand the physical processes at work in the Sun, the Solar Maximum Mission (SMM) spacecraft was launched on February 14, 1980, near the height of the solar cycle, to enable the solar physics community to examine, in more physically meaningful detail than ever before, the most violent aspect of solar activity: flares. The scientific products of SMM are substantial: by 1986, over 400 papers based on SMM observations and their interpretations had appeared in scientific journals. More important than such numerical measures of success is the significance of the science that has come from SMM. The following topics, the Sun as a star, solar flares, and the active solar atmosphere, as well as other findings of SMM investigators are described. The instruments on the SMM are also described.

Gurman, Joseph B.↗
NASA NTRS2023

Assessment of Oceanographic Conditions during the North Atlantic EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) Field Campaign

This manuscript presents an overview of NASA’s EXport Processes in the Ocean from Remote Sensing 2021 Field Campaign in the North Atlantic (EXPORTS NA) and provides quantitative and dynamical descriptions of the physical processes modulating water transformations during the study. A major programmatic goal was to conduct the sampling in a Lagrangian mode so that ocean ecological and biogeochemical changes can be observed independent from physical advective processes. To accomplish this goal, EXPORTS NA conducted a multi-ship, multi-asset field sampling program within a retentive, anticyclonic mode water eddy. Beneath depths of ∼100 m, Lagrangian sampling assets remained within the eddy core waters (ECWs) throughout the experiment, demonstrating that the ECWs within the mode water eddy were retentive. However, strong westerly winds from four storm events deepened the mixed layer (ML) of the surface core waters (SCWs) above the eddy’s mode water core by 25-40 m and exchanged some of the SCWs with surface waters outside of the eddy via Ekman transport. Estimates of flushing times ranged from 5-8 days, with surface exchange fractions ranging from 20-75% and were consistent with particle tracking advected by combined geostrophic and Ekman velocities. The relative contributions of horizontal and vertical advection on changes in ECW tracers depended on the horizontal and vertical gradients of that tracer. For example, horizontal advection played a large role in ECW salinity fluxes, while vertical entrainment played a larger role in the fluxes of nutrients into SCW ML. Each storm injected nutrients and low oxygen waters into the ML, after which the surface ocean ecosystem responded by reducing nutrient concentrations and increasing %O2 saturation levels. Overall, ECW values of chlorophyll and POC were the largest at the onset of the field program and decreased throughout the campaign. The analysis presented provides a physical oceanographic context for the many measurements made during the EXPORTS NA field campaign while illustrating the many challenges of conducting a production-flux experiment, even in a Lagrangian frame, and the inherent uncertainties of interpreting biological carbon pump observations that were collected in a Eulerian frame of reference.

oceanography↗