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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Effects of Atmospheric Dust on Residual South Polar Cap Stability

The Martian polar caps have been studied from the time of Herschel. Neither polar cap normally disappears in summer. The Residual North Polar Cap (portion that remains through summer) is composed of a mixture of water ice and dust, and its interannual stability is due to its low sublimation rate at the summer temperatures in the North Polar Region. The Residual South Polar Cap (RSPC) is more enigmatic, surviving the relatively hot perihelic summer season despite being composed of much more volatile CO2. It is able to do so because of its unusually high albedo, which is larger than that of other bright regions in the seasonal cap (e.g. Mountains of Mitchel). The proximity of the albedo of the RSPC to the critical albedo for stability raises the question of whether the RSPC exists in every Martian year. The ground based record is somewhat ambivalent. Douglass and Lowell reported that RSPC suddenly vanished at Ls=297deg in 1894 and did not reappear until Ls=0deg [1], and Kuiper reported that it disappeared in 1956 [2]; but both observations were questioned by contemporaries, who tended to attribute them to obscuring dust. Barker [3] reported a large amount of water vapor over the south polar cap in 1969 that could be attributed to exposure of near surface water ice during partial removal of the CO2 in the RSPC in 1969.

Bonrv, B. P.↗
NASA NTRS1988

Vertical distribution of dimethylsulfide, sulfur dioxide, aerosol ions, and radon over the northeast Pacific Ocean

The vertical distributions, in temperate latitudes, of dimethylsulfide (DMS), SO2, radon, methanesulfonate (MSA), nonsea-salt sulfate (nss-sulfate), and aerosol Na(+), NH4(+), and NO(-) ions were determined in samples collected by an aircraft over the northeast Pacific Ocean during May 3-12, 1985. DMS was also determined in surface seawater. It was found that DMS concentrations, both in seawater and in the atmospheric boundary layer, were significantly lower than the values reported previously for subtropical and tropical regions, reflecting the seasonal variability in the temperate North Pacific. The vertical profiles of DMS, MSA, SO2, and nss-sulfate were found to be strongly dependent on the convective stability of the atmosphere and on air mass origin. Biogenic sulfur emissions could account for most of the sulfur budget in the boundary layer, while the long-range transport of continentally derived air masses was mainly responsible for the elevated levels of both SO2 and nss-sulfate in the free troposphere.

Andreae, M. O.↗
NASA NTRS1976

Martian atmospheric lee waves

Areas of extensive mountain lee wave phenomenon in the northern midlatitudes during late winter are observed in Mariner 9 television pictures of Mars. The lee wave pattern is due to the discrete spectrum of waves generated by a crater ridge in an airstream. The cloud patterns resulting from the waves generated by the flow across a mountain or crater are dependent on the velocity profile of the airstream and the vertical stability of the atmosphere. A two-layer velocity model of the airstream is used in calculations based on the theory of mountain lee waves. Regardless of the simple model used for the airstream, the calculations appear to be capable of reproducing the observed wave patterns. The many observations of lee waves suggest that the near surface wind speeds as implied by the lower stream velocities do not greatly exceed, and most of the time are less than, 40 m/sec in the northern midlatitudes during late winter except possibly on a very localized scale. Results are in agreement with circulation models, especially the Leovy and Mintz (1969) two-layer numerical model.

Pirraglia, J. A.↗
NASA NTRS1990

Climate change and the middle atmosphere. I - The doubled CO2 climate

The effect of doubling the atmospheric content of CO2 on the middle-atmosphere climate is investigated using the GISS global climate model. In the standard experiment, the CO2 concentration is doubled both in the stratosphere and troposphere, and the SSTs are increased to match those of the doubled CO2 run of the GISS model. Results show that the doubling of CO2 leads to higher temperatures in the troposphere, and lower temperatures in the stratosphere, with a net result being a decrease of static stability for the atmosphere as a whole. The middle atmosphere dynamical differences found were on the order of 10-20 percent of the model values for the current climate. These differences, along with the calculated temperature differences of up to about 10 C, may have a significant impact on the chemistry of the future atmosphere, including that of stratospheric ozone, the polar ozone 'hole', and basic atmospheric composition.

Rind, D.↗
NASA NTRS1992

Measurement of the O-18 to O-16 isotope ratio for characterizing oxide surface layers on LDEF samples

The ratio of the density of the oxygen 18 isotope (O-18) to the density of the oxygen 16 isotope (O-16) is a strong function of altitude in the atmosphere because of the stronger gravitational attraction on the heavier isotope. It is proposed that the measurement of this ratio for oxide surface layers on LDEF samples can easily distinguish oxides formed in orbit from contaminative oxides formed during retrieval procedures. Since the satellite altitude is known as a function of time, it may be possible to use the measured ratio to determine the time of formation of oxide layers, the accuracy depending upon the stability of the atmosphere.

Sagalyn, Paul L.↗
NASA NTRS2003

Seasonal/Diurnal Mapping of Ozone and Water in the Martian Atmosphere

Ozone and water are key species for understanding the stability and evolution of Mars atmosphere; they are closely linked (along with CO, H, OH, and O) through photochemistry. Photolysis of water produces the OH radical (thought to catalyze reformation of CO2 from CO and O2) and atomic hydrogen (which reacts with O3 forming OH and O2). Atomic hydrogen also reacts with O2 (forming HO2), thereby reducing the amount of O2 available to reform O3 from collisions between O and O2. Hence ozone and water should be anti-correlated on Mars. Photolysis of O3 produces O2(a(sup 1) delta g) with 90% efficiency, and the resulting emission band system near 1.27 mm traces the presence and abundance of ozone. This approach was initially used to study ozone on Earth and then applied to Mars. In 1997, we measured several lines of the O2(a(sup 1) delta g) emission using CSHELL at the NASA IRTF; the O2(a(sup 1) delta g) state is also quenched by collisions with CO2. This quenching dominates at lower altitudes so that the detected emissions are used to detect ozone column densities above ~20 km. The slit was positioned N-S along Mars' central meridian resulting in a one-dimensional map of ozone. Nearly simultaneous maps may be made of water using CSHELL by detecting the v1 fundamental band of HDO near 3.67 microns and using the D/H ratio for Mars. This technique was used by DiSanti and Mumma. With CSHELL, measurements for both O2(a(sup 1) delta g) emissions and HDO absorptions can be made during the day or night. Since January, 1997, we have repeated these measurements at different times during the Martian year. For all of these dates, we have positioned the slit N-S along the central meridian; for some of these dates, we have also stepped the slit across the planet at 1 arc-sec intervals generating a 2-dimensional map. We have also positioned the slit E-W on Mars thus providing diurnal variations of ozone and water along the slit.

Novak, R. E.↗
NASA NTRS2006

Aerocapture Systems Analysis for a Neptune Mission

A Systems Analysis was completed to determine the feasibility, benefit and risk of an aeroshell aerocapture system for Neptune and to identify technology gaps and technology performance goals. The systems analysis includes the following disciplines: science; mission design; aeroshell configuration; interplanetary navigation analyses; atmosphere modeling; computational fluid dynamics for aerodynamic performance and aeroheating environment; stability analyses; guidance development; atmospheric flight simulation; thermal protection system design; mass properties; structures; spacecraft design and packaging; and mass sensitivities. Results show that aerocapture is feasible and performance is adequate for the Neptune mission. Aerocapture can deliver 1.4 times more mass to Neptune orbit than an all-propulsive system for the same launch vehicle and results in a 3-4 year reduction in trip time compared to all-propulsive systems. Enabling technologies for this mission include TPS manufacturing; and aerothermodynamic methods for determining coupled 3-D convection, radiation and ablation aeroheating rates and loads.

Lockwood, Mary Kae↗
NASA NTRS1997

The Onset of the Madden-Julian Oscillation Within an Aquaplanet Model

A series of numerical experiments using a two-level atmospheric general circulation model (AGCM) were performed for the purpose of investigating the coupling between sea surface temperature (SST) profile and the onset of the Madden-Julian Oscillation (MJO). The AGCM was modified to run as an aquaplane with all seasonal forcing removed. SST distributions based on the New Global Sea-Ice and Sea Surface Temperature (GISST) Data Set for 1903-1994 were generated then modified to vary the north-south gradient and tropical temperatures. It was found that the MJO signal did not depend on the SST temperature gradients but rather on the absolute temperature of the equatorial region, EOF analysis revealed that the SST distribution which generated the strongest MJO signal produced a periodic fluctuation in velocity potential at the 250 millibar level with a phase speed of 15 m/s, and a periodicity of 30 days which falls within the shortest limit of observed oscillations. This distribution also possessed the coolest equatorial SSTs which suggests that increased stability in the atmosphere favors the occurrence of organized MJO propagation.

Colon, Edward↗
NASA NTRS1972

Spectrocopic measurements of water vapor plasmas at high resolution: The optical transition probabilities for OH (A 2 Sigma - X 2 Pi)

Emission and absorption spectra of water vapor plasmas generated in a wall-stabilized arc at atmospheric pressure and 4 current, and at 0.03 atm and 15 to 50 A, were measured at high spatial and spectral resolution. The gas temperature was determined from the shape of Doppler-broadened rotational lines of OH. The observed nonequilibrium population distributions over the energy levels of atoms are interpreted in terms of a theoretical state model for diffusion-controlled arc plasmas. Excellent correlation is achieved between measured and predicted occupation of hydrogen energy levels. It is shown that the population distribution over the nonpredissociating rotational-vibrational levels of the A 2 Sigma state of OH is close to an equilibrium distribution at the gas temperature, although the total density of this state is much higher than its equilibrium density. The reduced intensities of the rotational lines originating in these levels yielded Boltzmann plots that were strictly linear.

Klein, L.↗
NASA NTRS1975

Satellite laser ranging work at the Goddard Space Flight Center

The paper describes the satellite laser ranging system at the Goddard Space Flight Center, its range and accuracy capabilities, and planned improvements for future systems. Major subsystems are described, including the laser, optical/mechanical, receiver, computer/software, timing, and laser data preprocessing subsystems. Operational considerations are examined, with attention given the mobile station layout, manpower requirements, and transportability. System performance is considered, with emphasis on system accuracy (calibration, stability, clock synchronization, atmospheric propagation correction) and range capability.

Mcgunigal, T. E.↗
NASA NTRS1983

Interpretation of MST radar returns from clear air

The nature of the scattering and reflection mechanisms that give rise to the MST radar echoes from the clear air is essential in the correct interpretation of the data about winds, waves, turbulence and stability in the atmosphere. There are two main aspects: the nature of the targets the radar sees and their generation mechanisms; and the signatures of the radar signals returned from the different targets. Volume scatterings from isotropic or anisotropic turbulence, and partial reflections from horizontally stratified, sharp refractive index gradients are believed the main contributors to radar echoes. Combined effects from all the mechanisms probably produce the observed data. The signature of the echo signals for these different scatterers under realistic experimental conditions should be studied. It is hoped from these studies, the nature of the targets can be better understood, and related to atmospheric dynamic processes.

Liu, C. H.↗
NASA NTRS1984

Participation in the Mars data analysis program: Global and regional studies of wind-indicators on the surface of Mars

Global and regional patterns on Mars were inferred from surface aeolian features, such as wind streaks and dune deposits, which were visible in Viking Orbiter images. Precise measurements of the dimensions of topographic obstacles, i.e., craters, hills, ridges, on Mars as well as their associated wind streaks were used to determine the aerodynamic shape of an obstacle affects near surface airflow. A classification of Martian wind streaks was developed on the basis of albedo contrast and the presence or absence of either topographic obstacles or sediment deposits at the point of origin of the wind streaks. It was concluded that local meteorological conditions, such as the stability of the atmospheric boundary layer, play a major role in determining why some Martian craters produce depositional wind streaks while others produce erosional ones.

Veverka, J.↗
NASA NTRS1984

Global variation of the para hydrogen fraction in Jupiter's atmosphere and implications for dynamics on the outer planets

A detailed analysis of the Voyager infrared spectrometer measurements on Jupiter's atmosphere is presented, and possible implications of para hydrogen disequilibrium for the energetics and dynamics of that atmosphere are examined. The method of data analysis is described, and results for the large scale latitude variation of the para hydrogen fraction are presented. The Jovian results show pronounced latitude variation, and are compared with other parameters including wind fields, thermal structure, and various indicators of atmospheric clouds. The problem of equilibration rate is reexamined, and it is concluded that on Jupiter the equilibration time is longer than the radiative time constant at the level of emission to space, but that this inequality reverses at greater depths. A model for the interaction of fluid motions with the ortho-para conversion process is presented, and a consistent mixing length theory for the reacting ortho-para mixture is developed. Several implications of the Jovian data for atmospheric energetics and stability on the outer planets are presented.

Conrath, B. J.↗
NASA NTRS1990

Climate and smoke - An appraisal of nuclear winter

A reevaluation is presented of the 'nuclear winter' scenario of Turco et al. (1983). New pertinent data have emerged from laboratory studies, field experiments, and numerical models on the smoke-plume, mesoscale, and global scales. A full-scale nuclear exchange's probable soot injections lead, in three-dimensional climate simulations, to midsummer land temperature decreases averaging 10-20 C in northern midlatitudes, with local cooling of as much as 35 C. Anomalous circulation patterns due to solar heating of the soot could stabilize the upper atmosphere against overturning, thereby prolonging the soot's residence time in the atmosphere. Monsoon disruptions and severe ozone layer depletion are also foreseen.

Turco, R. P.↗
NASA NTRS1999

Modeled Impact of Cirrus Cloud Increases Along Aircraft Flight Paths

The potential impact of contrails and alterations in the lifetime of background cirrus due to subsonic airplane water and aerosol emissions has been investigated in a set of experiments using the GISS GCM connected to a q-flux ocean. Cirrus clouds at a height of 12-15km, with an optical thickness of 0.33, were input to the model "x" percentage of clear-sky occasions along subsonic aircraft flight paths, where x is varied from .05% to 6%. Two types of experiments were performed: one with the percentage cirrus cloud increase independent of flight density, as long as a certain minimum density was exceeded; the other with the percentage related to the density of fuel expenditure. The overall climate impact was similar with the two approaches, due to the feedbacks of the climate system. Fifty years were run for eight such experiments, with the following conclusions based on the stable results from years 30-50 for each. The experiments show that adding cirrus to the upper troposphere results in a stabilization of the atmosphere, which leads to some decrease in cloud cover at levels below the insertion altitude. Considering then the total effect on upper level cloud cover (above 5 km altitude), the equilibrium global mean temperature response shows that altering high level clouds by 1% changes the global mean temperature by 0.43C. The response is highly linear (linear correlation coefficient of 0.996) for high cloud cover changes between 0. 1% and 5%. The effect is amplified in the Northern Hemisphere, more so with greater cloud cover change. The temperature effect maximizes around 10 km (at greater than 40C warming with a 4.8% increase in upper level clouds), again more so with greater warming. The high cloud cover change shows the flight path influence most clearly with the smallest warming magnitudes; with greater warming, the model feedbacks introduce a strong tropical response. Similarly, the surface temperature response is dominated by the feedbacks, and shows little geographical relationship to the high cloud input. Considering whether these effects would be observable, changing upper level cloud cover by as little as 0.4% produces warming greater than 2 standard deviations in the Microwave Sounding Unit (MSU) channels 4, 2 and 2r, in flight path regions and in the subtropics. Despite the simplified nature of these experiments, the results emphasize the sensitivity of the modeled climate to high level cloud cover changes, and thus the potential ability of aircraft to influence climate by altering clouds in the upper troposphere.

Rind, David↗
NASA NTRS1965

Review of the XB-70 Flight Program

Although the major NASA research effort is directed toward XB-70-2, which will not enter its flight program until the summer of 1965, a limited amount of information is available from the early flights of the XB-70-1 airplane. Initial take-off and landing performance data have generally substantiated predictions and indicate no unforeseen problems for this class of vehicle. Vertical velocities at impact are of the same order of magnitude as those being experienced by present-day subsonic jets. The XB-70 distances from brake release to lift-off graphically illustrate the advantage of the increased thrust-weight ratio of the supersonic cruise vehicle. The landing loads are well within the design limits up to the highest vertical velocities encountered to date, and recorded data show the response at the pilot station to be somewhat greater than that recorded at the center of gravity. Persistent shaking has been encountered in flight at subsonic speed. The cause of the excitation is not known at present but the oscillation does not appear to be conventional buffeting. The oscillation occurrence drops off appreciably at supersonic speeds and can be correlated with atmospheric turbulence. The stability and control characteristics at subsonic speeds appear satisfactory with stability augmentation on and off. A longitudinal trim discrepancy from predictions has been noted in the transonic region which appears to be decreasing with increasing supersonic speed. The supersonic handling qualities are considered adequate with stability augmentation off; however, sensitive lateral control has resulted in small pilot-induced oscillations.

Thomas R. Sisk↗
NASA NTRS2002

Urban Surface Radiative Energy Budgets Determined Using Aircraft Scanner Data

It is estimated that by the year 2025, 80% of the world's population will live in cities. The extent of these urban areas across the world can be seen in an image of city lights from the Defense Meteorological Satellite Program. In many areas of North America and Europe, it is difficult to separate individual cities because of the dramatic growth and sprawl of urbanized areas. This conversion of the natural landscape vegetation into man-made urban structures such as roads and buildings drastically alter the regional surface energy budgets, hydrology, precipitation patterns, and meteorology. One of the earliest recognized and measured phenomena of urbanization is the urban heat island (UHI) which was reported as early as 1833 for London and 1862 for Paris. The urban heat island results from the energy that is absorbed by man-made materials during the day and is released at night resulting in the heating of the air within the urban area. The magnitude of the air temperature difference between the urban and surrounding countryside is highly dependent on the structure of the urban area, amount of solar immolation received during the day, and atmospheric conditions during the night. These night time air temperature differences can be in the range of 2 to 5 C. or greater. Although day time air temperature differences between urban areas and the countryside exists during the day, atmospheric mixing and stability reduce the magnitude. This phenomena is not limited to large urban areas, but also occurs in smaller metropolitan areas. The UHI has significant impacts on the urban air quality, meteorology, energy use, and human health. The UPI can be mitigated through increasing the amount of vegetation and modification of urban surfaces using high albedo materials for roofs and paved surfaces. To understand why the urban heat island phenomenon exists it is useful to define the surface in terms of the surface energy budget. Surface temperature and albedo is a major component of the surface energy budget. Knowledge of it is important in any attempt to describe the radiative and mass fluxes which occur at the surface. Use of energy terms in modeling surface energy budgets allows the direct comparison of various land surfaces encountered in a urban landscape, from vegetated (forest and herbaceous) to non-vegetated (bare soil, roads, and buildings). These terms are also easily measured using remote sensing from aircraft or satellite platforms allowing one to examine the spacial variability. The partitioning of energy budget terms depends on the surface type. In natural landscapes, the partitioning is dependent on canopy biomass, leaf area index, aerodynamic roughness, and moisture status, all of which are influenced by the development stage of the ecosystem. In urban landscapes, coverage by man-made materials substantially alters the surface face energy budget. The remotely sensed data obtained from aircraft and satellites, when properly calibrated allows the measurement of important terms in the radiative surface energy budget a urban landscape scale.

Luvall, Jeffrey C.↗