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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

The formation and movement in the stratosphere of very dry air

The possible sources of very dry stratospheric air are investigated, extending the analysis of Atticks and Robinson (1983), on the basis of data from about 16,000 radiosonde ascents obtained during the FGGE from December 1978 through November 1979, from high-resolution Tiros and GMS IR-radiance observations on January 28, 1979, and from LIMS zonal-mean H2O-mass-mixing-ratio (HMMR) observations in December 1978 and May 1979. The data are compiled in tables and graphs and analyzed statistically, and the occurrence of low radiance temperatures (below -86 C) in the IR data (0.00025) is shown to be much lower than that (about 0.25) in the radiosonde data. It is inferred that air with HMMR less than 1.5 x 10 to the -6th could be produced in Cb cloud turrets, but not by the mechanism proposed by Danielsen (1982).

Robinson, G. D.↗
NASA NTRS1987

Measured performance of the heat exchanger in the NASA icing research tunnel under severe icing and dry-air conditions

Measurements were made of the pressure drop and thermal perfomance of the unique refrigeration heat exchanger in the NASA Lewis Icing Research Tunnel (IRT) under severe icing and frosting conditions and also with dry air. This data will be useful to those planning to use or extend the capability of the IRT and other icing facilities (e.g., the Altitude Wind Tunnel-AWT). The IRT heat exchanger and refrigeration system is able to cool air passing through the test section down to at least a total temperature of -30 C (well below icing requirements), and usually up to -2 C. The system maintains a uniform temperature across the test section at all airspeeds, which is more difficult and time consuming at low airspeeds, at high temperatures, and on hot, humid days when the cooling towers are less efficient. The very small surfaces of the heat exchanger prevent any icing cloud droplets from passing through it and going through the tests section again. The IRT heat exchanger was originally designed not to be adversely affected by severe icing. During a worst-case icing test the heat exchanger iced up enough so that the temperature uniformaity was no worse than about +/- 1 deg C. The conclusion is that the heat exchanger design performs well.

Olsen, W.↗
NASA NTRS1987

Acid dew and the role of chemistry in the dry deposition of reactive gases to wetted surfaces

A formalism is developed to describe the dry deposition of soluble reactive gases to wetted surfaces in terms of the relevant meteorological conditions, the surface roughness, the total amount of liquid water present on the surface, the rate of accumulation of this water, and the species' solubility and reactivity in the surface water. This formulation is then incorporated into a model designed to simulate the generation of acidic dew from the deposition of HNO3, SO2, S(IV) oxidants, H2O2, and O3. Similar to the observations of dew in the continental U.S., the model generates a dewdrop pH of about 4 by the end of the night; the pH can rapidly fall to toxic levels due to rapid evaporation after sunrise. Relatively low deposition velocities are predicted for the SO2 and O3 because of their lower solubilities and hence larger surface resistances than those of the other oxidants. Because the chemical lifetime of the SO2 in the dew is influenced by the atmospheric levels of H2O2, O3, and SO2, the SO2 deposition velocity is a strong function of these species' atmospheric abundances.

Chameides, William L.↗
NASA NTRS1988

The cycle of biogenic sulfur compounds over the Amazon Basin. I - Dry season

The concentrations of SO2, methylmercaptan, dimethylsulfide, H2S, aerosol sulfate, and methanesulfonate over the Amazon Basin during the July/August dry season were determined from samples collected by the NASA research aircraft. The results indicate that biogenic emissions represent an important, if not the dominant, source of sulfur to the atmosphere over Amazonia. Per unit area, the wet continental tropics appear to have about the same reduced sulfur emission flux as the oceanic area average (about 6 nmol/sq m per min), consistent with the fact that the aerosol sulfate concentration over the Amazon Basin is similar to the excess sulfate levels over the remote oceans. However, since the wet tropical continents represent only about 3 percent of the earth's surface, their global contribution is modest; it is also small relative to the anthropogenic emissions from fossil fuel burning.

Andreae, M. O.↗
NASA NTRS1988

Regional aerosol chemistry of the Amazon Basin during the dry season

The distribution and chemical composition of the atmospheric aerosol over the Amazon Basin forest were determined during the 1985 July-August dry season, using data on the aerosol chemical constituent concentration collected during the NASA Global Tropospheric Experiment Amazon Boundary Layer Experiment 2A mission. The results of the analyses suggest that there is a remarkable compositional and spatial homogeneity of the atmospheric aerosol on an extensive regional scale. Particulate organic carbon is the dominant component of the atmospheric aerosol, exhibiting an average concentration of about 740 nmol/cu m in the mixed layer and about 220 nmol/cu m in free tropospheric air. Oxalate and SO4(2-) exhibited the greatest enrichment in the mixed layer, while Cl(-) showed essentially no enrichment. The aerosol in the Amazonian atmosphere is essentially acid-base neutral, primarily as a result of incorporation of NH(+), which is presumably derived from NH3 released by the forest ecosystem.

Talbot, R. W.↗
NASA NTRS1990

A simulation and diagnostic study of water vapor image dry bands

Limited Area Mesoscale Prediction System model simulation and a special 3-hr radiosonde data set were used to investigate warm bands in the 6.7-micron water-vapor satellite imagery on March 6-7, 1982. It was found that the model reproduces major characteristics of the observed blackbody temperature, T(B), field. A 'development' dry image feature was found to occur in conjunction with an upper level shortwave trough, and an 'advective' feature was found associated with a polar jet streak. Both model and observed T(B) features were associated with vorticity maxima.

Muller, Bradley M.↗
NASA NTRS1990

Ozone measurements in Amazonia - Dry season versus wet season

Recent ozone measurements taken in the Amazonian rain forest environment during the wet season (April-May 1987) are described, revealling new aspects of the regional atmospheric chemistry. The measurements were part of the Amazon Boundary Layer Experiment (ABLE 2B) mission and utilized UV absorption as a measurement technique to obtain surface ozone data; 20 ozonesondes were launched in order to obtain vertical ozone profiles used to describe the upper troposphere and stratosphere. The major differences in comparison to a previous dry season experiment, which found ozone concentrations to be lower in the whole troposphere by nearly a factor of 2, are stressed.

Kirchhoff, V. W. J. H.↗
NASA NTRS1991

Rapid Dry Etching Of Photoresists Without Toxic Gases

Experimental dry etching technique strips photoresists from semiconductor wafers without damaging semiconductor materials. Makes use of afterglow existing downstream from plasma generated by radio-frequency electric field. Constituents of afterglow react with sacrificial polymer to make reactive gases that quickly etch-away photoresist. Strips quickly at room temperature; not necessary to heat substrates. No hazardous or toxic chemicals used.

Lerner, Narcinda R.↗
NASA NTRS1989

Effect of grinding on the fatigue life of titanium alloy (5 Al-2.5 Sn) under dry and wet conditions

The principal factors in the performance of aerospace materials are strength-to-weight ratio, fatigue life, fracture toughness, survivability and, of course, reliability. Machining processes and, in particular, grinding under adverse conditions have been found to cause damage to surface integrity and affect the residual stress distribution in the surface and subsurface region. These effects have a direct bearing on the fatigue life. In this investigation the effects of grinding conditions on the fatigue life of Titanium 5 Al-2.5Sn were studied. This alloy is used in ground form in the manufacturing of some critical components in the space shuttle's main engine. It is essential that materials for such applications be properly characterized for use in severe service conditions. Flat sub-size specimens 0.1 inch thick were ground on a surface grinding machine equipped with a variable speed motor at speeds of 2000 to 6000 rpm using SiC wheels of grit sizes 60 and 120. The grinding parameters used in this investigation were chosen from a separate study. The ground specimens were then fatigued at a selected stress and the resulting lives were compared with that of the virgin material. The surfaces of the specimens were examined under a scanning electron microscope, and the roughness and hardness were measured using a standard profilometer and microhardness tester, respectively. The fatigue life of the ground specimens was found to decrease with the increase in speed for both dry and wet conditions. The fatigue life of specimens ground under wet conditions showed a significant increase at the wheel speed of 2000 rpm for both the grit sizes and thereafter decreased with increase profilometry, microhardness measurements and scanning electron microscopic examination.

Rangaswamy, Partha↗
NASA NTRS1991

The density temperature and the dry and wet virtual adiabats

A density temperature is introduced to represent virtual temperature and potential temperature on thermodynamic diagrams. This study reviews how the dry and wet virtual adiabats can be used to represent stability and air parcel density for unsaturated and cloudy air, and present formula and tabulations.

Bartlo, J.↗
NASA NTRS1991

Evaluation of the high pressure oxidizer turbopump (HPOTP) vacuum drying procedures

Tests carried out on the HPOTP to determine the effects of surface finish on the rate at which water vapor could be removed from the bearing/spacer cavity are described. Data from these tests are used to evaluate the effects of a lower drying temperature on the flow rate of water vapor from the bearing/spacer cavity as well. It was found that, if the normality nut is torqued, there is no evidence of moisture entering the bearing/spacer cavity from external sources.

Fears, S. D.↗
NASA NTRS1991

LaRC dry powder towpreg process

The dry powder towpreg process overcomes many of the difficulties associated with melt, solution and slurry prepregging of advanced composite materials. In the process, fluidized powder is deposited on spread tow bundles and melted on the fibers by radiant heating to adhere the polymer to the fiber. Bench scale design and operating data have been correlated for use in process scale up to commercial operation. Powdered towpreg has been woven and molded into preform material of good quality. Cost estimates suggest that processing costs are comparable to those of conventional hot melt prepreg. In the future, from a part fabrication point of view, powder coated prepreg tape, woven broad goods and woven and braided preforms may be considered as options to similar materials made by other methods.

Marchello, Joseph M.↗
NASA NTRS1991

A comparison of wet and dry season ozone and CO over Brazil using in situ and satellite measurements

A comparison conducted between direct measurements of Brazilian ozone and NO concentrations and space-based measurements has indicated a strong correlation between the two environmental sensing methods and indicated the seasonality of both ozone and CO concentrations in this region. Dry season increases appear to be due to both increased local biomass burning and the transport of CO and ozone from Africa. The coincident high values of both CO and ozone suggest photochemical sources, rather than a stratospheric source, for the African and South American ozone.

Watson, Catherine E.↗
NASA NTRS1993

Longevity Of Dry Film Lubricants

Report describes evaluation of dry film lubricants candidate for use in rotary joints of proposed Space Station. Study included experiments and theoretical analyses focused on longevity of sputtered molybdenum disulfide films and ion-plated lead films under conditions partially simulating rolling contact.

Kannel, J. W.↗
NASA NTRS1993

Built-up Al-Li structures for cryogenic tank and dry bay applications

The objectives are: (1) to demonstrate the cost benefits of built-up cryotank and dry bay structures; (2) to study of benefits of using Al alloys; (3) to study of benefit of using Al-Li alloys; (4) to evaluate alternative low-cost stiffener and joining concepts.

Lisagor, W. Barry↗
NASA NTRS1992

Effects of climate and lifeform on dry matter yield (epsilon) from simulations using BIOME BGC

An ecosystem process simulation model, BIOME-BGC, is used in a sensitivity analysis to determine the factors that may cause the dry matter yield (epsilon) and annual net primary production to vary for different ecosystems. At continental scales, epsilon is strongly correlated with annual precipitation. At a single location, year-to-year variation in net primary production (NPP) and epsilon is correlated with either annual precipitation or minimum air temperatures. Simulations indicate that forests have lower epsilon than grasslands. The most sensitive parameter affecting forest epsilon is the total amount of living woody biomass, which affects NPP by increasing carbon loss by maintenance respiration. A global map of woody biomass should significantly improve estimates of global NPP using remote sensing.

Hunt, E. R., Jr.↗
NASA NTRS1992

An annual model of SSM/I radiobrightness for dry soil

An annual model is presented of the temperature structure within a homogeneous, dry soil halfspace that is subject to both diurnal and annual insolation, radiant heating from the atmosphere, sensible heat exchange with the atmosphere, and radiant cooling. The thermal constitutive properties of the soil are assumed to be constant so that the heat flow equation can be solved analytically. For computational economy, a variable time interval Laplace transform method is developed to predict the temperature.

Liou, Yuei-An↗