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NASA NTRS1975

Future monitoring of charged particle energy deposition into the upper atmosphere and comments on possible relationships between atmospheric phenomena and solar and/or geomagnetic activity

Monitoring of earth's atmosphere was conducted for several years utilizing the ITOS series of low-altitude, polar-orbiting weather satellites. A space environment monitoring package was included in these satellites to perform measurements of a portion of earth's charged particle environment. The charged particle observations proposed for the low-altitude weather satellite TIROS N, are described which will provide the capability of routine monitoring of the instantaneous total energy deposition into the upper atmosphere by the precipitation of charged particles from higher altitudes. Such observations may be of use in future studies of the relationships between geomagnetic activity and atmospheric weather pattern developments. Estimates are given to assess the potential importance of this type of energy deposition. Discussion and examples are presented illustrating the importance of distinguishing between solar and geomagnetic activity as possible causative sources. Such differentiation is necessary because of the widely different spatial and time scales involved in the atmospheric energy input resulting from these various sources of activity.

Williams, D. J.↗

NASA NTRS1984

An experimental and theoretical investigation of deposition patterns from an agricultural airplane

A flight test program has been conducted with a representative agricultural airplane to provide data for validating a computer program model which predicts aerially applied particle deposition. Test procedures and the data from this test are presented and discussed. The computer program features are summarized, and comparisons of predicted and measured particle deposition are presented. Applications of the computer program for spray pattern improvement are illustrated.

Morris, D. J.↗

NASA NTRS1984

Correlation of thermophoretically-modified small particle diffusional deposition rates in forced convection systems with variable properties, transpiration cooling and/or viscous dissipation

A cooled object (heat exchanger tube or turbine blade) is considered to be immersed in a hot fluid stream containing trace amounts of suspended vapors and/or small particles. Numerical prediction calculations were done for self-similar laminar boundary layers and law-of-the-wall turbulent boundary layers. Correlations are presented for the effect of thermophoresis in the absence of transpiration cooling and viscous dissipation; the effect of real suction and blowing in the absence of thermophoresis; the effect of viscous dissipation on thermophoresis in the absence of transpiration cooling; and the combined effect of viscous dissipation and transpiration cooling on thermophoresis. The final correlation, St/St-sub-zero, is insensitive to particle properties, Euler number, and local mainstream temperature.

Gokoglu, S. A.↗

NASA NTRS1984

Model studies in catalysis with uhv-deposited metal particles and clusters

Small supported metal particles have become a popular area of intense research interest, and important contributions to the considered problems are being made from the fields of uhv technology, thin film physics surface science, and surface and thin film instrumentation. Attention is given to insulating supports, particulate metal deposits and their properties, metal/support interactions and gas exposures, and integrated experimental approaches. It is concluded that major contributions to the field of model catalysis should be forthcoming in the near future from uhv-based methods of research. Catalysis and catalysis-related problem areas expected to benefit from advanced model studies include catalyst preparation processing, sintering mechanisms for metals and alloys, separation of initial and final state effects for supported clusters, and the influence of particle and/or support morphologies.

Poppa, H.↗

NASA NTRS1993

Method of fabricating a rocket engine combustion chamber

A process for making a combustion chamber for a rocket engine wherein a copper alloy in particle form is injected into a stream of heated carrier gas in plasma form which is then projected onto the inner surface of a hollow metal jacket having the configuration of a rocket engine combustion chamber is described. The particles are in the plasma stream for a sufficient length of time to heat the particles to a temperature such that the particles will flatten and adhere to previously deposited particles but will not spatter or vaporize. After a layer is formed, cooling channels are cut in the layer, then the channels are filled with a temporary filler and another layer of particles is deposited.

Holmes, Richard R.↗

NASA NTRS2024

Influence of More Mechanistic Representation of Particle Dry Deposition on 1850–2000 Changes in Global Aerosol Burdens and Radiative Forcing

Robust estimates of historical changes in aerosols are key for accurate constraints on climate sensitivity. Dry deposition is a primary sink of aerosols from the atmosphere. However, most global climate models do not accurately represent observed strong dependencies of dry deposition following turbulent transport on aerosol size. It is unclear whether there is a substantial impact of mischaracterized aerosol deposition velocities on historical aerosol changes. Here we describe improved mechanistic representation of aerosol dry deposition in the NASA Goddard Institute for Space Studies (GISS) global climate model, ModelE, and illustrate the impact on 1850–2000 changes in global aerosol burdens as well as aerosol direct and cloud albedo effects using a set of 1850 and 2000 time slice simulations. We employ two aerosol configurations of ModelE (a “bulk” mass-based configuration and a configuration that more explicitly represents aerosol size distributions, internal mixing, and microphysics) to explore how model structural differences in aerosol representation alter the response to representation of dry deposition. Both configurations show larger historical increases in the global burdens of non-dust aerosols with the new dry deposition scheme, by 11% in the simpler mass-based configuration and 23% in the more complex microphysical configuration. Historical radiative forcing responses, which vary in magnitude from 5% to 12% as well as sign, depend on the aerosol configuration.

aerosol↗

NASA NTRS2000

Apparatus for electrohydrodynamically assembling patterned colloidal structures

A method apparatus is provided for electrophoretically depositing particles onto an electrode, and electrohydrodynamically assembling the particles into crystalline structures. Specifically, the present method and apparatus creates a current flowing through a solution to cause identically charged electrophoretically deposited colloidal particles to attract each other over very large distances (<5 particle diameters) on the surface of electrodes to form two-dimensional colloidal crystals. The attractive force can be created with both DC and AC fields and can modulated by adjusting either the field strength or frequency of the current. Modulating this lateral attraction between the particles causes the reversible formation of two-dimensional fluid and crystalline colloidal states on the electrode surface. Further manipulation allows for the formation of two or three-dimensional colloidal crystals, as well as more complex designed structures. Once the required structures are formed, these three-dimension colloidal crystals can be permanently frozen or glued by controlled coagulation induced by to the applied field to form a stable crystalline structure.

Trau, Mathias↗

NASA NTRS1999

Method for electrohydrodynamically assembling patterned colloidal structures

Trau, Mathias↗

NASA NTRS1979

A structural analysis of small vapor-deposited 'multiply twinned' gold particles

High resolution selected zone dark field, Bragg reflection imaging and weak beam dark field techniques of transmission electron microscopy were used to determine the structure of small gold particles vapor deposited on NaCl substrates. Attention was focused on the analysis of those particles in the 50-150 A range that have pentagonal or hexagonal bright field profiles. These particles have been previously described as multiply twinned crystallites composed of face-centered cubic tetrahedra. The experimental evidence of the present studies can be interpreted on the assumption that the particle structure is a regular icosahedron or decahedron for the hexagonal or the pentagonal particles respectively. The icosahedron is a multiply twinned rhombohedral crystal and the decahedron is a multiply twinned body-centered orthorhombic crystal, each of which constitutes a slight distortion from the face-centered cubic structure.

Yang, C. Y.↗

NASA NTRS2000

Rapid Changes in Mercury's Sodium Exosphere

Sodium in the atmosphere of Mercury can be detected by sunlight scattered in the D1 and D2 resonance lines. Images of the sodium emission show that the sodium density changes from day to day and is often concentrated in regions at high or mid latitudes. Drew Potter (NASA/JSC) and Tom Morgan (SWRI) suggested that sputtering by magnetospheric particles was the origin of the sodium. A problem with this is that the magnetic field of Mercury is strong enough that it is believed to shield the surface from solar particles much of the time, although particle precipitation at the magnetospheric cusps could deposit particles to the surface at high latitudes. Ann Sprague (UA/LPL) noted that the "spots" of sodium emission tended to coincide with major geologic features, such as the Caloris Basin. She proposed that the sodium is released from sodiumrich surface rocks that are associated with these features; however, some spots have appeared where there are no obvious geologic features. Some of the difficulty in ascribing a source for the sodium arises from the effect of terrestrial atmospheric blurring of the image. It is hard to tell exactly where the sodium emission originates after the atmosphere has blurred the image. Potter, Killen (SWRI), and Morgan recently developed a technique for correcting sodium images for atmospheric blurring, using images made with a large-area image slicer. They applied this technique to a series of Mercury sodium observations made in November, 1997 at the McMath-Pierce Solar Telescope. Their technique for producing images from the spectroscopic data provides images of both the sodium emission and of the sunlight reflected from the surface.

Potter, Drew↗

NASA NTRS1975

The influence of man in space observations

The paper evaluates the Skylab missions from the viewpoint of to what extent the presence of men may have been a detriment to scientific observations, either through their movements or through contamination of the spacecraft and instruments. The stability of the instrument canister within the Apollo Telescope Mount was secured by the Experiment Pointing Control System. Angular stability was specified to be within plus or minus 2.5 arc seconds, and was found to be less than 2 arc seconds during normal crew activity. No astronomical observations were reported as being degraded by crew movements. Instrumentation was installed to measure rates of contaminant particle deposition on optical surfaces. Clouds were formed from particles originating in outgassing from vehicle surface materials and from vent apertures. The Coronograph Contamination Measurement Instrument was used to measure the brightness of the induced cloud surrounding Skylab. Preliminary analysis shows no significant degradation of photographic data attributable to contamination.

Hanes, T. E.↗

NASA NTRS1993

Contamination measurements on experiment M0003

The contamination monitors on the M0003 experiment consisted of passive sample collectors to measure molecular and particulate deposition. The collectors were placed in the leading and trailing edge trays of M0003. The objective was to quantify the contaminants and determine how contamination affected the other materials in the trays. Duplicate collectors were placed inside the vacuum canisters that provided protection from the launch, ascent, deployment, and recovery environments. Analyses of the samples show small quantities of molecular deposition on both the leading and trailing edge trays. Silicone deposits are negligible. The aluminized fused silica, second surface mirrors showed small changes in solar absorptances. This is consistent with the small quantities of molecular deposits deduced from the FTIR measurements. The results of particle deposition, light scatter, and a micrometeoroid (or debris) impact are presented.

Borson, Eugene N.↗

NASA NTRS1985

Preparation and analysis of particulate metal deposits

Small particles and clusters of palladium were grown by deposition from the vapor phase under ultrahigh vacuum conditions. Amorphous and crystalline support films of Al2O3 and ultrathin amorphous carbon films were used as substrate materials. The growth of the metal deposit was monitored in situ by scanning transmission diffraction of energy-filtered 100 kV electrons and high resolution transmission electron microscopy (TEM) analysis was performed in a separate instrument. It was established by in situ TEM, however, that the transfer of specimens in this case did not unduly affect the size and distribution of deposit particles. It was found that the cleanness, stoichiometry, crystallinity and structural perfection of the support surface play an essential role in determining the crystalline perfection and structure of the particles. The smallest palladium clusters reproducibly prepared contained not more than six atoms but size determinations below 1 nm average particle diameter are very problematic with conventional TEM. Palladium particles grown on carbon supports feature an impurity-stabilized mosaic structure.

Poppa, H.↗

NASA NTRS1985

Thermophoretically enhanced mass transport rates to solid and transpiration-cooled walls across turbulent (law-of-the-wall) boundary layers

Convective-diffusion mass transfer rate predictions are made for both solid wall and transpiration-cooled 'law-of-the-wall' nonisothermal turbulent boundary layers (TBLs), including the mechanism of thermophoresis, i.e., small particle mass transport 'down a temperature gradient'. The present calculations are confined to low mass-loading situations but span the entire particle size range from vapor molecules to particles near the onset of inertial ('eddy') impaction. It is shown that, when Sc is much greater than 1, thermophoresis greatly increases particle deposition rates to internally cooled solid walls, but only partially offsets the appreciable reduction in deposition rates associated with dust-free gas-transpiration-cooled surfaces. Thus, efficient particle sampling from hot dusty gases can be carried out using transpiration 'shielded' probe surfaces.

Gokoglu, Suleyman A.↗

NASA NTRS2015

Forecasting Space Weather Events for a Neighboring World

Shortly after NASA's Mars Atmosphere and Volatile EvolutioN mission (MAVEN) spacecraft entered Mars' orbit on 21 September 2014, scientists glimpsed the Martian atmosphere's response to a front of solar energetic particles (SEPs) and an associated coronal mass ejection (CME). In response to some solar flares and CMEs, streams of SEPs burst from the solar atmosphere and are further accelerated in the interplanetary medium between the Sun and the planets. These particles deposit their energy and momentum into anything in their path, including the Martian atmosphere and MAVEN particle detectors. MAVEN scientists had been alerted to the likely CME-Mars encounter by a space weather prediction system that had its origins in space weather forecasting for Earth but now forecasts space weather for Earth's neighboring planets. The two Solar Terrestrial Relations Observatory spacecraft and Solar Heliospheric Observatory observed a CME on 26 September, with a trajectory that suggested a Mars intercept. A computer model developed for solar wind prediction, the Wang-Sheeley-Arge-Enlil cone model [e.g., Zheng et al., 2013; Parsons et al., 2011], running in real time at the Community Coordinated Modeling Center (CCMC) located at NASA Goddard since 2006, showed the CME propagating in the direction of Mars (Figure 1). According to MAVEN particle detectors, the disturbance and accompanying SEP enhancement at the leading edge of the CME reached Mars at approximately 17 hours Universal Time on 29 September 2014. Such SEPs may have a profound effect on atmospheric escape - they are believed to be a possible means for driving atmospheric loss. SEPs can cause loss of Mars' upper atmosphere through several loss mechanisms including sputtering of the atmosphere. Sputtering occurs when atoms are ejected from the atmosphere due to impacts with energetic particles.

space weather↗

NASA NTRS1984

Computer Program for the Calculation of Multicomponent Convective Diffusion Deposition Rates from Chemically Frozen Boundary Layer Theory

The computer program based on multicomponent chemically frozen boundary layer (CFBL) theory for calculating vapor and/or small particle deposition rates is documented. A specific application to perimter-averaged Na2SO4 deposition rate calculations on a cylindrical collector is demonstrated. The manual includes a typical program input and output for users.

Gokoglu, S. A.↗

NASA NTRS1979

Volcanic resurfacing rates and implications for volatiles on Io

The rates of volcanic resurfacing on Io are estimated on the basis of two separate observations and the implications of these rates for the volatile history of Io and the supply of material to the Jovian torus are discussed. Rates of resurfacing based on the lack of observable impact craters and assuming a Jovian cratering rate similar to those of the moon and Mars are found to be on the order of 0.1 cm/year. Estimated deposition rates of volcanic matter are found to be in general agreement with cratering rate determinations, if large particle deposition, undetected volcanic activity, volcanic flows and gas condensation are taken into account. Escape rates from Io estimated for sulfur, oxygen and sodium, based on their concentrations around Io, indicate that only a fraction of the present volcanic material can escape. Thermal and nonthermal escape mechanisms are suggested to account for the current loss of sulfur and oxygen from Io's upper atmosphere, while sputtering of atoms from the surface by impacting magnetospheric ions is suggested as the mechanism of sodium supply.

Johnson, T. V.↗

NASA NTRS1984

Experimental verification of vapor deposition model in Mach 0.3 burner rigs

A comprehensive theoretical framework of deposition from combustion gases was developed covering the spectrum of various mass delivery mechanisms including vapor, thermophoretically enhanced small particle, and inertially impacting large particle deposition. Rational yet simple correlations were provided to facilitate engineering surface arrival rate predictions. Experimental verification of the deposition theory was validated using burner rigs. Toward this end, a Mach 0.3 burner rig apparatus was designed to measure deposition rates from salt-seeded combustion gases on an internally cooled cylindrical collector.

Gokoglu, S. A.↗