Search NASA⌕ Search

SEARCH · Search NASA

Results for “High concentration”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

High-performance deployable structures for the support of high-concentration ratio solar array modules

A study conducted on high-performance deployable structures for the support of high-concentration ratio solar array modules is discussed. Serious consideration is being given to the use of high-concentration ratio solar array modules or applications such as space stations. These concentrator solar array designs offer the potential of reduced cost, reduced electrical complexity, higher power per unit area, and improved survivability. Arrays of concentrators, such as the miniaturized Cassegrainian concentrator modules, present a serious challenge to the structural design because their mass per unit area (5.7 kg/square meters) is higher than that of flexible solar array blankets, and the requirement for accurate orientation towards the Sun (plus or minus 0.5 degree) requires structures with improved accuracy potentials. In addition, use on a space station requires relatively high structural natural frequencies to avoid deleterious interactions with control systems and other large structural components. The objective here is to identify and evaluate conceptual designs of structures suitable for deploying and accurately supporting high-concentration ratio solar array modules.

Mobrem, M.↗
NASA NTRS2001

The Mechanism Responsible for High Concentrations of Be-7 in the Near Space

In 1990 an unexpectedly high concentration of Be-7 was discovered on the LDEF satellite surface, facing in the RAM direction. The search for an explanation of this high concentration of Be-7 which is in thermal equilibrium in the upper atmosphere, led the researchers to the hypothesis of Be-7 transport by vertical turbulent fluxes from deeper layers in the Earth's atmosphere, where Be-7 is produced as a result of nuclear reactions between solar energetic protons (which penetrated there after a solar flare) and terrestrial atmosphere elements. The experiments carried out during 1995-1999 on 'Resource F1' and 'Cosmos' satellites not only confirmed the existence of high Be-7 concentrations at altitudes of about 200 km, but also permitted to establish correlation between the concentration of Be-7 in the upper atmosphere and flare activity on the Sun. More detailed analysis of the whole set of experimental data on Be-7 measurements at satellite altitudes showed, that the appearance of high Be-7 concentrations in the upper atmosphere of the Earth is a more complicated phenomenon. Two more mechanisms , explaining the observed effect can be indicated. Firstly, the observed concentrations could be associated with direct penetration of energetic Be-7 nuclei, originating in flares, into the terrestrial atmosphere. Calculations show, that in solar cosmic rays the flux of Be-7 nuclei should be maximum in comparison to the fluxes of other Beryllium isotopes. Secondly, the high concentration of Be-7 in the upper atmosphere of the Earth could be explained by solar wind penetration through the polar zones. Theoretical analysis of active processes including flares, occurring in the solar atmosphere, leads to the conclusion, that radioactive Beryllium is constantly present in the solar atmosphere, and, possibly, is the main isotope of solar Beryllium.

Panasyuk, M. I.↗
NASA NTRS1990

Wide acceptance angle, high concentration ratio, optical collector

The invention is directed to an optical collector requiring a wide acceptance angle, and a high concentration ratio. The invention is particularly adapted for use in solar collectors of cassegrain design. The optical collector system includes a parabolic circular concave primary mirror and a hyperbolic circular convex secondary mirror. The primary mirror includes a circular hole located at its center wherein a solar collector is located. The mirrored surface of the secondary mirror has three distinct zones: a center circle, an on-axis annulus, and an off-axis section. The parabolic shape of the primary mirror is chosen so that the primary mirror reflects light entering the system on-axis onto the on-axis annulus. A substantial amount of light entering the system off-axis is reflected by the primary mirror onto either the off-axis section or onto the center circle. Subsequently, the off-axis sections reflect the off-axis light toward the solar collector. Thus, off-axis light is captured which would otherwise be lost to the system. The novelty of the system appears to lie in the configuration of the primary mirror which focuses off-axis light onto an annular portion of the secondary mirror to enable capture thereof. This feature results in wide acceptance angle and a high concentration ratio, and also compensates for the effects of non-specular reflection, and enables a cassegrain configuration to be used where such characteristics are required.

Kruer, Mark Arthur↗
NASA NTRS2004

High Concentrating GaAs Cell Operation Using Optical Waveguide Solar Energy System

This paper discusses the result of the concentrating photovoltaic (CPV) cell experiments conducted with the Optical Waveguide (OW) Solar Energy System. The high concentration GaAs cells developed by Research Triangle Institute (RTI) were combined with the OW system in a "fiber-on-cell" configuration. The sell performance was tested up to the solar concentration of 327. Detailed V-I characteristics, power density and efficiency data were collected. It was shown that the CPV cells combined with the OW solar energy system will be an effective electric power generation device.

Nakamura, T.↗
NASA NTRS1991

Wide acceptance angle, high concentration ratio, optical collector

A cassegrain optical system provides improved collection of off-axis light yet is still characterized by a high concentration ratio. The optical system includes a primary mirror for collecting incoming light and reflecting the light to a secondary mirror which, in turn, reflects the light to a solar cell or other radiation collection device. The primary mirror reflects incoming on-axis light onto an annular section of the secondary mirror and results in the reflection of a substantial amount of incoming off-axis light onto the remainder of the secondary mirror. Thus light which would otherwise be lost to the system will be captured by the collector. Furthermore, the off-axis sections of the secondary mirror may be of a different geometrical shape than the on-axis annular section so as to optimize the amount of off-axis light collected.

Kruer, Mark A.↗
NASA NTRS2021

Components Cleaning Facility, SWMU 030 Eastern High-Concentration Plume Area Implementation Work Plan Kennedy Space Center, Florida

This Implementation Work Plan (IWP) presents detailed design elements and coordination specifics to implement an air sparging (AS) Interim Measure (IM) to remediate groundwater at the Components Cleaning Facility (CCF), Eastern High Concentration Plume (HCP) Area located at Kennedy Space Center (KSC), Florida. The objective of the CCF East IM is to remediate groundwater where trichloroethene, cis-1,2-dichloroethene, and vinyl chloride concentrations exceed Florida Department of Environmental Protection Natural Attenuation Default Criteria (NADC) (identified as the HCP) via AS and to transition to monitored natural attenuation. CCF has been designated Solid Waste Management Unit 030 under KSC’s Resource Conservation and Recovery Act Corrective Action Program.

James Lloyd↗
NASA NTRS1993

Cirrus microphysics observations made during FIRE 2: Small particles, high concentrations, and probe comparisons

Aircraft observations of cirrus cloud microphysics were made near Coffeyville, Kansas during Nov. and Dec. 1991. Cloud microphysics measurements were made using both a PMS 2DC probe and an ice particle replicator, both were mounted on the UND Citation aircraft. Intercomparison is made of the size, area, and ice mass spectra determined from these probes. The PMS 2DC undercounts particles for D less than 70 microns and the replicator oversizes particles for D greater than 150 microns, at least when column rosettes are encountered. High concentrations of particles with D less than 50 microns are noted in selected portions of the 22 Nov. 91 replicator data set. Relations between the maximum dimension of a crystal and its shadow area (known as area dimensional relationships) are computed from the PMS data. Area and mass dimensional relationships are used to give a simple analytical expression for computing the wavelength dependent absorption coefficient averaged over a size bin. Calculations based upon the replicator data show that crystals with D less than 50 microns contribute significantly to the solar extinction and infrared absorption coefficients during some time intervals.

Arnott, W. P.↗
NASA NTRS2001

A Nanometer Aerosol Size Analyzer (nASA) for Rapid Measurement of High-Concentration Size Distributions

We have developed a fast-response Nanometer Aerosol Size Analyzer (nASA) that is capable of scanning 30 size channels between 3 and 100 nm in a total time of 3 seconds. The analyzer includes a bipolar charger (P0210), an extended-length Nanometer Differential Mobility Analyzer (Nano-DMA), and an electrometer (TSI 3068). This combination of components provides particle size spectra at a scan rate of 0.1 second per channel free of uncertainties caused by response-time-induced smearing. The nASA thus offers a fast response for aerosol size distribution measurements in high-concentration conditions and also eliminates the need for applying a de-smearing algorithm to resulting data. In addition, because of its thermodynamically stable means of particle detection, the nASA is useful for applications requiring measurements over a broad range of sample pressures and temperatures. Indeed, experimental transfer functions determined for the extended-length Nano-DMA using the Tandem Differential Mobility Analyzer (TDMA) technique indicate the nASA provides good size resolution at pressures as low as 200 Torr. Also, as was demonstrated in tests to characterize the soot emissions from the J85-GE engine of a T38 aircraft, the broad dynamic concentration range of the nASA makes it particularly suitable for studies of combustion or particle formation processes. Further details of the nASA performance as well as results from calibrations, laboratory tests and field applications are presented.

Han, Hee-Siew↗
NASA NTRS2019

Radar Detection of High Concentrations of Ice Particles - Methodology and Preliminary Flight Test Results

High Ice Water Content (HIWC) has been identified as a primary causal factor in numerous engine events over the past two decades. Previous attempts to develop a remote detection process utilizing modern commercial radars have failed to produce reliable results. This paper discusses the reasons for previous failures and describes a new technique that has shown very encouraging accuracy and range performance without the need for any hardware modifications to industry’s current radar designs. The performance of this new process was evaluated during the joint NASA/FAA HIWC RADAR II Flight Campaign in August of 2018. Results from that evaluation are discussed, along with the potential for commercial application, and development of minimum operational performance standards for a future commercial radar product.

Harrah, Steven D.↗
NASA NTRS2004

Design and assembly of a catalyst bed gas generator for the catalytic decomposition of high concentration hydrogen peroxide propellants and the catalytic combustion of hydrocarbon/air mixtures

A method for designing and assembling a high performance catalyst bed gas generator for use in decomposing propellants, particularly hydrogen peroxide propellants, for use in target, space, and on-orbit propulsion systems and low-emission terrestrial power and gas generation. The gas generator utilizes a sectioned catalyst bed system, and incorporates a robust, high temperature mixed metal oxide catalyst. The gas generator requires no special preheat apparatus or special sequencing to meet start-up requirements, enabling a fast overall response time. The high performance catalyst bed gas generator system has consistently demonstrated high decomposition efficiency, extremely low decomposition roughness, and long operating life on multiple test articles.

Lohner, Kevin A.↗
NASA NTRS1980

Design requirements for high-efficiency high concentration ratio space solar cells

A miniaturized Cassegrainian concentrator system concept was developed for low cost, multikilowatt space solar arrays. The system imposes some requirements on solar cells which are new and different from those imposed for conventional applications. The solar cells require a circular active area of approximately 4 mm in diameter. High reliability contacts are required on both front and back surfaces. The back area must be metallurgically bonded to a heat sink. The cell should be designed to achieve the highest practical efficiency at 100 AMO suns and at 80 C. The cell design must minimize losses due to nonuniform illumination intensity and nonnormal light incidence. The primary radiation concern is the omnidirectional proton environment.

Rauschenbach, H.↗
NASA NTRS1974

Gas exchange and the coagulation system of the blood during the effect on the body of high concentrations of oxygen and carbon dioxide

Maximum permissible concentrations of oxygen and carbon dioxide in a controlled atmosphere were determined by evaluating their effects on human gas exchange, blood coagulation, and tolerances to acute hypoxia, acceleration, and physical loads. It was found that functional disturbances depend on the concentration of respiratory gases and the length of stay in an altered atmosphere. By changing the atmospheric composition and by bringing the gaseous environment into accordance with the work and rest regimen and energy expenditures, the general reactivity of the body changes favorably.

Palosh, L.↗
NASA NTRS1981

Low cost, high concentration ratio solar cell array for space applications

A miniaturized Cassegrainian-type concentrator solar array concept for space applications is described. In-orbit cell operating temperatures near 80 C are achieved with purely passive cell cooling and a net concentration ratio of 100. A multiplicity of miniaturized, rigid solar cell concentrator subassemblies are electrically interconnected in conventional fashion and mounted into rigid frames to form concentrator solar panel assemblies approximately 14-mm thick. A plurality of such interconnected panels forms a stowable and deployable solar cell blanket. It is projected that for 20% efficient silicon cells an array of 500 kW beginning-of-life output capability, including orbiter cradle structures, can be transported by a single shuttle orbiter flight into low earth orbit. In-orbit array specific performance is calculated to be approximately 100 W/sq m and 20 W/kg, including all stowage, deployment and array figure control equipment designed for a 30-year orbital life. Higher efficiency gallium arsenide and multiple band gap solar cells will improve these performance factors correspondingly.

Patterson, R. E.↗
NASA NTRS1984

Reductions in ozone at high concentrations of stratospheric halogens

An increase in the concentration of inorganic chlorine to levels comparable to that of oxidized reactive nitrogen could cause a significant change in the chemistry of the lower stratosphere leading to a reduction potentially larger than 15 percent in the column density of ozone. This could occur, for example by the middle of the next century, if emissions of man-made chlorocarbons were to grow at a rate of 3 percent per year. Ozone could be further depressed by release of industrial bromocarbon.

Prather, M. J.↗
NASA NTRS1950

The solution of the laminar-boundary-layer equation for the flat plate for velocity and temperature fields for variable physical properties and for the diffusion field at high concentration

In connection with Pohlhausen's solution for the temperature field on the flat plate, a series of formulas were indicated by means of which the velocity and temperature field for variable physical characteristics can be computed by an integral equation and an iteration method based on it. With it, the following cases were solved: On the assumption that the viscosity simply varies with the temperature while the other fluid properties remain constant, the velocity and temperature field on the heated and cooled plate, respectively, was computed at the Prandtl numbers 12.5 and 100 (viscous fluids). A closer study of these two cases resulted in general relations: The calculations for a gas of Pr number 0.7 (air) were conducted on the assumption that all fluid properties vary with the temperature, and the velocities are low enough for the heat of friction to be discounted. The result was a thickening of the boundary layers, but no appreciable modification in shearing stress or heat-transfer coefficient.

BOUNDARY LAYER, LAMINAR - PLATES, FLAT↗
NASA NTRS1994

Large-scale circulation patterns associated with high concentrations of tropospheric ozone in the tropical South Atlantic Ocean

Several years of satellite observations indicate the presence of enhanced amounts of tropospheric ozone over the tropical South Atlantic during the austral springs. Wide-spread biomass burning is prevalent over Africa and South America during the same time of the year. Another recent satellite technique has identified the locations of fires over the continents. In this study, we present an analysis of the prevailing meteorological conditions when the highest amounts of tropospheric ozone are present.

Fakhruzzaman, K. M.↗
NASA NTRS1997

Dimerization in Highly Concentrated Solutions of Phosphoimidazolide Activated Mononucleotides

Phosphoimidazolide activated ribomononucleotides (*pN) are useful substrates for the non-enzymatic synthesis of polynucleotides. However, dilute neutral aqueous solutions of *pN typically yield small amounts of dimers and traces of polymers; most of *pN hydrolyzes to yield nucleoside 5'-monophosphate. Here we report the self-condensation of nucleoside 5'-phosphate 2- methylimidazolide (2-MeImpN with N = cytidine, uridine or guanosine) in the presence of Mg2(+) in concentrated solutions, such as might have been found in an evaporating lagoon on prebiotic Earth. The product distribution indicates that oligomerization is favored at the expense of hydrolysis. At 1.0 M, 2-MelmpU and 2-MelmpC produce about 65% of oligomers including 4% of the 3',5'-Iinked dimer. Examination of the product distribution of the three isomeric dimers in a self-condensation allows identification of reaction pathways that lead to dimer formation. Condensations in a concentrated mixture of all three nucleotides (U,C,G mixtures) is made possible by the enhanced solubility of 2-MeImpG in such mixtures. Although percent yield of intemucleotide linked dimers is enhanced as a function of initial monomer concentration, pyrophosphate dimer yields remain practically unchanged at about 20% for 2-MelmpU, 16% for 2-MeImpC and 25% of the total pyrophosphate in the U,C,G mixtures. The efficiency by which oligomers are produced in these concentrated solutions makes the evaporating lagoon scenario a potentially interesting medium for the prebiotic synthesis of dimers and short RNAs.

Kanavarioti, Anastassia↗