Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Surface analysis”

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 1,495 records · Page 83
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Laboratory band strengths of methane and their application to the atmospheres of Jupiter, Saturn, Uranus, Neptune, and Titan

This paper reports laboratory studies of the visible spectrum of methane at column densities between 0.4 and 5 km-am and confirms the identification of bands at 4410, 4590, 4860, 5090, 5430, 5760, and 5970 A as caused by methane. Detailed equivalent-width measurements at 15 different pressure path lengths are employed to determine curves of growth and band strengths for the bands at 4410, 4860, 5430, and 5760 A. Using the curve-of-growth measurements in the reduction of planetary observations, the methane abundances in the atmospheres of Jupiter and Saturn are found to be between a factor of 3 and 4 larger than previously accepted values based on the analysis of the 3 nu(3) band at 1.1 microns, while the amount on Titan is significantly less than that obtained from an analysis of the same band with the assumption of a pure methane atmosphere. The present results, when combined with the band analysis, suggest a surface pressure on Titan of at least 0.4 atm. Extrapolation of these laboratory data to observations of Uranus and Neptune lead to single-air-mass column densities of 5.8 and 7.6 km-am of methane, respectively.

Lutz, B. L.↗
NASA NTRS1975

Elemental composition and size distribution of particulates in Cleveland, Ohio

Measurements have been made of the elemental particle size distribution at five contrasting urban environments with different source-type distributions in Cleveland, Ohio. Air quality conditions ranged from normal to air pollution alert levels. A parallel network of high-volume cascade impactors (5-stage) were used for simultaneous sampling on glass fiber surfaces for mass determinations and on Whatman-41 surfaces for elemental analysis by neutron activation for 25 elements. The elemental data are assessed in terms of distribution functions and interrelationships and are compared between locations as a function of resultant wind direction in an attempt to relate the findings to sources.

Leibecki, H. F.↗
NASA NTRS1976

Lunar soil movement registered by the Apollo 17 cosmic dust experiment

The paper describes the Lunar Ejecta and Meteorites (LEAM) experiment of the Apollo 17 flight mission, placed in the Taurus-Littrow area of the moon. The objective of the experiment was to measure impact parameters of cosmic dust on the lunar surface. Preliminary data analysis led to the recognition that the bulk of events recorded by the LEAM experiment are not signatures of hypervelocity cosmic dust particles as expected, but are induced signatures of electrostatically charged and transported lunar fines.

Berg, O. E.↗
NASA NTRS1976

Atmospheric analysis and prediction model development, volume 1

A set of hemispheric atmospheric analysis and prediction models was designed and tested. All programs were executed on either a 63 x 63 or 187 x 187 polar stereographic grid of the Northern Hemisphere. Parameters for objective analysis included sea surface temperature, sea level pressure, and twelve levels (from 1,000 to 100 millibars) of temperatures, heights, and winds. Stratospheric extensions (up to 10 millibars) were also provided. Four versions of a complex atmospheric prediction model, based on primitive equations, were programmed and tested. These models were executed on either the 63 x 63 or 187 x 187 grid, using either five or ten computational layers. The coarse-mesh (63 x 63) models were tested using real data for the period 21-23 April 1976. The fine-mesh (187 x 187) models were debugged, but insufficient computer resources precluded production tests. Preliminary test results for the 63 x 63 models are provided. Problem areas and proposed solutions are discussed.

Kesel, P. G.↗
NASA NTRS1977

Lunar resource surveys from orbit

The chemical composition of lunar soil and rocks is known now for nine surface sites, by analysis of returned samples. Three classes of silicate material, mare basalt, KREEP, and highland material (sometimes called ANT) have been identified as major components. Gamma-ray and X-ray instruments have mapped the Apollo 15 and 16 ground tracks for major elements, K, and Th. It is hoped that the Lunar Polar Orbiter will carry instruments capable of producing a chemical map of the entire moon. The most exciting possibility is that ice may exist in shadowed regions near the lunar pole.

Arnold, J. R.↗
NASA NTRS1976

Impact ejecta on the moon

The response of a lunar-sized object to the impact of meteoroids no more than about 100 km in radius is studied by means of a numerical model. The partitioning of impact energy into the kinetic and internal energy of the ejecta is obtained by using the conservation of mass, momentum, and energy conservation equations in finite-difference form within an Eulerian framework with approximate equations of state. The calculations are performed for a 15 km/sec impact of an iron object 5 cm in radius on a gabbroic anorthosite surface. Ejecta ballistic analysis is then performed. Most of the material lost escaping the moon is lunar crust material. Only 0.2% of the meteoroid escapes, all in the vapor phase.

Okeefe, J. D.↗
NASA NTRS1977

Primary aberrations for grazing incidence

Beginning with exact relations between object and image coordinates for a single reflective surface, a systematic analysis of general grazing incidence systems is presented. A complete set of primary aberrations for single-element and two-element systems is developed. The importance of a judicious choice for a coordinate system in showing field curvature to be clearly the predominant aberration for a two-element system is discussed. The validity of the theory is verified through comparisons with the exact ray-trace results for the case of a telescope.

Winkler, C. E.↗
NASA NTRS1977

Temporal evolution of the equatorial K-corona

Variation of the equatorial K-corona radiance at 2.5 solar radii from the sun center was studied on a daily basis during the Skylab mission (May 1973 to February 1974). The radiance data may be divided into three periods, the first characterized by a smooth variation in time, the second by a signal that is neither persistent in the short term nor recurrent from one limb passage to the next, and the third (and longest period) by a signal exhibiting an orderly, periodically increasing intensity. The data may be interpreted as indicating a general simplification of the coronal magnetic field; harmonic analysis of the surface field provides additional information on the evolution of the equatorial K-corona structures.

Macqueen, R. M.↗
NASA NTRS1978

Sublimate morphology on 74001 and 74002 orange and black glassy droplets

SEM-EDX analysis of the surface morphology of the 74001 and 74002 orange and black glassy droplets has revealed the presence of ubiquitous micromound coatings. Assuming that the diameter of an individual micromound is an indication of total coating thickness, then the thickness of this volatile and metal-rich layer ranges from less than 20 A to over 300 A in thickness. On rare droplets the micromound coating is partially covered by a sparse population of crystals and masses that are essentially NaCl in composition. Additionally, an irregular mass on the surface of one black droplet may contain free sulfur. Amoeboid masses of iron, some with incipient crystal faces, are also present on a few droplet surfaces. The above features, i.e., halite crystals, sulfur-rich masses and amoeboid iron, are rare; the more common occurrence of metals and volatiles is in the micromound coating. Based on our observations of several hundred spheres from both Apollo and Luna missions, the classic micromound coating is unique to the Apollo 15 green and Apollo 17 orange and black droplets. Although some investigators have proposed various impact sequences to produce these unique droplets, the volcanic fire fountain origin is favored.

Clanton, U. S.↗
NASA NTRS1980

A sunspot periodicity and the solar rotation

A least squares power spectrum analysis of daily sunspot numbers for the last 122 years yielded a statistically significant peak at 12.0715 plus or minus .002 days period. This feature at 11.685 days (sidereal) of the sunspot spectrum is discussed in relation to the peak at 12.22 days (sidereal) which Dicke found in his oblateness data. The data is attributed to the Sun's core if the core rotates at either 12.0715 days or 24.1430 days period (synodic). It is suggested that spacecraft observations combined with correlative analysis of solar surface features between eastern and western hemispheres could further reveal a basic core periodicity. A Dicke type space oblateness experiment is discussed for providing better photospheric observations than a ground instrument to determine the core periodicity.

Knight, J. W.↗
NASA NTRS1980

Research on lunar Mare emplacement and impact cratering experiments

A model was derived enabling the interpretation of lunar styles of volcanism through the analysis of various surface features. The model was applied to several areas on the Moon, including the Orientale Basin, the Smythii Basin, the Herigonious region, and several highland areas. Concurrent with the application of the model, several topical studies of various aspects of lunar volcanism were completed. A series of impact crater experiments was conducted at NASA Ames in order to determine the effect that viscous targets would have on cratering mechanics and morphology for application in studies of Martian ejecta flow craters. The results of the experiments led to a model that can account for the formation of multiple flow lobes and the general morphology of some aspects of Martian craters.

Greeley, R.↗
NASA NTRS1981

Considerations in the design of large space structures

Several analytical studies of topics relevant to the design of large space structures are presented. Topics covered are: the types and quantitative evaluation of the disturbances to which large Earth-oriented microwave reflectors would be subjected and the resulting attitude errors of such spacecraft; the influence of errors in the structural geometry of the performance of radiofrequency antennas; the effect of creasing on the flatness of tensioned reflector membrane surface; and an analysis of the statistics of damage to truss-type structures due to meteoroids.

Hedgepeth, J. M.↗
NASA NTRS1981

Galileo Probe forebody thermal protection

Material response solutions for the forebody heat shield on the candidate 310-kg Galileo Probe are presented. A charring material ablation analysis predicts thermochemical surface recession, insulation thickness, and total required heat shield mass. Benchmark shock layer solutions provide the imposed entry heating environments on the ablating surface. Heat shield sizing results are given for a nominal entry into modeled nominal and cool-heavy Jovian atmospheres, and for two heat-shield property models. The nominally designed heat shield requires a mass of at least 126 kg and would require an additional 13 kg to survive entry into the less probable cool-heavy atmosphere. The material-property model with a 30% surface reflectance reduces these mass requirements by as much as 16%.

Green, M. J.↗
NASA NTRS1981

Secondary Electron Emission Yields

The secondary electron emission (SEE) characteristics for a variety of spacecraft materials were determined under UHV conditions using a commercial double pass CMA which permits sequential Auger electron electron spectroscopic analysis of the surface. The transparent conductive coating indium tin oxide (ITO) was examined on Kapton and borosilicate glass and indium oxide on FED Teflon. The total SEE coefficient ranges from 2.5 to 2.6 on as-received surfaces and from 1.5 to 1.6 on Ar(+) sputtered surfaces with 5 nm removed. A cylindrical sample carousel provides normal incidence of the primary beam as well as a multiple Faraday cup measurement of the approximately nA beam currents. Total and true secondary yields are obtained from target current measurements with biasing of the carousel. A primary beam pulsed mode to reduce electron beam dosage and minimize charging of insulating coatings was applied to Mg/F2 coated solar cell covers. Electron beam effects on ITO were found quite important at the current densities necessary to do Auger studies.

Krainsky, I.↗
NASA NTRS1982

Assessment of Alternate Thermal Protection Systems for the Space Shuttle Orbiter

Candidate concepts are identified. The impact on the Shuttle Orbiter performance life cycle cost, and risk was assessed and technology advances required to bring the selected TPS to operational readiness are defined. The best system is shown to be a hybrid blend of metallic and carbon-carbon TPS concepts. These alternate concepts offer significant improvements in reusability and are mass competitive with the current ceramic tile reusable surface insulation. Programmatic analysis indicates approximately five years are required to bring the concepts to operational readiness.

Kelly, H. N.↗
NASA NTRS1982

Rawinsonde sounding data and synoptic conditions for the CCOPE-VAS experiment, July 1981

During the cooperative convective precipitation experiment, eight times were selected as VISSR atmospheric sounder (VAS) observation periods. A synoptic analysis of the surface and the 850, 700, 500, 300, and 200 maps for those eight periods. The satellite and radar data for those periods are included with the analyses. There were five rawinsonde stations in eastern Montana which made extra soundings for the VAS periods.

Henry, W. K.↗
NASA NTRS1982

Seasat altimeter timing bias estimation

A technique developed for the solution of time lag bias based on the analysis of sea surface height discrepancies at ground track intersections, prompted by the presence of a time calibration bias in Seasat altimeter data that produced measurement errors in excess of 1 m, is shown to yield a separation of the dominant, once-per-revolution ephemeris error amounting to about 1.5 m rms from the timing error signature. The technique does not depend on precise geoid data, and in application to a global Seasat altimeter data set covering July 28-August 9, 1978, has yielded a time lag value of -81.0 + or - 2 msec. This corroborates the -79.4 msec revised value derived from a reexamination of internal instrument time delays.

Marsh, J. G.↗
NASA NTRS1981

Second Eastern Regional Remote Sensing Applications Conference

Participants from state and local governments share experiences in remote sensing applications with one another and with users in the Federal government, universities, and the private sector during technical sessions and forums covering agriculture and forestry; land cover analysis and planning; surface mining and energy; data processing; water quality and the coastal zone; geographic information systems; and user development programs.

Imhoff, M. L.↗