SEARCH · Engineering Papers

Results for “insolation”

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.

SourceResearch connectionFrom yearThrough year

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

At least 361 records · Page 20

All sources NASA NTRS DOE OSTI

NASA NTRS1984

The Martian climate: Energy balance models with CO2/H2O atmospheres

Progress in the development of a multi-reservoir, time dependent energy balance climate model for Mars driven by prescribed insolation at the top of the atmosphere is reported. The first approximately half-year of the program was devoted to assembling and testing components of the full model. Specific accomplishments were made on a longwave radiation code, coupling seasonal solar input to a ground temperature simulation, and conceptualizing an approach to modeling the seasonal pressure waves that develop in the Martian atmosphere as a result of sublimation and condensation of CO2 in polar regions.

Hoffert, M. I.↗

NASA NTRS1985

Paleohydrologic Implications of Valley Networks of Mars

Valley networks in the heavily cratered terrains of Mars represent an ancient epoch of hydrologic conditions greatly different from those of today. Available crater counts on the valley networks indicate formation during the high flux of impacting bodies charaterizing the early heavy bombardment phase of Martian history. Two populations of valleys are recognized in the equatorial regions of Mars: pristine and degraded. The latter probably formed at the very end of the heavy bombardment phase, extending into the post-heavy bombardment by formation in the intercrater plains. Pristine valleys generally form segments of larger networks with degraded components. This suggests that valley formation was a prolonged process coeval with the heavy bombardment period and extending just beyond that period in martian history. The pristine networks and pristine portions of compound networks on Mars show morphological attributes consistent with an origin by headward growth through spring sapping. On Earth spring sapping occurs where groundwater out-streamflow can be generated by insolation changes associated with orbital parameters or with geothermal effects, such as might be associated with impact or with the volcanic emplacement of the intercrater plains. Thus, it is appropriate to specify the most conservation deviation from modern hydrologic conditions on Mars that could account for the ancient epoch of valley formation.

Baker, V. R.↗

NASA NTRS1985

Mars: Long Term Changes in the State and Distribution of H2O

A model for H2O distribution and migration on Mars was formulated which takes into account: (1) thermal variations at all depths in the regolith due to variations in obliquity, eccentricity and the solar constant; (2) variations in atmospheric PH2O caused by corresponding changes in polar surface insolation; and (3) the finite kinetics of H2O migration in both the regolith and atmosphere. Results suggest that regolith H2O transport rates are more strongly influenced by polar-controlled atmospheric PH2O variations than variations in pore gas PH2O brought about by thermal variations at the buried ice interface. The configuration of the ice interface as a function of assumed soil parameter and time is derived. Withdrawal of ice proceeds to various depths at latitudes less than 50 deg and is accompanied by filling of regolith pores at latitudes greater than 50 deg and transfer of H2O to the polar cap. The transfer has a somewhat oscillatory character, but only less than 1g/sq cm is shifted into and out the regolith during each obliquity cycle. It is concluded that this process combined with periodic thermal cycles played a major role in development of the fretted terrain, deflationary features in general, patterned ground, the north polar cap and the layered terrain.

Fanale, F. P.↗

NASA NTRS1984

Improved Nominal Operating Cell Temperature (NOCT) test procedure

A procedure is developed to improve testing of Nominal Operating Cell Temperature (NOCT) as it applies to solar energy conversion modules. NOCT is a direct reflection of module thermal design and is closely related to the representative ambient temperature. It is also a key to array energy production and estimates of module lifetimes. Present NOCT test and evaluation procedures are inconsistent, producing significant scatter. Test refinements would specify a clear sky, the addition of 10% to the insolation level for ground reflection, the addition of a ground emission factor of 0.8 (at 30C ground temperature), an effective wind direction of 135 degrees from the North, and a module tilt of 30 degrees from the horizon.

Wen, L.↗

NASA NTRS1985

The polar caps and the climatic evolution of Mars

Mars and Earth experience quasiperiodic variations in the distribution of incident solar radiation due to secular perturbations in their orbital and axial elements. On Mars, the potential climatic effects of these perturbations are large because the mass of the Martian atmosphere may be determined by the vapor pressures of semipermanent CO2 frost deposits at the poles. The Viking Orbiter observations of the Martian polar caps suggest that the sensitivity of the Martian climate system to the variations in the polar insolation may be considerably reduced by the tendency for polar frost deposits to become brighter with increasing rates of incident solar radiation. This phenomenon can be explained by the tendency for dust particles to sink into CO2 frost at rates that depend on the magnitude of the incident solar flux.

Paige, D. A.↗

NASA NTRS1984

Spectral absorption of solar radiation in cloudy atmospheres A 20/cm model

A radiative transfer model based on both LOWTRAN transmission functions (at a 20/cm resolution), and Monte Carlo simulations of wavelength distributions, is used to determine the spectral absorption of solar radiation in typical water clouds. This yields the relative absorption by the vapor and droplets within each cloud. The results obtained indicate a slightly lower absorption than had previously been found, with boundary layer clouds typically absorbing 9 percent of the terrestrial insolation for an overhead sun. This absorption is strongly dependent on the presence of water vapor above the cloud top and solar zenith angle. Droplets, rather than vapor, are shown to be the dominant absorbers within the cloud except in the absence of water vapor above the cloud top.

Davies, R.↗

NASA NTRS1984

Precession model for the nucleus of periodic Comet Kopff

The existing data base on certain characteristics of the periodic Comet Kopff, a candidate for a NASA rendezvous mission in the 1990s, is summarized. The comet was discovered in 1906. The data are used to calculate limits to the nuclear mass (0.7-1.5 x 10 to the 16th g), equatorial radius (1.26-1.64 km), and a geometric albedo of 0.08. An equatorial rotation velocity of 8.1-10.7 hr is projected. The estimates are highly dependent on the present photometric data, which in turn depend on the insolation rate, which if different than assumed could mean that all parameters would be revised upward significantly.

Sekanina, Z.↗

NASA NTRS1984

A seasonal model of the Saturnian upper troposphere Comparison with Voyager infrared measurements

In the present extension of Cess and Caldwell's (1979) seasonal climate model to the upper troposphere of Saturn, the ring-modulated latitudinal dependence of the insolation, the ring thermal emission, the oblateness and orbital eccentricity of the planet, and the latitudinal variation of the internal heat flux, are taken into account. While these calculations agree with the temperature-latitude profiles retrieved from Voyager IRIS measurements above 0.2-bar pressure level atmospheric strata, the model fails to predict the retrieved temperature-latitude profiles below the 0.3-bar level. This discrepancy may be due to the existence of clouds at these levels.

Bezard, B.↗

NASA NTRS1984

Mobility of water ice on Callisto - Evidence and implications

Voyager images of Callisto reveal evidence for the accumulation of a bright volatile, presumably water ice, on north-facing slopes in the north polar region. The geometry of these accumulations suggests that ice migration in Callistoan high latitudes is dominated by thermal sublimation, controlled by insolation-dependent surface temperature contrasts. Such sublimation-dominated migration may result in the cold-trapping of most of the surface ice in discrete high-albedo regions.

Spencer, J. R.↗

NASA NTRS1985

Terrestrial impactors at geological boundary events - Comets or asteroids?

In the present evaluation of evidence presented to date for a 26-28 million year periodicity in the extinction record and the age of large, well dated terrestrial impact craters, it is noted that no simple, one-to-one relationship emerges between major asteroid and/or comet impacts, siderophile anomalies, and biological extinction events. While impacts may indeed be the major extinction-triggering event in some or even most cases, either other major events, or secondary effects of the impacts, may be the actual extinction-causing mechanism. Long term obscuration of insolation, planetary cooling, or lethal atmospheric pollution may vary among extinctions, depending on the actual state of the planet and its biota during the geological period in question. The source of 28 million year-period asteroidal impactors, moreover, remains unknown and thereby casts doubt on the entire periodicity scenario.

Weissman, P. R.↗

NASA NTRS1985

Universal time dependence of nighttime F region densities at high latitudes

Coincident auroral-zone experiments using three incoherent-scatter radars at widely spaced longitudes are reported. The observational results demonstrate that, during the night, the F layer electron density is strongly dependent on the longitude of the observing site. Ionization patches were observed in the nighttime F region from the Chatanika and EISCAT radars, while densities observed from the Millstone radar were substantially smaller. The electron density within these maxima is larger at EISCAT than at Chatanika. When observed in the midnight sector auroral zone, these densities had a peak density at a high altitude of 360-475 km. The density was maximum when EISCAT was in the midnight sector and minimum when Millstone was in the midnight sector. A minimum in insolation in the auroral zone occurs at the UT when Millstone is in the midnight sector.

De La Beaujardiere, O.↗

NASA NTRS1985

Estimating ocean production from satellite-derived chlorophyll - Insights from the EASTROPAC data set

The EASTROPAC expedition took place in 1967-68 in the eastern tropical Pacific Ocean. Primary production was related to near-surface chlorophyll in these data. Much of the variability in the relation was due to the light-history of the phytoplankton and its photoadaptive state. This was due to changes in the depth of mixing of the surface waters more than changes in insolation. Accurate estimates of production from satellite chlorophyll measurements may require knowledge of the temporal and spatial variation in mixing of this region.

Eppley, R. W.↗

NASA NTRS1985

Criteria for the evaluation of laser solar energy converter systems

Assuming that a parabolic insolation-collection mirror-based solar pumped laser has a collector and heat emitter whose weights are proportional to their areas, and that the weight of the laser is negligible by comparison, the output power/unit weight can be expressed in terms of the efficiencies and working temperatures of the system. This ratio appears to be several times higher for an IBr laser than for one operating on C3F7I, because the solar utilization efficiency is greater for the former despite its lower working temperature.

Harries, W. L.↗

NASA NTRS1985

Electric power - Photovoltaic or solar dynamic?

The design of the power system for supplying the Space Station with insolation-generated electricity is the main Phase B task at NASA-Lewis Center. The advantages and limitations of two types of power systems, the photovoltaic arrays (PV) and the solar dynamic system (SD), are discussed from the points of view of cost, overall systems integration, and growth. Subsystems of each of these options are described, and a sketch of a projected SD system is shown. The PV technology is well developed and proven, but its low efficiency calls for solar arrays of large areas, which affect station dynamics, control, and drag compensation. The SD systems would be less costly to operate than VP, and are more efficient, needing less deployed area. The major drawback of the SD is its infancy. The conservative and forgiving designs for some of its components must still be created and tested, and the development risks assessed.

Thomas, R. L.↗

NASA NTRS1985

Temporal variations of the tropical tropopause characteristics

Results of a detailed study of tropopause characteristics at eleven Indian stations spread over a latitude range of 8.4 deg N to 28.6 deg N, using the data obtained during the period 1969 to 1978, are presented and discussed. This study reveals that the semiannual component in TP(T) (the tropopause potential temperature) can mainly be accounted by the corresponding variation on the solar insolation, whereas the annual component is greatly affected by the monsoon phenomenon, which is a large-scale annual one. During this period, the large-scale cloud cover would reduce the convective activity. Again, the annual components of TP(T) and lower stratospheric (18 km) potential temperature show a phase difference of about 6 months, except at the extratropical stations and about 2 to 3 months in the case of semiannual component. At extratropical stations the phase difference is much less, indicating the influence of convective process in the lower stratosphere.

Murthy, B. V. K.↗

NASA NTRS1985

Middle atmosphere tides

The recent direction of theoretical and observational research in middle atmosphere tides is reviewed. The diurnal tide has received considerable emphasis, including observations of evanescent components at high latitudes, numerical simulations of nonmigrating propagating components due to longitudinally varying water vapor insolation absorption in the troposphere, and implications and origins of unsteadiness in tidal oscillations over periods of days. Recent analyses of Nimbus 7 LIMS temperatures and partial reflection drift measurements of neutral winds in the tropical mesosphere have also emphasized the diurnal propagating tide. A description of the Atmospheric Tides Middle Atmosphere Program (ATMAP) and an overview of ATMAP campaign results are also presented.

Forbes, J. M.↗

NASA NTRS1985

Wave-mean flow interaction in the NCAR stratospheric general circulation model

A version of the NCAR General Circulation Model has been developed which extends from the surface into the mesosphere. The model was forced by climatological January sea surface temperatures and insolation and gives a fairly reasonable simulation of the troposphere and stratosphere. The transformed Eulerian formation is used to examine the interaction of the eddies with the mean flow in the winter hemisphere. The essence of the transformed Eulerian formation is an attempt to distinguish between the mean meridional circulation driven by diabatic heating and that driven by eddies. The net effect of eddies can then be determined, and is given by the Eliassen-Palm (EP) flux divergence. In practice, this method works reasonably well but is far from perfect. For instance, in the absence of eddy forcing, the winter stratosphere would go to radiative equilibrium and there would be no diabatic heating to drive a mean meridional circulation.

Boville, B. A.↗

NASA NTRS1986

Tidal coupling with the lower atmosphere (invited review)

The various ways are reviewed in which propagating tidal components excited in the mesophere and below affect the structure of the thermosphere and ionosphere above 100 km. Dynamo effects are not treated here. The physical processes affecting the propagation of upward propagating tides are examined and how they are interrelated in the context of a numerical model. Propagating diurnal and semidiurnal tides which reach thermospheric heights are excited primarily by insolation absorption by tropospheric water vapor (0 to 5 km) and stratospheric/mesospheric ozone (40 to 60 km), respectively. Simulation of these oscillations requires consideration of mean zonal winds and meridional temperature gradients, and the damping effects of turbulent and molecular dissipation, radiative cooling, and ion drag. These effects must be considered on a spherical rotating atmosphere extending from the ground to above 300 km, as they are in the model developed by Forbes depicted schematically.

Forbes, J. M.↗