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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Frost Growth and Densification on a Flat Surface in Laminar Flow with Variable Humidity

Experiments are performed concerning frost growth and densification in laminar flow over a flat surface under conditions of constant and variable humidity. The flat plate test specimen is made of aluminum-6031, and has dimensions of 0.3 mx0.3 mx6.35 mm. Results for the first variable humidity case are obtained for a plate temperature of 255.4 K, air velocity of 1.77 m/s, air temperature of 295.1 K, and a relative humidity continuously ranging from 81 to 54%. The second variable humidity test case corresponds to plate temperature of 255.4 K, air velocity of 2.44 m/s, air temperature of 291.8 K, and a relative humidity ranging from 66 to 59%. Results for the constant humidity case are obtained for a plate temperature of 263.7 K, air velocity of 1.7 m/s, air temperature of 295 K, and a relative humidity of 71.6 %. Comparisons of the data with the author's frost model extended to accommodate variable humidity suggest satisfactory agreement between the theory and the data for both constant and variable humidity.

Kandula, M.↗
NASA NTRS1974

Mars - The case against permanent CO2 frost caps

Leighton and Murray (1966) have argued that there is a polar reservoir of solid CO2 on Mars that lasts throughout the year and whose vapor pressure determines the mean partial pressure of CO2 in the atmosphere. This model is discussed in the light of recent data, and several difficulties emerge. First, such a system might be unstable, owing to the tendency of poleward heat transport to increase with atmospheric pressure. Second, the annual retreat of the CO2 frost cover would be slower according to the model than that observed. Moreover, the observations seem to indicate that the residual polar cap that lasts throughout the year is composed of water ice rather than CO2. Finally, observations of water vapor in the atmosphere appear to be inconsistent with a permanent CO2 cold trap in continuous existence for many years. These difficulties hold also for a CO2 reservoir buried by water ice and for a hydrated CO2 clathrate.

Ingersoll, A. P.↗
NASA NTRS1975

A laboratory study of the diffuse reflectance spectra of frosts occurring on astronomical objects

Mechanical, optical, and operating properties of an experiment chamber are examined and possible sample contamination difficulty is explained. The mechanical and operational characteristics of this apparatus are well suited for the study of the reflectance spectra of frosts. The infrared energy available at the detector is low and steps to increase the energy and the responsivity of the detector were taken. The problem of a standard diffuse reflector which is useful in the far ultraviolet region is considered and it is suggested that bright gold be used as the standard.

Glaser, F. M.↗
NASA NTRS1975

Evidence for frost on Rhea's surface

We have observed Rhea (S5) at 1.6 and 2.2 microns at Mt. Wilson using the Caltech photometer on the 1.52 m and 2.54 m telescopes. The infrared spectral reflectances relative to 0.55 micron are 0.8 at 1.65 micron and 0.6 at 2.2 microns. Such absorption bands in the near infrared are not consistent with spectra of most rocks or minerals; even carbonaceous chondritic materials have nearly flat reflectances over this spectral region. Frosts, however, have strong absorption bands in the 1-3 microns region. In particular, the broadband infrared reflectances of Rhea are similar to those of the Galilean satellites Europa (J2) and Ganymede (J3) and also the rings of Saturn. Rhea's low density, high albedo and relatively flat reflectance from 0.3 to 1.1 micron as well as the low infrared reflectances reported here are consistent with the presence of water ice on Rhea's surface.

Johnson, T. V.↗
NASA NTRS1976

Further laboratory study of the diffuse reflectance spectra of frosts occurring on astronomical objects

Oligoclase and bloedite, two mined samples, have been investigated, and the diffuse reflectance spectra are presented. These data are for powdered material, 50 microns to 5 microns size mixture, cooled to 160 K. The reflectivity of the oligoclase sample was also measured at room temperature, about 290 K, and the results at these two temperatures do indicate some tentative differences. A frost of ordinary water was prepared and its spectral reflectance is presented. This result compares reasonably well with measurements made by other investigators.

Glaser, F. M.↗
NASA NTRS1979

Mars south polar spring and summer temperatures - A residual CO2 frost

Viking infrared thermal mapper (IRTM) energy measurements over the Mars south polar cap throughout the Martian spring and summer revealed complex spatial, spectral, and temporal variations. High albedos did not directly correspond with low temperatures, and as the cap shrank to its residual position, it maintained large differences in brightness temperature between the four IRTM surface-sensing bands at 7, 9, 11, and 20 microns. The late summer infrared spectral pattern can be matched by a surface consisting of CO2 frost with 20 micron emissivity of 0.8 and about 6% dark, warm soil under a dusty atmosphere of moderate infrared opacity and spectral properties similar to those measured for the Martian global dust storms. Low temperature, the absence of appreciable water vapor in the south polar atmosphere, and the absence of surface warming expected if H2O were to become exposed, all imply that the residual south polar cap was covered by solid CO2.

Kieffer, H. H.↗
NASA NTRS1980

Surface temperatures and retention of H2O frost on Ganymede and Callisto

Surface temperatures and ice evaporation rates are calculated for Ganymede and Callisto as functions of latitude, time of day, and albedo, according to a model that uses surface thermal properties determined by eclipse radiometry and albedos determined from photometrically decalibrated Voyager images. The difference in temperature between Ganymede and Callisto is not great enough to account for the lack of bright polar caps on Callisto, which seems instead to reflect a real deficiency in the amount of available water frost relative to Ganymede. The temperature difference between Ganymede's grooved and cratered terrains also cannot account for the high concentration of bright ray craters in the former, suggesting that an internal geologic process has enriched the grooved terrain in ice content relative to the cratered terrain.

Squyres, S. W.↗
NASA NTRS1983

Frost Forecasting for Fruitgrowers

Progress in forecasting from satellite data reviewed. University study found data from satellites displayed in color and used to predict frost are valuable aid to agriculture. Study evaluated scheme to use Earth-temperature data from Geostationary Operational Environmental Satellite in computer model that determines when and where freezing temperatures endanger developing fruit crops, such as apples, peaches and cherries in spring and citrus crops in winter.

Martsolf, J. D.↗
NASA NTRS1981

Application of Satellite Frost Forecast Technology to Other Parts of the United States

Thermal infrared data taken from the GOES satellite over a period of several hours was color enhanced by computer according to temperature. The varying temperatures were then used to assist in frost forecasting. Input from Michigan and Pennsylvania to the cold climate mapping project is emphasized in the report of the second year's activities of a two year effort.

Martsolf, J. D.↗
NASA NTRS1981

A Satellite Frost Forecasting System for Florida

Since the first of two minicomputers that are the main components of the satellite frost forecast system was delivered in 1977, the system has evolved appreciably. A geostationary operational environmental satellite (GOES) system provides the satellite data. The freeze of January 12-14, 1981, was documented with increasing interest in potential of such systems. Satellite data is now acquired digitally rather than by redigitizing the GOES-Tap transmissions. Data acquisition is now automated, i.e., the computers are programmed to operate the system with little, if any, operation intervention.

Martsolf, J. D.↗