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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

H2 S3(1) and S4(1) transitions in the atmospheres of Neptune and Uranus - Observations and analysis

The present observational results for Neptune's S3(1) and S4(1) H2 lines show the former line's measured equivalent width to be the same as for this feature in Uranus, repeating the equality already established between the two planets for the latter feature. It is also noted that the observed ratio of the H2 S3(0)/S3(1) lines for Neptune's atmosphere is reproduced by models belonging to the family of models created by Baines and Smith (1990); by comparison with the earlier Uranus models of Baines and Bergstrahl (1986), the greater continuum absorption of Neptune is responsible for the increased S3(0)/S3(1) line ratio near 0.82 microns.

Smith, Wm. Hayden↗
NASA NTRS1987

Uranus' (3-0) H2 quadrupole line profiles

Spectra of Uranus' S3(0) and S3(1) H2 quadrupole lines, obtained during the 1978-1980 apparitions, are analyzed, and are found to require the presence of a deep cloud. Modifications of the Baines and Bergstralh (1986) standard model, including an additional haze layer above the 16-km-am H2 level which contains strongly absorbing particles, are needed to fit the observations. For a Rayleigh phase function, such a haze (uniformly mixed with the gas above this level) would have an absorption optical depth of 0.16 and a single scattering particle albedo of 0.30. This modification would imply a fraction of normal H2 equal to 0.25 + or - 0.10, in agreement with the Baines and Bergstralh standard model.

Trafton, L.↗
NASA NTRS1983

Interpretation of the 6818.9-A methane feature observed on Jupiter, Saturn, and Uranus

High-resolution (0.1-A) spectra of the 6818.9-A methane feature obtained for Jupiter, Saturn, and Uranus by Baines, Schempp, and Smith (1969) are modeled using a doubling and adding code after Hansen (1983). The feature's rotational quantum number is estimated using the relatively homogeneous atmosphere of Saturn, with only J = 0 and J = 1 fitting the observational constraints. The aerosol content within Saturn's northern temperate region is shown to be substantially less than at the equator, indicating a haze only half as optically thick. Models of Jupiter's atmosphere are consistent with the rotational quantum-number assignment. Synthetic line profiles of the 6818.9-A feature observed on Uranus reveal that a substantial haze exists at or above the methane condensation region with an optical depth eight times greater than previously reported. Seasonal effects are indicated. The methane column abundance is 5 + or - 1 km-am. The mixing ratio of methane to hydrogen within the deep unsaturated region of the planet is 0.045 + or - 0.025, based on an H2 column abundance of 240 + or - 60 km-am (Smith, Macy, and Pilcher /1980/), thus indicating that methane comprises between one-sixth and one-half of the planet's mass. However, proper reevaluation of H2 quadrupole features accounting for the haze reported here may significantly reduce the relative methane abundance.

Baines, K. H.↗
NASA NTRS1990

Absorption coefficients for the 6190-A CH4 band between 290 and 100 K with application to Uranus' atmosphere

A novel laser intracavity photoacoustic spectroscopy method allowing high sample control accuracy due to the small sample volume required has been used to obtain absorption coefficients for the CH4 6190 A band as a function of temperature, from 290 to 100 K. The peak absorption coefficient is found to increase from 0.6 to 1.0/cm, and to be accompanied by significant band shape changes. When used to further constrain the Baines and Bergstrahl (1986) standard model of the Uranus atmosphere, the low-temperature data yield an excellent fit to the bandshape near the 6190 A band's minimum.

Smith, Wm. Hayden↗
NASA NTRS2001

Functional properties of slow and fast gastrocnemius muscle fibers after a 17-day spaceflight

The purpose of this investigation was to study the effects of a 17-day spaceflight on the contractile properties of individual fast- and slow-twitch fibers isolated from biopsies of the fast-twitch gastrocnemius muscle of four male astronauts. Single chemically skinned fibers were studied during maximal Ca2+-activated contractions with fiber myosin heavy chain (MHC) isoform expression subsequently determined by SDS gel electrophoresis. Spaceflight had no significant effect on the mean diameter or specific force of single fibers expressing type I, IIa, or IIa/IIx MHC, although a small reduction in average absolute force (P(o)) was observed for the type I fibers (0.68 +/- 0.02 vs. 0.64 +/- 0.02 mN, P < 0.05). Subject-by-flight interactions indicated significant intersubject variation in response to the flight, as postflight fiber diameter and P(o) where significantly reduced for the type I and IIa fibers obtained from one astronaut and for the type IIa fibers from another astronaut. Average unloaded shortening velocity [V(o), in fiber lengths (FL)/s] was greater after the flight for both type I (0.60 +/- 0.03 vs. 0.76 +/- 0.02 FL/s) and IIa fibers (2.33 +/- 0.25 vs. 3.10 +/- 0.16 FL/s). Postflight peak power of the type I and IIa fibers was significantly reduced only for the astronaut experiencing the greatest fiber atrophy and loss of P(o). These results demonstrate that 1) slow and fast gastrocnemius fibers show little atrophy and loss of P(o) but increased V(o) after a typical 17-day spaceflight, 2) there is, however, considerable intersubject variation in these responses, possibly due to intersubject differences in in-flight physical activity, and 3) in these four astronauts, fiber atrophy and reductions in P(o) were less for slow and fast fibers obtained from the phasic fast-twitch gastrocnemius muscle compared with slow and fast fibers obtained from the slow antigravity soleus [J. J. Widrick, S. K. Knuth, K. M. Norenberg, J. G. Romatowski, J. L. W. Bain, D. A. Riley, M. Karhanek, S. W. Trappe, T. A. Trappe, D. L. Costill, and R. H. Fitts. J Physiol (Lond) 516: 915-930, 1999].

NASA Experiment Number 8913020 1/2↗
NASA NTRS1986

Activities of the Department of Astronomy and McDonald Observatory of the University of Texas at Austin

McDonald Observatory of the University of Texas at Austin reports on its activities during the period 1 Jan. 1986 to 30 June 1986. Extensive observations of Halley's Comet were obtained. The comet exhibited large variability; moreover, its variability was much more rapid than can be accounted for by water vaporization as the sole controller of activity. Jupiter satellite Io's atmosphere was found to be distended by more than the equilibrium scale height but less than for unimpeded streaming into space. The atmosphere is at least temporarily bound to IO. Uranus' (3-0) H2 quadrupole line shapes require a modification of Baines and Bergstralh's standard model which incorporates at high altitude absorbing haze in addition to the lower haze layer. A fraction of normal H2 equal to 0.25 + or 0.10 is derived, in good agreement with the standard model. This result is unchanged when the preliminary temperature structure derived by the Voyager Radio Occultation Experiment is used instead of Appleby's model c. Out of the six Pluto-Charon mutual events observed this year, data were obtained on four. Preliminary analysis is yielding improved estimates for the diameters, masses, densities, and albedos of these objects.

Smith, H. J.↗
NASA NTRS1990

The ultraviolet continuum albedo of Uranus

A radiative transfer code explicitly treating the Raman scattering of solar protons by H2 is presently used to analyze the Uranus geometric albedo in the 2000-5000 A range. The Baines and Bergstralh (1986) baseline model used reproduces the geometric albedo peak produced by Raman scattering filling of solar absorption line cores, but is found to be excessively bright for wavelengths below 2400 A. This discrepancy is resolvable through inclusion of an absorbing stratospheric haze layer, and results are thereby obtained which are consistent with the Pollack et al. (1987) model, in which aerosols are generated stratospherically through photochemical effects on hydrocarbons.

Cochran, William D.↗
NASA NTRS2006

On the Discovery of CO Nighttime Emissions on Titan by Cassini/VIMS: Derived Stratospheric Abundances and Geological Implications

We present a quantitative analysis of CO thermal emissions discovered on the nightside of Titan by Baines et al. [2005. The atmospheres of Saturn and Titan in the near-infrared: First results of Cassini/VIMS. Earth, Moon, and Planets, 96, 119-147] in Cassini/VIMS spectral imagery. We identify these emission features as the P and R branches of the 1-0 vibrational band of carbon monoxide (CO) near 4.65 microns. For CH3D, the prominent Q branch of the nu(2) fundamental band of CH3D near 4.55 microns is apparent. CO2 emissions from the strong nu(3) vibrational band are virtually absent, indicating a CO2 abundance several orders of magnitude less than CO, in agreement with previous investigations. Analysis of CO emission spectra obtained over a variety of altitudes on Titan's nightside limb indicates that the stratospheric abundance of CO is 32 +/- 15 ppm, and together with other recent determinations, suggests a vertical distribution of CO nearly constant at this value from the surface throughout the troposphere to at least the stratopause near 300 km altitude. The corresponding total atmospheric content of CO in Titan is similar to 2.9 +/- 1.5 x 10(exp 14) kg. Given the long lifetime of CO in the oxygen-poor Titan atmosphere (similar to 0.5-1.0 Gyr), we find a mean CO atmospheric production rate of 6 +/- 3 x 10(exp 5) kg yr(exp -1). Given the lack of primordial heavy noble gases observed by Huygens [Niemann et al., 2005. The abundances of constituents of Titan's atmosphere from the GCMS on the Huygens probe. Nature, 438, 779-784], the primary source of atmospheric CO is likely surface emissions. The implied CO/CH4 mixing ratio of near-surface material is 1.8 +/- 0.9 x 10(exp -4), based on an average methane surface emission rate over the past 0.5 Gyr of 1.3 x 10(exp -13) gm cm(exp -2) s(exp -1) as required to balance hydrocarbon haze production via methane photolysis [Wilson and Atreya, 2004. Current state of modeling the photochemistry of Titan's mutually dependent atmosphere and ionosphere. J. Geophys. Res. 109, E06002 Doi: 10.1029/2003JE002181]. This low CO/CH4 ratio is much lower than expected for the sub-nebular formation region of Titan and supports the hypothesis [e.g., Atreya et al., 2005. Methane on Titan: photochemical-meteorological-hydrogeochemical cycle. Bull. Am. Astron. Soc. 37, 735] that the conversion of primordial CO and other carbon-bearing materials into CH4-enriched clathrate-hydrates occurs within the deep interior of Titan via the release of hydrogen through the serpentinization process followed by Fischer-Tropsch catalysis. The time-averaged predicted emission rate of methane-rich surface materials is approximately 0.02 km(exp 3) yr (exp -1), a value significantly lower than the rate of silicate lava production for the Earth and Venus, but nonetheless indicative of significant geological processes reshaping the surface of Titan.

carbon compounds↗
NASA NTRS1972

The effect of gravity induced free convection upon the melting phenomena of a finite paraffin slab for thermal control

Two theoretical models were developed to predict the thermal response of the phase change material to a given hot plate temperature. A two-dimensional pure conduction model was developed to predict the melting of the phase change material when heat transfer was a function of conduction. A combined conduction-convection model, also two-dimensional, was developed to predict the phase change phenomena when heat transfer was a function of conduction and gravity-induced free convection. Both models were solved using explicit finite difference approximations on a digital computer. The experimental equipment consisted of a rectangular cell utilizing a heat chamber, an expansion chamber, and a test chamber; a sixteen channel multipoint recorder, and a fluid flow system. The recorder monitered hot and cold plate temperatures and interior node temperatures at two second intervals. A comparison of theoretical temperature profiles and experimental temperature profiles is presented for six runs at various angles of inclination of the test cell with respect to the horizontal direction. A detailed discussion of results is presented.

Bain, R. L.↗
NASA NTRS1972

An experimental and theoretical investigation of the liquefaction dynamics of a phase change material in a normal gravity environment

Experimental and theoretical investigations were undertaken to determine the role of gravity-induced free convection upon the liquefaction dynamics of a cylindrical paraffin slab under normal gravity conditions. The experimental equipment consisted of a test cell, a fluid-loop heating system, and a multipoint recorder. The test chamber was annular in shape with an effective radius of 1.585 cm and a length of 5.08 cm. The heating chamber was a 1.906 cm diameter tube going through the center of the test chamber, and connected to the fluid loop heating system. All experimental runs were made with the longitudinal axis of the test cell in the vertical direction to insure that convection was not a function of the angular axis of the cell. Ten melting runs were made at various hot wall temperatures. Also, two pure conduction solidification runs were made to determine an experimental latent heat of fusion.

Bain, R. L.↗