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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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9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Preliminary evaluation of the role of K2S in MHD hot stream seed recovery

Results are presented for recent analytical and experimental studies of the role of K2S in MHD hot stream seed recovery. The existing thermodynamic data base was found to contain large uncertainties and to be nonexistent for vapor phase K2S. Knudsen cell mass spectrometric experiments were undertaken to determine the vapor species in equilibrium with K2S(c). K atoms and S2 molecules ere found to be the major vapor phase species in vacuum, accounting for greater than 99 percent of the vapor phase. Combustion gas deposition studies using No. 2 Diesel fuel were also undertaken and revealed that condensed phase K2SO3 may potentially be an important compound in the MHD stream at near-stoichiometric combustion.

Bennett, J. E.↗
DOE OSTI2020

Materials Data on K2S by Materials Project

K2S is Fluorite structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. K1+ is bonded to four equivalent S2- atoms to form a mixture of edge and corner-sharing KS4 tetrahedra. All K–S bond lengths are 3.23 Å. S2- is bonded in a body-centered cubic geometry to eight equivalent K1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2S by Materials Project

K2S crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to five equivalent S2- atoms to form distorted KS5 trigonal bipyramids that share corners with twelve equivalent KS6 octahedra, corners with eight equivalent KS5 trigonal bipyramids, edges with six equivalent KS5 trigonal bipyramids, and faces with six equivalent KS6 octahedra. The corner-sharing octahedra tilt angles range from 31–60°. There are a spread of K–S bond distances ranging from 3.06–3.65 Å. In the second K1+ site, K1+ is bonded to six equivalent S2- atoms to form distorted KS6 octahedra that share corners with twelve equivalent KS6 octahedra, corners with twelve equivalent KS5 trigonal bipyramids, edges with six equivalent KS6 octahedra, faces with two equivalent KS6 octahedra, and faces with six equivalent KS5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 51°. There are four shorter (3.56 Å) and two longer (3.58 Å) K–S bond lengths. S2- is bonded in a 3-coordinate geometry to eleven K1+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1982

Vaporization thermodynamics of K2S and K2SO3

The vaporization reactions, vapor pressures, and thermodynamics of potassium sulfide and potassium sulfite were studied for purposes of providing fundamental data for the seed cycle in magnetohydrodynamic electric power generation. Rate of effusion studies, supported by tube furnace experiments, X-ray powder diffraction, mass spectrometry and appropriate chemical analyses and tests, revealed that potassium sulfite disproportionates at high temperatures to form potassium sulfide and potassium sulfate. Potassium sulfide was observed to vaporize incongruently, the initial vapors beng predominantly potassium atoms, with minor species being S2 and various K-S molecules. The ratio of K/S2 in the vapor is very large initially and decreases steadily with prolonged heating. Several materials were evaluated for purposes of containing K2S/K2SO3 at temperatures or = 800 C: Pt, Mo, W, quartz, machinable glass, BN, high density graphite, pyrolytic coated graphite, and alumina. Of these, only alumina was observed to be chemically inert to both K2S but reacted with K2SO3. The other materials were not suitable for either substance. Thermodynamic calculations based on measured vapor pressures and approximate free energy functions are described. Results from isothermal total mass loss experiments and from thermogravimetric experiments are also included.

Bennet, J. E.↗
NASA NTRS2016

Chaos in Kepler's Multiple Planet Systems and K2s Observations of the Atmospheres of Uranus Neptune

More than one-third of the 4700 planet candidates found by NASA's Kepler spacecraft during its prime mission are associated with target stars that have more than one planet candidate, and such "multis" account for the vast majority of candidates that have been verified as true planets. The large number of multis tells us that flat multiplanet systems like our Solar System are common. Virtually all of the candidate planetary systems are stable, as tested by numerical integrations that assume a physically motivated mass-radius relationship, but some of the systems lie in chaotic regions close to instability. The characteristics of some of the most interesting confirmed Kepler multi-planet systems will be discussed. The Kepler spacecraft's 'second life' in theK2 mission has allowed it to obtain long time-series observations of Solar System targets, including the giant planets Uranus & Neptune. These observations show variability caused by the chaotic weather patterns on Uranus & Neptune.

planet candidates↗
NASA NTRS1983

Thermodynamics of the potassium-sulfur-oxygen and related systems

The chemical reactions which occur when potassium sulfide, K2S, and potassium sulfite, K2SO3, are heated at temperatures where their vapor pressures are significant, were studied and the vapor pressures and the partial pressures of the chemical products were measured. Mass spectrometry of the vapor of potassium sulfide revealed only K(g). X-ray studies of the solid residues from vaporization experiments revealed K2S2(s) and chemical analyses of the same solid residues showed that the residues approached a composition K2Sx with x in the range 3-4. Vapor pressure of K2S was measured by simultaneous Knudsen-effusion and torsion-effusion (SKETE) in crucibles of aluminum oxide and of graphite. In each such experiment, the vapor pressures agreed initially, but then the apparent pressure by Knudsen-effusion increased suddenly and remained much greater than that by torsion-effusion for the remainder of the experiment. Results of third-law analysis of the torsion pressures imply a delta H (298K) of formation of K2S(s) of -364 + or - 12 kJ/mol. Vapor pressures over K2SO3(s) were measured by simultaneous Knudsen and torsion-effusion and by mass spectrometry. The vapor pressures of both K2S2O5(s) and K2SO3(s) were nonreproducible at a given temperature due to the vaporization reactions of the materials being irreversible under conditions in effusion cells.

Edwards, J. G.↗
NASA NTRS1979

Spectral evidence for sublimates and adsorbates on Io

The results of laboratory studies of sulfur adsorbates and sublimates are presented to explain the observed spectral reflectance of Io. The hemispherical and bidirectional spectral reflectances of typical sublimate phases of Na2S, NaHS, K2S and mixtures thereof with free sulfur were measured under varied temperature and particle-irradiation conditions. It is found that Na2S, K2S and NaHS have absorption bands at all the key wavelengths of Io's spectrum in the UV and visible ranges, and as a group can account for much of Io's spectral reflectance in the 0.25- to 5.0-micron range. It is also concluded that adsorbed gases, possibly H2S and SO2, believed to be formed by reactions in the sublimate phase, also contribute to the IR spectrum of Io's surface.

Nash, D. B.↗
NASA NTRS1979

Crystal growth of sulfide materials from alkali polysulfide liquids

The fluids experiment system was designed for low temperature solution growth, nominally aqueous solution growth. The alkali polysulfides, compositions in the systems Na2S-S and K2S-S form liquids in the temperature range of 190 C to 400 C. These can be used as solvents for other important classes of materials such as transition metal and other sulfides which are not soluble in aqueous media. Among these materials are luminescent and electroluminescent crystals whose physical properties are sensitive functions of crystal perfection and which could, therefore, serve as test materials for perfection improvement under microgravity conditions.

White, W. B.↗
NASA NTRS2016

Campaign 9 of the K2 Mission: Observational Parameters, Scientific Drivers, and Community Involvement for a Simultaneous Space- and Ground-based Microlensing Survey

K2ʼs Campaign 9 (K2C9) will conduct a approximately 3.7 sq. deg survey toward the Galactic bulge from 2016 April 22 through July 2 that will leverage the spatial separation between K2 and the Earth to facilitate measurement of the microlens parallax Pi(sub E) for approximately greater than 170 microlensing events. These will include several that are planetary in nature as well as many short-timescale microlensing events, which are potentially indicative of free-floating planets (FFPs). These satellite parallax measurements will in turn allow for the direct measurement of the masses of and distances to the lensing systems. In this article we provide an overview of the K2C9 space- and ground-based microlensing survey. Specifically, we detail the demographic questions that can be addressed by this program, including the frequency of FFPs and the Galactic distribution of exoplanets, the observational parameters of K2C9, and the array of resources dedicated to concurrent observations. Finally, we outline the avenues through which the larger community can become involved, and generally encourage participation in K2C9, which constitutes an important pathfinding mission and community exercise in anticipation of WFIRST.

K2s Campaign 9 (K2C9)↗