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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS2026

Polarized Resonant Soft X-ray Scattering (P-RSoXS) as a New Technique for Characterizing Amorphous Astromaterials

In the coming years, samples will be returned from several asteroids, the lunar surface, and the first material returned directly from the Martian surface. Previous in-situ and remote studies indicate these samples will contain abundant amorphous or weakly crystalline materials. However, detailed characterization and quantification of these amorphous materials remains challenging. Conventional techniques, including electron microscopy and X-ray diffraction, provide important information on material structure, but are generally limited to crystalline materials. Polarized resonant soft X-ray scattering (P-RSoXS) is a synchrotron-based X-ray scattering technique that has been used to characterize and quantify weakly crystalline systems, including soft materials. This research aims to translate this technique to geologic and extraterrestrial materials, building off the knowledge of using P-RSoXS to interrogate soft materials. P-RSoXS is well-suited to interrogate geologic materials, which are often multiphase, heterogeneous systems with crystalline and amorphous components, and domain sizes on the order of tens of nanometers. It is anticipated that future work will help reveal new chemical and structural information in geologic materials. Maturation of this preliminary work to develop P-RSoXS to characterize astromaterial-relevant samples will provide new understanding of the secondary processes responsible for the development of amorphous astromaterials and further elucidate our knowledge of the geologic history and past alteration processes.

Joshua H Litofsky↗
NASA NTRS1993

Two techniques for measuring locomotion impact forces during zero G

A load-cell-instrumented treadmill mated to a Kistler force plate was used to investigate two methods of force measurement instrumentation during treadmill ambulation in zero g, created by parabolic flight on NASA's KC-135 aircraft. Current spaceflight treadmills do not have adequate instrumentation to determine the resultant foot impact force applied during restrained ambulation. Accurate measurement of foot-ground reaction forces is critical in attaining proper one-g loading, therefore ensuring proper musculoskeletal conditioning. Treadmill instrumentation and force plate measurements were compared for frequency response and linearity. Locomotion impact data were also collected under one-g laboratory settings and in Keplerian flight. The first resonant frequency for both techniques was found to be well above the primary frequency content of the locomotive forces. Peak impact forces measured by the two systems compared to within 10 percent.

Greenisen, Michael C.↗
NASA NTRS1967

Liquid propulsion

The Resonant Combustion Program uses a bombing technique to precipitate the transition from the steady state to the resonant, or oscillatory, rocket combustion mode. The initial pressure disturbance produced by the high-explosive device, when exploded in a nonreactive environment of cold N2 gas, is a blast-wave having an initial amplitude of several thousand psi (within a radius of approximately one inch from the bomb case) which is still several hundred psi strong even at a radius of 4 to 5 in. The use of such a severe triggering disturbance has brought up the question of whether or not the violent sustained oscillatory mode observed in this program is forced by the character of the initial disturbance itself.

INJECTOR↗
NASA NTRS1990

Bias and uncertainty in the absorption emission measurement of atomic sodium density in the SSME exit plane

The measurement of atomic sodium concentration in the TTB 019 firing of April 1990 is significant in that it represents the first measurement of density at the exit plane of the space shuttle main engine. The knowledge of the sodium density, combined with the certainty that the exit plane of the plume is optically thin at the sodium D-line wavelengths, provides essential information for evaluation of diagnostic techniques using sodium atoms, such as resonant Doppler velocimetry for temperature, pressure, and velocity through high resolution fluorescent lineshape analysis. The technique used for the sodium atom line transmission (SALT) measurements is that of resonant absorption emission using a hollow cathode lamp as the reference source. Through the use of two-dimensional kinetic (TDK) predictions of temperature and density for the flight engine case and radiative transfer calculations, this line-of-sight spectrally integrated transmission indicates a sodium atom concentration, i.e., mole fraction, of 0.91e-10. The subject of this paper is the assumptions and measurement uncertainties tied into the calculation. Because of the narrow shape of the source emission, the uncertainties in the absorption profile could introduce considerable bias in the measurement. The following were investigated: (1) the inclusion of hyperfine splitting of the D-lines in the calculation; (2) the use of the flight engine predictions of plume temperature and density versus those for the large throat engine; (3) the assumption of a Gaussian, i.e., Doppler, distribution for the source radiance with a temperature of 400 K; (4) the use of atomic collisional shift and width values for the work by Jongerius; and (5) a Doppler shift for a 7 degree outward velocity vector at the plume edge. Also included in the study was the bias introduced by an uncertainty in the measurement of the D1/D2 line ratio in the source.

Bauman, Leslie E.↗
NASA NTRS1971

Experimental and computer studies of the radiation effects in silicon solar cells

A summary of selected experimental results obtained on lithium-diffused bulk silicon is presented. Particular emphasis is placed on the radiation-induced degradation and thermal annealing of minority carriers in bulk silicon because solar cell output is related to the minority carrier lifetime. The temperature dependence of the minority carrier lifetime indicates the density and energy levels of the recombination centers and provides clues to their identity. Electron spin resonance and infrared absorption techniques are used to investigate the introduction and anneal of three specific radiation induced defects, which are thought to contribute to the recombination process.

Leadon, R. E.↗
NASA NTRS1972

Niobium hyperfine structure in crystal calcium tungstate

A study of the niobium hyperfine structure in single crystal calcium tungstate was made by the combination of the technique of electron paramagnetic resonance and electron nuclear double resonance (EPR/ENDOR). The microwave frequency was about 9.4 GHz and the radio frequency from 20MHz to 70 MHz. The rare earth ions Nd(3+), U(3+), or Tm(3+) were added as the charge compensator for Nb(5+). To create niobium paramagnetic centers, the sample was irradiated at 77 deg K with a 10 thousand curie Co-60 gamma source for 1 to 2 hours at a dose rate of 200 K rads per hour and then transferred quickly into the cavity. In a general direction of magnetic field, the spectra showed 4 sets of 10 main lines corresponding to 4 nonequivalent sites of niobium with I = 9/2. These 4 sets of lines coalesced into 2 sets of 10 in the ab-plane and into a single set of 10 along the c-axis. This symmetry suggested that the tungsten ions are substituted by the niobium ions in the crystal.

Tseng, D. L.↗
NASA NTRS1974

Electron paramagnetic resonance of several lunar rock samples

The results are presented of investigating lunar rock samples returned by the Luna 16 automatic station, using electron paramagnetic resonance (EPR). The EPR technique makes it possible to detect paramagnetic centers and investigate their nature, with high sensitivity. Regolith (finely dispersed material) and five particles from it, 0.3 mm in size, consisting mostly of olivine, were investigated with EPR.

Marov, P. N.↗
NASA NTRS1975

Vector plotting as an indication of the approach to flutter

A binary flexure-torsion analysis was made to check theoretically a method for predicting flutter which depends on plotting vectorially the amplitudes of response relative to the exciting force and extracting the relevant damping rate. The results of this calculation are given in graphs both of the vector plots themselves and of the estimated damping rate against forward speed. The estimated damping rates are compared with calculated values. The method has the advantage that in a flight flutter test damping can be estimated from continuous excitation records: the method is an extension of the Kennedy and Pancu technique used in ground resonance testing.

Broadbent, E. G.↗
NASA NTRS1977

Apollo-Soyuz O/3P/ and N/4S/ density measurement by UV spectroscopy

The densities of O(3P) and N(4S) at 225 km were determined during the Apollo-Soyuz Test Project by a resonance absorption-fluorescence technique in which O I and N I line radiation produced and collimated on board the Apollo was reflected from the Soyuz back to the Apollo for spectral analysis. The two spacecraft maneuvered so that a range of observation angles of plus or minus 25 deg with respect to the normal to the orbital velocity vector was scanned. The measurements described were made at night on two consecutive orbits at spacecraft separations of 150 and 500 m. The results indicate an O density of 1.15 billion per cu cm (plus or minus 30%), agreeing with mass-spectrometric measurements made under similar conditions, and an N density of 5.6 to 11.2 million per cu cm, in good agreement with recent measurements but suggesting a smaller diurnal variation than predicted by present models.

Donahue, T. M.↗
NASA NTRS1977

Depositional history of core section 74001 - Depth profiles of maturity, FeO, and metal

Samples from every 0.5-cm interval of soil in core section 74001 have been studied by ferromagnetic resonance (FMR) and magnetic techniques. The values of the FMR maturity index show that the 74001 samples are very immature (the index ranges from 0.14 to 0.29 units) and have not seen appreciable, if any, surface exposure since their deposition. In fact, the small amount of fine-grained metal in the 74001 samples is probably not acquired as a result of their exposure to the micrometeoroid flux at the lunar surface. Thus, the black-glass soil of 74001 was deposited very rapidly, probably in a single episode or several closely spaced episodes of lunar fire fountaining. The average concentration of FeO and its standard deviation for all the 74001 samples are 22.5 + or - 0.3 wt.%. Since the FeO concentration is so uniform, no large variations in the major-element chemistry of 74001 are expected, with the possible exception of the volatile elements. The concentration of coarse-grained metal, which is measured magnetically, and its standard deviation are 0.15 + or - 0.01 wt.%. The coarse-grained metal probably precipitated contemporaneously with the silicate and oxide phases in the black-glass droplets.

Morris, R. V.↗
NASA NTRS1978

Validity of modifying Mie theory to describe scattering by nonspherical particles

A calculation procedure has been developed (Chylek et al., 1976) for determining the scattering properties of irregularly shaped, randomly oriented particles. The procedure uses a modified form of the Mie theory for spheres with equivalent cross-sectional areas. The validity of the procedure is examined with reference to the work of Welch and Cox (1978). Particular consideration is given to: (1) the assumption that surface waves constitute the only major difference between scattering by spherical and nonspherical particles, (2) the identification of certain properties of the Mie coefficients with surface waves, and (3) the technique of removing surface waves from the Mie theory. It is concluded that the idea of determining the scattering properties of random orientations of irregular particles by eliminating surface waves from the Mie expansion is valid. It is also found that the technique for removing the resonances leads to the introduction of substantial fictitious absorption.

Acquista, C.↗
NASA NTRS1978

Reactions of OH/+/ and H2O/+/ ions with some diatomic and simple polyatomic molecules

The rate constants and product distributions of the reactions of OH(+) and H2O(+) with some diatomic and simple polyatomic molecules were studied by ion cyclotron resonance (ICR) mass spectrometric techniques. Reaction rates with CO, NO, O2, N2, CO2, H2S, N2O, H2CO, CH4 and CD4 were measured. Charge transfer and proton transfer were generally observed in cases for which the reaction channel is exothermic, but processes involving rearrangement were not found.

Karpas, Z.↗
NASA NTRS1979

The reaction N/4S/ + O3 - An upper limit for the rate constant at 298 K

The reaction of N(4S) atoms with ozone was examined at 298 K using discharge flow and flash photolysis techniques, both coupled with resonance fluorescence detection of N(4S). No reaction was detected in either system, and an upper limit of 5 x 10 to the -16th cu cm/molecule/s was estimated for the rate constant. This is 1000 times lower than the presently accepted value of 5.7 x 10 to the -13th cu cm/molecule/s which is based on a discharge flow-mass spectrometric study of the reaction. Potential complications in the latter experiment are discussed.

Stief, L. J.↗
NASA NTRS1984

Ion-molecule reactions in unsaturated hydrocarbons - Allene, propyne, diacetylene, and vinylacetylene

Ion-molecule reactions in allene, propyne, diacetylene, and vinylacetylene (1-buten-3-yne) have been studied at near-thermal energies by the technique of ion cyclotron resonance mass spectrometry. Rate coefficients and branching ratios are reported for the reactions of C3Hn(+) (n = 1-4) with allene and propyne and for the reactions of C4Hn(+) (n = 0-5) with diacetylene and vinylacetylene. Branching ratios are also given for the reactions of C4Hn(+), C5Hn and C6Hn(+) with propyne and for reactions of C6Hn(+) with diacetylene and vinylacetylene. More than 90 percent of the reactive channels lead to product ions having a larger carbon skeleton than the reactant ion. Evidence for ions with the same m/e ratio having differing reactivities was obtained for C3Hn(+), C6H7(+), and C7H7(+). Ion reaction sequences in allene and propyne were followed at higher pressures (0.0001 torr) to investigate secondary, tertiary, and higher order processes.

Anicich, V. G.↗
NASA NTRS1990

Flow diagnostics by resonant holographic interferometry

This paper describes a resonant-holographic-interferometry (RHI) technique for nonintrusive flow diagnostics, that relies on the index of refraction variation close to a spectral line. This technique makes it possible to obtain interferograms that are species-selective along with quantitative full-field information for the species under study. The application of the RHI technique to flow fields is analyzed together with measurements of flow parameters such as velocity, pressure, and temperature. The advantages of RHI technique over other nonintrusive diagnostic techniques, such as LIF and planar LIF, are discussed.

Sirota, J. M.↗
NASA NTRS1990

High-frequency ac power distribution in Space Station

A utility-type 20-kHz ac power distribution system for the Space Station, employing resonant power-conversion techniques, is presented. The system converts raw dc voltage from photovoltaic cells or three-phase LF ac voltage from a solar dynamic generator into a regulated 20-kHz ac voltage for distribution among various loads. The results of EASY5 computer simulations of the local and global performance show that the system has fast response and good transient behavior. The ac bus voltage is effectively regulated using the phase-control scheme, which is demonstrated with both line and load variations. The feasibility of paralleling the driver-module outputs is illustrated with the driver modules synchronized and sharing a common feedback loop. An HF sinusoidal ac voltage is generated in the three-phase ac input case, when the driver modules are phased 120 deg away from one another and their outputs are connected in series.

Tsai, Fu-Sheng↗