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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 NTRS1992

Optical luminescence spectroscopy as a probe of the surface mineralogy of Mars

Optical luminescence (OpL) spectroscopy is an attractive use of a visible-near-IR spectrometer on a Mars lander because mineral products of atmosphere-surface interactions on Mars will probably have characteristic OpL spectra. Optical luminescence spectra would be taken at night, when a spectrometer might otherwise sit idle. Also needed would be a source of exciting radiation, which could be shared with other experiments. Optical luminescence is emission of nonthermal optical photons (near-UV through near-IR) as a response to energy input. On absorption of energy, an atom (or ion) will enter an excited state. The favored decay of many such excited states involving valence-band electrons is emission of an optical photon. Optical luminescence spectra can be useful in determining mineralogy and mineral composition. Optical luminescence in crystals can arise from essential elements (or ions), trace-element substituents (activators), or defects. Common activators in salts of alkali and alkaline earth elements include Mn(2+)(VI), other transition metals, the rare earths, and the actinides. Trace substituents of other species can enhance or quench OpL (e.g., Pb(2+) vs. Fe(3+)). Optical luminescence can also arise from defects in crystal structures, including those caused by radiation and shock.

Treiman, A. H.↗
NASA NTRS2001

Measuring Rocket Engine Temperatures with Hydrogen Raman Spectroscopy

Optically accessible, high pressure, hot fire test articles are available at NASA Marshall for use in development of advanced rocket engine propellant injectors. Single laser-pulse ultraviolet (UV) Raman spectroscopy has been used in the past in these devices for analysis of high pressure H2- and CH4-fueled combustion, but relies on an independent pressure measurement in order to provide temperature information. A variation of UV Raman (High Resolution Hydrogen Raman Spectroscopy) is under development and will allow temperature measurement without the need for an independent pressure measurement, useful for flows where local pressure may not be accurately known. The technique involves the use of a spectrometer with good spectral resolution, requiring a small entrance slit for the spectrometer. The H2 Raman spectrum, when created by a narrow linewidth laser source and obtained from a good spectral resolution spectrograph, has a spectral shape related to temperature. By best-fit matching an experimental spectrum to theoretical spectra at various temperatures, a temperature measurement is obtained. The spectral model accounts for collisional narrowing, collisional broadening, Doppler broadening, and collisional line shifting of each Raman line making up the H2 Stokes vibrational Q-branch spectrum. At pressures from atmospheric up to those associated with advanced preburner components (5500 psia), collisional broadening though present does not cause significant overlap of the Raman lines, allowing high resolution H2 Raman to be used for temperature measurements in plumes and in high pressure test articles. Experimental demonstrations of the technique are performed for rich H2-air flames at atmospheric pressure and for high pressure, 300 K H2-He mixtures. Spectrometer imaging quality is identified as being critical for successful implementation of technique.

Wehrmeyer, Joseph A.↗
NASA NTRS2019

Non-Intrusive Characterization of the Wear of the HERMeS Thruster Using Optical Emission Spectroscopy

The Hall Effect Rocket with Magnetic Shielding (HERMeS) is a 12.5 kW Hall thrusterelectric propulsion string that has been in development by NASA Glenn Research Center(GRC) and NASA JPL since 2012. Due to the magnetically shielded design, service life-limiting erosion of the boron nitride discharge has been virtually eliminated. The innerfront pole cover (IFPC) has now been identied as the component dening erosion-basedservice life. Optical emission spectroscopy (OES) is used as an in-situ diagnostic to measurerelative erosion trends during operation of the HERMeS thruster during a series of shortduration wear tests. Erosion trends obtained from the OES data will be compared totraditional erosion data measured with a non-contact prolometer.

hall thruster↗
NASA NTRS2019

Non-Intrusive Characterization of the Wear of the HERMeS Thruster Using Optical Emission Spectroscopy

The Hall Effect Rocket with Magnetic Shielding (HERMeS) is a 12.5 kW Hall thruster electric propulsion string that has been in development by NASA Glenn Research Center(GRC) and NASA JPL since 2012. Due to the magnetically shielded design, service life-limiting erosion of the boron nitride discharge has been virtually eliminated. The inner front pole cover (IFPC) has now been identified as the component defining erosion-based service life. Optical emission spectroscopy (OES) is used as an in-situ diagnostic to measure relative erosion trends during operation of the HERMeS thruster during a series of short duration wear tests. Erosion trends obtained from the OES data will be compared to traditional erosion data measured with a non-contact profilometer.

Gray, Timothy G.↗
NASA NTRS1988

Wavelength-precise slit spectroscopy with optical fiber image scramblers

The application of optical-fiber image scramblers in wavelength-precise slit spectroscopy is discussed together with the design strategy for the optimal instrument configuration incorporating an optical-fiber image scrambler. Particular attention is given to the aspects of data analysis and interpretation techniques which must be specially designed for high-precision spectroscopy. In a specific application to an existing coude spectrograph, the instrumentation and data reduction techniques described in this paper demonstrate an achievable precision corresponding to a systematic radial velocity error of about 30 m/sec.

Heacox, William D.↗
NASA NTRS2010

Confirmation of Soluble Sulfate at the Phoenix Landing Site: Implications for Martian Geochemistry and Habitability

Over the past several decades, elemental sulfur in martian soils and rocks has been detected by a number of missions using X-ray spectroscopy [1-3]. Optical spectroscopy has also provided evidence for widespread sulfates on Mars [4,5]. The ubiquitous presence of sulfur in soils has been interpreted as a widely distributed sulfate mineralogy [6]. However, direct confirmation as to the identity and solubility of the sulfur species in martian soil has never been obtained. One goal of the Wet Chemistry Laboratory (WCL) [7] on board the 2007 Phoenix Mars Lander [8] was to determine soluble sulfate in the martian soil. The WCL received three primary samples. Each sample was added to 25 mL of leaching solution and analysed for solvated ionic species, pH, and conductivity [9,10]. The analysis also showed a discrepancy between charge balance, ionic strength, and conductivity, suggesting unidentified anionic species.

Kounaves, S. P.↗
NASA NTRS1992

Optical fiber spectroscopy: A study of the luminescent properties of the europium ion for thermal sensors

Recently, there has been interest in developing a distributed temperature sensor integrated into an optical fiber. Such a system would allow embedding of the optical fiber within or on a structural material to provide for continuous monitoring of the material's temperature. Work has already begun on the development of a temperature sensor using the temperature dependent emission spectra from the lanthanide rare earths doped into crystalline hosts. The lifetime, the linewidth and the integrated intensity of this emission are each sensitive to changes in the temperature and can provide a basis for thermometry. One concept for incorporating this phenomena into an optical fiber based sensor involves bonding the optically active material to the cladding of an optical fiber and allowing the luminescent light to couple into the the fiber by the evanescent wave. Experimental work developing this concept has already been reported. Measurements of the linewidth of Eu3+:Y2O3, diffused into a fiber, made by Albin clearly show a strong and regular dependence on temperature over the range of 300 to 1000 K. We report here on a study of the temperature dependence of the lineshape of the emission at 611 nm using the data in references. We focus attention on understanding the general behavior of the Eu3+:Y2O3 system. Building upon understanding of this system we will be able to establish the physical criterial for a good optical fiber based temperature sensor and then to examine available data on other lanthanide rare earths and transition metal ions to determine the best luminescent system for temperature sensing in an optical fiber.

Buoncristiani, A. Martin↗
NASA NTRS2016

SU Lyncis, a Hard X-Ray Bright M Giant: Clues Point to a Large Hidden Population of Symbiotic Stars

Symbiotic star surveys have traditionally relied almost exclusively on low resolution optical spectroscopy. However, we can obtain amore reliable estimate of their total Galactic population by using all available signatures of the symbiotic phenomenon. Here we report the discovery of a hard X-ray source, 4PBC J0642.9+5528, in the Swift hard X-ray all-sky survey, and identify it with a poorly studied red giant, SU Lyn, using pointed Swift observations and ground-based optical spectroscopy. The X-ray spectrum, the optical to UV spectrum, and the rapid UV variability of SU Lyn are all consistent with our interpretation that it is a symbiotic star containing an accreting white dwarf. The symbiotic nature of SU Lyn went unnoticed until now, because it does not exhibit emission lines strong enough to be obvious in low resolution spectra. We argue that symbiotic stars without shell-burning have weak emission lines, and that the current lists of symbiotic stars are biased in favour of shell-burning systems. We conclude that the true population of symbiotic stars has been underestimated, potentially by a large factor.

binaries: symbiotic aEuro" stars: individual: SU L↗
NASA NTRS1986

Optical imaging spectroscopy

During the recent solar maximum the combination of imaging and spectroscopy in the visible part of the spectrum became a powerful tool for observational study of flares primarily because of the development of two-dimensional charge-coupled-device (CCD) arrays. In combination with appropriate new operational methods, this has led to the ability to observe, for the first time, the preflare and impulsive-phase physical processes associated with spatially resolved features of flare loops. As a result of concurrent theoretical developments, modeling progressed from an empirical to a physical level. This made it possible to interpret imaging spectra in terms of coronal pressure and heat flux, particle beam heating, chromospheric evaporation, and explosive chromospheric dynamics at the footpoints of flare loops. There is clear potential for further advances in the near future, taking advantage of improvements in digital recording speed (approx. 10-fold), number of photosensitive elements per array (approx. 10-fold), real-time data pre-reduction (potentially 10- to 100-fold), and using multiple CCD arrays. By the time of the next solar maximum imaging spectroscopy is expected to achieve spatial resolution or approx. arc 1 arc s, temporal resolution or approx. 5 s, and simultaneous critically-sampled spectroscopy of several lines and continua. As a result, continued increase in our understanding of the physical processes and configurations of solar flares in the chromosphere, temperature minimum region, and photosphere can be anticipated. Even greater progress toward a more global understanding of flares will obviously come about when simultaneous optical, X-ray, and gamma-ray imaging spectroscopy are possible.

Canfield, R. C.↗
NASA NTRS1986

Auger electron spectroscopy, secondary ion mass spectroscopy and optical characterization of a-C-H and BN films

The amorphous dielectrics a-C:H and BN were deposited on III-V semiconductors. Optical band gaps as high as 3 eV were measured for a-C:H generated by C4H10 plasmas; a comparison was made with bad gaps obtained from films prepared by CH4 glow discharges. The ion beam deposited BN films exhibited amorphous behavior with band gaps on the order of 5 eV. Film compositions were studied by Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The optical properties were characterized by ellipsometry, UV/VIS absorption, and IR reflection and transmission. Etching rates of a-C:H subjected to O2 dicharges were determined.

Pouch, J. J.↗
NASA NTRS1999

Optical Fiber Spectroscopy

This is the final report of work done on NASA Grant NAG-1-443. The work covers the period from July 1, 1992 to December 1, 1998. During this period several distinct but related research studies and work tasks were undertaken. These different subjects are enumerated below with a description of the work done on each of them. The focus of the research was the development of optical fibers for use as distributed temperature and stress sensors. The initial concept was to utilize the utilize the temperature and stress dependence of emission from rare earth and transition metal ions substitutionally doped into crystalline or glass fibers. During the course of investigating this it became clear that fiber Bragg gratings provided a alternative for making the desired measurements and there was a shift of research focus on to include the photo-refractive properties of germano-silicate glasses used for most gratings and to the possibility of developing fiber laser sources for an integrated optical sensor in the research effort. During the course of this work several students from Christopher Newport University and other universities participated in this effort. Their names are listed below. Their participation was an important part of their education.

Buoncristiani, A. M.↗
NASA NTRS1994

The pre-cataclysmic binary EUVE 2013+400

New optical spectroscopy shows a 0.706 d orbital period for Extreme Ultraviolet Explorer (EUVE) 2013+400 and confirms its membership in a class of close binary systems emerging from common-envelope evolution. This binary, like the prototype Feige 24, consists of an extreme ultraviolet (EUV) emitting hot white dwarf and a late-type dwarf. Bergeron et al.'s (1994) optical spectroscopy and ultraviolet spectrophotometry indicate that the white dwarf is hot (T(sub eff) approximately equals 50 000 K) and therefore very young (t(sub age) less than or equal 5 x 10(exp 6) yr), and extreme ultraviolet photometry places EUVE 2013+400 along a neutral hydrogen column density in the interstellar medium of n(sub H) approximately equal to 10(exp 19)/sq cm. The white dwarf is a DAO type and we obtained two independent estimates of the helium abundance from EUV photometric measurements (log(y) approximately equal to -3.2) and from the He II lambda-4686 line profile (log(y) approximately equal to -2.8). The data possibly indicate a level of heterogeneity expected in the context of on-going chemical separation in the photospheric layers. The Balmer lines show narrow emission that varies with binary phase with the equivalent widths of the emission trailing the radial velocities by 1/4 cycle: this phasing shows that most of the emission arises on the EUV-illuminated face of the red dwarf. A spectrophotometric decomposition shows that the secondary's spectral type is near M3 and that it contributes about 15%-25% of the total light near 6500 A; the resulting H-alpha emission is twice as strong as in Feige 24, with an equivalent width of 37-61 A with respect to the red dwarf continuum. EUVE 2013+400 is an important addition to the class of close binary stars discovered in EUV all-sky surveys.

Thorstensen, John R.↗
NASA NTRS1985

Rapid evaluation of ion thruster lifetime using optical emission spectroscopy

A major life-limiting phenomenon of electric thrusters is the sputter erosion of discharge chamber components. Thrusters for space propulsion are required to operate for extended periods of time, usually in excess of 10,000 hr. Lengthy and very costly life-tests in high-vacuum facilities have been required in the past to determine the erosion rates of thruster components. Alternative methods for determining erosion rates which can be performed in relatively short periods of time at considerably lower costs are studied. An attempt to relate optical emission intensity from an ion bombarded surface (screen grid) to the sputtering rate of that surface is made. The model used a kinetic steady-state (KSS) approach, balancing the rates of population and depopulation of ten low-lying excited states of the sputtered molybdenum atom (MoI) with those of the ground state to relate the spectral intensities of the various transitions of the MoI to the population densities. Once this is accomplished, the population density can be related to the sputtering rate of the target. Radiative and collisional modes of excitation and decay are considered. Since actual data has not been published for MoI excitation rate and decay constants, semiempirical equations are used. The calculated sputtering rate and intensity is compared to the measured intensity and sputtering rates of the 8 and 30 cm ion thrusters.

Rock, B. A.↗
NASA NTRS1985

Rapid evaluation of ion thruster lifetime using optical emission spectroscopy

A major life-limiting phenomenon of electric thrusters is the sputter erosion of discharge chamber components. Thrusters for space propulsion are required to operate for extended periods of time, usually in excess of 10,000 hr. Lengthy and very costly life-tests in high-vacuum facilities have been required in the past to determine the erosion rates of thruster components. Alternative methods for determining erosion rates which can be performed in relatively short periods of time at considerably lower costs are studied. An attempt to relate optical emission intensity from an ion bombarded surface (screen grid) to the sputtering rate of that surface is made. The model used a kinetic steady-state (KSS) approach, balancing the rates of population and depopulation of ten low-lying excited states of the sputtered molybdenum atom (MoI) with those of the ground state to relate the spectral intensities of the various transitions of the MoI to the population densities. Once this is accomplished, the population density can be related to the sputting rate of the target. Radiative and collisional modes of excitation and decay are considered. Since actual data has not been published for MoI excitation rate and decay constants, semiempirical equations are used. The calculated sputtering rate and intensity is compared to the measured intensity and sputtering rates of the 8 and 30 cm ion thrusters.

Rock, B. A.↗
NASA NTRS2018

Optical Coronagraphic Spectroscopy of AU Mic: Evidence of Time Variable Colors?

We present coronagraphic long slit spectra of AU Mic's debris disk taken with the STIS instrument aboard the Hubble Space Telescope. Our spectra are the first spatially-resolved, scattered light spectra of the system's disk, which we detect at projected distances between approximately 10 and 45 au. Our spectra cover a wavelength range between 5200 and 10200 Angstrom. We find that the color of AU Mic's debris disk is bluest at small (12-17 au) projected separations. These results both confirm and quantify the findings qualitatively noted by Krist et al. and are different than IR observations that suggested a uniform blue or gray color as a function of projected separation in this region of the disk. Unlike previous literature, which reported that the color of AU Mic's disk became increasingly more blue as a function of projected separation beyond approx. 30 au, we find the disk's optical color between 35 and 45 au to be uniformly blue on the southeast side of the disk and decreasingly blue on the northwest side. We note that this apparent change in disk color at larger projected separations coincides with several fast, outward moving ''features'' that are passing through this region of the southeast side of the disk. We speculate that these phenomenon might be related and that the fast moving features could be changing the localized distribution of sub-micron-sized grains as they pass by, thereby reducing the blue color of the disk in the process. We encourage follow-up optical spectroscopic observations of AU Mic to both confirm this result and search for further modifications of the disk color caused by additional fast moving features propagating through the disk.

Lomax, Jamie R.↗
NASA NTRS2005

Optical and X-ray studies of chromospherically active stars: FR Cancri, HD 95559 and LO Pegasi

We present a multiwavelength study of three chromospherically active stars, namely FR Cnc (= BD +16 degrees 1753), HD 95559 and LO Peg (=BD +22 degrees 4409), including newly obtained optical photometry, (for FR Cnc) low-resolution optical spectroscopy, as well as archival IR and X-ray observations. The BVR photometry carried out during the years 2001 - 2004 has found significant photometric variability to be present in all three stars. For FR Cnc, a photometric period 0.826685 +/- 0.000034 d has been established. The strong variation in the phase and amplitude of the FR Cnc light curves when folded on this period implies the presence of evolving and migrating spots or spot groups on its surface. Two independent spots with migration periods of 0.97 and 0.93 years respectively are inferred. The photometry of HD 95559 suggests the formation of a spot (group) during the interval of our observations. We infer the existence of two independent spots or groups in the photosphere of LO Peg, one of which has a migration period of 1.12 years. The optical spectroscopy of FR Cnc carried out during 2002-2003, reveals the presence of strong and variable Ca I1 H and K, H(sub beta) and H(sub alpha) emission features indicative of high level of chromospheric activity. The value of 5.3 for the ratio of the excess emission in H(sub alpha) to H(sub beta), EH(sub alpha)/EH(sub beta), suggests that the chromospheric emission may arise from an extended off-limb region. We have searched for the presence of color excesses in the near-IR JHK bands of these stars using 2MASS data, but none of them appear to have any significant color excess. We have also analyzed archival X-ray observations of HD 95559 and LO Peg carried out by with the ROSAT observatory. The best fit models to their X-ray spectra imply the presence of two coronal plasma components of differing temperatures and with sub-solar metal abundances. The inferred emission measures and temperatures of these systems are similar to those found for other active dwarf stars. The kinematics of FR Cnc suggest that it is a very young (35 - 55 Myrs) main-sequence star and a possible member of the IC 2391 supercluster. LO Peg also has young disk-type kinematics and has been previously suggested to be a member of the 100 Mys old Local Association (Pleiades Moving Group). The kinematics of HD 95559 indicate it is a possible member of the 600 Myrs old Hyades supercluster.

Pandey, J. C.↗