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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Acquisition of a Gas Chromatograph/Mass Spectrometer System for Laboratory Study of Prebiotic Organic Geochemical Processes on the Early Earth, Mars, and Meteorites

This was a major equipment grant that provided funds ($72K) for purchase of a benchtop gas chromatograph-mass spectrometer (GC-MS) for use in experimental studies of prebiotic organic compounds. An Agilent model 689015973 GC-MS was purchased and installed in the PI's lab in August of 2003. The instrument is now being used for a variety of research projects. The primary use of the instrument is to analyze and quantify organic products of laboratory experiments conducted by the PI. One example is shown, which shows organic products (predominantly n-alkanes) formed during Fischer-Tropsch-type abiotic synthesis under hydrothermal conditions. The analytical capabilities of the GC- MS allowed identification of the numerous organic products of this as well as other laboratory experiments. A key use of the instrument in this research is that the mass spectrometer capabilities allow use of isotopically labeled reactants to trace the progress of reactions and evaluate background contaminants. collaborative projects with other scientists involved in exobiology & astrobiology research (e.g., Mitch Schulte, NASA Ames; Katrina Edwards, Woods Hole Oceanographic Institution). For instance, an analysis of membrane lipids of an lithoautotrophic iron-oxidizing bacteria being grown on basalt as a source of metabolic energy, a project where the instrument is being used to evaluate possible biomarker compounds from these organisms is shown. These iron oxidizers are thought to be similar to those living within the ocean crust, and are being investigated as possible analog organisms to those on the early Earth or crust of Mars. The instrument has also been used by an outside investigator (graduate student Brandon Canfeld, Arizona State University) for identification and isotopic characterization of experimental products of abiotic organic synthesis experiments he is conducting with Dr. John Holloway. analysis of quality control samples for other NASA-funded projects. For instance, an analysis of residual hydrocarbon contaminants on the internal surface of the shell of an atmospheric sounding rocket is shown. This analysis was used to help determine the source of the contaminating compounds. In the future, the instrument will continue to be used for quality control analysis in clean rooms and instrument construction facilities within the Laboratory for Atmospheric and Space Physics, where the GC-MS is housed.

McCollom, Thomas↗
NASA NTRS1980

Mira variables: An informal review

The structure of the Mira variables is discussed with particular emphasis on the extent of their observable atmospheres, the various methods for measuring the sizes of these atmospheres, and the manner in which the size changes through the cycle. The results obtained by direct, photometric and spectroscopic methods are compared, and the problems of interpretation are addressed. Also, a simple model for the atmospheric structure and motions of Miras based on recent observations of the doubling of infrared molecualr times is described. This model, consisting of two atmospheric layers plus a circumstellar shell, provides a physically plausible picture of the atmosphere which is consistent with the photometrically measured magnitude and temperature variations as well as the spectroscopic data.

Wing, R. F.↗
NASA NTRS2011

Do Titan's Mountains Betray the Late Acquisition of its Current Atmosphere

Titan may have acquired its massive atmosphere relatively recently in solar system history [1,2,3,4]. Prior to that time, Titan would have been nearly airless, with its volatiles frozen or sequestered. Present-day Titan experiences only small (approximately 4 K) pole-to-equator variations, owing to efficient heat transport via the thick atmosphere [5]; these temperature variations would have been much larger (approximately 20 K) in the absence of an atmosphere. If Titan's ice shell is conductive, the change in surface temperature associated with the development of an atmosphere would have led to changes in shell thickness. In particular, the poles would move down (inducing compression) while the equator would move up. Figure 1 shows the predicted change in surface elevation as a result of the change in surface temperature, using the numerical conductive shell thickness model of [6]

Moore, Jeffrey Morgan↗
NASA NTRS1981

Continuous replenishment of molten semiconductor in a Czochralski-process, single-crystal-growing furnace

A replenishment crucible is mounted adjacent the usual drawing crucible, from which a monocrystalline boule is drawn according to the Czochralski method. A siphon tube for molten semiconductor transfer extends from the replenishment crucible to the drawing crucible. Each crucible is enclosed within its own hermetic shell and is provided with its own heater. The siphon tube is initially filled with molten semiconductor by raising the inert atmospheric pressure in the shell surrounding the replenishment crucible above that surrounding the drawing crucible. Thereafter, adjustment of the level of molten semiconductor in the drawing crucible may be achieved by adjusting the level in either crucible, since the siphon tube will establish the same level in both crucibles. For continuous processing, solid semiconductor may be added to and melted in the replenishment crucible during the process of drawing crystals from the drawing crucible. A constant liquid level of melted semiconductor is maintained in the system by an optical monitoring device and any of several electromechanical controls of the rate of replenishment or crucible height.

Fiegl, George↗
NASA NTRS1994

A deep atmospheric eclipse of AL Velorum

I have obtained new International Ultraviolet Explorer (IUE) observations in 1992 to search for an accretion column in and to analyze an atmospheric eclipse of AL Vel, a low luminosity zeta Aurigae binary. Rich shell spectra recorded at three phases of atmospheric eclipse give column densities and excitation temperatures for the chromospheric gas. The chromospheric density falls off exponentially with a scale height of 3 solar radius, an order of magnitude greater than expected for support by thermal motions. Excitation temperatures at 2 - 5 scale heights into the chromosphere are approximately 7000 K, with Doppler widths near 17 km/s. Absorption features that could be formed in an accretion column were detected at phases 0.70 and 0.75 in a series of spectra spanning the range 0.63-0.80 in orbital phase. They imply a very slow acceleration of the wind, consistent with results for other zeta Aur binaries, but the wind speed implied is inconsistent with profiles of wind lines. The terminal velocity of this wind, greater than or approximately = 360 km/s, is higher than that in any of the other zeta Aur binaries. Wind and chromospheric features in 1992 were much more prominent than in 1988, which implies that both the wind and chromosphere were much more massive: we seem to have witnessed in 1992 a burst of activity with a mass-loss rate greater than 10(exp -8) solar mass/yr.

Eaton, Joel A.↗
NASA NTRS2003

A Systematic Global Mapping of the Radiation Field at Aviation Altitudes

This paper presents early results from aircraft measurements made by a Low-LET Radiation Spectrometer (LoLRS), as part of a long-range effort to study the complex dynamics of the atmospheric radiation field. For this purpose, a comprehensive data base is being generated to enable a multivariable global mapping (and eventually modeling) of doses and Linear-Energy-Transfer (LET) spectra at aviation altitudes. To accomplish this, a methodical collection of data from the LoLRS (and other instruments), is planned over extended periods of time, in a manner that complements some previous isolated and sporadic measurements by other workers, with the objective to generate a detailed long-range description of the cosmic-ray induced particle environment and to study its variability and dependence on atmospheric thickness, magnetic latitude, L-shell or rigidity, space weather, solar particle events, solar cycle effects, magnetic field variation, diurnal and seasonal effects, and atmospheric weather. Analysis of initial data indicates that the dose is rising with increasing altitude and increasing magnetic latitude. Comparison of total doses with predictions is in good agreement.

Stassinopoulos, E. G.↗
NASA NTRSDate not supplied

Understanding Atmospheric Absorption Effects on UV Spectra from Sounding Rockets using a Spherical-Shells Model

Our team is working on building and calibrating the FURST sounding rocket, with an expected launch in mid-2023. The goal is to image the most complete and highest resolution UV spectra to date. To do this, preciseradiometric and wavelength calibration techniques have been developed. We describe below our model of O2 atmospheric absorption and couple that with simulated FURST images. With a high-enough SNR, we canestimate our ability to use absorption peaks for calibration, or for back-calculating atmospheric properties. If data is available, this method could be applied to older sounding rocket data to find hidden science.

MSFC, NASA, UAH, CSPAR, FURST, MSU, SHINE, Aeronom↗
NASA NTRSDate not supplied

Understanding Atmospheric Absorption Effects on UV Spectra from Sounding Rockets using a Spherical-Shells Model

Our team is working on building and calibrating the FURST sounding rocket, with an expected launch in mid-2023. The goal is to image the most complete and highest resolution UV spectra to date. To do this, precise radiometric and wavelength calibration techniques have been developed. We describe below our model of O2 atmospheric absorption and couple that with simulated FURST images. With a high-enough SNR, we can estimate our ability to use absorption peaks for calibration, or for back-calculating atmospheric properties. If data is available, this method could be applied to older sounding rocket data to find hidden science.

MSFC, NASA, UAH, CSPAR, FURST, MSU, SHINE, Aeronom↗
NASA NTRS1982

Spectral energy distribution /119 - 685 nm/ in 16 shell stars and a tentative model for accreting Be stars

IUE low-dispersion spectra and spectral scans made with the Lick Observatory IDS scanners have been combined for 16 shell stars. Eleven objects can be represented by Kurucz (1979) model atmospheres, although some of them display strong shell-type line spectra. Five among them are known binaries. The six remaining objects display complex spectra. A model involving continuum and line radiation from a hydrogen cloud surrounding the accreting component is proposed. A generalization of this model with optically thick segments of the cloud promises to explain even more exotic objects such as beta Lyrae, W Serpentis and possibly epsilon Aurigae.

Plavec, M. J.↗
NASA NTRS1994

The 1992/93 eclipse of 31 Cygni

Extensive new ultraviolet and optical spectra of an atmospheric eclipse define the physical properties throughout the wind and chromosphere of 31 Cyg. These data require mass loss of approximately 3 x 10(exp -8) solar masses/yr in a wind that may merge smoothly into the chromosphere. Considerations of how energy is injected into the wind, however, suggest that the chromosphere and wind are separate structures. Most, if not all, of the velocity structure in metallic lines, which we have heretofore simulated with Doppler widths in the range 15-25 km/s, results from differential expansion of the atmosphere. Electron densities in the inner R(sub star) of the chromosphere are in the range 1.5 x 10(exp 9) - 2 x 10(exp 8)/cu cm, which implies clumping of the gas. The ionization of oxygen and nitrogen is consistent with clumping by factors of 3-30 in the outer chromosphere, roughly the amount required to give enough gas pressure to support the chromosphere. Chromospheric gas in 31 Cyg becomes hotter with increasing height, thus with decreasing optical depth, in a way that seems similar for all the zeta Aur binaries. Excitation temperature for Fe II in 1992/93 rises from about 5000 K at the deepest points sampled to about 12,500 K high in the wind. Strengths of violet Balmer lines give an excitation temperature for hydrogen of 6200-6500 K above a radial mass column density of approximately 0.01 g/sq cm. This amount of excitation implies that Lyman-alpha is thermalized beneath about 4 x 10(exp -3) g/sq cm. The outer atmosphere was symmetrical to within a factor of 2 in 1992/93, although it was clearly variable at this level, and it had similar mass column densities as in 1982. One manifestation of the variability was a flow toward the B star at phases 0.013-0.022 spanning velocities 45-100 km/s. Several lines of evidence point to a complicated and variable ionization in the wind: At large distance from the K star, measured mass column densities are less by up to a factor of 3 than required by a smoothly flowing wind. Also, much of the gas beyond r = 350 solar radii = 1.75 R(sub star) has a negative radial velocity. Radial velocities of the shell lines imply the outer atmosphere rotates in the direction of orbital motion, possibly through the deflection of wind flow lines in this direction.

Eaton, Joel A.↗
NASA NTRS1985

Conjecture on superrotation in planetary atmospheres - A diffusion model with mixing length theory

The component of rigid shell superrotation on Venus is discussed in the context of comparative planetary atmospheres. A simplified, heuristic analysis, utilizing mixed length theory to describe the small scale nonlinear advections of energy and angular momentum, thereby providing a closure of the dynamic system, is presented, on the basis of which a crude estimate of zonal velocity is made. The rigid shell (global average) component on Venus was calculated to be 105 m/sec.

Mayr, H. G.↗
NASA NTRS1992

The cometary contribution to prebiotic chemistry

The chemical composition of cometary nuclei is examined to estimate the potential contribution of volatiles to the prebiotic earth from cometary collisions. Observations of cometary nuclei are reviewed to describe the chemical evolution of the objects and their theoretical potential for affecting the terrestrial environment. Specific attention is given to the plausibility of the single-impact formation of the earth-moon system, and experiments are proposed for testing the present theories. It is proposed that significant contributions of biogenic elements such as C, H, N, O, P, and S resulted from these nuclei colliding with the earth. Observations of the solar atmosphere and of the circumstellar shells of C-rich stars indicate that compounds such as CO, C2, and H2O were not pyrolyzed as a result of collision events. The compounds are theorized to have established the foundation for the abiotic synthesis of key biochemical molecules.

Oro, J.↗
NASA NTRS2009

NESC Review of the 8-Foot High Temperature Tunnel (HTT) Oxygen Storage Pressure Vessel Inspection Requirements

The 8-Foot HTT (refer to Figure 4.0-1) is used to conduct tests of air-breathing hypersonic propulsion systems at Mach numbers 4, 5, and 7. Methane, Air, and LOX are mixed and burned in a combustor to produce test gas stream containing 21 percent by volume oxygen. The NESC was requested by the NASA LaRC Executive Safety Council to review the rationale for a proposed change to the recertification requirements, specifically the internal inspection requirements, of the 8-Foot HTT LOX Run Tank and LOX Storage Tank. The Run Tank is an 8,000 gallon cryogenic tank used to provide LOX to the tunnel during operations, and is pressured during the tunnel run to 2,250 pounds per square inch gage (psig). The Storage Tank is a 25,000 gallon cryogenic tank used to store LOX at slightly above atmospheric pressure as a external shell, with space between the shells maintained under vacuum conditions.

Gilbert, Michael↗
NASA NTRS1976

Exospheric density measurements from the drag-free satellite Triad

The Triad satellite is maintained within 1 mm of its proof mass (a small metal ball) in a purely gravitational orbit, using a drag-free control system, named Discos, as the disturbance compensation system. The Discos proof mass is surrounded by an outer shell which holds fuel tanks and cold gas jets. The shell shields the proof mass from such nongravitational forces as radiation pressure, atmospheric drag, and micrometeorite impact. Whenever these forces displace the outer shell relative to the proof mass, an error signal is generated by a capacitive bridge sensor, and the satellite is propelled by gas jets to remain centered on the proof mass when the error reaches 1 mm. Local atmospheric densities near 800 km were measured, using ball position data, and the observed accelerations were corrected for the effects of solar radiation pressure. The measured densities reveal a greater dependence on latitude than that indicated by balloon satellites, and also a dependence on longitude. Only a small dependence on Kp, however, was observed in the region where the measurements were made.

Moe, K.↗
NASA NTRS1985

A mixed pseudospectral/finite difference method for a thermally driven fluid in a nonuniform gravitational field

A numerical study of the steady, axisymmetric flow in a heated, rotating spherical shell is conducted to model the Atmospheric General Circulation Experiment (AGCE) proposed to run aboard a later shuttle mission. The AGCE will consist of concentric rotating spheres confining a dielectric fluid. By imposing a dielectric field across the fluid a radial body force will be created. The numerical solution technique is based on the incompressible Navier-Stokes equations. In the method a pseudospectral technique is based on the incompressible Navier-Stokes equations. In the method a pseudospectral technique is used in the latitudinal direction, and a second-order accurate finite difference scheme discretizes time and radial derivatives. This paper discusses the development and performance of this numerical scheme for the AGCE which has been modelled in the past only by pure FD formulations. In addition, previous models have not investigated the effect of using a dielectric force to simulate terrestrial gravity. The effect of this dielectric force on the flow field is investigated as well as a parameter study of varying rotation rates and boundary temperatures. Among the effects noted are the production of larger velocities and enhanced reversals of radial temperature gradients for a body force generated by the electric field.

Macaraeg, M. G.↗
NASA NTRS1985

A mixed pseudospectral/finite difference method for a thermally driven fluid in a nonuniform gravitational field

A numerical study of the steady, axisymmetric flow in a heated, rotating spherical shell is conducted to model the Atmospheric General Circulation Experiment (AGCE) proposed to run aboard a later Shuttle mission. The AGCE will consist of concentric rotating spheres confining a dielectric fluid. By imposing a dielectric field across the fluid a radial body force will be created. The numerical solution technique is based on the incompressible Navier-Stokes equations. In the method a pseudospectral technique is used in the latitudinal direction, and a second-order accurate finite difference scheme discretizes time and radial derivatives. This paper discusses the development and performance of this numerical scheme for the AGCE which has been modeled in the past only by pure FD formulations. In addition, previous models have not investigated the effect of using a dielectric force to simulate terrestrial gravity. The effect of this dielectric force on the flow field is investigated as well as a parameter study of varying rotation rates and boundary temperatures. Among the effects noted are the production of larger velocities and enhanced reversals of radial temperature gradients for a body force generated by the electric field.

Macaraeg, M. G.↗
NASA NTRS2002

Outbursts In Symbiotic Binaries (FUSE 2000)

During the past year, we made good progress on analysis of FUSE observations of the symbiotic binary Z And. For background, Z And is a binary system composed of a red giant and a hot component of unknown status. The orbital period is roughly 750 days. The hot component undergoes large-scale eruptions every 10-20 yr. An outburst began several years ago, triggering this FUSE opportunity. First, we obtained an excellent set of ground-based optical data in support, of the FUSE observations. We used FAST, a high throughput low resolution spectrograph on the 1.5-m telescope at Mt. Hopkins, Arizona. A 300 g/ mm grating blazed at 4750 A, a 3 in. slit, and a thinned Loral 512 x 2688 CCD gave us spectra covering 3800-7500 A at a resolution of 6 A. The wavelength solution for each spectrum has a probable error of +/- 0.5 A or better. Most of the resulting spectra have moderate signal-to-noise, S/.N approx. greater than 30 per pixel. The time coverage for these spectra is excellent. Typically, we acquired spectra every 1-2 nights during dark runs at Mt. Hopkins. These data cover most of the rise and all of the decline of the recent outburst. The spectra show a wealth of emission lines, including H I, He I, He II, [Fe V11], and the Raman scattering bands at 6830 A and 7088 A. The Raman bands and other high ionization features vary considerably throughout the outburst. These features will enable us to correlate variations in the FUSE spectra with variations in the optical spectra. Second, we began an analysis of FUSE spectra of Z And. We have carefully examined the spectra, identifying real features and defects. We have identified and measured fluxes for all strong emission lines, including the O VI doublet at 1032 A and 1038 A. These and several other strong emission lines display pronounced P Cygni absorption components indicative of outgrowing gas. We will attempt to correlate these velocities with similar profiles observed on optical spectra. The line velocities - together with line variations - will yield physical parameters for the expanding shell of gas in the outer atmosphere of the hot component. We also worked on several diagnostic tools, including upgrades to photoionization programs developed by the PI and others. We plan to use these tools to derive electron densities and temperatures front intercombination and forbidden lines observed on optical and FUSE spectra. Preliminary results indicate a large electron density, n(sub e) is greater than or = 10(exp 10)/cc and a modest electron temperature, T(sub e) approx. 20,000 K. We see no evidence for shocked gas as observed in some other symbiotics. However, we have yet to include several important lines of [Fe VII] and [Ne V] in the analysis. Inclusion of these lines will yield an improved estimate of the electron temperature in the gas. Finally, we have one additional FUSE spectrum planned for acquisition during this cycle. These data will provide important information concerning the state of the system farther along in its decline. Once we have this spectrum in hand, we plan to complete our analysis and publish our results.

Kenyon, Scott J.↗
NASA NTRS2017

Mathematical Modeling of Electrodynamics Near the Surface of Earth and Planetary Water Worlds

An interesting feature of planetary bodies with hydrospheres is the presence of an electrically conducting shell near the global surface. This conducting shell may typically lie between relatively insulating rock, ice, or atmosphere, creating a strong constraint on the flow of large-scale electric currents. All or parts of the shell may be in fluid motion relative to main components of the rotating planetary magnetic field (as well as the magnetic fields due to external bodies), creating motionally-induced electric currents that would not otherwise be present. As such, one may expect distinguishing features in the types of electrodynamic processes that occur, as well as an opportunity for imposing specialized mathematical methods that efficiently address this class of application. The purpose of this paper is to present and discuss such specialized methods. Specifically, thin-shell approximations for both the electrodynamics and fluid dynamics are combined to derive simplified mathematical formulations describing the behavior of these electric currents as well as their associated electric and magnetic fields. These simplified formulae allow analytical solutions featuring distinct aspects of the thin-shell electrodynamics in idealized cases. A highly efficient numerical method is also presented that is useful for calculations under inhomogeneous parameter distributions. Finally, the advantages as well as limitations in using this mathematical approach are evaluated. This evaluation is presented primarily for the generic case of bodies with water worlds or other thin spherical conducting shells. More specific discussion is given for the case of Earth, but also Europa and other satellites with suspected oceans.

Tyler, Robert H.↗