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At least 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Storage and retrieval of mass spectral information

Computer handling of mass spectra serves two main purposes: the interpretation of the occasional, problematic mass spectrum, and the identification of the large number of spectra generated in the gas-chromatographic-mass spectrometric (GC-MS) analysis of complex natural and synthetic mixtures. Methods available fall into the three categories of library search, artificial intelligence, and learning machine. Optional procedures for coding, abbreviating and filtering a library of spectra minimize time and storage requirements. Newer techniques make increasing use of probability and information theory in accessing files of mass spectral information.

Hohn, M. E.↗
NASA NTRS1979

Critical mass flux through short Borda type inlets of various cross sections

Mass flux measurements associated with chocked flows through four Borda type inlet geometries: circular, square, triangular and rectangular (two-dimensional) and two sharp edged geometries taken over a very wide range of inlet stagnation conditions. The measurements indicate that: (1) the mass flux is independent of the inlet cross-section geometry and (2) the mass flux is dependent only on the inlet stagnation conditions. Also by using choked flow results found in the literature, the reduced mass flux is independent of working fluid. Two implications are drawn which remain to be verified: (1) since seal leak rates are weakly dependent on geometry but pressure distribution is strongly dependent on geometry, seal design efforts should be directed more toward controlling the dynamics, and (2) high-L/D ducts of arbitrary cross section and Borda type inlets can possess free jets.

Hendricks, R. C.↗
NASA NTRS1978

Metastable states and mass loss in Be stars

Three strong asymmetric absorption features with short-wavelength wings extending 350 km/s from their respective line centers at 2061.6, 2068.2, and 2079.0 A appear in high-resolution UV spectral data (0.1 A) for the Be star Phi Per (B2 Ve4) obtained with the Balloon-borne Ultraviolet Stellar Spectrometer (BUSS) on the evening of September 16, 1976. These transitions are not resonance lines and have been identified as transitions of Fe III (UV 48) originating from a metastable state with an excitation of 5.01 eV. The relative populations of the metastable and ground states are independent of the dilution factor, allowing calculation of the mass-outflow rate for a generalized model. Thus, a mass-outflow rate of 5 hundred-billionths of a solar mass per year is obtained. These transitions are observable with IUE and represent an important tool for studying mass outflow in Be and shell stars.

Bruhweiler, F. C.↗
NASA NTRS1978

Systems efficiency and specific mass estimates for direct and indirect solar-pumped closed-cycle high-energy lasers in space

Based on expected advances in technology, the maximum system efficiency and minimum specific mass have been calculated for closed-cycle CO and CO2 electric-discharge lasers (EDL's) and a direct solar-pumped laser in space. The efficiency calculations take into account losses from excitation gas heating, ducting frictional and turning losses, and the compressor efficiency. The mass calculations include the power source, radiator, compressor, fluids, ducting, laser channel, optics, and heat exchanger for all of the systems; and in addition the power conditioner for the EDL's and a focusing mirror for the solar-pumped laser. The results show the major component masses in each system, show which is the lightest system, and provide the necessary criteria for solar-pumped lasers to be lighter than the EDL's. Finally, the masses are compared with results from other studies for a closed-cycle CO2 gasdynamic laser (GDL) and the proposed microwave satellite solar power station (SSPS).

Monson, D. J.↗
NASA NTRS1979

Mass flow in loop type coronal transients

Coronal transients having characteristics of a well-defined loop structure are examined, particularly with respect to temporal changes in the density and mass per unit length along the loop over periods of several days after the initial eruption. Measurements of mass distributions as a function of time are presented for eight transients, and one particular transient with a fairly simple configuration is investigated in more detail. Theoretical calculations are combined with the masses and densities derived from the observations to obtain estimates of the material flow in the transients; this flow is modeled on the assumption that magnetic forces drive and confine the loop. The flow field is found to be diverging everywhere, indicating that the density decreases in time. It is inferred that the transient legs are approximately in hydrostatic equilibrium and that most of the mass of the transient is lost from the sun during the initial phase.

Anzer, U.↗
NASA NTRS1979

The association of coronal mass ejection transients with other forms of solar activity

Coronal mass-ejection transients observed with the white-light coronagraph on Skylab are found to be associated with several other forms of solar activity. There is a strong correlation between such mass-ejection transients and chromospheric H-alpha activity, with three-quarters of the transients apparently originating in or near active regions. It is inferred that 40% of transients are associated with flares, 50% are associated with eruptive prominences solely (without flares), and more than 70% are associated with eruptive prominences or filament disappearances (with or without flares). Nine of ten flares that displayed apparent mass ejections of H-alpha-emitting material from the flare site could be associated with coronal transients. Within each class of activity, the more energetic events are more likely to be associated with an observable mass ejection.

Munro, R. H.↗
NASA NTRS1978

Ultra-low-mass flexible planar solar arrays using 50-micron-thick solar cells

A conceptual design study has been completed which has shown the feasibility of ultra-low-mass planar solar arrays with specific power of 200 watts/kilogram. The beginning of life (BOL) power output of the array designs would be 10 kW at 1 astronomical unit (AU) and a 55C deg operating temperature. Two designs were studied: a retractable rollout design and a non-retractable fold-out. The designs employed a flexible low-mass blanket and low-mass structures. The blanket utilized 2 x 2 cm high-efficiency (13.5% at 28C deg AM0), ultra-thin (50 micron), silicon solar cells protected by thin (75 micron) plastic encapsulants. The structural design utilized the 'V'-stiffened approach which allows a lower mass boom to be used. In conjunction with the conceptual design, modules using the thin cells and plastic encapsulant were designed and fabricated.

Costogue, E. N.↗
NASA NTRS1980

A discussion of Cepheid masses

Masses and compositions of Cepheids are essential to map the places in the Hertzsprung-Russell diagram where various radial pulsation modes occur. Luminosity observations and stellar evolution theory give masses for Cepheids which range from 10 percent to a factor of four more than those given by pulsation theory. Combining the evolution and pulsation theories, a theoretical mass was determined using only the period and an approximate surface effective temperature. The ratio of the theoretical to evolutionary masses averaged 0.99 + or - 0.07 for 16 Cepheids.

Cox, A. N.↗
NASA NTRS1980

Pulsation and mass loss in Mira variables

The behavior of pulsation in the outer layers of a typical Mira variable was studied in the adiabatic and isothermal limits. A shock wave propagates outward once per period and the radial velocity obtained from observations of hydrogen emission lines is identified with the velocity of gas in the post shock region. In the adiabatic case, mass loss in the form of a steady stellar wind was produced. In the isothermal case, no continuous mass loss was produced but occasional ejection of shells occur. Pulsation introduced into a star undergoing steady mass loss as a result of radiation pressure acting on grains caused the mass loss rate to increase by a factor of approximately 40, while the terminal velocity of the flow was almost unaltered.

Wood, P. R.↗
NASA NTRS1979

Study and evaluation of impulse mass spectrometers for ion analysis in the D and E regions of the ionosphere

Theoretical and numerical analyses were made of planar, cylindrical and spherical electrode time-of-flight mass spectrometers in order to optimize their operating conditions. A numerical analysis of potential barrier gating in time-of-flight spectrometers was also made. The results were used in the design of several small mass spectrometers. These were constructed and tested in a laboratory space simulator. Detailed experimental studies of a miniature cylindrical electrode time of flight mass spectrometer and of a miniature hemispherical electrode time of flight mass spectrometer were made. The extremely high sensitivity of these instruments and their ability to operate at D region pressures with an open source make them ideal instruments for D region ion composition measurements.

Kendall, B. R.↗
NASA NTRS1980

Mass loss from warm giants: Magnetic effects

Among warm giant stars, rapid mass loss sets in along a well defined velocity dividing line (VDL). Hot corona also disappear close to the VDL and thermal pressure cannot drive the observed rapid mass loss in these stars. The VDL may be associated with magnetic fields changing from closed to open. Such a change is consistent with the lack of X-rays from late-type giants. A magnetic transition locus based on Pneuman's work on helmet streamer stability agrees well with the empirical VDL. The change from closed to open fields not only makes rapid mass loss possible, but also contributes to energizing the mass loss in the form of discrete bubbles.

Mullan, D. J.↗
NASA NTRS1979

Construction and testing of the 2.5m mass driver

Presented are the designs used in the construction of the 2.5 m mass driver and the results of the initial testing program. The mass driver consists of equal length sections of acceleration and deceleration each containing 59 drive coils of 13.1 cm caliber. Intermediate energy storage is provided by sector capacitors which are recharged every half cycle by an external power source. The drive coils are individually energized through SCR's with timing supplied by position sensing optical detectors. The drive consists of two phases which operate in quadrature. The initial bucket to be propelled through the mass driver contains two coils of aluminum wire chilled to liquid nitrogen temperatures to momentarily sustain superconducting field intensities. Magnetic flight is generated by eddy current repulsion from six copper guide strips lining the mass driver. Nominal acceleration is 5000 m/sec per sec giving a maximum bucket velocity of 112 m/s.

Snow, W. R.↗
NASA NTRS1979

N-body experiments and missing mass in clusters of galaxies

It is commonly assumed that the distributions of surface density and radial-velocity dispersion in clusters of galaxies are sensitive tracers of the underlying distribution of any unseen mass. N-body experiments have been used to test this assumption. Calculations with equal-mass systems indicate that the effects of the underlying mass distribution cannot be detected by observations of the surface-density or radial-velocity distributions, and the existence of an extended binding mass in all well-studied clusters would be consistent with available observations.

Smith, H.↗
NASA NTRS1979

Masses and densities of asteroids

Ceres, Pallas, and Vesta allow a determination of mass from gravitational effects in the motion of another asteroid. An extended and partly corrected set of observations of 197 Arete leads to an increase of 15% in the resulting mass of Vesta that was first determined by Hertz. Other possibilities of mass determination and estimates of the total mass of asteroids are mentioned. The available diameter determinations and adopt preferred values are reviewed. The densities for Ceres, Pallas, and Vesta are respectively 2.3 plus or minus 1.1 g/cu cm, 2.6 plus or minus 0.9 g/cu cm and 3.3 plus or minus 1.5 g/cu cm.

Schubart, J.↗
NASA NTRS1979

Minimum-mass designs of stiffened graphite/polyimide compression panels

This study presents results from an analytic investigation to determine minimum-mass designs of stiffened Gr/Pi compression panels for a wide range of uniaxial compression loads. Four panel configurations are considered: (1) hat stiffened-laminated skin, (2) hat stiffened-honeycomb core sandwich skin, (3) blade stiffened-laminated skin and (4) blade stiffened-honeycomb core sandwich skin panels. Designs are generated by an automatic optimization computer code entitled PASCO (Panel Analysis and Sizing COde). The analysis portion of PASCO contains a generalized buckling analysis which calculates all critical modes without assuming any of them a priori. Mass-strength curves are presented for the four configurations along with specific designs generated for low, moderate and high values of compression load. A mass-strength curve for a titanium hat stiffened panel is provided for comparison. A 30% to 50% mass savings over titanium panels is shown for moderately and heavily loaded Gr/Pi panels.

Weaver, G. G., II↗
NASA NTRS1980

Theoretical studies of massive stars. II - Evolution of a 15 solar-mass star from carbon shell burning to iron core collapse

The evolution of a Population I star of 15 solar masses is described from the carbon shell burning stage to the formation and collapse of an iron core. An unusual aspect of the evolution is that neon ignition occurs off-center and neon burning propagates inward by a series of shell flashes. The extent of the core burning is generally smaller than the Chandrasekhar mass, so that most of the nuclear energy generation occurs in shell sources. Because of degeneracy and the influence of rapid convective mixing, these shell sources are unstable and the core goes through large excursions in temperature and density. The small core also causes the shell sources to converge into a narrow mass region slightly above the Chandrasekhar mass. Thus, the final nucleosynthesis yields are generally small, with silicon being most strongly enhanced with respect to solar system abundances.

Sparks, W. M.↗
NASA NTRS1980

Mass transfer between binary stars

The transfer of mass from one component of a binary system to another by mass ejection is analyzed through a stellar wind mechanism, using a model which integrates the equations of motion, including the energy equation, with an initial static atmosphere and various temperature fluctuations imposed at the base of the star's corona. The model is applied to several situations and the energy flow is calculated along the line of centers between the two binary components, in the rotating frame of the system, thereby incorporating the centrifugal force. It is shown that relatively small disturbances in the lower chromosphere or photosphere can produce mass loss through a stellar wind mechanism, due to the amplification of the disturbance propagating into the thinner atmosphere. Since there are many possible sources of the disturbance, the model can be used to explain many mass ejection phenomena.

Modisette, J. L.↗
NASA NTRS1980

Cerenkov x total energy telescopes for the study of the mass composition of cosmic rays

The mass resolution attainable with cosmic ray telescopes employing Cerenkov counters for velocity measurement was examined. It is shown that in most cases, the limiting mass resolution is determined by the resolution of the Cerenkov counter. The resolution achieved in the UNH telescope flown on a balloon in 1977 is studied as a function of charge and energy. This telescope determines the mass using the Cerenkov x total energy technique. It is shown that the mass resolution for heavier nuclei can be accurately predicted using the response of the Cerenkov counter to sea level mu-mesons. The actual in flight resolution for heavier nuclei, including broadening effects, may be predicted using the beta = 1 Cerenkov distributions, and independently by studying the distribution function of the differences of the two banks of photomultipliers employed on each Cerenkov counter.

Webber, W. R.↗