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At least 973 records · Page 54

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NASA NTRS1978

Balloon-borne photoionization mass spectrometer for measurement of stratospheric gases

A balloon-borne photoionization mass spectrometer used to measure stratospheric trace gases is described. Ions are created with photons from high-intensity krypton discharge lamps and a quadrupole mass analyzer is employed for ion identification. Differential pumping is achieved with liquid helium cryopumping. To insure measurement of unperturbed stratospheric air, the entire system is contained in a sealed gondola and the atmospheric sample is taken some distance away during descent. The photoionization technique allows the detection of a low ionization potential constituent, such as nitric oxide, at less than a part in one billion in the presence of the major atmospheric gases and their isotopes. Operation of the mass spectrometer system was demonstrated during a daytime flight from Palestine, Texas on 26 April 1977. The sensitivity achieved and the unique selectivity afforded by this technique offer a capability for trace constituent measurement not possible with the more conventional electron impact ionization approach.

Aikin, A. C.↗

NASA NTRS1975

Farside lunar gravity from a mass point model

A mass point representation of the lunar gravity field was determined from the long-period orbital variations of the Apollo 15 and 16 subsatellites and Lunar Orbiter V. A radial acceleration contour map, evaluated at 100 km altitude from the lunar surface, shows that the nearside is in close agreement with the result derived from the line of sight method by Muller and Sjogren. The farside map shows the highland regions as broad positive gravity anomaly areas and the basins such as Korolev, Hertzsprung, Moscoviense, Mendeleev, and Tsiolkovsky as localized, negative gravity anomaly regions. The farside map has a first-order agreement with the result derived from the harmonic field method by Ferrari. The mass points analysis indicates that the nearside is almost all negative gravity anomaly regions except for the known positive mass anomaly basins (mascons) and the farside is almost all positive gravity anomaly regions except for some localized negative areas near the basins.

Ananda, M.↗

NASA NTRS1977

Mass ejections from the solar corona into interplanetary space

Data are presented that show that during the Skylab era, mass ejections from the solar corona probably contributed at least 3% of the mass flux from the sun. The frequency of the transients is expected to increase with overall activity in the solar cycle, so more than 10% of the sun's mass efflux will be in the form of ejections at solar cycle maximum.

Hildner, E.↗

NASA NTRS1978

Bump Cepheids - The mass anomaly as an opacity effect

Nonlinear calculations of models for bump Cepheids indicate that most of the basic features of these stars can be reproduced well by models having normal to nearly normal evolutionary masses and normal helium abundances, if Carson's opacities are adopted. The trends of the properties of the models with various physical parameters are otherwise very similar to those obtained by other authors with the Los Alamos opacities (which have led to Cepheid masses of half the evolutionary masses). Difficulties with the resonance hypothesis of Simon and Schmidt as an explanation of the bump are discussed.

Sastri, V. K.↗

NASA NTRS1978

Time variation of urban mass loading measured by small filters compared to high-volume samplers

The paper shows how the use of an instrument with 12 small-diameter (47-mm) membrane filters (samples taken for 12 2-hr periods), in conjunction with wind direction measurements, is a suitable technique for observing mass loading levels on a time-resolved basis. In contrast, standard high-volume instruments are unable to demonstrate specialized events because of the long collection period involved. A comparison is presented for a typical day where the mass loading changed during the observed period but could not be observed with a single high-volume sample measurement. Time-averaged mass loading for 2-hr periods is demonstrated to be a useful tool in developing trend analysis for diurnal effects.

Crumbly, K. H.↗

NASA NTRS1978

Real time mass flow computer for Arc Jet Wind Tunnel

Experiments at the Arc Jet Tunnel at Ames Research Center have typical run times of 5-10 sec during which the test model is subjected to an environment simulating reentry into Jupiter. Previous real-time determination of mass flow required off-line manual computations from taped or strip chart data. The present paper describes a computer which provides personnel with real-time computations of mass flow. Using an 8-bit microprocessor and standard TTL interface circuitry, the unit interrogates temperature and pressure instruments with other parameters to compute mass flow.

Vidal, J.↗

NASA NTRS1978

Small mass spectrometer with extended measurement capabilities at high pressures

For the in situ investigation of planetary atmospheres a small Mattauch-Herzog mass spectrometer has been developed. Its high-pressure performance has been improved by incorporating differential pumping between the ion source and the analyzing fields, shortening the path-length as well as increasing the extraction field in the ion source. In addition doubly ionized and dissociated ions are used for mass analysis. These measures make possible operation up to 0.01 millibars. Results of laboratory tests related to linearity, dynamic range, and mass resolution are presented, in particular for CO2.

Von Zahn, U.↗

NASA NTRS1979

Global model of longitude/UT variations in thermospheric composition and temperature based on mass spectrometer data

Measurements of N2, O, He, and Ar densities from neutral gas mass spectrometers on four satellites and inferred O2 and H densities from an ion mass spectrometer have been combined to produce a model of longitude/UT variations in thermospheric neutral composition and temperature. The longitude/UT model is an extension of the mass spectrometer-incoherent scatter thermospheric model (Hedin et al., 1977) and uses spherical harmonic terms dependent on geographic latitude, longitude, and UT. The combined longitude and UT variations reflect the influence of the geomagnetic field but indicate that the variations may not simply be represented in magnetic coordinates.

Hedin, A. E.↗

NASA NTRS1979

Mass Driver Two - Cryogenic module

The cryogenic module of Mass Driver Two comprises a 3.25 inch (82.55 mm) OD bucket with two 44 kilo-ampere-turn coils made with .028 inch (.71 mm) diam niobium-titanium multi-filamentary cable in a copper matrix, impregnated with lead alloy for thermal inertia, as well as the service station to refrigerate, energize and eject the bucket. The station is housed in a six inch flanged pyrex cross which connects to the four inch pyrex tube of the mass driver itself. The bucket is refrigerated by being forced against a copper braid cradle attached to the bottom of a liquid helium reservoir which protrudes into the cross from above. The bucket is energized inductively by turning off two superconducting coils which are also attached to the helium reservoir, and which have maintained the correct flux linkage through the bucket coils during their cool-down through the critical temperature. Once charging is completed, the clamping pressure is released and the bucket is injected into the mass driver by means of two normal-conductor pulse coils surrounding the horizontal branches of the cross.

Fine, K.↗

NASA NTRS1979

Comparison of atmospheric density data from mass spectrometers and atmospheric drag on the Aeros satellites

The comparison of perigee density data near 230 km for satellite Aeros-A has been extended to the complete mission time. The average ratio between orbital drag derived density and mass spectrometer measurements is very near to 1 with a large scatter reflected by a standard deviation of the order of 20%. A method of comparison was developed and tested which uses the observed rate of change of orbital period in comparison with the orbital decay computed from the actual mass spectrometer data measured at discrete positions along the orbit. This method proves that deviations from the average ratio of 1 between perigee densities from drag and mass spectrometers are due to the smoothing and poor resolution of the orbital drag technique.

Roemer, M.↗

NASA NTRS1980

Triple mode Cepheid masses

Unconventional composition structures are proposed to explain the periods of the triple mode Cepheid aC And. A strong Cepheid wind appears to enrich helium in the convection zones down to about 60,000 K or 70,000 K. Then some downward partial mixing occurs to the bottom of a layer with about 1-q = .0005 of the stellar mass. It was found that AC And was not unlike anomalous Cepheids. However, masses of betwen one and two solar masses are suggested and the population is more likely a type two.

King, D. S.↗

NASA NTRS1980

Mass loss of a TEOS-coated, reinforced carbon-carbon composite subjected to a simulted shuttle entry environment

Coated, reinforced carbon-carbon (RCC) is used for the leading edges of the space shuttle. The mass loss characteristics of RCC specimens coated with tetraethyl orthosilicate (TEOS) were determine for conditions which simulated the environment expected at the lug attachment area of the leading edge. Mission simulation included simultaneous application of load, temperature, and oxygen partial pressure. Maximum specimen temperature was 900 K (1160 F). Specimens were exposed for up to 80 simulated missions. Stress levels up to 6.8 MPa (980 psi) did not significantly affect the mass loss characteristics of the TEOS-coated RCC material. Mass loss was correlated with the bulk density of the specimens.

Stroud, C. W.↗

NASA NTRS1980

History of the mass of Mercury

A historical investigation reveals that Newcomb omitted to complete the calculation for the mass of mercury which would have given 8,405,291(-1), but instead arbitrarily adopted a value of 6,000,000(-1). This baseless figure 6000000(-1) became generally accepted and adopted in subsequent attempts to improve the mass. That only small changes have emerged is likely to be no more than a consequence of relying on a least squares process. Reduction of the Mercury mass to 9,000,000(-1) would alter theoretical angular positions of Venus by less than inherent observational errors, but the theoretical distances would be changed by amounts probably capable of detection by radar means.

Lyttleton, R. A.↗

NASA NTRS1979

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

Mass flux measurements associated with choked flows through four Borda-type inlet geometries: circular, square, triangular, and rectangular (two-dimensional) and two sharp-edged geometries are discussed for a wide range of inlet stagnation conditions. The results obtained indicate that the mass flux is independent of the inlet cross-section geometry, while it is dependent on the inlet stagnation conditions. The results also suggest that parallel surfaces as found in seals, dampers, bearings, and heat exchanger tubes of rectangular cross section with Borda-type inlet configurations are subject to large forces. It is noted that the reduced mass flux is independent of working fluid.

Hendricks, R. C.↗

NASA NTRS1979

Influence of a weak gravitational wave on a bound system of two point-masses

The problem of a weak gravitational wave impinging upon a nonrelativistic bound system of two point masses is considered. The geodesic equation for each mass is expanded in terms of two small parameters, v/c and dimensionless wave amplitude, in a manner similar to the post-Newtonian expansion; the geodesic equations are resolved into orbital and center-of-mass equations of motion. The effect of the wave on the orbit is determined by using Lagrange's planetary equations to calculate the time evolution of the orbital elements. The gauge properties of the solutions and, in particular, the gauge invariance of the secular effects are discussed.

Turner, M. S.↗

NASA NTRS1979

Mass-radius relationships in icy satellites

Using published laboratory data for H2O ice, a modeling technique was developed by which the bulk density, density and temperature profile, rotational moment of inertia, central pressure, and location of the rock-ice interface can all be obtained as a function of the radius, the heliocentric distance, and the silicate composition. Models of the interiors of Callisto, Ganymede, Europa, Rhea, and Titan are given, consistent with present mass and radius data. The radius and mass of spheres of ice under self-gravitation for two different temperature classes are given (103 and 77 deg K). Measurements of mass, radius and I/MR2 by spacecraft can be interpreted by this model to yield substantial information about the internal structure and the ice/rock ratio of the icy satellites of Jupiter and Saturn.

Lupo, M. J.↗

NASA NTRS1979

A new approach to the correlation of boundary layer mass transfer rates with thermal diffusion and/or variable properties

A rational approach to the correlation of boundary layer mass transport rates, applicable to many commonly encountered laminar flow conditions with thermal diffusion and/or variable properties, is outlined. The correlation scheme builds upon already available constant property blowing/suction solutions by introducing appropriate correction factors to account for the additional ('pseudo' blowing and source) effects identified with variable properties and thermal diffusion. Applications of the scheme to the particular laminar boundary layer mass transfer problems considered herein (alkali and transition metal compound vapor transport) indicates satisfactory accuracy up to effective blowing factors equivalent to about one third of the 'blow off' value. As a useful by-product of the variable property correlation, we extend the heat-mass transfer analogy, for a wide range of Lewis numbers, to include variable property effects.

Srivastava, R.↗

NASA NTRS1979

Preliminary estimates of mass loss from O-type stars

P Cygni profiles of C IV resonance lines (observed for O-type stars) taken with the high resolution spectrograph on IUE are presented, and data indicate that terminal velocity is proportional to photospheric escape velocity. Parameters determining these line profiles are stellar radius, mass loss rate, the velocity law, the abundance (assumed to be solar) of the absorbing ion, and atomic parameters such as wavelength and oscillator strength, while the ionization fraction is assumed to be the same as that of Zeta Pup (Lamers and Morton, 1976). Thus an electron temperature of 200,000 K, a radiation temperature of 30,000 K and an electron density of 10 to the 10th are adopted. It is concluded that mass loss rates are considerably lower in O stars than in Of stars, but that if mass loss is really proportional to luminosity, the earliest O stars should have rates at least a factor of 10 higher than were found.

Conti, P. S.↗