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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Mass spectrometry and inhomogeneous ion optics

Work done in several areas to advance the state of the art of magnetic mass spectrometers is described. The calculations and data necessary for the design of inhomogeneous field mass spectrometers, and the calculation of ion trajectories through such fields are presented. The development and testing of solid state ion detection devices providing the capability of counting single ions is discussed. New techniques in the preparation and operation of thermal-ionization ion sources are described. Data obtained on the concentrations of copper in rainfall and uranium in air samples using the improved thermal ionization techniques are presented. The design of a closed system static mass spectrometer for isotopic analyses is discussed. A summary of instrumental aspects of a four-stage mass spectrometer comprising two electrostatic and two 90 deg. magnetic lenses with a 122-cm radius used to study the interaction of ions with solids is presented.

White, F. A.↗
NASA NTRS1973

Mass influx obtained from low-light-level television observations of faint meteors

Low light level television systems offer the ability to observe meteors as faint as 10th magnitude which allows the extension of optical meteor data to masses as small as 0.0001 gram. The results of these observations, using image orthicons and intensified vidicons, are presented along with an interpretation in terms of mass flux. This interpretation includes the development of a relationship between peak luminosity of a meteor and mass, velocity, and zenith angle that was derived from single body meteor theory and compares favorably with results obtained from the artificial meteor program. Also included in the mass flux interpretation is an analysis of the observation response of a LLLTV system to fixed and moving point sources.

Naumann, R. J.↗
NASA NTRS1974

Current constraints on hidden mass in the Coma Cluster

Various possible means of accounting for the dynamical mass of the Coma Cluster are reviewed. We intentionally choose to emphasize conventional forms of hidden mass, specifically gas and low-luminosity stars, while adopting conventional mass-to-luminosity ratios for the observed luminous material in galaxies. We have attempted to combine all previous work relating to assumed gas parameters in order to examine precisely what constraints current observations, together with theoretical and observational upper limits, place on any gas in the Coma Cluster. In particular, we make use of a density distribution function that is consistent with the dynamical data and express all constraints in a manner which explicitly displays their dependence on Hubble constant, current observational flux levels, distance from the dynamical center of the cluster, and the mass of gas postulated.

Tarter, J.↗
NASA NTRS1975

The occultation of beta Scorpii by Jupiter. VI - The masses of beta Scorpii A1 and A2

From images of the spectroscopic binary beta Sco A, formed by the Jovian atmosphere during its 1971 May 13 occultation by Jupiter, the angular separation of the binary components was found to be 0.001496 plus of minus 0.000018 arcsec. The combination of this measurement, the elements of the spectroscopic orbit, and the parallax determination of Bertiau (1958) yields masses of 21.1 plus or minus 3.2 solar masses for the primary (B0.5 V) and 12.7 plus or minus 1.9 solar masses for the secondary. New observations are suggested for improving the accuracy of the mass determinations.

Elliot, J. L.↗
NASA NTRS1975

Stellar evolution at high mass with semiconvective mixing according to the Ledoux criterion

The effects of semiconvective mixing are investigated in evolutionary sequences of models for stars of 10, 15, and 30 solar masses with four different initial chemical compositions. The models are constructed using the Ledoux criterion for both the definition of convective instability and the state of convective neutrality assumed to be attained in regions with a gradient of mean molecular weight. It is shown that semiconvection is nonexistent at 10 solar masses, of minor importance at 15 solar masses, but covers most of the intermediate zone at 30 solar masses, developing into full convection if the initial hydrogen and metals abundances are high. The effects of low initial hydrogen and metals abundances are examined, and the critical importance is demonstrated of the depths of the semiconvective zone and the outer convective envelope in promoting a blue loop and determining the maximum effective temperature on the loop. The extent of the thermally stable stages of the blue-loop phase is determined.

Stothers, R.↗
NASA NTRS1975

Postmission plasma volume and red-cell mass changes in the crews of the first two Skylab missions

Red-cell mass determinations were performed before and after the first two Skylab missions. The data showed a 14% mean decrease in red-cell mass after the 28-day mission and a 12% mean decrease after the 59-day mission. The red-cell mass returned to premission levels more slowly after the shorter (28-day) than after the longer mission. Plasma volume decreases were found after each mission, with the crew from the longer mission showing the greater change (13% vs 8.4%). Postmission decreases in red-cell mass and plasma volume have been a general finding in crewmen who return from short or long spaceflight.

Johnson, P. C.↗
NASA NTRS1975

Mean rates of the orbital elements of a satellite perturbed by a lens shaped mass concentration

Long arc gravity analysis of lunar orbiter tracking data in the past has been carried out with the help of averaged equations of motion, in which short period effects have been suppressed. This procedure has required that the harmonic terms in the gravity potential be averaged over an orbital period. In the present paper, this technique is extended to mass points and mass disks in the gravity field. This requires the evaluation of expressions for the mean rates of the orbit elements for a satellite perturbed by a lens shaped mass concentration. Corresponding expressions for the perturbations due to a mass point are obtained in the limit as the lens radius goes to zero. The derived equations have been programmed on the UNIVAC 1108 computer, and the results checked by numerical differencing.

Ananda, M.↗
NASA NTRS1976

On the detection of a cometary mass distribution

The problem of detecting a possible cometary distribution on the fringes of the solar system is examined. The acceleration of a space probe due to a hypothetical cometary mass distribution with the surface density rising to a maximum and subsequently falling off with increasing distance from the sun is analyzed. The total minimum detectable cometary mass for the Pioneer and Mariner spacecraft is estimated on the basis of this model to be on the order of 1000 earth masses. Precision tracking of deep space probes is less sensitive by three orders of magnitude for the detection of an unseen cometary mass distribution at the fringes of the solar system than are the secular perturbations of long-period comets.

Boss, A. P.↗
NASA NTRS1976

The 3U 0900-40 binary system - Orbital elements and masses

Observations of the 283-s X-ray pulsations from 3U 0900-40 (Vela X-1) over a 36-day interval have led to a determination of the orbital elements for the X-ray star. These elements yield an X-ray mass function of about 18.5 solar masses and, when combined with the results of optical studies of the companion star HD 77581, give a probable lower limit of 1.4 solar masses to the mass of the X-ray star.

Rappaport, S.↗
NASA NTRS1977

Design and fabrication of a basic mass analyzer and vacuum system

A two-inch hyperbolic rod quadrupole mass analyzer with a mass range of 400 to 200 amu and a sensitivity exceeding 100 packs per billion has been developed and tested. This analyzer is the basic hardware portion of a microprocessor-controlled quadrupole mass spectrometer for a Gas Analysis and Detection System (GADS). The development and testing of the hyperbolic-rod quadrupole mass spectrometer and associated hardware are described in detail.

Judson, C. M.↗
NASA NTRS1976

A survey of mass loss from Be and shell stars using ultraviolet data from Copernicus

Ultraviolet spectra of intermediate resolution have been obtained with Copernicus of twelve objects classified as Be or shell stars, and an additional 19 dwarfs of spectral classes B0-B4. Some of these spectra show marked asymmetries in certain resonance lines, especially the Si IV doublet at 1400 A, indicating the presence of outflowing material with maximum velocities of nearly 1000 km/sec. Direct evidence for mass loss at these velocities is seen for the first time in dwarf stars as late as B1.5. Later than B0.5, the only survey objects showing this phenomenon are Be stars. Among the stars considered there is a correlation between the presence of mass-loss effects and projected rotational velocity, suggesting that the UV flux from B1-B3 dwarfs is sufficient to drive high-velocity stellar winds only if rotation reduces the effective gravity near the equator. The role of mass-loss in producing the Be star phenomenon and the effects of rotation on mass loss are discussed.

Marlborough, J. M.↗
NASA NTRS1976

Orbital elements and masses for the SMC X-1/Sanduleak 160 binary system

The binary X-ray source SMC X-1 was observed with the SAS-3 satellite for approximately four days (February 26-29, 1976). Sufficient timing data were obtained on the 0.71 s X-ray pulsations to measure the Doppler velocity curve of the X-ray source and thereby derive orbital and stellar parameters for the system. The projected velocity of the X-ray star is 301.5 plus or minus 2.0 (1 sigma) km/s, and the corresponding mass function is 11.05 plus or minus 0.22 (1 sigma) solar masses. Combining the X-ray timing data with constraints imposed by the X-ray eclipse duration and the available optical data on Sk 160, a range of allowable values of not less than 1.1 and not greater than 4.0 solar masses for the mass of the X-ray star is obtained.

Primini, F.↗
NASA NTRS1977

High-resolution stellar vidicon spectrophotometry. I - Variable mass loss from Arcturus and the hypothesis of giant convective elements

High-resolution spectrophotometry of the variable Ca II K line in the K2 IIIp star Alpha Boo was performed with the McMath Solar Telescope at Kitt Peak National Observatory and an experimental SEC vidicon camera. The results are compared with Copernicus observations of the Mg II h and k lines and with earlier Ca II data. It is found that either of two states may typically occur in the Arcturus chromosphere. From comparison with the results of model calculations for expanding chromospheres, it is concluded that these correspond respectively to a 'normal' state in which the mass loss is less than one billionth of a solar mass per year and an 'abnormal' state in which the mass loss is about 8 billionths of a solar mass per year. In the latter case, the expansion velocity is around 13 km/s at optical depth unity in the K-line, which exceeds the local sound speed. It is suggested that the abnormal state represents the rise to the photosphere of a very large convective element, as hypothesized for red giants by Schwarzschild (1975).

Chiu, H. Y.↗
NASA NTRS1976

Mass ejection from the O4f star Zeta Puppis

Profiles of P Cygni lines and displaced absorption lines observed in high-resolution Copernicus UV scans of Zeta Pup from 907 to 1738 A are compared with profile calculations to derive an optical-depth scale of the lines as a function of height or velocity in the expanding envelope. The degrees of ionization of the elements C, N, O, Si, and S under equilibrium conditions at electron temperatures of 20,000 to 1 million K, radiation temperatures of 20,000 to 50,000 K, and electron number densities of 100 million to 1 trillion per cu cm are computed with a dilution factor of 0.1, taking into account collisional ionization by electrons, radiative ionization from the ground state, radiative recombination, and dielectric recombination. Observed and predicted relative ionization fractions are then compared to determine the electron and radiation temperatures. Crude and refined estimates of the mass-loss rate and velocity law are made, and radiative acceleration in the expanding envelope is analyzed. The derived model for Zeta Pup is found to have a mass-loss rate of about 7.2 millionths of a solar mass per year, a wind velocity that increases slowly outward and reaches 700 km/s about 28 solar masses, and a nearly isothermal envelope with an electron temperature of approximately 200,000 K.

Lamers, H. J. G. L. M.↗
NASA NTRS1977

Guidance and trajectory considerations in lunar mass transportation

Flight-mechanics problems associated with large-scale transport of lunar mass to a space colony or manufacturing facility are discussed. The proposed transport method involves launch of payloads from a mass-driver on the lunar surface, onto ballistic trajectories to a passive mass-catcher located near the L2 libration point, with the caught mass subsequently being transported to the colony. Arrival velocities at L2, sensitivities in arrival dispersion due to launch errors, and effects of launch site location are treated, via numerically integrated orbits in the restricted three-body problem. From any launch site it is possible to define a target point reached with zero dispersion due to errors in a selected component of launch velocity. Effects of lunar geometrical librations and of obliquity, as well as the conditions for biasing a trajectory away from L2 so as to reduce stationkeeping costs, are dealt with along with transfer orbits from L2 to the colony. The theory of capture and the theory of resonance lead to a colony orbit, with period approximately two weeks, reached from L2 with velocity increment as low as 9.02 m/sec.

Heppenheimer, T. A.↗
NASA NTRS1976

A survey of mass-loss effects in early-type stars

Intermediate-resolution data obtained with the Copernicus satellite are surveyed in order to define the region in the H-R diagram where mass loss occurs. The survey includes 40 stars, providing good coverage of supergiants from O4 to A2 and main-sequence stars from O4 to B7 as well as spotty coverage of late O giants and intermediate to late B stars. The spectral transitions examined are primarily resonance lines of ions of abundant elements plus some lines arising from excited states (e.g., C III at 1175.7 A and Si IV at 1122.5 A). Observed P Cygni profiles are discussed along with interesting features of some individual profiles. The data are shown to indicate that mass-loss effects occur over a wide portion of the H-R diagram, that mass ejection generally occurs when the holometric magnitude is greater than -6.0, and that the mass-ejection rate is usually high enough to produce P Cygni profile whenever the N V feature at 1240 A is present in a spectrum.

Snow, T. P., Jr.↗
NASA NTRS1977

Mass driver retrievals of earth-approaching asteroids

Mass driver tugs can be designed to move Apollo and Amor asteroids at opportunities of low velocity increment to the vicinity of the earth. The cost of transferring asteroids through a velocity interval of 3 km/sec by mass driver is about 16 cents per kilogram amortized over 10 years, about ten times less than that required to retrieve lunar resources during the early phases of a program of space manufacturing. About 22 per cent of a 200-meter diameter asteroid could be transferred to high earth orbit by an automated 100 megawatt solar-powered mass driver in a period of five years for a cost of approximately $1 billion. Estimates of the total investment of a space manufacturing program could be reduced twofold by using asteroidal instead of lunar resources; such a program could begin several years sooner with minimal concurrent development if asteroidal search programs and mass driver development are immediately accelerated.

Oleary, B.↗
NASA NTRS1977

Mass spectrometer beam system for applications in the stratosphere

A special gas inlet system is required for reduction of high ambient pressures to ion source operating pressures for mass spectrometer investigations in the stratosphere for the determination of the abundance of minor constituents. A system has been designed which combines a mass spectrometer and a gas inlet system reducing pressure by differential pumping using high-speed liquid helium pumps and small orifices. The gas particles are formed into a neutral beam with a flag mechanism proceeding into the mass spectrometer ion source where they are ionized for subsequent mass separation. A laboratory model has been tested under conditions simulating stratospheric pressures. It was shown that the process is able to identify gases with abundances below 10 to the -8th. Some of the problems associated with gas analysis of trace constituents have been alleviated, and other applications of the system have been identified, such as pollution control and medicine.

Mauersberger, K.↗