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NASA NTRSDate not supplied

Mass Modeling of NEP Power Conversion Concepts for Human Mars Exploration

The specific mass (mass per unit of electric power output) of an NEP power conversion system is an important metric for the performance and feasibility of a crewed NEP vehicle. This work explores a component level buildup of the specific mass for a crewed NEP vehicle. The buildup is highly parametric and avoids being tied to specific technologies where practical. This allows the specific mass to be calculated for a variety of assumptions and operating conditions and be used to optimize particular design variables or compare different system configurations. The values of specific mass are dependent on assumptions with significant uncertainty; comparison between cases and trends observed in the models are the main goal of the work presented here. To demonstrate the level of insight this type of modeling can provide, the impacts of compressor inlet temperature, turbine inlet temperature, and radiator pressure drop on specific mass are explored. In addition, the specific mass can be used to assess the benefit of separating the radiator and reactor loop from the power conversion cycle.

NEP↗

NASA NTRSDate not supplied

Mass Modeling of NEP Power Conversion Concepts for Human Mars Exploration

nep↗

NASA NTRS2023

Propellant Mass Gauging in Microgravity with Electrical Capacitance Tomography

Advancements in microgravity propellant mass gauging will result in improvements to many areas of propellant management, which influences space vehicle performance and mission assurance. Propellant mass gauging technologies designed to work in an accelerated environment, where the propellant remains settled at one end of the propellant tank, do not always work well in a microgravity environment because the propellant is not necessarily settled. While some microgravity mass gauging technologies exist at various stages of development, most of them have major disadvantages. Electrical Capacitance Tomography (ECT) is a sensing technology that is able to reconstruct the liquid distribution inside of a tank, which can then be integrated to obtain mass. While ECT mass gauging will theoretically work during all phases of flight, it had not yet been tested in microgravity. The NASA Kennedy Space Center Launch Services Program, with support from the Flight Opportunities Program, successfully tested an ECT liquid mass gauging system experiment on a parabolic flight aircraft in May 2022. Basics of ECT measurement theory, details of the experiment setup, data processing, ground test results, and the flight test result will be discussed. The results suggest that ECT sensor systems will be useful as a propellant mass gauging technology in both accelerated and microgravity environments.

electrical capacitance tomography↗

NASA NTRS2022

Constraining the Physical Properties of Stellar Coronal Mass Ejections with Coronal Dimming: Application to Far-ultraviolet Data of є Eridani

Coronal mass ejections (CMEs) are a prominent contributor to solar system space weather and might have impacted the Sun's early angular momentum evolution. A signal diagnostic of CMEs on the Sun is coronal dimming: a drop in coronal emission, tied to the mass of the CME, that is the direct result of removing emitting plasma from the corona. We present the results of a coronal dimming analysis of Fe XII 1349 Å and Fe XXI 1354 Å emission from ϵ Eridani ( ϵ Eri), a young K2 dwarf, with archival far-ultraviolet observations by the Hubble Space Telescope's Cosmic Origins Spectrograph. Following a flare in 2015 February, ϵ Eri's Fe XXI emission declined by 81 ± 5%. Although enticing, a scant 3.8 minutes of preflare observations allows for the possibility that the Fe XXI decline was the decay of an earlier, unseen flare. Dimming nondetections following each of three prominent flares constrain the possible mass of ejected Fe XII-emitting (1 MK) plasma to less than a few × 10 15 g. This implies that CMEs ejecting this much or more 1 MK plasma occur less than a few times per day on ϵ Eri. On the Sun, 10 15 g CMEs occur once every few days. For Eri, the mass-loss rate due to CME-ejected 1 MK plasma could be < 0.6 Ṁ Ꙩ well below the star's estimated 30 Ṁ Ꙩ mass-loss rate (wind + CMEs). The order-of-magnitude formalism we developed for these mass estimates can be broadly applied to coronal dimming observations of any star.

Stellar coronal mass ejections↗

NASA NTRS1972

Mass spectrometry.

Review of the current state of mass spectrometry, indicating its unique importance for advanced scientific research. Mass spectrometry applications in computer techniques, gas chromatography, ion cyclotron resonance, molecular fragmentation and ionization, and isotope labeling are covered. Details are given on mass spectrometry applications in bio-organic chemistry and biomedical research. As the subjects of these applications are indicated alkaloids, carbohydrates, lipids, terpenes, quinones, nucleic acid components, peptides, antibiotics, and human and animal metabolisms. Particular attention is given to the mass spectra of organo-inorganic compounds, inorganic mass spectrometry, surface phenomena such as secondary ion and electron emission, and elemental and isotope analysis. Further topics include mass spectrometry in organic geochemistry, applications in geochronology and cosmochemistry, and organic mass spectrometry.

Burlingame, A. L.↗

NASA NTRS1971

Lunar orbital mass spectrometer experiment

The design, development, manufacture, test and calibration of five lunar orbital mass spectrometers with the four associated ground support equipment test sets are discussed. A mass spectrometer was installed in the Apollo 15 and one in the Apollo 16 Scientific Instrument Module within the Service Module. The Apollo 15 mass spectrometer was operated with collection of 38 hours of mass spectra data during lunar orbit and 50 hours of data were collected during transearth coast. The Apollo 16 mass spectrometer was operated with collection of 76 hours of mass spectra data during lunar orbit. However, the Apollo 16 mass spectrometer was ejected into lunar orbit upon malfunction of spacecraft boom system just prior to transearth insection and no transearth coast data was possible.

Lord, W. P.↗

NASA NTRS1975

On the lower mass limit for the carbon detonation scenario

The lower mass limit for carbon detonation (about 4 solar masses) is due to an argument by Paczynski (1970) that stars in the range between 1.4 and 3.5 solar masses will lose their envelopes prior to carbon detonation. This argument is based on two criteria for mass loss: (1) the envelope is unstable to adiabatic oscillations, and (2) the total energy of the envelope is positive. Recent hydrodynamic calculations of red-giant envelopes have shown that the envelopes are highly nonadiabatic and that the second criterion is not a sufficient condition for mass loss. Thus, a calculation which takes into account the nonadiabatic nature of the envelope is required in order to determine the lower mass limit for carbon detonation. This lower mass limit is directly related to the formation mechanisms and statistics of supernovae and pulsars.

Endal, A. S.↗

NASA NTRS1976

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

Evolutionary sequences for stellar models with 10, 15, 30, and 60 solar masses, as well as four different initial chemical compositions, are calculated to the end of core helium burning using the Schwarzschild criterion for convection. The results are analyzed in terms of the modifications of interior structure and surface parameters induced by semiconvective mixing as a result of adopting the Schwarzschild criterion. It is found that the main differences from results based on the Ledoux criterion are the great extent of the convectively unstable layers in the intermediate zone and the eventual development of a fully convective zone at the base of the semiconvective one. It is shown that semiconvection develops outside the convective core just after the ZAMS stage for masses greater than 12 solar masses and just before the stage of central hydrogen exhaustion for masses greater than 6 solar masses. The present models are found to be insufficiently hot in comparison with the bulk of observed stable blue supergiants and to predict far too many red supergiants fro the range above 20 solar masses. It is concluded that something is fundamentally wrong with the models, the most likely suspects being the stellar opacities adopted and the neglect of mass loss.

Stothers, R.↗

NASA NTRS1977

Mass ejections from the solar corona into interplanetary space

Results obtained from analysis of Skylab coronagraph images of mass ejections from the solar corona are reviewed which demonstrate the importance of mass-ejection coronal transients to the interplanetary medium and which support the belief that magnetic forces are the primary mechanism driving mass ejections from the corona. Observations of 13 large ejection events are examined which indicate that coronal mass ejections contribute a nonnegligible fraction of the mass flux from the sun, especially toward the heliographic equator near the maximum of a solar activity cycle. It is shown that observed loop-shaped transients were associated with regions of increased magnetic field and with separations of unipolar field regions, that the forces driving the transients outward acted to great heights long after the onsets of the events, and that the behavior of the ejecta was magnetically controlled. It is concluded that mass ejections from the corona contributed at least 3% of the mass flux from the sun during the Skylab era and that the most common loop-shaped ejections are magnetically driven through the corona.

Hildner, E.↗

NASA NTRS1978

On the masses of giant molecular cloud complexes

A method of mass estimation for molecular clouds is presented which is based on approximate balance in the outer cloud layers between the cloud's gravitation, the galactic tide, and internal pressure. The largest observed clouds, which have greatest linear extents of 100 pc, are found to have masses of at least 200,000 solar masses. The cloud masses cannot exceed this lower limit by more than a factor of 3, or the velocity distributions of disk stars would be more relaxed than is actually observed. This implied upper limit to cloud masses combined with the galactic tide may be related to the absence of clouds at galactocentric radii less than 4 kpc. If Sagittarius B2 is bound, its mass must be more than 50 million solar masses.

Stark, A. A.↗

NASA NTRS1977

Mass drivers. 3: Engineering

This paper is the last of a series of three by the Mass-Driver Group of the 1977 Ames Summer Study. It develops the engineering principles required to implement the basic mass-driver design defined in paper I and as presented previously in the literature. Optimum component mass trade-offs are derived from a set of four input parameters, and the program used to design a lunar launcher. The mass optimization procedure is then incorporated into a more comprehensive mission optimization program called OPT-4, which evaluates an optimized mass-driver reaction engine and its performance in a range of specified missions. Finally, this paper discusses, to the extent that time permitted, certain peripheral problems: heating effects in buckets due to magnetic field ripple; an approximate derivation of guide force profiles; the mechanics of inserting and releasing payloads; the reaction mass orbits; and a proposed research and development plan for implementing mass drivers. This paper also considers further optimization that depends on advances in component technology beyond the present state. It is concluded that significant advantage can be gained in the case of small reaction engines with high emission velocity by developing lightweight packaging technology for silicon-controlled rectifiers (SCR's).

William H. Arnold↗

NASA NTRS1979

A statistical model for the initial stellar mass function

The nonlinear stages of the fragmentation of a collapsing molecular cloud are modeled by coagulation theory. Several distinct physical processes are discussed, including protostellar fragment coalescence, gas accretion, and binary formation. This work confirms and extends the earlier result of Nakano (1966) that an approximately self-similar limiting form of the mass spectrum develops after several mean initial collision times. An approximate solution to the velocity-averaged coagulation equation is given for an arbitrary power-law dependence of the coalescence rate on mass, with dimensional dependence proportional to m to the power lambda; i.e., the asymptotic mass spectrum varies as m to the -3 lambda/2 power at small masses and cuts off exponentially at large masses, the characteristic mass depending on the number of collision times elapsed. Simple physical arguments suggest that lambda may increase with increasing mass, but is restricted to the range from 2/3 to 4/3. A large fraction of collisions could result in binary formation.

Silk, J.↗

NASA NTRS1983

The mass of the Oort cloud

The total mass of comets in the Oort cloud is calculated. The distribution of cometary masses is found based on the observed distribution of cometary magnitudes corrected for observational selection effects by Everhart (1967), and a derived relationship between brightness and nucleus mass. A cloud population of 1.4 trillion comets brighter than an absolute magnitude of 11 as found by Weissman (1982) is used. The estimated total mass is 1.9 earth masses. The probable error in the estimate is about one order of magnitude. Most of the mass of the Oort cloud is concentrated in the size range of the observed long-period comets. The mass estimate is consistent with either cometary formation among the outer planets, or in satellite fragments of the primordial solar nebula.

Weissman, P. R.↗

NASA NTRS1983

Evidence linking coronal mass ejections with interplanetary magnetic clouds

Using proxy data for the occurrence of those mass ejections from the solar corona which are directed earthward, we investigate the association between the post-1970 interplanetary magnetic clouds of Klein and Burlaga and coronal mass ejections. The evidence linking magnetic clouds following shocks with coronal mass ejections is striking; six of nine clouds observed at Earth were preceded an appropriate time earlier by meter-wave type II radio bursts indicative of coronal shock waves and coronal mass ejections occurring near central meridian. During the selected periods when no clouds were detected near Earth, the only type II bursts reported were associated with solar activity near the limbs. Where the proxy solar data to be sought are not so clearly suggested, that is, for clouds preceding interaction regions and clouds within cold magnetic enhancements, the evidence linking the clouds and coronal mass ejections is not as clear; proxy data usually suggest many candidate mass-ejection events for each cloud. Overall, the data are consistent with and support the hypothesis suggested by Klein and Burlaga that magnetic clouds observed with spacecraft at 1 AU are manifestations of solar coronal mass ejection transients.

Wilson, R. M.↗

NASA NTRS1983

Mass loss rates and anisotropies in the outflows from late-type stars

It has been found that late-type giants and supergiants are losing large amounts of mass. However, it is still not known why these stars lose mass. In connection with the aim to understand this process, it is attempted to establish more accurate mass loss rates in order to consider in detail a popular model for mass loss, taking into account the hypothesis that radiation pressure on grains is important or even controls the mass outflows. This hypothesis can be tested by comparing measurements of the flux from the star, the mass loss rate, and the outflow velocity of the material. The largest uncertainty is related to the mass loss rate. Most models for interpreting the observations of these stars have been for spherically symmetric envelopes. However, highly anisotropic outflows have been observed. It is, therefore, one of the purposes of this investigation to study the importance of the anisotropy in the physical characteristics of the outflow. It is found that anisotropy does not greatly alter the important basic photochemical processes, and that radiation pressure on grains can be important.

Jura, M.↗

NASA NTRS1985

Real-time measurement of sodium chloride in individual aerosol particles by mass spectrometry

The method of particle analysis by mass spectrometry has been applied to the quantitative measurement of sodium chloride in individual particles on a real-time basis. Particles of known masses are individually introduced, in the form of a beam, into a miniature Knudsen cell oven (1600 K). The oven is fabricated from rhenium metal sheet (0.018 mm thick) and is situated in the ion source of a quadrupole mass spectrometer. A particle once inside the oven is trapped and completely volatilized; this overcomes the problem of partial volatilization due to particles bouncing from the filament surface. Individual particles are thermally volatilized and ionized inside the rhenium oven, and produce discrete sodium ion pulses whose intensities are measured with the quadrupole mass spectrometer. An ion pulse width of several milliseconds (4-12 ms) is found for particles in the mass range 1.3 x 10 to the -13th to 5.4 x 10 to the -11th g. The sodium ion intensity is found to be proportional to the particle mass to the 0.86-power. The intensity distribution for monodisperse aerosol particles possesses a geometric standard deviation of 1.09, showing that the method can be used for the determination of the mass distribution function with good resolution in a polydisperse aerosol.

Sinha, M. P.↗

NASA NTRS1986

The mass of the classical cepheid SU Cygni

Radial velocity differences between the classical Cepheid SU Cyg and a hot companion were measured from IUE high dispersion spectra. The blue star is itself a close binary. The triple system solution provides the mass ratio of the Cepheid to the masses of the pair of companions. The masses of the companions are inferred from the low dispersion IUE spectra. The mass derived for the Cepheid is 6.3 solar masses, with a range from 7.0 to 5.9 solar masses, which is very close to the evolutionary mass.

Evans, Nancy Remage↗

NASA NTRS1987

High mass star formation in the galaxy

The Galactic distributions of HI, H2, and HII regions are reviewed in order to elucidate the high mass star formation occurring in galactic spiral arms and in active galactic nuclei. Comparison of the large scale distributions of H2 gas and radio HII regions reveals that the rate of formation of OB stars depends on (n sub H2) sup 1.9 where (n sub H2) is the local mean density of H2 averaged over 300 pc scale lengths. In addition the efficiency of high mass star formation is a decreasing function of cloud mass in the range 200,000 to 3,000,000 solar mass. These results suggest that high mass star formation in the galactic disk is initiated by cloud-cloud collisions which are more frequent in the spiral arms due to orbit crowding. Cloud-cloud collisions may also be responsible for high rates of OB star formation in interacting galaxies and galactic nuclei. Based on analysis of the Infrared Astronomy Satellite (IRAS) and CO data for selected GMCs in the Galaxy, the ratio L sub IR/M sub H2 can be as high as 30 solar luminosity/solar mass for GMCs associated with HII regions. The L sub IR/M sub H2 ratios and dust temperature obtained in many of the high luminosity IRAS galaxies are similar to those encountered in galactic GMCs with OB star formation. High mass star formation is therefore a viable explanation for the high infrared luminosity of these galaxies.

Scoville, N. Z.↗