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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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NASA NTRS1996

Detectability of the Reflection Signal from Inner Planets

Mayor and Queloz (1996) and Marcy and Butler (1996) have found massive planets with orbital periods Tp=approx.4 days around two solar-like stars (51 Pegasi and v Andromeda). These planets are most likely similar in size and composition to the gas giants in our solar system (Burrows et al 1996). Based on this expectation and assuming the same albedo as Jupiter, we examined the feasibility of searching for similar planets with a dedicated space-based 1-m telescope. The Kepler mission will survey approximately 70,000 main-sequence dwarf stars from 9 to 14 mag continuously for four years to detect transiting Earthlike planets. Based on the detection statistics of Marcy and Butler, we expect to detect 1400 inner-orbit giant planets. Such planets in a much wider range of orbital inclinations (i) will produce nearly sinusoidal modulations of the star light flux due to the varying planetary phases. The relative signal amplitudes are of order 2x10(exp -5) and decrease as Tp(exp 4/3) for i >> 0deg. We estimated the expected signal to noise ratio (SNR) using the solar irradiance measurements from the ACRIM 1 experiment along with expected shot and detector noises. The figure shows SNR as a function of Tp for a 12 mag star, and indicates the planet radius required for detection. The survey will be sensitive to planets with periods from 12 hr to approx.8 days at the 6 sigma level.

Borucki, W. J.↗
NASA NTRS1995

High temperature kinetic study of the reactions H + O2 = OH + O and O + H2 = OH + H in H2/O2 system by shock tube-laser absorption spectroscopy

The reactions: (1) H + O2 = OH + O; and (2) O + H2 = OH + H are the most important elementary reactions in gas phase combustion. They are the main chain-branching reaction in the oxidation of H2 and hydrocarbon fuels. In this study, rate coefficients of the reactions and have been measured over a wide range of composition, pressure, density and temperature behind the reflected shock waves. The experiments were performed using the shock tube - laser absorption spectroscopic technique to monitor OH radicals formed in the shock-heated H2/O2/Ar mixtures. The OH radicals were detected using the P(1)(5) line of (0,0) band of the A(exp 2) Sigma(+) from X(exp 2) Pi transition of OH at 310.023 nm (air). The data were analyzed with the aid of computer modeling. In the experiments great care was exercised to obtain high time resolution, linearity and signal-to-noise. The results are well represented by the Arrhenius expressions. The rate coefficient expression for reaction (1) obtained in this study is k(1) = (7.13 +/- 0.31) x 10(exp 13) exp(-6957+/- 30 K/T) cu cm/mol/s (1050 K less than or equal to T less than or equal to 2500 K) and a consensus expression for k(1) from a critical review of the most recent evaluations of k(1) (including our own) is k(1) = 7.82 x 10(exp 13) exp(-7105 K/T) cu cm/mol/s (960 K less than or equal to T less than or equal to 5300 K). The rate coefficient expression of k(2) is given by k(2) = (1.88 +/- 0.07) x 10(exp 14) exp(-6897 +/- 53 K/T) cu cm/mol/s (1424 K less than or equal to T less than or equal to 2427 K). For k(1), the temperature dependent A-factor and the correlation between the values of k(1) and the inverse reactant densities were not found. In the temperature range of this study, non-Arrhenius expression of k(2) which shows the upward curvature was not supported.

Ryu, Si-Ok↗
NASA NTRS1992

Detection and period measurements of GX1+4 at hard x ray energies with the SIGMA telescope

The galactic Low Mass X ray Binary GX1+4 was detected by the coded aperture hard X ray gamma ray SIGMA telescope during the Feb. to April 1991 observations of the galactic center regions. The source, whose emission varied during the survey of a factor greater than 40 pct., reached a maximum luminosity in the 40 to 140 energy range of 1.03 x 10(exp 37) erg/s (D = 8.5 kpc), thus approaching the emission level of the 1970 to 1980 high state. Two minute flux pulsations were detected on Mar. 22 and on Mar. 31 and Apr. 1. Comparison with the last period measurements shows that the current spin-down phase of GX1+4 is ending. Concerning the proposed association of this source with the galactic center 511 keV annihilation emission, upper limits were derived.

Laurent, PH.↗
NASA NTRS1991

Fully autonomous navigation for the NASA cargo transfer vehicle

A great deal of attention has been paid to navigation during the close approach (less than or equal to 1 km) phase of spacecraft rendezvous. However, most spacecraft also require a navigation system which provides the necessary accuracy for placing both satellites within the range of the docking sensors. The Microcosm Autonomous Navigation System (MANS) is an on-board system which uses Earth-referenced attitude sensing hardware to provide precision orbit and attitude determination. The system is capable of functioning from LEO to GEO and beyond. Performance depends on the number of available sensors as well as mission geometry; however, extensive simulations have shown that MANS will provide 100 m to 400 m (3(sigma)) position accuracy and 0.03 to 0.07 deg (3(sigma)) attitude accuracy in low Earth orbit. The system is independent of any external source, including GPS. MANS is expected to have a significant impact on ground operations costs, mission definition and design, survivability, and the potential development of very low-cost, fully autonomous spacecraft.

Wertz, James R.↗
NASA NTRS1990

A scaling law of radial gas distribution in disk galaxies

Based on the idea that local conditions within a galactic disk largely determine the region's evolution time scale, researchers built a theoretical model to take into account molecular cloud and star formations in the disk evolution process. Despite some variations that may be caused by spiral arms and central bulge masses, they found that many late-type galaxies show consistency with the model in their radial atomic and molecular gas profiles. In particular, researchers propose that a scaling law be used to generalize the gas distribution characteristics. This scaling law may be useful in helping to understand the observed gas contents in many galaxies. Their model assumes an exponential mass distribution with disk radius. Most of the mass are in atomic gas state at the beginning of the evolution. Molecular clouds form through a modified Schmidt Law which takes into account gravitational instabilities in a possible three-phase structure of diffuse interstellar medium (McKee and Ostriker, 1977; Balbus and Cowie, 1985); whereas star formation proceeds presumably unaffected by the environmental conditions outside of molecular clouds (Young, 1987). In such a model both atomic and molecular gas profiles in a typical galactic disk (as a result of the evolution) can be fitted simultaneously by adjusting the efficiency constants. Galaxies of different sizes and masses, on the other hand, can be compared with the model by simply scaling their characteristic length scales and shifting their radial ranges to match the assumed disk total mass profile sigma tot(r).

Wang, Zhong↗
NASA NTRS1998

Cultivation of Tomato Tissues Capable of Forming Flowers and Fruits in Vitro

The final phase of this research project was designed to develop a practical method for producing a steady supply of fresh cherry tomato fruits over a period of several months, for possible use as a fresh vegetable supplement to a standard diet of astronauts on extended missions. This effort was successful. We were able to excise immature flowers from Pixie tomato plants grown in a controlled condition room, implant them on artificial media under aseptic conditions, and get them to develop into edible fruits in a little over a month. The medium (Murashige-Skoog) was purchased from Sigma, supplemented with sugar plus a synthetic analog of the plant hormone cytokinin, and adjusted to pH 5.8. A temperature of at least 25 C and visible light helped to produce ripe red fruits within 7 weeks. To ensure a steady supply of such tomatoes, we found it possible to store the explanted flower buds in MS medium at 5 C for at least 6 weeks without significant loss of ability to develop into fruits. This means that many containers could be prepared before launch and put into a refrigerator; a convenient number could then be removed periodically to guarantee a succession of harvests during the life of an extended mission. Details are found in the attached reprints. Subsequent applications for funds for flight or continued research were denied, and the project was terminated.

Galston, Arthur W.↗
NASA NTRS2011

Searches for Periodic Neutrino Emission from Binary Systems with 22 and 40 Strings of IceCube

Recent observations of GeV /TeV photon emission from several X-ray binaries have sparked a renewed interest in these objects as galactic particle accelerators. In spite of the available multi-wavelength data, their acceleration mechanisms are not determined, and the nature of the accelerated particles (hadrons or leptons) is unknown. While much evidence favors leptonic emission, it is very likely that a hadronic component is also accelerated in the jets of these binary systems. The observation of neutrino emission would be clear evidence for the presence of a hadronic component in the outflow of these sources. In this paper we look for periodic neutrino emission from binary systems. Such modulation, observed in the photon flux, would be caused by the geometry of these systems. The results of two searches are presented that differ in the treatment of the spectral shape and phase of the emission. The 'generic' search allows parameters to vary freely and best fit values, in a 'model-dependent' search, predictions are used to constrain these parameters. We use the IceCube data taken from May 31, 2007 to April 5, 2008 with its 22-string configuration, and from April 5, 2008 and May 20, 2009 with its 40-string configuration. For the generic search and the 40 string sample, we find that the most significant source in the catalog of 7 binary stars is Cygnus X-3 with a 1.8% probability after trials (2.10" sigma one-sided) of being produced by statistical fluctuations of the background. The model-dependent method tested a range of system geometries - the inclination and the massive star's disk size - for LS I+61 deg 303, no significant excess was found.

Abassi, R.↗
NASA NTRS2007

Osmium Isotope Systematics of Ureilites

The Os-187/Os-188 for twenty-two ureilite whole rock samples, including monomict, augite-bearing, and polymict lithologies, were examined in order to constrain the provenance and subsequent magmatic processing of the ureilite parent body (or bodies). The Re/Os ratios of most ureilites show evidence for a recent disturbance, probably related to Re mobility during weathering, and no meaningful chronological information can be extracted from the present data set. The ureilite Os-187/Os-188 ratios span a range from 0.11739 to 0.13018, with an average of 0.1258+/-0.0023 (1(sigma)), similar to typical carbonaceous chondrites, and distinct from ordinary or enstatite chondrites. The similar mean of Os-187/Os-188 measured for the ureilites and carbonaceous chondrites suggests that the ureilite parent body probably formed within the same region of the solar nebula as carbonaceous chondrites. From the narrow range of the 187Os/188Os distribution in ureilite meteorites it is further concluded that Re was not significantly fractionated from Os during planetary differentiation and was not lost along with the missing ureilitic melt component. The lack of large Re/Os fractionations requires that Re/Os partitioning was controlled by a metal phase, and thus metal had to be stable throughout the interval of magmatic processing on the ureilite parent body.

Rankenburg, K.↗
NASA NTRS1977

A technique for simulating turbulence for aerospace vehicle flight simulation studies

An atmospheric turbulence model which accommodates variability of turbulence properties along an aerospace vehicle trajectory was developed. The technique involves the use of Dryden spectral forms in which the defining parameters are the standard deviations (sigma) and integral scales (L) of turbulence. These spectra are expressed as nondimensional functions of the nondimensional frequency Omega = omega L/V where omega is dimensional radian frequency and V is the true air speed of the aerospace vehicle. The nondimensional spectra are factored by standard techniques to obtain nondimensional linear recursive filters in the time domain whereby band-limited white-like noise can be operated upon to obtain nondimensional longitudinal, lateral, and vertical turbulence velocities, as functions of nondimensional time, tV/L, where t is time. Application of the technique to the simulation of the space shuttle orbiter entry flight phase is discussed.

Fichtl, G. H.↗
NASA NTRS1991

Evaluation of GPS/UTC steering performance

The Global Positioning System (GPS) is required to maintain GPS time to Universal Coordinated Time (UTC) to an accuracy of one microsecond and broadcast to the user the offset between GPS and UTC to an accuracy of 100 nanoseconds (1 sigma). On 25 Jun. 1990, an automatic steering algorithm was implemented to control GPS time to synchronize it with UTC. The description of the steering laws and predicted performance results were presented at the 1989 Precise Time and Time Interval (PTTI) conference, while preliminary performance results were presented at the 1990 PTTI conference. The initial performance was not as predicted, resulting in an in-depth analysis of the observed performance and a more thorough sensitivity analysis. In addition, responses to anomalies were investigated. This paper will describe these analyses and results, and evaluate actual steering performance from Jun. 1990 to Nov. 1991. Although anomalies were observed during the initial phase of steering, recent experience is more in line with expectations.

W. A. Feess↗
NASA NTRS1981

Precise time and frequency intercomparison between NPL, India and PTB, Federal Republic of Germany via satellite symphonie-1

A time and frequency intercomparison experiment conducted using Earth stations in New Delhi, India and Raisting, FRG is described. The NPL clock was placed at New Delhi Earth Station and the Raisting Clock was calibrated with PTB/Primary standard via LORAN-C and travelling clocks. The random uncertainity of time comparisons, represented by two sample Allan Variance sigma (30 seconds), was less than 10 nanoseconds. The relative frequency difference between the NPL and Raisting Clocks, SNPL, RAIS, as measured over the 44 days period was found to be -15.7 x 10 to the -13th power. The relative frequency difference between PTB Primary Standard and Raisting Clock, SPTB, RAIS, during this period, was measured to be -22.8 x 10 to the -13th power. The relative frequency difference between NPL clock and PTB Primary Standard, SNPL, PTB, thus, is +7.1 x 10 to the -13th power. The clock rate (UTC, India) of +7.1 + or - 0.5 x 10 to the -13th power, agrees well with that obtained via VLF phase measurements over one year period and with USNO travelling clock time comparisons made in September, 1980.

Mathur, B. S.↗
NASA NTRS1988

The orbit of the Cepheid AW Per

An orbit for the classical Cepheid AW Per was derived. Phase residuals from the light curve are consistent with the light-time effect from the orbit. The companion was studied using IUE spectra. The flux distribution from 1300 to 1700 A is unusual, probably an extreme PbSi star, comparable to a B7V or B8V star. The flux of the composite spectrum from 1200 A through V is well matched by F7Ib and B8V standard stars with Delta M(sub upsilon) = 3(m) multiplied by 1. The mass function from the orbit indicates that the mass of the Cepheid must be greater that 4.7 solar mass if it is the more massive component. A B7V to B8V companion is compatible with the 1 sigma lower limit (3.5 solar mass) from the mass function. This implies that the Cepheid has the same mass, but the large magnitude difference rules this out. It is likely that the companion is itself a binary.

Evans, Nancy Remage↗
NASA NTRS2003

X-ray Emission from the Pre-planetary Nebula Henize 3-1475

We report the first detection of X-ray emission in a pre-planetary nebula, He 3-1475. Pre-planetary nebulae are rare objects in the short transition stage between the asymptotic giant branch (AGB) and planetary nebula evolutionary phases, and He 3-1475, characterized by a remarkable S-shaped chain of optical knots, is one of the most noteworthy members of this class. Observations with the Advanced CCD Imaging Spectrometer on board the Chandra X-Ray Observatory show the presence of compact emission coincident with the brightest optical knot in this bipolar object, which is displaced from the central star by 2'.7 along the polar axis. Model fits to the X-ray spectrum indicate an X-ray temperature and luminosity, respectively, of (4.3-5.7) x 10(exp 6) K and (4 +/- 1.4) x 10(exp 31) (D/5 kpc)(exp 2) ergs s(exp -1) respectively. Our 3 sigma upper limit on the luminosity of compact X-ray emission from the central star in He 3-1475 is approximately equal to 5 x 10(exp 31) (D/5 kpc)(exp 2) ergs s(exp -1). The detection of X-rays in He 3-1475 is consistent with models in which fast collimated post-AGB outflows are crucial to the shaping of nebulae; we discuss such models in the context of our observations.

circumstellar matter↗
NASA NTRS1993

Further ROSAT measurements of the period of 4U 1820-30

We have made two new observations of 4U 1820-30 with the ROSAT position sensitive proportional counter (PSPC). The measurements do not provide further evidence for a secular period decrease of this source. Instead, after inclusion of our new arrival time measurements the significance of the orbital period derivative drops (from 5.5 to 4.6 sigma), its best-fit value decreases (to P-dot/P =(-5.3 +/- 1.1) x 10(exp -8)/yr) and the formal probability that statistical fluctuations have caused the observed P-dot increases to 0.5% (from 0.003%). We detect light curve changes that are large enough to be the cause of some (or all) of the period changes seen in 4U 1820-30, but not large enough to explain the discrepancy of the observed period derivative with that theoretically predicted. We explore the possibility that the secular period change observed during 1976-1991 could have been dominated by random or systematic changes in the position and shape of an occulting bulge on the disk rim and conclude that phase shifts caused by this mechanism could in principle explain the discrepancy entirely.

Klis, M. Van Der↗
NASA NTRS2018

Total Ozone Trends from 1979 to 2016 Derived from Five Merged Observational Datasets - The Emergence into Ozone Recovery

We report on updated trends using different merged datasets from satellite and ground-based observations for the period from 1979 to 2016. Trends were determined by applying a multiple linear regression (MLR) to annual mean zonal mean data. Merged datasets used here include NASA MOD v8.6 and National Oceanic and Atmospheric Administration (NOAA) merge v8.6, both based on data from the series of Solar Backscatter UltraViolet (SBUV) and SBUV-2 satellite instruments (1978–present) as well as the Global Ozone Monitoring Experiment (GOME)-type Total Ozone (GTO) and GOME-SCIAMACHY-GOME-2 (GSG) merged datasets (1995-present), mainly comprising satellite data from GOME, the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY), and GOME-2A. The fifth dataset consists of the monthly mean zonal mean data from ground-based measurements collected at World Ozone and UV Data Center (WOUDC). The addition of four more years of data since the last World Meteorological Organization (WMO) ozone assessment (2013-2016) shows that for most datasets and regions the trends since the stratospheric halogen reached its maximum (approximately 1996 globally and approximately 2000 in polar regions) are mostly not significantly different from zero. However, for some latitudes, in particular the Southern Hemisphere extratropics and Northern Hemisphere subtropics, several datasets show small positive trends of slightly below +1 percent decade(exp. -1) that are barely statistically significant at the 2 Sigma uncertainty level. In the tropics, only two datasets show significant trends of +0.5 to +0.8 percent(exp.-1), while the others show near-zero trends. Positive trends since 2000 have been observed over Antarctica in September, but near-zero trends are found in October as well as in March over the Arctic. Uncertainties due to possible drifts between the datasets, from the merging procedure used to combine satellite datasets and related to the low sampling of ground-based data, are not accounted for in the trend analysis. Consequently, the retrieved trends can be only considered to be at the brink of becoming significant, but there are indications that we are about to emerge into the expected recovery phase. However, the recent trends are still considerably masked by the observed large year-to-year dynamical variability in total ozone.

column ozone trends↗
NASA NTRS2008

Mission and Navigation Design for the 2009 Mars Science Laboratory Mission

NASA s Mars Science Laboratory mission will launch the next mobile science laboratory to Mars in the fall of 2009 with arrival at Mars occurring in the summer of 2010. A heat shield, parachute, and rocket-powered descent stage, including a sky crane, will be used to land the rover safely on the surface of Mars. The direction of the atmospheric entry vehicle lift vector will be controlled by a hypersonic entry guidance algorithm to compensate for entry trajectory errors and counteract atmospheric and aerodynamic dispersions. The key challenges for mission design are (1) develop a launch/arrival strategy that provides communications coverage during the Entry, Descent, and Landing phase either from an X-band direct-to-Earth link or from a Ultra High Frequency link to the Mars Reconnaissance Orbiter for landing latitudes between 30 deg North and 30 deg South, while satisfying mission constraints on Earth departure energy and Mars atmospheric entry speed, and (2) generate Earth-departure targets for the Atlas V-541 launch vehicle for the specified launch/arrival strategy. The launch/arrival strategy employs a 30-day baseline launch period and a 27-day extended launch period with varying arrival dates at Mars. The key challenges for navigation design are (1) deliver the spacecraft to the atmospheric entry interface point (Mars radius of 3522.2 km) with an inertial entry flight path angle error of +/- 0.20 deg (3 sigma), (2) provide knowledge of the entry state vector accurate to +/- 2.8 km (3 sigma) in position and +/- 2.0 m/s (3 sigma) in velocity for initializing the entry guidance algorithm, and (3) ensure a 99% probability of successful delivery at Mars with respect to available cruise stage propellant. Orbit determination is accomplished via ground processing of multiple complimentary radiometric data types: Doppler, range, and Delta-Differential One-way Ranging (a Very Long Baseline Interferometry measurement). The navigation strategy makes use of up to five interplanetary trajectory correction maneuvers to achieve entry targeting requirements. The requirements for cruise propellant usage and atmospheric entry targeting and knowledge are met with ample margins.

Mission design↗
NASA NTRS1998

A Monte Carlo Uncertainty Analysis of Ozone Trend Predictions in a Two Dimensional Model

We use Monte Carlo analysis to estimate the uncertainty in predictions of total O3 trends between 1979 and 1995 made by the Goddard Space Flight Center (GSFC) two-dimensional (2D) model of stratospheric photochemistry and dynamics. The uncertainty is caused by gas-phase chemical reaction rates, photolysis coefficients, and heterogeneous reaction parameters which are model inputs. The uncertainty represents a lower bound to the total model uncertainty assuming the input parameter uncertainties are characterized correctly. Each of the Monte Carlo runs was initialized in 1970 and integrated for 26 model years through the end of 1995. This was repeated 419 times using input parameter sets generated by Latin Hypercube Sampling. The standard deviation (a) of the Monte Carlo ensemble of total 03 trend predictions is used to quantify the model uncertainty. The 34% difference between the model trend in globally and annually averaged total O3 using nominal inputs and atmospheric trends calculated from Nimbus 7 and Meteor 3 total ozone mapping spectrometer (TOMS) version 7 data is less than the 46% calculated 1 (sigma), model uncertainty, so there is no significant difference between the modeled and observed trends. In the northern hemisphere midlatitude spring the modeled and observed total 03 trends differ by more than 1(sigma) but less than 2(sigma), which we refer to as marginal significance. We perform a multiple linear regression analysis of the runs which suggests that only a few of the model reactions contribute significantly to the variance in the model predictions. The lack of significance in these comparisons suggests that they are of questionable use as guides for continuing model development. Large model/measurement differences which are many multiples of the input parameter uncertainty are seen in the meridional gradients of the trend and the peak-to-peak variations in the trends over an annual cycle. These discrepancies unambiguously indicate model formulation problems and provide a measure of model performance which can be used in attempts to improve such models.

Considine, D. B.↗
NASA NTRS1999

Pulse Profiles, Accretion Column Dips and a Flare in GX 1+4 During a Faint State

The Rossi X-ray Timing Explorer (RXTE) spacecraft observed the X-ray GX 1+4 for it period of 34 hours on July 19/20 1996. The source faded front an intensity of approximately 20 mcrab to a minimum of <= 0.7 mcrab and then partially recovered towards the end of the observation. This extended minimum lasted approximately 40,000 seconds. Phase folded light curves at a barycentric rotation period of 124.36568 +/- 0.00020 seconds show that near the center of the extended minimum the source stopped pulsing in the traditional sense but retained a weak dip feature at the rotation period. Away from the extended minimum the dips are progressively narrower at higher energies and may be interpreted as obscurations or eclipses of the hot spot by the accretion column. The pulse profile changed from leading-edge bright before the extended minimum to trailing-edge bright after it. Data from the Burst and Transient Source Experiment (BATSE) show that a torque reversal occurred < 10 days after our observation. Our data indicate that the observed rotation departs from a constant period with a P/P value of approximately -1.5% per year at a 4.5sigma significance. We infer that we may have serendipitously obtained data, with high sensitivity and temporal resolution about the time of an accretion disk spin reversal. We also observed a rapid flare which had some precursor activity close to the center of the extended minimum.

Giles, A. B.↗