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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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At least 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

A university team approach to regenerative concepts

An interdisciplinary team of university-affiliated scientists and engineers has undertaken the design of a controlled ecological life support system that employs physical, chemical, and biological components to supply and efficiently recycle food, atmospheric gases, water, and waste products. An Integrated Waste and Water Management System furnishes the basic capabilities for waste product preprocessing and for the establishment of baseline comparisons with proven physical and chemical systems. Attention is given to the relationships between food and oxygen supply and the mass fraction of algae in food, as well as to the potential for O2 production.

Nicks, Oran W.↗
NASA NTRS1988

Magnetically induced neutrino oscillations and neutrino refractive effects in the early universe

The interrelation between hypothetical neutrino magnetic dipole moments (MDMs) and primeval magnetic fields is discussed. The parameter range over which these possibilities are mutually exclusive is determined, taking into account for the first time neutrino refractive effects in the early universe. It is shown that an independent determination of either the neutrino MDMs or the primeval magnetic field strength would set powerful bounds on the other quantity.

Fukugita, Masataka↗
NASA NTRS1988

The universe at infrared wavelengths

This article discusses the status of infrared astronomy after the mission of the Infrared Astronomical Satellite (IRAS). Important scientific results from IRAS include: the origin of the interplanetary dust cloud, the formation of solar type stars, the energetics of the interstellar medium, the discovery of ultra-luminous infrared galaxies and their possible relation to the origin of quasars, and the large scale structure of the universe.

Beichman, C. A.↗
NASA NTRS1988

Light propagation in inhomogeneous universes

Refsdal's (1970) method is generalized to study the propagation of light rays through an inhomogeneous universe. The probability distribution for the linear component of the cumulative shear (CS) along light rays is derived, and it is shown that the CS can be dominated by nonlinear components, espcially for light rays in empty cones. The amplification tail of the amplification probability distribution is compared with analytic results; these linear investigations are shown to underestimate the high-amplification probability and hence the importance of the amplification bias in source counts. The distribution of the ellipticity of images of infinitesimal circular sources is derived, and it is shown that this can be dominated by the nonlinear contributions to the CS.

Schneider, Peter↗
NASA NTRS1988

Gravitational lensing in a cold dark matter universe

Gravitational lensing due to mass condensations in a biased cold dark matter (CDM) universe is investigated using the Press-Schechter (1974) theory with density fluctuation amplitudes taken from previous N-body work. Under the critical assumption that CDM haloes have small core radii, a distribution of image angular separations for high-z lensed quasars with a peak at about 1 arcsec and a half-width of a factor of about 10. Allowing for selection effects at small angular separations, this is in good agreement with the observed separations. The estimated frequency of lensing is somewhat lower than that observed, but the discrepancy can be removed by invoking amplification bias and by making a small upward adjustment to the density fluctuation amplitudes assumed in the CDM model.

Narayan, Ramesh↗
NASA NTRS1987

The detection of global convection on the sun by an analysis of line shift data of the John M. Wilcox Solar Observatory at Stanford University

Signatures of the existence of the global convection in the sun were found in the absorption line shift data of the John M. Wilcox Solar Observatory at Stanford University. The signatures are characterized by persistent periodic time variations in the east-west component of the velocity fields defined by fitting a slope to the line shift data in a certain longitude window at a specified latitude and longitude by a least square method. The variations indicate that the amplitude of the velocity fields is about 100 m/s. It is suggested that several modes of global convection are coexisting in the solar convection zone.

Yoshimura, Hirokazu↗
NASA NTRS1987

Universal computer control system (UCCS) for space telerobots

A universal computer control system (UCCS) is under development for all motor elements of a space telerobot. The basic hardware architecture and software design of UCCS are described, together with the rich motor sensing, control, and self-test capabilities of this all-computerized motor control system. UCCS is integrated into a multibus computer environment with direct interface to higher level control processors, uses pulsewidth multiplier power amplifiers, and one unit can control up to sixteen different motors simultaneously at a high I/O rate. UCCS performance capabilities are illustrated by a few data.

Bejczy, Antal K.↗
NASA NTRS1988

Probes of large-scale structure in the universe

A general formalism is developed which shows that the gravitational instability theory for the origin of the large-scale structure of the universe is now capable of critically confronting observational results on cosmic background radiation angular anisotropies, large-scale bulk motions, and large-scale clumpiness in the galaxy counts. The results indicate that presently advocated cosmological models will have considerable difficulty in simultaneously explaining the observational results.

Suto, Yasushi↗
NASA NTRS1988

Universality relationships in condensed matter - Bulk modulus and sound velocity

New forms for the bulk modulus and sound velocity of solids under compression, based on the universal equation of state of Vinet, Ferrante, Smith, and Rose (1987) are presented. These expressions are compared with a number of bulk modulus formulas previously utilized in high-pressure studies. It is demonstrated that this form yields a superior fit to experimental data to very high compressions, for a very wide range of solids. These solids cover the entire range of values of the pressure derivative of the bulk modulus which has been observed in high-pressure measurements.

Schlosser, Herbert↗
NASA NTRS1988

Large-scale structure from cosmic-string loops in a baryon-dominated universe

The results are presented of a numerical simulation of the formation of large-scale structure in a universe with Omega(0) = 0.2 and h = 0.5 dominated by baryons in which cosmic strings provide the initial density perturbations. The numerical model yields a power spectrum. Nonlinear evolution confirms that the model can account for 700 km/s bulk flows and a strong cluster-cluster correlation, but does rather poorly on smaller scales. There is no visual 'filamentary' structure, and the two-point correlation has too steep a logarithmic slope. The value of G mu = 4 x 10 to the -6th is significantly lower than previous estimates for the value of G mu in baryon-dominated cosmic string models.

Melott, Adrian L.↗
NASA NTRS1989

VLSI Universal Noiseless Coder

Proposed universal noiseless coder (UNC) compresses stream of data signals for efficient transmission in channel of limited bandwidth. Noiseless in sense original data completely recoverable from output code. System built as very-large-scale integrated (VLSI) circuit, compressing data in real time at input rates as high as 24 Mb/s, and possibly faster, depending on specific design. Approach yields small, lightweight system operating reliably and consuming little power. Constructed as single, compact, low-power VLSI circuit chip. Design of VLSI circuit chip made specific to code algorithms. Entire UNC fabricated in single chip, worst-case power dissipation less than 1 W.

Rice, Robert F.↗
NASA NTRS1988

The Purdue University Get Away Special II (PUGAS II)

The Purdue University Get Away Special Project (PUGAS) is a student-run organization dedicated to preparing payloads for flight on NASA's space shuttle. The first such payload (PUGAS I) flew on Challenger in 1983. The second payload (PUGAS II) should be ready by the end of 1988 and will include three experiments. The first experiment will involve the production of tin metal foam under microgravity conditions. The second experiment will focus on the desorption of water from carbon-epoxy composite materials. The third experiment will use a solid polymeric material to detect radiation in space.

Olenski, Christopher↗
NASA NTRS1988

University program

Information on university programs, program growth, and space research and technology strategy, are given in viewgraph form.

Hartman, Steven C.↗
NASA NTRS1988

Universal limiter for transient interpolation modeling of the advective transport equations: The ULTIMATE conservative difference scheme

A fresh approach is taken to the embarrassingly difficult problem of adequately modeling simple pure advection. An explicit conservative control-volume formation makes use of a universal limiter for transient interpolation modeling of the advective transport equations. This ULTIMATE conservative difference scheme is applied to unsteady, one-dimensional scalar pure advection at constant velocity, using three critical test profiles: an isolated sine-squared wave, a discontinuous step, and a semi-ellipse. The goal, of course, is to devise a single robust scheme which achieves sharp monotonic resolution of the step without corrupting the other profiles. The semi-ellipse is particularly challenging because of its combination of sudden and gradual changes in gradient. The ULTIMATE strategy can be applied to explicit conservation schemes of any order of accuracy. Second-order schemes are unsatisfactory, showing steepening and clipping typical of currently popular so-called high resolution shock-capturing of TVD schemes. The ULTIMATE third-order upwind scheme is highly satisfactory for most flows of practical importance. Higher order methods give predictably better step resolution, although even-order schemes generate a (monotonic) waviness in the difficult semi-ellipse simulation. Little is to be gained above ULTIMATE fifth-order upwinding which gives results close to the ultimate for which one might hope.

Leonard, B. P.↗
NASA NTRS1989

Universal test fixture for monolithic mm-wave integrated circuits calibrated with an augmented TRD algorithm

The design and evaluation of a novel fixturing technique for characterizing millimeter wave solid state devices is presented. The technique utilizes a cosine-tapered ridge guide fixture and a one-tier de-embedding procedure to produce accurate and repeatable device level data. Advanced features of this technique include nondestructive testing, full waveguide bandwidth operation, universality of application, and rapid, yet repeatable, chip-level characterization. In addition, only one set of calibration standards is required regardless of the device geometry.

Romanofsky, Robert R.↗
NASA NTRS1988

Agenda of the Fourth Annual Summer Conference, NASA/USRA University Advanced Design Program

Presentations given by the participants at the fourth annual summer conference of the NASA/USRA University Advanced Design Program are summarized. The study topics include potential space and aeronautics projects which could be undertaken during a 20 to 30 year period beginning with the Space Station Initial Operating Configuration (IOC) scheduled for the early to mid-1990's. This includes system design studies for both manned and unmanned endeavors; e.g., lunar launch and landing facilities and operations, variable artificial gravity facility for the Space Station, manned Mars aircraft and delivery system, long term space habitat, construction equipment for lunar bases, Mars oxygen production system, trans-Pacific high speed civil transport, V/STOL aircraft concepts, etc.

Source record↗
NASA NTRS1987

A universal six-joint robot controller

A general purpose six-axis robotic manipulator controller was designed and implemented to serve as a research tool for the investigation of the practical and theoretical aspects of various control strategies in robotics. A 80286-based Intel System 310 running the Xenix operating servo software as well as the higher level software (e.g., kinematics and path planning) were employed. A Multibus compatible interface board was designed and constructed to handle I/O signals from the robot manipulator's joint motors. From the design point of view, the universal controller is capable of driving robot manipulators equipped with D.C. joint motors and position optical encoders. To test its functionality, the controller is connected to the joint motor D.C. power amplifier of a PUMA 560 arm bypassing completely the manufacturer-supplied Unimation controller. A controller algorithm consisting of local PD control laws was written and installed into the Xenix operating system. Additional software drivers were implemented to allow application programs access to the interface board. All software was written in the C language.

Bihn, D. G.↗
NASA NTRS1988

Supercomputer chemistry at the University of Minnesota

The focus of cluster chemistry studies at the University of Minnesota is on the adsorption of small hydrocarbon molecules on metal and graphite surfaces, and on the substitution defects in diamond and silicon. Of particular interest is the study of very large systems such as the C60 molecule and the C150H30 molecule. Many of the properties of such clusters converge extremely slowly toward bulk values. Ultrathin films and microporous media are discussed as well as the Brownian dynamics of polymers.

Almlof, Jan↗