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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 109 records · Page 6
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NASA NTRS1989

Results of dynamic testing of GP-B spherical gyroscopes

Laboratory tests of the spherical electrostatically levitated cryogenically cooled coated gyroscope being developed for the Gravity Probe B (GP-B) spacecraft (Bardas et al., 1986) are reported. Spin speed and the dc components of the trapped magnetic field are measured with three orthogonal pickup loops attached to SQUID detectors as the levitated gyro is brought up to speed by an He gas jet. Data on the spin-vector time history, mass unbalance, higher rotor-shape harmonics, and spin-vector position are presented in extensive graphs and characterized in detail, and a mathematical model of the electrostatic suspension torques is derived. Prototype gyro 86-4 is found to have mass unbalance within the range required for the GP-B mission (to detect the geodetic and motional effects predicted by general relativity theory).

Keiser, G. M.↗
NASA NTRS1989

Hypersonic nozzle design

Possible experimental facilities appropriate to a university environment that could make meaningful contributions to the solution of problems in hypersonic aerodynamics are investigated. Needs for the National Aerospace Plane and interplanetary flights with atmospheric aerobraking are used to scope the problem. Relevant events of the past two decades in universities and at the national laboratories are examined for their implications regarding both problems and prospects. Most striking is the emergence of computational fluid dynamics, which is viewed here as an equal partner with laboratory experimentation and flight test in relating theory with reality. Also significant are major advances in instrumentation and data processing methods, especially optical techniques. The direction of the study was guided by the concept of a companion program, i.e., the university effort should complement a major area of endeavor at NASA-Langley. Through this, both faculty and student participants gain a natural and effective working relationship. Existing and proposed major hypersonic aerodynamic facilities in industry and at the national laboratories are examined by type; hypersonic wind tunnels, arc-heated tunnels, shock tubes and tunnels, and ballistic ranges. Of these, the free piston tunnel and shock tube/tunnel are most appropriate for a university.

Griffith, Wayland C.↗
NASA NTRS1989

Report of the International Ozone Trends Panel 1988, volume 2

Chapters on the following topics are presented: trends in stratospheric temperature; theory and observations- model simulations of the period 1955-1985; trends in source gases; trends in stratospheric minor constituents; trends in aerosol abundances and distribution; and observations and theories related to antarctic ozone.

Source record↗
NASA NTRS1992

From Mars to Greenland: Charting gravity with space and airborne instruments - Fields, tides, methods, results

This symposium on space and airborne techniques for measuring gravity fields, and related theory, contains papers on gravity modeling of Mars and Venus at NASA/GSFC, an integrated laser Doppler method for measuring planetary gravity fields, observed temporal variations in the earth's gravity field from 16-year Starlette orbit analysis, high-resolution gravity models combining terrestrial and satellite data, the effect of water vapor corrections for satellite altimeter measurements of the geoid, and laboratory demonstrations of superconducting gravity and inertial sensors for space and airborne gravity measurements. Other papers are on airborne gravity measurements over the Kelvin Seamount; the accuracy of GPS-derived acceleration from moving platform tests; airborne gravimetry, altimetry, and GPS navigation errors; controlling common mode stabilization errors in airborne gravity gradiometry, GPS/INS gravity measurements in space and on a balloon, and Walsh-Fourier series expansion of the earth's gravitational potential.

Colombo, Oscar L.↗
NASA NTRS1949

General Theory of Aerodynamic Instability and the Mechanism of Flutter

The aerodynamic forces on an oscillating airfoil or airfoil-aileron combination of three independent degrees of freedom have been determined. The problem resolves itself into the solution of certain definite integrals, which have been identified as Bessel functions of the first and second kind and of zero and first order. The theory, being based on potential flow and the Kutta condition, is fundamentally equivalent to the conventional wing-section theory relating to the steady case. The air forces being known, the mechanism of aerodynamic instability has been analyzed in detail. An exact solution, involving potential flow and the adoption of the Kutta condition, has been analyzed in detail. An exact solution, involving potential flow and the adoption of the Kutta condition, has been arrived at. The solution is of a simple form and is expressed by means of an auxiliary parameter K.

Theodorsen, Theodore↗
NASA NTRS1994

Mechanical Properties of Shock-Damaged Rocks

Stress-strain tests were performed both on shock-damaged gabbro and limestone. The effective Young's modulus decreases with increasing initial damage parameter value, and an apparent work-softening process occurs prior to failure. To further characterize shock-induced microcracks, the longitudinal elastic wave velocity behavior of shock-damaged gabbro in the direction of compression up to failure was measured using an acoustic transmission technique under uniaxial loading. A dramatic increase in velocity was observed for the static compressive stress range of 0-50 MPa. Above that stress range, the velocity behavior of lightly damaged (D(sub 0) less than 0.1) gabbro is almost equal to unshocked gabbro. The failure strength of heavily-damaged (D(sub 0) greater than 0.1) gabbro is approx. 100-150 MPa, much lower than that of lightly damaged and unshocked gabbros (approx. 230-260 MPa). Following Nur's theory, the crack shape distribution was analyzed. The shock-induced cracks in gabbro appear to be largely thin penny-shaped cracks with c/a values below 5 x 10(exp -4). Moreover, the applicability of Ashby and Sammis's theory relating failure strength and damage parameter of shock-damaged rocks was examined and was found to yield a good estimate of the relation of shock-induced deficit in elastic modulus with the deficit in compressive strength.

He, Hongliang↗
NASA NTRS1998

Exploring the Structure and Evolution of the Universe: Multi-Band Profiles of the Known Gamma-Ray Pulsars

As summarized in this pamphlet, some of the far-reaching underlying issues to be addressed include: What is the origin of the universe and its destiny; Why is the universe lumpy; How did the known structures of the universe evolve; How do galaxies evolve; How do massive black holes grow; How did the elemental composition of the universe evolve; What is the structure and behavior of matter in the extreme; and Is Einstein's general relativity theory right.

UNIVERSE↗
NASA NTRS1998

The Moon's Molten Core and Tidal Q

The rotation of the Moon is influenced by solid-body tides and interaction at a liquid-core/solid-mantle boundary. The Lunar Laser Ranging (LLR) data are sensitive to variations in lunar rotation. Analysis of those ranges reveals four dissipation periodicities in the rotation. These signatures can be explained with the combined effects of tide plus core, but not with either alone. The fluid core detection exceeds three times its uncertainty. The inferred core radius has a 1 -sigma upper limit of 352 km for iron and up to 374 km if sulfur is present. The tidal dissipation is strong, Q at one month is 37 +/- 5 .Q increases for longer periods and is 60 (-15, +40) at one year.Dynamical evidence for a fluid lunar core has previously been presented. These-earlier solutions included three dissipation parameters. New solutions benefit from additional LLR data and an improved gravity field from Doppler tracking of Lunar Prospector. Five dissipation parameters are now solved for. There are several options for dissipation parameters: a core coupling parameter, a time delay for tidal distortion of the moments of inertia, and five periodic terms in the rotation angles. Solutions with different combinations of these are compatible (a theory relates K/C and time delay to a series of periodic terms). The solutions used K/C, time delay, and one periodic term. When dissipation signatures at five rotation frequencies are solved for, four amplitudes (4 to 263 milliarcseconds) are detected above the noise. Attempts to explain these results using either tides alone or core alone fail (less than 3(sigma) discrepancy for the former and 9(sigma), for the latter). A combination of tides and liquid core matches the results well.

Williams, J. G.↗
NASA NTRS2003

New Experiments with Spinning Metallic Discs

A number of recent advanced theories related to torsion properties of the space-time matrix predict the existence of an interaction between classically spinning objects. Indeed, some experimental data suggest that spinning magnetic bodies discernibly interact with Earth's natural fields. If there are interactions between rotating bodies then nuclear spins could be used for detection. Thus, assuming a spinning body induces a hypothetical torsion field, a sensor based on the giant magnetoresistance effect would detect local changes. Experimentally, spinning a brass wheel shielded from Earth's magnetic field showed no measurable change in signals; with no shielding a Faraday disc phenomenon was observed. Unexpected experimental measurements from the non-axial Faraday disc configuration were recorded and a theoretical model was derived to explain them.

Mazuruk, Konstantin↗
NASA NTRS2005

Self-dissimilarity as a High Dimensional Complexity Measure

For many systems characterized as "complex" the patterns exhibited on different scales differ markedly from one another. For example the biomass distribution in a human body "looks very different" depending on the scale at which one examines it. Conversely, the patterns at different scales in "simple" systems (e.g., gases, mountains, crystals) vary little from one scale to another. Accordingly, the degrees of self-dissimilarity between the patterns of a system at various scales constitute a complexity "signature" of that system. Here we present a novel quantification of self-dissimilarity. This signature can, if desired, incorporate a novel information-theoretic measure of the distance between probability distributions that we derive here. Whatever distance measure is chosen, our quantification of self-dissimilarity can be measured for many kinds of real-world data. This allows comparisons of the complexity signatures of wholly different kinds of systems (e.g., systems involving information density in a digital computer vs. species densities in a rain-forest vs. capital density in an economy, etc.). Moreover, in contrast to many other suggested complexity measures, evaluating the self-dissimilarity of a system does not require one to already have a model of the system. These facts may allow self-dissimilarity signatures to be used a s the underlying observational variables of an eventual overarching theory relating all complex systems. To illustrate self-dissimilarity we present several numerical experiments. In particular, we show that underlying structure of the logistic map is picked out by the self-dissimilarity signature of time series produced by that map

Wolpert, David H.↗
NASA NTRS2003

Proceedings of the 2003 NASA/JPL Workshop on Fundamental Physics in Space

The 2003 Fundamental Physics workshop included presentations ranging from forces acting on RNA to properties of clouds of degenerate Fermi atoms, to techniques to probe for a added space-time dimensions, and to flight hardware for low temperature experiments, amongst others. Mark Lee from NASA Headquarters described the new strategic plan that NASA has developed under Administrator Sean O'Keefe's leadership. Mark explained that the Fundamental Physics community now needs to align its research program and the roadmap describing the long-term goals of the program with the NASA plan. Ulf Israelsson of JPL discussed how the rewrite of the roadmap will be implemented under the leadership of the Fundamental Physics Discipline Working Group (DWG). Nick Bigelow, chair of the DWG, outlined how investigators can contribute to the writing of the roadmap. Results of measurements on very cold clouds of Fermi atoms near a Feshbach resonance were described by three investigators. Also, new measurements relating to tests of Einstein equivalence were discussed. Investigators also described methods to test other aspects of Einstein's relativity theories.

Strayer, Don↗
NASA NTRS2005

Proceedings of the 2004 NASA/ONR Circulation Control Workshop, Part 2

This conference proceeding is comprised of papers that were presented at the NASA/ONR Circulation Control Workshop held 16-17 March 2004 at the Radisson-Hampton in Hampton, VA. Over two full days, 30 papers and 4 posters were presented with 110 scientists and engineers in attendance, representing 3 countries. As technological advances influence the efficiency and effectiveness of aerodynamic and hydrodynamic applications, designs, and operations, this workshop was intended to address the technologies, systems, challenges and successes specific to Coanda driven circulation control in aerodynamics and hydrodynamics. A major goal of this workshop was to determine the state-of-the-art in circulation control and to assess the future directions and applications for circulation control. The 2004 workshop addressed applications, experiments, computations, and theories related to circulation control, emphasizing fundamental physics, systems analysis, and applied research. The workshop consisted of single session oral presentations, posters, and written papers that are documented in this unclassified conference proceeding. The format of this written proceeding follows the agenda of the workshop. Each paper is followed with the presentation given at the workshop. the editors compiled brief summaries for each effort that is at the end of this proceeding. These summaries include the paper, oral presentation, and questions or comments that occurred during the workshop. The 2004 Circulation Control Workshop focused on applications including Naval vehicles (Surface and Underwater vehicles), Fixed Wing Aviation (general aviation, commercial, cargo, and business aircraft); V/STOL platforms (helicopters, military aircraft, tilt rotors); propulsion systems (propellers, jet engines, gas turbines), and ground vehicles (automotive, trucks, and other); wind turbines, and other nontraditional applications (e.g., vacuum cleaner, ceiling fan). As part of the CFD focus area of the 2004 CC Workshop, CFD practitioners were invited to compute a two-dimensional benchmark problem for which geometry, flow conditions, grids, and experimental data were available before the workshop. The purpose was to accumulate a database of simulations for a single problem using a range of CFD codes, turbulence models, and grid strategies so as to expand knowledge of model performance/requirements and guide simulation of practical CC configurations.

Jones, Gregory S.↗
NASA NTRS2014

Drag Reduction Through Distributed Electric Propulsion

One promising application of recent advances in electric aircraft propulsion technologies is a blown wing realized through the placement of a number of electric motors driving individual tractor propellers spaced along each wing. This configuration increases the maximum lift coefficient by providing substantially increased dynamic pressure across the wing at low speeds. This allows for a wing sized near the ideal area for maximum range at cruise conditions, imparting the cruise drag and ride quality benefits of this smaller wing size without decreasing takeoff and landing performance. A reference four-seat general aviation aircraft was chosen as an exemplary application case. Idealized momentum theory relations were derived to investigate tradeoffs in various design variables. Navier-Stokes aeropropulsive simulations were performed with various wing and propeller configurations at takeoff and landing conditions to provide insight into the effect of different wing and propeller designs on the realizable effective maximum lift coefficient. Similar analyses were performed at the cruise condition to ensure that drag targets are attainable. Results indicate that this configuration shows great promise to drastically improve the efficiency of small aircraft.

Stoll, Alex M.↗
NASA NTRS1982

Matter in general relativity

Two theories of matter in general relativity, the fluid theory and the kinetic theory, were studied. Results include: (1) a discussion of various methods of completing the fluid equations; (2) a method of constructing charged general relativistic solutions in kinetic theory; and (3) a proof and discussion of the incompatibility of perfect fluid solutions in anisotropic cosmologies. Interpretations of NASA gravitational experiments using the above mentioned results were started. Two papers were prepared for publications based on this work.

Ray, J. R.↗
NASA NTRS1988

A modified Lorentz theory as a test theory of special relativity

Attention has been given recently to a modified Lorentz theory (MLT) that is based on the generalized Galilean transformation. Some explicit formulas within the framework of MLT, dealing with the one-way velocity of light, slow-clock transport, and the Doppler effect are derived. A number of typical experiments are analyzed on this basis. Results indicate that the empirical equivalence between MLT and special relativity is still maintained to second order terms. The results of previous works that predict that the MLT might be distinguished from special relativity at the third order by Doppler centrifuge tests capable of a fractional frequency detection threshold of 10 to the -15th are confirmed.

Chang, T.↗
NASA NTRS1982

Solar particle propagation and modulation theory

Developments related to solar flare particle propagation theory are considered, taking into account the transport equation currently employed to describe the propagation of solar flare particles. This equation does not take into consideration convection with the solar wind, drifts, and changes in particle energy. The equation was solved numerically to generate typical solar flare particle time profiles at 1 AU. The results, however, were not satisfactory. It was found that the numerical method used was apparently in error. New advances which provide approximate analytical solutions to the equation are reported. Questions of galactic cosmic ray propagation in interplanetary space are also discussed.

Lee, M. A.↗