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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

The dynamical evolution of the Saturnian ring spokes

It is suggested that the radial spokes observed in rotation across Saturn's B ring are composed of fine, charged dust levitated off the surfaces of larger bodies by electrostatic forces when the latter are sporadically charged to high electrostatic potentials. The time evolution of a spoke is likened to the continuous unfolding of a fan whose vertex is at the synchronous orbit, and whose corotating edge is fixed in the radial direction. According to the present model, the angular velocity of the fan leading edge depends on the age of the spoke, and it is anticipated that the observed scatter of the measured velocities about the Kepler value is real, rather than due to measurement errors, despite their presence inside the expected error bars. It is also shown that the resettling of the grains of dust on the larger bodies in the ring plane, following their initial levitation, results in a differential transport of grains across the ring plane, establishing different multimodal size distributions of dust within the spokes at different planetocentric distances.

Hill, J. R.↗
NASA NTRS1982

On the geometric nature of high energy nucleus-nucleus reaction cross sections

Within the context of a high energy double-folding optical potential approximation to the exact nucleus-nucleus multiple-scattering series, eikonal scattering theory is used to investigate the validity of geometric reaction cross sections in relativistic heavy ion collisions. The potential used includes a finite range interaction and nuclear single-particle densities extracted from nuclear charge distributions by unfolding the finite proton charge distribution. Pauli correlation effects are also included in an approximate way. The sensitivity of the predictions to the assumed interaction, Pauli correlation approximation, and nuclear density distributions is investigated. These results are in agreement with early predictions concerning the geometric nature of relativistic heavy ion collisions and in disagreement with a recent analysis, utilizing the zero range approximation, which suggested otherwise. Reasons for the lack of agreement between the analyses are also presented. Finally, approximate applicability limits for geometric reaction cross sections are determined.

Townsend, L. W.↗
NASA NTRS1982

Studies of neutron and proton nuclear activation in low-Earth orbit

The expected induced radioactivity of experimental material in low Earth orbit was studied for characteristics of activating particles such as cosmic rays, high energy Earth albedo neutrons, trapped protons, and secondary protons and neutrons. The activation cross sections for the production of long lived radioisotopes and other existing nuclear data appropriate to the study of these reactions were compiled. Computer codes which are required to calculate the expected activation of orbited materials were developed. The decreased computer code used to predict the activation of trapped protons of materials placed in the expected orbits of LDEF and Spacelab II. Techniques for unfolding the fluxes of activating particles from the measured activation of orbited materials are examined.

Laird, C. E.↗
NASA NTRS1983

An overview of computer-based natural language processing

Computer based Natural Language Processing (NLP) is the key to enabling humans and their computer based creations to interact with machines in natural language (like English, Japanese, German, etc., in contrast to formal computer languages). The doors that such an achievement can open have made this a major research area in Artificial Intelligence and Computational Linguistics. Commercial natural language interfaces to computers have recently entered the market and future looks bright for other applications as well. This report reviews the basic approaches to such systems, the techniques utilized, applications, the state of the art of the technology, issues and research requirements, the major participants and finally, future trends and expectations. It is anticipated that this report will prove useful to engineering and research managers, potential users, and others who will be affected by this field as it unfolds.

Gevarter, W. B.↗
NASA NTRS1983

An overview of artificial intelligence and robotics. Volume 1: Artificial intelligence. Part A: The core ingredients

Artificial Intelligence (AI) is an emerging technology that has recently attracted considerable attention. Many applications are now under development. The goal of Artificial Intelligence is focused on developing computational approaches to intelligent behavior. This goal is so broad - covering virtually all aspects of human cognitive activity - that substantial confusion has arisen as to the actual nature of AI, its current status and its future capability. This volume, the first in a series of NBS/NASA reports on the subject, attempts to address these concerns. Thus, this report endeavors to clarify what AI is, the foundations on which it rests, the techniques utilized, applications, the participants and, finally, AI's state-of-the-art and future trends. It is anticipated that this report will prove useful to government and private engineering and research managers, potential users, and others who will be affected by this field as it unfolds.

Gevarter, W. B.↗
NASA NTRS1983

Eikonal phase shift analyses of carbon-carbon scattering

A high-energy double-folding optical potential approximation to the exact nucleus-nucleus multiple-scattering series is used in determining eikonal phase shifts for carbon-carbon scattering at 204.2, 242.7, and 288.6 MeV. The double-folding potentials are derived by folding the energy-dependent free nucleon-nucleon interaction with densities for the projectile and target; these latter are obtained by unfolding the finite nucleon charge density from harmonic-well carbon charge distributions. The charge parameters for these distributions are taken from the results of electron scattering experiments. Predictions are made for total, reaction, and elastic differential cross sections using standard partial wave analysis for the scattering of identical particles and are then compared with recent experimental results. Excellent agreement is obtained despite the absence of arbitrarily adjusted parameters in the theory.

Townsend, L. W.↗
NASA NTRS1985

Compact Antispin Parachute System

Costs and complexity of parachute system greatly reduced. Rigidtowline parachute system operates in three steps: (1) When aircraft begins to spin, parachute compartment opened up, and parachute unfolds; (2) Parachute deployed and spin terminated; and (3) Parachute released. Advantage of towline system allows use of much smaller parachute, reducing design loads on structural reinforcement. Also, complex pyrotechnic-deployment or jettison systems no longer necessary.

Whipple, R. D.↗
NASA NTRS1984

Rendezvous and docking with remote piloted vehicles

The man-in-the-loop control system requirements for the Orbital Maneuvering Vehicle (OMV) are examined. Since many similarities exist between the Teleoperator Retrieval System (TRS) and the unfolding OMV concept, a review of the TRS control system baseline along with selected design trades which led to that baseline are discussed. TRS program issues relevant to the man-in-the-loop control system design include thruster size, communication delays and TV bandwidth compression, range/range rate radar, tumbling targets, shimmed docking interface, and control system definition. A TRS vs. OMV simulation comparative study is summarized, and the major issues currently facing the control system designer on OMV are discussed.

Micheal, J. D.↗
NASA NTRS1985

Hinged-Blade, Vertical-Shaft Windmill

Vertical-shaft windmill concept calls for hinged, flapping blades to increase energy-conversion efficiency by reducing wind-energy loss. Hinged Blade Halves unfold to catch wind when moving with it, then fold away from wind when moving against it.

Shultz, B., Jr.↗
NASA NTRS1985

Radial distribution of cosmic ray intensity in the galaxy from gamma-ray data

The radial distributions of Galactic gamma-ray emissivity and cosmic ray intensity are derived by unfolding the SAS2 line flux data. The results show a marked gradient, with the cosmic ray intensity in the region 3,R,7 kpc being 3 to 4 times as much as locally. There is also an indication for a higher gradient for cosmic rays of lower energy.

Goned, A.↗
NASA NTRS1985

s-wave threshold in electron attachment - Observations and cross sections in CCl4 and SF6 at ultralow electron energies

The threshold photoionization method was used to study low-energy electron attachment phenomena in and cross sections of CCl4 and SF6 compounds, which have applications in the design of gaseous dielectrics and diffuse discharge opening switches. Measurements were made at electron energies from below threshold to 140 meV at resolutions of 6 and 8 meV. A narrow resolution-limited structure was observed in electron attachment to CCl4 and SF6 at electron energies below 10 meV, which is attributed to the divergence of the attachment cross section in the limit epsilon, l approaches zero. The results are compared with experimental collisional-ionization results, electron-swarm unfolded cross sections, and earlier threshold photoionization data.

Chutjian, A.↗
NASA NTRS1986

Void-Free Lid for Food Packaging

Flexible cover eliminates air pockets in sealed container. Universal food-package lid formed from flexible plastic. Partially folded, lid unfolded by depressing center portion. Height of flat portion of lid above flange thereby reduced. Pressure of food against central oval depression pops it out, forming dome that provides finger grip for mixing contents with water or opening lid. Therefore food stays fresh, allows compact stacking of partially filled containers, and resists crushing. Originally developed for packaging dehydrated food for use in human consumption on Space Shuttle missions. Other uses include home canning and commercial food packaging.

Watson, C. D.↗
NASA NTRS1985

Study of statis and dynamic stress effects in nonlinear solids

As the basic physical principles behind the low-field magnetoacoustic interactions have been unfolded, a new step in the present research had to be taken. First, the stress measurements began in samples obtained in real railroad wheel and rail materials. Second, the effect of texture, which is the prime obstacle of conventional NDE techniques, has been investigated. The first stage shows experimental results on these subjects again confirmed that the present technique is most suited for nondestructive stress characterization in steel components. The stress effects on the magnetoacoustic interaction obtained in a sample made from railroad rail which were very similar to those obtained previously in 1045 steel. These results being somewhat different from the results with low (1020) and high (1095) carbon steels, there seemed to be certain range of medium carbon steels having the same characteristics. Also, as expected from the model, the stress information obtained by this technique has been confirmed to be least affected by the presence of texture.

Namkung, M.↗
NASA NTRS1986

Time and space integrating acousto-optic folded spectrum processing for SETI

Time and space integrating folded spectrum techniques utilizing acousto-optic devices (AOD) as 1-D input transducers are investigated for a potential application as wideband, high resolution, large processing gain spectrum analyzers in the search for extra-terrestrial intelligence (SETI) program. The space integrating Fourier transform performed by a lens channels the coarse spectral components diffracted from an AOD onto an array of time integrating narrowband fine resolution spectrum analyzers. The pulsing action of a laser diode samples the interferometrically detected output, aliasing the fine resolution components to baseband, as required for the subsequent charge coupled devices (CCD) processing. The raster scan mechanism incorporated into the readout of the CCD detector array is used to unfold the 2-D transform, reproducing the desired high resolution Fourier transform of the input signal.

Wagner, K.↗
NASA NTRS1987

Backlash-Free Locking Hinge

Tight joints achieved without precisely machined parts. Hinge for foldable structures locked with minimum force by human operator. Once locked, hinge makes strong, tight joint. Loose fit, or joint slop, common to commercial locking hinges eliminated. Despite tight fit, new hinge concept does not impose close tolerances on manufacture of its parts. Developed for erecting unfoldable structures in space, hinge used on collapsible scaffolds and similar terrestrial structures.

Wessekski, Clarence J.↗
NASA NTRS1986

Development of Deployable Truss Concept for Space Station

A single-fold, automatically deployable and retractable, square-shaped truss concept that is a candidate for the strongback of NASA's Space Station was developed. Compact stowage within a square-shaped housing is achieved by using folded longerons and telescoping diagonal members. Deployment or retraction is accomplished, bay by bay, in a controlled manner with root strength maintained at all times. Control is accomplished by motor-driven jack-screws operated by a controller. Power, data, and fluid utility lines can be integrated onto trays that unfold with the truss. To verify performance a kinematically representative ground test article version is used.

Greenberg, H. S.↗
NASA NTRS1987

Origin and propagation of galactic cosmic rays

The study of systematic trends in elemental abundances is important for unfolding the nuclear and/or atomic effects that should govern the shaping of source abundances and in constraining the parameters of cosmic ray acceleration models. In principle, much can be learned about the large-scale distributions of cosmic rays in the galaxy from all-sky gamma ray surveys such as COS-B and SAS-2. Because of the uncertainties in the matter distribution which come from the inability to measure the abundance of molecular hydrogen, the results are somewhat controversial. The leaky-box model accounts for a surprising amount of the data on heavy nuclei. However, a growing body of data indicates that the simple picture may have to be abandoned in favor of more complex models which contain additional parameters. Future experiments on the Spacelab and space station will hopefully be made of the spectra of individual nuclei at high energy. Antiprotons must be studied in the background free environment above the atmosphere with much higher reliability and presion to obtain spectral information.

Cesarsky, Catherine J.↗
NASA NTRS1988

Cavity door effects on aerodynamic loadings of compressed-carriage store configurations separating from cavities at supersonic speeds

An experimental wind-tunnel investigation has been conducted at supersonic Mach numbers to determine the effects of cavity doors on the aerodynamic characteristics of compressed-carriage store configurations during separation from a shallow box cavity (closed cavity flow) located in a simulated generic parent aircraft. The tests were conducted in the Langley Unitary Plan Wind Tunnel at free-stream Mach numbers of 1.70, 2.00, and 2.65 for a constant Reynolds number per foot of two million. Results are summarized to show the effects of cavity door opening angles, vertical door height, folded and unfolded tail fins, and Mach number on the near-field aerodynamic separation characteristics of a single missile-type store with in-line cruciform wings and tail fins.

Blair, A. B., Jr.↗