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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 217 records · Page 12

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NASA NTRS1990

Experiment K-6-02. Biomedical, biochemical and morphological alterations of muscle and dense, fibrous connective tissues during 14 days of spaceflight

Findings on the connective tissue response to short-term space flight (12 days) are discussed. Specifically, data regarding the biochemical, biomechanical and morphological characteristics of selected connective tissues (humerus, vertebral body, tendon and skeletal muscle) of growing rats is given. Results are given concerning the humerus cortical bone, the vertebral bone, nutritional effects on bone biomechanical properties, and soft tense fiber connective tissue response.

Vailas, A.↗

NASA NTRS1997

Effects of Weightlessness on Vestibular Development of Quail

The lack of gravity is known to alter vestibular responses in developing and adult vertebrates. One cause of these altered responses may be changes in the connections between the vestibular receptor and the brain. Therefore we propose to investigate the effects of gravity on the formations of connections between the gravity receptors of the ear and the brain in developing quail incubated in space beginning at an age before these connections are established (incubation day three) until near the time of hatching, when they are to some extent functional. This investigation will make use of a novel technique, the diffusion of a lipophilic dye, DiI, in fixed tissue. This technique can thus be used to analyze the connections in specimens fixed in orbit, thus eliminating changes due to the earth's gravity. The evaluation of the data will enable us to detect gross deviations from normal patterns as well as detailed quantitative deviations.

Fritzsch, Bernd↗

NASA NTRS1975

Observations of low-energy electrons upstream of the earth's bow shock

Observations of electron fluxes with a lunar-based electron spectrometer when the moon was upstream of the earth have shown that a subset of observed fluxes are strongly controlled by the interplanetary magnetic field (IMF) direction. The fluxes occur only when the IMF lines connect back to the earth's bow shock. Observed densities and temperatures were in the ranges 0.002 to 0.004 per cu cm and 1,700,000 to 2,800,000 K. It is shown that these electrons can account for increases in effective solar wind electron temperatures on bow shock connected field lines, which have been observed previously by other investigators. It is further shown that if a model of the bow shock with an electrostatic potential barrier is assumed, the potential can be estimated to be 500 V.

Reasoner, D. L.↗

NASA NTRS1973

Fundamental Consideration of Noise radiation by rotary wings

An historical review of progress in understanding of rotor noise is presented. Initial work was principally on propellers, but has many obvious applications to noise from rotary wings. Current understanding of rotor noise radiation is then reviewed in some detail. The principal noise sources appear to be: (1) discrete frequency due to distorted inflow; (2) low frequency broadband due to turbulent inflow, and (3) high frequency broadband due to tip effects. On a helicopter rotor each of these sources seems to be intimately connected with the shed vortex wakes. Tip modifications offer one method for controlling the effects. The implications for the designer are discussed. Rotor subjective noise levels appear to obey a velocity to the eighth power law, independent of thrust. Experiments to rectify some of the present deficiencies in knowledge are suggested.

Lowson, M. V.↗

NASA NTRS1950

The Boundary Layers in Fluids with Little Friction

The vortices forming in flowing water behind solid bodies are not represented correctly by the solution of the potential theory nor by Helmholtz's jets. Potential theory is unable to satisfy the condition that the water adheres at the wetted bodies, and its solutions of the fundamental hydrodynamic equations are at variance with the observation that the flow separates from the body at a certain point and sends forth a highly turbulent boundary layer into the free flow. Helmholtz's theory attempts to imitate the latter effect in such a way that it joins two potential flows, jet and still water, nonanalytical along a stream curve. The admissibility of this method is based on the fact that, at zero pressure, which is to prevail at the cited stream curve, the connection of the fluid, and with it the effect of adjacent parts on each other, is canceled. In reality, however, the pressure at these boundaries is definitely not zero, but can even be varied arbitrarily. Besides, Helmholtz's theory with its potential flows does not satisfy the condition of adherence nor explain the origin of the vortices, for in all of these problems, the friction must be taken into account on principle, according to the vortex theorem.

Blasius, H.↗

NASA NTRS1991

Theoretical studies of lasers and converters

Discussed here is Doppler broadening and its effects upon the stimulated emission cross-section connecting an upper level with a lower level in an iodine laser. The stimulated emission cross section is given. The level transitions for the iodine laser are illustrated as are the relative intensities of these transitions. Also discussed is the Voigt profile, which considers the effect of both Doppler broadening and collision broadening upon the absorption line shape. The equations describing the Voigt profile were added to the continuous flow laser model laser simulation program. The results were compared with the standard absorption profile reported in an earlier study. There seems to be no advantage to using the Voigt profile as the laser power output is relatively insensitive to changes in the absorption cross section at the pressures being considered for a space laser. One disadvantage of using the Voigt profile is the excessive numerical computations required by the additional equations.

Heinbockel, John H.↗

NASA NTRS1980

Upper atmosphere modifications due to chronic discharges of water vapor from space launch vehicle exhausts

The influences of transport, photodissociation, and frequency of injection on the global redistribution of water deposited in the earth's upper atmosphere by repeated launches of large rockets are investigated. Measurable environmental effects of the injected water are found to occur when the mesospheric water vapor mixing ratio exceeds 100 ppmv, which occurs over areas of order 20,000 sq km in connection with possible future Satellite Power System activities. These effects include (1) a 50% reduction in D-region ionization due to screening of L alpha radiation by water; (2) a 50% reduction of D-region ionization as a result of converting NO(+) to water cluster ions which possess more rapid recombination rates; (3) a doubling of OH concentrations below 100 km; and (4) a global doubling of nighttime E-region ionization due to L alpha and L beta radiations geocoronally scattered by atomic hydrogen released by photolysis of H2O. Mixing ratios of 1,000 ppmv necessary for the maintenance of clouds at the mesopause are reached only over areas of order 200 sq km.

Forbes, J. M.↗

NASA NTRS1986

Comparative oceanography of coastal lagoons

The hypothesis that physical lagoon characteristics and variability depend on the channel connecting the lagoon to the adjacent coastal ocean is evaluated. The geographical, hydrological, and oceanographic characteristics of 10 lagoon systems are described and analyzed; these oceanographic features are utilized to classify the lagoon systems. Choked lagoons (Laguna Joyuda, Coorong, Lake St.Lucia, Gippsland Lakes, Lake Songkla/Thale Luang/Thale Noi, and Lagoa dos Patos) are prevalent on coasts with high wave energy and low tidal range; restricted lagoons (Lake Pontchartrain and Laguna de Terminos) are located on low/medium wave energy coasts with a low tidal range; and leaky lagoons (Mississippi Sound and Belize Lagoon/Chetumal Bay) are connected to the ocean by wide tidal passes that transmit oceanic effects into the lagoon with a minimum of resistance. The data support the hypothesis that the nature of the connecting channel controls system functions.

Kjerfve, Bjorn↗

NASA NTRS1973

Investigation of the effect of stress on the chemistry, metabolism, and biophysics of collagen

The research is reported concerning the effect of stress on the chemistry in the connective tissue of the rat. It was found that within a day after administration of cortisol (stress harmone), a significant amount of the insoluble collagen disappeared from the skin. It is concluded that the abrupt catabolism of cutaneous collagen releases peptides. These peptides are rapidly degraded to free amino acids which are active in effecting liver glycogen synthesis, and provide a major energy source to assist the animal in the fight or flight reaction. It is proposed that cutaneous collagen represents a reserve energy pool, which can be mobilized via stress harmones.

Houck, J. C.↗

NASA NTRS1972

Effects of proton irradiation on several spacecraft science components.

In connection with programs for the exploration of the outer planets, several models have been developed and used to analyze the radiation hazard to the spacecraft. Typical components found in space flight science instruments have been tested to determine their capability to function properly before, after and, in some cases during, exposures to energy equivalenced levels predicted by the models. A summary of proton-irradiation tests is provided.

Parker, R. H.↗

NASA NTRS1975

PMR polyimides with improved high temperature performance

Studies were performed to investigate the effect of substituting a hexafluoro isopropyl idene connecting group for a carbonyl group of a PMR polyimide monomeric reactant on the thermo-mechanical properties processability of graphite fiber reinforced PMR polyimide composites. Composites were fabricated utilizing PMR methodology. Monomeric reactant solutions of various stoichiometric ratios were used to impregnate Hercules HTS graphite fiber. The processing characteristics and elevated temperature (600 F) mechanical properties of the composites are described.

Vannucci, R. D.↗

NASA NTRS1981

Solar energy control system

A solar energy control system for a hot air type solar energy heating system wherein thermocouples are arranged to sense the temperature of a solar collector, a space to be heated, and a top and bottom of a heat storage unit is disclosed. Pertinent thermocouples are differentially connected together, and these are employed to effect the operation of dampers, a fan, and an auxiliary heat source. In accomplishing this, the differential outputs from the thermocouples are amplified by a single amplifier by multiplexing techniques. Additionally, the amplifier is corrected as to offset by including as one multiplex channel a common reference signal.

Currie, J. R.↗

NASA NTRS1981

Analytical investigation of critical MHD phenomena

Development and analysis of schemes for suppression of the startup overvoltage transient in the AEDC High Performance Demonstration Experiment (HPDE), analysis of performance enhancement due to electrode voltage drop reduction by use of pyrolytic graphites in the HPDE, prediction of optimal loading schemes for the HPDE, prediction of PHDE performance with a diagonal electrical connection, and predictions of the likelihood and effects of axial current leakage between adjacent electrodes in the HPDE are reviewed. Simulations of tests at the AEDC/HPDE with STD Research Corporation multidimensional and time dependent computer codes provided additional validation for the computer codes and shed light on physical mechanisms which govern performance and durability of MHD power generators. The magnetoaerothermal effect was predicted by STD Research Corporation to have a significant effect on the HPDE/MHD generator performance at high interaction.

Source record↗

NASA NTRS1984

Investigation of electrodynamic stabilization and control of long orbiting tethers

The state-of-the-art in tether modelling among participants in the Tethered Satellite System (TSS) Program, the slack tether and its behavior, and certain advanced applications of the tether to problems in orbital mechanics are identified. The features and applications of the TSS software set are reviewed. Modelling the slack tether analytically with as many as 50 mass points and the application of this new model to a study of the behavior of a broken tether near the Shuttle are described. A reel control algorithm developed by SAO and examples of its use are described, including an example which also demonstrates the use of the tether in transferring a heavy payload from a low-orbiting Shuttle to a high circular orbit. Capture of a low-orbiting payload by a Space Station in high circular orbit is described. Energy transfer within a dumbbell-type spacecraft by cyclical reeling operations or gravitational effects on the natural elasticity of the connecting tether, it is shown, can circularize the orbit of the spacecraft.

Colombo, G.↗

NASA NTRS1985

On a possibility of inelasticity partial coefficient K sub gamma determination in pi C and pi Pb interactions at 10 to the 14th power eV (experiment PAMIR 1)

The investigation of hadron-nuclear interactions in Pamir experiment is carried out by means of X-ray emulsion chambers of two types: carbon (C) and lead (Pb). While comparing the results from the chambers of both types it was found a discrepancy in n sub h and E sub h(1)R values. The observed discrepancy in C and Pb chambers is connected with the difference in values of effective coefficients of energy transfer to the soft component K sub eff for C and Pb chambers.

Borisov, A. S.↗

NASA NTRS1987

On the wave excitation in the turbulent meteor trace

The solution to the problem of excitation of longitudinal and transverse electromagnetic waves in randomly inhomogeneous media is reduced to the derivation of a complex effective dielectric constant (EDC) tensor which nonlocally connects together the average macroscopic electromagnetic fields in continuous media, it is implied that the field values which are rapidly fluctuating on a microscopic scale in space and time become smoothed out in a specified way due to the inhomogeneous mixing of diffusion. Proceedings from the derived general expression for the EDC tensor new modes of longitudinal and transverse electromagnetic wave generation due to fluctuation in the parameters of the medium was predicted. In this connection, it is of interest to investigate the peculiarities of electromagnetic longitudinal and transverse wave propagation in such randomly inhomogeneous media where, apart from the charged particle concentration change, the random spatial and temporal changes of natural frequency of closely located oscillators take place.

Jandieri, G. V.↗

NASA NTRS1996

Decoherence and Exponential Law: A Solvable Model

We analyze a modified version of the 'AgBr' Hamiltonian, solve exactly the equations of motion in terms of SU(2) coherent states, and study the weak-coupling, macroscopic limit of the model, obtaining an exponential behavior at all times. The asymptotic dominance of the exponential behavior is representative of a purely stochastic evolution and can be derived quantum mechanically in the so-called van Hove's limit (which is a weak-coupling, macroscopic limit). At the same time, a temporal behavior of the exponential type, yielding a 'probability dissipation' is closely related to dephasing ('decoherence') effects and one can expect a close connection with a dissipative and irreversible behavior. We stress the central relevance of the problem of dissipation to the quantum measurement theory and to the general topic of decoherence.

Pascazio, Saverio↗

NASA NTRS1996

Collagen Gel Contraction by Fibroblasts: The Role of Myosin 2 and Gravity Effects

Several lines of evidence suggest that collagen organization by connective tissue cells is sensitive to force. For instance, in flight experiments on rats the collagen fibrils which were produced under weightlessness and which were immediately next to the tendon fibroblasts were shown to be oriented randomly around the cells while the older fibrils right next to these and which were produced under 1 G, were highly organized.

Johnson-Wint, Barbara P.↗