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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Effluent sampling of Scout D and Delta launch vehicle exhausts

Characterization of engine-exhaust effluents (hydrogen chloride, aluminum oxide, carbon dioxide, and carbon monoxide) has been attempted by conducting field experiments monitoring the exhaust cloud from a Scout-Algol III vehicle launch and a Delta-Thor vehicle launch. The exhaust cloud particulate size number distribution (total number of particles as a function of particle diameter), mass loading, morphology, and elemental composition have been determined within limitations. The gaseous species in the exhaust cloud have been identified. In addition to the ground-based measurements, instrumented aircraft flights through the low-altitude, stabilized-exhaust cloud provided measurements which identified CO and HCI gases and Al2O3 particles. Measurements of the initial exhaust cloud during formation and downwind at several distances have established sampling techniques which will be used for experimental verification of model predictions of effluent dispersion and fallout from exhaust clouds.

Hulten, W. C.↗
NASA NTRS1975

Particle flow within a transonic compressor rotor passage with application to laser-Doppler velocimetry

A theoretical analysis was conducted of the dynamic behavior of micron size particles moving in the three-dimensional flow field of a rotating transonic axial-flow air compressor rotor. The particle velocity lag and angular deviation relative to the gas were determined as functions of particle diameter, mass density and radial position. Particle size and density were varied over ranges selected to correspond to typical laser-Doppler velocimeter (LDV) flow field mapping applications. It was found that the particles move essentially on gas stream surfaces and that particle tracking is relatively insensitive to the rotor radial coordinate. Velocity lag and angular deviation increased whenever particle size or mass density increased, and particle tracking was more sensitive to a change in particle diameter than to a corresponding change in mass density. Results indicated that velocity and angular deviations generally less than 1 percent and 1 degree could be achieved with 1 gm/cc tracer particles with diameters of 1 micron or less.

Maxwell, B. R.↗
NASA NTRS1975

Intumescent coating modeling

A thermal response mathematical model for an intumescent coating system is developed. The model predicts indepth temperature profiles of the solid as a function of the fundamental kinetic, mass, and heat-transfer properties of the original coating system. In the model, swelling is based on an empirical function of the paint's weight loss. The model is used to describe the effectiveness of the coating for thermal protection. Using the thermal response time at the backface of the material as a criterion, a sensitivity analysis is made with respect to variation in individual properties, such as total expansion, to provide a guide for designing improved intumescing agents. The sensitivity analysis shows that total expansion and rate of expansion, along with other material properties, are important parameters for providing thermal protection. Finally, backface temperature histories are predicted and compared to experimental data obtained from a representative fire environment. Predicted temperatures agree within a maximum error of plus or minus 20%.

Cagliostro, D. E.↗
NASA NTRS1974

The use of the ion probe mass spectrometer in the measurement of hydrogen concentration gradients in Monel K 500

The ion probe mass spectrometer was used to measure hydrogen concentration gradients in cathodically charged Monel K 500. Initial work with the ion probe involved the calibration of the instrument and the establishment of a suitable experimental procedure for this application. Samples of Monel K 500 were cathodically charged in a weak sulfuric acid solution. By varying the current density, different levels of hydrogen were introduced into the samples. Hydrogen concentration gradients were taken by ion sputtering on the surface of these samples and monitoring the behavior of the hydrogen mass peak as a function of time. An attempt was made to determine the relative amounts of hydrogen in the bulk and grain boundaries by analyzing a fresh fracture surface with a higher proportion of grain boundary area. It was found that substantially more hydrogen was detected in the grain boundaries than in the bulk, confirming the predictions of previous workers. A sputter rate determination was made in order to establish the rate of erosion.

Truhan, J. J., Jr.↗
NASA NTRS1976

Measurement of the positron-electron reaction which produces a gamma ray pair in the region psi/3684/

An experiment was conducted to measure gamma ray pairs produced in the electron-positron reaction in the region of psi(3684) resonance. The apparatus consisted of two identical spectrometers mounted in a collinear configuration about the beam interaction region. Graphs are presented for the coplanarity angle between reconstructed gamma ray directions, for the scattering and energy deposition of gamma rays in the two crystals used, and for the observed rate of annihilation reactions as a function of center of mass energy.

Hughes, E. B.↗
NASA NTRS1977

Mars surface penetrator: System description

A point design of a penetrator system for a Mars mission is described. A strawman payload which is to conduct measurements of geophysical and meteorological parameters is included in the design. The subsystems used in the point design are delineated in terms of power, mass, volume, data, and functional modes. The prospects for survival of the rigors of emplacement are described. Data handling and communications plans are presented to allow consideration of the requirements placed by the penetrator on the orbiter and ground operations. The point design is technically feasible and the payload selection scientifically desirable.

Manning, L. A.↗
NASA NTRS1978

Enriched gas in clusters and the dynamics of galaxies and clusters Implications for theories of galaxy formation

Recent observations of the rotation of elliptical galaxies and of X-ray clusters are cited in developing a simple model for the formation of elliptical and spiral galaxies; the model provides for continuous galaxy formation from redshift values of about 100 onwards. In particular, it is argued that a fundamental alteration in the manner in which cosmic material fragmented to form stellar objects took place at a redshift value of approximately five. This change of regime may be employed to explain the formation of Population I disks, the origin of hot intracluster gas, the galaxy luminosity function, and the mass-to-light ratio stratification of galaxies.

Binney, J.↗
NASA NTRS1978

A technique for measuring in situ size distribution of aerosols

A multistage cascade impactor instrument employing piezoelectric crystals for real-time aerosol size distribution measurements is described in this paper. The instrument measures the aerosol mass concentration as a function of particle size in 10 size intervals ranging from 0.05 micrometers to 25 micrometers in diameter. The particles are then analyzed for elemental composition and morphology by means of scanning electron microscopy (SEM). Examples of particle size distributions in rocket motor exhaust plumes measured with the instrument are presented together with the elemental composition and morphology obtained by SEM.

Woods, D. C.↗
NASA NTRS1978

Rocket effluent size distributions made with a cascade quartz crystal microbalance

Airborne particulate size distribution measurements were made in the stabilized ground cloud from a Titan III C rocket just after launch from the Kennedy Space Center on May 12, 1977. The measurements were made from aboard a small twin engine aircraft instrumented with particle and gas sensors. The plume was followed for about 1 hour while making multiple passes through the cloud at varying altitudes. The results obtained with a ten-stage cascade quartz crystal microbalance impactor show that the mass concentration as a function of particle diameter is bimodal with the first maximum between 0.05 micrometers and 0.1 micrometers and the second maximum between 0.8 and 1.0 micrometer. Scanning electron microscope analysis were performed on the material collected and show distinctly different kinds of particles in the two modes.

Woods, D. C.↗
NASA NTRS1978

Stability of artificial and natural satellites

A quantitative measure of stability based on Hill's definition is evaluated for direct and retrograde satellite orbits. These orbits are known as Poincare's first kind in the restricted problem of three bodies. Onsets of possible instabilities and captures are established. A critical (maximum) value of the satellites orbital radius is found for stability as a remarkably simple function of the mass-parameter. The results are applied to the natural satellites of the solar system.

Szebehely, V.↗
NASA NTRS1979

Atmospheric entry systems for advanced Mars missions

A study of estimates of the mass and performance characteristics of entry system designs for advanced Mars missions is presented. The missions were: (1) a Mars Surface Sample Return Mission (MSSR), (2) a Mars Hard Lander, and (3) a Mars Aircraft Mission, and Viking technology or its extensions were used for these entry system conceptual designs. For the MSSR mission, various mission combinations were evaluated including different Mars Ascent Vehicle masses and the use of 2 through 4 stages of the IUS launch vehicle. The constraints for this Mars mission were the Shuttle payload bay geometry limitation and its massive requirements. Requirements for the simple Hard Lander Mission including entry and deceleration, using a parachute and a solid rocket are discussed. A design requirement for the Mars Aircraft Mission to minimize the total entry capsule/aircraft mass by combining entry functions and hardware into the aircraft system was described, and various approaches for supporting the folded aircraft within the aeroshell were examined.

Butts, A. J.↗
NASA NTRS1979

Lipids of aquatic sediments, recent and ancient

Computerized gas chromatography-mass spectrometry (GC-MS) is now an essential tool in the analysis of the complex mixtures of lipids (geolipids) encountered in aquatic sediments, both 'recent' (less than 1 million years old) and ancient. The application of MS, and particularly GC-MS, has been instrumental in the rapid development of organic geochemistry and environmental organic chemistry in recent years. The techniques used have resulted in the identification of numerous compounds of a variety of types in sediments. Most attention has been concentrated on molecules of limited size, mainly below 500 molecular mass, and of limited functionality, for examples, hydrocarbons, fatty acids and alcohols. Examples from recent studies (at Bristol) of contemporary, 'recent' and ancient sediments are presented and discussed.

Eglinton, G.↗
NASA NTRS1980

Examples of realistic aerosol particles collected in a cascade impactor

In this paper some scanning electron microscope photomicrographs showing examples of a variety of particulate aerosol shapes are presented. Compositions of particles also are presented. These particles represent samples from a number of different sources and locations including: solid propellant rocket motor plumes, active volcano plumes, the lower stratosphere over Sondrestrom, Greenland, and the upper troposphere over northern Texas. The particles were collected from aboard an aircraft with a cascade impactor which classified them according to aerodynamic size into 10 size intervals ranging from submicron to greater than 25 micrometers in diameter. The cascade impactor also served to measure the mass concentration as a function of particle size. The variety of shapes and compositions found among these particles suggest difficulties in obtaining reliable size distribution data from light scattering measurements.

Woods, D. C.↗
NASA NTRS1982

Effect of Fluid Flow on Zinc Electrodeposits from Acid Chloride Electrolytes

Zinc was deposited potentiostatically from acid chloride baths. Once bath chemistry and electrochemistry were controlled, the study was focused on convective mass transfer at horizontal electrodes and its effect on cell performance. A laser schlieren imaging technique allowed in situ observations of flow patterns and their correlation with current transients. Convection was turbulent and mass transfer as a function of Rayleigh number was well correlated by: Sh = 0.14 R to the 1/3 power. Similarly, convection initiation time was correlated by DT/d squared = 38 Ra to the -2/3 power. Time scale of fluctuations was about half the initiation time. Taking the boundary layer thickness as a characteristic length, a critical Rayleigh number for the onset of convection was deduced: Ra sub CR = 5000. Placing the anode on the top of the cathode completely changed the flow pattern but kept the I-t curves identical whereas the use of a cathode grid doubled the limiting current. A well defined plateau in the current voltage curves suggested that hydrogen evolution has been successfully inhibited. Finally, long time deposition showed that convection at horizontal electrodes increased the induction time for dentrite growth by at least a factor of 2 with respect to a vertical wire.

Abdelmassir, A. A.↗
NASA NTRS1984

Analytic modeling of a spray diffusion flame

A detailed model for a spray diffusion flame is described. The model is based on the boundary layer form of the equations of motion, with droplet transport accounted for using a discretized droplet size distribution function. Interphase transport of mass and energy are accounted for, with a flame-sheet model used to describe the combustion process on a droplet scale. Near dynamic equilibrium is assumed for the description of droplet transport; droplets can diffuse relative to the gas phase. Gas-phase mixing is accounted for using a two-equation turbulence model; buoyancy effects are included, with a temperature fluctuation equation used to account for buoyancy effects on turbulence structure. Thermal radiation from gas-phase CO2 and H2O is included. Gas-phase chemical kinetics are modeled using a 20-reaction, 10-species version of the advanced quasi-global chemical kinetics formulation. Results are compared with data for a vaporizing Freon spray and a pentane spray flame. It is shown that the computational approach provides a reasonably valid picture of the overall development of a spray diffusion flame, and, furthermore, provides a useful tool for the parametric examination of the spray combustion process.

Harsha, P. T.↗
NASA NTRS1985

Tether Fundamentals

Forces on tethered satellites, tether tension as a function of the effective mass, and parameters of candidate tether materials are examined. Illustrations show: stabilization control law; tethered satellite deployment and retrieval; angular momentum; electric motor effect reboost; a very long tether phenomenon; shuttle tethered satellite effects on the orbiter; artificial gravity; tethered satellite rendezvous docking relative velocity; and scaling up from the shuttle/TSS. Limitations of the tethered satellite system and of tether properties as well as cost/benefits trades for future applications are considered.

Rupp, C.↗
NASA NTRS1985

Progress on Experimental Impact Studies

Experimental impact studies were undertaken. Ejecta velocity distributions and related results from regolith targets were studied. The velocity distributions, energy partitioning, and related properties from 14 impacts at speeds 5 to 2321 m/s in vacuo into regolith-like fine powders were derived. Data are analyzed on: velocity and mass distributions as a function of azimuth around the crater during oblique impacts catastrophic disruption of spherical targets of variable strength, and catastrophic disruption of irregular-shaped natural rock targets and artificial granular aggregate targets.

Hartmann, W. K.↗
NASA NTRS1986

Derivation of heavy (10-210 AMU) ion composition and flow parameters for the Giotto PICCA instrument

The Giotto heavy ion analyzer RPA2-PICCA was designed to identify the composition and distribution of heavy thermal positive ions in the coma of comet Halley. The instrument is an electrostatic analyzer which takes advantage of the large relative flyby velocity and the fact that the ions in the inner coma should be cold and predominantly singly charged. A method of deconvolving E/Q measurements to yield ion mass composition, temperature, and flow velocity is presented. The measurements are used to investigate the dynamic behavior of the ions and variations in mass composition as a function of cometary distance.

Mitchell, D. L.↗