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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Science on Spacelab

Spacelab was developed by the European Space Agency for the conduction of scientific and technological experiments in space. Spacelab can be taken into earth orbit by the Space Shuttle and returned to earth after a period of 1-3 weeks. The Spacelab modular system of pallets, pressurized modules, and racks can contain large payloads with high power and telemetry requirements. A working group has defined the 'Atmospheres, Magnetospheres, and Plasmas-in-Space' project. The project objectives include the absolute measurement of solar flux in a number of carefully selected bands at the same time at which atmospheric measurements are made. NASA is committed to the concept that the scientist is to play a key role in its scientific programs.

Schmerling, E. R.↗
NASA NTRS1997

Kinetics and Mechanism of the Reaction of Hydoxyl Radicals with Acetonitrile under Atmospheric Conditions

The pulsed laser photolysis-pulsed laser induced fluorescence technique has been employed to determine absolute rate coefficients for the reaction OH + CH3CN (1) and its isotopic variants, OH + CD3CN (2), OD + CH3CN (3), and OD + CD3CN (4). Reactions 1 and 2 were studied as a function of pressure and temperature in N2, N2/O2, and He buffer gases. In the absence of O2 all four reactions displayed well-behaved kinetics with exponential OH decays and pseudo-first rate constants which were proportional to substrate concentration. Data obtained in N2 over the range 50-700 Torr at 298 K are consistent with k(sub 1), showing a small pressure dependence. The Arrhenius expression obtained by averaging data at all pressures in k(sub 1)(T) = (1.1(sup +0.5)/(sub -0.3)) x 10(exp -12) exp[(-1130 +/- 90)/T] cu cm /(molecule s). The kinetics of reaction 2 are found to be pressure dependent with k(sub 2) (298 K) increasing from (1.21 +/- 0.12) x 10(exp -14) to (2.16 +/- 0.11) x 10(exp -14) cm(exp 3)/ (molecule s) over the pressure range 50-700 Torr of N2 at 298 K. Data at pressures greater than 600 Torr give k(sub 2)(T) = (9.4((sup +13.4)(sub -5.0))) x 10(exp -13) exp[(-1180 +/- 250)/T] cu cm/(molecule s). The rates of reactions 3 and 4 are found to be independent of pressure over the range 50-700 Torr of N2 with 298 K rate coefficient given by k(sub 3) =(3.18 +/- 0.40) x 10(exp -14) cu cm/(molecule s) and k(sub 4) = (2.25 +/-0.28) x 10(exp -14) cu cm/(molecule s). In the presence of O2 each reaction shows complex (non-pseudo-first-order) kinetic behavior and/or an apparent decrease in the observed rate constant with increasing [O2], indicating the presence of significant OH or OD regeneration. Observation of regeneration of OH in (2) and OD in (3) is indicative of a reaction channel which proceeds via addition followed by reaction of the adduct, or one of its decomposition products, with O2. The observed OH and OD decay profiles have been modeled by using a simple mechanistic scheme to extract kinetic information about the adduct reations with O2 and branching ratios for OH regeneration. A plausible mechanism for OH regeneration in (2) involves OH addition to the nitrogen atom followed by O2 addition to the cyano carbon atom, isomeriazation and decomposition to D2CO + DOCN + OH. Our results suggest that the OH + CH3CN reaction occurs via a complex mechanism involving both bimolecular and termolecular pathways, analogous to the mechanisms for the the important atmospheric reactions of OH with CO and HNO3.

Hynes, A. J.↗
NASA NTRS1999

A Scale-Invariant Model of Statistical Mechanics and Modified Forms of the First and the Second Laws of Thermodynamics

A scale-invariant statistical theory of fields is presented that leads to invariant definition of density, velocity, temperature, and pressure, The definition of Boltzmann constant is introduced as k(sub k) = m(sub k)v(sub k)c = 1.381 x 10(exp -23) J x K(exp -1), suggesting that the Kelvin absolute temperature scale is equivalent to a length scale. Two new state variables called the reversible heat Q(sub rev) = TS and the reversible work W(sub rev) = PV are introduced. The modified forms of the first and second law of thermodynamics are presented. The microscopic definition of heat (work) is presented as the kinetic energy due to the random (peculiar) translational, rotational, and pulsational motions. The Gibbs free energy of an element at scale Beta is identified as the total system energy at scale (Beta-1), thus leading to an invariant form of the first law of thermodynamics U(sub Beta) = Q(sub Beta) - W(sub Beta) +N(e3)U(sub Beta-1).

Sohrab, Siavash H.↗
NASA NTRS1971

An evaluation of methods for scaling aircraft noise perception

One hundred and twenty recorded sounds, including jets, turboprops, piston engined aircraft and helicopters were rated by a panel of subjects in a paired comparison test. The results were analyzed to evaluate a number of noise rating procedures in terms of their ability to accurately estimate both relative and absolute perceived noise levels. It was found that the complex procedures developed by Stevens, Zwicker and Kryter are superior to other scales. The main advantage of these methods over the more convenient weighted sound pressure level scales lies in their ability to cope with signals over a wide range of bandwidth. However, Stevens' loudness level scale and the perceived noise level scale both overestimate the growth of perceived level with intensity because of an apparent deficiency in the band level summation rule. A simple correction is proposed which will enable these scales to properly account for the experimental observations.

Ollerhead, J. B.↗
NASA NTRS1984

A statistical correlation method for the retrieval of atmospheric moisture profiles by microwave radiometry

A statistical correlation technique is applied to the retrieval of vertical moisture profiles under clear-sky conditions from down-looking radiometric measurements of atmospheric radiation at microwave wavelengths. For a given set of channels, the method selects the optimum radiometric channels for estimating water vapor at specific pressure levels between the surface and 300 mb. The water vapor mixing ratio at these pressure levels is then calculated from a linear combination of the selected channel brightness temperatures. To test its validity the algorithm was applied, in a numerical experiment, to fifty independent tropical radiosondes. The rms absolute deviation of the estimated moisture profiles from the actual profiles was comparable to that obtained using an iterative retrieval method reported earlier. The statistical method, however, requires several orders of magnitude less computer time than the iterative method; it is suitable for high speed processing of large amounts of data.

Kakar, R. K.↗
NASA NTRS1992

Saturated fluorescence measurements of the hydroxyl radical in laminar high-pressure C2H6/O2/N2 flames

Saturation of a transition of the OH molecule in high-pressure flames is demonstrated by obtaining saturation curves in C2H6/O2/N2 laminar flames at 1, 6.1, 9.2, and 12.3 atm. Quantitative fluorescence measurements of OH number density at pressures to 12.3 atm are presented. To assess the efficacy of the balanced cross-rate model for high-pressure flames, laser-saturated fluorescence measurements, which were calibrated in an atmospheric-pressure flame, are compared with absorption measurements at 3.1 and 6.1 atm. At 3.1 atm the absorption and fluorescence measurements compare well. At 6.1 atm, however, the concentrations given by lasre-saturated fluorescence are about 25 percent lower than the absorption values, indicating some depletion of the laser-coupled levels beyond that at atmospheric pressure. By using a reasonable estimate for the finite sensitivity to quenching, it is anticipated that fluorescence measurements that are calibrated at 1 atm can be applied to flames at about 10 atm with absolute errors within +/- 50 percent.

Carter, Campbell D.↗
NASA NTRS1978

Surface temperatures and glassy state investigations in tribology, part 1

The research in this report is divided into two categories: (1) lubricant rheological behavior, and (2) thermal behavior of a simulated elastohydrodynamic contact. The studies of the lubricant rheological behavior consists of high pressure, low shear rate viscosity measurements, viscoelastic transition measurements, by volume dilatometry, dielectric transitions at atmospheric pressure and light scattering transitions. Lubricant shear stress-strain behavior in the amorphous glassy state was measured on several fluids. It appears clear from these investigations that many lubricants undergo viscoplastic transitions in typical EHD contacts and that the lubricant has a limiting maximum shear stress it can support which in turn will determine the traction in the contact except in cases of very low slide-roll ratio. Surface temperature measurements were made for a naphthenic mineral oil and a polyphenyl ether. The maximum surface temperature in these experiments was approximately symmetrical about the zero slide-roll ration except for absolute values of slide-roll ratio greater than about 0.9. Additional surface temperature measurements were made in contacts with rough surfaces where the composite surface roughness was approximately equal to the EHD film thickness. A regression analysis was done to obtain a predictive equation for surface temperatures as a function of pressure, sliding speed, and surface roughness. A correction factor for surface roughness effects to the typical flash temperature analysis was found.

Winer, W. O.↗
NASA NTRS1983

Hyperfiltration wash water recovery subsystem - Design and test results

The Hyperfiltration Wash Water Recovery (HWWR) subsystem, designed to offer low-power high-volume wash water purification for extended mission spacecraft, is discussed in terms of preprototype design and configuration. Heated wash water collected from the shower, hand wash, and laundry flows into a temperature-controlled (374 K) waste storage tank. Two parallel 25 micron absolute filters at the tank outlet remove large particles from the feed stream. A positive displacement feed pump delivers wash water to the hyperfiltration module at a constant flow rate of 0.20 lpm with discharge pressure variations from 4181-7239 Kpa. The hyperfiltration membrane module is a single-pass design including 36 porous stainless steel tubes, and is designed to provide an approximate water recovery rate of 90 percent. Permeate and brine water flows are monitored by flow meters, and removal of urea and ammonia is achieved by adding 15 percent NaOCl solution to the permeate fluid stream. An alternate module design using two diameters of tubing (allowing a smaller pressure drop and a larger membrane area) gave a superior predicted performance over the first module with larger tubing throughout.

Reysa, R. P.↗
NASA NTRS1992

The 2nd phase of the LEANDRE program: Water-vapor DIAL measurement

As a follow-on of the backscattered lidar, a differential absorption lidar (LEANDRE 2) is now being developed as part of the LEANDRE program for airborne meteorological studies. The primary measurement objective of LEANDRE 2 is water vapor. Pressure and temperature measurements are aimed at a second stage. The goals are to obtain a horizontal resolution of a few hundred meters for a vertical resolution of less than a hundred meters, with an absolute accuracy of 10 percent for humidity measurement. As compatibility is an important feature between the 2 first phases of LEANDRE, most of the LEANDRE 1 sub-system will be used and adapted for LEANDRE 2. For example, detection electronics, central computer, detectors and telescope will be the same. However, important modifications have to be done on the laser source, and spectral control has to be added. Most of the work is thus devoted to those developments, and the status is presented here.

Quaglia, P.↗
NASA NTRS1994

A rare gas optics-free absolute photon flux and energy analyzer to provide absolute photoionization rates of inflowing interstellar neutrals

A prototype spectrometer has been developed for space applications requiring long term absolute EUV photon flux measurements. The energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking advantage of the photoelectric effect in one of several rare gases at low pressures. Using an electron energy spectrometer, followed by an electron multiplier detector, pulses due to individual electrons are counted. The overall efficiency of this process can be made essentially independent of gain drifts in the signal path, and the secular degradation of optical components which is often a problem in other techniques is avoided. A very important feature of this approach is its freedom from the problem of overlapping spectral orders that plagues grating EUV spectrometers. An instrument with these features has not been flown before, but is essential to further advances in our understanding of solar EUV flux dynamics, and the coupled dynamics of terrestrial and planetary atmospheres. The detailed characteristics of this optics-free spectrometer are presented in the publications section.

Judge, Darrell L.↗
NASA NTRS1995

Application of a Navier-Stokes Solver to the Analysis of Multielement Airfoils and Wings Using Multizonal Grid Techniques

A computational study was performed to determine the predictive capability of a Reynolds averaged Navier-Stokes code (CFL3D) for two-dimensional and three-dimensional multielement high-lift systems. Three configurations were analyzed: a three-element airfoil, a wing with a full span flap and a wing with a partial span flap. In order to accurately model these complex geometries, two different multizonal structured grid techniques were employed. For the airfoil and full span wing configurations, a chimera or overset grid technique was used. The results of the airfoil analysis illustrated that although the absolute values of lift were somewhat in error, the code was able to predict reasonably well the variation with Reynolds number and flap position. The full span flap analysis demonstrated good agreement with experimental surface pressure data over the wing and flap. Multiblock patched grids were used to model the partial span flap wing. A modification to an existing patched- grid algorithm was required to analyze the configuration as modeled. Comparisons with experimental data were very good, indicating the applicability of the patched-grid technique to analyses of these complex geometries.

Jones, Kenneth M.↗
NASA NTRS2000

Kinetics of the Cl(2)P(J)) + CH4 Reaction: Effects of Secondary Chemistry Below 300 K

Absolute rate data for the Cl(2)P(J) + CH4 yields HCl + CH3 reaction have been obtained from 218 to 298 K by using the discharge-flow resonance fluorescence technique at I Torr total pressure. The result at 298 K is (10.1 +/- 0.6) x 10(exp -14) cu cm/molecule/s. The temperature dependence in Arrhenius form is (6.5 +/- 0.9 ) x 10(exp -12) exp[(-1235 +/- 34 )/T]. The errors given are one standard deviation; overall experimental error is estimated at +/- 15%. Because of the relatively large disagreement among earlier measurements at low temperatures, the results were examined for possible effects of non-Boltzmann spin distribution and vibrational excitation of CH4, secondary chemistry of CH3 radicals, and impurities in the CH4 source. There was no significant change in the observed rate constant when an efficient spin quencher, CF4, was added and estimates indicate that vibrational partitioning in CH4 should be at the ambient reactor temperature before the start of the reaction. The results were also independent of the source of Cl atoms (microwave discharge or thermal decomposition of Cl2) and whether CH4 was purified in-situ. However, the observed rate constant did depend on initial Cl atom concentrations and to a lesser extent on CH4 concentrations. Numerical simulations were used to assess the importance of secondary chemistry over a range of reactant concentrations

Wang, J. J.↗
NASA NTRS2000

Mass Spectrometric and Langmuir Probe Measurements in Inductively Coupled Plasmas in Ar, CHF3/Ar and CHF3/Ar/O2 Mixtures

Absolute fluxes and energy distributions of ions in inductively coupled plasmas of Ar, CHF3/Ar, and CHF3/Ar/O2 have been measured. These plasmas were generated in a Gaseous Electronics Conference (GEC) cell modified for inductive coupling at pressures 10-50 mTorr and 100-300 W of 13.56 MHz radio frequency (RF) power in various feedgas mixtures. In pure Ar plasmas, the Ar(+) flux increases linearly with pressure as well as RF-power. Total ion flux in CHF3 mixtures decreases with increase in pressure and also CHF3 concentration. Relative ion fluxes observed in the present studies are analyzed with the help of available cross sections for electron impact ionization and charge-exchange ion-molecule reactions. Measurements of plasma potential, electron and ion number densities, electron energy distribution function, and mean electron energy have also been made in the center of the plasma with a RF compensated Langmuir probe. Plasma potential values are compared with the mean ion energies determined from the measured ion energy distributions and are consistent. Electron temperature, plasma potential, and mean ion energy vary inversely with pressure, but increase with CHF3 content in the mixture.

Kim, J. S.↗
NASA NTRS2003

Studies of Elementary Reactions of Chemical Importance in the Atmospheres of Planets

The paper discusses the following: 1. F + Cl2 Kinetics. Absolute rate constant for the reaction F(P-2) with Cl2 has been measured using the discharge flow kinetics technique coupled to mass spectrometric detection at T = 180 - 360 K and 1 Torr He nominal pressure. 2. Vapor pressure system. The main effort on the vapor pressure system involved the design and construction of an insulated enclosure ("Bakeout Box") to improve the uniformity of heating during the bakeout process. 3. Sunphotometer System. This period saw the completion of the two-channel sunphotometer, its calibration, and two field deployments. 4. Vibrational-to-translation (V-T) transfer rates for light hydrocarbons at low temperatures are important parameters in thermal-structure models of the upper atmospheres of the outer planets and their satellites. However, the required data are either simply not available or do not extend to the low temperatures found in those systems. Because methane is such an important constituent in outer planet atmospheres, we have initiated a program to measure the temperature dependence of (V-T) rates for its relaxation by appropriate collision partners. 5. The central focus of this research has been the vapor phase nucleation and growth of metals/refractory species into small particles and the aggregation of these primary particles into larger structures. These topics are part of the broader goal of understanding the conditions under which interstellar dust grains condense from stellar outflows and how these small dust grains coagulate into larger bodies such as planetesimals or planets.

Nesbitt, Fred L.↗
NASA NTRS2011

Laser Truss Sensor for Segmented Telescope Phasing

A paper describes the laser truss sensor (LTS) for detecting piston motion between two adjacent telescope segment edges. LTS is formed by two point-to-point laser metrology gauges in a crossed geometry. A high-resolution (<30 nm) LTS can be implemented with existing laser metrology gauges. The distance change between the reference plane and the target plane is measured as a function of the phase change between the reference and target beams. To ease the bandwidth requirements for phase detection electronics (or phase meter), homodyne or heterodyne detection techniques have been used. The phase of the target beam also changes with the refractive index of air, which changes with the air pressure, temperature, and humidity. This error can be minimized by enclosing the metrology beams in baffles. For longer-term (weeks) tracking at the micron level accuracy, the same gauge can be operated in the absolute metrology mode with an accuracy of microns; to implement absolute metrology, two laser frequencies will be used on the same gauge. Absolute metrology using heterodyne laser gauges is a demonstrated technology. Complexity of laser source fiber distribution can be optimized using the range-gated metrology (RGM) approach.

Liu, Duncan T.↗
NASA NTRS1978

Investigation of the jet-wake flow of a highly loaded centrifugal compressor impeller

Investigations, aimed at developing a better understanding of the complex flow field in high performance centrifugal compressors were performed. Newly developed measuring techniques for unsteady static and total pressures as well as flow directions, and a digital data analysis system for fluctuating signals were thoroughly tested. The loss-affected mixing process of the distorted impeller discharge flow was investigated in detail, in the absolute and relative system, at impeller tip speeds up to 380 m/s. A theoretical analysis proved good coincidence of the test results with the DEAN-SENOO theory, which was extended to compressible flows.

Eckardt, D.↗
NASA NTRS1922

Skin frictional resistance of plane surfaces in air

Given here is the most recent research on skin frictional resistance of plane surfaces in air that was conducted by Dr. Wieselsberger under the direction of Dr. Prandtl of Gottingen University. In all, 16 models were tested. These were divided into four groups, as follows: 1) cloth, in the original condition; 2) cloth, with the nap singed off; 3) cloth, with three coats of dope; and 4) cloth, with six coats of dope. Each group consisted of four models of uniform width, 1 meter, and of lengths of 0.5, 1.0, 1.5, and 2.0 meters. Tests were made on each model at speeds varying from 7.0 to 50 meters per second. The observed total resistance was corrected for the form resistance which was obtained from the pressure distribution on the end of the model. Previous tests had shown that the form resistance due to the rounded front edge used on the models was negligible. The results are expressed in terms of the absolute coefficient of frictionless resistance, C(sub F).

Diehl, W S↗
NASA NTRS1979

Rate constant for the reaction of atomic chlorine with formaldehyde from 200 to 500 K

The absolute rate constant for the reaction of atomic chlorine with formaldehyde has been measured from 200 to 500 K using the flash photolysis-resonance fluorescence technique. The results were independent of substantial variations in (H2CO), total pressure (Ar), and flash intensity (i.e., initial (Cl)). The rate constant was shown to be invariant with temperature, the best representation for this temperature range being k-sub-1 = (7.48 + or - 0.50) times 10 to the -11 cu cm/molecule sec, where the error is one standard deviation. This result is compared with the only previous determination of k-sub-1, which was a relative value obtained at 298 K. The rate constant is theoretically discussed, and the potential importance of the reaction in stratospheric chemistry is considered.

Michael, J. V.↗