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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 1,477 records · Page 82
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Combined observations of meteors by image-orthicon television camera and multi-station radar

Observations from multiple sites of a radar network and by television of 29 individual meteors from February 1969 through June 1970 are reported. Only 12 of the meteors did not appear to fragment over all the observed portion of their trajectories. From these 12, the relation for the radar magnitude to the panchromatic absolute magnitude was found in terms of velocity of the meteor. A very tentative fit to the data on the duration of long enduring echoes versus visual absolute magnitude is made. The exponential decay characteristics of the later parts of several of the light curves are pointed out as possible evidence of mutual coalescence of droplets into which the meteoroid has completely broken.

Cook, A. F.↗
NASA NTRS1974

Rb-Sr age of the Civet Cat clast, 72255, 41

Plagioclase rich clasts, orthopyroxene rich matrix, purified pyroxene, and plagioclase from the Civet Cat clast define a Rb-Sr isochron age of 4.18 + or - 0.04 x 10 to the 9th power yr and an initial Sr-87/Sr-86 ratio of 0.69922 + or - 0.00005. The fit of all data to the line is within error except for plagioclase 3, and blank corrections are essentially negligible. The decay constant used is 1.39 x 10 to the minus 11th power yr.

Compston, W.↗
NASA NTRS1974

CO2 photodissociation and vibrational excitation in the planetary atmospheres

The principal subjects of investigation were the determination of the CO2 photodissociation quantum yields at the wavelengths from 1200 A to 1500 A, and the efficiency of electronic-to-vibrational energy transfer in the systems 0(1D) + CO, N2, CO2 yields 0(3P) + CO N2, CO2 vibrational energies. Measurements on the photodissociation quantum yield of CO2 in the 1200-1500 A region show that it is wavelength dependent, and for the six atomic line sources used, the quantum yield varied from 0.2 to 0.8. The data appear to fit the interpretation of stable CO2 bound states mixed with repulsive or predissociating states, since the low quantum yields coincide with the maximum structure in the CO2 absorption spectrum. The first reliable measurements were made on the efficiency of electronic-to-vibrational energy transfer in the systems 0(1D)-CO and 0(1D)-N2, using a uv resonance fluorescence technique. The 0(1D)-CO2 interaction was investigated by infrared techniques.

Slanger, T. G.↗
NASA NTRS1974

Water impact analysis of space shuttle solid rocket motor by the finite element method

Preliminary analysis showed that the doubly curved triangular shell elements were too stiff for these shell structures. The doubly curved quadrilateral shell elements were found to give much improved results. A total of six load cases were analyzed in this study. The load cases were either those resulting from a static test using reaction straps to simulate the drop conditions or under assumed hydrodynamic conditions resulting from a drop test. The latter hydrodynamic conditions were obtained through an emperical fit of available data. Results obtained from a linear analysis were found to be consistent with results obtained elsewhere with NASTRAN and BOSOR. The nonlinear analysis showed that the originally assumed loads would result in failure of the shell structures. The nonlinear analysis also showed that it was useful to apply internal pressure as a stabilizing influence on collapse. A final analysis with an updated estimate of load conditions resulted in linear behavior up to full load.

Buyukozturk, O.↗
NASA NTRS1973

Mars physical parameters as determined from Mariner 9 observations of the natural satellites

Derivation of values for the Mars gravity field, as well as the mass and spin axis direction, by processing combined radio and optical data taken with the Mariner 9 spacecraft. The optical data consists of 62 TV photographs of Phobos and Deimos taken during the Mars orbiting phase of Mariner 9. The radio data consists of apoapsis state vectors obtained from 195 one-revolution fits of the Doppler data. A first-order analytic theory is used to model both the satellites and the spacecraft's motion. However, the shallow resonance condition of Mariner 9's orbit necessitated development of a partial second-order theory to model the long-period perturbations which derive from Mars even-order tesseral harmonics. Use of an analytic theory allows rapid and inexpensive processing of both data types simultaneously. The results are in good agreement with those previously published from Mariner 9 Doppler and landmark data.

Born, G. H.↗
NASA NTRS1974

On the distribution of He+ in the plasmasphere from observations of resonantly scattered He II 304-A radiation

The intensity of the He II 304-A radiation in the night sky was measured from a sounding rocket launched from White Sands Missile Range on June 9, 1972. The data obtained on this flight are compared with predictions of theoretical models of the He(+) altitude distribution within the plasmasphere. The observations are not consistent with an isothermal equilibrium model of the helium ion in the plasmasphere, confirming earlier results. The data are best fit by a diffussive equilibrium model of exospheric He(+) having a plasma temperature gradient of 0.5 K per km and a number density at 1600 km of 200,000 He(+) ions per cu cm. In this model the ion densities are calculated without allowance for thermal diffusion. A similar model that allows for thermal diffusion and that has a He(+) number density at 1600 km of 1500 per cu cm and a temperature gradient of 1.2 K per km yields a less satisfactory fit to the observations but is more consistent with in situ satellite observations.

Paresce, F.↗
NASA NTRS1974

Investigation of nitric oxide decomposition in the temperature range 2500-4100 K

The decomposition of nitric oxide has been studied in the temperature range 2500-4100 K using a shock-tube technique. The principle result of the study was the determination of the rate constant (k) for the reaction O + NO yields N + O2. Mixtures of NO and N2O diluted in argon or krypton were heated by incident shock waves and the infrared emission from the fundamental vibration-rotation band of NO at 5.3 microns was used to monitor the time-varying NO concentration. The experimental values of k are fit closely by the expression k = (2.36 times 10 to the 9th power) x T x exp(-38,640/RT) cm cu/mole-sec, which also provides a good fit to previous data at higher and lower temperatures.

Flower, W. L.↗
NASA NTRS1974

A simple method of calculating power-law velocity profile exponents from experimental data

Analytical expressions for the effects of compressibility and heat transfer on laminar and turbulent shape factors H have been developed. Solving the turbulent equation for the power law velocity profile exponent N has resulted in a simple technique by which the N values of experimental turbulent profiles can be calculated directly from the integral parameters. Thus the data plotting, curve fitting, and slope measuring, which is the normal technique of obtaining experimental N values, is eliminated. The N values obtained by this method should be within the accuracy with which they could be measured.

Allen, J. M.↗
NASA NTRS1975

Thermal expansion in the nickel-chromium-aluminum and cobalt-chromium-aluminum systems to 1200 degrees C

Thermal expansion data were obtained on 12 Ni-Cr-Al and 9 Co-Cr-Al alloys by high temperature X-ray diffraction. The data were computer fit to an empirical thermal expansion equation developed in the study. It is shown that the fit is excellent to good, and that the expansion constants depend on phase but not on composition. Phases for the Ni-Cr-Al system and Co-Cr-Al system are given. Results indicate that only alpha Cr has an expansion constant low enough to minimize oxide spalling or coating cracking induced by thermal expansion mismatch.

Lowell, C. E.↗
NASA NTRS1974

Rate of recombination of oxygen atoms and CO at temperatures below ambient

The measurements reported were conducted with 30.0 torr CO, 40.0 torr argon, and varying amounts of carbon dioxide from about 20 to 230 torr. Measurements were made at 277, 272, 263, and 257 K. The pseudo-first-order decay rate as a function of carbon dioxide pressure is shown in a graph. An Arrhenius plot for the rate constants obtained from the measurements is also presented. A value for the activation energy was determined on the basis of a linear least-squares fit to the data.

Inn, E. C. Y.↗
NASA NTRS1975

Observations of the Circinus X-1 region

The X-ray telescope on board the OSO-7 satellite has provided observations of the Cir X-1 region for over 110 days between December 1971 and March 1973. Although statistically significant fluctuations in the 7- to 11-keV flux were measured, no periodicities in the range between 5 hours and 100 days were found to an upper limit of about 40 percent amplitude. Intensities in the 7- to 57-keV range show variability by a factor of approximately 25 and changes in the spectral shape reflected by a number spectral index varying from about 1.1 to about 3.0. There is a positive correlation between intensity and spectral shape, with a steeper spectrum at times of peak intensity. Although power-law, exponential, and blackbody spectral shapes are equally good fits to these data alone, examination of all the available data appears to rule out a simple blackbody spectrum, at least at times of maximum intensity.

Baity, W. A.↗
NASA NTRS1975

Planetary isophotes as a clue to aerosol characteristics

A study was conducted to see how much information could be extracted from the Mariner 9 Mars isophotes taken at a phase angle of approximately 60 deg. It was found that the Minnaert functions and both isotropic and Rayleigh scattering could easily be ruled out, and that it was essential to use forward-peaked phase functions, which were computed from Mie theory. Isophotes similar to those observed assuming a semi-infinite dust cloud with a considerable variation in particle properties and size distribution could be obtained, so long as the ratio of the multiply- to singly-scattered light was held within certain limits. These conditions are met by micron-sized, moderatly absorbing mineral grains whose mean size should not be much larger than a micron. It was also found that a dust cloud of finite optical thickness bounded from below by a Lambert ground would fit the isophote data.

Kattawar, G. W.↗
NASA NTRS1976

A new approach to the pulsed thermocouple for high gas temperature measurements

Pulsed thermocouple systems can be used to measure gas temperatures above the melting point of the thermocouple by various techniques of short term of intermittent exposure of the thermocouple operating at lower temperatures. An approach is described which uses a thermocouple cooled by a small jet of inert gas. When a measurement is to be made, the cooling jet is turned off and the thermocouple allowed to heat up to near its melting point, at which time the cooling is reapplied. The final temperature which the thermocouple should have attained is then calculated by extrapolating an exponential curve fit to the data. Temperature measurements can be recorded and displayed in near real time by using modern high-speed computing systems to perform these calculations. Examples of the technique applied to high temperature jet engine combustor development are presented.

Glawe, G. E.↗
NASA NTRS1975

Torsional potential function of glyoxal

We have shown, using the fact that glyoxal exists in the trans conformer and the pseudo stable cis conformer that a potential function can be calculated which fits the infrared data of the trans conformer and the microwave intensity data of the cis conformer. This potential function was extended to the d sub 1 and d sub 2 analogs. A study of the potential function of 1,3-butadiene using a different molecular geometry than was previously used was undertaken. Results are presented with different possible vibrational assignments and potential functions which would be consistent with the observed infrared and Raman spectra.

Durig, J. R.↗
NASA NTRS1976

Thermodynamics of a solar mixture of molecular hydrogen and helium at high pressure

The thermodynamic properties of a model molecular hydrogen and helium mixture are calculated in the strongly interacting region of 0.005 to 0.3 per cu cm for a range of temperatures that are of interest for the envelopes of the Jovian planets. Computed adiabats fit the gravity data and boundary conditions from model atmospheres of Jupiter.

Slattery, W. L.↗
NASA NTRS1976

Numerical determination of the transmissibility characteristics of a squeeze film damped forced vibration system

Numerical solutions of the governing equations of motion of a liquid squeeze film damped forced vibration system were carried out to examine the feasibility of using a liquid squeeze film to cushion and protect large structures, such as buildings, located in areas of high seismic activity. The mathematical model used was that for a single degree of freedom squeeze film damped spring mass system. The input disturbance was simulated by curve fitting actual seismic data with an eleventh order Lagranging polynomial technique. Only the normal component of the seismic input was considered. The nonlinear, nonhomogeneous governing differential equation of motion was solved numerically to determine the transmissibility over a wide range of physical parameters using a fourth-order Runge-Kutta technique. It is determined that a liquid squeeze film used as a damping agent in a spring-mass system can significantly reduce the response amplitude for a seismic input disturbance.

Sutton, M. A.↗
NASA NTRS1976

Outdoor performance results for NBS Round Robin collector no. 1

The efficiency of a PPG flat-plate solar collector was evaluated utilizing an outdoor solar collector test facility at the NASA-Lewis Research Center, as part of the National Bureau of Standards 'round robin' collector test program. The correlation equation for collector thermal efficiency Eta curve fit of the data was: Eta = 0.666 - 1.003(Btu/hr-sq ft-F) Theta, where the parameter Theta is the difference between the average fluid temperature and the ambient temperature, all divided by the total flux impinging on the collector.

Miller, D. R.↗
NASA NTRS1977

Space age health care delivery

Space age health care delivery is being delivered to both NASA astronauts and employees with primary emphasis on preventive medicine. The program relies heavily on comprehensive health physical exams, health education, screening programs and physical fitness programs. Medical data from the program is stored in a computer bank so epidemiological significance can be established and better procedures can be obtained. Besides health care delivery to the NASA population, NASA is working with HEW on a telemedicine project STARPAHC, applying space technology to provide health care delivery to remotely located populations.

Jones, W. L.↗