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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Non-LTE analysis of extremely helium-rich stars. The hot sdO stars LSE 153, 259 and 263

Results of a non-LTE fine analysis based mainly on high-resolution CASPEC spectra for three extremely helium-rich sdO stars are discussed in order to explain hydrogen deficiency in single stars. High temperature (Teff = 70,000 to 75,000 K) and a position in the log Teff - log g diagram were found close to the Eddington limit. Various abundance estimates are derived for hydrogen (upper limits only), carbon, nitrogen, and magnesium. Hydrogen is reduced to less than 10 percent by number in LSE 153 and LSE 263, and to less than 5 percent in LSE 259. The hydrogen deficiency is accompanied by nitrogen- and carbon-enrichment in LSE 153 and LSE 259 only. In LSE 263, carbon is depleted by about 1 dex. Stellar masses obtained by assuming that a core mass-luminosity relation holds for these stars, were found to be in the range 0.6-0.9 solar mass, yielding luminosities log L/L:solar = 3.7-4.5. Two of the program stars (LSE 153 and 259) appear to be possible successors of the R CrB and helium B stars, whereas the third star (LSE 263) displays a much lower carbon content in its photosphere making it an exceptional case among the known hydrogen deficient stars.

Husfeld, D.↗
NASA NTRS1982

The mass of hot, shocked CO in Orion - First observations of the J = 17-J = 16 transition at 153 microns

Observations of the Kleinmann-Low Nebula in Orion detected the J = 17-J = 16 transition of CO at 153 microns and at a flux level of 7 x 10 to the -17th W/sq cm. The total mass of hot (not less than about 750 K) carbon monoxide in the nebula is estimated at 8 x 10 to the 30th g, and the total hydrogen mass at this temperature is assessed to be about 1.5 solar masses. A CO column density of about 4 x 10 to the 17th per sq cm is derived for the region, which agrees with those predictions made by Storey et al. (1981), and an apparent deficit of oxygen in the nebula is discussed.

Stacey, G. J.↗
NASA NTRS1984

The calibration of photographic and spectroscopic films: The response of 2aO film to small dosages of alpha particles from 3/10th's rad to 8 rads at energy levels 153 MeV, 79 MeV and 47 MeV

The 2aO film, pre-exposed to a series of neutral density filters which on development under standard conditions will produce the standard H-D curve for that film, were then exposed to Alpha paricles with a dose range of 3/10ths rads to 8 rads while varying the energy of the particles using 153 MeV, 70 MeV, and 47 MeV, respectively. An analysis of the film shows that the 3/10th rad dose produces the lowest optical density changes at 70 MeV and 47 MeV. While the optical density readings for the darker patterns seem to oscillate and decrease when exposed to radiation dosages of 3/10th rads to 8 rads.

Hammond, E. C., Jr.↗
NASA NTRS1990

A 153 day periodicity in the occurrence of solar flares producing energetic interplanetary electrons

The occurrence times of energetic (above 10 MeV) solar flare electron events observed on board the ISEE 3 spacecraft during the years 1978-1982 have been examined; strong evidence is found for a periodicity of 153 + or - 2 days, confirming the discovery of a periodicity in the occurrence of solar flares producing X-rays and gamma rays. The Rayleigh test for periodicity is applied to obtain a probability of less than 10 to the -6th that the times of the electron flares were drawn from a uniform distribution.

Droge, Wolfgang↗
NASA NTRS1994

Low density of neutral hydrogen and helium in the local interstellar medium: Extreme Ultraviolet Explorer photometry of the Lyman continuum of the hot white dwarfs MCT 0501-2858, MCT 0455-2812, HZ 43, and GD 153

The first comprehensive sky survey of the extreme ultraviolet (EUV) spectral range performed by the Extreme Ultraviolet Explorer (EUVE) has uncovered a handful of very bright sources at wavelengths longer than the He I 504 A photoionization edge. Among these objects are four white dwarfs with exceptionally low interstellar medium (ISM) column densities along the line of sight. Analysis of EUV photometry of the He-rich DO white dwarf MCT 0501-2858 and the H-rich DA white dwarf MCT 0455-2812 along one line of sight and of the DA white dwarfs HZ 43 and GD 153 near the north Galactic pole indicates that the overall minimum column density of the neutral material centered on the Sun is N(H I) = 0.5-1.0 x 10(exp 18)/sq cm. In the case of MCT 0501-2858, EUV photometric measurements provide a clear constraint to the effective temperature (60,000-70,000 K). Given these neutral hydrogen columns, the actual contribution to the density of neutral species from the immediate solar environment (the 'local fluff') would only cover a distance of approximately equals 2-3 pc (assuming an average density n(H I) = 0.1/cu cm) leaving these lines of sight almost entirely within the hot phase of the ISM. A preliminary examination of the complete EUVE long-wavelength survey indicates that these lines of sight are exceptional and set a minimum column density in the solar environment.

Vennes, Stephane↗
NASA NTRS1993

Absorption by H2O and H2O-N2 mixtures at 153 GHz

New experimental data on and a theoretical analysis of the absorption coefficient at 153 GHz are presented for pure water vapor and water vapor-nitrogen mixtures. This frequency is 30 GHz lower than the resonant frequency of the nearest strong water line (183 GHz) and complements our previous measurements at 213 GHz. The pressure dependence is observed to be quadratic in the case of pure water vapor, while in the case of mixtures there are both linear and quadratic density components. By fitting our experimental data taken at several temperatures we have obtained the temperature dependence of the absorption. Our experimental data are compared to several theoretical models with and without a continuum contribution, and we find that none of the models is in very good agreement with the data; in the case of pure water vapor, the continuum contribution calculated using the recent theoretical absorption gives the best results. In general, the agreement between the data and the various models is less satisfactory than found previously in the high-frequency wing. The anisotropy in the observed absorption differs from that currently used in atmospheric models.

Bauer, A.↗
NASA NTRS1976

Lidar measurement of stratospheric dust from St. Augustine Volcano

The detection of a stratospheric dust layer of probable volcanic origin over Hampton, Va., on the evening of Jan. 28, 1976, with a 20-inch lidar system is reported. A digitized cathode-ray-tube trace of a return signal from altitudes of 12 to 24 km on January 28 is provided, and it is shown that 38% of the return was due to stratospheric aerosol. Noting that measurements on January 22 and February 2 showed no traces of this stratospheric dust layer, trajectories of dust-laden air parcels are followed from initiation at 0000 GMT on January 24 at the St. Augustine Volcano on Augustine Island, Alaska (59 deg N, 153 deg W). Analysis of the trajectories indicates that dust injected into the stratosphere at 59 deg N, 153 deg W could have been transported to Virginia in about 4 days. It is concluded that if the St. Augustine Volcano was the source of the dust, at least 23 deg of meridional transport from polar latitudes was observed.

Remsberg, E. E.↗
NASA NTRS1986

Super active regions and production of major solar flares

The success of imaging detectors with small fields of veiw such as HXIS or P/OF (Pinhole/Occulter Facility) depends heavily on pointing to the right place at the right time. During the solar maximum years many active regions coexist on the solar disk. Therefore, in order to point the imaging detector to the right place, it is important to know which active region is most likely to produce major flares. This knowledge is also important for flare prediction. As a first step toward this goal active regions have been identified which produced major flares observed by HXRBS (Hard X-Ray Burst Spectrometer) on SMM during February 1980 through December 1983. For this study the HXRBS Event List, an updated flare list compiled by the HXRBS group, and the Comprehensive Reports of the Solar Geophysical Data were used. During this period, HXRBS detected hard X-rays from approx 7000 solar flares, out of which only 441 flares produced X-rays with peak count rates exceeding 1000 counts/s. Flares with such high peak count rates are major flares. During the same time period about 2100 active regions passed across the solar disk, out of which only 153 were observed to produce major flares. (Some active regions are known to persist for several solar rotations, but at each passage new active region numbers are assigned and the estimate is based on active region numbers.) Out of these 153 active regions, 25 were observed to produce 5 or more major flares. Considering their high productivity of major flares, we may call these active regions super active regions. These 25 super active regions produced 209 major flares, accounting for 51% of all the major flares with identified active regions.

Bai, T.↗
NASA NTRS1971

Simulated space environment tests on cadmium sulfide solar cells

Cadmium sulfide (Cu2s - CdS) solar cells were tested under simulated space environmental conditions. Some cells were thermally cycled with illumination from a Xenon-arc solar simulator. A cycle was one hour of illumination followed immediately with one-half hour of darkness. In the light, the cells reached an equilibrium temperature of 60 C (333 K) and in the dark the cell temperature dropped to -120 C (153 K). Other cells were constantly illuminated with a Xenon-arc solar simulator. The equilibrium temperature of these cells was 55 C (328 K). The black vacuum chamber walls were cooled with liquid nitrogen to simulate a space heat sink. Chamber pressure was maintained at 0.000001 torr or less. Almost all of the solar cells tested degraded in power when exposed to a simulated space environment of either thermal cycling or constant illumination. The cells tested the longest were exposed to 10.050 thermal cycles.

Clarke, D. R.↗
NASA NTRS1972

Hot-gas-side heat transfer with and without film cooling on a simulated nuclear rocket thrust chamber using H2-O2

Heat-transfer coefficients were obtained on a thrust chamber which simulated the geometry of the NERVA nuclear rocket. The tests were performed with and without peripheral film cooling over a chamber pressure range of 1.05 million to 5.84 million newtons per square meter (153 to 847 psia). With no film cooling, the overall axial variation in the value of the correlation coefficient C of the equation (Stanton)* (Prandtl)* to the 0.7ths power = C(Reynolds)* to the -0.2ths power, where * indicates the reference enthalpy condition, was reduced 66 percent when the local diameter in the Reynolds number was replaced by the axial distance from the injector face. The average peak values of C were reduced 25 percent with 2 and 3.75 percent cooling and 50 percent with 7.5 percent cooling.

Quentmeyer, R. J.↗
NASA NTRS1972

Hypersonic and transonic buzz measurements on the lower pitch flap of the M2-F2 lifting entry configuration

Free-oscillation damping measurements at hypersonic and transonic Mach numbers are presented for the lower pitch flap of the M2-F2 reentry vehicle. For the flow and model conditions tested, the damping measurements indicate the absence of hypersonic buzz instability for flap rotation frequencies of 47.3 Hz, 153 Hz, and 360 Hz, the presence of transonic buzz for 47.3 Hz flap, and the absence of transonic buzz for a 115 Hz flap. There are not enough flap damping data for an error estimate based on repeatability, but a partial damping calibration is presented in which an analog computer simulation of random flap response for a known flap damping is fed into the autocorrelation computer and filter combination used for most of the damping measurements.

Warner, R. W.↗
NASA NTRS1972

Design study of shaft face seal with self-acting lift augmentation. 4: Force balance

A method for predicting the operating film thickness of self-acting seals is described. The analysis considers a 16.76-cm mean diameter seal that is typical of large gas turbines for aircraft. Four design points were selected to cover a wide range of operation for advanced engines. This operating range covered sliding speeds of 61 to 153 m/sec, sealed pressures of 45 to 217 N/sq cm abs, and gas temperatures of 311 to 977 K. The force balance analysis revealed that the seal operated without contact over the operating range with gas film thicknesses ranging between 0.00046 to 0.00119 cm, and with gas leakage rates between 0.01 to 0.39 scmm.

Ludwig, L. P.↗
NASA NTRS1973

Warm gas TVC design study

A warm gas thrust vector control system was studied to optimize the injection geometry for a specific engine configuration, and an injection valve was designed capable of meeting the base line requirements. To optimize injection geometry, studies were made to determine the performance effects of varying injection location, angle, port size, and port configuration. Having minimized the injection flow rate required, a warm gas valve was designed to handle the required flow. A direct drive hydraulic servovalve capable of operating with highly contaminated hydraulic fluid was designed. The valve is sized to flow 15 gpm at 3000 psia and the direct drive feature is capable of applying a spool force of 200 pounds. The baseline requirements are the development of 6 deg of thrust vector control utilizing 2000 F (total temperature) gas for 180 seconds on a 1.37 million pound thrust engine burning LOX and RP-1 at a chamber pressure of 250 psia with a 155 inch long conical nozzle having a 68 inch diameter throat and a 153 inch diameter exit.

Moorhead, S. B., Jr.↗
NASA NTRS1973

Need for a regional wind survey

Accurate measurements for the purpose of estimating wind energies are proposed in those regions of the USA where the greatest potentials exists. Preliminary wind characteristic calculations from weather station data are provided for the Southern Great Plains region; wind energies from 153 to 212 kW-hr/(ft squared-per year) for 1970 to 1972 are determined. It is concluded that a wind energy survey based on data compiled from weather service stations is feasible for determining the energy potential of a windpowered integrated energy network.

Nelson, V.↗