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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1939

Hydrodynamic and Aerodynamic Tests of a Family of Models of Seaplane Floats with Varying Angles of Dead Rise - N.A.C.A. Models 57-A, 57-B, and 57-C

Three models of V-bottom floats for twin-float seaplanes (N.A.C.A. models 57-A, 57-B, and 57-C) having angles of dead rise of 20 degrees, 25 degrees, and thirty degrees, respectively, were tested in the N.A.C.A. tank and in the N.A.C.A. 7- by 10-foot wind tunnel. Within the range investigated, the effect of angle of dead rise on water resistance was found to be negligible at speeds up to and including the hump speed, and water resistance was found to increase with angle of dead rise at planing speeds. The height of the spray at the hump speed decreased with increase in angle of dead rise and the aerodynamic drag increased with dead rise. Lengthening the forebody of model 57-B decreased the water resistance and the spray at speeds below the hump speed. Spray strips provided an effective means for the control of spray with the straight V sections used in the series but considerably increased the aerodynamic drag. Charts for the determination of the water resistance and the static properties of the model with 25 degrees dead rise and for the aerodynamic drag of all the models are included for use in design.

Parkinson, John B↗
NASA NTRS2021

The Peculiar Nebula Simeis 57: II. Distance, Nature and Excitation

Simeis 57 (HS 191) is an optically bright nebula in the Cygnus X region with a peculiar appearance that suggests an outflow from a rotating source. Newly obtained observations and archival data reveal Simeis 57 as a low-density (ne∼100cm−3) nebula with an east-to-west excitation gradient. The extinction of the nebula isAV≤2mag. The nebula is recognizable but not prominent in mid-and far-infrared images. In its direction, half a dozen small CO clouds have been identified at VLSR= +5km s−1. One of these coincides with both the optical nebula and a second CO cloud at the nebular velocity- VLSR≈ −10km−1. No luminous stars are embedded in these molecular clouds, nor are any obscured by them and no sufficiently luminous stars are found in the immediate vicinity of the nebula. Instead, all available data points to the evolved star HD 193793 = WR 140 (an O4-5 supergiant and WC7 Wolf–Rayet binary)as the source of excitation, notwithstanding its large separation of 50′, about 25 pc at the stellar distance of 1.7 kpc. Simeis 57 appears to be a part of a larger structure surrounding the HI void centered on HD 193793

L H T Oudshoorn↗
NASA NTRS1986

The exciting star of HH 57

The first spectral classification for the exciting star of HH 57 is provided. The star is an F8 III and suffers about 5 mag of visual extinction, far greater than that toward the HH 57A knot, only a few arcseconds away. This difference supports the previous identification of a flattened geometry for the circumstellar dust around this star. Using IRAS photometry, a distance of 940 pc to HH 57 is determined by bolometrically matching the observed luminosity of the star to those of FU Ori and V1057 Cyg.

Cohen, M.↗
NASA NTRS2020

Simulating the Benesov Bolide Flowfield and Spectrum at Altitudes of 47 and 57 km

This paper develops a computational fluid dynamics capability for simulating the radiative emission from a meteor shock-layer and wake to an external observer. The developed capability includes the impact of radiation and ablation on the meteor flowfield, where coupled radiation accounts for the impact of radiation on the flowfield energy equations and coupled ablation accounts for the injection of ablation species from the meteoroid surface into the ow. This capability includes updated flowfield chemistry and nonequilibrium radiation models, which are compiled from the literature. To provide a level of validation for this capability, the Benesov spectral measurements are considered. Although the meteoroid was likely fragmented at the 47 and 57 km altitudes considered, and the measurement uncertainty is roughly ±50%, these measurements represent the best available spectral measurements for a relatively large (meter-class) bolide. To determine the equivalent meteoroid diameter to simulate, the continuum component of the spectrum in the 570 to 610 nm range is considered. This range is dominated by air emission from the high pressure and temperature shock-layer in front of the meteoroid, which is simulated with a relatively small uncertainty (because of the abundance of relevant shock tube measurements) and sensitive to the equivalent meteoroid diameter. This allows an equivalent diameter between 0.62 to 0.9 m to be determined, based on comparisons between measurements and simulations in the 570 to 610 nm range. The range of equivalent diameters is due to the various meteoroid geometries considered, where increasing the bluntness decreases the required diameter. Applying these diameters to simulations at 47 and 57 km results in simulated spectra that compare within 30% of the measured values, considering the wavelength integrated values between 400 and 650 nm. This agreement is well within the estimated measurement uncertainty of ±50%. All major spectral features are captured by the simulations. This agreement provides a level of validation for the developed model that has not been previously available.

Luminous efficiency↗
NASA NTRS1980

Chemical classification of iron meteorites. IX - A new group /IIF/, revision of IAB and IIICD, and data on 57 additional irons

The paper discusses the chemical classification of independent iron meteorites which include 57 meteorites based on structural observations and concentrations of Ni, Ga, Ge, and Ir. Instrumental neutron activation analysis indicates that five previously studied irons with very high Ge/Ga ratios are compositionally closely related and can be gathered together as group IIF; a previously unstudied iron, Dehesa, has the highest Ge/Ga ratios known in an iron meteorite, a ratio 18 times higher than that in CI chondrites. In terms of Ge/Ga ratios and other properties, group IIF shows genetic links to the Eagle station pallasites and CO/CV chondrites. The iron with the highest Ni concentration, Oktibbeha County, is a member of group IAB, and it extends the concentration ranges of all elements in this nonmagnetic group.

Kracher, A.↗
NASA NTRS1993

Optical studies of interstellar material in low density regions of the Galaxy. I - A survey of interstellar Na I and Ca II absorption toward 57 distant stars

We present high-resolution spectra of the Na I D and Ca II K lines toward 57 late-O and early-B stars along extended (d greater than 1 kpc) low-density paths through the Milky Way disk and halo. The sight lines preferentially sample diffuse gas in the interstellar medium (ISM) along interarm, Galactic center, and high latitude directions. We measure equivalent widths, apparent column densities, and absorption component structure. The Ca II to Na I ratios presented as a function of velocity for each sight line exhibit variations due to elemental depletion, ionization, and density enhancements. Absorption along high latitude sight lines is kinematically simpler than it is along interarm and Galactic center sight lines. Galactic rotation noticeably broadens the absorption profiles of distant stars located in these latter directions. Along several sight lines, we see Ca II absorption at velocities corresponding to large distances (/z/ about 1 kpc) from the Galactic plane. The effects of differences in the Ca II and Na I scale heights and nonzero velocity dispersions are readily apparent in the data. Brief notes are given for several sight lines with interesting absorption properties.

Sembach, K. R.↗
NASA NTRS1994

Deep UBVRI photometric calibration of high-latitude fields: SA 57 (1307+30) and Hercules (1720+50)

We present CCD photometric calibration sequences in the magnitude range V = 17-22 for two fields at high Galactic latitude: SA 57 (at the North Galactic Pole) and Hercules (l = 77, b = 35). Photometry to a precision of about 0.02 mag at V = 20 and, in general, better than 0.10 mag at V = 22 was obtained in the Johnson UBV as well as the Kron-Cousins R and I bands. These data are suitable for setting magnitude zero-points in catalogues of faint stars, galaxies, and QSOs, and we apply them to our own photographic catalogs in these two fields. We also note a significant deviation in the (V-R, R-I) color-color diagram for the locus of faint (V is greater than 20) M dwarfs compared to the locus provided by much brighter M dwarfs. This deviation may indicate differences in spectral properties between Population I and older populations of late dwarfs; however we do not discount the possibility that this locus for the faint stars, which appears as a saturation in V-R color with increasing R-I color, is the result of systematic photometric error.

Majewski, S. R.↗
NASA NTRS1974

In-line task 57: Component evaluation

Design analysis tests were performed on selected power switching components to determine the possible applicability of off-the-shelf hardware to space shuttles. Various characteristics were also evaluated in those devices to determine the most desirable properties for the space shuttle.

Boykin, J. C.↗
NASA NTRS1976

Results of an air data probe investigation utilizing a 0.10 scale orbiter forebody (model 57-0) in the Ames Research Center 14-foot wind tunnel (OA220)

Results are presented of a 0.10 scale orbiter forebody test with left and right mounted air data probes (ADP) as well as a flight test probe (nose boom). Left and right ADP data were obtained at Mach numbers of .3, .4, .5, .6, .7, .8, .85, .9, .95, .98, 1.05 and 1.1 through a Reynolds number range of 1.3 to 4.4 million. Nose boom data were obtained at Mach numbers of .3, .4, .5, .6, .7, .9 and .98.

Esparza, V.↗
NASA NTRS1988

Computer-aided design analysis of 57-mm, angular-contact, cryogenic turbopump bearings

The Space Shuttle main engine high-pressure oxygen turbopumps have not experienced the sevice life required of them. This insufficiency has been due in part to the shortened life of the bearings. To improve the life of the existing turbopump bearings, an effort is under way to investigate bearing modifications that could be retrofitted into the present bearing cavity. Several bearing parameters were optimized using the computer program SHABERTH, which performs a thermomechanical simulation of a load support system. The computer analysis showed that improved bearing performance is feasible if low friction coefficients can be attained. Bearing geometries were optimized considering heat generation, equilibrium temperatures, and relative life. Thermal gradients through the bearings were found to be lower with liquid lubrication than with solid film lubrication, and a liquid oxygen coolant flowrate of approximately 4.0 kg/s was found to be optimal. This paper describes the analytical modeling used to determine these feasible modifications to improve bearing performance.

Armstrong, Elizabeth S.↗