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At least 487 records · Page 27

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NASA NTRS1975

The location of the site of energy release in a solar X-ray subflare

A rapid sequence of high-resolution X-ray photographs was obtained by the S-054 X-ray Telescope Experiment on Skylab on 1973 September 1. During the course of this observation, photographs were obtained of a flarelike brightening in a simple, bipolar active region. Analysis reveals the following facts. The event had the form of a small, elongated bright feature whose narrowest dimension was less than seconds of arc. The brightness peak of the flarelike brightening was located within seconds of arc of the center of brightness of a preexisting loop structure that crossed the magnetic neutral line. This loop was observed to brighten gradually beginning approximately 10 minutes prior to the flarelike event. During the rise of the event, the 2-17 A X-ray brightness of the center of the subflare core rose by over a factor of 10 in a time period of 196 seconds or less.

Petrasso, R. D.↗

NASA NTRS1975

Curved branching crystals and differentiation in comb-layered rocks

An investigation is conducted concerning two common features of comb layered rocks. Attention is given to the curvature of oriented, elongate, branching crystals and the tendency to form highly differentiated layers. Crystallization studies of plagioclase show that some degree of supercooling is necessary to produce the skeletal, curved, and branching plagioclase crystal morphologies found in comb-layered rocks and that curved crystals can be grown without the presence of a directed stress.

Lofgren, G. E.↗

NASA NTRS1975

The structure and evolution of coronal holes

Soft X-ray observations of coronal holes are analyzed to determine the structure, temporal evolution, and rotational properties of those features as well as possible mechanisms which may account for their almost rigid rotational characteristics. It is shown that coronal holes are open features with a divergent magnetic-field configuration resulting from a particular large-scale magnetic-field topology. They are apparently formed when the successive emergence and dispersion of active-region fields produce a swath of unipolar field founded by fields of opposite polarity, and they die when large-scale field patterns emerge which significantly distort the original field configuration. Two types of holes are described (compact and elongated), and three possible rotation mechanisms are considered: a rigidly rotating subphotospheric phenomenon, a linking of high and low latitudes by closed field lines, and an interaction between moving coronal material and open field lines.

Timothy, A. F.↗

NASA NTRS1975

A model for Io's atmosphere and sodium cloud

Observations of the sodium D-line emissions associated with the Galilean satellite Io suggest that the emitting region has two components. The first is an atmosphere which extends 1000 km above Io's surface. This is a relatively dense region which is optically thick in the sodium D lines. The second component is a surrounding optically thin cloud spread out along Io's orbit to form part of a torus. No emission was detected during any of three eclipses observed, although Io's sodium emission was consistently present when Io was near orbital elongation. This indicates that resonant scattering is the principal emission mechanism in both components. For the atmosphere, measurements of the D-line intensity, D-2/D-1 ratio, and line width indicate a temperature of 500 to 1000 K and a sodium column abundance of 3 by 10 to the 13th power per sq cm. Upper limits to the abundance of Mg, K, Ca, and Li indicate a high sodium abundance ratio in the atmosphere. This may also be true for Io's surface if sputtering by energetic particles is the source of the atmosphere. The sodium cloud has been detected as far as 60 arcsec from Io in the orbital plane and at least 6 arcsec above and below this plane. The cloud can be sustained by atoms escaping from the critical level at the top of the atmosphere.

Macy, W., Jr.↗

NASA NTRS1975

A search for forward scattering of sunlight from lunar libration clouds

Data obtained with the white-light coronagraph on Skylab are analyzed to determine the radiance of forward scattered sunlight from particles in lunar libration regions. It is found that the libration regions could not be distinguished against the solar K + F coronal background, and upper limits are determined for the libration cloud radiance as well as density enhancements in the libration region. The actual spatial density enhancement is calculated on the basis of previous observations by Roach (1975). The radiance contrast of a possible model libration cloud is calculated with respect to the K- and F-corona/zodiacal-light background and is found to be a maximum in the vicinity of a solar elongation angle of the order of 30 deg.

Munro, R. H.↗

NASA NTRS1976

Metal structures with parallel pores

Four methods of fabricating metal plates having uniformly sized parallel pores are studied: elongate bundle, wind and sinter, extrude and sinter, and corrugate stack. Such plates are suitable for electrodes for electrochemical and fuel cells.

Sherfey, J. M.↗

NASA NTRS1975

Flight service evaluation of Kevlar-49/epoxy composite panels in wide-bodied commercial transport aircraft

Kevlar-49 fairing panels were inspected and found to be performing satisfactorily after two years flight service on an Eastern and an Air Canada L-1011. Six panels are on each aircraft including sandwich and solid laminate wing-body panels, and 300 F service aft engine fairings. Some of the panels were removed from the aircraft to permit inspection of inner surfaces and fastener hole conditions. Minor defects such as surface cracks due to impact damage, small delaminated areas, elongation and fraying of fastener holes, were noted. None of these defects were considered serious enough to warrant corrective action in the opinion of airline personnel. The defects are typical for the most part of defects noted on similar fiberglass parts.

Stone, R. H.↗

NASA NTRS1975

Skylab M551 metals melting experiment

The objectives of the M551 Metals Melting Experiment were to: (1) study behavior of molten metal, (2) characterize metals melted and solidified in the low gravity space environment compared to one-gravity of earth, and (3) determine feasibility of joining metals in space. The experiment used the electron beam (EB) and chamber of the M512 apparatus to make a dwell puddle and a melt in a rotating disc of varying thickness. Hence, the EB performed cut-through, full and partial penetration melts, in addition to a resolidified button. The three disc materials were aluminum 2219-T87, 304 stainless steel, and pure tantalum to provide a wide range of density and melting conditions. Observations to date include the proof that EB welding, cutting, and melting can be done successfully in low gravity. Earlier, some welding authorities had postulated that without gravity the EB would force the molten puddle out of contact. However, the experiment proved that surface tension forces predominate. From the viewpoint of cast-solidification, small, equiaxed grains in Skylab specimens compared to large, elongated grains in ground based specimens were observed. The former are thought to be associated with constitutional supercooling and nucleation where the latter are associated with dendritic solidification. In further support of the more equiaxed grain growth in Skylab, symmetric subgrain patterns were frequently observed where there was much less symmetry in ground based specimens.

Poorman, R. M.↗

NASA NTRS1975

Preliminary study of oxide-dispersion-strengthened B-1900 prepared by mechanical alloys

An experimental oxide dispersion strengthened (ODS) alloy based on the B-1900 composition was produced by the mechanical alloying process. Without optimization of the processing for the alloy or the alloy for the processing, recrystallization of the extruded product to large elongated grains was achieved. Materials having grain length-width ratios of 3 and 5.5 were tested in tension and stress-rupture. The ODS B-1900 exhibited tensile strength similar to that of cast B-1900. Its stress-rupture life was lower than that of cast B-1900 at 760 C. At 1095 C the ODS B-1900 with the higher grain length-width ratio (5.5) had stress-rupture life superior to that of cast B-1900. It was concluded that, with optimization, oxide dispersion strengthening of B-1900 and other complex cast nickel-base alloys has potential for improving high temperature properties over those of the cast alloy counterparts.

Glasgow, T. K.↗

NASA NTRS1975

Development of restraint material and tucked fabric joints

A study was conducted to evaluate and select a suitable restraint material for the exterior of space suits pressurized to 4.0 PSID for normal operations, and to develop and improve tucked fabric joints for motions associated with the human shoulder, elbow, knee, waist, hip, ankle, and wrist. The many attributes of the end items are summarized to include structural integrity, simplicity, low maintenance, lightweight, high durability, low elongation, full range mobility, long life, and resistance to degradation in the operational environment.

Mcmullen, J. M.↗

NASA NTRS1975

Hydrogeological investigations in the Pampa of Argentina

In large areas of the Argentinian Pampa the salinization of ground water creates water supply difficulties. Investigations of satellite imagery (Landsat-1 and Skylab) which were based on an extensive ground survey revealed that differences in the vegetation cover are closely related to depth and salinity of ground water. Narrow elongated depressions called bajos are often the only indication of fresh ground water. They can be easily detected on the imagery. Due to their high resolution, Skylab photos even allow a quantitative estimation of fresh ground water situated below the bajos. In general however Landsat-1 imagery sufficed for evaluation. In the area of the Rio Tercero a fossil drainage pattern was discovered and in Corrientes province, soil types could be discriminated and compared to the Soil Map of the World.

Kruck, W.↗

NASA NTRS1976

Fire resistant resilient foams

Primary program objectives were the formulation, screening, optimization and characterization of open-cell, fire resistant, low-smoke emitting, thermally stable, resilient polyimide foams suitable for seat cushions in commercial aircraft and spacecraft. Secondary program objectives were to obtain maximum improvement of the tension, elongation and tear characteristics of the foams, while maintaining the resiliency, thermal stability, low smoke emission and other desirable attributes of these materials.

Gagliani, J.↗

NASA NTRS1976

Mixing insert for foam dispensing apparatus

A device for mixing foam ingredients is described. The device comprises an arrangement of lands situated about a cylindrical elongated shaft-like member with each land having a slot. The slots of alternate lands are positioned 180 deg from each other so that as the ingredients flow through the mixing chamber they flow from adjacent one side of the housing to the other dividing as such passes around the shaft-like member.

Simpson, W. G.↗

NASA NTRS1975

Observation of soft X-rays from cosmic sources

A binary X-ray source, an extended extragalactic X-ray source and several nearby stars were surveyed for X-ray emission. The energy spectrum and time structure of X-ray flux from the binary source, Her X-l, was investigated in the range from 0.15 to 6 KeV. This source was observed at a binary phase of 0.18 with the system near elongation normal to the line of sight. Intense pulsations were observed in optical emission lines near this binary phase. The spectrum and angular distribution of X-ray emission from the X-ray source in the Virgo Cluster of Galaxies, near M 87, was also observed. In addition, the stars Alpha Leo, Zeta Her, and Epsilon Vir were investigated. Epsilon Aur and Alpha Aur were also scanned. These stars were studied since there is increasing evidence that such objects may be transient sources of soft X-rays.

Catura, R. C.↗

NASA NTRS1976

Solar energy trap

An apparatus is described for trapping solar energy for heating a fluid that could be subsequently used in turbines and similar devices. The apparatus includes an elongated vertical light pipe having an open end through which the visible spectrum of electromagnetic radiation from the sun passes to strike a tubular absorber. The light pipe has a coated interior surface of a low absorptivity and a high reflectivity at the visible wavelengths and a high absorptivity/emissivity ratio at infrared wavelengths. The tubular absorber has a coating on the surface for absorbing visible wavelengths to heat the fluid passing through. Infrared wave lengths are radiated from the tubular absorber back into the light pipe for heating fluid passing through a tubular coil wound around it.

Brantley, L. W., Jr.↗

NASA NTRS1976

Lineaments on Skylab photographs: Detection, mapping, and hydrologic significance in central Tennessee

The author has identified the following significant results. Lineaments were detected on Skylab photographs by stereo viewing, projection viewing, and composite viewing. Sixty-nine percent more lineaments were found by stereo viewing than by projection, but segments of projection lineaments are longer; total length of lineaments found by these two methods is nearly the same. Most Skylab lineaments consist of topographic depression: stream channel alinements, straight valley walls, elongated swales, and belts where sinkholes are abundant. Most of the remainder are vegetation alinements. Lineaments are most common in dissected areas having a thin soil cover. Results of test drilling show: (1) the median yield of test wells on Skylab lineaments is about six times the median yield of all existing wells; (2) three out of seven wells on Skylab lineaments yield more than 6.3 1/s (110 gal/min): (3) low yields are possible on lineaments as well as in other favorable locations; and (4) the largest well yields can be obtained at well locations of Skylab lineaments that also are favorably located with respect to topography and geologic structure, and are in the vicinity of wells with large yields.

Moore, G. K.↗

NASA NTRS1976

M551 metals melting experiment

The Metals Melting Skylab Experiment consisted of selectively melting, in sequence, three rotating discs made of aluminum alloy, stainless steel, and tantalum alloy. For comparison, three other discs of the same three materials were similarly melted or welded on the ground. The power source of the melting was an electron beam unit. Results are presented which support the concept that the major difference between ground base and Skylab samples (i.e., large elongated grains in ground base samples versus nearly equiaxed and equal sized grains in Skylab samples) can be explained on the basis of constitutional supercooling, and not on the basis of surface phenomena. Microstructural observations on the weld samples and present explanations for some of these observations are examined. In particular, ripples and their implications to weld solidification were studied. Evidence of pronounced copper segregation in the Skylab A1 weld samples, and the tantalum samples studied, indicates a weld microhardness (and hence strength) that is uniformly higher than the ground base results, which is in agreement with previous predictions. Photographs are shown of the microstructure of the various alloys.

Li, C. H.↗

NASA NTRS1975

Rutgers zodiacal light experiment on OSO-6

A detector was placed in a slowly spinning wheel on OSO-6 whose axis was perpendicular to the line drawn to the sun, to measure the surface brightness and polarization at all elongations from the immediate neighborhood of the sun to the anti-solar point. Different wavelength settings and polarizations were calculated from the known order of magnitude brightness of the zodiacal light. The measuring sequence was arranged to give longer integration times for the regions of lower surface brightness. Three types of analysis to which the data on OSO-6 were subjected are outlined; (1) photometry, (2) colorimetry and (3) polarimetry.

Carroll, B.↗