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At least 559 records · Page 31

The utilization of Habrobracon and artemia as experimental materials in bioastronautic studies

In the reproductive performance of female braconids striking contrasts were revealed between the results from the actual biosatellite flight and those from experiments when the recovered vehicle was subjected to the forces of simulated launching and recovery. Second week decreases in egg production due to the radiation damage of cells in mitosis were minimized for the females irradiated during space flight. It was demonstrated that females irradiated for two days during orbital flight laid as many eggs during the second week as the unirradiated ground-based controls. After the 10th day their oviposition records exceeded control values. The hatchability of eggs deposited by Biosatellite II females was excellent. Explanations were sought for the space flight's cancellation of the characteristic radiation-induced decrease in egg production, and for the exceptionally good hatchability of eggs derived from most of the cell types in the irradiated ovarioles. Eggs from only two classes of cells showed enhanced embryonic lethality: those poised in meiotic metaphase during their mother's orbital flight, and those from oocytes beginning vitellogenesis.

Grosch, D. S.↗

Computer program to assess impact of fatigue and fracture criteria on weight and cost of transport aircraft

A preliminary design analysis tool for rapidly performing trade-off studies involving fatigue, fracture, static strength, weight, and cost is presented. Analysis subprograms were developed for fatigue life, crack growth life, and residual strength; and linked to a structural synthesis module which in turn was integrated into a computer program. The part definition module of a cost and weight analysis program was expanded to be compatible with the upgraded structural synthesis capability. The resultant vehicle design and evaluation program is named VDEP-2. It is an accurate and useful tool for estimating purposes at the preliminary design stage of airframe development. A sample case along with an explanation of program applications and input preparation is presented.

Tanner, C. J.↗

Measurement of the fluxes of galactic cosmic ray H-2 and He-3 in 1972 - 1973

If a nearby source of low-energy helium is present, which has traversed a relatively small amount of matter and thus has not caused the production of a significant amount of H-2 or He-3, then these abundance ratios will be suppressed, particularly at low energies. This seems to be the most likely explanation for low ratios.

Teegarden, B. J.↗

Investigation of immiscible systems and potential applications

The droplet coalescence kinetics at 0 g and 1 g were considered for two systems which contained liquid droplets in a host liquid. One of these (Al-In) typified a system containing a liquid phase miscibility gap and the order (oil-water) a mixture of two essentially insoluble liquids. A number of coalescence mechanisms potentially prominent at low g in this system were analyzed and explanations are presented for the observed unusual stability of the emulsion. Ground base experiments were conducted on the coalescence of In droplets in and Al-In alloy during cooling through the miscibility gap at different cooling rates. These were in qualitative agreement with the computer simulation. Potential applications for systems with liquid phase miscibility gaps were explored. Possibilities included superconductors, electrical contact materials, superplastic materials, catalysts, magnetic materials, and others. The role of space processing in their production was also analyzed.

Markworth, A. J.↗

Pre-resonance Raman spectra of some simple gases

The pre-resonance Raman spectra of SO2, N2O, and H2S were investigated using the 4880 A, 4727 A, and 4579 A lines of the argon ion laser. Although these molecules have electronic absorption bands in the near ultraviolet, none exhibit any pre-resonance enhancement within our experimental error of + or - 10%. Possible explanations taking into account the current theories for resonance Raman are discussed.

Low, P. W.↗

Vortex shedding from a blunt trailing edge with equal and unequal external mean velocities

A flow visualization study showed that strong Karman vortices are developed behind the blunt trailing edge of a plate when the free stream velocities over both surfaces are equal. These vortices tend to disappear when the surface velocities are unequal. This observation provided an explanation for the occurrence and disappearance of the lip noise often present in coaxial jets. Vortex formation and lip noise occurred at a Strouhal number of about 0.2 based on the lip thickness and the average of the external steady-state velocities. Results from theoretical calculations of the vortex formation, based on an inviscid, incompressible analysis of the motion of point vortices, were in good agreement with the experimental observations.

Brinich, P. F.↗

The interplanetary acceleration of energetic nucleons

Co-rotating proton and electron streams are the dominant type of low-energy (0.1-10 MeV/nucleon) particle event observed at 1 A.U. The radial dependence of these events was studied between 1 and 4.6 A.U. using essentially identical low-energy detector systems on IMP 7, Pioneer 10 and Pioneer 11. It was expected that at a given energy, the intensity of these streams would decrease rapidly with heliocentric distance due to the effects of interplanetary adiabatic deceleration. Instead it was found that from event to event the intensity either remains roughly constant or increases significantly (more than an order of magnitude) between 1 and 3 A.U. It appears that interplanetary acceleration processes are the most plausible explanation. Several possible acceleration models are explored.

Mcdonald, F. B.↗

A finite-difference program for stresses in anisotropic, layered plates in bending

The interlaminar stresses induced in a layered laminate that is bent into a cylindrical surface are studied. The laminate is modeled as a continuum, and the resulting elasticity equations are solved using the finite difference method. The report sets forth the mathematical framework, presents some preliminary results, and provides a listing and explanation of the computer program. Significant among the results are apparent symmetry relationships that will reduce the numerical size of certain problems and an interlaminar stress behavior having a sharp rise at the free edges.

Salamon, N. J.↗

Emotionality in response to aircraft noise: A report of development work

A literature search and pilot study conducted to investigate the topic of emotional response to aircraft noise are described. A Tell-A-Story Technique was developed for use in the pilot study which required respondents to make up stories for a series of aircraft-related and non-aircraft-related pictures. A content analysis of these stories was made. The major finding was that response patterns varied among three groups of respondents - those currently living near airports, those who had lived near airports in the past, and those who had never lived near airports. Negative emotional feelings toward aircraft were greatest among respondents who had lived near airports in the past but no longer did. A possible explanation offered for this finding was that people currently living near airports might adapt to the situation by denying some of their negative feelings, which they might feel more free to express after they had moved away from the situation. Other techniques used in the pilot study are also described, including group interviews and a word association task.

Klaus, P. A.↗

Physics of compact nonthermal sources. III - Energetic considerations

The energy content of the compact incoherent electron-synchrotron sources 3C 84, 3C 120, 3C 273, 3C 279, 3C 454.3, CTA 102, 3C 446, PKS 2134+004, VRO 42.22.01 and OJ 287 is calculated on the assumption that the low-frequency turnovers in the radio spectrum are due to self-absorption and that the electron distribution is isotropic. The dependence of the source parameters on various modifications of the standard assumptions is determined. These involve relativistic motions, alternate explanations for the low-frequency turnover, proton-synchrotron radiation, and distance to the source. The canonical interpretation is found to be accurate in many respects; some of the difficulties and ways of dealing with them are discussed in detail.

Burbidge, G. R.↗

Significance of semiannual waves in the mesospheric zonal wind and evidence of influence by the geomagnetic field

The recently described polar semiannual oscillations in zonal wind can explain midwinter weakening of the polar winter vortex and the relatively short stratospheric and mesospheric summer easterlies. This explanation implies that stratospheric sudden warmings may be caused or affected by the polar semiannual oscillation. Two potential physical mechanisms (not mutually exclusive) for the oscillation are presented: planetary wave action and changes in the radiation field. Radiation absorption changes are suggested to result from changes in ozone concentration during magnetic storms. Contours of amplitude of both the polar and tropical semiannual wind oscillations are more nearly congruent with geomagnetic than with geographic latitude.

Belmont, A. D.↗

Mixed mode stress field effect in adhesive fracture

Numerical or analytical analyses were performed on seven different test specimens including blister test, 90-degree peel test, torsion test, and various cone tests. These specimens are in general subjected to complex stress fields having various amounts of Mode I, Mode II, and Mode III loads. The specimens were then constructed using polymethyl methacrylate for the adherends and a transparent polyurethane elastomer (Solithane 113) for the adhesive. This combination permitted direct observation of the bondline as load was applied. Although initial debonds as well as bond end termination singularities were present in all specimens, in some cases the debond did not initiate at the singularity points as would normally have been expected. An explanation for this behavior is presented, as well as a comparison of loading mode effect on those specimens for which the debond did propagate from a bond terminus singular point.

Anderson, G. P.↗

Possible influence of comets on the chemical evolution of the galaxy

It has been suggested by Cameron (1973) that a cloud of comets containing a mass of condensable elements, comparable to the mass of such elements in the sun, formed on the outskirts of the solar system. If the formation of such comet clouds is a general feature of star formation, they constitute a significant sink of elements heavier than helium. It is shown here that this process provides a possible explanation for the very slow rate at which the mean metal abundance of disk stars has increased during the lifetime of the Galaxy.

Tinsley, B. M.↗

Spacecraft charging at high altitudes - The SCATHA satellite program

Satellites at synchronous altitude exhibit unexplained behavior in the operation of electronic circuits and in the performance of thermal controls. A possible explanation for this behavior is the fact that satellites can be charged to large negative voltages by energetic electrons in the space environment. A space measurements program entitled SCATHA has been formulated to determine the characteristics of the charging process, to measure the response of the satellite when charging occurs, and to evaluate the utility of various corrective techniques which can minimize differential charging on the satellite. The instrumentation will measure charging levels and rates of twenty samples of satellite materials, some of which will be modified to prevent buildup of electrostatic charge. The electromagnetic interference background on the satellite will be measured for comparison with MIL STD 461, Electromagnetic Interference Characteristics Requirements for Equipment.

Mcpherson, D. A.↗

The significance of observed rotational magnetic hysteresis in lunar samples

Rotational magnetic hysteresis curves for lunar soils 10084, 12070, and 14259, and rock 14053 have been published. There is no adequate explanation to date for the observed large hysteresis at high fields. Lunar rock magnetism researchers consider fine particle iron to be the primary source of stable magnetic remanence in lunar samples. Iron has cubic anisotropy with added shape anisotropy for extreme particle shapes. The observed high-field hysteresis must have its source in uniaxial or unidirectional anisotropy. This implies the existence of minerals with uniaxial anisotropy or exchange-coupled spin states. Therefore, the source of this observed high-field hysteresis must be identified and understood before serious paleointensity studies are made. It is probable that the exchange-coupled spin states and/or the source of uniaxial anisotropy responsible for the high-field hysteresis might be influenced by the lunar surface diurnal temperature cycling. The possible sources of high-field hysteresis in lunar samples are presented and considered.

Wasilewski, P.↗

The spectrum of Mars in the region 1800-3200 per cm

During the 1971 opposition of Mars, new infrared spectra covering the region 1800-3200 per cm were taken at a resolution of 0.095 per cm using a Connes'-type Fourier spectrometer on a 2.7 m telescope. No new trace constituents have, as yet, been found in the spectra, but several previously unobserved combination of isotopic bands of CO2 are visible. It has also been found possible to fit fairly well defined kinetic temperatures and Bond albedos to the data. The kinetic temperatures have been determined by a new technique. It is found that the albedo at 33 deg phase, which was determined a few days after the onset of the great dust storm of 1971, was significantly higher than for the clear atmosphere. The explanation for this phenomenon must await detailed radiative transfer calculations for a dust-laden atmosphere.

Beer, R.↗

Rationale for NASA Planetary Exploration Program

The Planetary Mission Model, NASA's program of future solar system exploration for the years 1973-1990, is presented. The model is based on a continuation of the balanced exploration philosophy, tempered by a conception of the realities of technology availability and fiscal constraints. It envisions the continued use of existing spacecraft technology (i.e., Mariner, Viking, and Pioneer) with only evolutionary changes, but with the introduction of atmospheric probe technology in the late 70's. The Titan/Centaur vehicle would be in use through 1980, and solar-electric propulsion (SEP) capability would be introduced in about 1979. Beyond 1980, shuttle capability is assumed. A brief explanation of the rationale behind the sequences at the following targets is presented: Mercury, Venus, Mars, the outer planets, and comets and asteroids.

Rasool, I.↗