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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 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

A low-frequency radio survey of the planets with RAE 2

Over one thousand occultations of each planet in the solar system have occurred during the period from mid-1973 through mid-1976 as seen from the lunar orbiting Radio Astronomy Explorer 2 (RAE 2) spacecraft. These occultations have been examined for evidence of planetary radio emissions in the 0.025-13.1 MHz band. Only Jupiter and the earth have given positive results. Lack of detection of emission from the other planets can mean that either they do not emit radio noise in this band or the flux level of their emissions and/or its occurrence rate are too low to be detected by RAE 2.

Kaiser, M. L.↗
NASA NTRS1977

A high-resolution infrared spectrum of IRC +10216

The IR-emitting core and shell of IRC +10216 are investigated using a high-resolution spectrum covering the wavelength interval between 3 and 5 microns. Line identifications made or confirmed include those due to (C-12)(O-16), (C-13)(O-16), (C-12)(O-17), and (C-12)(O-18). A mean heliocentric velocity of about -32 km/s is obtained from the 42 least blended (C-12)O and (C-13)O lines, and the following isotopic abundance ratios are derived by comparing equivalent widths of the observed lines: C-12/C-13, C-12/C-14, O-16/O-17, and O-17/O-18. The structure of the expanding gas shell is examined, an explanation is offered for the lack of P Cygni profiles in the spectrum, and an unsuccessful search for other molecules is briefly discussed. It is concluded that a low C-12/C-13 ratio is not necessarily a signature of a carbon star.

Barnes, T. G.↗
NASA NTRS1976

Basic aspects of superalloy design for crack growth resistance

It is pointed out that the major difficulty concerning an understanding of the flaw growth resistance properties of superalloys is related to the lack of basic theories. An attempt is made to develop these theories, taking into account their use for the identification of tentative alloy design guidelines for flaw growth resistance. A brief review of the fatigue crack growth literature is provided. Attention is given to continuous fatigue crack growth theory, threshold fatigue crack growth, planar slip superalloy fatigue crack growth, and aspects of creep crack growth resistance.

Tien, J. K.↗
NASA NTRS1976

Considerations on data compression of synthetic aperture radar images

This paper describes some analytical results relative to the effectiveness of applying data compression techniques for efficient transmission of synthetic aperture radar (SAR) signals and images. A Rayleigh target model is assumed in the analysis. It is also assumed that all surface reflectivity information is of interest and needs to be transmitted. Spectral characteristics of radar echo signals and processed images are analyzed. Analytical results generally indicate that due to the lack of high spatial correlation in the Rayleigh distributed radar surface reflectivity, application of data compression to SAR signals and images under the square difference fidelity criterion may be less effective than its application to images obtained using incoherent illumination. On the other hand, if certain random variations in radar images are considered as undesirable, substantial compression ratio may be achieved by removing such variations.

Wu, C.↗
NASA NTRS1977

Limitations to growth of microorganisms on Uranus, Neptune, and Titan

Reappraisal of the probabilistic policy toward planetary contamination by terrestrial microorganisms carried aboard space probes is suggested on the grounds that assignment of numerical probabilities to qualitatively unknown phenomena, as expressed in Phillips's (1974) formulation of the probability of contamination, is inappropriate. As an alternative, it is proposed that fundamental knowledge of the interacting nature of life on earth, interrelations between terrestrial organisms, and continuing effects of these organisms on earth's atmosphere and surface should guide the formulation of a sounder scientific quarantine policy. Simple conservative atmospheric models most favorable for life on Uranus and Neptune are examined. It is concluded that terrestrial microorganisms will not grow on either planet due to limitations of liquid water, atmospheric convection to lethal depths, the absence of energy sources and nutrients, the presence of ammonia and hydrogen, insufficient concentrations of biologically necessary ions, and the lack of a surface. The likelihood of terrestrial microorganism growth on Titan is found to be vanishingly small.

Margulis, L.↗
NASA NTRS1977

Searching for extraterrestrial civilizations

Three interrelated assumptions are critically examined in an attempt to outline a productive strategy for a search for extraterrestrial intelligence. Questions concerning the feasibility of interstellar travel are investigated. It is concluded that the probability of interstellar travel is high enough that, given a modest number of advanced civilizations, at least one of them will engage in interstellar voyages and colonize the galaxy. Assuming, however, that technological civilizations are rare the galaxy would be essentially unpopulated. Attention is given to the present lack of contact with extraterrestrial beings and frequencies for interstellar beacons.

Kuiper, T. B. H.↗
NASA NTRS1976

The excess fission xenon problem in lunar samples

This paper presents noble-gas (neon, krypton, and xenon) data obtained in stepwise heating of five lunar breccias: 14063, 14082, 15205, 15405, and 15445. These data are discussed in terms of spallation gas content, cosmic-ray exposure ages, and content of fission xenon. None of these samples is rich in solar-wind gases, and none contains more fission xenon than would be expected for in situ fission of U-238 and Pu-244. The essential features of the excess-fission-xenon phenomenon seen in several Apollo 14 samples are reviewed, as are models which might account for this phenomenon and criteria by which these models may be evaluated. The lack of excess fission xenon in 14063 and 14082 eliminates models relying on microscale xenon redistribution. A model is proposed in which the excess fission xenon originates in local material and percolates through and is adsorbed on regolith material.

Drozd, R. J.↗
NASA NTRS1976

Fibre evaluation for spacecraft cleaning

The employment of vacuum brushes utilizing sable tail hair for the physical removal of particulates from spacecraft surfaces has become problematical in connection with a lack of compatibility of the bristle with sterilization and biological decontamination procedures required for spacecraft cleaning. An investigation was, therefore, conducted to find a suitable fiber which can replace sable bristle. Felor fiber was found to have the best properties for use in a motorized cleaning brush.

Jensen, W. M.↗
NASA NTRS1977

Apollo 17 KREEPy basalt - A rock type intermediate between mare and KREEP basalts

The Apollo 17 KREEPy basalt is a unique lunar volcanic rock, observed only as clasts in the light friable breccia matrix (72275) of Boulder 1, Station 2 at Taurus-Littrow. Its status as a volcanic rock is confirmed by the absence of any meteoritic contamination, a lack of cognate inclusions or xenocrystal material, and low Ni contents in metal grains. The basalt was extruded 4.01 + or - 0.04 b.y. ago, approximately contemporaneously with the high-alumina mare basalts at Fra Mauro; shortly afterwards it was disrupted, probably by the Serenitatis impact, and its fragments emplaced in the South Massif. The basalt, which is quartz-normative and aluminous, is chemically and mineralogically intermediate between the Apollo 15 KREEP basalts and the high-alumina mare basalts in most respects. It consists mainly of plagioclase and pigeonitic pyroxene in approximately equal amounts, and 10-30% of mesostatis.

Ryder, G.↗
NASA NTRS1977

Auroral vector electric field and particle comparisons. I - Preliminary convection topology

Data obtained by Polar 3, launched from northern Norway January 27, 1974, are interpreted. The rocket, which traversed nearly 3 deg of latitude, crossed over a stable IBC II auroral arc in the positive bay region and continued north to a convection boundary which has been identified as the Harang discontinuity. Measurements of the complete electric field vector, of energetic electrons, and of auroral emissions were used to study the convection topology in the premagnetic midnight region. The inverted V nature of the electron precipitations at the convection boundary, compared with the lack of such structure over the arc which was within the positive bay region, is thought to indicate that auroral arcs are likely to be associated with inverted V type precipitation only at or poleward of convection boundaries and their eddy structures.

Maynard, N. C.↗
NASA NTRS1977

Mining the Apollo and Amor asteroids

Earth-approaching asteroids could provide raw materials for space manufacturing. For certain asteroids the total energy per unit mass for the transfer of asteroidal resources to a manufacturing site in high earth orbit is comparable to that for lunar materials. For logistical reasons the cost may be many times less. Optical studies suggest that these asteroids have compositions corresponding to those of carbonaceous and ordinary chondrites, with some containing large quantities of iron and nickel; other are thought to contain carbon, nitrogen, and hydrogen, elements that appear to be lacking on the moon. The prospect that several new candidate asteroids will be discovered over the next few years increases the likelihood that a variety of asteroidal resource materials can be retrieved on low-energy missions.

Oleary, B.↗
NASA NTRS1977

What the exploration of Mars tells us about earth

Data obtained from the Viking missions to Mars have lead to comparisons between characteristics of that planet and certain aspects of earth. Topics discussed include: thermal and compositional evolution of the planets' interiors, the origin of their atmospheres, the history of their fluid environments, the evolution of organic material, and climatic changes. Examples of convective and magmatic activity on the crusts of the two planets are contrasted; outgassing evidenced in the crustal zones is related to the evolution of atmosphere. Analysis of experimental degassing of meteorites provides further insight into the origin and composition of planetary atmospheres. Attributes of the Martian surface, which is apparently an oxidizing rather than reducing medium, are reviewed, and explanations proposed to account for its lack of an organic richness comparable to that found on earth. Data on long-range climatic changes on earth, related to precession, obliquity, and eccentricity of the planet, may contribute to understanding of the Martian polar caps, and vice versa.

Rasool, S. I.↗
NASA NTRS1977

Seismic energy transmission in an intensively scattering environment

In order to account for some special features of lunar seismograms, namely, the gradual build-up of the signal, the extremely prolonged tail, and the lack of apparent coherence among three orthogonal components of ground motion, a statistical approach is proposed for describing transmission of seismic energy through a medium in which strong scattering takes place. A seismic diffusion theory is presented for a medium with randomly distributed scatterers of a given size distribution. A solution of the resulting diffusion equation for an impulsive energy source gives a curve which fairly closely reproduces the envelope of typical lunar impact seismograms. Since the model is based on constant diffusivity, long-range transmission will require a combination of diffusion and wave propagation treatments for accurate description.

Nakamura, Y.↗
NASA NTRS1977

Double-discharge stabilization of supersonic CO laser mixtures

Experiments have been conducted to study the applicability of a CW double-discharge stabilization scheme under conditions appropriate for high-energy lasers in supersonic flows. Steady arc-free volume discharges have been produced in a Mach 3 supersonic-flow test cavity using an auxiliary discharge to stabilize the main discharge at low-current densities in N2 and He/CO mixtures. A significant result is the lack of observed plasma E/N changes in response to auxiliary-discharge current changes. Also, where glow discharges were obtained, the energy loading achieved was less than the threshold required for laser operation.

Srinivasan, G.↗
NASA NTRS1977

The effects of the geosynchronous energetic particle radiation environment on spacecraft charging phenomena

The energetic electron environment at the geosynchronous orbit is responsible for a variety of adverse charging effects on spacecraft components. The most serious of these is the degradation and failure of a complementary-metal-oxide-semiconductor (CMOS) electronic components as a result of internal charge-buildup induced by the energetic electrons. Efforts to accurately determine the expected lifetime of these components in this orbit are hampered by the lack of detailed knowledge of the electron spectrum and intensity, particularly of the more penetrating energies greater than 1.5 MeV. This problem is illustrated through the calculation of the dose received by a CMOS device from the energetic electrons and associated bremsstrahlung as a function of aluminum shielding thickness using the NASA AE-6 and the Aerospace measured electron environments. Two computational codes which were found to be in good agreement were used to perform the calculations. For a given shielding thickness the dose received with the two radiation environments differ by as much as a factor of seven with a corresponding variation in lifetime of the CMOS.

Reagan, J. B.↗
NASA NTRS1977

Large-size monodisperse latexes as a commercial space product

Proposed spacelab production of large-size (2-40 micron diameter) monodispersed latexes is discussed. Explanations are given for the present lack of monodisperse particles in this size range. The four main topics discussed are: (1) the potential uses of these large particle size latexes, (2) why it is necessary for the particles to have a very narrow size distribution, (3) why large amounts of these monodisperse latexes are needed, and (4) why it is necessary to go to microgravity to prepare these latexes.

Kornfeld, D. M.↗
NASA NTRS1977

Studies of perception of information on the spatial position of an aircraft

Problems of pilot visual perception were identified, specifically problems of identifiying the surface of the earth at moment of transition from flight-instrument observation. The percepted difficulties studied were: (1) the accuracy of defining the slope of the flight path during lack of visibility of the actual line of the horizon, (2) the accuracy of predicting the time remaining before landing under conditions of limited external visibility, and (3) the structure of the shape of the earth's surface necessary for the maximum accurate determination of flight-path slope and prediction of time remaining to landing.

Zebrowski, M.↗
NASA NTRS1977

Early stages in the evolution of the atmosphere and climate on the Earth-group planets

The early evolution of the atmospheres and climate of the Earth, Mars and Venus is discussed, based on a concept of common initial conditions and main processes (besides known differences in chemical composition and outgassing rate). It is concluded that: (1) liquid water appeared on the surface of the earth in the first few hundred million years; the average surface temperature was near the melting point for about the first two eons; CO2 was the main component of the atmosphere in the first 100-500 million years; (2) much more temperate outgassing and low solar heating led to the much later appearance of liquid water on the Martian surface, only one to two billion years ago; the Martian era of rivers, relatively dense atmosphere and warm climate ended as a result of irreversible chemical bonding of CO2 by Urey equilibrium processes; (3) a great lack of water in the primordial material of Venus is proposed; liquid water never was present on the surface of the planet, and there was practically no chemical bonding of CO2; the surface temperature was over 600 K four billion years ago.

Moroz, V. I.↗