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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 1,369 records · Page 76
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NASA NTRS1979

The effect of disturbance on a wing

Disturbances such as flap and aileron hinges and poorly faired spoilers were simulated in a computer wind tunnel. The total drag of a single roughness element does not depend only on the size of that element. Its position on the wing has a surprisingly strong effect. In particular, a roughness element on the convex side of a deflected flap or aileron causes a very substantial increase in drag. Very few experimental data are available for comparison. Good agreement with experiment can be achieved, however, by adapting a fictive step size. The correlation between the real roughness-element size and the drag increase remains to be determined. Simple, fundamental experiments are suggested which will allow a theoretical estimation of the drag increase due to roughness elements.

Eppler, R.↗
NASA NTRS1979

Primordial inhomogeneities in the expanding universe. I - Density and velocity distributions of galaxies in the vicinities of rich clusters

The density profiles and Hubble flow deviations in the vicinities of rich galaxy clusters are derived for a variety of models of initial density and velocity perturbations at the recombination epoch. The galaxy correlation function, measured with respect to the Abell clusters, is used to normalize the theoretical models. The angular scales of the required primordial inhomogeneities are calculated. It is found that the resulting density profiles around rich clusters are surprisingly insensitive to the shape of the initial perturbations and also to the cosmological density parameter, Omega. However, it is shown that the distribution of galaxy radial velocities can provide a possible means of deriving Omega.

Silk, J.↗
NASA NTRS1979

The impact of gas-surface reactions on mass spectrometric measurements of atomic nitrogen

The paper presents a simplified model of the ion source chemistry, explains several details of the data reduction method used in obtaining atomic-nitrogen (N) densities from OSS data, and discusses implications of gas-surface reactions for the design of future satellite-borne mass spectrometers. Because of various surface reactions, N appears in three different forms in the ion source, as N, NO, and NO2. Considering the rather small spin modulation of NO and NO2 in the semi-open ionization chamber used in the OSS instrument, it is not surprising that these reaction products have not been previously identified in closed source instruments as a measure of the presence of atomic nitrogen. Warmup and/or outgassing of the ion source are shown to drastically reduce the NO2 concentration, thereby making possible reliable measurement of ambient N densities.

Engebretson, M. J.↗
NASA NTRS1979

A study of magnetosphere dynamics during auroral electrojet events by observations of energetic electron intensity changes at synchronous orbit

The central theme of the considered investigation is the surprising detailed correlation between dynamical changes in electron directional intensity measurements at synchronous orbit and the auroral electrojet currents in the polar ionosphere. The statistical study reported has been carried out following the discovery by Erickson and Winckler (1973) of a close relationship between the time profiles of auroral electrojet intensifications and electron intensity decreases observed in the pre-midnight sector at synchronous orbit. The electron data used in the study were obtained during 1967 and 1968 by the University of Minnesota magnetic spectrometer carried onboard ATSl.

Erickson, K. N.↗
NASA NTRS1979

On the configuration of the nightside Venus ionopause

Nightside measurements of electron and ion concentrations by instruments on the Pioneer Venus Orbiter have revealed an ionopause which is highly dynamic and whose global configuration is surprisingly complex. Inbound crossing which occur at high northern latitudes encounter the ionopause at an average altitude of 870 km in the late afternoon sector. The average ionopause altitude increases slightly near 100 deg solar zenith angle (SZA) followed by a nightside compression to well below 500 km. The outbound crossings of the ionopause occur at about 20 deg south of the equator. The ionospause at this latitude is found at an average altitude of 800 km in the afternoon-evening sector between 65 and 110 deg SZA, followed by a pronounced rise to altitudes as high as 3000 km in a pronounced bulge near 130 deg SZA.

Brace, L. H.↗
NASA NTRS1979

Voyager 1 - Energetic ions and electrons in the Jovian magnetosphere

The observations of the cosmic-ray subsystem have added significantly to our knowledge of Jupiter's magnetosphere. The most surprising result is the existence of energetic sulfur, sodium, and oxygen nuclei with energies above 7 MeV per nucleon which were found inside of Io's orbit. Also, significant fluxes of similarly energetic ions reflecting solar cosmic-ray composition were observed throughout the magnetosphere beyond 11 times the radius of Jupiter. It was also found that energetic protons are enhanced by 30 to 70% in the active hemisphere. Finally, the first observations were made of the magnetospheric tail in the dawn direction out to 160 Jupiter radii.

Vogt, R. E.↗
NASA NTRS1978

Comparisons between observed and predicted cosmogenic noble gases in lunar samples

Comparisons are made between cosmogenic production rates and isotopic ratios predicted on the basis of nuclear systematics with those observed in well-documented lunar samples. Although some significant differences are found, the agreement in general is surprisingly good. The predicted production rates for Ar-38 and Xe-126 agree reasonably well with observation but the predicted rate for Ne-21 appears to be too high; in most cases the predicted rate for Kr-83 agrees to within 50%, although some larger differences are apparent. There are some prominent cases in which predicted isotopic compositons differ from observation: Kr-78/Kr-83 trends in the wrong sense with the Zr/Sr ratio; Xe-124/Xe-126 is too large by about 13%; Xe-128/Xe-126 is too small by about 6%; Xe-130/Xe-126 is too low by 30-40%.

Hohenberg, C. M.↗
NASA NTRS1979

The radiation field wave forms produced by intracloud lightning discharge processes

The large-amplitude radiation field pulses produced by intracloud lightning discharge processes have been recorded with submicrosecond time resolution. The wave forms are distinctly different from those produced by return strokes in cloud-to-ground lightning, yet they are surprisingly alike within a discharge and in different discharges. The shapes tend to be bipolar, with two or three narrow, fast-rising pulses superimposed on the initial half cycle. Pulses with a positive initial polarity are usually produced in the several tens of milliseconds prior to the first return stroke in a cloud-to-ground discharge. Positive pulses tend to occur at regular intervals and have a mean full width of about 40 + or - 13 microsec. Negative pulses are usually produced during isolated cloud discharges at more random intervals and have shapes similar to the positive pulses but with more variability. The implications of the field shapes and polarities for the physics of intracloud discharge processes are discussed.

Weidman, C. D.↗
NASA NTRS1979

Composition and structure of the Venus atmosphere - Results from Pioneer Venus

The composition of the Venusian atmosphere was studied using a mass spectrometer on the Pioneer Venus sounder probe. The single-focusing magnetic-sector spectrometer scanned the mass range from hydrogen through mercury with a dynamic range of six decades. Data taken by the mass spectrometer were compared with those of a gas chromatograph, resulting in slight discrepancies due to the use of a sputter ion pump acting as a sink for entry of rare gases through the inlet leak. A surprisingly large concentration of primordial Ar-36 and Ar-38 was discovered in a ratio of 5 to 1. It was concluded that the large excess of primordial argon was a valid result and that the mixing of HCl in the lower Venusian atmosphere was less than a few parts per million. Arguments against the sun as the source for excess primordial gases on Venus were presented. Concentrations of other elements such as Ne, Kr, He, S, and O were discussed. Although the mass peaks in the spectrum were real, it was not clear whether all of the chemical reactions (i.e., COS production) actually occurred in the atmosphere. Until further analysis can be made, it will be uncertain how the inlet system, which is at atmospheric temperature, affected the results.

Hoffman, J. H.↗
NASA NTRS1979

Sunspots and the physics of magnetic flux tubes. IV - Aerodynamic lift on a thin cylinder in convective flows

The aerodynamic lift exerted on a long circular cylinder immersed in a convective flow pattern in an ideal fluid is calculated to establish the equilibrium position of the cylinder. The calculations establish the surprising result that the cylinder is pushed out the upwellings and the downdrafts of the convective cell, into a location midway between them. The implications for the intense magnetic flux tubes in the convection beneath the surface of the sun are considered.

Tsinganos, K. C.↗
NASA NTRS1979

Preliminary results from the Pioneer Venus Orbiter infrared radiometer - Temperature and dynamics in the upper atmosphere

Data from the infrared radiometer aboard the Pioneer Venus Orbiter are examined and interpreted within the context of zonally averaged temperatures and circulation in the upper atmosphere of Venus. Surprisingly, the northern hemisphere pole is warmer than the equator throughout most of the region sampled. This implies both a rapid decrease with height of the 100 m/s cloud top winds previously observed, and the probable existence of large (50 to 100 m/s) meridional winds.

Elson, L. S.↗
NASA NTRS1979

A connection between block and convolutional codes

Convolutional codes of any rate and any constraint length give rise to a sequence of quasi-cyclic codes. Conversely, any quasi-cyclic code may be convolutionally encoded. Among the quasi-cyclic codes are the quadratic residue codes, Reed-Solomon codes and optimal BCH codes. The constraint length K for the convolutional encoding of many of these codes (Golay, (48, 24) QR, etc.) turns out to be surprisingly small. Thus using the soft decoding techniques for convolutional decoding, a new maximum likelihood decoding algorithm for many block codes is established. Conversely an optimal quasi-cyclic code will yield a convolutional encoding with optimal local properties and therefore with good infinite convolutional coding properties.

Solomon, G.↗
NASA NTRS1979

Information Theory and the Earth's Density Distribution

An argument for using the information theory approach as an inference technique in solid earth geophysics. A spherically symmetric density distribution is derived as an example of the method. A simple model of the earth plus knowledge of its mass and moment of inertia lead to a density distribution which was surprisingly close to the optimum distribution. Future directions for the information theory approach in solid earth geophysics as well as its strengths and weaknesses are discussed.

Rubincam, D. P.↗
NASA NTRS1980

Effect of sodium, potassium, magnesium, calcium, and chlorine on the high temperature corrosion of IN-100, U-700, IN-792, and Mar M-509

The effects of potential impurities such as Na, K, Mg, Ca, and Cl, in coal-derived liquid fuels on accelerated corrosion of IN-100, U-700, IN-792, and Mar M-509 were investigated using a Mach 0.3 burner rig for times to 200 hours in one hour cycles. These impurities were injected in combination as aqueous solutions into the combustor. Other variables were time, temperature, and fuel-to-air ratio. The experimental matrix was a central composite fractional fractorial design divided into blocks to allow modification of the design as data was gathered. The extent of corrosion was determined by metal consumption. The time exponent was near 1.0 for the least corrosion resistant alloys, U-700 and IN-100; near 0.8 for the moderately resistant IN-792; and close to Mar M-509, the most corrosion resistant alloy. As anticipated, corrosion rapidly increased with increasing temperature as well as Na and K concentrations, while corrosion decreased somewhat as the Ca concentration increased for all alloys. Mg was beneficial for the Ni-base alloys but had little effect on the Co-base alloy. Surprisingly, the effect of increasing Cl was to decrease the corrosion of all alloys. Little interaction among the dopants was noted.

Lowell, C. E.↗
NASA NTRS1979

Evaluation of use of MPAD trajectory tape and number of orbit points for orbiter mission thermal predictions

The application of using the mission planning and analysis division (MPAD) common format trajectory data tape to predict temperatures for preflight and post flight mission analysis is presented and evaluated. All of the analyses utilized the latest Space Transportation System 1 flight (STS-1) MPAD trajectory tape, and the simplified '136 note' midsection/payload bay thermal math model. For the first 6.7 hours of the STS-1 flight profile, transient temperatures are presented for selected nodal locations with the current standard method, and the trajectory tape method. Whether the differences are considered significant or not depends upon the view point. Other transient temperature predictions are also presented. These results were obtained to investigate an initial concern that perhaps the predicted temperature differences between the two methods would not only be caused by the inaccuracies of the current method's assumed nominal attitude profile but also be affected by a lack of a sufficient number of orbit points in the current method. Comparison between 6, 12, and 24 orbit point parameters showed a surprising insensitivity to the number of orbit points.

Vogt, R. A.↗
NASA NTRS1979

Supernovae and the origin of the solar system

This review concentrates on recent ideas involving a relationship between the early solar system and supernova explosions. It summarizes briefly the data that has helped inspire those ideas. Because the true relationship is still unknown and generates controversy, the distinct ideas are introduced singly in the historical context of their origins, and the active sense of surprise and controversy is visible. Quotations from pivotal papers are used as part of the exposition. The subject involves equally the isotopic anomalies detected in meteorites and the dynamic events of galactic evolution, nucleosynthesis, and protosolar collapse. Whatever the correct situation is, new connections have been found between the origin of the elements and the formation of the solar system. The objective of this review is to enable interested space scientists to quickly identify the competing points of view and the experiments and theories that have led to them.

Clayton, D. D.↗
NASA NTRS1979

Vibronic effects in the predissociation of the C/1/Pi/u state of C2N2

The partitioning of excess photochemical energy as a function of the vibrational energy of the state of C2N2 has been measured. Surprisal theory has been used to analyze the data and it shows that complete randomization does not occur before dissociation. The results are also inconsistent with the predictions of the quasidiatomic theory for photodissociation.

Miller, G. E.↗
NASA NTRS1979

A kinetic approach to magnetospheric modeling

The earth's magnetosphere is caused by the interaction between the flowing solar wind and the earth's magnetic dipole, with the distorted magnetic field in the outer parts of the magnetosphere due to the current systems resulting from this interaction. It is surprising that even the conceptually simple problem of the collisionless interaction of a flowing plasma with a dipole magnetic field has not been solved. A kinetic approach is essential if one is to take into account the dispersion of particles with different energies and pitch angles and the fact that particles on different trajectories have different histories and may come from different sources. Solving the interaction problem involves finding the various types of possible trajectories, populating them with particles appropriately, and then treating the electric and magnetic fields self-consistently with the resulting particle densities and currents. This approach is illustrated by formulating a procedure for solving the collisionless interaction problem on open field lines in the case of a slowly flowing magnetized plasma interacting with a magnetic dipole.

Whipple, E. C., Jr.↗