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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 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Satellite nuclear power station: An engineering analysis

A nuclear-MHD power plant system which uses a compact non-breeder reactor to produce power in the multimegawatt range is analyzed. It is shown that, operated in synchronous orbit, the plant would transmit power safely to the ground by a microwave beam. Fuel reprocessing would take place in space, and no radioactive material would be returned to earth. Even the effect of a disastrous accident would have negligible effect on earth. A hydrogen moderated gas core reactor, or a colloid-core, or NERVA type reactor could also be used. The system is shown to approach closely the ideal of economical power without pollution.

Williams, J. R.↗
NASA NTRS1973

The ultraviolet /1200-1900 Angstrom/ spectrum of Venus

A far-ultraviolet moderate-resolution spectrum of Venus has been obtained by using an accurately pointed rocket-borne telescope-spectrophotometer. H I 1216 A, O I 1304 A, O I 1356 A, C I 1561 A, C I 1657 A, and the CO fourth-positive band system were observed in emission. Brightnesses and upper limits for other emissions are reported. An estimate of the O concentration indicates approximately 10% at a column density of 4 x 10 to the 16th power CO2 per sq cm. The large CO fourth-positive emission indicates that the CO concentration is also high.

Rottman, G. J.↗
NASA NTRS1973

A preliminary study of the neutral wind in the auroral E region

Auroral zone E region neutral winds have been derived from simultaneous measurements of ion drift velocities at different altitudes by the incoherent scatter radar facility at Chatanika, Alaska. The wind derived for quiet and moderately disturbed days shows a consistent pattern during the daytime and appears to be that expected from a day-night pressure asymmetry. In the nighttime, however, the winds are much more variable, apparently responding to the momentum transfer and heating effects of ion drag when sizable electric fields and electron densities are present.

Brekke, A.↗
NASA NTRS1973

A relaxation method for calculating transonic flows with detached bow shocks

The use of Murman and Krupp's (1971) method for calculating steady, inviscid, transonic flows with imbedded shock waves is discussed in application to two-dimensional problems for transonic flows past sharp and moderately blunt nosed geometries. A relaxation algorithm is used to solve the equations.

Murman, E. M.↗
NASA NTRS1973

Utilization of low-redundancy convolutional codes

This paper suggests guidelines for the utilization of low-redundancy convolutional codes with emphasis on providing a quick look capability (no decoding) and a moderate amount of coding gain. The performance and implementation complexity of threshold, Viterbi, and sequential decoding when used with low-redundancy, systematic, convolutional codes is discussed. An extensive list of optimum, short constraint length codes is found for use with Viterbi decoding, and several good, long constraint length codes are found for use with sequential decoding.

Cain, J. B.↗
NASA NTRS1973

Optical transmission in a circumstellar dust cloud

It is shown from the equation of radiative transfer that the visual attenuation of an optically thick, spherically symmetric circumstellar cloud of dust can be small compared to that produced by an equal optical depth of interstellar dust. The reasons for this are the moderately large albedos of the grains and their tendency to emphasize forward scattering.

Jones, T. W.↗
NASA NTRS1973

Large-scale structure of the interplanetary medium. II - Evolving magnetic configurations deduced from multi-spacecraft observations

Description of a method for constructing large-scale (about 0.25 AU) interplanetary magnetic field lines using only solar wind velocity from well-separated appropriately located spacecraft. The technique is based on 'labeling' the field lines at each spacecraft with their coronal connection longitudes calculated in the EQRH (extrapolated quasi-radial hypervelocity) approximation. Even though the EQRH approximation is most applicable to quasi-steady solar wind, it is proposed that it should also be satisfactorily accurate for moderately evolving conditions. For strongly evolving conditions (e.g., flare-associated plasma) a straightforward correction based on the inferred coronal longitudinal velocity profile is proposed. To illustrate the multispacecraft EQRH technique, a calculation is performed in which the interplanetary field lines in a model evolving solar wind disturbance are deduced from model observations at separated spacecraft. Since the expected agreement is found, data from Pioneers 8 and 9 and Vela are used to construct field lines for an unusually quiet period (Apr. 26-30, 1969) and for a flare-associated disturbance accompanied by a Forbush decrease (Mar. 23-25, 1969).

Nolte, J. T.↗
NASA NTRS1973

An ultrahigh rate digital tape recorder for spacecraft applications

Spaceborne digital recorders must satisfy the conflicting requirements of maximum data storage of high-rate data (particularly for high-resolution sensor data) and a long life with high reliability (meaning rugged design and moderate head-to-tape speeds). The multitrack longitudinal (fixed head) recorder can successfully resolve this conflict and satisfy both requirements. An evolutionary machine is described which was originally designed to store and reproduce 30 minutes of 39.9-Mb/sec sensor data, for mission lives on the order of one year; newer designs have surpassed these parameters by significant amounts.

Thompson, C. R.↗
NASA NTRS1974

The limitations of wind measurement accuracy for balloon systems

The error in horizontal wind field measurements as computed from the trajectory of balloons with linear and quadratic rise rates (as functions of altitude) has been derived. Balloon trajectories through light, moderate, and severe wind fields have been considered. Figures are presented which show the wind error vs altitude for various rise rates in each wind field, assuming linear smoothing of the trajectory data. The rise rate profile of the Jimsphere is analyzed as a special case. The results and figures presented are useful in determining the ultimate capability of rising balloon systems in general and for the Jimsphere system in particular for measuring wind from the surface to 18 km. Using the figures presented, it is possible to estimate the wind accuracy that can be achieved by any type of rising balloon by knowing only its rise rate behavior vs altitude. In addition, the results can be used in balloon design to determine what rise rate function is needed to achieve specified wind accuracies. A table is presented which shows the balloon radius for smooth and roughened spheres needed to achieve 2 to 20 m/sec rise rates at 10 and 14 km altitudes.

Luers, J. K.↗
NASA NTRS1974

Polar cap auroral electron fluxes observed with Isis 1

Three types of auroral particle precipitation have been observed over the polar caps, well inside the auroral oval, by means of the soft particle spectrometer on the Isis 1 satellite. The first type is a uniform, very soft (about 100 eV) electron 'polar rain' over the entire polar cap; this may well be present with very weak intensity at all times, but it is markedly enhanced during worldwide geomagnetic storms. A second type of precipitation is a structured flux of electrons with energies near 1 keV, suggestive of localized 'polar showers'; it seems likely that these are the cause of the sun-aligned auroral arcs that have been observed during moderately quiet conditions. During periods of intense magnetic disturbance this precipitation can become very intense and exhibit a characteristic pattern that we have come to call a 'polar squall'.

Winningham, J. D.↗
NASA NTRS1973

Photodesorption from interstellar dust grains

An experiment to measure the photodesorption of physisorbed gases from a cold fused quartz substrate by near UV photons is described. The observed yield (mol/photon) is as large as .00001, a higher yield is likely in the vacuum UV. Included is a discussion of the photodesorption process and some applications to the interstellar medium. The observed yield is enough to maintain molecular abundances in moderate density interstellar clouds in equilibrium.

Greenberg, L. T.↗
NASA NTRS1974

A detailed investigation of flight buffeting response at subsonic and transonic speeds

The structural response to aerodynamic buffeting during moderate-to-high-g maneuvers was investigated. Dynamic response data measured during a flight loads program were analyzed to obtain power spectra and rms values of response for 19 sensors mounted on the test aircraft. In this paper, peaks in the power spectra of accelerations measured at the wing tips, center of gravity and pilot's seat, and wing vertical shear, bending moment and torsional moments are correlated with natural vibration modes. The amplitudes of response are compared to show effects of angle of attack, sensor type and location, Mach number, and altitude.

Benepe, D. B.↗
NASA NTRS1974

Holographic studies of shock waves within transonic fan rotors

NASA has funded two separate contracts to apply pulsed laser holographic interferometry to the detection of shock patterns in the outer span regions of high tip speed transonic rotors. The first holographic approach used ruby laser light reflected from a portion of the centerbody just ahead of the rotor. These holograms showed the bow wave patterns upstream of the rotor and the shock patterns just inside the blade row near the tip. The second holographic approach, on a different rotor, used light transmitted diagonally across the inlet annulus past the centerbody. This approach gave a more extensive view of the region bounded by the blade leading and trailing edges, by the part span shroud and by the blade tip. These holograms showed the passage shock emanating from the blade leading edge and a moderately strong conical shock originating at the intersection of the part span shroud leading edge and the blade suction surface.

Benser, W. A.↗
NASA NTRS1974

Catalytic trimerization of aromatic nitriles for synthesis of polyimide matrix resins

Aromatic nitriles may be trimerized at moderate temperature and pressure with p-toluenesulfonic acid as catalyst. Studies were conducted to establish the effect of the reaction temperature, pressure, time, and catalyst concentration on yield of the trimerized product. Trimerization studies were also conducted to establish the effect of substituting electron donating or withdrawing groups on benzonitrile. Preliminary results of using the catalytic trimerization approach to prepare s-triazine cross-linked polyimide/graphite fiber composites are presented.

Hsu, L.-C.↗
NASA NTRS1974

Morphology of lunar craters - A test of lunar erosional models

The present work is a test of published theoretical and experimental studies of crater erosion by micrometeorite bombardment which predict systematic variations in the morphology of lunar craters as a function of crater diameter and crater age. Numerical, ranking-type degradation classifications indicate that the craters on Mare Imbrium and Mare Tranquillitatis confirm these predictions by showing a systematic increase in degradation with decreasing diameter for craters smaller than a few kilometers in diameter but larger than the equilibrium diameter, and by showing fixed proportions of fresh, moderately degraded, and very degraded craters under equilibrium conditions. Furthermore, the relative ages of the two mare surfaces may be determined using a diameter/mean-degradation-number curve. These determinations of relative age and process of crater erosion are both essentially independent of the traditionally studied crater diameter/frequency relationships.

Mcgill, G. E.↗
NASA NTRS1974

Differential transmission of sunlight on Mars - Biological implications

A euphotic zone seems to exist at about 1 cm subsurface in the Martian epilith. At this depth, visible light is still intense enough to be utilized by conceivable photosynthetic organisms; but the germicidal ultraviolet intensities at the Martian surface have been reduced to values manageable by terrestrial life. Such euphotic zone organisms would experience moderately high Martian temperatures at equatorial latitudes and can be dispersed readily during global dust storms. During such storms the Martian euphotic zone may reach the surface. The aerosol content of the Martian atmosphere can be monitored by multiband single-line scans of the sun at large zenith angles by the Viking lander camera; and the postulated euphotic zone organisms can be searched for with the Viking lander sample arm and biology experiments.

Sagan, C.↗
NASA NTRS1974

Clinical aspects of blood pressure autorhythmometry

Self-measurements made by a 55-year-old physician with mild to moderate hypertension of ten years' duration are considered. The physician had been in excellent health until age 45 when sustained elevation of blood pressure up to 180/100 mmHg and a slight aortic diastolic murmur were noted. On the basis of the investigation it is suggested that physical and mental performance measures provide an objective basis for assessing the desirability of a given physiological change. Such studies will have to be complemented by a search for long-term effects.

Levine, H.↗
NASA NTRS1974

Production of fissioning uranium plasma to approximate gas-core reactor conditions

The intense burst of neutrons from the d-d reaction in a plasma-focus apparatus is exploited to produce a fissioning uranium plasma. The plasma-focus apparatus consists of a pair of coaxial electrodes and is energized by a 25 kJ capacitor bank. A 15-g rod of 93% enriched U-235 is placed in the end of the center electrode where an intense electron beam impinges during the plasma-focus formation. The resulting uranium plasma is heated to about 5 eV. Fission reactions are induced in the uranium plasma by neutrons from the d-d reaction which were moderated by the polyethylene walls. The fission yield is determined by evaluating the gamma peaks of I-134, Cs-138, and other fission products, and it is found that more than 1,000,000 fissions are induced in the uranium for each focus formation, with at least 1% of these occurring in the uranium plasma.

Lee, J. H.↗