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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 595 records · Page 33
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NASA NTRS1975

Satellite laser ranging work at the Goddard Space Flight Center

The pulsed-laser satellite ranging systems presently being operated by the Goddard Space Flight Center are described along with their range and accuracy capabilities. The major subsystems are outlined, operation of the fixed system and the two mobile systems is discussed, and the performance of all three systems is evaluated. It is noted that these systems have an accuracy of better than 10 cm on a carefully surveyed range as well as in regular satellite ranging operations and are capable of ranging to all currently launched retroreflector-equipped satellites with the exception of Timation III. Future improvements discussed include a third mobile system which will be able to range distant satellites, such as Timation III, with an accuracy of better than 5 cm and the use of a frequency-doubled Nd:YAG laser in place of the ruby lasers now being employed.

Mcgunigal, T. E.↗
NASA NTRS1976

Preliminary meteorological results on Mars from the Viking 1 lander

The results from the meteorology instruments on the Viking 1 lander are presented for the first 4 sols of operation. The instruments are working satisfactorily. Temperatures fluctuated from a low of 188 K to an estimated maximum of 244 K. The mean pressure is 7.65 millibars with a diurnal variation of amplitude 0.1 millibar. Wind speeds averaged over several minutes have ranged from essentially calm to 9 meters per second. Wind directions have exhibited a remarkable regularity which may be associated with nocturnal downslope winds and gravitational oscillations, or to tidal effects of the diurnal pressure wave, or to both.

Hess, S. L.↗
NASA NTRS1976

Bow shock and magnetosheath waves at Mercury

Mariner 10 measurements at the Mercury bow shock provide examples where the magnetic field is approximately parallel or perpendicular to the bow shock normal. Upstream of a broad irregular parallel shock, left-hand circularly polarized waves are observed which cut off very sharply at about 4 Hz. Upstream of a perpendicular shock, righ-hand circularly polarized waves are observed which persist up to the Nyquist frequency of 12 Hz. Determination of the wave propagation vector as a function of frequency helps to identify conclusively the waves as whistler mode waves propagating from the shock. The magnetosheath downstream of the parallel shock is disturbed more than that downstream of the perpendicular shock, particularly below 1 Hz. In the latter case, regular left-hand-polarized waves observed slightly above the proton gyrofrequency are identified as ion cyclotron waves with wavelengths of about 300 km which have been Doppler shifted up to their observed frequency.

Fairfield, D. H.↗
NASA NTRS1976

The formation of Saturn's satellites and rings, as influenced by Saturn's contraction history

The paper investigates constraints imposed on the ice content of Saturn's satellites and rings by the planet's high luminosity during the early part of its quasi-equilibrium contraction phase. It is assumed that the addition of ices to the satellites was not completed until after the start of the quasi-equilibrium contraction and that the condensation of ices ceased at the same time within the primordial nebulae of Jupiter and Saturn. Using previously derived limits on the time of condensation cessation for Jupiter's system, the following tentative conclusions are made: (1) Titan is the innermost satellite at whose position a methane-containing ice could condense; (2) water ice could have condensed at the positions of all the satellites; (3) the systematic decrease in the mass of the regular satellites with decreasing distance from the planet may have been caused, in part, by the larger time intervals, for the closer satellites, between the start of contraction and the first condensation of ices at their positions; and (4) ammonia ices, primarily NH4SH, were able to condense at the positions of all but the innermost satellites. It is also shown that water ice could have condensed in the region of the rings near the end of the condensation period.

Pollack, J. B.↗
NASA NTRS1976

The 35-d X-ray profile of Her X-1

Results of an analysis of more than 500 days of Ariel 5 All-Sky Monitor data are reported which support the view that enhanced X-ray emission from Her X-1 occurs regularly in the source's 35-day cycle. The data analyzed show that the enhancement is centered at phase 0.55 (+ or - 0.05) relative to the maximum, has an intensity of at least one-fourth of the maximum, and has an apparent duration not exceeding 10% of the 35-day cycle. It is strongly suggested that the enhancement occurs in every cycle at about one-third of the maximum.

Holt, S. S.↗
NASA NTRS1975

CARETS: A prototype regional environmental information system. Volume 7: Land use information and air quality planning

The pilot national land use information system developed by the U.S. Geological Survey in the Central Atlantic Regional Ecological Test Site project has provided an improved technique for estimating emissions, diffusion, and impact patterns of sulfur dioxide (S0 2 ) and particulate matter. Implementation of plans to control air quality requires land use information, which, until this time, has been inadequate. The pilot system, however, provided data for updating information on the sources of point and area emissions of S0 2 and particulate matter affecting the Norfolk--Portsmouth area of Virginia for the 1971-72 winter (Dec.-Jan.-Feb.) and the annual 1972 period, and for a future annual period--1985. This emission information is used as input to the Air Quality Display Model of the Environmental Protection Agency to obtain diffusion and impact patterns for the three periods previously mentioned. The results are: (1) During the 1971-72 winter, estimated SO 2 amounts over an area with a SW-NE-axis in the central section of Norfolk exceeded both primary and secondary levels; (2) future annual levels of SO 2 , estimated by anticipated residential development and point-source changes, are not expected to cause serious deterioration of the region's present air quality; and (3) for the 1971-72 winter and annual 1972 period the diffusion results showed that both primary and secondary standards for particulate matter are regularly exceeded in central Norfolk and Portsmouth. In additions on the bas is of current control programs, the 1985 levels of particulate matter are expected to exceed the presently established secondary air quality standards throughout central Norfolk and Portsmouth and in certain areas of Virginia Beach. The land use information can be used to estimate emissions for inputs to diffusion models and to interpret the implications of diffusion patterns for: (1) Implementing various control strategies (2) selecting sites of air sampling stations, and (3) predicting the effects that proposed changes in land use might have on emission patterns and air quality.

Remote sensing↗
NASA NTRS1976

Three-dimensional structure of the extended solar magnetic field and the sunspot cycle variation in cosmic ray intensity

A principal cause for the eleven-year sunspot cycle variation in the primary cosmic ray intensity observed at earth may be a variation in the solid angle of the heliosphere occupied by the extended solar polar magnetic field. Galactic cosmic rays have relatively easy access to the inner solar system through the regular extended solar polar fields, and relatively difficult access through the irregular extended solar sector structure fields.

Svalgaard, L.↗
NASA NTRS1976

Modeling studies for a Mars penetrator heat flow measurement

There were, two different design concepts considered for the purpose of measuring heat flow as part of a Mars penetrator mission. The first of the tentative designs utilizes temperature sensors emplaced along the trailing umbilicus at regularly spaced intervals, no greater than 1m, which is thermally coupled to the adjacent regolith radiatively and possibly convectively or conductively. The second of the heat flow designs considered requires the radial deployment of two or more low thermal mass temperature sensors outward from the penetrator body over a vertical (depth) range on the order of 1m.

Keihm, S. J.↗
NASA NTRS1976

A postprocessor system for the data reduction and post analysis of NASTRAN results

NASTRAN analysis results are scanned to determine maximum and minimum displacements, forces and stresses. Allowables and margins of safety are computed, and in the case of multiple loading conditions, envelopes for displacements, forces, stresses and margins of safety are also produced for specified element sets. Graphical plots of the reduced or the regular NASTRAN results may be obtained superimposed either of a developed fuselage strip or on a projection of any specified part of the finite element model. The use of the data reduction, post analysis and graphical plotting capabilities provide the analyst with a fast and convenient tool for the study of NASTRAN analysis results and their presentation for project documentation.

Raibstein, A. I.↗
NASA NTRS1976

Orbital construction demonstration study

A conceptual design and program plan for an Orbital Construction Demonstration Article (OCDA) was developed that can be used for evaluating and establishing practical large structural assembly operations. A flight plan for initial placement and continued utility is presented as a basic for an entirely new shuttle payload line-item having great future potential benefit for space applications. The OCDA is a three-axis stabilized platform in low-earth orbit with many structural nodals for mounting large construction and fabrication equipments. This equipment would be used to explore methods for constructing the large structures for future missions. The OCDA would be supported at regular intervals by the shuttle. Construction experiments and consumables resupply are performed during shuttle visit periods. A 250 kw solar array provides sufficient power to support the shuttle while attached to the OCDA and to run construction experiments at the same time. Wide band communications with a Telemetry and Data Relay Satellite compatible high gain antenna can be used between shuttle revisits to perform remote controlled, TV assisted construction experiments.

Source record↗
NASA NTRS1977

Sampling video compression system

A system for transmitting video signal of compressed bandwidth is described. The transmitting station is provided with circuitry for dividing a picture to be transmitted into a plurality of blocks containing a checkerboard pattern of picture elements. Video signals along corresponding diagonal rows of picture elements in the respective blocks are regularly sampled. A transmitter responsive to the output of the sampling circuitry is included for transmitting the sampled video signals of one frame at a reduced bandwidth over a communication channel. The receiving station is provided with a frame memory for temporarily storing transmitted video signals of one frame at the original high bandwidth frequency.

Matsumoto, Y.↗
NASA NTRS1977

Mesoscale cloud phenomena observed by LANDSAT

Examples of certain mesoscale cloud features - jet cirrus, eddies/vortices, cloud banding, and wave clouds - were collected from LANDSAT imagery and placed into Mason's four groups of causes of cloud formation based on the mechanism of vertical motion which produces condensation. These groups are as follows: (1) layer clouds formed by widespread regular ascent; (2) layer clouds caused by irregular stirring motions; (3) convective clouds; and (4) clouds formed by orographic disturbances. These mechanisms explain general cloud formation. Once formed, other forces may play a role in the deformation of a cloud or cloud mass into unusual and unique meso- and microscale patterns. Each example presented is followed by a brief discussion describing the synoptic situation, and some inference into the formation and occurrence of the more salient features. No major attempt was made to discuss in detail the meteorological and topographic interplay producing these mesoscale features.

Ormsby, J. P.↗
NASA NTRS1976

Uhuru observations of Hercules X-1 during the low state of the 35-day cycle

X-ray emission from Her X-1 has been observed during the 23-day low state of the 35-day cycle. During this time, all the activity normally present during the high state was seen, including regular eclipses, absorption 'dips,' and 1.24-s pulsations. The present observations are compared with the models of Her X-1 derived by Roberts (1974), Gerend and Boynton (1976), Katz (1973), and Petterson (1975). It is suggested that a hot optically thin corona along both faces of the accretion disk can produce the unpulsed component of emission observed during both the high- and low-intensity states.

Jones, C.↗
NASA NTRS1976

Viking-1 meteorological measurements - First impressions

A preliminary evaluation is given of in situ meteorological measurements made by Viking 1 on Mars. The data reported show that: (1) the atmosphere has approximate volume mixing ratios of 1.5% argon, 3% nitrogen, and 95% carbon dioxide; (2) the diurnal temperature range is large and regular, with a sunrise minimum of about 188 K and a midafternoon maximum near 244 K; (3) air and ground temperatures coincide quite closely during the night, but ground temperature exceeds air temperature near midday by as much as 25 C; (4) the winds exhibit a marked diurnal cycle; and (5) a large diurnal pressure variation with an afternoon minimum and an early-morning maximum parallels the wind pattern. The variations are explained in terms of familiar meteorological processes. It is suggested that latent heat is unlikely to play an important role on Mars because no evidence has been observed for traveling synoptic-scale disturbances such as those that occur in the terrestrial tropics.

Hess, S. L.↗
NASA NTRS1976

Long duration exposure facility - A multipurpose free-flying experiment carrier

The Long Duration Exposure Facility (LDEF) is being developed to accommodate, using the Shuttle, a class of technology, science, and applications experiments which do not require a sophisticated or dedicated satellite. The LDEF is a simple reusable structure approximately 4.3 m in diameter and 9 m in length. The basic LDEF consists of a structural framework whose cross section is a 12-sided regular polygon. A facility description is provided, taking into account the structure, aspects of attitude stabilization, the experiment trays, the experiment exposure control canister, the environment monitoring system, and Shuttle bay environment measurements. Missions and questions of experiment selection are discussed, giving attention to orbits, dynamic motions, a space debris damage experiment, thermal coating experiments, the solar cells and arrays experiment, and the active optical components experiment.

Kinard, W. H.↗
NASA NTRS1976

On estimating thermal conductivity coefficients in the critical region of gases

The thermal conductivity of a fluid exhibits a pronounced anomalous increase in a large range of densities and temperatures around the gas-liquid critical point. In this paper we discuss an attempt to estimate the thermal conductivity in the critical region of fluids from a knowledge of the equilibrium properties and the regular behavior of the transport properties outside the critical region.

Hanley, H. J. M.↗
NASA NTRS1976

Vulcanism, mercury-sensitized photo-reactions and abiogenetic synthesis - A theoretical treatment

Attention is called to the photodynamic and thermodynamic properties of Periodic Group IIb elements, most notably Hg, as they relate to ultra-violet sensitization in organic chemical reactions. The energy levels of 6 1P1 and 6 3P1 resonance states and the high vapor pressure (greater than 0.001 mm) of the metal at temperatures as low as 293 K bring Hg with the range of bond dissociation energies in most organic molecules and many inorganics. These capabilities considered together with recent evidence for Hg emission as a regular part of volcanic and geothermal processes provide the basis for a proposal that Hg-sensitized ultraviolet photo-reactions may have played a significant part in abiogenetic organic synthesis on the primative earth.

Siegel, S. M.↗
NASA NTRS1977

The electric fields produced by lightning stepped leaders

The electric fields produced by stepped and dart-stepped leaders which immediately precede return strokes in lightning discharges to the ground have been recorded in Florida and Arizona. The mean interval time between normal steps is about 16 microsec, and the mean interval between dart steps is 6-8 microsec. The amplitudes of leader pulses in Florida increase just prior to the return stroke, the largest usually being about 10% of the return-stroke peak. In Arizona the leader pulse amplitudes are smaller than those in Florida, in relation to the return stroke, and are not as easy to identify. The shapes of the fields produced by normal steps are similar to dart steps, and the dart steps are very similar to regular sequences of pulses produced by many intracloud discharges. The 10-90% rise times of individual step wave forms are often less than 0.3 microsec, and the full width at half maximum of a step pulse is typically 0.4-0.5 microsec under conditions where the propagation distortion is minimal. The amplitudes and the shapes of leader step wave forms suggest that the peak step current is at least 2000-8000 A close to the ground and that the maximum rate of change of step current is 6-24 kA/microsec or larger. A rough estimate of the minimum charge lowered during the formation of a step is 0.001 to 0.004 C.

Krider, E. P.↗