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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 901 records · Page 50
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NASA NTRS1974

Human physiological problems in zero gravity - An attempt at understanding through systems analysis

When the experimental situation is that of man exposed to a gravitationless environment for varying periods of time, the possible importance and value of a related modeling effort is readily apparent. One of the main objectives of the Skylab Program, with its missions of 28, 59, and 85 day duration concerned biomedical investigations of various types, and large amounts of relevant experimental data have been gathered and are in the process of being sorted and interpreted. In order to be of eventual usefulness in forming and testing consistent physiological hypotheses concerning the effect of zero gravity on man, a modeling effort was established in 1972 through the General Electric Company, Space Division, Houston, Texas. An account is given of some of the developments completed or in progress as part of this modeling effort. A long-term cardiovascular model and a large model of the systemic circulation are discussed.

White, R. J.↗
NASA NTRS1975

On the effect of timing errors in run length codes

Many redundancy removal algorithms employ some sort of run length code. Blocks of timing words are coded with synchronization words inserted between blocks. The probability of incorrectly reconstructing a sample because of a channel error in the timing data is a monotonically nondecreasing function of time since the last synchronization word. In this paper we compute the 'probability that the accumulated magnitude of timing errors equal zero' as a function of time since the last synchronization word for a zero-order predictor (ZOP). The result is valid for any data source that can be modeled by a first-order Markov chain and any digital channel that can be modeled by a channel transition matrix. An example is presented.

Wilkins, L. C.↗
NASA NTRS1975

Petrology of lunar soils

The paper summarizes the physical and petrographic characteristics of the finer-grained fractions (less than 1 cm) of lunar regolith soil in Apollo and Luna samples. Lunar soils are poorly sorted and consist mostly of lithic and mineral debris derived by impact comminution of the underlying bedrock and glass particles formed by impact melting. Agglutinates constitute an important soil component and are key factors in the genetic history of lunar soil. Some models concerning the development of lunar regolith based on soil studies are examined.

Heiken, G.↗
NASA NTRS1975

Stratification in the lunar regolith - A preliminary view

Although our knowledge of lunar regolith stratification is incomplete, several categories of thick and thin strata have been identified. Relatively thick units average 2 to 3 cm in thickness, and appear surficially to be massive. On more detailed examination, these units can be uniformly fine-grained, can show internal trends, or can show internal variations which apparently are random. Other thick units contain soil clasts apparently reworked from underlying units. Thin laminae average approximately 1 mm in thickness; lenticular distribution and composition of some thin laminae indicates that they are fillets shed from adjacent rock fragments. Other dark fine-grained well-sorted thin laminae appear to be surficial zones reworked by micrometeorites. Interpretations of stratigraphic succession can be strengthened by the occurrence of characteristic coarse rock fragments and the orientation of large spatter agglutinates, which are commonly found in their original depositional orientation.

Duke, M. B.↗
NASA NTRS1975

Evidence for magnetic field line reconnection in the solar wind

The basic scheme of Petschek's (1963) models for slow and fast magnetic reconnection in the solar wind is reviewed in order to determine what sort of results one would expect from satellite observations of possible reconnection processes. Data from HEOS 1 and OGO 5 are then analyzed, in which four observations of neutral sheet structures with large change of magnetic field direction were made. All four may be interpreted as indicating magnetic line reconnections rather than as D-sheets because they all show two distinct discontinuities which bound a lower magnetic field intensity region. The geometry of the magnetic field in the reconnection region appears to be similar to that described by Petschek. In one case the reconnection rate is in agreement with Petschek's prediction, but in the other three cases it is much larger than his limit. The reconnection rates observed do, however, agree with Sonnerup's (1972) limit.

Formisano, V.↗
NASA NTRS1977

Data-management and information system

User command language consists of unabbreviated English words. System allows user to create, delete, sort, merge, update, punch, or transfer all or portion of any file in system without programmer assistance.

Long, J. J.↗
NASA NTRS1977

Information retrieval and display system

Versatile command-driven data management system offers users, through simplified command language, a means of storing and searching data files, sorting data files into specified orders, performing simple or complex computations, effecting file updates, and printing or displaying output data. Commands are simple to use and flexible enough to meet most data management requirements.

Groover, J. L.↗
NASA NTRS1975

MIRADS-2 Implementation Manual

The Marshall Information Retrieval and Display System (MIRADS) which is a data base management system designed to provide the user with a set of generalized file capabilities is presented. The system provides a wide variety of ways to process the contents of the data base and includes capabilities to search, sort, compute, update, and display the data. The process of creating, defining, and loading a data base is generally called the loading process. The steps in the loading process which includes (1) structuring, (2) creating, (3) defining, (4) and implementing the data base for use by MIRADS are defined. The execution of several computer programs is required to successfully complete all steps of the loading process. This library must be established as a cataloged mass storage file as the first step in MIRADS implementation. The procedure for establishing the MIRADS Library is given. The system is currently operational for the UNIVAC 1108 computer system utilizing the Executive Operating System. All procedures relate to the use of MIRADS on the U-1108 computer.

Source record↗
NASA NTRS1977

Effects of pressure waves

Two parameters, side on overpressure and side on impulse loads, and their application to the determination of structural damage to buildings and vehicles in the vicinity of an explosion are investigated. Special consideration was given to what constitutes damage and what level of damage is acceptable. Solutions were sorted through the examination of glass breakage, curve fit to bomb damage, overturning of marginal structures (buses, trucks, mobile homes) subject to toppling, and initiation of yielding in either beam or plate structural components. Three different empirical pressure versus impulse diagrams were presented - the first is for minor structural damage involving wrenched joints and partitions, the second is for major damage structural damage with load bearing members at least partially destroyed, and the third is for 50% to 75% of the building demolished. General guidelines were obtained from the results when the accurate structural details are unknown.

Source record↗
NASA NTRS1976

Particulate and aerosol detector

A device is described for counting aerosols and sorting them according to either size, mass or energy. The component parts are an accelerator, a capacitor sensor and a readout. The accelerator is a means for accelerating the aerosols toward the face of the capacitor sensor with such force that they partially penetrate the capacitor sensor, momentarily discharging it. The readout device is a means for counting the number of discharges of the capacitor sensor and measuring the amplitudes of these different discharges. The aerosols are accelerated by the accelerator in the direction of the metal layer with such force that they penetrate the metal and damage the oxide layers, thereby allowing the electrical charge on the capacitor to discharge through the damaged region. Each incident aerosol initiates a discharge path through the capacitor in such a fashion as to vaporize the conducting path. Once the discharge action is complete, the low resistance path no longer exists between the two capacitor plates and the capacitor is again able to accept a charge. The active area of the capacitor is reduced in size by the damaged area each time a discharge occurs.

Wortman, J. J.↗
NASA NTRS1976

A description of the mechanical behavior of composite solid propellants based on molecular theory

Both the investigation and the representation of the stress-strain response (including rupture) of gum and filled elastomers can be based on a simple functional statement. Internally consistent experiments are used to sort out the effects of time, temperature, strain and crosslink density on gum rubbers. All effects are readily correlated and shown to be essentially independent of the elastomer when considered in terms of non-dimensionalized stress, strain and time. A semiquantitative molecular theory is developed to explain this result. The introduction of fillers modifies the response, but, guided by the framework thus provided, their effects can be readily accounted for.

Landel, R. F.↗
NASA NTRS1977

Gamma rays and supernova explosions

Thermal radiation associated with the explosion of supernovae is investigated. High temperature is required to produce copious gamma radiation of this sort. It appears that type 11 supernovae do not release much of their energy as gamma ray continuum radiation.

Arnett, W. D.↗
NASA NTRS1977

Introductory Remarks

Advanced transonic configurations, such as the supercritical wing, are inherently more sensitive to Reynolds number than earlier configurations because the pressure recovery gradients imposed on the boundary layer are generally steeper. The results of two-dimensional supercritical airfoil investigations and theoretical calculations show this effect. A technique for approximately simulating full-scale Reynolds number characteristics at present wind-tunnel Reynolds numbers for near-cruise conditions is described. The transition strip, which in the past has been located near the leading edge of the wing, is rearward so that the relative displacement thickness of the boundary layer at the trailing edge of the wing is the same as might be expected on a full-scale configuration with the transition near the leading edge. Two-dimensional wind-tunnel results indicate that the technique provides a very good simulation of airfoil characteristics at full-scale Reynolds number. The need for sorting the effects of Reynolds number and aeroelasticity, which can be done in the NTF, is also addressed.

Whitcomb, R.↗
NASA NTRS1976

Temperatures of the Martian surface and atmosphere - Viking observation of diurnal and geometric variations

Selected observations made with the Viking infrared thermal mapper after the first landing are reported. Atmospheric temperatures measured at the latitude of the Viking 2 landing site (48 deg N) over most of a Martian day reveal a diurnal variation of at least 15 K, with peak temperatures occurring near 2.2 hours after noon, implying significant absorption of sunlight in the lower 30 km of the atmosphere by entrained dust. The summit temperature of Arsia Mons varies by a factor of nearly two each day; large diurnal temperature variation is characteristic of the south Tharsis upland and implies the presence of low-thermal-inertia material. The thermal inertia of material on the floors of several typical large craters is found to be higher than for the surrounding terrain; this suggests that craters are somehow effective in sorting aeolian material. Brightness temperatures of the Viking 1 landing area decrease at large emissions angles; the intensity of reflected sunlight shows a more complex dependence on geometry than expected, implying atmospheric as well as surface scattering.

Kieffer, H. H.↗
NASA NTRS1977

Diameters of minor planets

The paper discusses the tremendous improvements in measurements of the asteroids since 1970, when polarimetric and radiometric methods began to replace the visual methods. A table is given which gives the sizes and albedos of 187 of the larger asteroids. When the asteroids are sorted according to albedo, they are seen to fall into two distinct groups: C-type, or carbonaceous, asteroids, with albedos of 2-5%, and a group of primarily stony or silicate bodies, the S asteroids, clustered around an albedo of 15%. The majority of the asteroids are seen to be very dark, and the maximum density in the asteroid belt must lie somewhere beyond 3.0 astronomical units.

Morrison, D.↗
NASA NTRS1977

Imaging natural materials with a quasi-microscope

A Viking lander camera with auxilliary optics mounted inside the dust post was evaluated to determine its capability for imaging the inorganic properties of granular materials. During mission operations, prepared samples would be delivered to a plate positioned within the camera's field of view and depth of focus. The auxiliary optics would then allow soil samples to be imaged with an 11 pm pixel size in the broad band (high resolution, black and white) mode, and a 33 pm pixel size in the multispectral mode. The equipment will be used to characterize: (1) the size distribution of grains produced by igneous (intrusive and extrusive) processes or by shock metamorphism, (2) the size distribution resulting from crushing, chemical alteration, or by hydraulic or aerodynamic sorting; (3) the shape and degree of grain roundness and surface texture induced by mechanical and chemical alteration; and (4) the mineralogy and chemistry of grains.

Bragg, S.↗
NASA NTRS1977

Mechanical processess affecting differentiation of protolunar material

Mechanisms prior to lunar formation are sought to account for the loss of volatiles, the depletion of iron, and the enrichment of plagioclase. Some of the same mechanisms are necessary to account for achondritic, stony-iron, and iron meteorites. Collisions seem marginally capable of providing the heat to accomplish the differentiation into iron, magnesian silicates, and plagioclase. Once this differentiation is accomplished, the subsequent mechanical history should have been sufficient to sort material according to composition in the protolunar circumterrestrial cloud. Effects operating include the correlation of body size with mechanical strength; the lesser ability of the cloud to trap the larger, denser infalling bodies; the more rapid drawing into the Earth of the larger moonlets; and the higher energy orbits for dominantly plagioclase smaller pieces broken off by collision.

Kaula, W. M.↗
NASA NTRS1978

A dual assault upon turbulence

All known calculation methods incorporate some sort of turbulence model to reduce the infinite hierarchy of equations, under Reynolds' averaging, to a finite set. All such models suffer from a certain ad hoc nature. A dual structure model was developed wherein the turbulence field is, somewhat arbitrarily, decomposed into large eddies which presumably are dominant contributors to the Reynolds' stress and small eddies which feed on the large eddies as these, in turn feed upon the average flow to gain their energy. These concepts have been developed into a dual approach, one extractive and the other predictive as outlined below.

Payne, F. R.↗