Subjective workload experienced during pursuit tracking as a function of available information
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Hauser, Jan R.↗
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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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Impacting Space Station Freedom design with operations and safety requirements - An availability process
The unusually long mission duration of Space Station Freedom leads to operations costs that have significant impacts on life-cycle cost relative to previous manned space programs. Maintaining an affordable program requires that operations costs be considered throughout the design process. An appropriate means of impacting the design with operations concerns is to specify requirements that ensure operational effectiveness when implemented. The Space Station Freedom Program has developed a process defining such requirements. It focuses on specifying functional profiles and allocating resources such that designers gain a better understanding of the operational envelope in which their systems must perform. This paper examines the details of the process, where it came from, and why it is effective.
Garegnani, Jerry J.↗
The global geochemistry of bomb-produced tritium - General circulation model compared to available observations and traditional interpretations
Observational evidence suggests that of the tritium produced during nuclear bomb tests that has already reached the ocean, more than twice as much arrived through vapor impact as through precipitation. In the present study, the Goddard Institute for Space Studies 8 x 10 deg atmospheric general circulation model is used to simulate tritium transport from the upper atmosphere to the ocean. The simulation indicates that tritium delivery to the ocean via vapor impact is about equal to that via precipitation. The model result is relatively insensitive to several imposed changes in tritium source location, in model parameterizations, and in model resolution. Possible reasons for the discrepancy are explored.
Koster, Randal D.↗
A model of Saturn's magnetic field based on all available data
A model of Saturn's magnetic field, called Saturn Pioneer Voyager (SPV), is developed on the basis of an analysis of three sets of data: those from the Pioneer 11, the Voyager 1, and the Voyager 2 magnetometers. It is shown that the SPV model fits the data observed between 1.3 and 8.0 Saturn radii from the planet's center with a 1.13 percent weighted rms average of the percent differences between the observed and modeled fields, which is substantially better than the fits yielded by any of the previous models.
Davis, Leverett, Jr.↗
Availability of hydrogen for lunar base activities
Hydrogen will be needed on a lunar base to make water for consumables, to provide fuel, and to serve as reducing agent in the extraction of oxygen from lunar minerals. The abundance and distribution of solar wind implanted hydrogen were studied. Hydrogen was found in all samples studied with concentrations varying widely depending on soil maturity, grain size, and mineral composition. Seven cores returned from the moon were studied. Although hydrogen was implanted in the upper surface layer of the regolith, it was found throughout the cores due to micrometeorite reworking of the soil.
Bustin, Roberta↗
Stirling engine: Available tools for long-life assessment
A review is presented for the durability approaches applicable to long-time life assessment of Stirling engine hot-section components. The crucial elements are experimental techniques for generating long-time materials property data (both monotonic and cyclic flow and failure properties); analytic representations of slow strain rate material stress-strain response characteristics (monotonic and cyclic constitutive relations) at high temperatures and low stresses and strains; analytic creep-fatigue-environmental interaction life prediction methods applicable to long lifetimes at high temperatures and small stresses and strains; and experimental verification of life predictions. Long-lifetime design criteria for materials of interest are woefully lacking. Designing against failures due to creep, creep-rupture, fatigue, environmental attack, and creep-fatigue-environmental interaction will require considerable extrapolation. Viscoplastic constitutive models and time-temperature parameters will have to be calibrated for the hot-section materials of interest. Analysis combined with limited verification testing in a short-time regime will be required to build confidence in long-lifetime durability models.
Halford, Gary R.↗
Study of the available finite element software packages at KSC
The interaction among the three finite element software packages, SDRCI/I-DEAS, MSC/NASTRAN, and I/FEM, used at NASA, Kennedy Space Center is addressed. The procedures for using more than one of these application software packages to model and analyze a structure design are discussed. Design and stress analysis of a solid rocket booster fixture is illustrated by using four different combinations of the three software packages. Their results are compared and show small yet acceptable differences.
Lu, Chu-Ho↗
Water on Mars: Volatile history and resource availability
The existence of water on Mars is undisputed today. Measurements of atmospheric water vapor have shown that the abundance varies with location and season in a systematic way which depends on processes of exchange with the polar caps, regolith, and atmosphere. Channels, which give the appearance of having been carved by water or of having had water involved in their formation, appear in various locations on the surface; some were formed by catastrophic outflow of water from beneath the surface, while others form valley networks which give the appearance of having formed over long periods of time primarily early in the planet's history. The north polar residual cap consists of water ice, possibly containing an amount of water equivalent to a global layer several tens of meters thick. Finally, water is observed within the regolith, as adsorbed water or as water of hydration.
Jakosky, Bruce M.↗
Effectivity of atmospheric electricity on launch availability
Thunderstorm days at KSC; percentage of frequency of thunderstorms (1957-1989); effect of lightning advisory on ground operations; Shuttle launch history; Shuttle launch weather history; applied meteorology unit; and goals/operational benefits. This presentation is represented by viewgraphs.
Ernst, John A.↗
Ocean color - Availability of the global data set
The use of satellite observations of ocean color to provide reliable estimates of marine phytoplankton biomass on synoptic scales is examined. An overview is given of the Coastal Zone Color Scanner data processing system. The archiving and distribution of ocean color data are discussed, and NASA-sponsored archive sites are listed.
Feldman, Gene↗
Iron availability, nitrate uptake, and exportable new production in the subarctic Pacific
This paper presents a critique of experimental data and papers by Martin et al. (1989, 1990), who suggested that the phytoplankton growth is iron-limited and that, small additions of iron to large subarctic ocean areas might be a way of removing significant amounts of atmospheric CO2 by increasing phytoplancton growth. Data are presented to show that, in the summer of 1987, the phytoplankton assemblage as a whole was not iron limited, as measured by the bulk removal of nitrate or by the increase of chlorophyll. It is suggested that grazing normally prevents the phytoplankton from reaching concentrations that reduce the iron (and nitrate) to levels that depress division rates drastically.
Banse, Karl↗
A new spherical model for computing the radiation field available for photolysis and heating at twilight
Accurate computation of atmospheric photodissociation and heating rates is needed in photochemical models. These quantities are proportional to the mean intensity of the solar radiation penetrating to various levels in the atmosphere. For large solar zenith angles a solution of the radiative transfer equation valid for a spherical atmosphere is required in order to obtain accurate values of the mean intensity. Such a solution based on a perturbation technique combined with the discrete ordinate method is presented. Mean intensity calculations are carried out for various solar zenith angles. These results are compared with calculations from a plane parallel radiative transfer model in order to assess the importance of using correct geometry around sunrise and sunset. This comparison shows, in agreement with previous investigations, that for solar zenith angles less than 90 deg adequate solutions are obtained for plane parallel geometry as long as spherical geometry is used to compute the direct beam attenuation; but for solar zenith angles greater than 90 deg this pseudospherical plane parallel approximation overstimates the mean intensity.
Dahlback, Arne↗
Some potential impacts of lunar oxygen availability on near-earth space transportation
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Driggers, Gerald W.↗
Monthly mean global satellite data sets available in CCM history tape format
Satellite data for climate monitoring have become increasingly important over the past decade, especially with increasing concern for inadvertent antropogenic climate change. Although most satellite based data are of short record, satellites can provide the global coverage that traditional meteorological observations network lack. In addition, satellite data are invaluable for the validation of climate models, and they are useful for many diagnostic studies. Herein, several satellite data sets were processed and transposed into 'history tape' format for use with the Community Climate Model (CCM) modular processor. Only a few of the most widely used and best documented data sets were selected at this point, although future work will expand the number of data sets examined as well as update the archived data sets. An attempt was made to include data of longer record and only monthly averaged data were processed. For studies using satellite data over an extended period, it is important to recognize the impact of changes in instrumentation, drift in instrument calibration, errors introduced by retrieval algorithms and other sources of errors such as those resulting from insufficient space and/or time sampling.
Hurrell, James W.↗
Reliability and availability modeling of coupled communication networks - A simplified modeling approach
The network-complexity of LANs and of LANs that are interconnected by bridges and routers poses a challenging reliability-modeling problem. The present effort toward these problems' solution attempts to simplify them by reducing their number of states through truncation and state merging, as suggested by Shooman and Laemmel (1990). Through the use of state merging, it becomes possible to reduce the Bateman-Cortes 161 state model to a two state model with a closed-form solution. In the case of coupled networks, a technique which allows for problem-decomposition must be used.
Shooman, Martin L.↗
Minimizing selective availability error on satellite and ground global positioning system measurements
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Wu, S. C.↗
Availability of hydrogen for lunar base activities
Hydrogen will be needed on a lunar base to make water for consumables, to provide fuel, and to serve as a reducing agent in the extraction of oxygen from lunar minerals. This study was undertaken in order to learn more about the abundance and distribution of solar-wind-implanted hydrogen. Hydrogen was found in all samples studied, with concentrations, varying widely depending on soil maturity, grain size, and mineral composition. Seven cores returned from the Moon were studied. Although hydrogen was implanted in the upper surface layer of the regolith, it was found throughout the cores due to micrometeorite reworking of the soil.
Bustin, Roberta↗
Resource availability at Taurus-Littrow
Early lunar technologies will probably use a common lunar material as ore. They will be robust to minor fluctuations in feedstock composition and will not require appreciable feedstock beneficiation such as rock grinding or mineral concentration. Technologies using unprocessed soil and indifferent to its composition will have the advantage. Nevertheless, the size and grade of the ore body must be confirmed for even the most indiscriminate process. Simple uses such as heaping unprocessed lunar soil for thermal insulation or radiation shielding onto a habitat require that we know the depth of the regolith, the size distributions of its soils, the locations of large boulders, and the ease of excavation. Costs of detailed site surveys trade against restrictions on site selection and conservative engineering design to accommodate unknown conditions of a poorly explored site. Given the above considerations, we consider briefly some abundant lunar materials, their proposed uses, and technologies for their preparation, with particular attention to the Taurus-Littrow site.
Haskin, Larry A.↗