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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Interplanetary magnetic-field variations and substorm activity.

A fine time-scale study of interplanetary magnetic field (IMF) variations and auroral-zone magnetograms during active and moderately active days show that the time delay between the southward turning of the IMF and the first sign of a negative magnetic bay is typically less than 15 min. During the moderately active period, 88% of all substorms were associated with southward interplanetary magnetic fields. Conversely, 80% of all large southward IMF events were associated with auroral-zone negative bays; during some events, however, magnetic bays could not be found, even by using high-latitude stations. It is concluded that the main mechanism for the triggering of magnetospheric substorms is the southward turning of the IMF.

Tsurutani, B. T.↗
NASA NTRS1972

Structural active cooling applications for the Space Shuttle.

Analytic and experimental studies have been conducted to evaluate a number of active cooling approaches to structural thermal protection for the Space Shuttle. The primary emphasis was directed toward the thermal protection system. Trade study results are presented for various heat shield material and TPS arrangements. Both metallic and reusable surface insulation (RSI) concepts were considered. Active systems heat sinks consisted of hydrogen, phase change materials, and expendable water. If consideration is given only to controlling the surface temperature, passive TPS was found to provide the most efficient system. Use of active cooling which incorporates some interior temperature control made the thermally less efficient RSI system more attractive.

Masek, R. V.↗
NASA NTRS1972

Correlation of irradiation data using activation fluences and irradiation temperature.

A new method of correlating radiation damage data is tested using actual measured data taken from the open literature. This method, the activation fluence method, was found to be as accurate as other contemporary models with which it was compared. The new method also has several advantages over the other methods. The method employs a new entity, the activation fluence (time-integrated specific activation rate), as the independent variables in a regression model. Temperature at which the irradiation takes place is also a variable. Although the method was tested for a specific type of damage (change in nil-ductility transition temperature for A302-B steel) it has no inherent restrictions and is limited only by the imagination of the user.

Lynch, J. H.↗
NASA NTRS1972

Enzyme activity in terrestrial soil in relation to exploration of the Martian surface

An exploration was made of enzyme activities in soil, including abundance, persistence and localization of these activities. An attempt was made to develop procedures for the detection and assaying of enzymes in soils suitable for presumptive tests for life in planetary soils. A suitable extraction procedure for soil enzymes was developed and measurements were made of activities in extracts in order to study how urease is complexed in soil organic matter. Mathematical models were developed, based on enzyme action and microbial growth in soil, for rates of oxidation of nitrogen as nitrogen compounds are moved downward in soil by water flow. These biogeochemical models should be applicable to any percolating system, with suitable modification for special features, such as oxygen concetrations, and types of hydrodynamic flow.

Ardakani, M. S.↗
NASA NTRS1972

Evaluation of feasibility of mapping seismically active faults in Alaska

The author has identified the following significant results. A previously unmapped seismically active fault has been identified in south-central Alaska on the basis of ERTS-1 imagery. It can be traced for at least 120 km. An unmapped fault was found on the northwest flank of Mt. Sanford that is apparently a reverse fault. A large scale, seismically active fracture system has been identified in central Alaska on the basis of MSS imagery. The system consists of two sets of fractures which intersect at an angle of about 55 degrees. The dominant feature of the system is the Minook Creek fault, on which an earthquake of magnitude 6.5 occurred on October 29, 1968. A possible related feature is a 60 km long lineament near the Toklat River north of Mt. McKinley. These areas are all moderately seismically active. Focal mechanism studies of the 1968 earthquake revealed that left-lateral displacement had occurred on the Minook Creek fault due to compressive stress. A similarly oriented direction of compressive stress could be responsible for the entire fracture system.

Gedney, L. D.↗
NASA NTRS1972

Design and evaluation of an electrohydraulic servoactuator using active standby redundancy

The application is described of active standby redundancy techniques to a large electrohydraulic servoactuator. The advantages and limitations of active standby redundancy are identified. Special areas of investigation during the development test phase of the program were the evaluation of output transients as a function of channel switching and the nuisance switching characteristics of the system. The feasibility of constructing large electrohydraulic servoactuators using active standby redundancy was successfully demonstrated. In particular the stability and predictability of a properly designed hydromechanical failure detector was demonstrated.

Anderson, R. L.↗
NASA NTRS1973

Evaluation of feasibility of mapping seismically active faults in Alaska

The author has identified the following significant results. ERTS-1 imagery is proving to be exceptionally useful in delineating structural features in Alaska which have never been recognized on the ground. Previously unmapped features such as seismically active faults and major structural lineaments are especially evident. Among the more significant results of this investigation is the discovery of an active strand of the Denali fault. The new fault has a history of scattered activity and was the scene of a magnitude 4.8 earthquake on October 1, 1972. Of greater significance is the disclosure of a large scale conjugate fracture system north of the Alaska Range. This fracture system appears to result from compressive stress radiating outward from around Mt. McKinley. One member of the system was the scene of a magnitude 6.5 earthquake in 1968. The potential value of ERTS-1 imagery to land use planning is reflected in the fact that this earthquake occurred within 10 km of the site which was proposed for the Rampart Dam, and the fault on which it occurred passes very near the proposed site for the bridge and oil pipeline crossing of the Yukon River.

Gedney, L. D.↗
NASA NTRS1973

Evaluation of radioisotope tracer and activation analysis techniques for contamination monitoring in space environment simulation chambers

Radioisotope measurement techniques and neutron activation analysis are evaluated for use in identifying and locating contamination sources in space environment simulation chambers. The alpha range method allows the determination of total contaminant concentration in vapor state and condensate state. A Cf-252 neutron activation analysis system for detecting oils and greases tagged with stable elements is described. While neutron activation analysis of tagged contaminants offers specificity, an on-site system is extremely costly to implement and provides only marginal detection sensitivity under even the most favorable conditions.

Smathers, J. B.↗
NASA NTRS1973

Geomagnetic activity at sector boundaries.

The relation between the rise in geomagnetic activity at sector boundaries and the south-pointing component of the interplanetary field is investigated. It is shown that, in 1968, an increase in the average southward component occurred when the sector boundary was crossed. This increase can account for the initial increase in magnetic activity. However, the southward component rapidly fell to its preboundary levels, while geomagnetic activity remained elevated for at least a day. This observation suggests that either the magnetosphere took of the order of a day to relax or energy continued to be fed into the magnetosphere at an enhanced rate during the postboundary period. A possible cause of the increase in southward fields at sector boundaries is discussed.

Hirshberg, J.↗
NASA NTRS1973

Analysis and synthesis of distributed-lumped-active networks by digital computer

The use of digital computational techniques in the analysis and synthesis of DLA (distributed lumped active) networks is considered. This class of networks consists of three distinct types of elements, namely, distributed elements (modeled by partial differential equations), lumped elements (modeled by algebraic relations and ordinary differential equations), and active elements (modeled by algebraic relations). Such a characterization is applicable to a broad class of circuits, especially including those usually referred to as linear integrated circuits, since the fabrication techniques for such circuits readily produce elements which may be modeled as distributed, as well as the more conventional lumped and active ones.

Source record↗
NASA NTRS1974

Fibrinolysis and fibrinogenolysis on magnetically-active days

On magnetically-active days, activation of fibrinolysis and fibrinogenolysis is observed. The increase in fibrinolysis and fibrinogenolysis begins on the day of the onset of a magnetic storm, reaching a maximum in 24 hours. Activation is higher on days with magnetic storms with a sudden onset and a C index of 1.5-2.0.

Marchenko, V. I.↗
NASA NTRS1974

Laboratory demonstration model: Active cleaning technique device

The technique which utilizes exposure to a plasma to remove contaminants from a surface was incorporated into a laboratory model which demonstrates active cleaning by both plasma cleaning and ion sputtering modes of operation. The development phase is reported and includes discussion of the plasma tube configuration, device design, and performance tests. A general description of the active cleaning device is provided which includes information on the main power/plasma discharge sensors, and the power, gas supply, and ion accelerator systems. Development of the active cleaning species at high vacuum conditions is described and results indicate that plasma cleaning occurs in the region of a visible plume which extends from the end of the plasma tube. Recommendations are made for research to determine the plasma cleaning mechanism and the plasma species responsible for the cleaning, as well limitations on the type of contaminants that can be removed.

Shannon, R. L.↗
NASA NTRS1974

Possible relationships between solar activity and atmospheric constituents

The large body of data on solar variations and atmospheric constituents collected between 1902 and 1953 by the Astrophysical Observatory of the Smithsonian Institution (APO) is examined. Short term variations in amounts of atmospheric aerosols and water vapor due to seasonal changes, volcanic activity, air pollution, and frontal activity are discussed. Preliminary evidence indicates that increased solar activity is at times associated with a decrease in attenuation due to airborne particulates.

Roosen, R. G.↗
NASA NTRS1974

Some problems in coupling solar activity to meteorological phenomena

The development of a theory of coupling of solar activity to meteorological phenomena has to date foundered on the two difficulties of (1) devising a mechanism that can modify the behavior of the troposphere while employing only a negligible amount of energy compared with the energy necessary to drive the normal meteorological system; and (2) determining how such a mechanism can effectively couple some relevant magnetospheric process into the troposphere in such a way as to influence the weather. A clue to the nature of the interaction between the weather and solar activity might be provided by the fact that most solar activity undergoes a definite 11-year cycle, while meteorological phenomena undergo either no closely correlated variation, or an 11-year variation, or a 22-year variation.

Dessler, A. J.↗
NASA NTRS1974

Space shuttle/food system study. Volume 2, Appendix A: Active heating system-screening analysis. Appendix B: Reconstituted food heating techniques analysis

Technical data are presented which were used to evaluate active heating methods to be incorporated into the space shuttle food system design, and also to evaluate the relative merits and penalties associated with various approaches to the heating of rehydrated food during space flight. Equipment heating candidates were subject to a preliminary screening performed by a selection rationale process which considered the following parameters; (1) gravitational effect; (2) safety; (3) operability; (4) system compatibility; (5) serviceability; (6) crew acceptability; (7) crew time; (8) development risk; and (9) operating cost. A hot air oven, electrically heated food tray, and microwave oven were selected for further consideration and analysis. Passive, semi-active, and active food preparation approaches were also studied in an effort to determine the optimum method for heating rehydrated food. Potential complexity, cost, vehicle impact penalties, and palatability were considered in the analysis. A summary of the study results is provided along with cost estimates for each of the potential sytems

Source record↗
NASA NTRS1974

Relative desirability of leisure activities and work parameters in a simulation of isolated work stations

The kinds of activities that are attractive to man in long duration isolation are delineated considering meaningful work as major activity and a choice of leisure/living provisions. The dependent variables are the relative distribution between various work, leisure, and living activities where external constraints on the subject's freedom of choice are minimized. Results indicate that an average of at least five hours per day of significant meaningful work is required for satisfactory enjoyment of the situation; most other parameters of the situation have less effects on overall performance and satisfaction

Sullins, W. R., Jr.↗
NASA NTRS1974

Temperature dependence of emission measure in solar X-ray plasmas. 1: Non-flaring active regions

X-ray and ultraviolet line emission from hot, optically thin material forming coronal active regions on the sun may be described in terms of an emission measure distribution function, Phi (T). A relationship is developed between line flux and Phi (T), a theory which assumes that the electron density is a single-valued function of temperature. The sources of error involved in deriving Phi (T) from a set of line fluxes are examined in some detail. These include errors in atomic data (collisional excitation rates, assessment of other mechanisms for populating excited states of transitions, element abundances, ion concentrations, oscillator strengths) and errors in observed line fluxes arising from poorly - known instrumental responses. Two previous analyses are discussed in which Phi (T) for a non-flaring active region is derived. A least squares method of Batstone uses X-ray data of low statistical significance, a fact which appears to influence the results considerably. Two methods for finding Phi (T) ab initio are developed. The coefficients are evaluated by least squares. These two methods should have application not only to active-region plasmas, but also to hot, flare-produced plasmas.

Phillips, K. J. H.↗
NASA NTRS1973

Shuttle active thermal control system development testing. Volume 6: Water ejector plume tests

Results are given of vacuum testing of nozzles designed to eject water vapor away from the space shuttle to prevent contamination of the spacecraft surfaces and payload. The water vapor is generated by an active cooling system which evaporates excess fuel cell water to supplement a modular radiator system (MRS). The complete heat rejection system including the MRS, flash evaporator or sublimator and nozzle were first tested to demonstrate the system operational characteristics. The plume tests were performed in two phases and the objectives of this test series were: (1) to determine the effectiveness of a supersonic nozzle and a plugged nozzle in minimizing impingement upon the spacecraft of water vapor exhausted by an active device (flash evaporator or sublimator); and (2) to obtain basic data on the flow fields of exhaust plumes generated by these active devices, both with and without nozzles installed.

Mcginnis, F. K.↗