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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Discrete component bonding and thick film materials study

The results are summarized of an investigation of discrete component bonding reliability and a fundamental study of new thick film resistor materials. The component bonding study examined several types of solder bonded components with some processing variable studies to determine their influence upon bonding reliability. The bonding reliability was assessed using the thermal cycle: 15 minutes at room temperature, 15 minutes at +125 C 15 minutes at room temperature, and 15 minutes at -55 C. The thick film resistor materials examined were of the transition metal oxide-phosphate glass family with several elemental metal additions of the same transition metal. These studies were conducted by preparing a paste of the subject composition, printing, drying, and firing using both air and reducing atmospheres. The resulting resistors were examined for adherence, resistance, thermal coefficient of resistance, and voltage coefficient of resistance.

Kinser, D. L.↗
NASA NTRS1975

The use of LANDSAT-1 imagery for water quality studies in southern Scandinavia

The possibilities of using LANDSAT-1 images for environmental studies, with special references to water quality studies, were investigated by selecting test areas in southern Scandinavia. The MSS images of different bands are compared under the magnification of an Interpretoscope and densitometric analyses are performed in a Schnell-photometer. The possibility of tracing pollution plumes is studied in the Oresund outside Copenhagen. The effect of different sewers and the circulation of the polluted water is analyzed in various situations. The variation in reflectivity of a great number of lakes in South and Middle Sweden is studied by means of densitometric analyses and significant regional differences are found. The correlation with in situ measurements of water quality (turbidity and secchi disc transparency) of the sampled lakes (made by the National Swedish Environment Protection Board) is fairly good.

Hellden, U.↗
NASA NTRS1976

A numerical comparison of discrete Kalman filtering algorithms: An orbit determination case study

The numerical stability and accuracy of various Kalman filter algorithms are thoroughly studied. Numerical results and conclusions are based on a realistic planetary approach orbit determination study. The case study results of this report highlight the numerical instability of the conventional and stabilized Kalman algorithms. Numerical errors associated with these algorithms can be so large as to obscure important mismodeling effects and thus give misleading estimates of filter accuracy. The positive result of this study is that the Bierman-Thornton U-D covariance factorization algorithm is computationally efficient, with CPU costs that differ negligibly from the conventional Kalman costs. In addition, accuracy of the U-D filter using single-precision arithmetic consistently matches the double-precision reference results. Numerical stability of the U-D filter is further demonstrated by its insensitivity of variations in the a priori statistics.

Thornton, C. L.↗
NASA NTRS1975

Acoustical modeling study of the open test section of the NASA Langley V/STOL wind tunnel

An acoustic model study was carried out to identify effective sound absorbing treatment of strategically located surfaces in an open wind tunnel test section. Also an aerodynamic study done concurrently, sought to find measures to control low frequency jet pulsations which occur when the tunnel is operated in its open test section configuration. The acoustical modeling study indicated that lining of the raised ceiling and the test section floor immediately below it, results in a substantial improvement. The aerodynamic model study indicated that: (1) the low frequency jet pulsations are most likely caused or maintained by coupling of aerodynamic and aeroacoustic phenomena in the closed tunnel circuit, (2) replacing the hard collector cowl with a geometrically identical but porous fiber metal surface of 100 mks rayls flow resistance does not result in any noticable reduction of the test section noise caused by the impingement of the turbulent flow on the cowl.

Ver, I. L.↗
NASA NTRS1976

Lunar seismic profiling experiment natural activity study

The Lunar Seismic Experiment Natural Activity Study has provided a unique opportunity to study the high frequency (4-20 Hz) portion to the seismic spectrum on the moon. The data obtained from the LSPE was studied to evaluate the origin and importance of the process that generates thermal moonquakes and the characteristics of the seismic scattering zone at the lunar surface. The detection of thermal moonquakes by the LSPE array made it possible to locate the sources of many events and determine that they are definitely not generated by astronaut activities but are the result of a natural process on the moon. The propagation of seismic waves in the near-surface layers was studied in a qualitative manner. In the absence of an adequate theoretical model for the propagation of seismic waves in the moon, it is not possible to assign a depth for the scattering layer. The LSPE data does define several parameters which must be satisfied by any model developed in the future.

Duennebier, F. K.↗
NASA NTRS1976

A temperature dependence kinetics study of the reactions of Cl/2-P-3/2/ with O3, CH4, and H2O2

The temperature dependence of two chlorine atom reactions of considerable fundamental importance to stratospheric chemistry was studied using the technique of flash photolysis-resonance fluorescence. The reactions of interest were: (1) Cl + O3 yields ClO + O2 studied at 220-350 K, and (2) Cl + CH4 yields CH3 + HCl studied at 218-401 K. In addition, the reaction Cl + H2O2 yields HCl + HO2 was studied at 300 K. The corresponding rate constants are provided for the three reactions. The new rate data implies the need to revise downward by a factor of 2.4-3 the magnitude of the ozone perturbation due to the presence of ClO/x/ species in the stratosphere, predicted by earlier model calculations.

Watson, R.↗
NASA NTRS1976

Numerical Studies of Three-dimensional Breakdown in Trailing Vortex Wakes

Finite element, three dimensional relaxation methods are used to calculate the development of vortex wakes behind aircraft for a considerable downstream distance. The inclusion of a self-induction term in the solution, dependent upon local curvature and vortex core radius, permits calculation of finite lifetimes for systems for which infinite life would be predicted two dimensionally. The associated computer program is described together with single-pair, twin-pair, and multiple-pair studies carried out using it. It is found, in single-pair studies, that there is a lower limit to the wavelengths at which the Crow-type of instability can occur. Below this limit, self-induction effects cause the plane of the disturbance waves to rotate counter to the vortex direction. Self induction in two dimensionally generated twin spiral waves causes an increase in axial length which becomes more marked with decreasing initial wavelength. The time taken for vortex convergence toward the center plane is correspondingly increased. The limited parametric twin-pair study performed suggests that time-to-converge increases with increasing flap span. Limited studies of Boeing 747 configurations show correct qualitative response to removal of the outer flap and to gear deployment, as compared with wind tunnel and flight test experience.

Evans, P. F.↗
NASA NTRS1976

Payload specialist station study. Volume 1: Executive summary

The results of the Payload Specialist Station study are summarized. An optimum aft flight deck (AFD) controls and displays (C&D) configuration concept for payload operations within the Shuttle Orbiter were studied. The concept derived satisfied the large majority of identified payload C&D requirements through the 1980's, was cost effective, and utilized existing technology. The results are directly applicable to Phase C/D activities. Programmatic analyses, phase C/D program definition and schedules, and economic analyses were completed; and estimated phase C/D costs were identified. The AFD control and display concept was defined via panel layouts, CEI specifications, and programmatics for phase C/D. The study plan included the following six phases: (1) derive control and display requirements; (2) perform functional analyses; (3) perform system synthesis; (4) perform trade studies; (5) perform preliminary design; and (6) provide programmatics.

Source record↗
NASA NTRS1976

Payload specialist station study. Volume 2, part 1: Preliminary design document

The details of six tasks of the payload Specialist Station study are discussed: (1) derive payload control and display requirements; (2) perform functional analyses; (3) perform system synthesis; (4) perform trade studies; (5) perform preliminary design; and (6) provide data format. Functional analysis diagrams were developed for the study payloads. These diagrams presented the payload's functional activities flow based on the six mission phases established. These phases are: (1) launch, ascent, orbit insertion; (2) on-orbit checkout and activation; (3) on-orbit operation; (4) deployment/retrieval; (5) on-orbit deactivation; and (6) descent, landing, post-landing. To perform system synthesis the widest variety of available hardware and software, as individual pieces of equipment and as systems, was investigated. The intent was to synthesize a complete AFD system or systems which could accommodate the range of requirements identified for the study missions.

Source record↗
NASA NTRS1976

A comparison between conventional and LANDSAT based hydrologic modeling: The Four Mile Run case study

Models designed to support the hydrologic studies associated with urban water resources planning require input parameters that are defined in terms of land cover. Estimating the land cover is a difficult and expensive task when drainage areas larger than a few sq. km are involved. Conventional and LANDSAT based methods for estimating the land cover based input parameters required by hydrologic planning models were compared in a case study of the 50.5 sq. km (19.5 sq. mi) Four Mile Run Watershed in Virginia. Results of the study indicate that the LANDSAT based approach is highly cost effective for planning model studies. The conventional approach to define inputs was based on 1:3600 aerial photos, required 110 man-days and a total cost of $14,000. The LANDSAT based approach required 6.9 man-days and cost $2,350. The conventional and LANDSAT based models gave similar results relative to discharges and estimated annual damages expected from no flood control, channelization, and detention storage alternatives.

Ragan, R. M.↗
NASA NTRS1977

Preliminary design study of advanced multistage axial flow core compressors

A preliminary design study was conducted to identify an advanced core compressor for use in new high-bypass-ratio turbofan engines to be introduced into commercial service in the 1980's. An evaluation of anticipated compressor and related component 1985 state-of-the-art technology was conducted. A parametric screening study covering a large number of compressor designs was conducted to determine the influence of the major compressor design features on efficiency, weight, cost, blade life, aircraft direct operating cost, and fuel usage. The trends observed in the parametric screening study were used to develop three high-efficiency, high-economic-payoff compressor designs. These three compressors were studied in greater detail to better evaluate their aerodynamic and mechanical feasibility.

Wisler, D. C.↗
NASA NTRS1975

Aviation system modeling study and alternatives

The Aviation System Modeling Study was directed toward two primary goals: an improved understanding of the U.S. aviation system, and technology. There are three major categories into which the individual study efforts may be subdivided. These three categories are: special issue studies, task studies, and data base development.

Source record↗
NASA NTRS1978

Multi-KW dc distribution system technology research study

The Multi-KW DC Distribution System Technology Research Study is the third phase of the NASA/MSFC study program. The purpose of this contract was to complete the design of the integrated technology test facility, provide test planning, support test operations and evaluate test results. The subjet of this study is a continuation of this contract. The purpose of this continuation is to study and analyze high voltage system safety, to determine optimum voltage levels versus power, to identify power distribution system components which require development for higher voltage systems and finally to determine what modifications must be made to the Power Distribution System Simulator (PDSS) to demonstrate 300 Vdc distribution capability.

Dawson, S. G.↗
NASA NTRS1978

Laboratory and community studies of aircraft noise effects

The noise effects programs objective is to develop aircraft noise criteria and noise reduction methods for achieving greater community and passenger acceptance of air transportation systems. The approach consists of laboratory tests to subjectively evaluate the properties of aircraft-generated noise that are responsible for causing annoyance and field surveys to study the broader problems of community and passenger acceptability. The program is organized into two major thrusts: community acceptance and passenger acceptance. The community acceptance includes subjective response studies of single and multiple aircraft overflights as well as longer term community noise exposure. Emphasis is on the development of units and indices which accurately quantify annoyance. The passenger acceptance program includes studies to determine acceptably levels of interior noise and vibration for speech intelligibility and comfort of crew and passengers. Selected results from several recent studies are presented to indicate the nature, scope, and methods of the research program.

Stephens, D. G.↗
NASA NTRS1978

European Space Agency studies of the solar probe

The feasibility and scientific objectives of a solar probe were studied by a Mission Definition Group in 1975 and 1976. The orbit analysis program was developed and an extended study of the orbit analysis was done in 1977. The results of these studies are in the Report of the Mission Definition Study (1976) and an E.S.O.C. report (1978), and the reader is referred to these sources for greater details. In this report, only brief discussion on mission concept and objectives, satellite design, orbit, orbit analysis, are presented.

Roxburgh, I. W.↗
NASA NTRS1975

Lunar Science Conference, 6th, Houston, Tex., March 17-21, 1975, Proceedings. Volume 1 - Mineralogical and petrological studies. Conference sponsored by NASA and Lunar and Planetary Institute

This book represents a conference whose main topics include: petrological studies of lunar samples, studies of anorthositic rocks, studies of soils and breccias, lunar minerology, petrologic studies of lunar problems, and petrogenetic models of lunar evolution. Attention is given to samples obtained from the Apollo 16 and 17 missions.

Merrill, R. B.↗
NASA NTRS1975

Consortium studies of matrix of light gray breccia 73215

A description is presented of the preliminary results of interdisciplinary studies of matrix samples. The significance of the 73215 studies is considered and the relationship of 73215 to other Apollo 17 highland breccias is discussed. According to a tentative hypothesis 73215 is an aggregate of fragments plus melt generated in a very large impact, possibly the Serenitatis basin-forming event. If this is correct, studies of this sample will make it possible to date the Serenitatis event and will provide an insight into the breccia-forming processes associated with such events. Studies of the clasts in the breccia will provide an opportunity to formulate a partial characterization of the preimpact source terrain. An investigation of the deep lunar crust might perhaps also be possible.

James, O. B.↗
NASA NTRS1978

A feasibility study of orbiter flight control experiments

The results of a feasibility study of orbiter flight control experiments performed are summarized. Feasibility studies were performed on a group of 14 experiments selected from a candidate list of 35 submitted to the study contractor by the flight control community. Concepts and requirements were developed for the 14 selected experiments and they were ranked on a basis of technical value, feasibility, and cost. It was concluded that all the selected experiments can be considered as potential candidates for the Orbiter Experiment program, which is being formulated for the Orbiter Flight Tests and subsequent operational flights, regardless of the relative ranking established during the study. None of the selected experiments has significant safety implications and the cost of most was estimated to be less than $200K.

Geissler, W. H.↗