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At least 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Phased array-fed antenna configuration study

The scope of this contract entails a configuration study for a phased array fed transmit antenna operating in the frequency band of 17.7 to 20.2 GHz. This initial contract provides a basis for understanding the design limitations and advantages of advanced phased array and cluster feeds (both utilizing intergral MMIC modules) illuminating folded reflector optics (both near field and focused types). Design parametric analyses are performed utilizing as constraints the objective secondary performance requirements of the Advanced Communications Technology Satellite (Table 1.0). The output of the study provides design information which serves as a data base for future active phased array fed antenna studies such as detailed designs required to support the development of a ground tested breadboard. In general, this study is significant because it provides the antenna community with an understanding of the basic principles which govern near field phased scanned feed effects on secondary reflector system performance. Although several articles have been written on analysis procedures and results for these systems, the authors of this report have observed phenomenon of near field antenna systems not previously documented. Because the physical justification for the exhibited performance is provided herein, the findings of this study add a new dimension to the available knowledge of the subject matter.

Crosswell, W. F.↗
NASA NTRS1983

Interagency Array Study Report

The interagency array study that was convened in early 1982 to determine which of the world's large radio reception facilities might be feasibly and beneficially enlisted to help support the Voyager encounters at Uranus (1986) and Neptune (1989), and also to examine the future for such similar events and options as might appear is discussed. A similar but more specific study of the Parkes Radio Telescope at Uranus Encounter was just then being completed with a strong positive recommendation, and formed the foundation of the broader study. The approach, driving considerations, and outcome of the interagency array study are discussed. The recommendations of the study team concentrated upon the Voyager Encounters are: specifically to develop Parkes for the Uranus Encounter, while pursuing related Advanced Systems development work with the Owens Valley Radio Observatory, and to seek support for the Neptune Encounter from Parkes, the Very Large Array near Socorro, Mexico, and the Japanese institute of Space and Astronautical Sciences 64 meter station.

Wayland, J. W.↗
NASA NTRS1983

Electromagnetic induction studies

Recent developments in electromagnetic induction studies of the lithosphere and the asthenosphere are reviewed. Attention is given to geoelectrical studies of active tectonic areas in terms of the major zones of crustal extension, the basin and range province along western regions of North America, and the Rio Grande rift. Studies have also been performed of tectonic activity around Iceland, the Salton Trough and Cerro Prieto, and the subduction zones of the Cascade Mountains volcanic belt, where magnetotelluric and geomagnetic variation studies have been done. Geomagnetic variations experiments have been reported in the Central Appalachians, and submarine electromagnetic studies along the Juan de Fuca ridge. Controlled source electromagnetic and dc resistivity investigations have been carried out in Nevada, Hawaii, and in the Adirondacks Mountains. Laboratory examinations on the conductivity of representative materials over a broad range of temperature, pressure, and chemistry are described.

Hermance, J. F.↗
NASA NTRS1983

Advanced Platform Systems Technology study. Volume 3: Supporting data

The overall study effort proceeded from the identification of 106 technology topics to the selection of 5 for detail trade studies. The technical issues and options were evaluated through the trade process. Finally, individual consideration was given to costs and benefits for the technologies identified for advancement. Eight priority technology items were identified for advancement. Supporting data generated during the trade selection and trade study process were presented. Space platform requirements, trade study and cost benefits analysis, and technology advancement planning are advanced. The structured approach used took advantage of a number of forms developed to ensure that a consistent approach was employed by each of the diverse specialists that participated. These forms were an intrinsic part of the study protocol.

Source record↗
NASA NTRS1984

Space station automation and robotics study. Operator-systems interface

This is the final report of a Space Station Automation and Robotics Planning Study, which was a joint project of the Boeing Aerospace Company, Boeing Commercial Airplane Company, and Boeing Computer Services Company. The study is in support of the Advanced Technology Advisory Committee established by NASA in accordance with a mandate by the U.S. Congress. Boeing support complements that provided to the NASA Contractor study team by four aerospace contractors, the Stanford Research Institute (SRI), and the California Space Institute. This study identifies automation and robotics (A&R) technologies that can be advanced by requirements levied by the Space Station Program. The methodology used in the study is to establish functional requirements for the operator system interface (OSI), establish the technologies needed to meet these requirements, and to forecast the availability of these technologies. The OSI would perform path planning, tracking and control, object recognition, fault detection and correction, and plan modifications in connection with extravehicular (EV) robot operations.

Source record↗
NASA NTRS1986

Orifice-induced pressure error studies in Langley 7- by 10-foot high-speed tunnel

For some time it has been known that the presence of a static pressure measuring hole will disturb the local flow field in such a way that the sensed static pressure will be in error. The results of previous studies aimed at studying the error induced by the pressure orifice were for relatively low Reynolds number flows. Because of the advent of high Reynolds number transonic wind tunnels, a study was undertaken to assess the magnitude of this error at high Reynolds numbers than previously published and to study a possible method of eliminating this pressure error. This study was conducted in the Langley 7- by 10-Foot High-Speed Tunnel on a flat plate. The model was tested at Mach numbers from 0.40 to 0.72 and at Reynolds numbers from 7.7 x 1,000,000 to 11 x 1,000,000 per meter (2.3 x 1,000,000 to 3.4 x 1,000,000 per foot), respectively. The results indicated that as orifice size increased, the pressure error also increased but that a porous metal (sintered metal) plug inserted in an orifice could greatly reduce the pressure error induced by the orifice.

Plentovich, E. B.↗
NASA NTRS1986

Synthesis and analysis in studies of chemical evolution

Studies of the various processes that may have given rise to life on the Earth have demonstrated the appropriateness of an approach that makes use of analysis and synthesis. Analysis of extraterrestrial samples in the form of meteorites has demonstrated the presence of several precursors of biomolecules, most notably a full suite of nucleic acid bases and nucleotides of biological significance. These species were determined after exhaustive extraction of the sample and subsequent analysis using HPLC, GC, MS, and GC-MS. Procedural blanks indicate that these molecules are likely not the result of contamination during the extraction and analysis process. Similar species were found as products of spark discharge experiments in atmospheres thought to mimic primitive Earth conditions. These results indicate that the basic chemistry underlying these syntheses is common, and that life may not be unique to the Earth. Studies underway in the laboratory make use of proton nuclear magnetic resonance spectroscopy as a probe to assess associations between selected amino acids and any of several nucleotides comprising their genetic code and genetic anticode sequences. These studies demonstrate a clear selectivity by the anticode sequences, thus confirming the hydrophobicity studies performed by Lacey et al. These studies further support the contention that life is likely a natural result of the physics and chemistry of the universe.

Ponnamperuma, C.↗
NASA NTRS1986

Turbulent Boundary Layers in Oscillating Flows. Part 1: an Experimental and Computational Study

An experimental-computational study of the behavior of turbulent boundary layers for oscillating air flows over a plane surface with a small favorable mean pressure gradient is described. Experimental studies were conducted for boundary layers generated on the test section wall of a facility that produces a flow with a mean free stream velocity and a superposed nearly-pure sinusoidal component over a wide range of frequency. Flow at a nominal mean free stream velocity of 50 m/s were studied at atmospheric pressure and temperature at selected axial positions over a 2 m test length for frequencies ranging from 4 to 29 Hz. Quantitative experimental results are presented for unsteady velocity profiles and longitudinal turbulence levels obtained from hot wire anemometer measurements at three axial positions. Mean velocity profiles for oscillating flows were found to exhibit only small deviations from corresponding steady flow profiles, while amplitudes and phase relationships exhibited a strong dependence on axial position and frequency. Since sinusoidal flows could be generated over a wide range of frequency, studies at fixed values of reduced frequency at different axial positions were studied. Results show that there is some utility in the use of reduced frequency to correlate unsteady velocity results. The turbulence level u' sub rms was observed to vary essentially sinusoidally around values close to those measured in steady flow. However, the amplitude of oscillation and phase relations for turbulence level were found to be strongly frequency dependent. Numerical predictions were obtained using an unsteady boundary layer computational code and the Cebeci-Smith and Glushko turbulence models. Predicted quantities related to unsteady velocity profiles exhibit fair agreement with experiment when the Cebeci-Smith turbulence model is used.

Cook, W. J.↗
NASA NTRS1987

Wilson Cycle studies

The main activity relating to the study during this half year was a three week field trip to study Chinese sedimentary basins (June 10 to July 3, 1986) at no cost to the project. This study, while of a reconnaissance character, permitted progress in understanding how the processes of island arc-collision and micro-continental collision operated during the Paleozoic in far western China (especially the Junggar and Tarim basins and in the intervening Tien Shan Mountains). These effects of the continuing collision of India and Asia on the area were also studied. Most specifically, these result in the elevation of the Tien Shan to more than 4 km above sea level and the depression of Turfan to move 150m below sea level. Both thrusting and large-scale strike-slip motion are important in producing these elevation changes. Some effort during the half year was also devoted to the study of greenstone-belts in terms of the Wilson Cycle.

Burke, Kevin↗
NASA NTRS1985

Performance study of a data flow architecture

Teams of scientists studied data flow concepts, static data flow machine architecture, and the VAL language. Each team mapped its application onto the machine and coded it in VAL. The principal findings of the study were: (1) Five of the seven applications used the full power of the target machine. The galactic simulation and multigrid fluid flow teams found that a significantly smaller version of the machine (16 processing elements) would suffice. (2) A number of machine design parameters including processing element (PE) function unit numbers, array memory size and bandwidth, and routing network capability were found to be crucial for optimal machine performance. (3) The study participants readily acquired VAL programming skills. (4) Participants learned that application-based performance evaluation is a sound method of evaluating new computer architectures, even those that are not fully specified. During the course of the study, participants developed models for using computers to solve numerical problems and for evaluating new architectures. These models form the bases for future evaluation studies.

Adams, George↗
NASA NTRS1988

Thematic mapper study of Alaskan ophiolites

The two principle objectives of the project Thematic Mapper Study of Alaskan Ophiolites were to further develop techniques for producing geologic maps, and to study the tectonics of the ophiolite terrains of the Brooks Range and Ruby Geanticline of northern Alaska. Ophiolites, sections of oceanic lithosphere emplaced along island arcs and continental margins, are important to the understanding of mountain belt evolution. Ophiolites also provide an opportunity to study the structural, lithologic, and geochemical characteristics of ocean lithosphere, yielding a better understanding of the processes forming lithosphere. The first part of the report is a description of the methods and results of the TM mapping and gravity modeling. The second part includes papers being prepared for publication. These papers are the following: (1) an analysis of basalt spectral variations; (2) a study of basalt geochemical variations; (3) an examination of the cooling history of the ophiolites using radiometric data; (4) an analysis of shortening produced by thrusting during the Brooks Range orogeny; and (5) a study of an ophiolite using digital aeromagnetic and topographic data. Additional papers are in preparation.

Bird, John M.↗
NASA NTRS1987

Orbit transfer rocket engine technology program. Phase 2: Advanced engine study

In Phase 2 of the Advanced Engine Study, the Failure Modes and Effects Analysis (FMEA) maintenance-driven engine design, preliminary maintenance plan, and concept for space operable disconnects generated in Phase 1 were further developed. Based on the results of the vehicle contractors Orbit Transfer Vehicle (OTV) Concept Definition and System Analysis Phase A studies, minor revisions to the engine design were made. Additional refinements in the engine design were identified through further engine concept studies. These included an updated engine balance incorporating experimental heat transfer data from the Enhanced Heat Load Thrust Chamber Study and a Rao optimum nozzle contour. The preliminary maintenance plan of Phase 1 was further developed through additional studies. These included a compilation of critical component lives and life limiters and a review of the Space Shuttle Main Engine (SSME) operations and maintenance manual in order to begin outlining the overall maintenance procedures for the Orbit Transfer Vehicle Engine and identifying technology requirements for streamlining space-based operations. Phase 2 efforts also provided further definition to the advanced fluid coupling devices including the selection and preliminary design of a preferred concept and a preliminary test plan for its further development.

Erickson, C.↗
NASA NTRS1988

Microcomputer versus mainframe simulations: A case study

The research was conducted to two parts. Part one consisted of a study of the feasibility of running the Space Transportation Model simulation on an office IBM-AT. The second part was to design simulation runs so as to study the effects of certain performance factors on the execution of the simulation model. The results of this research are given in the two reports which follow: Microcomputer vs. Mainframe Simulation: A Case Study and Fractional Factorial Designs of Simulation Runs for the Space Transportation System Operations Model. In the first part, a DOS batch job was written in order to simplify the execution of the simulation model on an office microcomputer. A comparison study was then performed of running the model on NASA-Langley's mainframe computer vs. running on the IBM-AT microcomputer. This was done in order to find the advantages and disadvantages of running the model on each machine with the objective of determining if running of the office PC was practical. The study concluded that it was. The large number of performance parameters in the Space Transportation model precluded running a full factorial design needed to determine the most significant design factors. The second report gives several suggested fractional factorial designs which require far fewer simulation runs in order to determine which factors have significant influence on results.

Bengtson, Neal M.↗
NASA NTRS1990

Evaluation of a proposed expert system development methodology: Two case studies

Two expert system development projects were studied to evaluate a proposed Expert Systems Development Methodology (ESDM). The ESDM was developed to provide guidance to managers and technical personnel and serve as a standard in the development of expert systems. It was agreed that the proposed ESDM must be evaluated before it could be adopted; therefore a study was planned for its evaluation. This detailed study is now underway. Before the study began, however, two ongoing projects were selected for a retrospective evaluation. They were the Ranging Equipment Diagnostic Expert System (REDEX) and the Backup Control Mode Analysis and Utility System (BCAUS). Both projects were approximately 1 year into development. Interviews of project personnel were conducted, and the resulting data was used to prepare the retrospective evaluation. Decision models of the two projects were constructed and used to evaluate the completeness and accuracy of key provisions of ESDM. A major conclusion reached from these case studies is that suitability and risk analysis should be required for all AI projects, large and small. Further, the objectives of each stage of development during a project should be selected to reduce the next largest area of risk or uncertainty on the project.

Gilstrap, Lewey↗
NASA NTRS1990

An aircraft noise study in Norway

An extensive study of aircraft noise is currently being conducted in Oslo, Norway. The traffic at Oslo Airport Fornebu that includes both national and international flights, totals approximately 350 movements per day: 250 of these are regular scheduled flights with intermediate and large size aircraft, the bulk being DC9 and Boeing 737. The total traffic during the summer of 1989 was expected to resemble the maximum level to which the regular traffic will increase before the new airport can be put into operation. The situation therefore represented a possibility to study the noise impact on the communities around Fornebu. A comprehensive social survey was designed, including questions on both aircraft and road traffic noise. A random sample of 1650 respondents in 15 study areas were contacted for an interview. These areas represent different noise levels and different locations relative to the flight paths. The interviews were conducted in a 2 week period just prior to the transfer of charter traffic from Gardemoen to Fornebu. In the same period the aircraft noise was monitored in all 15 areas. In addition the airport is equipped with a permanent flight track and noise monitoring system. The noise situation both in the study period and on an average basis can therefore be accurately described. In August a group of 1800 new respondents were subjected to identical interviews in the same 15 areas, and the noise measurement program was repeated. Results of the study are discussed.

Gjestland, Truls T.↗
NASA NTRS1990

Laboratory studies, analysis, and interpretation of the spectra of hydrocarbons present in planetary atmospheres including cyanoacetylene, acetylene, propane, and ethane

Combining broadband Fourier transform spectrometers (FTS) from the McMath facility at NSO and from NRC in Ottawa and narrow band TDL data from the laboratories with computational physics techniques has produced a broad range of results for the study of planetary atmospheres. Motivation for the effort flows from the Voyager/IRIS observations and the needs of Voyager analysis for laboratory results. In addition, anticipation of the Cassini mission adds incentive to pursue studies of observed and potentially observable constituents of planetary atmospheres. Current studies include cyanoacetylene, acetylene, propane, and ethane. Particular attention is devoted to cyanoacetylen (H3CN) which is observed in the atmosphere of Titan. The results of a high resolution infrared laboratory study of the line positions of the 663, 449, and 22.5/cm fundamental bands are presented. Line position, reproducible to better than 5 MHz for the first two bands, are available for infrared astrophysical searches. Intensity and broadening studies are in progress. Acetylene is a nearly ubiquitous atmospheric constituent of the outer planets and Titan due to the nature of methane photochemistry. Results of ambient temperature absolute intensity measurements are presented for the fundamental and two two-quantum hotband in the 730/cm region. Low temperature hotband intensity and linewidth measurements are planned.

Blass, William E.↗
NASA NTRS1990

Theoretical and experimental studies of baroclinic processes

The geophysical fluid flow simulation code, GEOSIM, is being used to study the phenomenon of vacillation in the baroclinic annulus. Having verified that the code predicts vacillation for the same points as the experiments, the work is aiming toward explaining the mechanics of vacillation and pointing out some of the sensitivities of the results to the numerical method. Researchers are finding that there is a structural change associated with amplitude vacillation, where the structural changes are in the vertical. The results disagree with the premise of Lindzen et al, that the vacillation is due to constructive and destructive interference of neutral modes with different phase speeds. The researchers are continuing to study the Spacelab 3 Geophysical Fluid Flow Cell (GFFC) results with horizontal temperature gradients and heating from below. GEOSIM has been used to compute a wide range of cases, and these are being compared with the observations. The computations and observations compare well, and the model is being used to extend the results beyond cases studied in the experiments and to study the mechanics and predictability of the flows. The study of fully nonlinear baroclinic instability using the GFFC apparatus is proceeding with the numerical code. While the first instability that occurs is of planetary scale, secondary instabilities consisting of small-scale, penetrative convection occurs where cold fluid flows over a warm surface. The simultaneous modeling of the planetary scale and the convective scale is possible because of the nonhydrostatic formulation of the model. Some of these results have been animated on the Stardent computer, which shows the explosive nature of the small-scale convection.

Miller, Tim↗
NASA NTRS1991

Cosmos-1989 immunology studies

Evidence from both human and rodent studies has indicated that alterations in immunological parameters occur after space flight. The number of flight experiments has been small, and the full breadth of immunological alterations occurring after space flight remains to be established. Among the major effects on immune responses after space flight that have been reported are: alterations in lymphocyte blastogenesis and natural killer cell activity, alterations in production of cytokines, changes in leukocyte sub-population distribution, and decreases in the ability in the ability of bone marrow cells to respond to colony stimulating factors. Changes have been reported in immunological parameters of both humans and rodents. The significance of these alterations in relation to resistance to infection remains to be established. The current study involved a determination of the effects of flight on Cosmos mission 2044 on leukocyte subset distribution and the sensitivity of bone marrow cells to colony stimulating factor-GM. A parallel study with antiorthostatic suspension was also carried out. The study involved repetition and expansion of studies carried out on Cosmos 1887.

Sonnenfeld, Gerald↗