SEARCH · Engineering Papers

Results for “foresee”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4

All sources NASA NTRS DOE OSTI

NASA NTRS1991

Investigations of turbulent scalar fields using probability density function approach

Scalar fields undergoing random advection have attracted much attention from researchers in both the theoretical and practical sectors. Research interest spans from the study of the small scale structures of turbulent scalar fields to the modeling and simulations of turbulent reacting flows. The probability density function (PDF) method is an effective tool in the study of turbulent scalar fields, especially for those which involve chemical reactions. It has been argued that a one-point, joint PDF approach is the one to choose from among many simulation and closure methods for turbulent combustion and chemically reacting flows based on its practical feasibility in the foreseeable future for multiple reactants. Instead of the multi-point PDF, the joint PDF of a scalar and its gradient which represents the roles of both scalar and scalar diffusion is introduced. A proper closure model for the molecular diffusion term in the PDF equation is investigated. Another direction in this research is to study the mapping closure method that has been recently proposed to deal with the PDF's in turbulent fields. This method seems to have captured the physics correctly when applied to diffusion problems. However, if the turbulent stretching is included, the amplitude mapping has to be supplemented by either adjusting the parameters representing turbulent stretching at each time step or by introducing the coordinate mapping. This technique is still under development and seems to be quite promising. The final objective of this project is to understand some fundamental properties of the turbulent scalar fields and to develop practical numerical schemes that are capable of handling turbulent reacting flows.

Gao, Feng↗

NASA NTRS1994

Versatile Controller For CCD's

General-purpose controller for charge-coupled device (CCD) programmed to accommodate variety of CCD designs. In operation of controller, software used to specify CCD-clock waveforms, available in great diversity. Includes timing-signal generator controlled by microcomputer. Flexibility and speed makes it versatile tool for laboratory testing and for variety of applications. Controller operates existing CCD's and able to operate CCD's expected to be developed in foreseeable future.

Novello, J.↗

NASA NTRS1989

User interface support

Space construction will require heavy investment in the development of a wide variety of user interfaces for the computer-based tools that will be involved at every stage of construction operations. Using today's technology, user interface development is very expensive for two reasons: (1) specialized and scarce programming skills are required to implement the necessary graphical representations and complex control regimes for high-quality interfaces; (2) iteration on prototypes is required to meet user and task requirements, since these are difficult to anticipate with current (and foreseeable) design knowledge. We are attacking this problem by building a user interface development tool based on extensions to the spreadsheet model of computation. The tool provides high-level support for graphical user interfaces and permits dynamic modification of interfaces, without requiring conventional programming concepts and skills.

Lewis, Clayton↗

NASA NTRS1989

Lunar shuttle

Current plans for the extension of human presence into the solar system include the establishment of a permanently occupied base on the Moon for use as a source of raw materials, a transportation node, a facility for the fabrication and launch of elements of the space exploration infrastructure, and a base for scientific investigation and astronomical observatories. All of the aforementioned uses of a lunar base foresee the requirement for a lunar shuttle to operate from the lunar surface to one or more orbiting space stations located in low lunar orbits (LLO). The Utah State University lunar shuttle design is baslined for implementation after a mature lunar base has been established. The shuttle is designed to operate between the lunar base and a space station located in a 400-km-altitude orbit. This orbit was chosen with reference to Apollo experience, which has indicated that very low orbits, on the order of 100-km, may be unstable over periods of many months. After a thorough investigation of the anticipated needs and production capabilities of a lunar base, several design requirements were placed upon the shuttle. These requirements are (1) maximum use of lunar-derived propellant; (2) modularity and payload versatility; (3) two-way transport of 25-metric-ton cargo; (4) human transport capability; (5) satellite servicing; and (6) 3000-kg mass budget.

Voyer, P.↗

NASA NTRS1993

Advanced transportation system studies, technical area 3. Alternate propulsion subsystem concepts: J-2S restart study

The objectives were to assess what design changes would be required to remit late production of the J-2S engine for use as a large high energy upper stage engine. The study assessed design changes required to perform per the J-2S model specification, manufacturing changes required due to obsolescence or improvements in state-of-the-practice, availability issues for supplier provided items, and provided cost and schedule estimates for this configuration. The confidence that J-2S production could be reinitiated within reasonable costs and schedules was provided. No significant technical issues were identified in either the producibility study or in the review of previous technical data. Areas of potential cost reduction were identified which could be quantified to a greater extent with further manufacturing planning. The proposed schedule can be met with no foreseeable impacts. The results of the study provided the necessary foundation for the detailed manufacturing and test plans and non-recurring and recurring cost estimates that are needed to complete the effort to reinitiate production of the J-2S engine system.

Vilja, John↗

NASA NTRS1993

Presenting the Rain-Sea Interaction Facility

The new Rain-Sea Interaction Facility (RSIF) was established at GSFC/WFF and the first finds are presented. The unique feature of this laboratory is the ability to systematically study microwave scattering from a water surface roughened by artificial rain, for which the droplets are at terminal velocity. The fundamental instruments and systems (e.g., the rain simulator, scatterometers, and surface elevation probes) were installed and evaluated during these first experiments - so the majority of the data were obtained with the rain simulator at 1 m above the water tank. From these initial experiments, three new models were proposed: the square-root function for NCS vs. R, the log Gaussian model for ring-wave elevation frequency spectrum, and the Erland probability density distribution for back scattered power. Rain rate is the main input for these models, although the coefficients may be dependent upon other factors (drop-size distribution, fall velocity, radar configuration, etc.). The facility is functional and we foresee collaborative studies with investigators who are engaged in measuring and modeling rain-sea interaction processes.

Bliven, Larry F.↗

NASA NTRS1992

Deep near-infrared survey of the Southern Sky (DENIS)

DENIS (Deep Near-Infrared Survey of the Southern Sky) will be the first complete census of astronomical sources in the near-infrared spectral range. The challenges of this novel survey are both scientific and technical. Phenomena radiating in the near-infrared range from brown dwarfs to galaxies in the early stages of cosmological evolution, the scientific exploitation of data relevant over such a wide range requires pooling expertise from several of the leading European astronomical centers. The technical challenges of a project which will provide an order of magnitude more sources than given by the IRAS space mission, and which will involve advanced data-handling and image-processing techniques, likewise require pooling of hardware and software resources, as well as of human expertise. The DENIS project team is composed of some 40 scientists, computer specialists, and engineers located in 5 European Community countries (France, Germany, Italy, The Netherlands, and Spain), with important contributions from specialists in Australia, Brazil, Chile, and Hungary. DENIS will survey the entire southern sky in 3 colors, namely in the I band at a wavelength of 0.8 micron, in the 1.25 micron J band, and in the 2.15 micron K' band. The sensitivity limits will be 18th magnitude in the I band, 16th in the J band, and 14.5th in the K' band. The angular resolution achieved will be 1 arcsecond in the I band, and 3.0 arcseconds in the J and K' bands. The European Southern Observatory 1 m telescope on La Silla will be dedicated to survey use during operations expected to last four years, commencing in late 1993. DENIS aims to provide the astronomical community with complete digitized infrared images of the full southern sky and a catalogue of extracted objects, both of the best quality and in readily accessible form. This will be achieved through dedicated software packages and specialized catalogues, and with assistance from the Leiden and Paris Data Analysis Centers. The data will be mailed on DAT tapes from La Silla to the two Data Analysis Centers for further processing. Two centers are necessary because of the shear quantity of data and because of the complementary roles the Centers will develop, each exploiting its own particular expertise. The Leiden Data Analysis Center (LDAC) will extract objects, establish their parameters, and archive them into a source catalogue. The LDAC will collaborate with the Groningen Space Research group that has gained experience in infrared image handling from the IRAS satellite. The Paris Data Analysis Center (PDAC) will be responsible for archiving and preprocessing the raw data to provide a homogeneous set of data suitable for further reduction in both the Leiden and Paris data analysis streams. The PDAC will also extract and archive images for the sources flagged by the LDAC as extended, and create a catalogue of galaxies. In exploiting the DENIS data we foresee the collaboration with other data analysis centers, such as the Observatoire de Lyon where the relevant DENIS catalogue of galaxies can be incorporated into their extragalactic database. The Point Sources and the Small Extended Sources catalogues could be incorporated in the Late Type Star database at Montpellier, and in the SIMBAD database as CDS. At Groningen the IRAS Point Source catalogue and/or image data can be merged with the DENIS catalogues. At Meudon algorithms and software will be developed with main goal assessing the limits reachable for the homogeneity and intrinsic consistency between the ensemble of the images in the data base (flat-fielding, relative positioning of the fields, bootstrapped flux calibration) but also for the data analysis.

Deul, E.↗

NASA NTRS1993

A large eddy simulation scheme for turbulent reacting flows

The recent development of the dynamic subgrid-scale (SGS) model has provided a consistent method for generating localized turbulent mixing models and has opened up great possibilities for applying the large eddy simulation (LES) technique to real world problems. Given the fact that the direct numerical simulation (DNS) can not solve for engineering flow problems in the foreseeable future (Reynolds 1989), the LES is certainly an attractive alternative. It seems only natural to bring this new development in SGS modeling to bear on the reacting flows. The major stumbling block for introducing LES to reacting flow problems has been the proper modeling of the reaction source terms. Various models have been proposed, but none of them has a wide range of applicability. For example, some of the models in combustion have been based on the flamelet assumption which is only valid for relatively fast reactions. Some other models have neglected the effects of chemical reactions on the turbulent mixing time scale, which is certainly not valid for fast and non-isothermal reactions. The probability density function (PDF) method can be usefully employed to deal with the modeling of the reaction source terms. In order to fit into the framework of LES, a new PDF, the large eddy PDF (LEPDF), is introduced. This PDF provides an accurate representation for the filtered chemical source terms and can be readily calculated in the simulations. The details of this scheme are described.

Gao, Feng↗

NASA NTRS1993

The combustion program at CTR

Understanding and modeling of turbulent combustion are key problems in the computation of numerous practical systems. Because of the lack of analytical theories in this field and of the difficulty of performing precise experiments, direct numerical simulation (DNS) appears to be one of the most attractive tools to use in addressing this problem. The general objective of DNS of reacting flows is to improve our knowledge of turbulent combustion but also to use this information for turbulent combustion models. For the foreseeable future, numerical simulation of the full three-dimensional governing partial differential equations with variable density and transport properties as well as complex chemistry will remain intractable; thus, various levels of simplification will remain necessary. On one hand, the requirement to simplify is not necessarily a handicap: numerical simulations allow the researcher a degree of control in isolating specific physical phenomena that is inaccessible in experiments. CTR has pursued an intensive research program in the field of DNS for turbulent reacting flows since 1987. DNS of reacting flows is quite different from DNS of non-reacting flows: without reaction, the equations to solve are clearly the five conservation equations of the Navier Stokes system for compressible situations (four for incompressible cases), and the limitation of the approach is the Reynolds number (or in other words the number of points in the computation). For reacting flows, the choice of the equations, the species (each species will require one additional conservation equation), the chemical scheme, and the configuration itself is more complex.

Poinsot, Thierry J.↗

NASA NTRS1993

Hybrid techniques for complex aerospace electromagnetics problems

Important aerospace electromagnetics problems include the evaluation of antenna performance on aircraft and the prediction and control of the aircraft's electromagnetic signature. Due to the ever increasing complexity and expense of aircraft design, aerospace engineers have become increasingly dependent on computer solutions. Traditionally, computational electromagnetics (CEM) has relied primarily on four disparate techniques: the method of moments (MoM), the finite-difference time-domain (FDTD) technique, the finite element method (FEM), and high frequency asymptotic techniques (HFAT) such as ray tracing. Each of these techniques has distinct advantages and disadvantages, and no single technique is capable of accurately solving all problems of interest on computers that are available now or will be available in the foreseeable future. As a result, new approaches that overcome the deficiencies of traditional techniques are beginning to attract a great deal of interest in the CEM community. Among these new approaches are hybrid methods which combine two or more of these techniques into a coherent model. During the ASEE Summer Faculty Fellowship Program a hybrid FEM/MoM computer code was developed and applied to a geometry containing features found on many modern aircraft.

Aberle, Jim↗

NASA NTRS1994

Weightlessness and the human skeleton: A new perspective

It is now clear after more than two decades of space exploration that one of the major short- and long-term effects of microgravity on the human body is the loss of bone. The purpose of this presentation will be to review the data regarding the impact of microgravity and bed rest on calcium and bone metabolism. The author takes the position in this Socratic debate that the effect of microgravity on bone metabolism can be either reversed or mitigated. As we begins to contemplate long-duration space flight and habitation of Space Station Freedom and the moon, one of the issues that needs to be addressed is whether humans need to maintain a skeleton that has been adapted for the one-g force on earth. Clearly, in the foreseeable future, a healthy and structurally sound skeleton will be required for astronauts to shuttle back and forth from earth to the moon, space station, and Mars. Based on most available data from bed-rest studies and the short- and long-duration microgravity experiences by astronauts and cosmonauts, bone loss is a fact of life in this environment. With the rapid advances in understanding of bone physiology it is now possible to contemplate measures that can prevent or mitigate microgravity-induced bone loss. Will the new therapeutic approaches for enhancing bone mineralization be useful for preventing significant bone loss during long-term space flight? Are there other approaches such as exercise and electrical stimulation that can be used to mitigate the impact of microgravity on the skeleton? A recent study that evaluated the effect of microgravity on bone modeling in developing chick embryos may perhaps provide a new perspective about the impact of microgravity on bone metabolism.

Holick, Michael F.↗

NASA NTRS1993

Macro, mini, micro and nano (M(sup 3)N) technologies for the future

Microelectromechanical systems (MEMS), micro systems technologies (MST), and micromanufacturing are relatively recent phrases or acronyms that have become synonymous with the design, development, and manufacture of 'micro' devices and systems. Micromanufacturing encompasses MEMS or MST and, in addition, includes all of the processes involved in the production of micro things. Integration of mechanical and electrical components, including built-in computers, can be formed into systems which must be connected to the macroworld. Macro, mini, micro, and nano technologies are all a part of MEMS or micromanufacturing. At this point in the development of the technology, it is becoming apparent that mini systems, with micro components, could very well be the economic drivers of the technology for the foreseeable future. Initial research in the fabrication of microdevices using IC processing technology took place over thirty years ago. Anisotropic etching of silicon was used to produce piezoresistive diaphragms. Since the early 60's, there has been gradual progress in MEMS until the early 1980's when worldwide interest in the technology really started to develop. During this time high aspect ratio micromachining using x rays was started in Germany. In 1987 the concept of a 'silicon micromechanics foundry' was proposed. Since then the interest in the U.S., Germany, and Japan has increased to the point where hundreds of millions of dollars of research monies are being funneled into the technology (at least in Germany and Japan) and the technology has been classified as critical or as a technology or national importance by the U.S. government.

Friedrich, Craig R.↗

NASA NTRS1994

Meeting the challenges of installing a mobile robotic system

The challenges of integrating a mobile robotic system into an application environment are many. Most problems inherent to installing the mobile robotic system fall into one of three categories: (1) the physical environment - location(s) where, and conditions under which, the mobile robotic system will work; (2) the technological environment - external equipment with which the mobile robotic system will interact; and (3) the human environment - personnel who will operate and interact with the mobile robotic system. The successful integration of a mobile robotic system into these three types of application environment requires more than a good pair of pliers. The tools for this job include: careful planning, accurate measurement data (as-built drawings), complete technical data of systems to be interfaced, sufficient time and attention of key personnel for training on how to operate and program the robot, on-site access during installation, and a thorough understanding and appreciation - by all concerned - of the mobile robotic system's role in the security mission at the site, as well as the machine's capabilities and limitations. Patience, luck, and a sense of humor are also useful tools to keep handy during a mobile robotic system installation. This paper will discuss some specific examples of problems in each of three categories, and explore approaches to solving these problems. The discussion will draw from the author's experience with on-site installations of mobile robotic systems in various applications. Most of the information discussed in this paper has come directly from knowledge learned during installations of Cybermotion's SR2 security robots. A large part of the discussion will apply to any vehicle with a drive system, collision avoidance, and navigation sensors, which is, of course, what makes a vehicle autonomous. And it is with these sensors and a drive system that the installer must become familiar in order to foresee potential trouble areas in the physical, technical, and human environment.

Decorte, Celeste↗

NASA NTRS1993

The possibilities for mobile and fixed services up to the 20/30 GHz frequency bands

Satellite Communications and broadcasting is presently in a period of considerable change. In the fixed service there is strong competition from terrestrial fiber optic systems which have virtually arrested the growth of the traditional satellite market for long distance high capacity communications. The satellite has however made considerable progress in areas where it has unique advantages; for example, in point to multipoint (broadcasting), multipoint to point (data collection) and generally in small terminal system applications where flexibility of deployment coupled with ease of installation are of importance. In the mobile service, in addition to the already established geostationary systems, there are numerous proposals for HEO, MEO and LEO systems. There are also several new frequency allocations as a result of the WARC 92 to be taken into account. At one extreme there are researchers working on Ka band 20/30 GHz mobile systems and there are other groups who foresee no future above the L-band frequency allocations. Amongst all these inputs it is difficult to see the direction in which development activities both for satellites and for earth segment should be focused. However, as an aid to understanding, this paper seeks to find some underlying relationships and to clarify some of the variables.

Hughes, Clifford D.↗

NASA NTRS1994

Long-range consequences of interplanetary collisions

As Comet Shoemaker-Levy 9 races toward its mid-July collision with the planet Jupiter, considerable public attention is focused on catastrophic impacts with the Earth -- in the past and in the future. In recent years calls have been made to develop technologies that could deflect any asteroid or comet on a collision course. Careful consideration must be given to the nature and time scale of the risk and to the cost-effectiveness and possible problems in the suggested solutions. Risk assessment, threat removal, and resources misuse are examined. The greatest concern is to have a poorly informed public -- exerting pressure for means to mitigate even non-existent threats. The only foreseeable solution is a combination of accurate orbit estimation, realistic threat assessment, and effective public education.

Sagan, Carl↗

NASA NTRS1995

What's new, Voyager: The discoveries continue

The twin Voyager spacecraft, launched nearly two decades ago, continue to operate and are now searching for the edge of our solar system, the heliopause. Voyager's giant-planet flybys of Jupiter, Saturn, Uranus, and Neptune have provided data that are likely to remain the definitive data set for the foreseeable future and have led to many ongoing discoveries. As the spacecraft move toward the heliopause, they are also providing data on the structure of the heliosphere. This article discusses the discoveries resulting from the flyby and heliosphere data that have been made within the past five years.

Miner, Ellis D.↗

NASA NTRS1995

Stresses In And Near A Bend In A Thin-Walled Duct

Report describes computational study of distributions of stresses in and near 90 degrees bend in thin-walled duct subject to various applied loads. Purpose of study to help satisfy need for more accurate knowledge of local concentrations of stresses caused by loads: such knowledge makes possible to design light-weight ducts to survive reasonably foreseeable operating conditions with some degree of reliability. Also guides selection of locations for mounting strain gauges to measure local stresses for comparison with computed values, contributing to refinement of theoretical concepts and computational techniques.

Min, J. B.↗

NASA NTRS1995

Electronic manufacturing and packaging in Japan

This report summarizes the status of electronic manufacturing and packaging technology in Japan in comparison to that in the United States, and its impact on competition in electronic manufacturing in general. In addition to electronic manufacturing technologies, the report covers technology and manufacturing infrastructure, electronics manufacturing and assembly, quality assurance and reliability in the Japanese electronics industry, and successful product realization strategies. The panel found that Japan leads the United States in almost every electronics packaging technology. Japan clearly has achieved a strategic advantage in electronics production and process technologies. Panel members believe that Japanese competitors could be leading U.S. firms by as much as a decade in some electronics process technologies. Japan has established this marked competitive advantage in electronics as a consequence of developing low-cost, high-volume consumer products. Japan's infrastructure, and the remarkable cohesiveness of vision and purpose in government and industry, are key factors in the success of Japan's electronics industry. Although Japan will continue to dominate consumer electronics in the foreseeable future, opportunities exist for the United States and other industrial countries to capture an increasingly large part of the market. The JTEC panel has identified no insurmountable barriers that would prevent the United States from regaining a significant share of the consumer electronics market; in fact, there is ample evidence that the United States needs to aggressively pursue high-volume, low-cost electronic assembly, because it is a critical path leading to high-performance electronic systems.

Kelly, Michael J.↗