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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 379 records · Page 21

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NASA NTRS1988

Comparison of Space Shuttle Hot Gas Manifold analysis to air flow data

This paper summarizes several recent analyses of the Space Shuttle Main Engine Hot Gas Manifold and compares predicted flow environments to air flow data. Codes used in these analyses include INS3D, PAGE, PHOENICS, and VAST. Both laminar (Re = 250, M = 0.30) and turbulent (Re = 1.9 million, M = 0.30) results are discussed, with the latter being compared to data for system losses, outer wall static pressures, and manifold exit Mach number profiles. Comparison of predicted results for the turbulent case to air flow data shows that the analysis using INS3D predicted system losses within 1 percent error, while the PHOENICS, PAGE, and VAST codes erred by 31, 35, and 47 percent, respectively. The INS3D, PHOENICS, and PAGE codes did a reasonable job of predicting outer wall static pressure, while the PHOENICS code predicted exit Mach number profiles with acceptable accuracy. INS3D was approximately an order of magnitude more efficient than the other codes in terms of code speed and memory requirements. In general, it is seen that complex internal flows in manifold-like geometries can be predicted with a limited degree of confidence, and further development is necessary to improve both efficiency and accuracy of codes if they are to be used as design tools for complex three-dimensional geometries.

Mcconnaughey, P. K.↗

NASA NTRS1989

Dynamic Transfers Of Tasks Among Computers

Allocation scheme gives jobs to idle computers. Ideal resource-sharing algorithm should have following characteristics: Dynamics, decentralized, and heterogeneous. Proposed enhanced receiver-initiated dynamic algorithm (ERIDA) for resource sharing fulfills all above criteria. Provides method balancing workload among hosts, resulting in improvement in response time and throughput performance of total system. Adjusts dynamically to traffic load of each station.

Liu, Howard T.↗

NASA NTRS1989

Aiming Instruments On The Space Station

Report discusses capabilities and requirements for aiming scientific instruments carried aboard proposed Space Station. Addresses two issues: whether system envisioned for pointing instruments at celestial targets offers sufficiently low jitter, high accuracy, and high stability to meet scientific requirements; whether it can do so even in presence of many vibrations and other disturbances on Space Station. Salient conclusion of study, recommendation to develop pointing-actuator system including mechanical/fluid base isolator underneath reactionaless gimbal subsystem. This kind of system offers greatest promise of high performance, cost-effectiveness, and modularity for job at hand.

Estus, Jay M.↗

NASA NTRS1988

Modeling of transitional flows

An effort directed at developing improved transitional models was initiated. The focus of this work was concentrated on the critical assessment of a popular existing transitional model developed by McDonald and Fish in 1972. The objective of this effort was to identify the shortcomings of the McDonald-Fish model and to use the insights gained to suggest modifications or alterations of the basic model. In order to evaluate the transitional model, a compressible boundary layer code was required. Accordingly, a two-dimensional compressible boundary layer code was developed. The program was based on a three-point fully implicit finite difference algorithm where the equations were solved in an uncoupled manner with second order extrapolation used to evaluate the non-linear coefficients. Iteration was offered as an option if the extrapolation error could not be tolerated. The differencing scheme was arranged to be second order in both spatial directions on an arbitrarily stretched mesh. A variety of boundary condition options were implemented including specification of an external pressure gradient, specification of a wall temperature distribution, and specification of an external temperature distribution. Overall the results of the initial phase of this work indicate that the McDonald-Fish model does a poor job at predicting the details of the turbulent flow structure during the transition region.

Lund, Thomas S.↗

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 NTRS1988

Issues and opportunities in space photovoltaics

Space power sources are becoming a central focus for determining man's potential and schedule for exploring and utilizing the benefits of space. The ability to search, probe, survey, and communicate throughout the universe will depend on providing adequate power to the instruments to do these jobs. Power requirements for space platforms are increasing and will continue to increase into the 21st century. Photovoltaics have been a dependable power source for space for the last 30 years and have served as the primary source of power on virtually all DOD and NASA satellites. The performance of silicon (Si) solar cells has increased from 10 percent air mass zero (AM0) solar energy conversion efficiency in the early 60's to almost 15 percent on today's spacecraft. Some technologists even think that the potential for solar photovoltaics has reached a plateau. However, present and near-future Air Force and NASA requirements show needs that, if the problems are looked upon as opportunities, can elevate the photovoltaic power source scientist and array structure engineer into the next technological photovoltaic growth curve.

Francis, Robert W.↗

NASA NTRS1988

Use of SAR imagery and other remotely-sensed data in deriving ice information during a severe ice event on the Grand Banks (Newfoundland)

Image data from synthetic aperture radar (SAR) are used to observe an ice compaction event off the East Coast of Newfoundland in spring, 1987. The information developed from sequential SAR observations is shown to do a remarkably effective job of describing the ice conditions; the difficult variable is the ice thickness which is found to be surprisingly large (2 to 4 times the thickness predictable from thermodynamic growth alone). It may be possible to model the ice thickness using SAR-derived ice motion.

Carsey, F. D.↗

NASA NTRS1988

Knowledge-based graphical interfaces for presenting technical information

Designing effective presentations of technical information is extremely difficult and time-consuming. Moreover, the combination of increasing task complexity and declining job skills makes the need for high-quality technical presentations especially urgent. We believe that this need can ultimately be met through the development of knowledge-based graphical interfaces that can design and present technical information. Since much material is most naturally communicated through pictures, our work has stressed the importance of well-designed graphics, concentrating on generating pictures and laying out displays containing them. We describe APEX, a testbed picture generation system that creates sequences of pictures that depict the performance of simple actions in a world of 3D objects. Our system supports rules for determining automatically the objects to be shown in a picture, the style and level of detail with which they should be rendered, the method by which the action itself should be indicated, and the picture's camera specification. We then describe work on GRIDS, an experimental display layout system that addresses some of the problems in designing displays containing these pictures, determining the position and size of the material to be presented.

Feiner, Steven↗

NASA NTRS1988

Optimal solutions for complex design problems: Using isoperformance software for human factors trade offs

A major application of isoperformance is as a trade-off methodology of the three major drivers of system design; equipment, training variables, and user characteristics. The flexibility of isoperformance allows each of these three components to be nearly any rational variation. For example, aptitude may be military Armed Forces Qualification Testing (AFQT) categories, cutoff scores within a selection procedure, or simply dichotomizing high and low scorers (pass/fail). Equipment may be new versus old, 'smart' versus dumb, high versus low resolution, etc. Training may be short versus long or varieties of media types (lecture versus CAI/CBI versus self-paced workbooks). In its final computerized form isoperformance lets the user set an operational level of performance (e.g., a jet pilot in a simulated emergency must take prescribed corrective action and clear the plane in several seconds, pilot astronauts will check out all shuttle flight systems within 30 minutes, or Mission Specialists must handle sucdessfully a required number of job elements). At this point the computer program guides the user through any requested trade-offs of the three components while maintaining the specified operational level of performance through isoperformance curves. A demonstration of the computer program is currently available.

Kennedy, Robert S.↗

NASA NTRS1989

Computational procedures for postbuckling of composite shells

A recently developed finite-element capability for general nonlinear shell analysis, featuring the use of three-dimensional constitutive equations within an efficient resultant-oriented framework, is employed to simulate the postbuckling response of an axially compressed composite cylindrical panel with a circular cutout. The problem is a generic example of modern composite aircraft components for which postbuckling strength (i.e., fail-safety) is desired in the presence of local discontinuities such as holes and cracked stiffeners. While the computational software does a reasonable job of predicting both the buckling load and the qualitative aspects of postbuckling (compared both with experiment and another code) there are some discrepancies due to: (1) uncertainties in the nominal layer material properties, (2) structural sensitivity to initial imperfections, and (3) the neglect of dynamic and local material delamination effects in the numerical model. Corresponding refinements are suggested for the realistic continuation of this type of analysis.

Stanley, G. M.↗

NASA NTRS1988

Memory protection

Accidental overwriting of files or of memory regions belonging to other programs, browsing of personal files by superusers, Trojan horses, and viruses are examples of breakdowns in workstations and personal computers that would be significantly reduced by memory protection. Memory protection is the capability of an operating system and supporting hardware to delimit segments of memory, to control whether segments can be read from or written into, and to confine accesses of a program to its segments alone. The absence of memory protection in many operating systems today is the result of a bias toward a narrow definition of performance as maximum instruction-execution rate. A broader definition, including the time to get the job done, makes clear that cost of recovery from memory interference errors reduces expected performance. The mechanisms of memory protection are well understood, powerful, efficient, and elegant. They add to performance in the broad sense without reducing instruction execution rate.

Denning, Peter J.↗

NASA NTRS1989

The private sector economic and employment benefits to the nation and to each state of proposed FY 1990 NASA procurement expenditures

The private sector economic and employment benefits (disaggregated among 80 industries and 475 occupations) of the proposed FY 1990 NASA procurement expenditures to the nation and to each state are estimated. Nationwide, it is found that FY 1990 NASA procurement expenditures of $11.3 billion will have an economic multiplier of 2.1 and will create, directly and indirectly, 237,000 jobs, $23.2 billion in total industry sales, $2.4 billion in corporate profits, and $7.4 billion in Federal, state, and local government tax revenues. These benefits are widely dispersed throughout the United States and are significant in many states not normally considered to be major beneficiaries of NASA spending. The indirect economic benefits are identified for each state resulting from the second-, third-, and fourth rounds of industry purchases generated by NASA procurement expenditures. Each state is ranked on the basis of several criteria, including the total benefits, indirect benefits, and per capita benefits received from NASA spending. The estimates developed are important for maintaining a viable U.S. Space Program through the remainder of this century.

Source record↗

NASA NTRS1988

The three R's of training: Recording, Retaining, and Reporting - The training management system that synergizes

NASA's Kennedy Space Center employs a Training and Certification Record System (TCRS) which tracks and maintains records for each of its employees, encompassing all aspects of training history: training courses, physical examinations, proficiency tests, on-the-job training, standboards, and certifications with completions and expiration dates. TCRS, which is fully automated, includes an expiration-alert notification capability to project recurring expirations, thereby functioning as a forecasting tool for training budgets.

Ingram, Dick D.↗

NASA NTRS1988

The Transportable Applications Environment - An interactive design-to-production development system

An account is given of the design philosophy and architecture of the Transportable Applications Environment (TAE), an executive program binding a system of applications programs into a single, easily operable whole. TAE simplifies the job of a system developer by furnishing a stable framework for system-building; it also integrates system activities, and cooperates with the host operating system in order to perform such functions as task-scheduling and I/O. The initial TAE human/computer interface supported command and menu interfaces, data displays, parameter-prompting, error-reporting, and online help. Recent extensions support graphics workstations with a window-based, modeless user interface.

Perkins, Dorothy C.↗

NASA NTRS1989

On the modelling of scalar and mass transport in combustor flows

Results are presented of a numerical study of swirling and nonswirling combustor flows with and without density variations. Constant-density arguments are used to justify closure assumptions invoked for the transport equations for turbulent momentum and scalar fluxes, which are written in terms of density-weighted variables. Comparisons are carried out with measurements obtained from three different axisymmetric model combustor experiments covering recirculating flow, swirling flow, and variable-density swirling flow inside the model combustors. Results show that the Reynolds stress/flux models do a credible job of predicting constant-density swirling and nonswirling combustor flows with passive scalar transport. However, their improvements over algebraic stress/flux models are marginal. The extension of the constant-density models to variable-density flow calculations shows that the models are equally valid for such flows.

Nikjooy, M.↗

NASA NTRS1990

Dummy Cup Helps Robot-Welder Programmers

Dummy gas cup used on torch of robotic welder during programming and practice runs. Made of metal or plastic, dummy cup inexpensive and durable. Withstands bumps caused by programming errors, and is sized for special welding jobs within limited clearances. After robot satisfactorily programmed, replaced by ceramic cup of same dimensions for actual welding.

Gordon, Stephen S.↗

NASA NTRS1990

Jam-Resistant Cutters For Emergency Separation

Pyrotechnic emergency-separation system includes shaped explosive charges that sever pair of hinges. System ensures reliable opening of escape hatch. Two pairs of cutters provided for each hinge so if one pair of cutters fails, other completes job. Pressure of explosions vented to prevent charge holders from fragmenting and forming sharp edges around open hatch. Exit slide deployed without tearing. Before detonation L-shaped retainers bear on hinge. After denonation, retainers fold outward to facilitate egress of severed hinges.

Ordonez, Arturo C.↗

NASA NTRS1990

Neural-Network Processor Would Allocate Resources

Global optimization problems solved quickly. Neural-network processor optimizes allocation of M resources among N expenditures according to cost of pairing each resource with each expenditure and subject to limit on number of resources feeding into each expenditure and/or limit on number of expenditures to which each resource allocated. One cell performs several analog and digital functions. Potential applications include assignment of jobs, scheduling, dispatching, and planning of military maneuvers.

Eberhardt, Silvio P.↗