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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 631 records · Page 35

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NASA NTRS1981

Developing experiment instrument packages

Ground-Support Equipment (GSE) system supports development, calibration, and testing of experiment packages. It is also used for "quick look" processing and in-progress data analysis. User interacts with incoming telemetry data, performs computations, and controls execution of procedures using versatile Experiment Command Interactive Language (ECIL). Program is implemented many ways with minimal modification. It is written in MARCO II and FORTRAN for DEC PDP-11/34 using the RSX-11M operating system.

Herreid, R.↗

NASA NTRS1980

A singular perturbation analysis of minimum time long range intercept

The application of singular perturbation theory for deriving algorithms suitable for on board real time computation of optimal aircraft trajectory control was investigated. Minimum time intercept in three dimensions was selected as a pilot problem formulation, and data for an early version F-4 aircraft was used to represent aircraft aerodynamic and propulsion characteristics. Results include the derivation of nonlinear, near optimal feedback control laws that are readily implementable in an aircraft flight computer, performance results for a variety of initial conditions (including optimal intercept at short ranges), and a point mass three dimensional simulation suitable for representing fighter aircraft under closed loop optimal control.

Calise, A.↗

NASA NTRS1980

Laboratory evaluation of the pointing stability of the ASPS Vernier System

The annular suspension and pointing system (ASPS) is an end-mount experiment pointing system designed for use in the space shuttle. The results of the ASPS Vernier System (AVS) pointing stability tests conducted in a laboratory environment are documented. A simulated zero-G suspension was used to support the test payload in the laboratory. The AVS and the suspension were modelled and incorporated into a simulation of the laboratory test. Error sources were identified and pointing stability sensitivities were determined via simulation. Statistical predictions of laboratory test performance were derived and compared to actual laboratory test results. The predicted mean pointing stability during simulated shuttle disturbances was 1.22 arc seconds; the actual mean laboratory test pointing stability was 1.36 arc seconds. The successful prediction of laboratory test results provides increased confidence in the analytical understanding of the AVS magnetic bearing technology and allows confident prediction of in-flight performance. Computer simulations of ASPS, operating in the shuttle disturbance environment, predict in-flight pointing stability errors less than 0.01 arc seconds.

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NASA NTRS1980

Thermal protection of reentry vehicles by actively cooled nosetips

Analytical modeling efforts and clear-air ground test results of a transportation-cooled nosetips (TCNT) design are presented. The discrete water injection platelet TCNT described was conceived and created to achieve the performance requirements for severe reentry vehicle trajectories. Thermal performance computer modeling techniques, combing both local heat blockage and boundary layer recovery enthalpy reduction are outlined.

Walker, R. E.↗

NASA NTRS1979

Human factors by descent energy management

This paper describes some of the results of a human factors study of energy management during descent using standard aircraft displays. Discussions with pilots highlighted the practical constraints involved and the techniques (algorithms) used to accomplish the descent. The advantages and disadvantages of these algorithms are examined with respect to workload and their sensitivity to disturbances. Vertical navigation and flight performance computers are discussed in terms of the information needed for effective pilot monitoring and takeover

Curry, R. E.↗

NASA NTRS1982

The effect of brokenness on cloud-climate sensitivity

A study has been made of the effect of brokenness on the infrared and albedo feedback of clouds in climate models using a simplified treatment of broken cloudiness. It is shown that the individual feedback terms computed using the plane-parallel assumption differ markedly from the computations performed for a regular array of cuboidal clouds. If the cloudiness changes such that clear areas become cloudy but the nature of the broken cloud field remains unchanged, then both the feedbacks are magnified, the infrared more so than the albedo. However, if individual elements in the cloud field are increased horizontally in a constrained area, the feedbacks can be enhanced or diminished depending on the cloud fraction and aspect ratio of the elements. It is also shown that, in the global average, the ratio of the change in outgoing infrared flux to global albedo, as deduced from satellite measurements, will be larger than model simulations using planiform clouds.

Harshvardhan, MR.↗

NASA NTRS1981

Experimental program for the evaluation of turbofan/turboshaft c conversion technology

A TF34 turbofan engine is being modified to produce shaft power from an output coupling on the fan disk when variable inlet guide vanes are closed to reduce fan airflow. The engine, called a convertible engine, could be used on advanced rotorcraft such as X-wing, ABC (Advanced Blade Concept), and Folding Tilt Rotor, and on V/STOL craft in which two engines are cross-coupled. The engine will be tested on an outdoor static test stand at NASA Lewis Research Center. Steady-state tests will be made to measure performance in turbofan, turboshaft, and combined power output modes. Transient tests will be made to determine the response to the engine and a new digital engine control system for several types of rapid changes in thrust and shaft loads. The paper describes the engine modifications, the test facility equipment, proposed testing techniques for several types of tests, and typical test results predicted from engine performance computer programs.

Mcardle, J. G.↗

NASA NTRS1982

Compressor cascade performance deterioration caused by sand ingestion

Airfoil cascade erosion and performance deterioration was investigated in a gas particle cascade tunnel. The cascade blades were made of 2024 aluminum alloy and the solid particles used were quartz sand. The results of the experimental measurements are presented to show the change in the blade surface erosion, pressure distribution and the total loss coefficient with erosion. The surface quality of the blades exposed to particulate flows are changing the material surfaces. With time, the surface roughness increases and leads to a decrease in engine performance. It was found that the surface roughness values increase asymptotically to a maximum value with increased erosion. The experimental results indicate that the roughness parameters correlate well against the mass of particles impacting unit area of the surface. Such a correlation is useful in aerodynamics and performance computations in turbomachinery.

Tabakoff, W.↗

NASA NTRS1984

Overview of NASA Lewis Research Center free-piston Stirling engine activities

A generic free-piston Stirling technology project is being conducted to develop technologies generic to both space power and terrestrial heat pump applications in a cooperative, cost-shared effort. The generic technology effort includes extensive parametric testing of a 1 kW free-piston Stirling engine (RE-1000), development of a free-piston Stirling performance computer code, design and fabrication under contract of a hydraulic output modification for RE-1000 engine tests, and a 1000-hour endurance test, under contract, of a 3 kWe free-piston Stirling/alternator engine. A newly initiated space power technology feasibility demonstration effort addresses the capability of scaling a free-piston Stirling/alternator system to about 25 kWe; developing thermodynamic cycle efficiency or equal to 70 percent of Carnot at temperature ratios in the order of 1.5 to 2.0; achieving a power conversion unit specific weight of 6 kg/kWe; operating with noncontacting gas bearings; and dynamically balancing the system. Planned engine and component design and test efforts are described.

Slaby, J. G.↗

NASA NTRS1984

Analysis of physical-chemical processes governing SSME internal fluid flows

In order to aid the development of current and future SSME type engines, it is necessary to improve the understanding of basic issues related with physical-chemical processes of SSME internal flows. Accomplishments under each of the following specific objectives are described herein: (1) supplying a state-of-the-art CFD code and graphics package; (2) demonstrating code usage on SSME-related problems to NASA MSFC personnel; and (3) performance computations and analysis of problems relevant to current and future SSME's.

Singhal, A. K.↗

NASA NTRS1985

Analysis of physical-chemical processes governing SSME internal fluid flows

The basic issues concerning the physical chemical processes of the Space Shuttle Main Engine are discussed. The objectives being to supply the general purpose CFD code PHOENICS and the associated interactive graphics package - GRAFFIC; to demonstrate code usage on SSME related problems; to perform computations and analyses of problems relevant to current and future SSME's; and to participate in the development of new physical models of various processes present in SSME components. These objectives are discussed in detail.

Singhal, A. K.↗

NASA NTRS1985

Modeling and measurement of fault-tolerant multiprocessors

The workload effects on computer performance are addressed first for a highly reliable unibus multiprocessor used in real-time control. As an approach to studing these effects, a modified Stochastic Petri Net (SPN) is used to describe the synchronous operation of the multiprocessor system. From this model the vital components affecting performance can be determined. However, because of the complexity in solving the modified SPN, a simpler model, i.e., a closed priority queuing network, is constructed that represents the same critical aspects. The use of this model for a specific application requires the partitioning of the workload into job classes. It is shown that the steady state solution of the queuing model directly produces useful results. The use of this model in evaluating an existing system, the Fault Tolerant Multiprocessor (FTMP) at the NASA AIRLAB, is outlined with some experimental results. Also addressed is the technique of measuring fault latency, an important microscopic system parameter. Most related works have assumed no or a negligible fault latency and then performed approximate analyses. To eliminate this deficiency, a new methodology for indirectly measuring fault latency is presented.

Shin, K. G.↗

NASA NTRS1983

The use of Ada in distributed simulations

The increasing need for detailed information about systems of continually growing complexity enhances steadily the demands regarding the employed models. The present investigation is concerned with work related to the development of high-performance computer hardware intended for the support of the real-time simulation of jet engines. The hardware is structured in the form of a network of communicating microprocessors running in parallel. The need for a higher-order language capability for programming such a network has led to the research considered in this study. Attention is given to the hardware which is being developed, an abstract model, programming language considerations, research considerations, research objectives, Ada tasks, Ada packages, the Ada model, the mapping of the model to the hardware, a precompiler example, and the advantages of Ada.

Collins, W. R.↗

NASA NTRS1984

Overview of NASA Lewis Research Center free-piston Stirling engine activities

Slaby, J. G.↗

NASA NTRS1985

Overview of free-piston Stirling technology at the NASA Lewis Research Center

An overview of the National Aeronautics and Space Administration (NASA) Lewis Research Center (Lewis) free-piston Stirling engine activities is presented. These activities include: (1) a generic free-piston Stirling technology project being conducted to develop technologies synergistic to both space power and terrestrial heat pump applications in a cooperative, cost-shared effort with the Department of Energy (DOE/Oak Ridge National Laboratory (ONRL)), and (2) a free-piston Stirling space-power technology demonstration project as part of the SP-100 program being conducted in support of the Department of Defense (DOD), DOE, and NASA/Lewis. The generic technology effort includes extensive parametric testing of a 1 kw free-piston Stirling engine (RE-1000), development and validation of a free-piston Stirling performance computer code, and fabrication and initial testing of an hydraulic output modification for the RE-1000 engine. The space power technology effort, under SP-100, addresses the status of the 25 kWe Space Power Demonstrator Engine (SPDE) including early test results.

Slaby, J. G.↗

NASA NTRS1985

Interactive information processing for NASA's mesoscale analysis and space sensor program

The Atmospheric Sciences Division (ASD) of the Systems Dynamics Laboratory at NASA's Marshall Space Flight Center (MSFC) is currently involved in interactive information processing for the Mesoscale Analysis and Space Sensor (MASS) program. Specifically, the ASD is engaged in the development and implementation of new space-borne remote sensing technology to observe and measure mesoscale atmospheric processes. These space measurements and conventional observational data are being processed together to gain an improved understanding of the mesoscale structure and the dynamical evolution of the atmosphere relative to cloud development and precipitation processes. To satisfy its vast data processing requirements, the ASD has developed a Researcher Computer System consiting of three primary computer systems which provides over 20 scientists with a wide range of capabilities for processing and displaying a large volumes of remote sensing data. Each of the computers performs a specific function according to its unique capabilities.

Parker, K. G.↗

NASA NTRS1987

Improvement of the Earth's gravity field from terrestrial and satellite data

The terrestrial gravity data base was updated. Studies related to the Geopotential Research Mission (GRM) have primarily considered the local recovery of gravity anomalies on the surface of the Earth based on satellite to satellite tracking or gradiometer data. A simulation study was used to estimate the accuracy of 1 degree-mean anomalies which could be recovered from the GRM data. Numerous procedures were developed for the intent of performing computations at the laser stations in the SL6 system to improve geoid undulation calculations.

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NASA NTRS1987

Modeling and implementation of wind shear data

The problems of implementing the JAWS wind shear data are discussed. The data sets are described from the view of utilizing them in an aircraft performance computer program. Then, some of the problems of nonstandard procedures are described in terms of programming the equations of aircraft motion when the effects of temporal and spatially variable winds are included. Finally, some of the computed effects of the various wind shear terms are shown.

Frost, Walter↗