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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Bithermal fatigue - A link between isothermal and thermomechanical fatigue

A technique for bithermal fatigue testing is presented in which the tensile and compressive halves of the cycle are conducted isothermally at two significantly different temperatures. With reference to experimental results obtained for a nickel-base superalloy, B1900 + Hf, it is shown that bithermal fatigue testing is a simple alternative to thermomechanical fatigue and can provide a conservative determination of thermomechanical fatigue life for creep damage dominated failure modes. Bithermal fatigue results can be directly related to thermomechanical fatigue results through the use of an appropriate damage rule.

Halford, Gary R.↗
NASA NTRS1988

An overview of rotorcraft propulsion research at Lewis Research Center

Rotorcraft propulsion research at Lewis Research Center is discussed, stressing programs in four areas of component research: compressors, combustors, turbines and transmissions, and three developmental programs: the Small Turboshaft Engine Research (STER) Project, the Advanced Rotorcraft Transmission (ART) program, and the Compound Cycle Engine (CCE) program. The component research emphasizes special problems of turboshaft engines in the 5 lb/sec to 30 lb/sec range. The objectives of the STER program are to evaluate the application of advanced concepts to small turboshaft engine systems and to investigate system related phenomena, such as distortion effects and secondary flow phenomena. The goals of the ART program are to reduce transmission weight by 25 percent, noise generation by 10 dB and mean time between removal to 5,000 hrs. The CCE program is working to combine the airflow capacity and light-weight features of a gas turbine with the more efficient, but heavier diesel turbine.

Bill, Robert C.↗
NASA NTRS1987

FIESTA: An operational decision aid for space network fault isolation

The Fault Tolerance Expert System for Tracking and Data Relay Satellite System (TDRSS) Applications (FIESTA) is a fault detection and fault diagnosis expert system being developed as a decision aid to support operations in the Network Control Center (NCC) for NASA's Space Network. The operational objectives which influenced FIESTA development are presented and an overview of the architecture used to achieve these goals are provided. The approach to the knowledge engineering effort and the methodology employed are also presented and illustrated with examples drawn from the FIESTA domain.

Lowe, Dawn↗
NASA NTRS1988

Subselenean tunneler melting head design: A preliminary study

The placement of base facilities in subsurface tunnels created as a result of subsurface mining is described as an alternative to the establishing of a base on the lunar surface. Placement of the base facilities and operations in subselenean tunnels will allow personnel to live and work free from the problem of radiation and temperature variations. A conceptual design for a tunneling device applicable to such a lunar base application was performed to assess the feasibility of the concept. A tunneler was designed which would melt through the lunar material leaving behind glass lined tunnels for later development. The tunneler uses a nuclear generator which supplies the energy to thermally melt the regolith about the cone shaped head. Melted regolith is exacavated through intakes in the head and transferred to a truck which hauls it to the surface. The tunnel walls are solidified to provide support lining by using an active cooling system about the mid section of the tunneler. Also addressed is the rationale for a subselenean tunneler and the tunneler configuration and subsystems, as well as the reasoning behind the resulting design.

Engblom, Bill↗
NASA NTRS1989

Pilots' use of a traffic alert and collision-avoidance system (TCAS 2) in simulated air carrier operations. Volume 1: Methodology, summary and conclusions

Pilots' use of and responses to a traffic alert and collision-avoidance system (TCAS 2) in simulated air carrier line operations are described in Volume 1. TCAS 2 monitors the positions of nearby aircraft by means of transponder interrogation, and it commands a climb or descent when conflicting aircraft are projected to reach an unsafe closest point-of-approach within 20 to 25 seconds. A different level of information about the location of other air traffic was presented to each of three groups of flight crews during their execution of eight simulated air carrier flights. A fourth group of pilots flew the same segments without TCAS 2 equipment. Traffic conflicts were generated at intervals during the flights; many of the conflict aircraft were visible to the flight crews. The TCAS equipment successfully ameliorated the seriousness of all conflicts; three of four non-TCAS crews had hazardous encounters. Response times to TCAS maneuver commands did not differ as a function of the amount of information provided, nor did response accuracy. Differences in flight experience did not appear to contribute to the small performance differences observed. Pilots used the displays of conflicting traffic to maneuver to avoid unseen traffic before maneuver advisories were issued by the TCAS equipment. The results indicate: (1) that pilots utilize TCAS effectively within the response times allocated by the TCAS logic, and (2) that TCAS 2 is an effective collision avoidance device. Volume II contains the appendices referenced in Volume I, providing details of the experiment and the results, and the text of two reports written in support of the program.

Chappell, Sheryl L.↗
NASA NTRS1989

Pilots' use of a traffic alert and collision-avoidance system (TCAS 2) in simulated air carrier operations. Volume 2: Appendices

Pilots' use of and responses to a traffic alert and collision-avoidance system (TCAS 2) in simulated air carrier line operations are discribed in Volume 1. TCAS 2 monitors the positions of nearby aircraft by means of transponder interrogation, and it commands a climb or descent which conflicting aircraft are projected to reach an unsafe closest point-of-approach within 20 to 25 seconds. A different level of information about the location of other air traffic was presented to each of three groups of flight crews during their execution of eight simulated air carrier flights. A fourth group of pilots flew the same segments without TCAS 2 equipment. Traffic conflicts were generated at intervals during the flights; many of the conflict aircraft were visible to the flight crews. The TCAS equipment successfully ameliorated the seriousness of all conflicts; three of four non-TCAS crews had hazardous encounters. Response times to TCAS maneuver commands did not differ as a function of the amount of information provided, nor did response accuracy. Differences in flight experience did not appear to contribute to the small performance differences observed. Pilots used the displays of conflicting traffic to maneuver to avoid unseen traffic before maneuver advisories were issued by the TCAS equipment. The results indicate: (1) that pilots utilize TCAS effectively within the response times allocated by the TCAS logic, and (2) that TCAS 2 is an effective collision avoidance device. Volume 2 contains the appendices referenced in Volume 1, providing details of the experiment and the results, and the text of two reports written in support of the program.

Chappell, Sheryl L.↗
NASA NTRS1988

CONDOR: Long endurance high altitude vehicle, volume 5

The results of a design study resulting in the proposed CONDOR aircraft are presented. The basic requirements are for the aircraft to maintain continuous altitude at or above 45,000 feet for at least a 3-day mission, be able to comfortably support a two-man crew during this period with their field of vision not obstructed to a significant degree, carry a payload of 200 pounds, and provide a power supply to the payload of 2000 watts. The take-off and landing distances must be below 5000. feet, and time to reach cruise altitude must not exceed 3 hours. The subjects discussed are configuration selection, structural analysis, stability and control, crew and payload accomodations, and economic estimates.

Andrews, L. Cullen↗
NASA NTRS1989

A graphics package for meteorological data, version 1.5

A plotting package has been developed to simplify the task of plotting meteorological data. The calling sequences and examples of high level yet flexible routines which allow contouring, vectors and shading of cylindrical, polar, orthographic and Mollweide (egg) projections are given. Routines are also included for contouring pressure-latitude and pressure-longitude fields with linear or log scales in pressure (interpolation to fixed grid interval is done automatically). Also included is a fairly general line plotting routine. The present version (1.5) produces plots on WMS laser printers and uses graphics primitives from WOLFPLOT.

Moorthi, Shrinivas↗
NASA NTRS1988

Advanced transmission studies

The NASA Lewis Research Center and the U.S. Army Aviation Systems Command share an interest in advancing the technology for helicopter propulsion systems. In particular, this paper presents highlights from that portion of the program in drive train technology and the related mechanical components. The major goals of the program are to increase the life, reliability, and maintainability; reduce the weight, noise, and vibration; and maintain the relatively high mechanical efficiency of the gear train. The current activity emphasizes noise reduction technology and analytical code development followed by experimental verification. Selected significant advances in technology for transmissions are reviewed, including advance configurations and new analytical tools. Finally, the plan for future transmission research is presented.

Coy, John J.↗
NASA NTRS1988

TASKILLAN - A simulation to predict the validity of multiple resource models of aviation workload

A study to establish the validity of five predictive models of workload in the context of a controlled helicopter mission, TASKILLAN, is presented. Ten subjects performed simulations involving combinations of a low level flight task with three cognitive side tasks pertaining to navigation, spatial awareness, and computation. It is found that the best predictors of subjective workload are relativly simple models that integrate the total demands of task over time.

Wickens, Christopher D.↗
NASA NTRS1989

The moments of inertia of Mars

The mean moment of inertia of Mars is, at present, very poorly constrained. The generally accepted value of 0.365 M(R-squared) is obtained by assuming that the observed second degree gravity field can be decomposed into a hydrostatic oblate spheroid and a nonhydrostatic prolate spheroid with an equatorial axis of symmetry. An alternative decomposition is advocated in the present analysis. If the nonhydrostatic component is a maximally triaxial ellipsoid (intermediate moment exactly midway between greatest and least), the hydrostatic component is consistent with a mean moment of 0.345 M(R-squared). The plausibility of this decomposition is supported by statistical arguments and comparison with the earth, moon and Venus.

Bills, Bruce G.↗
NASA NTRS1989

Variations in effective compensation depth across Aphrodite Terra, Venus

Topography and gravity data obtained by Pioneer Venus Orbiter have been used to estimate an effective depth of Airy compensation for each of 75 orbital arcs that provide fairly uniform areal coverage of Aphrodite Terra. A general increase in compensation depth is noted to the east, with the most rapid change occurring near 135 deg. Five distinctive regional patterns, four well defined peaks, and one interval of widely scattered and poorly constrained depths are found to be superimposed on this larger trend. It is noted that the maxima in compensation depth correlate well with regional topographic highs.

Herrick, Robert R.↗
NASA NTRS1989

Efficient grid generation

The application of a new efficient grid generation method in computational fluid dynamics is discussed. After 100 iterations, final grids were produced in about 110 seconds using a VAX 8650 computer in a time-shared mode. Using a SUN 3/50 workstation, a similar version of the program completed 100 iterations in about 15 minutes.

Gutierrez, Bill↗
NASA NTRS1990

Space Information For Educators

Anyone with personal computer, modem, and telephone can obtain educational materials. Access to collection of NASA information, stored in computer in Huntsville, Alabama, obtained over telephone lines from computers in classrooms and homes. Available free of charge. Users must pay own telephone charges. Data base offers information on following topics: NASA news; Research in aeronautics; Space exploration before Space Shuttle; Exploration with Space Shuttle and beyond; NASA and its centers; NASA educational services; Classroom materials; and Space program spinoffs. User communicates with Spacelink via almost any existing communication software. Simple keystrokes control display of documents on user's terminal.

Anderson, Bill↗
NASA NTRS1990

Evaluation Of An Aircraft-Collision-Avoidance System

Report describes study of pilots' use of traffic alert and collision-avoidance system (TCAS II) in simulated airplane flights. Gives alert by light and sound when another aircraft within 40 s of passing very closely. If other aircraft still poses threat 15 to 20 s later, TCAS II advises pilot to maneuver vertically or to continue on same flightpath but alter rate of ascent or descent. Report describes methodology, summarizes results, and presents conclusions.

Chappell, Sheryl L.↗
NASA NTRS1990

Details Of Collision-Avoidance Study

Report provides background information on and detailed description of study of pilots' use of traffic-alert and collision-avoidance system (TCAS II) in simulated flights. Described in article, "Evaluation of an Aircraft-Collision-Avoidance System" (ARC-12367). Plans, forms, training narratives, scripts, questionnaires, and other information compiled.

Chappell, Sheryl L.↗
NASA NTRS1987

Independent Orbiter Assessment (IOA): Analysis of the crew equipment subsystem

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical (PCIs) items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The independent analysis results coresponding to the Orbiter crew equipment hardware are documented. The IOA analysis process utilized available crew equipment hardware drawings and schematics for defining hardware assemblies, components, and hardware items. Each level of hardware was evaluated and analyzed for possible failure modes and effects. Criticality was assigned based upon the severity of the effect for each failure mode. Of the 352 failure modes analyzed, 78 were determined to be PCIs.

Sinclair, Susan↗