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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 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

A general study of techniques for ultraviolet astrophysical studies on space vehicles

Recent accomplishments in three areas of UV instrumentation for space astronomy are discussed. These areas include reliable UV photometry, sensitive photon-detection techniques, and precise telescope pointing. Calibration facilities for spectrometers designed to operate in the spectral regions above 1200 A and down to 400 A are described which employ a series of diodes calibrated against electron synchrotron radiation as well as other radiometric standards. Improvements in photon-detection sensitivity achieved with the aid of pulse-counting electronics and multispectral detectors are reported, and the technique of precise subarcsecond telescope pointing is briefly noted. Some observational results are presented which demonstrate the advantages and precision of the instruments and techniques considered.

Moos, H. W.↗
NASA NTRS1979

Accelerated stress testing of terrestrial solar cells

A program to investigate the reliability characteristics of unencapsulated low-cost terrestrial solar cells using accelerated stress testing is described. Reliability (or parametric degradation) factors appropriate to the cell technologies and use conditions were studied and a series of accelerated stress tests was synthesized. An electrical measurement procedure and a data analysis and management system was derived, and stress test fixturing and material flow procedures were set up after consideration was given to the number of cells to be stress tested and measured and the nature of the information to be obtained from the process. Selected results and conclusions are presented.

Prince, J. L.↗
NASA NTRS1981

Small gas-turbine combustor study: Fuel injector evaluation

As part of a continuing effort at the Lewis Research Center to improve performance, emissions, and reliability of turbine machinery, an investigation of fuel injection technique and effect of fuel type on small gas turbine combustors was undertaken. Performance and pollutant emission levels are documented over a range of simulated flight conditions for a reverse flow combustor configuration using simplex pressure-atomizing, spill-flow return, and splash cone airblast injectors. A parametric evaluation of the effect of increased combustor loading with each of the fuel injector types was obtained. Jet A and an experimental referee broad specification fuel were used to determine the effect of fuel type.

Norgren, C. T.↗
NASA NTRS1981

Small gas-turbine combustor study - Fuel injector evaluation

As part of a continuing effort at the Lewis Research Center to improve performance, emissions, and reliability of turbine machinery, an investigation was undertaken to determine the effect of fuel injection technique and fuel type on similar improvements for small gas-turbine combustors. Performance and pollutant emission levels are documented over a range of simulated flight conditions for a reverse-flow combustor configuration using simplex pressure-atomizing, spill-flow return, and splash cone airblast injectors. A parametric evaluation of the effect of increased combustor loading with each of the fuel injector types was obtained. Jet A and an experimental referee broad specification fuel were used to determine and compare effects of burning different types of fuels in a small experimental gas turbine combustor.

Norgren, C. T.↗
NASA NTRS1981

Heat balance statistics derived from four-dimensional assimilations with a global circulation model

The reported investigation was conducted to develop a reliable procedure for obtaining the diabatic and vertical terms required for atmospheric heat balance studies. The method developed employs a four-dimensional assimilation mode in connection with the general circulation model of NASA's Goddard Laboratory for Atmospheric Sciences. The initial analysis was conducted with data obtained in connection with the 1976 Data Systems Test. On the basis of the results of the investigation, it appears possible to use the model's observationally constrained diagnostics to provide estimates of the global distribution of virtually all of the quantities which are needed to compute the atmosphere's heat and energy balance.

Schubert, S. D.↗
NASA NTRS1984

Drives and benefits overview

The major technology issues for an advanced orbital transfer vehicles (OTV) engine to be used in conjunction with a space based, reusable orbit transfer vehicle are discussed. The results of the space station studies as they relate to the OTV and the ground rules and guidelines for a reusable OTV vehicle study are reviewed. The technology drives and benefit categories such as mission versatility, increased reliability or reduced cost are presented. The technology drivers and the associated benefits are covered with regard to relative significance and impact on the ongoing OTV engine technology program. It is recommended that because of the broad range of mission requirements and the long term potential cost benefits a new engine is needed for the space based reusable OTV.

Mcintyre, S. D.↗
NASA NTRS1984

Hydrological planning studies using Landsat-4 Thematic Mapper (TM)

NASA, in cooperation with the U.S. Army Corps of Engineers, is evaluating the capabilities of Landsat 4 Thematic Mapper (TM) data for environmental and hydrological applications. Attention is given to the results of studies conducted at the Clinton River Basin in Michigan and the eastern shore of the Chesapeake Bay in Maryland. In the former, the evaluation conducted was for the band combinations: (1) 2, 3, and 4; (2) 3, 4, and 5; (3) 3, 4, 5, and 6; and (4) all seven bands. In the latter case, Multispectral Scanner (MSS) and TM data were classified for combinations (1), (3) and (4). Wetland classification accuracy for the 7-band TM data in this study was found to be 9 percent higher than with MSS data, allowing more reliable and accurate monitoring.

Gervin, J. C.↗
NASA NTRS1985

Design optimization for a space based, reusable orbit transfer vehicle

Future NASA and DOD missions will benefit from high performance, reusable orbit transfer vehicles. With the advent of a space station, advanced engine technology, and various new vehicle concepts, reusable orbit transfer vehicles that provide significant economic benefits and mission capability improvements will be realized. Engine and vehicle design criteria previously have lacked definition with regard to issues such as space basing and servicing, man-rating and reliability, performance, mission flexibility, and life cycle cost for a reusable vehicle. The design study described here has resulted in the definition of a reusable orbit transfer vehicle concept and subsequent recommendations for the design criteria of an advanced LO2/LH2 engine. These design criteria include number of engines per vehicle, nozzle design, etc. The major characteristics of the vehicle preliminary design include low lift to drag aerocapture capability, a main propulsion system failure criteria of fail operational/fail safe, and either two main engines with a high performance attitude control system for back-up or three main engines with which to meet this failure criteria. In addition, a maintenance approach has been established for the advanced vehicle concept.

Redd, L.↗
NASA NTRS1986

Thermoluminescence of Antarctic meteorites: A rapid screening technique for terrestrial age estimation, pairing studies and identification of specimens with unusual prefall histories

Thermoluminescence (TL) is a promising technique for rapid screening of the large numbers of Antarctic meteorites, permitting identification of interesting specimens that can then be studied in detail by other, more definite techniques. Specifically, TL permits determination of rough terrestrial age, identification of potential paired groups and location of specimens with unusual pre-fall histories. Meteorites with long terrestrial ages are particularly valuable for studying transport and weathering mechanisms. Pairing studies are possible because TL variations among meteorites are large compared to variations within individual objects, especially for natural TL. Available TL data for several L3 fragments, three of which were paired by other techniques, are presented as an example of the use of TL parameters in pairing studies. Additional TL measurements, specifically a blind test, are recommended to satisfactorily establish the reliability of this pairing property. The TL measurements also identify fragments with unusual pre-fall histories, such an near-Sun orbits.

Sutton, S. R.↗
NASA NTRS1988

Numerical results for axial flow compressor instability

Using Cornell's supercomputing facilities, an extensive study of the Moore-Greitzer model was carried out, which gives accurate and reliable information about compressor instability. The bifurcation analysis in the companion paper shows the dependence of the mode of compressor response on the shape of the rotating stall characteristic. The numerical results verify and extend this with a more accurate representation of the characteristic. The effect of the parameters on the shape of the rotating stall characteristic is investigated, and it is found that the parameters with the strongest effects are the inlet length, and the shape of the compressor pressure rise vs. mass flow diagram (i.e. tall diagrams vs. shallow diagrams). The effects of inlet guide vane loss on the characteristic are discussed.

Mccaughan, F. E.↗
NASA NTRS1989

Multi-version software reliability through fault-avoidance and fault-tolerance

A number of experimental and theoretical issues associated with the practical use of multi-version software to provide run-time tolerance to software faults were investigated. A specialized tool was developed and evaluated for measuring testing coverage for a variety of metrics. The tool was used to collect information on the relationships between software faults and coverage provided by the testing process as measured by different metrics (including data flow metrics). Considerable correlation was found between coverage provided by some higher metrics and the elimination of faults in the code. Back-to-back testing was continued as an efficient mechanism for removal of un-correlated faults, and common-cause faults of variable span. Software reliability estimation methods was also continued based on non-random sampling, and the relationship between software reliability and code coverage provided through testing. New fault tolerance models were formulated. Simulation studies of the Acceptance Voting and Multi-stage Voting algorithms were finished and it was found that these two schemes for software fault tolerance are superior in many respects to some commonly used schemes. Particularly encouraging are the safety properties of the Acceptance testing scheme.

Vouk, Mladen A.↗
NASA NTRS1989

ALS rocket engine combustion devices design and demonstration

Work performed during Phase one is summarized and the significant technical and programmatic accomplishments occurring during this period are documented. Besides a summary of the results, methodologies, trade studies, design, fabrication, and hardware conditions; the following are included: the evolving Maintainability Plan, Reliability Program Plan, Failure Summary and Analysis Report, and the Failure Mode and Effect Analysis.

Arreguin, Steve↗
NASA NTRS1991

Low Pressure Nuclear Thermal Rocket (LPNTR) concept

A background and a description of the low pressure nuclear thermal system are presented. Performance, mission analysis, development, critical issues, and some conclusions are discussed. The following subject areas are covered: LPNTR's inherent advantages in critical NTR requirement; reactor trade studies; reference LPNTR; internal configuration and flow of preliminary LPNTR; particle bed fuel assembly; preliminary LPNTR neutronic study results; multiple LPNTR engine concept; tank and engine configuration for mission analysis; LPNTR reliability potential; LPNTR development program; and LPNTR program costs.

Ramsthaler, J. H.↗
NASA NTRS1993

HL-20 subsystem design

The NASA Langley Research Center has been developing a lifting-body configuration called the HL-20 for potential application as a personnel launch system orbiter that will provide the crew changeout at the Space Station Freedom. The objectives have been to provide an alternate manned access to space with a more cost-effective, efficient, reliable, and safer system for the routine transportation of people to LEO. The detailed study of this concept includes the subsystem design, flight software sizing, and mass properties that are discussed in this paper. The goals were to develop a subsystem complement to maximize operational efficiency with minimum development costs while using current technology. Subsystem selection and trade studies showed that current technology components will provide the required performance and operational effectiveness. Many of the selected components have Shuttle flight histories or considerable development heritage from other programs that will help minimize development costs.

Stone, H. W.↗
NASA NTRS1958

Development of X-15 escape system

The content of this paper is concerned primarily with testing and determining the suitability of such factors as cockpit mobility, escape potential, mechanical reliability, post-separation performance, and airframe compatibility. Integrating the results of the various studies led to the conclusion that the pressure suit in combination with the open ejection seat would best satisfy the X-15 emergency-escape requirements by virtue of elimination of capsule-imposed penalties on aircraft performance and significant reduction in development time.

Hegenwald, J F↗
NASA NTRS1994

Thermochemistry of dense hydrous magnesium silicates

Recent experimental investigations under mantle conditions have identified a suite of dense hydrous magnesium silicate (DHMS) phases that could be conduits to transport water to at least the 660 km discontinuity via mature, relatively cold, subducting slabs. Water released from successive dehydration of these phases during subduction could be responsible for deep focus earthquakes, mantle metasomatism and a host of other physico-chemical processes central to our understanding of the earth's deep interior. In order to construct a thermodynamic data base that can delineate and predict the stability ranges for DHMS phases, reliable thermochemical and thermophysical data are required. One of the major obstacles in calorimetric studies of phases synthesized under high pressure conditions has been limitation due to the small (less than 5 mg) sample mass. Our refinement of calorimeter techniques now allow precise determination of enthalpies of solution of less than 5 mg samples of hydrous magnesium silicates. For example, high temperature solution calorimetry of natural talc (Mg(0.99) Fe(0.01)Si4O10(OH)2), periclase (MgO) and quartz (SiO2) yield enthalpies of drop solution at 1044 K to be 592.2 (2.2), 52.01 (0.12) and 45.76 (0.4) kJ/mol respectively. The corresponding enthalpy of formation from oxides at 298 K for talc is minus 5908.2 kJ/mol agreeing within 0.1 percent to literature values.

Bose, Kunal↗
NASA NTRS1994

Reliability analysis in the Office of Safety, Environmental, and Mission Assurance (OSEMA)

The technical personnel in the SEMA office are working to provide the highest degree of value-added activities to their support of the NASA Langley Research Center mission. Management perceives that reliability analysis tools and an understanding of a comprehensive systems approach to reliability will be a foundation of this change process. Since the office is involved in a broad range of activities supporting space mission projects and operating activities (such as wind tunnels and facilities), it was not clear what reliability tools the office should be familiar with and how these tools could serve as a flexible knowledge base for organizational growth. Interviews and discussions with the office personnel (both technicians and engineers) revealed that job responsibilities ranged from incoming inspection to component or system analysis to safety and risk. It was apparent that a broad base in applied probability and reliability along with tools for practical application was required by the office. A series of ten class sessions with a duration of two hours each was organized and scheduled. Hand-out materials were developed and practical examples based on the type of work performed by the office personnel were included. Topics covered were: Reliability Systems - a broad system oriented approach to reliability; Probability Distributions - discrete and continuous distributions; Sampling and Confidence Intervals - random sampling and sampling plans; Data Analysis and Estimation - Model selection and parameter estimates; and Reliability Tools - block diagrams, fault trees, event trees, FMEA. In the future, this information will be used to review and assess existing equipment and processes from a reliability system perspective. An analysis of incoming materials sampling plans was also completed. This study looked at the issues associated with Mil Std 105 and changes for a zero defect acceptance sampling plan.

Kauffmann, Paul J.↗
NASA NTRS1995

A highly reliable, high performance open avionics architecture for real time Nap-of-the-Earth operations

An Army Fault Tolerant Architecture (AFTA) has been developed to meet real-time fault tolerant processing requirements of future Army applications. AFTA is the enabling technology that will allow the Army to configure existing processors and other hardware to provide high throughput and ultrahigh reliability necessary for TF/TA/NOE flight control and other advanced Army applications. A comprehensive conceptual study of AFTA has been completed that addresses a wide range of issues including requirements, architecture, hardware, software, testability, producibility, analytical models, validation and verification, common mode faults, VHDL, and a fault tolerant data bus. A Brassboard AFTA for demonstration and validation has been fabricated, and two operating systems and a flight-critical Army application have been ported to it. Detailed performance measurements have been made of fault tolerance and operating system overheads while AFTA was executing the flight application in the presence of faults.

Harper, Richard E.↗