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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 1,189 records · Page 66
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

A general software reliability process simulation technique

The structure and rationale of the generalized software reliability process, together with the design and implementation of a computer program that simulates this process are described. Given assumed parameters of a particular project, the users of this program are able to generate simulated status timelines of work products, numbers of injected anomalies, and the progress of testing, fault isolation, repair, validation, and retest. Such timelines are useful in comparison with actual timeline data, for validating the project input parameters, and for providing data for researchers in reliability prediction modeling.

Tausworthe, Robert C.↗
NASA NTRS1991

Development of BEM for ceramic composites

It is evident that for proper micromechanical analysis of ceramic composites, one needs to use a numerical method that is capable of idealizing the individual fibers or individual bundles of fibers embedded within a three-dimensional ceramic matrix. The analysis must be able to account for high stress or temperature gradients from diffusion of stress or temperature from the fiber to the ceramic matrix and allow for interaction between the fibers through the ceramic matrix. The analysis must be sophisticated enough to deal with the failure of fibers described by a series of increasingly sophisticated constitutive models. Finally, the analysis must deal with micromechanical modeling of the composite under nonlinear thermal and dynamic loading. This report details progress made towards the development of a boundary element code designed for the micromechanical studies of an advanced ceramic composite. Additional effort has been made in generalizing the implementation to allow the program to be applicable to real problems in the aerospace industry.

Henry, D. P.↗
NASA NTRS1990

Proceedings of the Fifteenth Annual Software Engineering Workshop

The Software Engineering Laboratory (SEL) is an organization sponsored by GSFC and created for the purpose of investigating the effectiveness of software engineering technologies when applied to the development of applications software. The goals of the SEL are: (1) to understand the software development process in the GSFC environment; (2) to measure the effect of various methodologies, tools, and models on this process; and (3) to identify and then to apply successful development practices. Fifteen papers were presented at the Fifteenth Annual Software Engineering Workshop in five sessions: (1) SEL at age fifteen; (2) process improvement; (3) measurement; (4) reuse; and (5) process assessment. The sessions were followed by two panel discussions: (1) experiences in implementing an effective measurement program; and (2) software engineering in the 1980's. A summary of the presentations and panel discussions is given.

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NASA NTRS1989

STS investigators' guide

The capability of the Space Transportation System (STS), the Space Shuttle, to support crew tended and free flyer research in low Earth orbit has opened new possibilities for science in space. For the first time, research equipment can be put into orbit routinely, operated in either a shirtsleeve environment or exposed to space, and then returned to the investigator. NASA, operator of the Shuttle, has implemented a variety of programs to ensure that anyone with a worthy research idea can take advantage of this opportunity. Investigators ranging from high school students to renowned space scientists have already used the Shuttle as a platform for making Earth, atmospheric, and astronomical observations; for performing space plasma physics measurements; and for exploring the effects of microgravity on living organisms and physical processes. For investigators considering a flight experiment for the first time, this guide explains what the Shuttle has to offer, how to arrange to fly an experiment, and what to expect once preparations for the flight are under way.

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NASA NTRS1992

A multinational Mars mission for the International Space University

The International Space University's 1991 design project activity has yielded a report on the organization and implementation of a multinational program for manned exploration of Mars; the organization encompasses a political as well as a technical component. This International Manned Mission employs an artificial-gravity spacecraft with nuclear-electric propulsion for interplanetary transfer. An unmanned cargo mission precedes the piloted flights to increase the mass deliverable to Mars, as well as to serve as a testbed for interplanetary vehicle design.

Mendell, Wendell W.↗
NASA NTRS1992

Probabilistic material degradation model for aerospace materials subjected to high temperature, mechanical and thermal fatigue, and creep

A probabilistic general material strength degradation model has been developed for structural components of aerospace propulsion systems subjected to diverse random effects. The model has been implemented in two FORTRAN programs, PROMISS (Probabilistic Material Strength Simulator) and PROMISC (Probabilistic Material Strength Calibrator). PROMISS calculates the random lifetime strength of an aerospace propulsion component due to as many as eighteen diverse random effects. Results are presented in the form of probability density functions and cumulative distribution functions of lifetime strength. PROMISC calibrates the model by calculating the values of empirical material constants.

Boyce, L.↗
NASA NTRS1992

Reducing transport delay through improvements in real-time program flow

This paper describes the process of measuring and reducing software-transport delays through careful analysis, and modifications of real-time programs. A 737 program is analyzed and modified to improve the simulation overall transport delay by approximately 30 percent. The transport delay was improved through modification to the real-time program flow and the implementation of quaternions in the calculation of the math model.

Smith, R. M.↗
NASA NTRS1992

Fingerprinting of Materials

Recent issues emerging in our fiscal and ecological environments have promulgated that federal agencies shall promote activities which respond to the improvement of both. In response to these developments, the National Aeronautics and Space Administration (NASA) has undertaken an innovative approach to improve the control of materials used in all NASA manufacturing activities. In concert with this goal, NASA is requiring that its contractors and their sub-contractors perform a more intensive consolidation of technologies that can provide an accounting of materials, which includes in-coming materials, materials in process, end-products and waste materials. The purpose of this handbook is to provide guidelines to NASA and its contractor personnel for the planning and implementation of chemical fingerprinting programs and to illustrate the chemical and statistical fundamentals needed for successful use of chemical fingerprinting.

Workman, Gary L↗
NASA NTRS1992

Prediction of thermal cycling induced matrix cracking

Thermal fatigue has been observed to cause matrix cracking in laminated composite materials. A method is presented to predict transverse matrix cracks in composite laminates subjected to cyclic thermal load. Shear lag stress approximations and a simple energy-based fracture criteria are used to predict crack densities as a function of temperature. Prediction of crack densities as a function of thermal cycling is accomplished by assuming that fatigue degrades the material's inherent resistance to cracking. The method is implemented as a computer program. A simple experiment provides data on progressive cracking of a laminate with decreasing temperature. Existing data on thermal fatigue is also used. Correlations of the analytical predictions to the data are very good. A parametric study using the analytical method is presented which provides insight into material behavior under cyclical thermal loads.

Mcmanus, Hugh L.↗
NASA NTRS1992

A Spatial Analysis and Modeling System (SAMS) for environment management

This is a proposal to develop a uniform global environmental data gathering and distribution system to support the calibration and validation of remotely sensed data. SAMS is based on an enhanced version of FE MA's Integrated Emergency Management Information Systems and the Department of Defense's Air Land Battlefield Environment Software Systems. This system consists of state-of-the-art graphics and visualization techniques, simulation models, database management and expert systems for conducting environmental and disaster preparedness studies. This software package will be integrated into various Landsat and UNEP-GRID stations which are planned to become direct readout stations during the EOS timeframe. This system would be implemented as a pilot program to support the Tropical Rainfall Measuring Mission (TRMM). This will be a joint NASA-FEMA-University-Industry project.

Vermillion, Charles H.↗
NASA NTRS1993

The 1992 Langley Aerospace Research Summer Scholars (LARSS) program

The overwhelming majority of the LARSS participants rated their overall summer research experience as good or excellent. Even though the 1992 LARSS Program has met its goals, all areas of the program need to be considered for continuous improvement. Of the various recommendations provided by the participants, the following will be implemented in the 1993 LARSS Program: (1) LARSS participants will be housed in two or three apartment complexes; (2) mentors will be encouraged to contact their student before the beginning of the LARSS Program; (3) LARSS participants will be notified of a tentative payroll schedule before the Program begins; (4) LARSS participants will be strongly encouraged to give an oral presentation on their research project in their respective Divisions; and (5) a Career Conference, in conjunction with a forum where the participants can share their individual research projects will be held. The participant recommendations made in the 1992 LARSS Student Exit Survey will ensure a more successful and improved LARSS Program in 1993.

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NASA NTRS1992

Numerical evaluation of single central jet for turbine disk cooling

The cooling arrangement of the Space Shuttle Main Engine High Pressure Oxidizer Turbopump (HPOTP) incorporates two jet rings, each of which produces 19 high-velocity coolant jets. At some operating conditions, the frequency of excitation associated with the 19 jets coincides with the natural frequency of the turbine blades, contributing to fatigue cracking of blade shanks. In this paper, an alternate turbine disk cooling arrangement, applicable to disk faces of zero hub radius, is evaluated, which consists of a single coolant jet impinging at the center of the turbine disk. Results of the CFD analysis show that replacing the jet ring with a single central coolant jet in the HPOTP leads to an acceptable thermal environment at the disk rim. Based on the predictions of flow and temperature fields for operating conditions, the single central jet cooling system was recommended for implementation into the development program of the Technology Test Bed Engine at NASA Marshall Space Flight Center.

Subbaraman, M. R.↗
NASA NTRS1985

Tropical upper tropospheric motion field

Upper tropospheric cloud motion vectors and commercial aircraft wind reports have enabled a detailed definition of the motion field. These two data sets have enhanced our observational capability since the launch of 4 to 5 geostationary satellites around the globe and the implementation of the ASDAR program. A sample is illustrated of recent commercial aircraft wind reports at the 300, 250, and 200 mb surfaces over parts of the Pacific Ocean, North America, and Atlantic Ocean. This data coverage is impressive. The rms difference between these data and those obtained from rawinsonde ascents (colocated) is around + or - 4 m/s. In a recent study of the cloud winds, from geostationary satellites, Johnson (1984) noted almost 15 m/s vector wind differences between estimates from GMS, GOES, and METEOSAT with respect to the rawinsonde observations. These results are illustrated based on the assessment of Johnson (1984). Overall, the commercial aircraft winds are the more accurate of these two observing systems. However, it is apparent that because of the sparcity of airline routes across southern oceans, one has to rely rather heavily on the cloud winds as a primary data source over the tropical southern oceans. The operational rawinsonde coverage over the tropics is generally very poor. The overall data coverage based primarily on the collections at the ECWMF are shown.

Krishnamurti, T. N.↗
NASA NTRS1991

An interferometric spectral mapper for the Cassini mission to Saturn and Titan

The research reported resulted in a detailed proposal for the Cassini Mission that addressed fundamental atmospheric structure and composition questions for both Saturn and Titan. Due to the brief time available between the initiation of the research and the proposal date, it was necessary to develop the science goals in close synchronicity with the instrument design. A major goal of the program was to acquire, implement, and test SWIR and MWIR arrays suitable for use with the DIGITAL ARRAY SCANNED INTERFEROMETERS, (DASI's), for the extended goal of developing DASI's for a range of spectral mapping research in solar system exploration. These goals were all reached or exceeded in the course of this work.

Smith, William Hayden↗
NASA NTRS1994

Development of a nondestructive vibration technique for bond assessment of Space Shuttle tiles

This final report describes the achievements of the above titled project. The project is funded by NASA-KSC (Grant No. NAG 10-0117) for the period of 1 Jan. to 31 Dec. 1993. The purpose of this project was to develop a nondestructive, noncontact technique based on 'vibration signature' of tile systems to quantify the bond conditions of the thermal protection system) tiles of Space Shuttle orbiters. The technique uses a laser rapid scan system, modal measurements, and finite element modeling. Finite element models were developed for tiles bonded to both clamped and deformable integrated skin-stringer orbiter mid-fuselage. Results showed that the size and location of a disbonded tile can be determined from frequency and mode shape information. Moreover, a frequency response survey was used to quickly identify the disbonded tiles. The finite element results were compared with experimentally determined frequency responses of a 17-tile test panel, where a rapidscan laser system was employed. An excellent degree of correlation between the mathematical simulation and experimental results was realized. An inverse solution for single-tile assemblies was also derived and is being implemented into a computer program that can interact with the modal testing software. The output of the program displays the size and location of disbond. This program has been tested with simulated input (i.e., finite element data), and excellent agreement between predicted and simulated disbonds was shown. Finally, laser vibration imaging and acoustic emission techniques were shown to be well suited for detecting and monitoring the progressive damage in Graphite/Epoxy composite materials.

Moslehy, Faissal A.↗
NASA NTRS1994

Design and Implementation of a Distributed Version of the NASA Engine Performance Program

Distributed NEPP is a new version of the NASA Engine Performance Program that runs in parallel on a collection of Unix workstations connected through a network. The program is fault-tolerant, efficient, and shows significant speed-up in a multi-user, heterogeneous environment. This report describes the issues involved in designing distributed NEPP, the algorithms the program uses, and the performance distributed NEPP achieves. It develops an analytical model to predict and measure the performance of the simple distribution, multiple distribution, and fault-tolerant distribution algorithms that distributed NEPP incorporates. Finally, the appendices explain how to use distributed NEPP and document the organization of the program's source code.

Cours, Jeffrey T.↗
NASA NTRS1993

Synthetic vision system flight test results and lessons learned

Honeywell Systems and Research Center developed and demonstrated an active 35 GHz Radar Imaging system as part of the FAA/USAF/Industry sponsored Synthetic Vision System Technology Demonstration (SVSTD) Program. The objectives of this presentation are to provide a general overview of flight test results, a system level perspective that encompasses the efforts of the SVSTD and Augmented VIsual Display (AVID) programs, and more importantly, provide the AVID workshop participants with Honeywell's perspective on the lessons that were learned from the SVS flight tests. One objective of the SVSTD program was to explore several known system issues concerning radar imaging technology. The program ultimately resolved some of these issues, left others open, and in fact created several new concerns. In some instances, the interested community has drawn improper conclusions from the program by globally attributing implementation specific issues to radar imaging technology in general. The motivation for this presentation is therefore to provide AVID researchers with a better understanding of the issues that truly remain open, and to identify the perceived issues that are either resolved or were specific to Honeywell's implementation.

Radke, Jeffrey↗
NASA NTRS1992

Modeling of Thermal Barrier Coatings

The project examined the effectiveness of studying the creep behavior of thermal barrier coating system through the use of a general purpose, large strain finite element program, NIKE2D. Constitutive models implemented in this code were applied to simulate thermal-elastic and creep behavior. Four separate ceramic-bond coat interface geometries were examined in combination with a variety of constitutive models and material properties. The reason for focusing attention on the ceramic-bond coat interface is that prior studies have shown that cracking occurs in the ceramic near interface features which act as stress concentration points. The model conditions examined include: (1) two bond coat coefficient of thermal expansion curves; (2) the creep coefficient and creep exponent of the bond coat for steady state creep; (3) the interface geometry; and (4) the material model employed to represent the bond coat, ceramic, and superalloy base.

Ferguson, B. L.↗