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Results for “Reliability and Maintainability”

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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Improving a data-acquisition software system with abstract data type components

Abstract data types and object-oriented design are active research areas in computer science and software engineering. Much of the interest is aimed at new software development. Abstract data type packages developed for a discontinued software project were used to improve a real-time data-acquisition system under maintenance. The result saved effort and contributed to a significant improvement in the performance, maintainability, and reliability of the Goldstone Solar System Radar Data Acquisition System.

Howard, S. D.↗
NASA NTRS1989

On the feasibility of a spaceborne fault-tolerant hypercube

The feasibility of implementing a fault-tolerant hypercube architecture for space applications is discussed. Node-level architectures and designs are considered and a first-order reliability model is presented. It is shown how error recovery can be implemented using program rollback or roll-forward techniques. Shared memory augmentations to the message-passing structure can be used to get around the inefficiencies of multicomputers to provide efficient use of hardware to achieve the needed reliabilities while maintaining performance.

Rennels, David A.↗
NASA NTRS1989

Designing an infrared system to map and detect wildland fires

The 'Firefly' project is developing an infrared remote sensing system to provide near real-time wildland fire information for fire management and suppression. Recent technological advances in several areas now allow the design of an end-to-end, infrared system to map and detect wildland fires. The system components will include an airborne infrared sensor, automatic onboard signal and data processing, telecommunications link, and integration into a ground data terminal. The system will provide improved performance over current systems in terms of increased timeliness of data delivery, quantifiable accuracy, data consistency, reliability, and maintainability. The system will be the next generation of wildland fire mapping and detection system for the United States Forest Service.

Nichols, J. David↗
NASA NTRS1990

A Unified Statistical Rain-Attenuation Model for Communication Link Fade Predictions and Optimal Stochastic Fade Control Design Using a Location-Dependent Rain-Statistic Database

A static and dynamic rain-attenuation model is presented which describes the statistics of attenuation on an arbitrarily specified satellite link for any location for which there are long-term rainfall statistics. The model may be used in the design of the optimal stochastic control algorithms to mitigate the effects of attenuation and maintain link reliability. A rain-statistics data base is compiled, which makes it possible to apply the model to any location in the continental U.S. with a resolution of 0-5 degrees in latitude and longitude. The model predictions are compared with experimental observations, showing good agreement.

Manning, Robert M.↗
NASA NTRS1990

U.S. Space Station Freedom waste fluid disposal system with consideration of hydrazine waste gas injection thrusters

The results are reported of a study of various methods for propulsively disposing of waste gases. The options considered include hydrazine waste gas injection, resistojets, and eutectic salt phase change heat beds. An overview is given of the waste gas disposal system and how hydrozine waste gas injector thruster is implemented within it. Thruster performance for various gases are given and comparisons with currently available thruster models are made. The impact of disposal on station propellant requirements and electrical power usage are addressed. Contamination effects, reliability and maintainability assessments, safety issues, and operational scenarios of the waste gas thruster and disposal system are considered.

Winters, Brian A.↗
NASA NTRS1989

Advanced Launch System propulsion focused technology liquid methane turbopump technical implementation plan

This program will focus on the integration of all functional disciplines of the design, manufacturing, materials, fabrication and producibility to define and demonstrate a highly reliable, easily maintained, low cost liquid methane turbopump as a component for the STBE (Space Transportation Booster Engine) using the STME (main engine) oxygen turbopump. A cost model is to be developed to predict the recurring cost of production hardware and operations. A prime objective of the program is to design the liquid methane turbopump to be used in common with a LH2 turbopump optimized for the STME. Time phasing of the effort is presented and interrelationship of the tasks is defined. Major subcontractors are identified and their roles in the program are described.

Csomor, A.↗
NASA NTRS1991

Rule groupings: A software engineering approach towards verification of expert systems

Currently, most expert system shells do not address software engineering issues for developing or maintaining expert systems. As a result, large expert systems tend to be incomprehensible, difficult to debug or modify and almost impossible to verify or validate. Partitioning rule based systems into rule groups which reflect the underlying subdomains of the problem should enhance the comprehensibility, maintainability, and reliability of expert system software. Attempts were made to semiautomatically structure a CLIPS rule base into groups of related rules that carry the same type of information. Different distance metrics that capture relevant information from the rules for grouping are discussed. Two clustering algorithms that partition the rule base into groups of related rules are given. Two independent evaluation criteria are developed to measure the effectiveness of the grouping strategies. Results of the experiment with three sample rule bases are presented.

Mehrotra, Mala↗
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 NTRS1990

Evaluation of undeveloped rocket engine cycle applications to advanced transportation

Undeveloped pump-fed, liquid propellant rocket engine cycles were assessed and evaluated for application to Next Manned Transportation System (NMTS) vehicles, which would include the evolving Space Transportation System (STS Evolution), the Personnel Launch System (PLS), and the Advanced Manned Launch System (AMLS). Undeveloped engine cycles selected for further analysis had potential for increased reliability, more maintainability, reduced cost, and improved (or possibly level) performance when compared to the existing SSME and proposed STME engines. The split expander (SX) cycle, the full flow staged combustion (FFSC) cycle, and a hybrid version of the FFSC, which has a LOX expander drive for the LOX pump, were selected for definition and analysis. Technology requirements and issues were identified and analyses of vehicle systems weight deltas using the SX and FFSC cycles in AMLS vehicles were performed. A strawman schedule and cost estimate for FFSC subsystem technology developments and integrated engine system demonstration was also provided.

Source record↗
NASA NTRS1990

NACA/NASA supersonic flight research

The use of experimental and testbed vehicles and their contributions to fundamental problem solving and overall vehicle characteristics are presented. A chronological description of aircraft from the first supersonic flight in the X-1 through the development of the F-100 series, the X-15, and the B-1 is given. One of the early significant contributions made was the development of the all-moving stabilizer that solved the problem associated with high-speed tuck and the trim requirements of entry into the supersonic regime. Some wind tunnel/flight drag characteristics studies associated with the B-1 bomber involving flexibility effects and wind tunnel effects are shown. Finally, the evolution of digital systems to enhance maintainability and reliability and to reduce the work load in the cockpit are described.

Ayers, T. G.↗
NASA NTRS1989

Dynamic systems-engineering process - The application of concurrent engineering

A system engineering methodology is described which enables users, particulary NASA and DOD, to accommodate changing needs; incorporate emerging technologies; identify, quantify, and manage system risks; manage evolving functional requirements; track the changing environment; and reduce system life-cycle costs. The approach is a concurrent, dynamic one which starts by constructing a performance model defining the required system functions and the interrelationships. A detailed probabilistic risk assessment of the system elements and their interrelationships is performed, and quantitative analysis of the reliability and maintainability of an engineering system allows its different technical and process failure modes to be identified and their probabilities to be computed. Decision makers can choose technical solutions that maximize an objective function and minimize the probability of failure under resource constraints.

Wiskerchen, Michael J.↗
NASA NTRS1991

The determination of operational and support requirements and costs during the conceptual design of space systems

The primary objective is to develop a methodology for predicting operational and support parameters and costs of proposed space systems. The first phase consists of: (1) the identification of data sources; (2) the development of a methodology for determining system reliability and maintainability parameters; (3) the implementation of the methodology through the use of prototypes; and (4) support in the development of an integrated computer model. The phase 1 results are documented and a direction is identified to proceed to accomplish the overall objective.

Ebeling, Charles↗
NASA NTRS1990

Early experiences building a software quality prediction model

Early experiences building a software quality prediction model are discussed. The overall research objective is to establish a capability to project a software system's quality from an analysis of its design. The technical approach is to build multivariate models for estimating reliability and maintainability. Data from 21 Ada subsystems were analyzed to test hypotheses about various design structures leading to failure-prone or unmaintainable systems. Current design variables highlight the interconnectivity and visibility of compilation units. Other model variables provide for the effects of reusability and software changes. Reported results are preliminary because additional project data is being obtained and new hypotheses are being developed and tested. Current multivariate regression models are encouraging, explaining 60 to 80 percent of the variation in error density of the subsystems.

Agresti, W. W.↗
NASA NTRS1990

Rotorcraft transmissions

Highlighted here is that portion of the Lewis Research Center's helicopter propulsion systems program that deals with drive train technology and the related mechanical components. The major goals of the program are to increase life, reliability, and maintainability, to reduce weight, noise, and vibration, and to 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 advanced configurations and new analytical tools. Finally, the plan for transmission research in the future is presented.

Coy, John J.↗
NASA NTRS1992

The determination of operational and support requirements and costs during the conceptual design of space systems

The first year of research to provide NASA support in predicting operational and support parameters and costs of proposed space systems is reported. Some of the specific research objectives were (1) to develop a methodology for deriving reliability and maintainability parameters and, based upon their estimates, determine the operational capability and support costs, and (2) to identify data sources and establish an initial data base to implement the methodology. Implementation of the methodology is accomplished through the development of a comprehensive computer model. While the model appears to work reasonably well when applied to aircraft systems, it was not accurate when used for space systems. The model is dynamic and should be updated as new data become available. It is particularly important to integrate the current aircraft data base with data obtained from the Space Shuttle and other space systems since subsystems unique to a space vehicle require data not available from aircraft. This research only addressed the major subsystems on the vehicle.

Ebeling, Charles↗
NASA NTRS1991

Thermal imaging of graphite/epoxy composite samples with fabricated defects

Consideration is given to a thermal inspection system for quickly inspecting large area composites for increased reliability and maintainability of helicopters resulting from improved quality assurance manufacturing. The infrared camera/image processor-based inspection system was used to image defects in composites. Noncontacting and single-sided measurements were performed on graphite/epoxy samples with fiber volume fraction variations, fabricated porosity, impact damage, and inclusions in incurred lay ups. These defects were imaged by determining the variations in the cooling rates caused by differences in through ply thermal diffusivity. Attention is also given to the system's sensitivity to measuring the defects due to sample thickness.

Zalameda, Joseph N.↗
NASA NTRS1992

Role of automation in the ACRV operations

The Assured Crew Return Vehicle (ACRV) will provide the Space Station Freedom with contingency means of return to earth (1) of one disabled crew member during medical emergencies, (2) of all crew members in case of accidents or failures of SSF systems, and (3) in case of interruption of the Space Shuttle flights. A wide range of vehicle configurations and system approaches are currently under study. The Program requirements focus on minimizing life cycle costs by ensuring simple operations, built-in reliability and maintainability. The ACRV philosophy of embedded operations is based on maximum use of existing facilities, resources and processes, while minimizing the interfaces and impacts to the Space Shuttle and Freedom programs. A preliminary integrated operations concept based on this philosophy and covering the ground, flight, mission support, and landing and recovery operations has been produced. To implement the ACRV operations concept, the underlying approach has been to rely on vehicle autonomy and automation, to the extent possible. Candidate functions and processes which may benefit from current or near-term automation and robotics technologies are identified. These include, but are not limited to, built-in automated ground tests and checkouts; use of the Freedom and the Orbiter remote manipulator systems, for ACRV berthing; automated passive monitoring and performance trend analysis, and periodic active checkouts during dormant periods. The major ACRV operations concept issues as they relate to the use of automation are discussed.

Sepahban, S. F.↗
NASA NTRS1993

Multi-viewpoint clustering analysis

In this paper, we address the feasibility of partitioning rule-based systems into a number of meaningful units to enhance the comprehensibility, maintainability and reliability of expert systems software. Preliminary results have shown that no single structuring principle or abstraction hierarchy is sufficient to understand complex knowledge bases. We therefore propose the Multi View Point - Clustering Analysis (MVP-CA) methodology to provide multiple views of the same expert system. We present the results of using this approach to partition a deployed knowledge-based system that navigates the Space Shuttle's entry. We also discuss the impact of this approach on verification and validation of knowledge-based systems.

Mehrotra, Mala↗