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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Status of multijunction solar cells

This paper describes Applied Solar's present activity on Multijunction (MJ) space cells. We have worked on a variety of MJ cells, both monolithic and mechanically stacked. In recent years, most effort has been directed to GaInP2/GaAs monolithic cells, grown on Ge substrates, and the status of this cell design will be reviewed here. MJ cells are in demand to provide satellite power because of the acceptance of the overwhelming importance of high efficiency to reduce the area, weight and cost of space PV power systems. The need for high efficiencies has already accelerated the production of GaAs/Ge cells, with efficiencies 18.5-19%. When users realized that MJ cells could provide higher efficiencies (from 22% to 26%) with only fractional increase in costs, the demand for production MJ cells increased rapidly. The main purpose of the work described is to transfer the MOCVD growth technology of MJ high efficiency cells to a production environment, providing all the space requirements of users.

Yeh, Y. C. M.↗
NASA NTRS2009

A Computational Approach for Probabilistic Analysis of Water Impact Simulations

NASA's development of new concepts for the Crew Exploration Vehicle Orion presents many similar challenges to those worked in the sixties during the Apollo program. However, with improved modeling capabilities, new challenges arise. For example, the use of the commercial code LS-DYNA, although widely used and accepted in the technical community, often involves high-dimensional, time consuming, and computationally intensive simulations. The challenge is to capture what is learned from a limited number of LS-DYNA simulations to develop models that allow users to conduct interpolation of solutions at a fraction of the computational time. This paper presents a description of the LS-DYNA model, a brief summary of the response surface techniques, the analysis of variance approach used in the sensitivity studies, equations used to estimate impact parameters, results showing conditions that might cause injuries, and concluding remarks.

Horta, Lucas G.↗
NASA NTRS1979

Numerical aerodynamic simulation facility feasibility study

There were three major issues examined in the feasibility study. First, the ability of the proposed system architecture to support the anticipated workload was evaluated. Second, the throughput of the computational engine (the flow model processor) was studied using real application programs. Third, the availability reliability, and maintainability of the system were modeled. The evaluations were based on the baseline systems. The results show that the implementation of the Numerical Aerodynamic Simulation Facility, in the form considered, would indeed be a feasible project with an acceptable level of risk. The technology required (both hardware and software) either already exists or, in the case of a few parts, is expected to be announced this year. Facets of the work described include the hardware configuration, software, user language, and fault tolerance.

Source record↗
NASA NTRS1994

User type certification for advanced flight control systems

Advanced avionics through flight management systems (FMS) coupled with autopilots can now precisely control aircraft from takeoff to landing. Clearly, this has been the most important improvement in aircraft since the jet engine. Regardless of the eventual capabilities of this technology, it is doubtful that society will soon accept pilotless airliners with the same aplomb they accept driverless passenger trains. Flight crews are still needed to deal with inputing clearances, taxiing, in-flight rerouting, unexpected weather decisions, and emergencies; yet it is well known that the contribution of human errors far exceed those of current hardware or software systems. Thus human errors remain, and are even increasing in percentage as the largest contributor to total system error. Currently, the flight crew is regulated by a layered system of certification: by operation, e.g., airline transport pilot versus private pilot; by category, e.g., airplane versus helicopter; by class, e.g., single engine land versus multi-engine land; and by type (for larger aircraft and jet powered aircraft), e.g., Boeing 767 or Airbus A320. Nothing in the certification process now requires an in-depth proficiency with specific types of avionics systems despite their prominent role in aircraft control and guidance.

Gilson, Richard D.↗
NASA NTRS2002

Structural Life and Reliability Metrics: Benchmarking and Verification of Probabilistic Life Prediction Codes

Over the past two decades there has been considerable effort by NASA Glenn and others to develop probabilistic codes to predict with reasonable engineering certainty the life and reliability of critical components in rotating machinery and, more specifically, in the rotating sections of airbreathing and rocket engines. These codes have, to a very limited extent, been verified with relatively small bench rig type specimens under uniaxial loading. Because of the small and very narrow database the acceptance of these codes within the aerospace community has been limited. An alternate approach to generating statistically significant data under complex loading and environments simulating aircraft and rocket engine conditions is to obtain, catalog and statistically analyze actual field data. End users of the engines, such as commercial airlines and the military, record and store operational and maintenance information. This presentation describes a cooperative program between the NASA GRC, United Airlines, USAF Wright Laboratory, U.S. Army Research Laboratory and Australian Aeronautical & Maritime Research Laboratory to obtain and analyze these airline data for selected components such as blades, disks and combustors. These airline data will be used to benchmark and compare existing life prediction codes.

Litt, Jonathan S.↗
NASA NTRS1997

Alternative Perspectives on Risk

The goal of the commercial air transport system is to provide air transportation to the flying public at an acceptable cost with minimal risk. in an ideal situation these three goals would support each other. In fact, it is sometimes the case that the goals conflict: getting passengers to their destinations on time may conflict with fixing a minor mechanical malfunction that may or may not impact safety; flying a route that will avoid turbulence, thereby providing passengers with a more comfortable ride, may consume more fuel; managing traffic density may mean aircraft are delayed or must use an approach that will result in a long taxi to their gates, costing time and fuel. Various players in the system--pilots, dispatchers, controllers, as well as managers in the airline carriers and traffic management system--make decisions every day that involve trade-offs of benefits and costs. The prospect of revisions in the air traffic management system, with shifts in responsibilities from controllers to users, including airline operations center personnel and pilots, means that individuals may be performing either new jobs or old jobs under new guidance. It will be essential to know how the various players (a) perceive the risks and benefits associated with the decisions they will make under the old and new control structures, and (b) how much risk they are willing to accept in making decisions. Risk is here defined as the probability and magnitude of negative events (after Slovic, 1987). Of primary interest are risks associated with traffic, weather, and operational factors such as schedule, fuel consumption, and passenger service. Previous research has documented differences between groups in perceptions of risks associated with both everyday and aviation related situations. Risk perception varies as a function of familiarity with the situation, degree to which one is potentially affected by the risk, the level of control one has over the situation, and one's level of experience and responsibility in the situation. In our presentation we will consider several factors that may influence differences in risk perception, risk tolerance and risk management among the three major categories of participants in the aviation system (pilots, dispatchers, and controllers). Primary factors that may affect risk attitudes (the collective term we will use for the three components of risk) include: expertise or job-specific knowledge or training, personal involvement or vulnerability to consequences, goals, time horizon (imminence of consequences), span of control and type of control, and information or technology support. These will be considered in the context of five different types of risk (physical threat, economic, social, legal, and ethical). A study designed to study differences between pilots and controllers in their perceptions and responses to traffic risks under the present and a user-preferred control situation will be described. Future studies involving dispatchers' risk perceptions regarding various types of risk will be discussed.

Davison, Jeannie↗
NASA NTRS1987

Scheduling spacecraft operations

A prototype scheduling system named MAESTRO currently under development is being used to explore possible approaches to the spacecraft operations scheduling problem. Results indicate that the appropriate combination of heuristic and other techniques can provide an acceptable solution to the scheduling problem over a wide range of operational scenarios and management approaches. These can include centralized or distributed instrument or systems control, batch or incremental scheduling, scheduling loose resource envelopes or exact profiles, and scheduling with varying degrees of user intervention. Techniques used within MAESTRO to provide this flexibility and power include constraint propagation mechanisms, multiple asynchronous processes, prioritized transaction-based command management, resource opportunity calculation, user-alterable selection and placement mechanisms, and maintenance of multiple schedules and resource profiles. These techniques and scheduling complexities requiring them are discussed.

Britt, Daniel L.↗
NASA NTRS1998

Visit to an Ocean Planet

"Visit to an Ocean Planet" is an interactive, educational CD-ROM that reveals the importance of our oceans to global climate and life. It is designed to complement middle and high school science curricula, as well as to be enjoyed by the general public. The CD-ROM allows users to explore the Gulf of Mexico with satellite data, investigate the 1997-1998 El Nino, discover "what's up" with Earth-orbiting satellites, and learn about the real life oceanographers. The curriculum background material are arranged in the context of widely accepted teaching themes. The CD-ROM also highlights results from the TOPEX/Poseidon satellite launched by NASA and the Centre National Etudes Spatiales (CNES). It has been measuring our oceans since 1992. This product is a result of NASA's commitment to involve the educational community in endeavors to inspire America's students, create learning opportunities, and enlighten inquisitive minds.

Source record↗
NASA NTRS2004

Simplifying CEA through Excel, VBA, and Subeq

Many people use compound equilibrium programs for very different reasons, varying from refrigerators to light bulbs to rockets. A commonly used equilibrium program is CEA. CEA can take various inputs such as pressure, temperature, and volume along with numerous reactants and run them through equilibrium equations to obtain valuable output information, including products formed and their relative amounts. A little over a year ago, Bonnie McBride created the program subeq with the goal to simplify the calling of CEA. Subeq was also designed to be called by other programs, including Excel, through the use of Visual Basic for Applications (VBA). The largest advantage of using Excel is that it allows the user to input the information in a colorful and user-friendly environment while allowing VBA to run subeq, which is in the form of a FORTRAN DLL (Dynamic Link Library). Calling subeq in this form makes it much faster than if it were converted to VBA. Since subeq requires such large lists of reactant and product names, all of which can't be passed in as an array, subeq had to be changed to accept very long strings of reactants and products. To pass this string and adjust the transfer of input and output parameters, the subeq DLL had to be changed. One program that does this is Compaq Visual FORTRAN, which allows DLLs to be edited, debugged, and compiled. Compaq Visual FORTRAN uses FORTRAN 90/95, which has additional features to that of FORTRAN 77. My goals this summer include finishing up the excel spreadsheet of subeq, which I started last summer, and putting it on the Internet so that others can use it without having to download my spreadsheet. To finish up the spreadsheet I will need to work on debugging current options and problems. I will also work on making it as robust as possible, so that all errors that may arise will be clearly communicated to the user. New features will be added old ones will be changed as I receive comments from people using the spreadsheet. To implement this onto the Internet, I will need to develop an XML input/output format and learn how to write HTML.

Foster, Ryan↗
NASA NTRS1987

The results of application studies for space nuclear power

The results are summarized of the studies over the last several years to identify and characterize potential applications for the SP-100 space nuclear reactor power system in powering spacecraft. SP-100 is a space power system based on a fast spectrum nuclear reactor with thermoelectric power conversion and liquid metal and heat pipe thermal transport. SP-100 reactor systems are designed to provide electric power with user designated characteristics at levels in the range from 10 to 1000 kWe. The use of nuclear reactors such as SP-100 as a power source provides a potential means of providing uninterrupted electrical power as required for many of todays space missions within acceptable cost and safety constraints.

Isenberg, L.↗
NASA NTRS2013

FY12 End of Year Report for NEPP DDR2 Reliability

This document reports the status of the NASA Electronic Parts and Packaging (NEPP) Double Data Rate 2 (DDR2) Reliability effort for FY2012. The task expanded the focus of evaluating reliability effects targeted for device examination. FY11 work highlighted the need to test many more parts and to examine more operating conditions, in order to provide useful recommendations for NASA users of these devices. This year's efforts focused on development of test capabilities, particularly focusing on those that can be used to determine overall lot quality and identify outlier devices, and test methods that can be employed on components for flight use. Flight acceptance of components potentially includes considerable time for up-screening (though this time may not currently be used for much reliability testing). Manufacturers are much more knowledgeable about the relevant reliability mechanisms for each of their devices. We are not in a position to know what the appropriate reliability tests are for any given device, so although reliability testing could be focused for a given device, we are forced to perform a large campaign of reliability tests to identify devices with degraded reliability. With the available up-screening time for NASA parts, it is possible to run many device performance studies. This includes verification of basic datasheet characteristics. Furthermore, it is possible to perform significant pattern sensitivity studies. By doing these studies we can establish higher reliability of flight components. In order to develop these approaches, it is necessary to develop test capability that can identify reliability outliers. To do this we must test many devices to ensure outliers are in the sample, and we must develop characterization capability to measure many different parameters. For FY12 we increased capability for reliability characterization and sample size. We increased sample size this year by moving from loose devices to dual inline memory modules (DIMMs) with an approximate reduction of 20 to 50 times in terms of per device under test (DUT) cost. By increasing sample size we have improved our ability to characterize devices that may be considered reliability outliers. This report provides an update on the effort to improve DDR2 testing capability. Although focused on DDR2, the methods being used can be extended to DDR and DDR3 with relative ease.

Guertin, Steven M.↗
NASA NTRS1978

Communication system analysis for manned space flight

The development of adaptive delta modulators capable of digitizing a video signal is summarized. The delta modulator encoder accepts a 4 MHz black and white composite video signal or a color video signal and encodes it into a stream of binary digits at a rate which can be adjusted from 8 Mb/s to 24 Mb/s. The output bit rate is determined by the user and alters the quality of the video picture. The digital signal is decoded using the adaptive delta modulator decoder to reconstruct the picture.

Schilling, D. L.↗
NASA NTRS2011

Reliability and Maintainability Engineering - A Major Driver for Safety and Affordability

The United States National Aeronautics and Space Administration (NASA) is in the midst of an effort to design and build a safe and affordable heavy lift vehicle to go to the moon and beyond. To achieve that, NASA is seeking more innovative and efficient approaches to reduce cost while maintaining an acceptable level of safety and mission success. One area that has the potential to contribute significantly to achieving NASA safety and affordability goals is Reliability and Maintainability (R&M) engineering. Inadequate reliability or failure of critical safety items may directly jeopardize the safety of the user(s) and result in a loss of life. Inadequate reliability of equipment may directly jeopardize mission success. Systems designed to be more reliable (fewer failures) and maintainable (fewer resources needed) can lower the total life cycle cost. The Department of Defense (DOD) and industry experience has shown that optimized and adequate levels of R&M are critical for achieving a high level of safety and mission success, and low sustainment cost. Also, lessons learned from the Space Shuttle program clearly demonstrated the importance of R&M engineering in designing and operating safe and affordable launch systems. The Challenger and Columbia accidents are examples of the severe impact of design unreliability and process induced failures on system safety and mission success. These accidents demonstrated the criticality of reliability engineering in understanding component failure mechanisms and integrated system failures across the system elements interfaces. Experience from the shuttle program also shows that insufficient Reliability, Maintainability, and Supportability (RMS) engineering analyses upfront in the design phase can significantly increase the sustainment cost and, thereby, the total life cycle cost. Emphasis on RMS during the design phase is critical for identifying the design features and characteristics needed for time efficient processing, improved operational availability, and optimized maintenance and logistic support infrastructure. This paper discusses the role of R&M in a program acquisition phase and the potential impact of R&M on safety, mission success, operational availability, and affordability. This includes discussion of the R&M elements that need to be addressed and the R&M analyses that need to be performed in order to support a safe and affordable system design. The paper also provides some lessons learned from the Space Shuttle program on the impact of R&M on safety and affordability.

Safie, Fayssal M.↗
NASA NTRS2016

ISS Double-Gimbaled CMG Subsystem Simulation Using the Agile Development Method

This paper presents an evolutionary approach in simulating a cluster of 4 Control Moment Gyros (CMG) on the International Space Station (ISS) using a common sense approach (the agile development method) for concurrent mathematical modeling and simulation of the CMG subsystem. This simulation is part of Training systems for the 21st Century simulator which will provide training for crew members, instructors, and flight controllers. The basic idea of how the CMGs on the space station are used for its non-propulsive attitude control is briefly explained to set up the context for simulating a CMG subsystem. Next different reference frames and the detailed equations of motion (EOM) for multiple double-gimbal variable-speed control moment gyroscopes (DGVs) are presented. Fixing some of the terms in the EOM becomes the special case EOM for ISS's double-gimbaled fixed speed CMGs. CMG simulation development using the agile development method is presented in which customer's requirements and solutions evolve through iterative analysis, design, coding, unit testing and acceptance testing. At the end of the iteration a set of features implemented in that iteration are demonstrated to the flight controllers thus creating a short feedback loop and helping in creating adaptive development cycles. The unified modeling language (UML) tool is used in illustrating the user stories, class designs and sequence diagrams. This incremental development approach of mathematical modeling and simulating the CMG subsystem involved the development team and the customer early on, thus improving the quality of the working CMG system in each iteration and helping the team to accurately predict the cost, schedule and delivery of the software.

Inampudi, Ravi↗
NASA NTRS2016

Stewardship of NASA's Earth Science Data and Ensuring Long-Term Active Archives

Program, NASA has followed an open data policy, with non-discriminatory access to data with no period of exclusive access. NASA has well-established processes for assigning and or accepting datasets into one of 12 Distributed Active Archive Centers (DAACs) that are parts of EOSDIS. EOSDIS has been evolving through several information technology cycles, adapting to hardware and software changes in the commercial sector. NASA is responsible for maintaining Earth science data as long as users are interested in using them for research and applications, which is well beyond the life of the data gathering missions. For science data to remain useful over long periods of time, steps must be taken to preserve: (1) Data bits with no corruption, (2) Discoverability and access, (3) Readability, (4) Understandability, (5) Usability' and (6). Reproducibility of results. NASAs Earth Science data and Information System (ESDIS) Project, along with the 12 EOSDIS Distributed Active Archive Centers (DAACs), has made significant progress in each of these areas over the last decade, and continues to evolve its active archive capabilities. Particular attention is being paid in recent years to ensure that the datasets are published in an easily accessible and citable manner through a unified metadata model, a common metadata repository (CMR), a coherent view through the earthdata.gov website, and assignment of Digital Object Identifiers (DOI) with well-designed landing product information pages.

Data Management↗
NASA NTRS1989

A comparison of communication modes for delivery of air traffic control clearance amendments in transport category aircraft

A user centered evaluation is performed on the use of flight deck automation for display and control of aircraft horizontal flight path. A survey was distributed to pilots with a wide range of experience with the use of flight management computers in transport category aircraft to determine the acceptability and use patterns as reflected by the need for information displayed on the electronic horizontal situation indicator. A summary of survey results and planned part-task simulation to compare three communication modes (verbal, alphanumeric, graphic) are presented.

Chandra, D.↗
NASA NTRS1996

Sea WiFS Technical Report Series: The fourth SeaWIFS Intercalibration Round-Robin Experiment (SIRREX-4), May 1995

This report documents the fourth Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Intercalibration Round-Robin Experiment (SIRREX-4), which was held at the National Institute of Standards and Technology (NIST) on 3-10 May 1995. The agenda for SIRREX-4 was established by a consensus reached at the conclusion of SIRREX-3: there should be an emphasis on training and work to foster and encourage uniform use of accepted protocols for calibrating radiometric instruments in the laboratory. The goal was to host the activity in a setting where proper techniques could be discussed and demonstrated. It seemed appealing to split the day between morning lectures and afternoon laboratory exercises or practicals. The former gave the user community a chance to present what was important to them and discuss it with acknowledged experts in radiometry, while the latter presented a unique opportunity for training and evaluation in the presence of these same experts. The five laboratory sessions were concerned with (1) determining the responsivity of a spectroradiometer and the spectral radiance of an unknown integrating sphere source, (2) demonstrating spectral field calibration procedures for an integrating sphere using three different instruments, (3) measuring spectral radiance using the plaque method, (4) setting up and aligning lamp calibration transfer standards using the NIST specifications for irradiance measurements, and (5) characterizing radiometric instruments. In addition to documenting some supplemental studies performed outside the laboratory sessions, this report includes an evaluation of the hardware that has been used during the SIRREX activities plus a critical evaluation of SIRREX objectives.

Johnson, B. Carol↗
NASA NTRS1988

Integrated resource scheduling in a distributed scheduling environment

The Space Station era presents a highly-complex multi-mission planning and scheduling environment exercised over a highly distributed system. In order to automate the scheduling process, customers require a mechanism for communicating their scheduling requirements to NASA. A request language that a remotely-located customer can use to specify his scheduling requirements to a NASA scheduler, thus automating the customer-scheduler interface, is described. This notation, Flexible Envelope-Request Notation (FERN), allows the user to completely specify his scheduling requirements such as resource usage, temporal constraints, and scheduling preferences and options. The FERN also contains mechanisms for representing schedule and resource availability information, which are used in the inter-scheduler inconsistency resolution process. Additionally, a scheduler is described that can accept these requests, process them, generate schedules, and return schedule and resource availability information to the requester. The Request-Oriented Scheduling Engine (ROSE) was designed to function either as an independent scheduler or as a scheduling element in a network of schedulers. When used in a network of schedulers, each ROSE communicates schedule and resource usage information to other schedulers via the FERN notation, enabling inconsistencies to be resolved between schedulers. Individual ROSE schedules are created by viewing the problem as a constraint satisfaction problem with a heuristically guided search strategy.

Zoch, David↗