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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Knowledge acquisition from natural language for expert systems based on classification problem-solving methods

It is shown how certain kinds of domain independent expert systems based on classification problem-solving methods can be constructed directly from natural language descriptions by a human expert. The expert knowledge is not translated into production rules. Rather, it is mapped into conceptual structures which are integrated into long-term memory (LTM). The resulting system is one in which problem-solving, retrieval and memory organization are integrated processes. In other words, the same algorithm and knowledge representation structures are shared by these processes. As a result of this, the system can answer questions, solve problems or reorganize LTM.

Gomez, Fernando↗
NASA NTRS1990

Multistep matrix integrators for real-time simulation

An explicit linear multistep matrix-integration technique is presented for vector systems of ODEs which employs the stability region placement approach to permit the time-step to be chosen independently of system eigenvalues. Closed-form solutions for the general p-step method and the case where the system matrix has zero eigenvalues are given. It is shown that system mode shapes are preserved over the integration process, and that the technique remains applicable to systems with eigenvalues at their origin without need for computing a matrix inversion.

De Abreu-Garcia, J. A.↗
NASA NTRS1991

Description of the PMAD DC test bed architecture and integration sequence

NASA-Lewis is responsible for the development, fabrication, and assembly of the electric power system (EPS) for the Space Station Freedom (SSF). The SSF power system is radically different from previous spacecraft power systems in both the size and complexity of the system. Unlike past spacecraft power system the SSF EPS will grow and be maintained on orbit and must be flexible to meet changing user power needs. The SSF power system is also unique in comparison with terrestrial power systems because it is dominated by power electronic converters which regulate and control the power. Although spacecraft historically have used power converters for regulation they typically involved only a single series regulating element. The SSF EPS involves multiple regulating elements, two or more in series, prior to the load. These unique system features required the construction of a testbed which would allow the development of spacecraft power system technology. A description is provided of the Power Management and Distribution (PMAD) DC Testbed which was assembled to support the design and early evaluation of the SSF EPS. A description of the integration process used in the assembly sequence is also given along with a description of the support facility.

Beach, R. F.↗
NASA NTRS1991

YUCSA: A CLIPS expert database system to monitor academic performance

The York University CLIPS Student Administrator (YUCSA), an expert database system implemented in C Language Integrated Processing System (CLIPS), for monitoring the academic performance of undergraduate students at York University, is discussed. The expert system component in the system has already been implemented for two major departments, and it is under testing and enhancement for more departments. Also, more elaborate user interfaces are under development. We describe the design and implementation of the system, problems encountered, and immediate future plans. The system has excellent maintainability and it is very efficient, taking less than one minute to complete an assessment of one student.

Toptsis, Anestis A.↗
NASA NTRS1992

A co-designed equalization, modulation, and coding scheme

The commercial impact and technical success of Trellis Coded Modulation seems to illustrate that, if Shannon's capacity is going to be neared, the modulation and coding of an analogue signal ought to be viewed as an integrated process. More recent work has focused on going beyond the gains obtained for Average White Gaussian Noise and has tried to combine the coding/modulation with adaptive equalization. The motive is to gain similar advances on less perfect or idealized channels.

Peile, Robert E.↗
NASA NTRS1991

Evolutionary development of a lunar CELSS

An evolutionary technology-integration process has been applied to a baseline, partially-closed regenerative life support system (LSS) based on Space Station Freedom-typified physicochemical (PC) technology; the result of this evolution is the Lunar-base Controlled Ecological LSS (LCELSS), which is a hybrid system incorporating both bioregenerative (BR) and PC technologies. The evolution of the LCELSS has proceeded through a sequence of additions involving (1) bioregenerative functions, (2) supplementing specific PC functions with BR ones, (3) replacement of initial PC technologies with more advanced ones, and (4) the addition of new PC technologies.

Schwartzkopf, Steven H.↗
NASA NTRS1991

Microgravity science experiment integration - When the PI and the PED differ

This paper addresses issues related to the integration of principal investigators (PIs) and payload-element developers (PEDs) for conducting effective microgravity experiments. The Crystal Growth Furnace (CGF) is used as an example to demonstrate the key issues related to the integration of a PI's sample into a facility run by a different organization. Attention is given to the typical preflight timeline, documentation required for experimental implementation, and hardware deliverables. A flow chart delineates the payload-integration process flow, and PI inputs required for an experiment include equipment and procedure definitions, detailed design and fabrication of the experiment-specific equipment, and specifications of the contract-end item. The present analysis is of interest to the coordination of effective microgravity experiments on the Space Station Freedom that incorporate PIs and PEDs from different organizations.

Baer-Peckham, M. S.↗
NASA NTRS1991

Description of the PMAD DC test bed architecture and integration sequence

NASA-LEWIS is responsible for the development, fabrication, and assembly of the electric power system (EPS) for the Space Station Freedom (SSF). The SSF power system is radically different from previous spacecraft power systems in both the size and complexity of the system. Unlike past spacecraft power systems, the SSF EPS will grow and be maintained on orbit and must be flexible to meet challenging user power needs. The SSF power system is also unique in comparison with terrestrial power systems because it is dominated by power electronic converters which regulate and control the power. A description is provided of the Power Management and Distribution DC Testbed which was assembled to support the design and early evaluation of the SSF EPS. A description of the integration process used in the assembly sequence is also given along with a description of the support facility.

Beach, R. F.↗
NASA NTRS1992

Strategic directions and mechanisms in technology transfer

An outline summarizing the Working Panel discussion related to strategic directions for technology transfer is presented. Specific topics addressed include measuring success, management of technology, innovation and experimentation in the tech transfer process, integration of tech transfer into R&D planning, institutionalization of tech transfer, and policy/legislative resources.

Mackin, Robert↗
NASA NTRS1993

A COMPACT model reduction methodology for articulated, multi-flexible bodies structures

To simulate the dynamical motion of articulated, multiflexible body structures, one can use multibody simulation packages such as DISCOS. To this end, one need appropriate reduced-order models for all the flexible components involved. The component modes projection and assembly model reduction methodology is one way to construct these reduced-order component models. However, the generated reduced-order system models typically contain high frequency extraneous modes. The presence of high frequency extraneous modes in a reduced-order system model forces us to use a small stepsize in the numerical integration of that model, resulting in an increase in the elapsed time of the integration process. To eliminate these high-frequency modes, we first identify and discard the component modes that 'contributed' to the generations of these modes. A sensitivity analysis is then used to determine how the remaining component modes should be perturbed in order to still closely capture the selected system modes. The effectiveness of the proposed methodology has been successfully verified using a finite-element model of the Galileo spacecraft.

Lee, Allan Y.↗
NASA NTRS1994

Muscular activity and its relationship to biomechanics and human performance

The purpose of this manuscript is to address the issue of muscular activity, human motion, fitness, and exercise. Human activity is reviewed from the historical perspective as well as from the basics of muscular contraction, nervous system controls, mechanics, and biomechanical considerations. In addition, attention has been given to some of the principles involved in developing muscular adaptations through strength development. Brief descriptions and findings from a few studies are included. These experiments were conducted in order to investigate muscular adaptation to various exercise regimens. Different theories of strength development were studied and correlated to daily human movements. All measurement tools used represent state of the art exercise equipment and movement analysis. The information presented here is only a small attempt to understand the effects of exercise and conditioning on Earth with the objective of leading to greater knowledge concerning human responses during spaceflight. What makes life from nonliving objects is movement which is generated and controlled by biochemical substances. In mammals. the controlled activators are skeletal muscles and this muscular action is an integral process composed of mechanical, chemical, and neurological processes resulting in voluntary and involuntary motions. The scope of this discussion is limited to voluntary motion.

Ariel, Gideon↗
NASA NTRS1993

Express Payload Project - A new method for rapid access to Space Station Freedom

The deployment and permanent operation of Space Station Freedom will enable researchers to enter a new era in the 21st century, in which continuous on-orbit experimentation and observation become routine. In support of this objective, the Space Station Freedom Program Office has initiated the Express Payload Project. The fundamental project goal is to reduce the marginal cost associated with small payload development, integration, and operation. This is to be accomplished by developing small payload accommodations hardware and a new streamlined small payload integration process. Standardization of small payload interfaces, certification of small payload containers, and increased payload developer responsibility for mission success are key aspects of the Express Payload Project. As the project progresses, the principles will be applied to both pressurized payloads flown inside the station laboratories and unpressurized payloads attached to the station external structures. The increased access to space afforded by Space Station Freedom and the Express Payload Project has the potential to significantly expand the scope, magnitude, and success of future research in the microgravity environment.

Uhran, Mark L.↗
NASA NTRS1994

Earth Observing System/Advanced Microwave Sounding Unit-A (EOS/AMSU-A): Software concept document

This document presents the concept for two separate but closely related software systems. The first is the special test equipment (STE) software used at Aerojet for AMSU-A instrument testing, and the second is the workstation software used at the spacecraft integration facility to monitor the AMSU-A instrument when installed on the spacecraft. The primary use of the STE software is to monitor the data output from the AMSU-A instruments, to command the instruments, and to perform automated thermal-vacuum calibration testing. The primary use of the workstation software is to monitor the AMSU-A instrument's performance through an Ethernet link during the instrument/spacecraft integration process.

Schwantje, Robert↗
NASA NTRS1994

Poly(arylene ether imidazole) surfacing films for flat and parabolic structures

Films of thermoplastic poly(arylene ether imidazole)s (PAEIs) are used as surface modifiers for neat resin panels and composite resin panels. The PAEI polymer contains imidazole groups along the backbone which co-cure, i.e., react chemically, with epoxies or bismaleimides during processing and thereby provide excellent adhesion between the PAEI film and an epoxy or bismaleimide neat resin or composite resin facesheet. The film provides good adhesion and a smooth surface to the finished part and acts as a release agent from the mold. The as-processed integral structures have very smooth (specular) surfaces, and since the film releases readily from a glass mold, no release agent is necessary. The PAEI film is thermally stable, resistant to electron radiation, and adheres tenaciously to the facesheet. The film maintains good adhesion even after thermal cycling from room temperature to approximately -196 C.

Connell, John W.↗
NASA NTRS1994

Breaking down barriers in cooperative fault management: Temporal and functional information displays

At the highest level, the fundamental question addressed by this research is how to aid human operators engaged in dynamic fault management. In dynamic fault management there is some underlying dynamic process (an engineered or physiological process referred to as the monitored process - MP) whose state changes over time and whose behavior must be monitored and controlled. In these types of applications (dynamic, real-time systems), a vast array of sensor data is available to provide information on the state of the MP. Faults disturb the MP and diagnosis must be performed in parallel with responses to maintain process integrity and to correct the underlying problem. These situations frequently involve time pressure, multiple interacting goals, high consequences of failure, and multiple interleaved tasks.

Potter, Scott S.↗
NASA NTRS1993

Atlas IIAS ascent trajectory design for the SOHO mission

In 1995, an Atlas IIAS launch vehicle will loft the Solar and Heliospheric Observatory (SOHO) as part of the International Solar and Terrestrial Physics program. The operational phase of the SOHO mission will be conducted from a `halo orbit' about the Sun-Earth interior libration point. Depending on the time of the year of launch, the optimal transfer requires a parking orbit of variable duration to satisfy widely varying inertial targets. A simulation capability has been developed that optimizes the launch vehicle ascent and spacecraft transfer phases of flight together, subject to both launch vehicle and spacecraft constraints. It will be shown that this `ground-up' simulation removes the need for an intermediate target vector at Centaur upper stage/spacecraft separation. Although providing only a modest gain in deliverable satellite mass, this capability substantially improves the mission integration process by removing the strict reliance on near-Earth target vectors. Trajectory data from several cases are presented and future applications of this capability are also discussed.

Willen, Robert E.↗
NASA NTRS1997

Landing Gear Integration in Aircraft Conceptual Design

The design of the landing gear is one of the more fundamental aspects of aircraft design. The design and integration process encompasses numerous engineering disciplines, e.g., structure, weights, runway design, and economics, and has become extremely sophisticated in the last few decades. Although the design process is well-documented, no attempt has been made until now in the development of a design methodology that can be used within an automated environment. As a result, the process remains to be a key responsibility for the configuration designer and is largely experience-based and graphically-oriented. However, as industry and government try to incorporate multidisciplinary design optimization (MDO) methods in the conceptual design phase, the need for a more systematic procedure has become apparent. The development of an MDO-capable design methodology as described in this work is focused on providing the conceptual designer with tools to help automate the disciplinary analyses, i.e., geometry, kinematics, flotation, and weight. Documented design procedures and analyses were examined to determine their applicability, and to ensure compliance with current practices and regulations. Using the latest information as obtained from industry during initial industry survey, the analyses were in terms modified and expanded to accommodate the design criteria associated with the advanced large subsonic transports. Algorithms were then developed based on the updated analysis procedures to be incorporated into existing MDO codes.

Chai, Sonny T.↗
NASA NTRS1999

Rendering Three-Dimensional Solar Coronal Structures of Active Region 8227

Coronal X-ray and EUV synthesized images are constructed of Active Region 8227 (May-June 1996) and are compared with Yohkoh/SXT, SOHO/EIT, and TRACE observations. Using the rendering technique of Gary (1997) and Alexander, Gary, and Thompson (1998), specific geometric and physical models are used to integrated the plasma emission along the line of sight to obtain a rendered image. The specific instrumental profiles are convolved in the integration process as well as specific heating functions. We analyze coronal X-ray and EUV structures by constructing synthesized image and comparison with observations provide test of specific physical models. We investigate how different pressure distributions within the active region loop system affect the emission characteristics and compare the various results with coronal observations. We investigate how the different heating functions in the active region are reflected in the effect of overall structure of the region. Specific heating rates are tested.

Gary, G. A.↗