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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

[NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 4:] Technical communications in aerospace: An analysis of the practices reported by US and European aerospace engineers and scientists

Two pilot studies were conducted that investigated the technical communications practices of U.S. and European aerospace engineers and scientists. Both studies had the same five objectives: (1) solicit opinions regarding the importance of technical communications; (2) determine the use and production of technical communications; (3) seek views about the appropriate content of an undergraduate course in technical communications; (4) determine use of libraries, information centers, and online database; (5) determine use and importance of computer and information technology to them. A self-administered questionnaire was mailed to randomly selected aerospace engineers and scientists, with a slightly modified version sent to European colleagues. Their responses to selected questions are presented in this paper.

Pinelli, Thomas E.↗
NASA NTRS1991

Towards practical control design using neural computation

The objective is to develop neural network based control design techniques which address the issue of performance/control effort tradeoff. Additionally, the control design needs to address the important issue if achieving adequate performance in the presence of actuator nonlinearities such as position and rate limits. These issues are discussed using the example of aircraft flight control. Given a set of pilot input commands, a feedforward net is trained to control the vehicle within the constraints imposed by the actuators. This is achieved by minimizing an objective function which is the sum of the tracking errors, control input rates and control input deflections. A tradeoff between tracking performance and control smoothness is obtained by varying, adaptively, the weights of the objective function. The neurocontroller performance is evaluated in the presence of actuator dynamics using a simulation of the vehicle. Appropriate selection of the different weights in the objective function resulted in the good tracking of the pilot commands and smooth neurocontrol. An extension of the neurocontroller design approach is proposed to enhance its practicality.

Troudet, Terry↗
NASA NTRS1991

An architectural approach to create self organizing control systems for practical autonomous robots

For practical industrial applications, the development of trainable robots is an important and immediate objective. Therefore, the developing of flexible intelligence directly applicable to training is emphasized. It is generally agreed upon by the AI community that the fusion of expert systems, neural networks, and conventionally programmed modules (e.g., a trajectory generator) is promising in the quest for autonomous robotic intelligence. Autonomous robot development is hindered by integration and architectural problems. Some obstacles towards the construction of more general robot control systems are as follows: (1) Growth problem; (2) Software generation; (3) Interaction with environment; (4) Reliability; and (5) Resource limitation. Neural networks can be successfully applied to some of these problems. However, current implementations of neural networks are hampered by the resource limitation problem and must be trained extensively to produce computationally accurate output. A generalization of conventional neural nets is proposed, and an architecture is offered in an attempt to address the above problems.

Greiner, Helen↗
NASA NTRS1992

Professor Jesse W. Beams and the first practical magnetic suspension

Dr. Jesse W. Beams developed the first practical magnetic suspension for high speed rotating devices. The devices included high speed rotating mirrors, ultracentrifuges, and high speed centrifugal field rotors. A brief biography of Dr. Beams is presented, and the following topics are discussed: (1) early axial magnetic suspension for ultracentrifuges; and (2) magnetic suspension for high centrifugal fields.

Allaire, P. E.↗
NASA NTRS1991

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 13: The information-seeking habits and practices of engineers

It is argued that only by maximizing the research and development process can the United States maintain and possibly capture its international competitive edge. Key to this goal is the provision of information services and products which meet the information needs of engineers. Evidence exists which indicates that traditional information services and products may, in fact, not be meeting the information needs of engineers. The primary reason for this deficiency is three fold. First, the specific information needs of engineers are neither well known nor well understood. Second, what is known about the information seeking habits and practices of engineers has not been applied to existing engineering information services. Third, the information professionals continue to over-emphasize technology instead of concentrating on the quality of the information itself and the ability of the information to meet the needs of the user.

Pinelli, Thomas E.↗
NASA NTRS1991

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 14: An analysis of the technical communications practices reported by Israeli and US aerospace engineers and scientists

As part of Phase 4 of the NASA/DoD Aerospace Knowledge Diffusion Research Project, two pilot studies were conducted that investigated the technical communications practices of Israeli and U.S. aerospace engineers and scientists. Both studies had the same five objectives: first, to solicit the opinions of aerospace engineers and scientists regarding the importance of technical communications to their profession; second, to determine the use and production of technical communications by aerospace engineers and scientists; third, to seek their view about the appropriate content of an undergraduate course in technical communications; fourth, to determine aerospace engineers' and scientists' use of libraries, technical information centers, and on-line databases; and fifth, to determine the use and importance of computer and information technology to them. A self-administered questionnaire was mailed to randomly selected U.S. aerospace engineers and scientists who are working in cryogenics, adaptive walls, and magnetic suspension. A slightly modified version was sent to Israeli aerospace engineers and scientists working at Israel Aircraft Industries, LTD. Responses of the Israeli and U.S. aerospace engineers and scientists to selected questions are presented in this paper.

Barclay, Rebecca O.↗
NASA NTRS1992

Practical considerations in designing the engine cycle

When it is required to define the cycle parameters and calculate the performance of a real engine, there are numerous practical constraints that need to be taken into account. These fall into two main categories: the limitations of available component technologies, and the operational considerations that are dependent on aircraft application. The lecture discusses the main technology limiters and indicates how they are incorporated into the cycle definition process. Operational factors include the extent of the intended flight envelope and range of critical flight conditions for which performance must be assured, and the balance to be struck between minimising fuel consumption, maximising installed power and constraining costs of ownership. Taking these technology and operational influences into account, the basic cycle characteristics and approach to cycle choice are examined for three main classes of aircraft: subsonic transports, military combat aircraft and helicopters.

M G Philpot↗
NASA NTRS1991

Acquisition and improvement of human motor skills: Learning through observation and practice

Skilled movement is an integral part of the human existence. A better understanding of motor skills and their development is a prerequisite to the construction of truly flexible intelligent agents. We present MAEANDER, a computational model of human motor behavior, that uniformly addresses both the acquisition of skills through observation and the improvement of skills through practice. MAEANDER consists of a sensory-effector interface, a memory of movements, and a set of performance and learning mechanisms that let it recognize and generate motor skills. The system initially acquires such skills by observing movements performed by another agent and constructing a concept hierarchy. Given a stored motor skill in memory, MAEANDER will cause an effector to behave appropriately. All learning involves changing the hierarchical memory of skill concepts to more closely correspond to either observed experience or to desired behaviors. We evaluated MAEANDER empirically with respect to how well it acquires and improves both artificial movement types and handwritten script letters from the alphabet. We also evaluate MAEANDER as a psychological model by comparing its behavior to robust phenomena in humans and by considering the richness of the predictions it makes.

Iba, Wayne↗
NASA NTRS1992

Practical design optimization of wing/body configurations using the Euler equations

The development of a practical method for the aerodynamic design of isolated wing and wing/body configurations is achieved through the coupling of existing computational fluid dynamics (CFD) analysis codes and a quasi-Newton numerical optimization method. The direct design method is generalized to treat three-dimensional aerodynamic optimization problems subject to inviscid, rotational, compressible flow conditions imposed by the Euler equations. The method couples either the FLO57 or the TEAM flow solver with a modified version of the QNMDIF numerical optimization algorithm. The method is applied, but is not limited, to supersonic design problems. A case study is presented illustrating the method's effectiveness in maximizing the lift-to-drag ratio, subject to a variety of constraints, of selected supersonic configurations at cruise conditions.

Reuther, J.↗
NASA NTRS1993

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 16: A comparison of the technical communications practices of Russian and US aerospace engineers and scientists

As part of Phase 4 of the NASA/DOD Aerospace Knowledge Diffusion Project, two studies were conducted that investigated the technical communications practices of Russian and U.S. aerospace engineers and scientists. Both studies have the same five objectives: first, to solicit the opinions of aerospace engineers and scientists regarding the importance of technical communications to their profession; second, to determine the use and production of technical communications by aerospace engineers and scientists; third, to seek their views about the appropriate content of an undergraduate course in technical communications; fourth, to determine aerospace engineers' and scientists' use of libraries, technical information centers, and on-line data bases; and fifth, to determine the use and importance of computer and information technology to them. A self-administered questionnaire was distributed to aerospace engineers and scientists at the Central Aero-Hydrodynamic Institute (TsAGI), NASA ARC, and NASA LaRC. The completion rates for the Russian and U.S. surveys were 64 and 61 percent, respectively. The responses of the Russian and U.S. participants, to selected questions, are presented in this report.

Thomas E Pinelli↗
NASA NTRS1993

Practical aspects of transfer from GTO to lunar orbit

This paper is a presentation of some practical aspects of orbital transfer from Geosynchronous Transfer Orbit (GTO) to close, near-circular orbits of the Moon. The intent is to identify the important parameters affecting the problem and to bound (approximately) the range of required delta V for a spacecraft that has been placed in GTO. The basic geometric relationships are described and the dynamics are simulated by use of the Zero-Sphere-of Influence Patched Conic method. It is found that the inclination of the transfer orbit to the Earth-Moon plane is relatively unimportant while the position of the line of apsides with respect to the Moon's orbit is the main geometric parameter of interest. It is shown that this parameter can be controlled by selecting the time of day for launch and that two launch windows of approximately 45 minutes duration are available each day of the year if use is made of the recommended phasing orbit transfer. The phasing orbit transfer not only provides twice-daily launch windows, but also provides a mechanism for efficacious correction of GTO injection errors. Delta V penalties for out-of-plane transfer and for late launch are evaluated and the method is recommended for use as an affordable means of achieving lunar orbit.

Uphoff, Chauncey↗
NASA NTRS1993

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 28: The technical communication practices of Russian and US aerospace engineers and scientists

As part of Phase 4 of the NASA/DoD Aerospace Knowledge Diffusion Research Project, two studies were conducted that investigated the technical communication practices of Russian and U.S. aerospace engineers and scientists. Both studies had the same five objectives: first, to solicit the opinions of aerospace engineers and scientists regarding the importance of technical communication to their professions; second, to determine the use and production of technical communication by aerospace engineers and scientists; third, to seek their views about the appropriate content of the undergraduate course in technical communication; fourth, to determine aerospace engineers' and scientists' use of libraries, technical information centers, and on-line databases; and fifth, to determine the use and importance of computer and information technology to them. A self administered questionnaire was distributed to Russian aerospace engineers and scientists at the Central Aero-Hydrodynamic Institute (TsAGI) and to their U.S. counterparts at the NASA Ames Research Center and the NASA Langley Research Center. The completion rates for the Russian and U.S. surveys were 64 and 61 percent, respectively. Responses of the Russian and U.S. participants to selected questions are presented in this paper.

Pinelli, Thomas E.↗
NASA NTRS1993

Design of coupled mace filters for optical pattern recognition using practical spatial light modulators

Spatial light modulators (SLMs) are being used in correlation-based optical pattern recognition systems to implement the Fourier domain filters. Currently available SLMs have certain limitations with respect to the realizability of these filters. Therefore, it is necessary to incorporate the SLM constraints in the design of the filters. The design of a SLM-constrained minimum average correlation energy (SLM-MACE) filter using the simulated annealing-based optimization technique was investigated. The SLM-MACE filter was synthesized for three different types of constraints. The performance of the filter was evaluated in terms of its recognition (discrimination) capabilities using computer simulations. The correlation plane characteristics of the SLM-MACE filter were found to be reasonably good. The SLM-MACE filter yielded far better results than the analytical MACE filter implemented on practical SLMs using the constrained magnitude technique. Further, the filter performance was evaluated in the presence of noise in the input test images. This work demonstrated the need to include the SLM constraints in the filter design. Finally, a method is suggested to reduce the computation time required for the synthesis of the SLM-MACE filter.

Rajan, P. K.↗
NASA NTRS1992

The Effects of Use of Civil Airworthiness Criteria on U.S. Air Force Acquisition, Test and Evaluation Practices

In response to the initiatives to streamline, not to mention comply with the Public Law for Non-Developmental Item Preference, the Department of Defense (DOD) has increased its use of commercial products. The Air Force has, over the past 15 years, been adapting Federal Aviation Administration (FAA) certified aircraft to perform many of its airlift and training missions. Counting the T-1A Jayhawk Trainer (Beechjet 400), in excess of 500 total aircraft, covering 15 different types, will have been procured since 1978. Needless to say, significant reform of the "classical" DOD and Air Force way of doing business has been necessary. Major strides have been made by the Transport Directorate of the Aircraft Program Office in the area of test and evaluation, with integrated qualification and operational testing (QT &E/QOT &E) and airworthiness certification testing by the FAA. As well, significant changes in contracting practices and the use of commercial (vice military) specifications for qualification criteria have been realized. This paper will relate some of these significant strides in "commercializing" and streamlining the DOD acquisition and test and evaluation processes. Additionally, it will review both regulatory changes made and recommended. It concludes with a compilation of lessons learned and recommendations for further streamlining of the DOD processes.

Flight Testing↗
NASA NTRS1992

Practical computation of the mixed mu problem

The computational aspects of the recently developed upper and lower bounds for the mixed mu problem are examined. In particular, a practical algorithm is developed to compute the bounds. This has been implemented as a Matlab function (m-file) and will be available in a test version in conjunction with the mu-Tools toolbox. The algorithm performance is very encouraging, in terms of both accuracy of the resulting bounds and growth rate in required computation with problem size. In particular, it appears that one can handle medium-size problems (less than 100 perturbations) with reasonable computational requirements.

Young, Peter M.↗
NASA NTRS1993

The technical communication practices of Russian and U.S. aerospace engineers and scientists

As part of Phase 4 of the NASA/DoD Aerospace Knowledge Diffusion Research Project, two studies were conducted that investigated the technical communication practices of Russian and U.S. aerospace engineers and scientists. Both studies had the same five objectives: first, to solicit the opinions of aerospace engineers and scientists regarding the importance of technical communication to their professions; second, to determine the use and production of technical communication by aerospace engineers and scientists; third, to seek their views about the appropriate content of the undergraduate course in technical communication; fourth, to determine aerospace engineers' and scientists' use of libraries, technical information centers, and on-line databases; and fifth, to determine the use and importance of computer and information technology to them. A self administered questionnaire was distributed to Russian aerospace engineers and scientists at the Central Aero-Hydrodynamic Institute (TsAGI) and to their U.S. counterparts at the NASA Ames Research Center and the NASA Langley Research Center. The completion rates for the Russian and U.S. surveys were 64 and 61 percent, respectively. Responses of the Russian and U.S. participants to selected questions are presented in this paper.

Pinelli, Thomas E.↗
NASA NTRS1993

Emission characteristics of a model gas turbine combustor at practical conditions

This paper reports on in situ and exit plane emissions measurements from a model gas turbine combustor at practical air preheat temperatures and pressures for a range of operating conditions. The model combustor chosen for the study features two rows of jets (primary and dilution) with four jets per row, and utilizes effusive air cooling holes on the liner wall. The combustor dome is equipped with a flat-vaned swirler with a vane angle of 60 deg. Data are obtained at combustor pressures ranging from 2 to 10 atmospheres, air preheat temperatures from 204 C to 427 C, and combustor reference velocities from 10.0 to 20.0 m/s. An overall equivalence ratio of 0.3 was constant for all conditions. Exit plane and in situ measurements are presented for HC, O2, CO2, CO, and NO(x). The results from exit plane NO(x) measurements illustrate that the model combustor is representative of current gas turbine combustors. The in situ data reveal effects of fuel/air and wall jet mixing on emission performance.

Drennan, S. A.↗