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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 1,621 records · Page 90
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Technology transfer to a developing nation, Korea

An experimental project is reported which was undertaken. to determine if selected types of technology developed for the aerospace program during the past decade are relevant to specific industrial problems of a developing nation and to test whether a structured program could facilitate the transfer of relevant technologies. The Korea Institute of Science and Technology and the IIT Research Institute were selected as the active transfer agents to participate in the program. The pilot project was based upon the approach to the transfer of domestic technology developed by the NASA Technology Utilization Division and utilized the extensive data and technical resources available through the Space Agency and its contractors. This pilot project has helped to clarify some aspects of the international technology transfer process and to upgrade Korean technological capabilities.

Stone, C. A.↗
NASA NTRS1972

A curve fitting method for solving the flutter equation

A curve fitting approach was developed to solve the flutter equation for the critical flutter velocity. The psi versus nu curves are approximated by cubic and quadratic equations. The curve fitting technique utilized the first and second derivatives of psi with respect to nu. The method was tested for two structures, one structure being six times the total mass of the other structure. The algorithm never showed any tendency to diverge from the solution. The average time for the computation of a flutter velocity was 3.91 seconds on an IBM Model 50 computer for an accuracy of five per cent. For values of nu close to the critical root of the flutter equation the algorithm converged on the first attempt. The maximum number of iterations for convergence to the critical flutter velocity was five with an assumed value of nu relatively distant from the actual crossover.

Cooper, J. L.↗
NASA NTRS1975

Evaluation of boron/aluminum tubes in compression

A brief analytical and experimental investigation was conducted to determine the compressive behavior of a limited number of boron/aluminum (B/Al) tubes. The purpose of the investigation was to gain hardware experience in a limited evaluation of the material for possible application to spacecraft truss structures. Specimen description, test procedures and results are presented as well as comparisons with theoretical predictions regarding local column stability. It is shown that the experimental results of full-scale tests are consistent with previously reported data and that the local stability of B/Al columns as determined through short column tests can best be predicted using large deflection theory.

Knoell, A. C.↗
NASA NTRS1977

Quiet, Clean, Short-Haul Experimental Engines /QCSEE/ - A technology development program

NASA's QCSEE Program (Quiet, Clean, Short-Haul Experimental Engine) performed by the General Electric Company covers a wide range of advanced propulsion technology features applicable to future subsonic engine concepts. These technology features are combined into two engine and nacelle configurations for demonstration of program goals. This paper presents descriptions of two engine/nacelle configurations and shows the flow of technology developed in component programs into the configurations. The under-the-wing (UTW) configuration, featuring major innovative and advanced components, such as a large variable pitch fan and a composite material integrated engine and nacelle structure, has been tested at General Electric's Peebles, Ohio test facility. The key characteristics of the engine as observed from the initial test series are presented.

Willis, W. S.↗
NASA NTRS1977

Development of a low expansion, composite antenna subreflector with a frequency selective surface

A Kevlar-49 epoxy, composite frequency-selective-surface subreflector was developed for the high gain antenna used on the Voyager spacecraft. The Kevlar-49 material was selected for this sandwich structure because a dielectric material was required, and the use of Kevlar-49 resulted in a composite sandwich with a low thermal coefficient of expansion and reduced weight over an equivalent fiberglass construction. A detailed description and the results of the development program are given and include the design requirements for the structure, the development testing of the materials that led to the final design configuration, and the processes used to fabricate this advanced composite spacecraft antenna component.

Stonier, R. A.↗
NASA NTRS1980

JPL self pulsed laser surface measurement system development

The use of a self pulsed laser system for accurately describing the surface shape of large space deployed antenna structures was evaluated. Tests with a breadboard system verified functional operation with short time resolution on the order of .2 mm, nonambiguous ranging, and a maximum range capability on the order of 150 m. The projected capability of the system is resolution of less than .1 mm over a reasonable time period and a range extension to over 300 m.

Berdahl, M.↗
NASA NTRS1980

Cost reduction in space operations - Structuring a planetary program to minimize the annual funding requirement as opposed to minimizing the program runout cost

An approach is proposed for the structuring of a planetary mission set wherein the peak annual funding is minimized to meet the annual budget restraint. One aspect of the approach is to have a transportation capability that can launch a mission in any planetary opportunity; such capability can be provided by solar electric propulsion. Another cost reduction technique is to structure a mission test in a time sequenced fashion that could utilize essentially the same spacecraft for the implementation of several missions. A third technique would be to fulfill a scientific objective in several sequential missions rather than attempt to accomplish all of the objectives with one mission. The application of the approach is illustrated by an example involving the Solar Orbiter Dual Probe mission.

Herman, D. H.↗
NASA NTRS1980

Crop identification studies using Landsat data Separation of barley from other spring small grains and corn and soybean decision logic

Two labeling procedures were developed which identify various agricultural crops through the use of Landsat data. One procedure separates barley from other spring small grains, and the other identifies corn and soybeans. For both procedures, a minimum data set (critical acquisition time) has been designated. Landsat data in both image format and various graphic displays were used along with ancillary data to obtain information which aided in labeling the spectral signatures. The corn and soybean procedure also employed a structured decision logic. Test results for the barley separation procedure emphasized the importance of obtaining a critical acquisition and showed some success especially in areas where spring crops followed the expected growth patterns. Two tests of the corn and soybean procedure produced good labeling accuracies. Problems with the procedure were easy to identify, and some solutions were implemented for the second test. Automation of various parts of the procedure and extension to other crops and regions were recommended.

Dailey, C. L.↗
NASA NTRS1979

Airborne Electronically Steerable Phased Array (AESPA) program

The basic concept and design of a flatplate-fed transmission array are described and system performance requirements are summarized. Particular emphasis is given to the design of the aperture, the radiating element, the phase shifter, the flatplate feed, and the mechanical support structure. Fabrication and testing techniques are considered. Of the three major parameters of interest in demonstrating the performance capabilities of the transmissive array, beamwidth was shown to be the least sensitive to system amplitude and phase errors. Beam pointing angle was also shown to be relatively insensitive to errors. Close agreement between measured and calculated values was found for array gain. The greatest difference was found for array sidelone level.

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NASA NTRS1980

The design of low cost structures for extensive ground arrays

The development of conceptual designs of solar array support structures and their foundations including considerations of the use of concrete, steel, aluminum, or timber are reported. Some cost trends were examined by varying selected parameters to determine optimum configurations. Detailed civil/structural design criteria were developed. Using these criteria, eight detailed designs for support structures and foundations were developed and cost estimates were made. As a result of the study wind was identified as the major loading experienced by these low height structures, whose arrays are likely to extend over large tracts of land. Proper wind load estimating is considered essential to developing realistic structural designs and achieving minimum cost support structures. Wind tunnel testing of a conceptual array field was undertaken and some of the resulting wind design criteria are presented. The SPS rectenna system designs may be less sensitive to wind load estimates, but consistent design criteria remain important.

Franklin, H. A.↗
NASA NTRS1984

Repair techniques for celion/LARC-160 graphite/polyimide composite structures

The large stiffness-to-weight and strength-to-weight ratios of graphite composite in combination with the 600 F structural capability of the polyimide matrix can reduce the total structure/TPS weight of reusable space vehicles by 20-30 percent. It is inevitable that with planned usage of GR/PI structural components, damage will occur either in the form of intrinsic flaw growth or mechanical damage. Research and development programs were initiated to develop repair processes and techniques specific to Celion/LARC-160 GR/PI structure with emphasis on highly loaded and lightly loaded compression critical structures for factory type repair. Repair processes include cocure and secondary bonding techniques applied under vacuum plus positive autoclave pressure. Viable repair designs and processes are discussed for flat laminates, honeycomb sandwich panels, and hat-stiffened skin-stringer panels. The repair methodology was verified through structural element compression tests at room temperature and 315 C (600 F).

Jones, J. S.↗
NASA NTRS1984

Aerospace engineering design by systematic decomposition and multilevel optimization

A method for systematic analysis and optimization of large engineering systems, by decomposition of a large task into a set of smaller subtasks that is solved concurrently is described. The subtasks may be arranged in hierarchical levels. Analyses are carried out in each subtask using inputs received from other subtasks, and are followed by optimizations carried out from the bottom up. Each optimization at the lower levels is augmented by analysis of its sensitivity to the inputs received from other subtasks to account for the couplings among the subtasks in a formal manner. The analysis and optimization operations alternate iteratively until they converge to a system design whose performance is maximized with all constraints satisfied. The method, which is still under development, is tentatively validated by test cases in structural applications and an aircraft configuration optimization.

Sobieszczanski-Sobieski, J.↗
NASA NTRS1983

Application of stiffened cylinder analysis to ATP interior noise studies

An analytical model developed to predict the interior noise of propeller driven aircraft was applied to experimental configurations for a Fairchild Swearingen Metro II fuselage exposed to simulated propeller excitation. The floor structure of the test fuselage was of unusual construction - mounted on air springs. As a consequence, the analytical model was extended to include a floor treatment transmission coefficient which could be used to describe vibration attenuation through the mounts. Good agreement was obtained between measured and predicted noise reductions when the foor treatment transmission loss was about 20 dB - a value which is consistent with the vibration attenuation provided by the mounts. The analytical model was also adapted to allow the prediction of noise reductions associated with boundary layer excitation as well as propeller and reverberant noise.

Wilby, E. G.↗
NASA NTRS1984

Aerospace engineering design by systematic decomposition and multilevel optimization

This paper describes a method for systematic analysis and optimization of large engineering systems, e.g., aircraft, by decomposition of a large task into a set of smaller, self-contained subtasks that can be solved concurrently. The subtasks may be arranged in many hierarchical levels with the assembled system at the top level. Analyses are carried out in each subtask using inputs received from other subtasks, and are followed by optimizations carried out from the bottom up. Each optimization at the lower levels is augmented by analysis of its sensitivity to the inputs received from other subtasks to account for the couplings among the subtasks in a formal manner. The analysis and optimization operations alternate iteratively until they converge to a system design whose performance is maximized with all constraints satisfied. The method, which is still under development, is tentatively validated by test cases in structural applications and an aircraft configuration optimization. It is pointed out that the method is intended to be compatible with the typical engineering organization and the modern technology of distributed computing.

Sobieszczanski-Sobieski, J.↗
NASA NTRS1985

Guide to using lunar soil and simulants for experimentation

It is pointed out that lunar soil can be described as well-graded silty sands or sandy silts with an average particle size by weight in the range from 0.040 to 0.130 mm. The density of in situ bulk lunar soil is typically 1.4 to 1.9 g/cu cm. Changes in soil from moon to laboratory are considered along with some critical differences between simulants and lunar soil. Attention is given to agglutinates, iron metal distributed throughout the agglutinatic glass, solar wind hydrogen, and major lunar minerals (anorthite, pyroxene, ilmenite, olivine). The use of lunar fines as experimental samples is discussed, and the characteristics of simulants for experiments are examined, taking into account grain size distribution, particle type distribution, a highlands simulant, and a high titanium mare simulant. Simulants for testing equipment and structures are also described.

Allton, J. H.↗
NASA NTRS1986

X-29A advanced technology demonstrator program overview

The present discussion of the X-29A forward-swept wing experimental aircraft's functional flight program and concept evaluation program gives attention to the program management structure for a test team that encompasses NASA, the U.S. Air Force, and the prime contractor for the X-29A. The preflight, flight-functional, envelope-expansion and flight research test objectives of the program are also noted, together with the qualitative characterizations obtained to date for both a limited envelope flight control system and one for an expanded envelope.

Sefic, W. J.↗
NASA NTRS1986

The 15 meter hoop-column antenna dynamics: Test and analysis

A 15 meter model of the hoop-column antenna concept has been vibration tested for model characterization and analytical model verification. Linear finite element analysis predicted the global vibration frequencies accurately. Good agreement between analysis and test data was obtained only after the analytical model was refined using static test data. As structures become more flexible, structural properties determined from static data become more accurate and should be used to update analytical models. Global vibration modes are not significantly affected by the surface mesh which permits simplified analytical models to be used for prediction of global behavior. These reduced models are believed sufficient for preliminary design and controls simulations where only global behavior is desired. The mesh modes were highly damped due to the knit mesh used for the reflector surface. These modes were also highly coupled and very difficult to measure in the laboratory. The inability to fully characterize the antenna mesh modes in the laboratory indicates robust methods for active surface vibration suppression will be needed. Fortunately, the surface mesh exhibits high passive damping which should be beneficial to active control systems.

Belvin, W. Keith↗
NASA NTRS1985

Collected software engineering papers, volume 3

Topics addressed include: software technology evaluation programs; collection of valid software engineering data; test processes using structural coverage; prototype expert system for software engineering management; use of an environment characteristic software metric set; software modulation; software development by analysis of change; and independent verification and validation.

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