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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 469 records · Page 26
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NASA NTRS1972

Automated design optimization of supersonic airplane wing structures under dynamic constraints

The problems of the preliminary and first level detail design of supersonic aircraft wings are stated as mathematical programs and solved using automated optimum design techniques. The problem is approached in two phases: the first is a simplified equivalent plate model in which the envelope, planform and structural parameters are varied to produce a design, the second is a finite element model with fixed configuration in which the material distribution is varied. Constraints include flutter, aeroelastically computed stresses and deflections, natural frequency and a variety of geometric limitations.

Fox, R. L.↗
NASA NTRS1973

The effect of noise constraints on engine cycle optimization for long-haul transports

Results are presented of NASA studies to determine optimum engine cycles for noise levels of 10, 15, and 20 EPNdb below current FAA regulations. The study aircraft were 200-passenger trijets flying over ranges of 5,556 and 10,200 km at cruise speeds of Mach 0.90 to 0.98. The economic impact of reducing noise, the identification of needed advanced technology and the effect of these advances are presented. The studies showed that the noise constraints imposed compromises on the optimum cycle with resulting economic penalties. The application of advanced engine technologies, however, could effectively offset these economic penalties.

Antl, R. J.↗
NASA NTRS1973

The effect of finite thrust and heating constraints on the synergetic plane change maneuver for a space shuttle orbiter-class vehicle

Numerical solutions to the optimal three-dimensional glide/thrust atmosphere skip maneuver are obtained using the multiple shooting iteration scheme. A singular thrust arc, induced by the heating constraints, is encountered. The synergetic plane change maneuver is shown to be superior to an extra-atmospheric one for 556-km (300-nm) circular orbit plane changes of more than 5 degrees.

Dickmanns, E. D.↗
NASA NTRS1972

Design of communication systems using short-constraint-length convolutional codes.

A method is presented for calculating the effect of carrier-phase reference error in a receiver phase-locked loop on bit error rates in convolutionally coded data, for the practical design of systems using short-constraint-length convolutional codes. A set of design curves shows the relation between design bit error rate, uplink carrier tracking loop SNR, downlink total SNR, and downlink modulation index. These curves make possible rapid and simple system optimization.

Merrill, H. M.↗
NASA NTRS1973

Observational constraints imposed by Brans-Dicke cosmologies.

Flat-space Brans-Dicke (BD) cosmologies previously found are analyzed in more detail. It is shown that the observed values of the matter density, the Hubble age, the ages of objects in the universe, the deceleration parameter, and the bound on the (unobserved) fractional time variation of the gravitational constant are too inaccurate to distinguish between the BD and Einstein-Friedmann cosmologies. An attempt is made to argue that because of the great degree of latitude in the observational constraints imposed by the BD cosmologies, efforts to improve the bound on the fractional time variation of G alone are not sufficient to rule out the BD theory.

Morganstern, R. E.↗
NASA NTRS1973

Optimal design of structures with buckling constraints.

The paper presents an iterative, finite element method for minimum weight design of structures with respect to buckling constraints. The redesign equation is derived from the optimality criterion, as opposed to a numerical search procedure, and can handle problems that are characterized by the existence of two fundamental buckling modes at the optimal design. Application of the method is illustrated by beam and orthogonal frame design problems.

Kiusalaas, J.↗
NASA NTRS1973

Quarantine constraints as applied to satellites.

Plans for unmanned missions to planets beyond Mars in the 1970s include satellite encounters. Recently published observations of data for Titan, a satellite of Saturn, indicate that conditions may be hospitable for the growth of microorganisms. Therefore, the problem of satisfying possible quarantine constraints for outer planet satellites was investigated. This involved determining the probability of impacting a satellite of Jupiter or Saturn by a spacecraft for a planned satellite encounter during an outer planet mission. Mathematical procedures were formulated which (1) determine the areas in the aim-plane that would result in trajectories that impact the satellite and (2) provide a technique for numerically integrating the navigation error function over the impact area to obtain impact probabilities. The results indicate which of the planned spacecraft trajectory correction maneuvers are most critical in terms of satellite quarantine violation.

Hoffman, A. R.↗
NASA NTRS1973

The constraint method: A new finite element technique

An approch to the finite element method which utilizes families of conforming finite elements based on complete polynomials is presented. Finite element approximations based on this method converge with respect to progressively reduced element sizes as well as with respect to progressively increasing orders of approximation. Numerical results of static and dynamic applications of plates are presented to demonstrate the efficiency of the method. Comparisons are made with plate elements in NASTRAN and the high-precision plate element developed by Cowper and his co-workers. Some considerations are given to implementation of the constraint method into general purpose computer programs such as NASTRAN.

Tsai, C.↗
NASA NTRS1974

Similarity constraints in testing of cooled engine parts

A study is made of the effect of testing cooled parts of current and advanced gas turbine engines at the reduced temperature and pressure conditions which maintain similarity with the engine environment. Some of the problems facing the experimentalist in evaluating heat transfer and aerodynamic performance when hardware is tested at conditions other than the actual engine environment are considered. Low temperature and pressure test environments can simulate the performance of actual size prototype engine hardware within the tolerance of experimental accuracy if appropriate similarity conditions are satisfied. Failure to adhere to these similarity constraints because of test facility limitations or other reasons, can result in a number of serious errors in projecting the performance of test hardware to engine conditions.

Colladay, R. S.↗
NASA NTRS1974

Space tug thermal control equipment thermal requirements, characteristics, and constraints catalogue: Users guide

This manual details the input instructions to the data bank, and explanation of the program and its output. The data bank was developed in satisfaction of two of the study tasks, the equipment thermal requirement catalog and the equipment characteristics and constraints catalog. The data bank contains 109 components within space tug avionics system. Other systems were not included in the data bank due to the available information, however, with some program modification, other systems could be incorporated into the data bank program. The data bank was developed and checked out and is compatible with the Univac 1108, and the CDC 6500 operating systems. The data contained in the data bank is general in content with emphasis on the component thermal design. The data is applicable to any spacecraft program where the components contained in the data bank can be applied in satisfaction of the system and subsystem requirements.

Ward, T. L.↗
NASA NTRS1974

Space tug thermal control equipment thermal requirements, characteristics and constraints catalogue

The Space Tug Thermal Control Study contained two tasks associated with the cataloging of equipment thermal requirements, physical characteristics and constraints. In satisfaction of these tasks a Data Bank program was developed to provide a means of standardizing the method of cataloging while using the computer to handle the data and format the data into the desired catalogues. During the course of the study 109 components were catalogued and included in the Data Bank. A standardized method was selected for describing each component. Each subsystem of the Avionics System is described on a subsystem header page which describes the types of components included within the subsystem, the quantity requirements, target weights, target power and relative comments. The individual components listed within each subsystem are not necessarily a complete list of candidate items but do represent several of the presently available components for consideration in a Tug application.

Ward, T. L.↗
NASA NTRS1973

The effect of noise constraints on engine cycle optimization for long-haul transports

Optimum engine cycles were determined for noise levels of 10, 15, and 20 EPNdB below current FAA regulations, using 200-passenger trijet aircraft flying over ranges from 5555 to 10,200 km at cruise speeds of Mach 0.90 and 0.98. The tests showed that the noise constraints imposed compromises on the optimum cycle with resulting economic penalties. The economic penalties, however, could be effectively offset by applying advanced engine technologies.

Antl, R. J.↗
NASA NTRS1974

WINDOWAC (Wing Design Optimization With Aeroelastic Constraints): Program manual

User and programer documentation for the WIDOWAC programs is given. WIDOWAC may be used for the design of minimum mass wing structures subjected to flutter, strength, and minimum gage constraints. The wing structure is modeled by finite elements, flutter conditions may be both subsonic and supersonic, and mathematical programing methods are used for the optimization procedure. The user documentation gives general directions on how the programs may be used and describes their limitations; in addition, program input and output are described, and example problems are presented. A discussion of computational algorithms and flow charts of the WIDOWAC programs and major subroutines is also given.

Haftka, R. T.↗
NASA NTRS1974

Earth Observatory Satellite system definition study. Report 2: Instrument constraints and interfaces

The instrument constraints and interface specifications for the Earth Observatory Satellite (EOS) are discussed. The Land Use Classification Mission using a 7 band Thematic Mapper and a 4 band High Resolution Pointable Imager is stressed. The mission and performance of the instruments were reviewed and expanded to reflect the instrument as a part of the total remote sensing system. A preliminary EOS interface handbook is provided to describe the mission and system, to specify the spacecraft interfaces to potential instrument contractors, and to describe the instrument interface data required by the system integration contractor.

Source record↗
NASA NTRS1974

Petrogenesis of lunar rocks: Rb-Sr constraints and lack of H2O

Rb and Sr isotopic data and other chemical data indicate major lunar differentiation at about 4.6 AE and very limited subsequent differentiation. The constraints of limited differentiation post 4.6 AE and the apparent lack of H2O on the moon, when applied to the derivation and petrogenesis of lunar samples, suggest the following: (1) soil samples, breccias, metaclastic rocks, and feldspathic basalts represent mixtures of repeatedly-modified clastic material, which was ultimately derived from materials formed during the about 4.6 AE differentiation; and (2) mare basalts crystallized from melts which formed by partial melting and, which developed without equilibration between the melt and crystalline residuum.

Albee, A. L.↗
NASA NTRS1975

A study of payload specialist station monitor size constraints

Constraints on the CRT display size for the shuttle orbiter cabin are studied. The viewing requirements placed on these monitors were assumed to involve display of imaged scenes providing visual feedback during payload operations and display of alphanumeric characters. Data on target recognition/resolution, target recognition, and range rate detection by human observers were utilized to determine viewing requirements for imaged scenes. Field-of-view and acuity requirements for a variety of payload operations were obtained along with the necessary detection capability in terms of range-to-target size ratios. The monitor size necessary to meet the acuity requirements was established. An empirical test was conducted to determine required recognition sizes for displayed alphanumeric characters. The results of the test were used to determine the number of characters which could be simultaneously displayed based on the recognition size requirements using the proposed monitor size. A CRT display of 20 x 20 cm is recommended. A portion of the display area is used for displaying imaged scenes and the remaining display area is used for alphanumeric characters pertaining to the displayed scene. The entire display is used for the character alone mode.

Kirkpatrick, M., III↗
NASA NTRS1975

A g-load display for remotely piloted vehicles and other aircraft that are subject to maneuvering constraints

The absence of kinesthetic cues deprives RPV pilots of essential feedback, particularly during high speed maneuvers. A display was designed to facilitate pilot control of g loads and to permit an immediate indication of g-load constraint violations. The display embodies all the motion vector components that contribute to maneuvering accelerations. In one mode of operation, the device displays the components of angular velocity as variable length pointers emanating from the center of a circle whose radius is determined by the linear velocity of the vehicle. An alternative mode of operation permits the pilot to select a display in which g loads are presented directly as variable length pointers emanating from the center of a circle whose radius is again determined by the linear velocity of the vehicle. Each circle defines a safe region of operation, and penetration of the circumference of the appropriate circle by a pointer implies that the structural design load was exceeded.

Howard, J. C.↗
NASA NTRS1975

Modeling damaged wings: Element selection and constraint specification

The NASTRAN analytical program was used for structural design, and no problems were anticipated in applying this program to a damaged structure as long as the deformations were small and the strains remained within the elastic range. In this context, NASTRAN was used to test three-dimensional analytical models of a damaged aircraft wing under static loads. A comparison was made of calculated and experimentally measured strains on primary structural components of an RF-84F wing. This comparison brought out two sensitive areas in modeling semimonocoque structures. The calculated strains were strongly affected by the type of elements used adjacent to the damaged region and by the choice of multipoint constraints sets on the damaged boundary.

Stronge, W. J.↗