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At least 1,189 records · Page 66

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NASA NTRS1980

Research on graphite reinforced glass matrix composites

High levels of mechanical performance in tension, flexure, fatigue, and creep loading situations of graphite fiber reinforced glass matrix composites are discussed. At test temperatures of up to 813 K it was found that the major limiting factor was the oxidative instability of the reinforcing graphite fibers. Particular points to note include the following: (1) a wide variety of graphite fibers were found to be comparable with the glass matrix composite fabrication process; (2) choice of fiber, to a large extent, controlled resultant composite performance; (3) composite fatigue performance was found to be excellent at both 300 K and 703 K; (4) composite creep and stress rupture at temperatures of up to 813 K was limited by the oxidative stability of the fiber; (5) exceptionally low values of composite thermal expansion coefficient were attributable to the dimensional stability of both matrix and fiber; and (6) component fabricability was demonstrated through the hot pressing of hot sections and brazing using glass and metal joining phases.

Prewo, K. M.↗

NASA NTRS1980

Multiple band circularly polarized microstrip antenna

A multiple antenna assembly for communicating electromagnetic radiation is disclosed. An antenna element stack is constructed of a plurality of elliptical lamina antenna elements mutally separated by layers of dielectric material, and separated from a ground plane by dielectric material. The antenna assembly is coupled through a feed line in contact with the top antenna element. A conductor joins the remaining antenna elements to the ground plane. Each individual antenna element is operable for communication reception and transmission within a frequency band determined by the size of the particular antenna element. The sizes of the antenna elements may be selected to provide electromagnetic radiation communication over several distinct frequency bands, or to connect the individual bands into a broad band.

Yu, I. P.↗

NASA NTRS1980

Large space structures activity at MSFC

This paper describes a broad based set of activities which have been undertaken at the Marshall Space Flight Center (MSFC) developing technologies necessary to emplace and operate large structures in space. Progress has been made in the development of processes and equipment needed for the in space fabrication of structural members in both aluminum and graphite composite materials. Designs for member joining attachments have been completed and the evaluation of procedures for structural assembly have been simulated and evaluated utilizing the MSFC Neutral Buoyancy Facility. A concept of a flight test necessary for flight verification of the technologies for space fabrication, assembly, and operation of large space structure is described. Recently initiated is a project to develop design characteristics of a deployable structure required for the Science and Applications Space Platform (SASP). This is being accomplished through the design, fabrication, analysis, and test of a full scale ground test article which reflects the influence of system requirements of the SASP. Development of designs for erectable/deployable structures which are modular and have various applications to large space structures is in progress.

Denton, S. J.↗

NASA NTRS1980

Effect of inflow control on inlet noise of a cut-on fan

A cut-on, high tip speed fan stage was acoustically tested with three configurations of an inflow control device in the NASA Lewis anechoic chamber. Although this was a cut-on design, rotor-inflow interaction appeared to be a much stronger source of blade passing tone radiated from the inlet than rotor-stator interaction for the 1.6 mean rotor chord separation. Aft external suction applied to the area where the inflow control device joined the inlet produced a further reduction in blade passing tone suggesting that disturbances in the forward flow on the outside of the inlet were superimposed on the inlet boundary layer and were a significant source of tone noise.

Woodward, R. P.↗

NASA NTRS1980

Welding of the external tank of the Space Shuttle

Welding processes and assembly techniques used in the fabrication of the external tank of the Space Shuttle are discussed. Each external tank consists of one liquid oxygen tank and one liquid hydrogen tank connected by an intertank skirt which is mechanically assembled; the fabrication of the external tank pressure vessel involves about 36,000 linear inches of weld required to join 138 pieces of 2219 aluminum. The discussion includes several innovations, such as building domes using the 1/4 panel assembly technique, which have been used in the fabrication of the tank.

Clover, F. R., Jr.↗

NASA NTRS1982

Assembling Multicolor Printing Plates

Improved joining method uses wave-soldering techniques developed for integrated-circuit-board assemblies. Thermosetting plastic is replaced by wave soldering, which applies a thin even coat of solder to mating copper surfaces. This is done after ink holes and channels have been protected by water-soluble, high-temperature solder mask which prevents wetting and clogging.

Waters, W. J.↗

NASA NTRS1980

A probabilistic analysis of electrical equipment vulnerability to carbon fibers

The statistical problems of airborne carbon fibers falling onto electrical circuits were idealized and analyzed. The probability of making contact between randomly oriented finite length fibers and sets of parallel conductors with various spacings and lengths was developed theoretically. The probability of multiple fibers joining to bridge a single gap between conductors, or forming continuous networks is included. From these theoretical considerations, practical statistical analyses to assess the likelihood of causing electrical malfunctions was produced. The statistics obtained were confirmed by comparison with results of controlled experiments.

Elber, W.↗

NASA NTRS1980

Nonlinear dynamic response of a uni-directional model for the tile/pad space shuttle thermal protection system

A unidirectional analysis of the nonlinear dynamic behavior of the space shuttle tile/pad thermal protection system is developed and examined for imposed sinusoidal and random motions of the shuttle skin and/or applied tile pressure. The analysis accounts for the highly nonlinear stiffening hysteresis and viscous behavior of the pad which joins the tile to the shuttle skin. Where available, experimental data are used to confirm the validity of the analysis. Both analytical and experimental studies reveal that the system resonant frequency is very high for low amplitude oscillations but decreases rapidly to a minimum value with increasing amplitude. Analytical studies indicate that with still higher amplitude the resonant frequency increases slowly. The nonlinear pad is also responsible for the analytically and experimentally observed distorted response wave shapes having high sharp peaks when the system is subject to sinusoidal loads. Furthermore, energy dissipation in the pad is studied analytically and it is found that the energy dissipated is sufficiently high to cause rapid decay of dynamic transients. Nevertheless, the sharp peaked nonlinear responses of the system lead to higher magnification factors than would be expected in such a highly damped linear system.

Housner, J. M.↗

NASA NTRS1980

Dual methods and approximation concepts in structural synthesis

Approximation concepts and dual method algorithms are combined to create a method for minimum weight design of structural systems. Approximation concepts convert the basic mathematical programming statement of the structural synthesis problem into a sequence of explicit primal problems of separable form. These problems are solved by constructing explicit dual functions, which are maximized subject to nonnegativity constraints on the dual variables. It is shown that the joining together of approximation concepts and dual methods can be viewed as a generalized optimality criteria approach. The dual method is successfully extended to deal with pure discrete and mixed continuous-discrete design variable problems. The power of the method presented is illustrated with numerical results for example problems, including a metallic swept wing and a thin delta wing with fiber composite skins.

Fleury, C.↗

NASA NTRS1980

Geometric methods in computational fluid dynamics

General methods for the construction of geometric computational fluid dynamic algorithms are presented which simulate a variety of flow fields in various nontrivial regions. Included are: basic developments with tensors; various forms for the equations of motion; generalized numerical methods and boundary conditions; and methods for mesh generation to meet the strong geometric constraints of turbomachines. Coordinate generation is shown generally to yield mesh descriptions from one or more transformations that are smoothly joined together to form a composite mesh.

Eiseman, P. R.↗

NASA NTRS1981

Erectable concepts for large space system technology

Design features of components for space erectable/deployable concepts are described along with the neutral buoyancy testing with the shuttle remote manipulator system. The basic structural configuration is a double folding cubic module. It is 3 meters by 3 meters in crosssection by 6 meters long. The first folding operation results in a 3 meter by 6 meter planar configuration. The second folding operation results in a 9 meter linear configuration. Folding (deployment) is achieved by single and double pivoting joints and telescoping diagonal members. Deployment and retraction is accomplished by an external force. Two joining devices, the module to module coupler and the automatic coupler, were designed and fabricated for test. The module to module coupler features angular and axial locking compliances of 10 deg and 2.5 mm, respectively. It also has a linear zero free play stiffness characteristic.

Agan, W. E.↗

NASA NTRS1981

Modular reflector concept study

The feasibility was studied of constructing large space structures, specifically a 100 meter paraboloidal R.F. reflector, by individually deploying a number of relatively small structural modules, and then joining them to form a single large structure in orbit. The advantage of this approach is that feasibility of a large antenna may be demonstrated by ground and flight tests of several smaller and less costly subelements. Thus, initial development costs are substantially reduced and a high degree of reliability can be obtained without commitment to construction of a very large system. The three candidate structural concepts investigated are: (1) the deployable cell module; (2) the paraboloidal extendable truss antenna adapted to modular assembly; and (3) the modular extendable truss antenna (META).

Vaughan, D. H.↗

NASA NTRS1981

Multifunctional transducer

Several parameters of a small region of a muscle tissue or other object, can be simultaneously measured using with minimal traumatizing or damage of the object, a trifunctional transducer which can determine the force applied by a muscle fiber, the displacement of the fiber, and the change in thickness of the fiber. The transducer has three legs with inner ends joined together and outer ends formed to piece the tissue and remain within it. Two of the legs are relatively stiff, to measure force applied by the tissue, and a third leg is relatively flexible to measure displacement of the tissue relative to one or both stiff legs, and with the three legs lying in a common plane so that the force and displacement measurements all relate to the same direction of muscle movements. A flexible loop is attached to one of the stiff legs to measure changes in muscle thickness, with the upper end of the loop fixed to the leg and the lower end of the loop bearing against the surface of the tissue and being free to slide on the leg.

Feldstein, C.↗

NASA NTRS1980

Aboard the Space Shuttle

Livability aboard the space shuttle orbiter makes it possible for men and women scientists and technicians in reasonably good health to join superbly healthy astronauts as space travelers and workers. Features of the flight deck, the mid-deck living quarters, and the subfloor life support and house-keeping equipment are illustrated as well as the provisions for food preparation, eating, sleeping, exercising, and medical care. Operation of the personal hygiene equipment and of the air revitalization system for maintaining sea level atmosphere in space is described. Capabilities of Spacelab, the purpose and use of the remote manipulator arm, and the design of a permanent space operations center assembled on-orbit by shuttle personnel are also depicted.

Steinberg, F. S.↗

NASA NTRS1980

Fundamental heat transfer research for gas turbine engines

Thirty-seven experts from industry and the universities joined 24 NASA Lewis staff members in an exchange of ideas on trends in aeropropulsion research and technology, basic analyses, computational analyses, basic experiments, near-engine environment experiments, fundamental fluid mechanics and heat transfer, and hot technology as related to gas turbine engines. The workshop proceedings described include pre-workshop input from participants, presentations of current activity by the Lewis staff, reports of the four working groups, and a workshop summary.

Metzger, D. E.↗

NASA NTRS1981

Development of a composite geodetic structure for space construction, phase 2

Primary physical and mechanical properties were defined for pultruded hybrid HMS/E-glass P1700 rod material used for the fabrication of geodetic beams. Key properties established were used in the analysis, design, fabrication, instrumentation, and testing of a geodetic parameter cylinder and a lattice cone closeout joined to a short cylindrical geodetic beam segment. Requirements of structural techniques were accomplished. Analytical procedures were refined and extended to include the effect of rod dimensions for the helical and longitudinal members on local buckling, and the effect of different flexural and extensional moduli on general instability buckling.

Source record↗

NASA NTRS1980

An experimental test of the electromagnetic ion cyclotron instability within the earth's magnetosphere

Examples of propagating electromagnetic Alfven/ion cyclotron waves in plasma particle and magnetic field data observed by the ATS-6 geostationary satellite are discussed. These waves were viewed mainly near the afternoon and dusk regions of the earth's magnetosphere with normalized frequencies in the 0.05 to 0.5 range. Two wave events were analyzed: both appeared coincidentally with the encounter of cool plasma populations which joined the hot populations already present. An electromagnetic ion cyclotron instability was proposed as the wave generation mechanism; this theory was tested by evaluating the linear growth integrals under the measured anisotropic hot ion distribution.

Mauk, B. H.↗

NASA NTRS1981

Neutral buoyancy test results of a deployable space beam

Large erectable and deployable space structures have been studied extensively in the past few years with a view toward usage in the near future for space platforms. The paper covers in particular the operational testing of a double-cell, double-folding cubic aluminum module at the Marshall Space Flight Center Neutral Buoyancy Simulator. Joining methods, deployment kinematics, configurations and operation time lines were analyzed using the Shuttle Remote Manipulator System (RMS) and EVA crewmen. Results of the test were considered successful, with crew tasks accomplished and the structural design adequate for flight design.

Stokes, J. W.↗