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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Mechanics of load transfer at the interface

The mechanism of load transfer from matrix to fiber though the interface and, as a consequence, the effects of the interface on composite structural integrity are discussed. Specifically, the present work deals with the role of interfacial bonding in composite strength, the dependence of fracture surface on interface bond strength, and methods of measuring and predicting the stress at the interface, the microresidual stress, and load condition effects on the interface bond. The possibility of designing composites with specified bond properties is examined. Many of these effects are illustrated graphically to indicate general trends and to illustrate significant points. The discussion is based on theoretical considerations and is supplemented with pertinent experimental data.

Chamis, C. C.↗
NASA NTRS1975

A model for the origin of solar wind stream interfaces

The basic variations in solar wind properties that have been observed at 'stream interfaces' near 1 AU are explained by a gas dynamic model in which a radially propagating stream, produced by a temperature variation in the solar envelope, steepens nonlinearly while moving through interplanetary space. The region thus identified with the stream interface separates the ambient solar wind from the fresh hot material originally in the stream. However, the interface regions given by the present model are thicker than most stream interfaces observed in the solar wind, a fact suggesting that some additional physical process may be important in determining that thickness. Variations in the density, speed, or Alfven pressure alone appear not to produce streams with such an interface.

Hundhausen, A. J.↗
NASA NTRS1975

Tug and payload-to-Orbiter interface requirements

This paper presents results of a study to identify, evaluate, and develop Tug plus payload-to-Orbiter accommodation requirements. Interface areas include structural, mechanical, fluids, environmental, avionics, and safety. Each interface area was investigated to determine the best physical and operational method of accomplishing the required functions with an overriding goal of establishing sample and flexible interface requirements suitable for Tug, Tug payloads, and other cargo. The recommended system for supporting the Tug and its payload from the Orbiter employs a cylindrical load-carrying structure called a deployment adapter that has a rotational capability for Tug deployment. The design and operation of the deployment adapter and other peripheral interface equipment such as crew compartment monitor and control panels and cargo bay fluid and electrical interface panels are discussed.

Bock, E. H.↗
NASA NTRS1975

Tug payload interfaces

Some conclusions reached during the IUS/Tug payload requirements compatibility study are presented. This study is concerned with all prospective Tug-payload interfaces, including detailed analysis of low-earth orbit, geosynchronous, and interplanetary missions. Tug payload requirements are discussed and summarized as to operational requirements, structural/mechanical interface, avionics interfaces, fluids interface, and environment. The shuttle impacts created by Tug/payload interfaces are examined and presented in tabular form. Major conclusions are that all payloads in the mission model can be suitably and inexpensively accommodated by the Tug and the Shuttle if standardized integration equipment is employed, that multiple payloads pose no significant integration challenge, and that a relatively small inventory of integration equipment is required to support all prospective payloads.

Runge, F.↗
NASA NTRS1976

An interface between a datametrics 1085A manometer and a Hewlett-Packard 2100S computer

A hardware/software interface designed to mate a Datametrics models 1085A electronic manometer to a Hewlett-Packard (HP) model 2100S computer is described. The software driver operates in the basic control system (BCS) and requires 173 words of memory; the hardware interface uses an HP data source interface (DSI) card which requires one computer input/output channel. Results obtained by incorporating this interface into a data acquisition system indicate that the interface operates successfully.

Hillard, M. E., Jr.↗
NASA NTRS1977

Surface charge kinetics near metal-dielectric interfaces exposed to kilovolt electron flux

Interfaces between dielectric films and grounded metallic boundaries were exposed, in vacuum, to monoenergic electron fluxes having energies up to 22 keV. Two principal concerns were the measuring of the charge distributions on dielectrics and the determining of causes of flashovers, events where dielectric surface charges abruptly transfer to the metallic structures. Surface charges are perturbed within 10 mm of interfaces. Perturbations are relatively small except within about 3 mm of the interface. The probability of flashover was found to be related to microscopic imperfections in the interfaces. As flashovers occur in an exposed metal substrate, points become burned into the dielectric along the slit. As these points develop, the probability of flashover increases greatly. An interface which is highly immune to flashover was formed by covering a dielectric film with a 1.5-mm-thick aperture plate which exposes the film through a machined opening.

Robinson, J. W.↗
NASA NTRS1978

Solar wind stream interfaces

Results are presented for a superposed epoch analysis of discontinuous solar wind interfaces. The average time-space profiles of stream interfaces are discussed with reference to fluid properties (flow speed, pressure ridge, density, electron and proton temperatures) and kinetic properties (electron core and halo, flow speed fluctuations, electron heat flux, alpha particles). Other aspects of stream interfaces are described, such as the persistence of individual interfaces, shock associations, the sector boundaries of the interplanetary magnetic field, and sudden impulses in the geomagnetic field. Interface position is considered in terms of the observed temperature jump. A conceptual model of high-speed stream evolution is proposed.

Gosling, J. T.↗
NASA NTRS1982

NASA payload interface verification requirements - Process and implementation

The separate and combinatorial roles played by NASA and STS payload contractors in the processes of interfacing cargo with the Shuttle are described. NASA personnel aid payload interface verification beginning at the hardware development level and perform independent interface verification once the payload is delivered to the payload processing facility. The cargo is first checked for operational and flight readiness, including inspection of installed devices to specification for the interface connections. Checklists furnished to the user are returned to NASA prior to integration simulation unless formal statements of compliance or waivers are exchanged. The continuance of strict adherence to predelivery interface verification testing is emphasized as necessary for meeting the turnaround times projected for the Orbiter fleet.

Huffstetler, W. J.↗
NASA NTRS1982

Finite element analysis of the effect of a non-planar solid-liquid interface on the lateral solute segregation during unidirectional solidification

The effect of solid-liquid interface shape on lateral solute segregation during steady-state unidirectional solidification of a binary mixture is calculated under the assumption of no convection in the liquid. A finite element technique is employed to compute the concentration field in the liquid and the lateral segregation in the solid with a curved boundary between the liquid and solid phases. The computational model is constructed assuming knowledge of the solid-liquid interface shape; no attempt is made to relate this shape to the thermal field. The influence of interface curvature on the lateral compositional variation is investigated over a range of system parameters including diffusivity, growth speed, distribution coefficient, and geometric factors of the system. In the limiting case of a slightly nonplanar interface, numerical results from the finite element technique are in good agreement with the analytical solutions of Coriell and Sekerka obtained by using linear theory. For the general case of highly non-planar interface shapes, the linear theory fails and the concentration field in the liquid as well as the lateral solute segregation in the solid can be calculated by using the finite element method.

Carlson, F. M.↗
NASA NTRS1984

The pilot interface with cockpit automation and advanced avionics systems

A flight test program was conducted with a sophisticated, integrated avionics system to study pilot workload and the pilot interface with high levels of avionics capability. The study indicates that advanced systems can provide improved information to the pilot and additional functional capability. The study also indicates that additional research is needed to develop the knowledge base required to design pilot interfaces with such systems. The combination of the pilot interface and the high level of system capability used in this study led to pilot blunders associated with navigation data management, autopilot management, and maintaining awareness of system status. A functional relationship is suggested between level of avionics system sophistication and the required state-of-the-art in pilot/avionics interface design. Suggested guidelines for the design of the pilot/avionics interface for advanced avionics systems are given.

Hinton, D. A.↗
NASA NTRS1984

The Multimission Image Processing Laboratory's virtual frame buffer interface

Large image processing systems use multiple frame buffers with differing architectures and vendor supplied interfaces. This variety of architectures and interfaces creates software development, maintenance and portability problems for application programs. Several machine-dependent graphics standards such as ANSI Core and GKS are available, but none of them are adequate for image processing. Therefore, the Multimission Image Processing laboratory project has implemented a programmer level virtual frame buffer interface. This interface makes all frame buffers appear as a generic frame buffer with a specified set of characteristics. This document defines the virtual frame uffer interface and provides information such as FORTRAN subroutine definitions, frame buffer characteristics, sample programs, etc. It is intended to be used by application programmers and system programmers who are adding new frame buffers to a system.

Wolfe, T.↗
NASA NTRS1985

Productivity issues at organizational interfaces

The need for close interdependence between large numbers of diverse and specialized work groups makes the Space Program extremely vulnerable to loss of productivity at organizational interfaces. Trends within the program also suggest that the number and diversity of interfaces will grow in the near term. Continued maintenance of R&D excellence will require that interface performance issues be included in any future productivity improvement effort. The types and characteristics of organizational interfaces are briefly presented, followed by a review of factors which impact their productivity. Approaches to assessing and improving interface effectiveness are also discussed.

Holland, A. W.↗
NASA NTRS1986

Interface of the transport systems research vehicle monochrome display system to the digital autonomous terminal access communication data bus

An upgrade of the transport systems research vehicle (TSRV) experimental flight system retained the original monochrome display system. The original host computer was replaced with a Norden 11/70, a new digital autonomous terminal access communication (DATAC) data bus was installed for data transfer between display system and host, while a new data interface method was required. The new display data interface uses four split phase bipolar (SPBP) serial busses. The DATAC bus uses a shared interface ram (SIR) for intermediate storage of its data transfer. A display interface unit (DIU) was designed and configured to read from and write to the SIR to properly convert the data from parallel to SPBP serial and vice versa. It is found that separation of data for use by each SPBP bus and synchronization of data tranfer throughout the entire experimental flight system are major problems which require solution in DIU design. The techniques used to accomplish these new data interface requirements are described.

Easley, W. C.↗
NASA NTRS1985

Stability of interfaces with mesh refinement

A study is conducted of the stability of mesh refinement in space and time for several different interface equations and finite-difference approximations. First, a root condition which implies stability for the initial-boundary value problem for this type of interface is derived. From the root condition, the stability of several interface equations is proved, using the maximum principle. In some cases, the final verification steps can be done analytically; in other cases, a simple computer program has been written to check the condition for values of a parameter along the boundary of the unit circle. Using this method, stability for Lax-Wendroff with all the interface conditions considered, and for Leapfrog with interpolation interface conditions when the fine and coarse grids overlap is proved.

Berger, M. J.↗
NASA NTRS1986

Interaction of flows with the crystal-melt interface

The coupling between a crystal-melt interface and fluid flow is investigated. The solidification boundary conditions at the crystal-melt interface are described. The influences of morphological and double-diffusive instabilities during directional solidification on the interface are studied. The experiments by Glicksman and Mickalonis (1982) and Fang et al. (1985) which examine the relationship between the hydrodynamic state of the phase melt and phase-change interface are analyzed. The Rayleigh-Benard problem, and the effect of crystal-melt interaction on the Rayleigh number are examined. Various applications for melt-flow interactions with solid-liquid interface to engineering and welding are discussed.

Glicksman, M. E.↗
NASA NTRS1985

Interface shape in Czochralski grown crystals - Effect of conduction and radiation

A sequential modular computational scheme has been proposed for the calculation of temperature profiles in the melt and crystal including the melt-crystal interface shape and the crystal pulling rate for a fixed crystal radius. The heat transfer in the melt is assumed to occur by conduction only. The shape of melt-gas meniscus, described by Laplace-Young equation, is incorporated in the model and its effects on interface shape and pulling rate are examined. Further, the model incorporates the detailed radiation interaction among the various surfaces in the puller using the Gebhart enclosure theory which accounts for both direct and reflected radiation. The effects of various process parameters on the interface shape and the pulling rate have been investigated. The results of this study indicate that the shape of the melt-gas meniscus has a significant effect on the pulling rate and the interface shape in conformity with earlier studies. Further, it is shown that a simple radiation model (Stefan's model) is inadequate to model the radiation heat exchange in the Czochralski puller apparatus and the detailed Gebhart analysis is necessary for accurate calculation of both the temperature profile in the crystal as well as the interface shape.

Srivastava, R. K.↗
NASA NTRS1987

The desktop interface in intelligent tutoring systems

The interface between an Intelligent Tutoring System (ITS) and the person being tutored is critical to the success of the learning process. If the interface to the ITS is confusing or non-supportive of the tutored domain, the effectiveness of the instruction will be diminished or lost entirely. Consequently, the interface to an ITS should be highly integrated with the domain to provide a robust and semantically rich learning environment. In building an ITS for ZetaLISP on a LISP Machine, a Desktop Interface was designed to support a programming learning environment. Using the bitmapped display, windows, and mouse, three desktops were designed to support self-study and tutoring of ZetaLISP. Through organization, well-defined boundaries, and domain support facilities, the desktops provide substantial flexibility and power for the student and facilitate learning ZetaLISP programming while screening the student from the complex LISP Machine environment. The student can concentrate on learning ZetaLISP programming and not on how to operate the interface or a LISP Machine.

Baudendistel, Stephen↗
NASA NTRS1988

Service offerings and interfaces for the ACTS network of Earth stations

The Advanced Communications Satellite (ACTS) is capable of two modes of communication. Mode 1 is a mesh network of Earth stations using baseband-switched, time-division multiple-access (BBS-TDMA) and hopping beams. Mode 2 is a mesh network using satellite-switched, time-division multiple-access (SS-TDMA) and fixed (or hopping) beams. The purpose of this paper is to present the functional requirements and the design of the ACTS Mode 1 Earth station terrestrial interface. Included among the requirements are that: (1) the interface support standard telecommunications service offerings (i.e., voice, video and data at rates ranging from 9.6 kbps to 44 Mbps); (2) the interface support the unique design characteristics of the ACTS communications systems (e.g., the real time demand assignment of satellite capacity); and (3) the interface support test hardware capable of validating ACTS communications processes. The resulting interface design makes use of an appropriate combination of T1 or T3 multiplexers and a small central office (maximum capacity 56 subscriber lines per unit).

Coney, Thom A.↗