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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 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Expandable pallet for space station interface attachments

Described is a foldable expandable pallet for Space Station interface attachments with a basic square configuration. Each pallet consists of a series of struts joined together by node point fittings to make a rigid structure. The struts have hinge fittings which are spring loaded to permit collapse of the module for stowage transport to a Space Station in the payload bay of the Space Shuttle, and development on orbit. Dimensions of the pallet are selected to provide convenient, closely spaced attachment points between the node points of the relatively widely spaced trusses of a Space Station platform. A pallet is attached to a strut at four points: one close fitting hole, two oversize holes, and a slot to allow for thermal expansion/contraction and for manufacturing tolerances. Applications of the pallet include its use in rotary or angular joints; servicing of splints; with gridded plates; as instrument mounting bases; and as a roadbed for a Mobile Service Center (MSC).

Wesselski, Clarence J.↗
NASA NTRS1988

Collet lock joint for space station truss

A lock joint for a Space Station has a series of struts joined together in a predetermined configuration by node point fittings. The fittings have removeable inserts. The lock joint has an elongated housing connected at one end to a strut. A split-fingered collet is mounted within the housing to insure reciprocal movement. A handle on the housing is connected to the collet for moving the collet into the insert where the fingers of the collet expand to lock the joint to the fitting.

Wesselski, Clarence J.↗
NASA NTRS1987

Better welds for launch vehicles

The use and benefits of automated variable polarity plasma arc (VPPA) welding of Al joints are described. The entire welding system, including welding head manipulator, weld-wire feed, torch, and power supply are computer controlled. The importance of proper torch dynamics and the control of argon gas flow through the plasma orifice are discussed. The use of arc-voltage control, the improvements in system monitoring, and the reduction or elimination of electromagnetic interferences are examined. VPPA welding is applicable to joining Space Shuttle components, and an example of its use on an External Tank of the Shuttle is presented.

Schwinghamer, Robert J.↗
NASA NTRS1987

Preliminary investigation of inertia friction welding B2 aluminides

An attempt is made to achieve inertia friction-welding in FeAl and NiAl samples, taking into account their intermetallics' compositions, extrusion parameters, and microstructural data. The energy required for the weld is stored in a rotating flywheel mass attached to one of the two pieces to be joined; when enough energy is introduced, the flywheel is disconnected and an axial load is applied which forces the spinning piece against the stationary one, converting the energy into heat by means of friction. Due to the inherent brittleness of the aluminides, a step-load program was used in which an initial, low-pressure heat buildup increased the work pieces' ductility.

Whittenberger, J. Daniel↗
NASA NTRS1987

Power flow analysis of an L-shaped plate structure

In the analysis of the vibration response and structure-borne vibration transmission between elements of a complex structure, statistical energy analysis (SEA) or finite element analysis (FEA) are generally used. However, an alternative method is using vibrational power flow techniques which can be especially useful in the mid frequencies between the optimum frequency regimes for FEA and SEA. Power flow analysis has in general been used on one-dimensional beam-like structures or between structures with point joints. In this paper, the power flow technique is extended to two-dimensional plate like structures joined along a common edge without frequency or spatial averaging the results, such that the resonant response of the structure is determined. The power flow results are compared to results obtained using FEA at low frequencies and SEA at high frequencies. The agreement with FEA results is good but the power flow technique has an improved computational efficiency. Compared to the SEA results the power flow results show a closer representation of the actual response of the structure.

Cuschieri, J. M.↗
NASA NTRS1986

Seam bonding of graphite reinforced composite panels

An account is given of the design features and operating characteristics of a method for the joining of composite parts, at a rate of 2 to 6 inches/min, in which the heating process responsible for adhesive flow at 800 F is focused upon the overlapped seam. The heating element is a self-tuning solid state power oscillator whose ferrite's toroid geometry generates a uniform, concentrated magnetic flux in the component to be bonded. Specimens cut from graphite/epoxy panels bonded with epoxy-phenolic adhesive by this process have exhibited average lap-shear strengths of the order of 3400 lbs/sq in.

Buckley, John D.↗
NASA NTRS1988

Weakly relativistic dispersion of Bernstein waves

Weakly relativistic effects on the dispersion of Bernstein waves are investigated for waves propagating nearly perpendicular to a uniform magnetic field in a Maxwellian plasma. Attention is focused on those large-wave-vector branches that are either weakly damped or join continuously onto weakly damped branches since these are the modes of most interest in applications. The transition between dispersion at perpendicular and oblique propagation is examined and major weakly relativistic effects can dominate even in low-temperature plasmas. A number of simple analytic criteria are obtained which delimit the ranges of harmonic number and propagation angle within which various types of weakly damped Bernstein modes can exist.

Robinson, P. A.↗
NASA NTRS1988

Development and properties of aluminum-clad graphite/epoxy tubes for space structures

This paper presents the development and properties of seamless aluminum-clad P75/Epoxy tubes and the unique manufacturing method used in their production. Thermo-mechanical properties of the tubes were determined analytically and verified by tests. These properties were shown to be suitable for space structures that require high stiffness, low weight and thermal expansion, and dimensional stability during operational life. A special feature of the tubes is the ability to tune the tube for thermal expansion after fabrication by a chemical milling process. The tubes are also resistant to atomic oxygen and handling damage. The toughness of the tubes was demonstrated by impact testing. Cyclic thermal testing showed no adverse effects on the expansion and stiffness behavior of the tubes. The paper also includes a discussion of a joining method that uses aluminum end fittings and an efficient scarf joint configuration. Additional studies considered various adhesives and fitting materials. Joint allowables were higher for titanium and B4C particulate magnesium fittings. The effect of different adhesives under static loading conditions favored the high-strength adhesives.

Johnson, R. R.↗
NASA NTRS1988

Experimental component mode synthesis of structures with sloppy joints

The accuracy of component mode synthesis is investigated experimentally for substructures coupled by nonideal joints. The work is based upon a segmented experimental beam for which free-interface frequency response matrices are measured for each segment. These measurements are used directly in component mode synthesis to predict the behavior of the assembled structure; the segments are then physically joined, and the resulting frequency response of the superstructure is compared to the prediction. Rotational freeplay is then introduced into the connecting joint, and the new superstructure frequency response is compared to the original linear component mode synthesis prediction. The level of accuracy to be expected in component mode synthesis is discussed in terms of the degree of nonlinearity in the joints, mode number, and mode shapes.

Blackwood, Gary H.↗
NASA NTRS1988

The northern extension of the radio arc near the Galactic center

High-resolution observations of the positive-latitude extension of the radio continuum arc at 1 = 0.2 deg, the northern polarized lobe, have been carried out at both 6 and 20 cm wavelengths. These observations show clearly that the northern lobe is composed of a number of filaments which join continuously with the more prominent, linear, filamentary structures constituting the radio continuum arc, thus confirming the suggestion based on single-dish observations that the polarized lobe and the arc are physically associated. Attention is drawn to a puzzling absorption filament adjacent to the nonthermal filaments in the 6 cm images, implying the existence of a thermal component associated with the system of nonthermal filaments. These observations help clarify the spatial relationship between the thermal and nonthermal structures constituting the continuum arc, provide pictorial evidence that the nonthermal and thermal features are interacting, and support the hypothesis that the geometry of the magnetic field is poloidal near the Galactic center. The images are used to argue against the suggestion that the lobe is a manifestation activity associated with the Galactic nucleus.

Yusef-Zadeh, Farhad↗
NASA NTRS1988

On multigrid methods for the Navier-Stokes Computer

The overall architecture of the multipurpose parallel-processing Navier-Stokes Computer (NSC) being developed by Princeton and NASA Langley (Nosenchuck et al., 1986) is described and illustrated with extensive diagrams, and the NSC implementation of an elementary multigrid algorithm for simulating isotropic turbulence (based on solution of the incompressible time-dependent Navier-Stokes equations with constant viscosity) is characterized in detail. The present NSC design concept calls for 64 nodes, each with the performance of a class VI supercomputer, linked together by a fiber-optic hypercube network and joined to a front-end computer by a global bus. In this configuration, the NSC would have a storage capacity of over 32 Gword and a peak speed of over 40 Gflops. The multigrid Navier-Stokes code discussed would give sustained operation rates of about 25 Gflops.

Nosenchuck, D. M.↗
NASA NTRS1988

Lightweight structural design of a bolted case joint for the Space Shuttle Solid Rocket Motor

This paper presents the structural design of a bolted joint with a static face seal which can be used to join Space Shuttle Solid Rocket Motor (SRM) case segments. Results from numerous finite element parametric studies indicate that the bolted joint meets the design requirement of preventing joint opening at the O-ring locations during SRM pressurization. A final design recommended for further development has the following parameters: 180 1-inch-diameter studs, stud center line offset of .5 inches radially inward from the shell wall center line, flange thickness of 0.75 inches, bearing plate thickness of 0.25 inches, studs prestressed to 70 percent of ultimate load, and the intermediate alcove. The design has a mass penalty of 1096 lbm, which is 164 lbm greater than the currently proposed capture tang redesign.

Dorsey, John T.↗
NASA NTRS1987

A transputer based finite element solver

The feasibility of performing FEM structural-mechanics analyses on transputer systems is investigated experimentally. Transputers are programmable microprocessors equipped with local memory and point-to-point communication links; they can be joined in a large concurrent system via a programming language which supports distributed processing; this permits parallel processing at relatively low hardware cost. The computational tasks required by FEM programs are reviewed; the hardware (one PC, one master transputer, and 12 slave transputers) employed in the test calculations is described; and results demonstrating the speed and efficiency of the transputer array in assembling a global stiffness matrix and performing Gauss-Jordan matrix inversion are presented in graphs. It is predicted that larger transputer networks could approach the power of supercomputers at minicomputer costs.

Favenesi, J. A.↗
NASA NTRS1989

Gas-Jet Cooling Would Improve Czochralski Process

Controlled cooling by jets of gas improves growth of single crystals of silocon by Czochralski process, according to study. Rate of cooling by jets joins temperature of crucible and pulling rate as input variable of process adjusted to achieve required diameter of crystal and shape of crystal/melt interface. Critical parameters of growing crystal, output variables of Czochralski process controlled via two or all three of input variables. One input variable, usually speed, held constant while other two adjusted to achieve required diameter and interface.

Dudukovic, M. P.↗
NASA NTRS1989

Standard Method For Radiation Tests Of Liquids

Simple procedure provides standard method for radiation tests of liquids. Assures identical handling and dosage so data from different test laboratories compared reliably. Pair of glass vials, joined by frangible neck and equipped with valves, used. Third vial also used. Filled with control specimen and not irradiated. Developed for measuring properties of liquids for use in radiation-resistant liquid-dielectric capacitors, procedure used for any of variety of liquids proposed for use in high-radiation environment - in x-ray and particle-accelerating machines and nuclear reactors, for example.

Bouquet, Frank L.↗
NASA NTRS1989

Robotic Target-Tracking Subsystem

Position and orientation of target measured in six degrees of freedom. Robotic vision subsystem measures relative position and orientation of specially designed target. Uses standard image-processing algorithms implemented directly in circuitry instead of computer programs. This feature makes it possible to extract complete sets of target-tracking data from successive image frames at rate of 30 frames per second. Five bright circles of target positioned in such way that video images of them processed into data on position and orientation of target relative to camera. Subsystem useful in industrial assembly operation requiring automatic joining of parts initially oriented and moving randomly.

Shawaga, Lawrence M.↗
NASA NTRS1989

Compliant Prosthetic Or Robotic Joint

Rotation partly free and partly restrained by resilience and damping. Joint includes U-shaped x- and y-axis frames joined by cables that cross in at center piece. The y-axis frame rotates about y-axis on roller bearing within predetermined angular range. The y-axis frame rotates slightly farther when arm strikes stop, because cables can twist. This mimics compliant resistance of knee joint reaching limit of its forward or backward motion. Used in prosthetic device to replace diseased or damage human joint, or in robot linkage to limit movement and cushion overloads.

Kerley, James J.↗
NASA NTRS1988

Lightweight structural design of a bolted case joint for the space shuttle solid rocket motor

The structural design of a bolted joint with a static face seal which can be used to join Space Shuttle Solid Rocket Motor (SRM) case segments is given. Results from numerous finite element parametric studies indicate that the bolted joint meets the design requirement of preventing joint opening at the O-ring locations during SRM pressurization. A final design recommended for further development has the following parameters: 180 one-in.-diam. studs, stud centerline offset of 0.5 in radially inward from the shell wall center line, flange thickness of 0.75 in, bearing plate thickness of 0.25 in, studs prestressed to 70 percent of ultimate load, and the intermediate alcove. The design has a mass penalty of 1096 lbm, which is 164 lbm greater than the currently proposed capture tang redesign.

Dorsey, John T.↗