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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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Design evolution of a low shock release nut

Design improvements and detailed functional analyses are reviewed to trace the development of a pyroactuated release device with segmented thread design from its intermediate design into one that reduces the levels of shock spectra generated during its operation by 50%. Comparisons of shock output and internal load distribution are presented, along with descriptions of mechanical operation for both designs. Results also show the potential areas where design development activity can gain further progress in lowering actuation shock levels.

Otth, D. H.↗
NASA NTRS1976

Transverse tensile and stress rupture properties of gamma/gamma prime-delta directionally solidified eutectic

Tensile and stress rupture properties were determined primarily at 760 C for specimens oriented at various angles (0 deg, 10 deg, 45 deg, and 90 deg) from the solidification direction of bars and/or slabs of the Ni-20Cb-6Cr-2.5A (gamma/gamma prime-delta) eutectic. Threaded-head specimens yielded longer rupture lives with significantly less scatter than did tapered-head specimens. Miniature specimens are suitable for determining traverse tensile and rupture properties of 1.2 centimeter diameter bar stock. The 300 hour rupture stress at 760 C for specimens oriented at 10 deg from the solidification direction was reduced from 740 to 460 MPa, and to 230 MPa for material oriented at either 45 deg or 90 deg.

Gray, H. H.↗
NASA NTRS1976

A local diffusion process associated with the sweeping of energetic particles by Io

A local, turbulent diffusion process which may rapidly refill the partial cavity of energetic particles created by Io's passage through a flux tube is discussed. A model is developed of Io's sweeping action on energetic particles in which a wake is formed behind the flux tube threading Io. It is shown to be possible that this wake contains an excess of positive charge, thereby creating an electric field. The particle drift produced by this field, coupled with the density gradient of energetic protons, can generate an instability. It is this instability that is responsible for the turbulent diffusion process. The sweeping of energetic particles is also discussed in relation to particle energy and pitch angle distribution.

Huba, J. D.↗
NASA NTRS1976

Plasma injection at synchronous orbit and spatial and temporal auroral morphology

Analysis of ATS 5 particle spectrograms and simultaneous meridian-scanning photometer data obtained at the base of the ATS field line has revealed systematic relationships between temporal and spatial auroral morphology and particle-injection events. The details of these relationships depend on previous injection events, the local time of the observatory with respect to current-injection events, and the extent and magnitude of current injections. A persistent zone of weak aurora is related to steady plasma-sheet drizzle, and the equatorward edge of this aurora delineates field lines threading the inner edge of the plasma sheet. Auroras associated with injection events superimpose on this preexisting pattern, with the lowest latitude of new precipitation depending on local time. In general, plasma energization is not required between the equatorial plane and the ionosphere to account for observed auroral intensities. The data indicate occasional occurrence of enhanced loss-cone fluxes, suggesting low-altitude field-aligned acceleration. A summary figure shows how various characteristic auroral-precipitation regions are related to the shape, extent, and orientation of the substorm injection boundary and to the subsequent drift paths of injected plasma.

Eather, R. H.↗
NASA NTRS1978

No-spill touchup paint container

Container has two-piece threaded device that is installed in hole in standard metal lid. In addition to preventing spillage, device provides better brush support and wiper edge.

Peters, R. L.↗
NASA NTRS1976

Impact tensile testing of wires

The test consists of fixing one end of a wire specimen and allowing a threaded falling weight to strike the other. Assuming the dynamic stress in the wire to be a function only of its strain, energy considerations show for negligible wire inertia effects that the governing dynamic stress-strain law can be determined directly from impact energy vs. wire elongation data. Theoretical calculations are presented which show negligible wire inertia effects for ratios of wire mass to striking mass of the order of .01 or less. The test method is applied to soft copper wires and the dynamic stress-strain curve so determined is found to be about 30 percent higher than the corresponding static curve.

Dawson, T. H.↗
NASA NTRS1977

The effect of configuration on strength, durability, and handle of Kevlar fabric-based materials

Five Kevlar based laminates and three Kevlar based coated materials were designed, hand made, and tested against comparative conventional Dacron based materials for strength, peel, tear, puncture, creases, and handle. Emphasis was placed on evaluating geometric orientation of constituents, use of elastomeric film in place of high modulus films, and the use of flying thread loom bias reinforcement of Kevlar yarns. Whereas, the performance of the Kevlar laminates was severely degraded by crease effects, significant gains in overall performance factors were shown for the coated Kevlar materials.

Reuter, L. L.↗
NASA NTRS1976

On tenuous plasmas, fireballs, and boundary layers in the earth's magnetotail

The plasma instrumentation (the Lepedea) and the magnetometer aboard IMP 8 performed correlative measurements of magnetic fields and plasmas within the geomagnetic tail at geocentric radial distances of about 23-46 R-E during March-October 1974. The hot tenuous plasmas within the plasma sheet were found to be in a state of almost continuous flow and were threaded with northward, or closed geomagnetic lines. The satellite encountered a region of acceleration in the magnetotail, the 'fireball' which exhibits strong jetting of plasmas in excess of 1000 km/s, proton temperatures of about 10 to the 7th K, disordered magnetic fields, southward magnetic fields during tailward jetting of plasmas, and northward magnetic fields for fast plasma flows toward earth. In addition, the magnetosheath plasmas within the boundary layers which are contiguous to the plasma sheet display evidence of plasma heating, great changes in bulk flow velocities, and acceleration of energetic electrons with an energy of greater than 45 keV.

Frank, L. A.↗
NASA NTRS1977

A CW ultrasonic bolt-strain monitor

There exists a need for a relatively inexpensive system for measuring strain in bolts. The torque wrench is one technique for straining bolts which has been widely applied. Unfortunately, friction in the bolt threads and between the nut and the work tend to make such a simple system inaccurate. In practice, a torque wrench is unacceptable for many situations where strain is critical. In this article, an ultrasonic technique is described which can indicate changes in bolt strain to better than one part in 10,000. The technique is based on the one-dimensional propagating-ultrasonic-wave model and uses a new ultrasonic instrument called a Reflection Oscillator Ultrasonic Spectrometer which is a closed-loop feedback marginal-oscillator system that frequency locks the device to the peak of a mechanical resonance in the bolt. The instrument indicates a shift in the bolt resonance frequency due to elongation and changes in velocity of sound due to strain. Data are presented comparing a standard torque wrench to the ultrasonic monitor for different measured stresses on the bolt as well as for different bolt conditions. The strain instrument can be used to monitor changing stresses, to measure material properties and may be applied as a strain gage or load cell.

Heyman, J. S.↗
NASA NTRS1977

Physics of an active region loop system

The structure of the active region loops is investigated by the study of a loop complex which undergoes a dramatic evacuation of most of the mass it contains. The need for continual energy deposition in loops is emphasized by the apparent cessation of energy input to the loops studied and their subsequent behavior. Estimates are made of the energy necessary to form and to maintain the loops, and of the relative importance of radiation and thermal conduction as energy loss mechanisms. Models based on the observed EUV emission are used to place limits on the size of loops seen in various lines and on the density and temperature structure. It is found that the cool cores of active region loops are likely to be no more than a few hundred kilometers in radius and that several such cool threads may be imbedded in a common hot outer sheath. The primary energy loss on a large scale is radiation with thermal conduction contributing to local disturbances. There is a tendency for the development of apparently unstable condensations or knots along the length of a loop.

Levine, R. H.↗
NASA NTRS1977

A structured surface for high performance evaporative heat transfer

An evaporative surface is described for heat pipes and other two-phase heat transfer applications that consists of a hybrid composition of V-grooves and capillary wicking. Characteristics of the surface include both a high heat transfer coefficient and high heat flux capability relative to conventional open faced screw thread surfaces. With a groove density of 12.6/cm and ammonia working fluid, heat transfer coefficients in the range of 1 to 2 W/sq cm K have been measured, along with maximum heat flux densities in excess of 20 W/sq cm. A peak heat transfer coefficient in excess of 2.3 W/sq cm K at 20 W/sq cm was measured with a 37.8/cm hybrid surface.

Saaski, E. W.↗
NASA NTRS1978

Nylon screws make inexpensive coil forms

Standard nylon screws act as coil form copper wire laid down in spiral thread. Completed coil may be bonded to printed-circuit board. However, it is impossible to tune coil by adjusting spacing between windings, technique sometimes used with air-core coils.

Aucoin, G.↗
NASA NTRS1978

Flicking-wire drag tensioner

Wire-drag system improves wire profile and applies consistent drag to wire. Wire drag is continuously adjustable from zero drag to tensile strength of wire. No-sag wire drag is easier to thread than former system and requires minimal downtime for cleaning and maintenance.

Dassele, M. A.↗
NASA NTRS1978

Ultrasonic extensometer measures bolt preload

Extensometer using ultrasonic pulse reflections to measure elongations in tightened belts and studs is much more accurate than conventional torque wrenches in application of specified preload to bolts and other threaded fasteners.

Daniels, C. M., Jr.↗
NASA NTRS1977

Study of a high performance evaporative heat transfer surface

An evaporative surface is described for heat pipes and other two-phase heat transfer applications that consists of a hybrid composition of V-grooves and capillary wicking. Characteristics of the surface include both a high heat transfer coefficient and high heat flux capability relative to conventional open-faced screw thread surfaces. With a groove density of 12.6 cm/1 and ammonia working fluid, heat transfer coefficients in the range of 1 to 2 W/sq cm have been measured along with maximum heat flux densities in excess of 20 W/sq cm. A peak heat transfer coefficient in excess of 2.3 W/sq cm was measured with a 37.8 cm/1 hybrid surface.

Saaski, E. W.↗
NASA NTRS1978

Rotary leveling base platform

A leveling apparatus for the precise adjustment of a scientific instrument is reported. A base member is provided having a hollow cylindrical shape. A table for supporting the instrument rests on the base and has a shaft portion extending below the table. The upper portion of the shaft fits tightly into the hollow portion of the base member whereas the lower portion of the shaft is machined to fit loosely. The lower portion of the shaft is provided with a groove. Adjusting screws are threaded through the hollow cylindrical portion and are adapted to enter the groove. By adjusting the screws, the lower portion of the shaft is moved in a vertical plane since the shaft is loosely fitted into the cylinder. The upper portion of the shaft which is tightly fitted into the upper end of the cylinder causes the cylinder to deform slightly providing a fulcrum point which allows the table to be leveled in response to the adjustment of the adjusting screws.

Delaplaine, R. W.↗
NASA NTRS1978

An investigation of heat pipe meniscus heat transfer

The use of grooved evaporator surfaces in heat pipes has increased in popularity in the past few years primarily due to the reproducibility achievable with grooved walls and the relatively low costs of the threading or extrusion processes involved in their production. The present study combines both analyses and experiments on square groove geometries, with special emphasis on overcoming the limitations of earlier analyses with finite-difference methods and groove-fillet hydrodynamic simplifications. The groove fillet, which has in previous analyses been assumed constant in radius of curvature, is permitted to change in thickness and curvature consistent with hydrodynamics and heat loss from the groove. A model is developed for accurate determination of the effect of constriction resistance on groove performance. The grooved-surface tests to be conducted are briefly described which will provide data under closely controlled operation to allow comparison and verification of the analyses.

Saaski, E. W.↗
NASA NTRS1978

Disk accretion by magnetic neutron stars

A model for disk accretion by a rotating magnetic neutron star is proposed which includes a detailed description of matter flow in the transition region between the disk and the magnetosphere. It is shown that the disk plasma cannot be completely screened from the stellar magnetic field and that the resulting magnetic coupling between the star and the disk exerts a significant torque on the star. On the assumption that the distortion of the residual stellar field lines threading the disk is limited by reconnection, the total accretion torque on the star is calculated. The calculated torque gives period changes in agreement with those observed in the pulsating X-ray sources and provides a natural explanation of why a fast rotator like Her X-1 has a spin-up rate much below the conventional estimate for slow rotators. It is shown that for such fast rotators, fluctuations in the mass-accretion rate can produce fluctuations in the accretion torque about 100 times larger. For sufficiently fast rotators or, equivalently, for sufficiently low accretion rates, the star experiences a braking torque even while accretion continues and without any mass ejection from its vicinity.

Ghosh, P.↗