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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 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Status of the Electroforming Shield Design (ESD) project

The utilization of a digital computer to augment electrodeposition/electroforming processes in which nonconducting shielding controls local cathodic current distribution is reported. The primary underlying philosophy of the physics of electrodeposition was presented. The technical approach taken to analytically simulate electrolytic tank variables was also included. A FORTRAN computer program has been developed and implemented. The program utilized finite element techniques and electrostatic theory to simulate electropotential fields and ionic transport.

Fletcher, R. E.↗
NASA NTRS1977

Arc heater code validation tests of heat shield materials

Results are reported for tests of candidate heat-shield materials for outer-planet entry probes, which were conducted in two different arc-heater facilities at heating rates below those predicted for entry. One facility supplied a combined radiative-convective heating environment in air while the other provided a hydrogen/helium environment for convective heating only. Both 'infinite-slab' and 'finite-slab' models consisting of various carbon phenolic (CP) and fused silica (FS) materials were tested. The test results obtained are expressed in terms of ablation rates and surface as well as in-depth temperature variations with time for the air environment and in terms of normalized ablation rate as a function of temperature for the H/He environment. The measured values are compared with calculations based on a charring material thermal response and ablation code. For the CP models, good agreement between predicted and measured mass-loss rates is noted, surface temperatures in air are predicted within 18%, and in-depth temperature predictions are shown to be conservative in comparison with measured values. For the FS models, discrepancies are found between the predicted and measured mass-loss rates and surface temperatures.

Kesselring, J. P.↗
NASA NTRS1976

Shield volcanism and lithospheric structure beneath the Tharsis plateau, Mars

The heights of four great shield volcanoes, when interpreted as reflecting the local hydrostatic head on a common source of upwelling magma, provide significant constraints on models of lithospheric structure beneath the Tharsis plateau. If Bouguer gravity anomalies are modeled in terms of a variable thickness crust, and a two-component (crust/mantle) earth-like structure is assumed for the Martian lithosphere, the derived model lithosphere beneath the Tharsis plateau has the following properties: (1) the upper low-density 'crustal' component is thickened beneath the Tharsis plateau; (2) the lower high-density 'mantle' component is thinned beneath the Tharsis plateau; and (3) there is a net gradient on the base of the Martian lithosphere directed downward away from beneath the summit of the Tharsis plateau. A long history of magmatic intrusion is hypothesized to have been the cause of the updoming of the Tharsis plateau and the maintenance of the plateau in a state of only partial compensation.

Blasius, K. R.↗
NASA NTRS1977

Shielding effects in Norton County and other aubrites

Al-26 (dpm/kg) and/or He, Ne, and Ar have been measured in samples of the Norton County meteorite from three different depths. The gas contents yield a shielding-corrected age of 75.8 + or - 5.7 million years. The ratio of atomic production rates P(Al-26)/P(Ne-21) is 0.22 + or - 0.02. He-3, Ne-21, and Al-26 increase with decreasing Ne-22/Ne-21 at nearly the same rates as they do in the smaller Keyes chondrite. Al-26 contents were measured in Bustee, Khor Temiki, Pesyanoe, and Shallowater meteorites. The ratio of observed to predicted Al-26 content correlates with Ne-22/Ne-21, and comparison with the corresponding chondrite correlation indicates that such aubrites as Malakal may have experienced an unusually high flux of cosmic rays.

Herzog, G. F.↗
NASA NTRS1979

Splicing shielded cables

Simple repair technique retains cable characteristic impedance. Shielded-Cable Splicing Technique retains cable characteristic impedance. Procedure involves splicing inner conductors in staggered pattern, installing jumper braid by heat-shrinking two solder sleeves, and placing insulation sleeve over repaired section and heat-shrinking it. Two possible insulation materials are modified polyvinylidene fluoride and polytetrafluoroethylene.

Lind, W. P.↗
NASA NTRS1978

The design of reactive shielded magnet clutches

The design of reactive shielded magnet clutches is considered along with their schematics, design formulas and characteristics of clutches in general. The design method suggested makes it possible to reduce calculation errors to 10%.

Gertsov, S. M.↗
NASA NTRS1977

Effect of experiments on the density distribution in a molecular shield

A steady-state, collisionless flow analysis has been made of the density distribution within a hemisphere-disk system due to independent, uniformly distributed internal gas sources. The model may be used to estimate the density within a molecular shield, deployed from the Shuttle Orbiter, which contains internal experiments having a prescribed gas source. Contour plots of the density distribution within the system are presented for disk-to-hemisphere radius ratios of 0.1, 0.3, 0.5, and 0.7, and for disk-to-hemisphere surface emission flux density ratios of 0.01, 1, and 100. The hemisphere-disk system is compared to the empty hemisphere and it is found that if the disk emission flux density is the same as the hemisphere and the disk radius is not greater than one-third of the hemisphere radius, the increase in density at the center of the hemisphere-disk system is less than 50%.

Hueser, J. E.↗
NASA NTRS1980

Interleaved shielding for cables

Interleaved wrapping of metal foil shielding on power cables gives more effective electromagnetic interference protection without increasing amount of material or weight.

Read, G. R.↗
NASA NTRS1979

Space Shuttle Orbiter AFT heat shield seal

The evolution of the orbiter aft heat shield seal (AHSS) design, which involved advancing mechanical seal technology in severe thermal environment is discussed. The baseline design, various improvements for engine access, and technical problem solution are presented. It is a structure and mechanism at the three main propulsion system (MPS) engine interfaces to the aft compartment structure. Access to each MPS engine requires disassembly and removal of the AHSS. Each AHSS accommodates the engine movement, is exposed to an extremely high temperature environment, and is part of the venting control of the aft compartment.

Walkover, L. J.↗
NASA NTRS1979

Magnetic shielding of large high-power-satellite solar arrays using internal currents

Present concepts for solar power satellites involve dimensions up to tens of kilometers and operating internal currents up to hundreds of kiloamperes. A question addressed is whether the local magnetic fields generated by these strong currents during normal operation can shield the array against impacts by plasma ions and electrons (and from thruster plasmas) which can cause possible losses such as power leakage and surface erosion. One of several prototype concepts was modeled by a long narrow rectangular panel 2 km wide and 20 km long. The currents flow in a parallel across the narrow dimension (sheet current) and along the edge (wire currents). The wire currents accumulate from zero to 100 kiloamp and are the dominant sources. The magnetic field is approximated analytically. The equations of motion for charged particles in this magnetic field are analyzed. The ion and electron fluxes at points on the surface are represented analytically for monoenergetic distributions and are evaluated.

Parker, L. W.↗
NASA NTRS1981

Safety shield for vacuum/pressure chamber viewing port

Observers are protected from flying debris resulting from a failure of a vacuum or pressure chamber viewing port following an implosion or explosion by an optically clear shatter resistant safety shield which spaced apart from the viewing port on the outer surface of the chamber.

Shimansky, R. A.↗
NASA NTRS1981

Preliminary design study of solar probe heat shields

The requirements, constraints, design guidelines, and expected performances of heat-shield systems for a solar probe are analyzed. A multiple-stage, asymmetric, right-angle radiation cascade configuration is used as the basis for comparison. Output-to-input radiative flux ratios are first calculated for a system employing gray surfaces. Assuming that the temperature of the inner surface of the payload bus is allowed to reach 400 K, it is shown that four- and five-stage cascade systems employing graphite can approach, respectively, to within about 5.5 and 4 solar radii of the sun. The systems using slip-cast silica and tungsten are then analyzed accounting for the degradation of surface-optical performance caused by the solar wind. It is shown that two- and three-stage silica-tungsten systems can approach, respectively, to within 4 and 3 solar radii of the sun.

Park, C.↗
NASA NTRS1982

An investigation of MAGSAT and complementary data emphasizing precambrian shields and adjacent areas of West Africa and South America

The problems associated with the use of an interactive magnetic modeling program are reported and a publication summarizing the MAGSAT anomaly results for Africa and the possible tectonic associations of these anomalies is provided. An overview of the MAGSAT scalar anomaly map for Africa suggested a correlation of MAGSAT anomalies with major crustal blocks of uplift or depression and different degrees of regional metamorphism. The strongest MAGSAT anomalies in Africa are closely correlated spatially with major tectonic features. Results indicate that the Bangui anomaly may be caused by a central old Precambrian shield, flanked to the north and south by two relatively young sedimentary basins.

Hastings, D. A.↗
NASA NTRS1982

Trajectories of solid particles spalled from a carbonaceous heat shield

Trajectories are calculated of solid carbon particles that spall from a carbonaceous heat shield and travel through a given flow field. The mathematical model takes into account mass, momentum, and energy conservation during evaporation of the particles in an effort to understand spallation phenomena and their consequences in a physical way. The solution technique is applied to available Galileo Probe flow field solutions. Plots of trajectories and other particle parameters are presented for a range of initial particle sizes and velocities. It is shown that a significant amount of gaseous carbon is deposited in the inviscid region and ahead of the bow shock as well as in the ablation layer.

Davies, C. B.↗
NASA NTRS1982

Late-stage summit activity of Martian shield volcanoes

The preservation of morphologically fresh lava flows which pre-date the most recent episodes of caldera collapse at the summits of Ascraeus, Arsia and Olympus Montes indicates that explosive eruptions were not associated with this stage of Tharsis shield volcanism. The existence of resurfaced floor segments, complex wrinkle ridges, and lava terraces within the summit craters suggests that lava lakes comprised the dominant form of the intra-caldera activity. Multiple collapse episodes on Ascraeus and Olympus Montes are indicated by the nested summit craters. The most plausible cause of caldera collapse appears to be large-scale sub-terminal effusive activity, which is corroborated by the previously recognized existence of large lava flows on the flanks of these volcanoes. Due to the implied sequence of large-scale explosive (silicic) volcanism followed by effusive (basaltic) activity, it appears highly unlikely that ignimbrites or other forms of pyroclastic flows (previously proposed as possible deposits within the Olympus Mons aureole material) were ever erupted from the Tharsis Montes.

Mouginis-Mark, P. J.↗
NASA NTRS1984

Shield Boosts Silicon-Growth Rate

Radiation shield permits faster growth--by 20 percent--of singlecrystal silicon from molten silicon by producting sharper thermal gradients near growth front.

Lane, R. L.↗
NASA NTRS1982

Analysis of the characteristics appearing in LANDSAT multispectral images in the geological structural mapping of the midwestern portion of the Rio Grande do Sul shield

The central-western part of Rio Grande do Sul Shield was geologically mapped to test the use of MSS-LANDSAT data in the study of mineralized regions. Visual interpretation of the images a the scale of 1:500,000 consisted, in the identification and analysis of the different tonal and textural patterns in each spectral band. After the structural geologic mapping of the area, using visual interpretation techniques, the statistical data obtained were evaluated, specially data concerning size and direction of fractures. The IMAGE-100 system was used to enlarge and enhance certain imagery. The LANDSAT MSS data offer several advantages over conventional white and black aerial photographs for geological studies. Its multispectral characteristic (band 6 and false color composition of bands 4, 5 and 7 were best suitable for the study). Coverage of a large imaging area of about 35,000 sq km, giving a synoptical view, is very useful for perceiving the regional geological setting.

Parada, N. D. J.↗