Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “PENETRATION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Diurnal modulation of the quiet time penetrating electron flux

Three sounding rocket measurements of energetic electron precipitation in the 65 to 80 km altitude range above Siple Station, Antarctica suggest a possible diurnal modulation of the precipitation. Flights made on January 10 and 11, 1981, to investigate this possibility showed that no electrons were present after local noon, while a significant flux of penetrating electrons was observed the following day near local dawn, even though the level of magnetic activity was higher during the postnoon flight. A prevous flight from Siple Station also observed a large flux of penetrating electrons near local dawn. Calculations of electron drift trajectories in a model magnetic field indicate that moderate values of the convection electric field could cause significant local time variations in the penetrating electron flux at the western edge of the South Atlantic anomaly. These calculations indicate that Siple Station is shadowed by eastern Siberia when it is at local noon, but not when it is at local dawn.

Sheldon, W. R.↗
NASA NTRS1986

The flight and impact dispersion of the Comet Nucleus Penetrator - A six-degree-of-freedom simulation

The flight dynamics of a Penetrator probe which, as part of a Comet Rendezvous and Asteroid Flyby mission will impact a known periodic comet, possibly Hempel 2, and penetrate beneath the surface to obtain measurements, is discussed. The mission is described, including the penetrator-separation dynamics, the dynamics during initial coast and rocket thrust phase, and the final coast to impact. The effects on the results that may be caused by the comet nucleus gravity field variations, uncertainty in the spacecraft state vector, the spacecraft pointing accuracy, initial separation errors, and rocket motor thrust errors are examined.

Mascy, A. C.↗
NASA NTRS1987

Space station integrated wall design and penetration damage control. Task 4: Impact detection/location system

A program to develop a methodology is documented for detecting and locating meteoroid and debris impacts and penetrations of a wall configuration currently specified for use on space station. Testing consisted of penetrating and non-penetrating hypervelocity impacts on single and dual plate test configurations, including a prototype 1.22 m x 2.44 m x 3.56 mm (4 ft x 8 ft x 0.140 in) aluminum waffle grid backwall with multilayer insulation and a 0.063-in shield. Acoustic data were gathered with transducers and associated data acquisition systems and stored for later analysis with a multichannel digitizer. Preliminary analysis of test data included sensor evaluation, impact repeatability, first waveform arrival, and Fourier spectral analysis.

Nelson, J. M.↗
NASA NTRS1986

Penetration of sunlight into a canopy - Explicit models based on vertical and horizontal leaf projections

The projections of leaf areas onto a horizontal plane and onto a vertical plane are examined for their utility in characterizing canopies for sunlight penetration (direct beam only) models. These projections exactly specify the penetration if the projections on the principal plane of the normals to the top surfaces of the leaves are in the same quadrant as the sun. Inferring the total leaf area from these projections (and therefore the penetration as a function of the total leaf area) is possible only with a large uncertainty (up to + or - 32 percent) because the projections are a specific measure of the total leaf area only if the leaf angle distribution is known. It is expected that this uncertainty could be reduced to more acceptable levels by making an approximate assessment of whether the zenith angle distribution is that of an extremophile canopy.

Otterman, J.↗
NASA NTRS1986

Study of Comet Nucleus Gamma-Ray Spectrometer Penetration System

A penetrator system has been suggested as an approach for making in situ measurements of the composition and physical properties of the nucleus of a comet. This study has examined in detail the feasibility of implementing the penetrator concept. The penetrator system and mission designs have been developed and iterated in sufficient detail to provide a high level of confidence that the concept can be implemented within the constraints of the Mariner Mark 2 spacecraft.

Adams, G. L.↗
NASA NTRS1988

Near-nucleus trajectory design for Comet Penetrator-Lander data relay

A Comet Penetrator-Lander is included in the payload of the Comet Rendezvous Asteroid Flyby spacecraft; it will be deployed from an orbit about the comet nucleus and will implant itself in the nucleus at a pre-selected site. Throughout the following 9 days, the orbiting spacecraft must be in position to receive transmissions from the Penetrator-Lander at specified intervals. Using conic orbits and a simplified model of the nucleus, several types of trajectories have been identified which will allow the data relay requirements to be met. These are sensitive to the mass and rotational properties of the comet nucleus and to the latitude of the Penetrator-Lander impact site; no single orbital strategy can cover the entire range of possibilities. Frequent spacecraft maneuvers would provide more flexibility, but would result in a much more complicated mission scenario. More accurate modeling of the comet nucleus and the orbiter trajectories will refine the relay orbit options presented here.

Stetson, Douglas↗
NASA NTRS1991

Monitoring Weld Penetration Via Gas Pressure

Welding monitor uses pressure on back side of weldment to monitor penetration of weld. Sudden drop on pressure chart means weld pool has fully penetrated; sudden rise means pool no longer extends through joint. Devised to ensure full penetration along full lengths of weld joints, when direct observation of back sides by visual inspection, x rays, or fiber optics not possible. Used in initial development of welding parameters or during production as safeguard.

Coby, J. Ben, Jr.↗
NASA NTRS1991

A simulation study of impulsive penetration of solar wind irregularities into the magnetosphere at the dayside magnetopause

The impulsive penetration processes that occur when a plasma irregularity in the magnetosheath, modeled as a field-aligned filament, impinges on the dayside magnetopause, are investigated via a 2D magnetohydrodynamic code. It is found that, when the magnetic fields of the magnetosheath and magnetosphere are parallel or antiparallel, even plasma filaments with small initial velocities can eventually penetrate through the magnetopause and enter the magnetosphere. If the magnetic fields are not aligned, penetration will occur only if the initial kinetic energy density of the plasma filament is more than 50 times larger than the magnetic energy density due to the transverse component of the magnetic field.

Ma, Z. W.↗
NASA NTRS1990

Parsec-Scale Penetration of UV into Molecular Clouds: CII 158 Micron Mapping of W3, NGC 1977, and NGC 2023

The spatial distribution of the 158 microns CII fine structure line in the galactic sources W3, NGC 1977, and NGC 2023 is mapped. The emission arises from warm (100 to 300 K), dense photodissociation regions at the surface of molecular gas. In all three sources, the emission extends over parsec scales or greater. For W3 and NGC 1977, where the UV source/molecular cloud geometry presents an edge on view of the variation of CII intensity into the molecular gas, two dimensional models of the CII emission which include the effects of gas clumping and scattering by dust on the transport of UV photons are constructed. The observed CII distribution and intensity is well modeled by a clumpy or filamentary distribution to the molecular gas, with a clump/interclump gas density ratio of 100 or more, which allows deep penetration of carbon ionizing UV photons into the clouds. The penetration of UV into clumped molecular clouds may also explain the extended far IR continuum emission from these sources. The total luminosity of CII emission from a clumpy molecular cloud with adjacent or embedded octave band stars can be as much as an order of magnitude higher than the CII luminosity of a uniform cloud. In addition, the extended penetration of UV into molecular clouds will affect the abundances of atomic and molecular species and increase the fractional ionization of interclump gas and UV illuminated clump surfaces.

Howe, J. E.↗
NASA NTRS1991

Assessment of surface penetration with polarimetric radar

An airborne P-, L-, and C-band polarimetric radar dataset acquired over the Atchafalaya Bay study site was used to assess its surface penetration capabilities. The dataset was decompressed and reformatted to form a three-wavelength and three-polarization nine-channel dataset. All nine channels were filtered for speckle noise removal, using the 7-by-7 local-statistics moving-window filtering. Significant smoothing of data was obtained so that the data can be classified using the SRCH and M234 ELAS programs. Preliminary assessment of the PLC images indicated that the radar waves penetrated muddy water. Therefore the radar can measure the water depth and can be used to map the submerged sediments. A statistical analysis of the digital data provided insight on the depth of muddy water penetration.

Wu, Shih-Tseng↗
NASA NTRS1992

Space Debris Surfaces - Probability of no penetration versus impact velocity and obliquity

A collection of computer codes called Space Debris Surfaces (SD-SURF), have been developed to assist in the design and analysis of space debris protection systems. An SD-SURF analysis will show which obliquities and velocities are most likely to cause a penetration to help the analyst select a shield design best suited to the predominant penetration mechanism. Examples of the interaction between space vehicle geometry, the space debris environment, and the penetration and critical damage ballistic limit surfaces of the shield under consideration are presented.

Elfer, N.↗
NASA NTRS1991

Lunar regolith penetrators and cutters

An apparatus was designed and built for conducting simulation experiments on cutting tool penetration in the centrifuge. This equipment is mounted on the laminar container which is used for the regolith densification study, so that the end product of the latter, i.e., a regolith bed with the proper density profile, can be used directly for the penetration tests. In this apparatus, an etching tool is suspended through a pulley system by the action of a double acting air cylinder. By adjusting the air pressure acting on each side of the cylinder, the net downward force acting on the tool can be controlled. The penetration of the tool is measured by an LVDT. This apparatus was proof-tested in the centrifuge and is ready for use in conjunction with the regolith densification experiments.

Barnes, Frank↗
NASA NTRS1993

Hypervelocity particle penetration in multi-layered thermal blankets

Micrometeoroid and related hypervelocity particle impacts into 0.04-sq m samples cut from Scheldahl G411500 thermal blankets (STB) covering trays D05 and D07 in the NASA-LDEF satellite are characterized in detail. These impacts usually produced unique penetration features that generally consist of a delamination zone extending tens of penetration-hole diameters, separating the Teflon layer from the silver/Inconel film and the paint backing layers. When viewed from the space-facing side, the penetration holes are usually surrounded by rings or concentric halos within the delamination zone and radial cracks extending from the ejecta-rim surrounding the hole to the edge of the delamination zone. The phenomena responsible for the formation of these features are examined.

Liu, Jean↗
NASA NTRS1931

The Effect of Injection-Valve Opening Pressure on Spray-Tip Penetration

The effect of various injection-valve opening pressures on the spray-tip penetration was determined for several injection pressure. A common-rail fuel injection system was used. For a given injection pressure a maximum rate of penetration was obtained with an injection-valve opening pressure equal to the injection pressure. As the excess of the injection pressure over the injection-valve opening pressure was increased for a given injection pressure, the effect of the injection-valve opening pressure on the spray-tip penetration was increased.

Rothrock, A M↗
NASA NTRS1948

Investigation of the Penetration on an Air Jet Directed Perpendicularly to an Air Stream

An experimental investigation was conducted to determine the penetration of a circular air Jet directed perpendicularly to an air stream as a function of Jet density, Jet velocity, air-stream density, air-stream velocity, Jet diameter, and distance downstream from the Jet. The penetration was determined for nearly constant values of air-stream density at two tunnel velocities, four Jet diameters, four positions downstream of the Jet, and for a large range of Jet velocities and densities. An equation for the penetration was obtained in terms of the Jet diameter, the distance downstream from the jet, and the ratios of Jet and air-stream velocities and densities.

JETS↗
NASA NTRS1993

Impact penetration experiments in teflon targets of variable thickness

Approximately 20.4 sq m of Teflon thermal blankets on the nonspinning Long Duration Exposure Facility (LDEF) were exposed to the orbital debris and micrometeoroid environment in low-Earth orbit (LEO) for approximately 5.7 years. Each blanket consisted of an outer layer (approximately 125 micron thick) of FEP Teflon that was backed by a vapor-deposited metal mirror (Inconel; less than 1 micron thick). The inner surface consisted of organic binders and Chemglaze thermal protective paint (approximately 50 micron thick) resulting in a somewhat variable, total blanket thickness of approximately 180 to 200 microns. There was at least one of these blankets, each exposing approximately 1.2 sq m of surface area, on nine of LDEF's 12 principal pointing directions, the exceptions being Rows 3, 9, and 12. As a consequence, these blankets represent a significant opportunity for micrometeoroid and debris studies, in general, and specifically they provide an opportunity to address those issues that require information about pointing direction (i.e., spatial density of impact events as a function of instrument orientation). During deintegration of the LDEF spacecraft at KSC, all penetration holes greater than or equal to 300 micron in diameter were documented and were recently synthesized in terms of spatial density as a function of LDEF viewing direction by. The present report describes ongoing cratering and penetration experiments in pure Teflon targets, which are intended to establish the relationships between crater or penetration-hole diameters and the associated projectile dimensions at laboratory velocities (i.e., 6 km/s). The ultimate objective of these efforts is to extract reliable mass-frequencies and associated fluxes of hypervelocity particles in LEO.

Hoerz, F.↗
NASA NTRS1994

The effect of aircraft speed on the penetration of sonic boom noise into a flat ocean

As U.S. aircraft manufacturers now have focused their HSCT efforts on overwater supersonic flight, a great deal more must be known about sonic booms propagating overwater and interacting with the ocean. For example, it is thought that atmospheric turbulence effects are often much less severe over water than over land. Another important aspect of the overwater flight problems is the penetration of the sonic boom noise into the ocean, where there could be an environmental impact on sea life. This talk will present a brief review on the penetration of sonic boom noise into a large body of water with a flat surface. It has been determined recently that faster supersonic speeds imply greater penetration of sonic boom noise into the ocean. The new theory is derived from the original Sawyers paper and from the knowledge that for level flight a boom's duration is proportional to the quantity M/(M(exp 2)-1)(exp 3/8) where M is the Mach number. It is found that for depths of 10 m or less, the peak SPL varies less than 6 dB over a wide range of M. For greater depths, 100 m for example, increased Mach numbers may increase the SPL by 15 dB or more.

Sparrow, Victor W.↗
NASA NTRS1995

Penetration rates over 30 years in the space age

Experimental data from spacecraft providing impact penetration rates and cratering for metallic targets is reviewed. Data includes NASA Explorers 16 and 23 and the Pegasus series, the second US-UK satellite Ariel 2, Space Shuttle STS-3 (MFE), recovered surfaces on Solar Max Satellite, The Long Duration Exposure Facility (LDEF) and EuReCa TiCCE. Factors concerning exposure to the environment are considered and, especially, material properties which affect the penetration resistance. Reference to a common material, Aluminum alloy 2024-T3, is effected and the data then compared to define firstly an average impact flux over the period. The data is examined, in the context of possible satellite and space debris growth rates, to determine the constancy of the flux. This also provides strong constraints on the current space debris component. It is found that the impact data are consistent with domination by natural meteoroid sources. Growth rates are not evident within the period 1980-1990 and Eureca TiCCE fluxes in 1993, for particles penetrating foils of around 10 microns thickness, supports the constancy of the flux. At larger dimensions the 1993 Eureca TiCCE fluxes show an 8-fold increase but this is considered not inconsistent with the selective exposure to meteoroid streams of a satellite stabilized in heliocentric co-ordinates for an 11 month period.

Mcdonnell, J. A. M.↗