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1

Preliminary earth berm shielding calculations for the accelerator production of tritium 1700-MeV accelerator  

SciTech Connect

The authors have performed calculations using the LAHET Code System (LCS) to obtain an estimation of the amount of earth berm shielding that will be required for the 1700-MeV proton accelerator proposed for the Accelerator Production of Tritium (APT) Project. A source scenario of 10 nA/m beam loss along the beam line was used to calculate the dose values above a 6-m earth berm from high-energy neutrons, low-energy neutrons, and photons. LAHET, a Monte Carlo based particle transport code, was used to transport a 1700-MeV protons from the beam along a divergence path of 1{degree} from the original beam direction and impacting representative beampipe material along a 300-m beamline. LAHET was then used to track all high-energy neutron production until the neutrons either escape the berm shield, or scatter down in energy to 20 MeV, where their parameters were then written to a source file for MCNP. Photon production data was also written to a source file used by MCNP. MCNP transported all neutrons and photons from the LAHET source file until they (1) were absorbed, scattered down to an energy cutoff, or (2) escaped from the system. Doses were calculated from surface flux tallies obtained from LAHET and MCNP. These doses were then compared to earlier Moyer model calculations.

Court, J.D.; Pitcher, E.J.; Ferguson, P.D.; Russell, G.J.; Patton, B.W.

1998-07-01

2

SOUTHWEST REAR AND SOUTHEAST SIDE. Protective berm at left shields ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

SOUTHWEST REAR AND SOUTHEAST SIDE. Protective berm at left shields Air Supply building from launch pad - Edwards Air Force Base, South Base Sled Track, Air Supply Building for Building No. 0545, South of Sled Track at east end, Lancaster, Los Angeles County, CA

3

Jupiter: Earth's Shield  

NSDL National Science Digital Library

More than 155 planets have been found outside of our solar system since the first discovery in 1995, mostly massive Jupiter-like planets in orbits close to their suns. Now, to find an Earth-like planet, scientists are looking for a planetary setup that is similar to our own, in which a Jupiter-like planet lies a good distance away from its sun. This video segment explores how the arrangement of planets in our solar system may have affected the development of life on Earth and describes how researchers are searching for the right planetary setup. The segment is two minutes one second in length. A background essay and list of discussion questions are also provided.

2011-02-01

4

SHIELD: a comprehensive earth-protection architecture  

Microsoft Academic Search

The greatest natural threat to the long-term survivability of mankind is an asteroid or comet impact with the Earth. SHIELD is an architectural concept for a comprehensive Earth defense system designed to discover, catalog, calculate orbits of near-Earth objects, and to deflect potential impactors. SHIELD consists of Sentries, Soldiers, and an Earth Control Center. Sentries are spacecraft designed to search

R. E. Gold

2001-01-01

5

THEMIS discovers holes in Earth's solar shield  

NASA Video Gallery

This animation shows the latest findings from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission. Earth's magnetic field; which shields our planet from severe ...

6

Earth pressure balance control for EPB shield  

Microsoft Academic Search

This paper mainly deals with the critical technology of earth pressure balance (EPB) control in shield tunneling. On the assumption\\u000a that the conditioned soil in the working chamber of the shield is plasticized, a theoretical principle for EPB control is\\u000a proposed. Dynamic equilibrium of intake volume and discharge volume generated by thrust and discharge is modeled theoretically\\u000a to simulate the

HuaYong Yang; Hu Shi; GuoFang Gong; GuoLiang Hu

2009-01-01

7

SHIELD: a comprehensive earth-protection architecture  

NASA Astrophysics Data System (ADS)

The greatest natural threat to the long-term survivability of mankind is an asteroid or comet impact with the Earth. SHIELD is an architectural concept for a comprehensive Earth defense system designed to discover, catalog, calculate orbits of near-Earth objects, and to deflect potential impactors. SHIELD consists of Sentries, Soldiers, and an Earth Control Center. Sentries are spacecraft designed to search and locate NEOs of all types. Sentries maximize the lead-time for a potential impact, which simplifies the task of the Soldiers to deflect the object. Sentry spacecraft determine the orbit of each object, and compare it with the onboard database of known NEOs. The results are kept in a distributed space-Earth database. Soldier spacecraft deflect or disperse the potential impactor. Several mitigation methods have been compared by their specific impulse. Each technique requires some development to be feasible. These techniques can be categorized into "rendezvous" in which the Soldier physically lands on the NEO and "intercept". The required number of Soldiers and their locations has been examined. SHIELD has clearly shown that an Earth-protection system is practical and that a full system could be built within a few years. Indeed, very capable Sentries can be launched today.

Gold, R. E.

2001-01-01

8

Shielding distribution for anisotropic radiation in low earth orbit  

Microsoft Academic Search

The highly directional nature of radiation encountered in low earth orbit (LEO) can be a basis for distributing mass for spacecraft radiation shielding. Trapped (Van Allen) radiation at low altitudes is concentrated within a plane perpendicular to the local geometric field lines. Trapped high-energy protons (which penetrate the relatively thin shielding required for electrons) have a pronounced east-west asymmetry at

M. W. Henley

1986-01-01

9

The Magnetosphere - Earth Raises its Shields  

NSDL National Science Digital Library

A view of a computer-generated model of the Earth's magnetosphere. Semi-transparent surfaces represent particle density (red is high, blue is low) and silvery tubes represent the magnetic field lines. In this particular model, the solar wind has an ambient density of 8.35 particles-cm^3. The isosurfaces are then red (>17 particles-cm^3), yellow (>12 particles-cm^3), green (>8.6 particles-cm^3) and blue (<1.0 particle-cm^3).

Bridgman, Tom; Mitchell, Horace; Sokolowsky, Eric; Spicer, Dan

2002-02-28

10

Reconnection: Solar Wind Breaches the Earths Magnetic Shield  

NSDL National Science Digital Library

The Far Ultraviolet camera abord the IMAGE spacecraft captured this view of a proton aurora (the bright spot near the center of the view) as well as the ring of the electron aurora. The protons for this aurora came from the incoming solar wind. The made it though the Earths magnetic shield in a magnetic reconnection event higher in the magnetosphere which was detected by the Cluster satellite. Note: A corner appears in the data in the beginning as the IMAGE spacecraft moves into a position where it can view the entire north polar region.

Bridgman, Tom; Frey, Harald; Phan, Tai

2003-12-04

11

Numerical Simulation of Earth Pressure on Head Chamber of Shield Machine with FEM  

NASA Astrophysics Data System (ADS)

Model parameters of conditioned soils in head chamber of shield machine are determined based on tree-axial compression tests in laboratory. The loads acting on tunneling face are estimated according to static earth pressure principle. Based on Duncan-Chang nonlinear elastic constitutive model, the earth pressures on head chamber of shield machine are simulated in different aperture ratio cases for rotating cutterhead of shield machine. Relationship between pressure transportation factor and aperture ratio of shield machine is proposed by using aggression analysis.

Li, Shouju; Kang, Chengang; Sun, Wei; Shangguan, Zichang

2010-05-01

12

How to protect the Earth from Global warming by means of Sunlight Shield Equipments  

NASA Astrophysics Data System (ADS)

The Earth is getting warmer because excess carbon dioxide of the Earth's atmosphere. Many studies are proceeding in the world in order to prevent global warming. Three methods are studied: (1) How to reduce carbon dioxide of the Earth's atmosphere. For example, more trees will be planted and carbon dioxide is changed to oxygen and carbon. (2) How to reduce carbon dioxide emission that human activity makes. (3) How to protect the Earth from global warming. The first or the second method has been studied, and they do not immediately protect the Earth from global warming. On the other hand the third method has an immediate effect. Sunlight shield effects of a cloud or tiny sulfur in the air have been studied. The author has proposed a sunlight shield equipment which is composed of a flat balloon. Balloon's surface has a mirror function. The sunlight shield equipment is set at the stratosphere and its surface reflects sunlight to the space. It is different temperature between daytime and night time, because the earth is heated by the sun during only daytime. Temperature of the Earth could be controlled by controlling an amount of a sunlight power which the earth receives from the sun. In other word, when many sunlight shield equipments are set and operated at the stratosphere, and an amount of sunlight, which the earth receives from the sun, could be controlled. For example, when an amount of the sunlight power, which the earth receives, decreases one percent, a mean value of the earth temperature deceases about one centigrade. In order to decrease one percent of a sunlight power which the earth receives, it is required that many sunlight shield equipments are distributively set and operated, and the gross area of many sunlight shield equipments is equal to 5,060,000 km squares. When a size of a sunlight shield equipment is equal to 5 km squares, about one million of sunlight shield equipments are necessary, and a large scale of cost is required. Therefore, an effective operation of sunlight shield equipments is desired. This paper clarifies how to operate effectively sunlight shield equipments in order to protect the Earth from global warming, and considers issues of the equipment operation.

Murakami, H.

2010-09-01

13

SPERTI Reactor Pit Building (PER605). Earth shielding protect adjacent Instrument ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

SPERT-I Reactor Pit Building (PER-605). Earth shielding protect adjacent Instrument Cell (PER-606). Security fencing surrounds complex, to which gate entry is provided next to Guard House (PER-607). Note gravel road leading to control area. Earth-covered conduit leads from instrument cell to terminal building out of view. Photographer: R.G. Larsen. Date: June 22, 1955. INEEL negative no. 55-1701 - Idaho National Engineering Laboratory, SPERT-I & Power Burst Facility Area, Scoville, Butte County, ID

14

III-V compound semiconductor film growth in low earth orbit on the wake shield facility  

Microsoft Academic Search

Gallium Arsenide (GaAs) films, both silicon doped and undoped, have been deposited by Molecular Beam Epitaxy (MBE) in Low Earth Orbit (LEO) in an ultra vacuum environment created by the Wake Shield Facility (WSF). The WSF is a 12 foot diameter stainless steel disk that sweeps out a volume of space thus creating an ultra vacuum in its wake. It

Charles Horton; Alex Ignatiev; Mark Sterling; Abdelhak Bensaoula; Alex Freundlich; Steven Pei; Ron Sega

1995-01-01

15

Using Combustion Synthesis to Reinforce Berms and Other Regolith Structures  

NASA Technical Reports Server (NTRS)

The Moonraker Excavator and other tools under development for use on the Moon, Mars, and asteroids will be employed to construct a number of civil engineering projects and to mine the soil. Mounds of loose soil will be subject to the local transport mechanisms plus artificial mechanisms such as blast effects from landers and erosion from surface vehicles. Some of these structures will require some permanence, with a minimum of maintenance and upkeep. Combustion Synthesis (CS) is a family of processes and techniques whereby chemistry is used to transform materials, often creating flame in a hard vacuum. CS can be used to stabilize civil engineering works such as berms, habitat shielding, ramps, pads, roadways, and the like. The method is to unroll thin sheets of CS fabric between layers of regolith and then fire the fabric, creating a continuous sheet of crusty material to be interposed among layers of loose regolith. The combination of low-energy processes, ISRU (in situ resource utilization) excavator, and CS fabrics, seems compelling as a general method for establishing structures of some permanence and utility, especially in the role of robotic missions as precursors to manned exploration and settlement. In robotic precursory missions, excavator/ mobility ensembles mine the Lunar surface, erect constructions of soil, and dispense sheets of CS fabrics that are covered with layers of soil, fired, and then again covered with layers of soil, iterating until the desired dimensions and forms are achieved. At the base of each berm, for example, is a shallow trench lined with CS fabric, fired and filled, mounded, and then covered and fired, iteratively to provide a footing against lateral shear. A larger trench is host to a habitat module, backfilled, covered with fabric, covered with soil, and fired. Covering the applied CS fabric with layers of soil before firing allows the resulting matrix to incorporate soil both above and below the fabric ply into the fused layer, developing a very irregular surface which, like sandpaper, can provide an anchor for loose soil. CS fabrics employ a coarse fiberglass weave that persists as reinforcement for the fired material. The fiberglass softens at a temperature that exceeds the combustion temperature by factors of two to three, and withstands the installation process. This type of structure should be more resistant to rocket blast effects from Lunar landers.

Rodriquez, Gary

2013-01-01

16

3. Earthen berm and water control structure used to regulate ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

3. Earthen berm and water control structure used to regulate water flow into adjacent cultivated area - Natomas Ditch System, Blue Ravine Segment, Juncture of Blue Ravine & Green Valley Roads, Folsom, Sacramento County, CA

17

17. View from Sterling Creek Marsh looking west, with berm ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

17. View from Sterling Creek Marsh looking west, with berm to the left and Henry Ford Mansion in the far background - Richmond Hill Plantation, Sterling Creek Marsh, East of Richmond Hill on Ford Neck Road, Richmond Hill, Bryan County, GA

18

FEATURE A. CONCRETE ANTIAIRCRAFT GUN POSITION, SHOWING CORAL RUBBLE BERM, ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

FEATURE A. CONCRETE ANTI-AIRCRAFT GUN POSITION, SHOWING CORAL RUBBLE BERM, VIEW FACING SOUTHEAST. - Naval Air Station Barbers Point, Battery-Anti-Aircraft Gun Position, South of Point Cruz Road & west of Coral Sea Road, Ewa, Honolulu County, HI

19

Ab initio study of NMR shielding of alkali earth metal ions in water complexes and magnetic moments of alkali earth metal nuclei  

NASA Astrophysics Data System (ADS)

Ab initio calculations of NMR shielding constants of alkali earth metal ions in the series of water clusters are presented. The shielding constants for systems modeling the structure of the solvation layer of these ions are determined by adding to the coupled cluster singles-and-doubles (CCSD) results the calculated relativistic corrections. The relative magnitude of the dynamical effects, estimated for a typical solvated ion from Car-Parrinello molecular dynamics, is very small. The computed shielding constants are used next to obtain new values of the nuclear magnetic dipole moments of alkali earth metal nuclei.

Antušek, Andrej; Rodziewicz, Pawel; Ke?ziera, Dariusz; Kaczmarek-Ke?ziera, Anna; Jaszu?ski, Micha?

2013-11-01

20

A captured asteroid : Our David's stone for shielding earth and providing the cheapest extraterrestrial material  

NASA Astrophysics Data System (ADS)

The issue of protecting the Earth against an asteroid impact is very popular and many concepts have been proposed to fulfil this objective. In this paper, we develop the idea of capturing a small size asteroid from an orbit close to Earth's in terms of energy and placing it into a loose Earth-bound orbit in order to use it as a shield by engineering its collision with any incoming, threatening body prior to its impact with the Earth. The operations for turning the captured asteroid into an efficient shield appear to be quicker, easier, cheaper and safer than an mission aimed at landing on an incoming impact-bound asteroid either for altering its trajectory or attempting to destroy it. The aim is an asteroid typically 20 40 m in diameter, too small to cause damage on Earth if an improper management leads to its crash, but big enough to destroy and deviate any incoming body if a collision is engineered with it preferably at more than one million km from Earth. Such a collision could be implemented within a 8 month time frame. Such an asteroid would also be a source of material such as liquid oxygen for exploratory missions. We show that the production of this material is much more efficient from an asteroid's surface than from the Moon's. As the celestial surface most accessible from Earth, a captured asteroid is also easier to engineer. Several thousands of tons of oxygen might become available sitting on the outer rim of Earth's gravity field. We examine the advantages and drawbacks of this concept and we propose a stepped approach for making it a reality within a foreseeable future. Key factors are first the detection of a candidate, whose small size make it difficult to spot, among a population of asteroids easy to reach from the Earth. We have identified such a potential candidate in 2000SG344 and describe the parameters of its capture. The second key point is how to deviate the candidate into an loose Earth bound orbit. Our preferred concept is to deposit a small robotic instrument aimed at throwing up matter gathered on the surface of the body with typical velocities of tens of meters per second. The robot would require a year and a few hundreds of watts continuously to alter the velocity of the asteroid in such a way as to inject it through an Earth Sun Lagrange point, and then to control a Lagrangian quasi-periodic orbit with a typical 6-month period. We conclude that such an enterprise is far from being unfeasible and that it can probably be conducted using today's systems and exploratory tools in a few years time frame.

Massonnet, Didier; Meyssignac, Benoît

2006-07-01

21

Evidence for the Snowball Earth hypothesis in the Arabian-Nubian Shield and the East African Orogen  

Microsoft Academic Search

Formation of the Arabian-Nubian Shield (ANS) and the East African Orogen (EAO) occurred between 870Ma and the end of the Precambrian (?542Ma). ANS crustal growth encompassed a time of dramatic climatic change, articulated as the Snowball Earth hypothesis (SEH). SEH identifies tremendous paleoclimatic oscillations during Neoproterozoic time. Earth’s climate shifted wildly, from times when much of our planet’s surface was

R. J. Stern; D. Avigad; N. R. Miller; M. Beyth

2006-01-01

22

Development of Multifunctional Radiation Shielding Materials for Long Duration Human Exploration Beyond the Low Earth Orbit  

NASA Technical Reports Server (NTRS)

One of the major challenges for long duration human exploration beyond the low Earth orbit and sustained human presence on planetary surfaces would be development of materials that would help minimize the radiation exposure to crew and equipment from the interplanetary radiation environment, This radiation environment consists primarily of a continuous flux of galactic cosmic rays (GCR) and transient but intense fluxes of solar energetic particles (SEP). The potential for biological damage by the relatively low percentage of high-energy heavy-ions in the GCR spectrum far outweigh that due to lighter particles because of their ionizing-power and the quality of the resulting biological damage. Although the SEP spectrum does not contain heavy ions and their energy range is much lower than that for GCRs, they however pose serious risks to astronaut health particularly in the event of a bad solar storm The primary purpose of this paper is to discuss our recent efforts in development and evaluation of materials for minimizing the hazards from the interplanetary radiation environment. Traditionally, addition of shielding materials to spacecrafts has invariably resulted in paying a penalty in terms of additional weight. It would therefore be of great benefit if materials could be developed not only with superior shielding effectiveness but also sufficient structural integrity. Such a multifunctional material could then be considered as an integral part of spacecraft structures. Any proposed radiation shielding material for use in outer space should be composed of nuclei that maximize the likelihood of projectile fragmentation while producing the minimum number of target fragments. A modeling based approach will be presented to show that composite materials using hydrogen-rich epoxy matrices reinforced with polyethylene fibers and/or fabrics could effectively meet this requirement. This paper will discuss the fabrication of such a material for a crewed vehicle. Ln addition, the capability of synthesizing radiation shielding materials for habitat structures primarily from Lunar or Martian in-situ resources will also be presented. Such an approach would significantly _reduce the cost associated with transportation of such materials and structures from earth. Results from radiation exposure measurements will be presented demonstrating the shielding effectiveness of the developed materials. Mechanical testing data will be discussed to illustrate that the specific mechanical properties of the developed composites are comparable to structural aluminum based alloys currently used for the space shuttle and space station.

Sen, S.; Bhattacharya, M.; Schofield, E.; Carranza, S.; O'Dell, S.

2007-01-01

23

Canmar's berm-supported SSDC drilling advances arctic technology  

SciTech Connect

This report describes design, installation and performance of the single steel drilling caisson (SSDC) on a subsea berm. It details key points learned from the $100-million project by Canadian Marine Drilling Ltd. installed in the Beaufort Sea. Unitized construction allows for permanent installation and hookup of the drilling rig package. Mobilization and demobilization is much simpler, resulting in quicker and safer operation than that required with a multi-caisson system. The high freeboard achieved with the SSDC unit gives much greater protection with respect to wave run-up and ice ride-up, resulting in significant operational improvements. The relatively low elevation of the submerged berm at 9 m below sea level results in improved berm stability and erosion resistance.

Hewitt, K.J.; Berzins, W.E.; Fitzpatrick, J.P.; Hogeboom, H.G.

1985-07-01

24

2. PROTECTIVE BERM SURROUNDING LAUNCH AREA AT EAST END OF ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. PROTECTIVE BERM SURROUNDING LAUNCH AREA AT EAST END OF TRACK. WATER PUMP STATION 0540 AT FAR RIGHT. Looking from northeast of Station "0". - Edwards Air Force Base, South Base Sled Track, Edwards Air Force Base, North of Avenue B, between 100th & 140th Streets East, Lancaster, Los Angeles County, CA

25

Radiation Protection Effectiveness of Polymeric Based Shielding Materials at Low Earth Orbit  

NASA Technical Reports Server (NTRS)

Correlations of limited ionizing radiation measurements onboard the Space Transportation System (STS; shuttle) and the International Space Station (ISS) with numerical simulations of charged particle transport through spacecraft structure have indicated that usage of hydrogen rich polymeric materials improves the radiation shielding performance of space structures as compared to the traditionally used aluminum alloys. We discuss herein the radiation shielding correlations between measurements on board STS-81 (Atlantis, 1997) using four polyethylene (PE) spheres of varying radii, and STS-89 (Endeavour, 1998) using aluminum alloy spheres; with numerical simulations of charged particle transport using the Langley Research Center (LaRC)-developed High charge (Z) and Energy TRaNsport (HZETRN) algorithm. In the simulations, the Galactic Cosmic Ray (GCR) component of the ionizing radiation environment at Low Earth Orbit (LEO) covering ions in the 1< or equals Z< or equals 28 range is represented by O'Neill's (2004) model. To compute the transmission coefficient for GCR ions at LEO, O'Neill's model is coupled with the angular dependent LaRC cutoff model. The trapped protons/electrons component of LEO environment is represented by a LaRC-developed time dependent procedure which couples the AP8min/AP8max, Deep River Neutron Monitor (DRNM) and F10.7 solar radio frequency measurements. The albedo neutron environment resulting from interaction of GCR ions with upper atmosphere is modeled through extrapolation of the Atmospheric Ionizing Radiation (AIR) measurements. With the validity of numerical simulations through correlation with PE and aluminum spheres measurements established, we further present results from the expansion of the simulations through the selection of high hydrogen content commercially available polymeric constituents such as PE foam core and Spectra fiber(Registered TradeMark) composite face sheet to assess their radiation shield properties as compared to generic PE.

Badavi, Francis F.; Stewart-Sloan, Charlotte R.; Wilson, John W.; Adams, Daniel O.

2008-01-01

26

Aerothermodynamic optimization of Earth entry blunt body heat shields for Lunar and Mars return  

NASA Astrophysics Data System (ADS)

A differential evolutionary algorithm has been executed to optimize the hypersonic aerodynamic and stagnation-point heat transfer performance of Earth entry heat shields for Lunar and Mars return manned missions with entry velocities of 11 and 12.5 km/s respectively. The aerothermodynamic performance of heat shield geometries with lift-to-drag ratios up to 1.0 is studied. Each considered heat shield geometry is composed of an axial profile tailored to fit a base cross section. Axial profiles consist of spherical segments, spherically blunted cones, and power laws. Heat shield cross sections include oblate and prolate ellipses, rounded-edge parallelograms, and blendings of the two. Aerothermodynamic models are based on modified Newtonian impact theory with semi-empirical correlations for convection and radiation. Multi-objective function optimization is performed to determine optimal trade-offs between performance parameters. Objective functions consist of minimizing heat load and heat flux and maximizing down range and cross range. Results indicate that skipping trajectories allow for vehicles with L/D = 0.3, 0.5, and 1.0 at lunar return flight conditions to produce maximum cross ranges of 950, 1500, and 3000 km respectively before Qs,tot increases dramatically. Maximum cross range increases by ˜20% with an increase in entry velocity from 11 to 12.5 km/s. Optimal configurations for all three lift-to-drag ratios produce down ranges up to approximately 26,000 km for both lunar and Mars return. Assuming a 10,000 kg mass and L/D = 0.27, the current Orion configuration is projected to experience a heat load of approximately 68 kJ/cm2 for Mars return flight conditions. For both L/D = 0.3 and 0.5, a 30% increase in entry vehicle mass from 10,000 kg produces a 20-30% increase in Qs,tot. For a given L/D, highly-eccentric heat shields do not produce greater cross range or down range. With a 5 g deceleration limit and L/D = 0.3, a highly oblate cross section with an eccentricity of 0.968 produces a 35% reduction in heat load over designs with zero eccentricity due to the eccentric heat shield's greater drag area that allows the vehicle to decelerate higher in the atmosphere. In this case, the heat shield's drag area is traded off with volumetric efficiency while fulfilling the given set of mission requirements. Additionally, the high radius-of-curvature of the spherical segment axial profile provides the best combination of heat transfer and aerodynamic performance for both entry velocities and a 5 g deceleration limit.

Johnson, Joshua E.

27

Significance of the Tambien Group (Tigrai, N. Ethiopia) for Snowball Earth events in the Arabian–Nubian Shield  

Microsoft Academic Search

Juvenile continental crust of the Arabian–Nubian Shield (ANS) formed within a Neoproterozoic supercontinent cycle. Subsequent late Neoproterozoic deposition overlapped a series of dramatic climatic events that are unparalleled in subsequent Phanerozoic time, as proposed by the “Snowball Earth” hypothesis. In particular, extreme negative ?13C excursions coincident with glacial diamictite and cap carbonate sequences imply that profound carbon flux changes accompanied

Nathan R. Miller; Mulugeta Alene; Rosalino Sacchi; Robert J. Stern; Anna Conti; Alfred Kröner; Gianmaria Zuppi

2003-01-01

28

III-V compound semiconductor film growth in low earth orbit on the wake shield facility  

NASA Astrophysics Data System (ADS)

Gallium Arsenide (GaAs) films, both silicon doped and undoped, have been deposited by Molecular Beam Epitaxy (MBE) in Low Earth Orbit (LEO) in an ultra vacuum environment created by the Wake Shield Facility (WSF). The WSF is a 12 foot diameter stainless steel disk that sweeps out a volume of space thus creating an ultra vacuum in its wake. It was developed specifically to take advantage of the ultra vacuum for the deposition of thin film materials. The WSF was flown for the first time on STS-60 in February, 1993. The mission objectives were to measure the unique wake vacuum environment and to epitaxially deposit GaAs thin films. In this paper, we describe the films deposited and report on the characterization performed to date. Films were deposited in two basic structures. The first structure consisted of undoped GaAs films of thicknesses ranging from 2 to 4 ?m with a thin (?200 nm) highly silicon doped layer (n?5×1017/cc) on top. This is basically a metal-semiconductor field effect transistor (MESFET) structure. The second structure was a lightly silicon doped GaAs film (n?5×1015/cc). We have obtained Photoluminescence (PL), Secondary Ion Mass Spectrometry (SIMS) and X-Ray diffraction data on selected films. The data indicate average quality single crystal films with oxygen and carbon contamination. The source of the contamination and further characterization will be discussed.

Horton, Charles; Ignatiev, Alex; Sterling, Mark; Bensaoula, Abdelhak; Freundlich, Alex; Pei, Steven; Sega, Ron

1995-01-01

29

How to protect the Earth from Global warming by means of Sunlight Shield Equipments  

Microsoft Academic Search

The Earth is getting warmer because excess carbon dioxide of the Earth's atmosphere. Many studies are proceeding in the world in order to prevent global warming. Three methods are studied: (1) How to reduce carbon dioxide of the Earth's atmosphere. For example, more trees will be planted and carbon dioxide is changed to oxygen and carbon. (2) How to reduce

H. Murakami

2010-01-01

30

Predictions of barrier island berm evolution in a time-varying storm climatology  

USGS Publications Warehouse

Low-lying barrier islands are ubiquitous features of the world's coastlines, and the processes responsible for their formation, maintenance, and destruction are related to the evolution of smaller, superimposed features including sand dunes, beach berms, and sandbars. The barrier island and its superimposed features interact with oceanographic forces (e.g., overwash) and exchange sediment with each other and other parts of the barrier island system. These interactions are modulated by changes in storminess. An opportunity to study these interactions resulted from the placement and subsequent evolution of a 2 m high sand berm constructed along the northern Chandeleur Islands, LA. We show that observed berm length evolution is well predicted by a model that was fit to the observations by estimating two parameters describing the rate of berm length change. The model evaluates the probability and duration of berm overwash to predict episodic berm erosion. A constant berm length change rate is also predicted that persists even when there is no overwash. The analysis is extended to a 16 year time series that includes both intraannual and interannual variability of overwash events. This analysis predicts that as many as 10 or as few as 1 day of overwash conditions would be expected each year. And an increase in berm elevation from 2 m to 3.5 m above mean sea level would reduce the expected frequency of overwash events from 4 to just 0.5 event-days per year. This approach can be applied to understanding barrier island and berm evolution at other locations using past and future storm climatologies.

Plant, Nathaniel G.; Flocks, James; Stockdon, Hilary F.; Long, Joseph W.; Guy, Kristy; Thompson, David M.; Cormier, Jamie M.; Smith, Christopher G.; Miselis, Jennifer L.; Dalyander, P. Soupy

2014-01-01

31

On the evolution of the Arabian-Nubian Shield and the largest shear zone on the Earth  

NASA Astrophysics Data System (ADS)

The Najd Fault System is known to be the largest pre-Mesozoic shear zone on the Earth. It developed in the context of the Pan African orogeny during the closure of the Mozambique Ocean and the subsequent collision between East- and West-Gondwanaland. The fault system crosses the entire Arabian Nubain Shield of northern Africa from northwest to southeast. During its activity, middle crustal level rocks were exhumed as a series of metamorphic complexes that are located in the Proterozoic rocks of Egypt and Saudi Arabia. It is now known that some of these complexes were exhumed as classical core complexes in extension regime. However, recent studies have shown that others (i.e those of Sinai) exhumed in oblique compression regime. Recent published age-dating data showed that this difference in exhumation mechanism is not only in a tectonic context but in the exhumation's age: Exhumation of the metamorphic complexes of the eastern part of the shield is much older than the exhumation of the western part. One way to test this new concept is to study the mid-crustal rocks of Saudi Arabia (eastern part of the shield). Preliminary work shows that all the metamorphic complexes of the Arabian-Nubian Shield exhumed due to the activity of the Najd Fault System over an interval of some tens of millions years (? 690 - 530 Ma). Early metamorphic complexes were exhumed in compression regime due to the collision between East- and West-Gondwanaland, while the later ones exhumed in extension setting due to the relaxation that follows the collision.

Hassan, M. M.; Abu-Alam, T. S.; Stuewe, K.; Meyer, S.; Passchier, C. W.

2012-12-01

32

Progress Toward Electrostatic Radiation Shielding of Interplanetary Spacecraft: Strategies, Concepts and Technical Challenges of Human Exploration Beyond Low Earth Orbit  

NASA Technical Reports Server (NTRS)

The radiation problem is a serious obstacle to solar system exploration. Electrostatic shielding was previously dismissed as unworkable. This was based on the false assumption that radial symmetry is needed to provide isotropic protection. KSC recently demonstrated the feasibility of asymmetric, multipole electrostatic shielding. Combined with passive shielding it might solve the radiation problem

Metzger, Philip T.; Lane, John E.; Youngquist, Robert C.

2004-01-01

33

Mid-crustal dynamics and island-arc accretion in the Arabian Shield: insight from the Earth's natural laboratory  

NASA Astrophysics Data System (ADS)

The late Proterozoic terrane of the Arabian Shield uniquely exposes the records of magmatic processes and deformation patterns that shaped the Earth over half a billion years ago. This Precambrian to Cambrian terrane is composed of supracrustal rocks underlain and intruded by igneous rocks. The plutonic shedding and accretion of the crust has been studied in detail. Satellite images (TM Landsat and SPOT) were processed to enhance both lithologic content and structural patterns, using spectral transformation and spatial filtering techniques. Results obtained by integrating the image interpretation with detailed ground studies are discussed. The supracrustal rocks display complex fold interference patterns, associated with the emplacement of the basic plutons (Jarshah and Mifsah) and mantled gneiss-domes (Qardath and Miktaa) which took place coeval with crustal shortening by regional deformation. The intrusion of a younger pluton (Arafadi) caused the collision of two pre-existing plutons (Jarshah and Mifsah), involved extensive sideway shedding of supracrustal rocks and formed a major shear zone (Qurayn). Finally, a subvolcanic complex (Mahala) was emplaced, which includes a 2.5-km radius ringdike of several hundred meters thickness. The geologic features of our study area can be explained by a simple model of island arc evolution in six stages: (I+II) Pre-tectonic and pre-plutonic, paleogeographic situation (0.9 to 0.66 Ga); (III) Syntectonic, basic plutonism (0.65 Ga); (IV) Syntectonic gneiss-domes (0.62 Ga); (V) Post-tectonic, acidic plutonism (0.59 to 0.54 Ga); and (VI) Post-orogenic volcanism (0.54 to 0.5 Ga). In our scenario, the relative ages of events inferred on the basis of field relationships are compatible with the geochronologic ages of rock units previously dated by radiometric methods only. The accretion rate of the Arabian Shield region is here estimated at 0.1 km 3 yr -1 or 10% of the total global accretion rate at the present-day. The average Arabian arc addition rate is 33 km 3 km -1 Ma -1 for the late Proterozoic, which is rather close to estimates of modern island-arc accretion rates of 30 km 3 km -1 Ma -1. We conclude that the process and rate of island-arc accretion onto active continental margins of Arabia in the late Precambrian eon evolved in a fashion similar to that of island-arc accretion in the Phanerozoic eon. This conclusion is important because it counters the view that, based on unrealistic assumptions, accretion rates for the late Proterozoic crust of the Arabian craton were as much as 10 times faster than the modern crustal accretion rates.

Weijermars, R.; Asif Khan, M.

2000-03-01

34

Evidence for the Snowball Earth hypothesis in the Arabian-Nubian Shield and the East African Orogen  

NASA Astrophysics Data System (ADS)

Formation of the Arabian-Nubian Shield (ANS) and the East African Orogen (EAO) occurred between 870 Ma and the end of the Precambrian (˜542 Ma). ANS crustal growth encompassed a time of dramatic climatic change, articulated as the Snowball Earth hypothesis (SEH). SEH identifies tremendous paleoclimatic oscillations during Neoproterozoic time. Earth’s climate shifted wildly, from times when much of our planet’s surface was frozen to unusually warm episodes and back again. There is evidence for four principal icehouse episodes: ˜585 582 Ma (Gaskiers), ˜660 635 Ma (Marinoan), ˜680 715 Ma (Sturtian), and ˜735 770 Ma (Kaigas). Evidence consistent with the SEH has been found at many locations around the globe but is rarely reported from the ANS, in spite of the fact that this may be the largest tract of Neoproterozoic juvenile crust on the planet, and in spite of the fact that Huqf Group sediments in Oman, flanking the ANS, record evidence for Sturtian and Marinoan low-latitude glaciations. This review identifies the most important evidence preserved in sedimentary rocks elsewhere for SEH: diamictites, dropstones, cap carbonates, and banded iron formation (BIF). Expected manifestations of SEH are integrated into our understanding of ANS and EAO tectonic evolution. If Kaigas and Sturtian events were global, sedimentary evidence should be preserved in ANS sequences, because these occurred during an embryonic stage of ANS evolution, when crustal components (island arcs, back-arc basins, and sedimentary basins) were mostly below sea level. Previous SEH investigations have been largely reconnaissance in scope, but potentially diagnostic sedimentary units such as diamictites, marine carbonates with ?13C excursions and banded iron formations are reported from the ANS and are worthy of further investigation. Collision and uplift to form the EAO destroyed most marine sedimentary basins about 630 Ma ago, so evidence of Marinoan and Gaskiers glaciations will be more difficult to identify. Several post-accretionary Neoproterozoic sedimentary basins in Arabia may preserve sedimentary evidence but such evidence has not been documented yet. The Huqf Group of Oman contains sedimentary evidence for the Marinoan glaciation but no evidence that the Gaskiers glaciation was significant in this part of the world. Deep erosion at ˜600 Ma throughout the northern ANS and EAO may be related to Marinoan continental glaciation, which may have accomplished much of the cutting of the ANS peneplain, but final shaping of the peneplain took place over the next 60 million years. African geoscientists can contribute to our understanding of Neoproterozoic climate change through careful field studies, and the international geoscientific community interested in Neoproterozoic climate change should pay attention to evidence from the ANS. Future investigations should include knowledge of the SEH and its controversial aspects, in addition to the greater plate tectonic setting of the ANS.

Stern, R. J.; Avigad, D.; Miller, N. R.; Beyth, M.

2006-01-01

35

Advanced Multifunctional MMOD Shield: Radiation Shielding Assessment  

NASA Technical Reports Server (NTRS)

As NASA is looking to explore further into deep space, multifunctional materials are a necessity for decreasing complexity and mass. One area where multifunctional materials could be extremely beneficial is in the micrometeoroid orbital debris (MMOD) shield. A typical MMOD shield on the International Space Station (ISS) is a stuffed whipple shield consisting of multiple layers. One of those layers is the thermal blanket, or multi-layer insulation (MLI). By increasing the MMOD effectiveness of MLI blankets, while still preserving their thermal capabilities, could allow for a less massive MMOD shield. Thus, a study was conducted to evaluate concept MLI blankets for MMOD shields. In conjunction, these MLI blankets and the subsequent MMOD shields were also evaluated for their radiation shielding effectiveness towards protecting crew. These concepts were evaluated against the ISS MLI blankets and the ISS MMOD shield, which acted as the baseline. These radiation shielding assessments were performed using the high charge and energy transport software (HZETRN). This software is based on a one-dimensional formula of the Boltzmann transport equation with a straight-ahead approximation. Each configuration was evaluated against the following environments to provide a diverse view of radiation shielding effectiveness in most space environments within the heliosphere: August 1972 solar particle event, October 1989 solar particle event, 1982 galactic cosmic ray environment (during solar maximum), 1987 galactic cosmic ray environment (during solar minimum), and a low earth orbit environment in 1970 that corresponded to an altitude of 400 km and inclination of 51.6 . Both the absorbed dose and the dose equivalent were analyzed, but the focus of the discussion was on the dose equivalent since the data is most concerned with radiation shielding of the crew. The following paper outlines the evaluations performed and discusses the results and conclusions of this evaluation for radiation shielding effectiveness. Future work will focus on optimizing the radiation shielding properties for the MMOD shield. Submission

Rojdev, Kristina; Christiansen, Eric

2011-01-01

36

Remedial shielding concepts for Line D and Line D facilities, Los Alamos Meson Physics Facility, Los Alamos National Laboratory, Los Alamos, New Mexico: Appendix 2. Final report  

SciTech Connect

This appendix contains the structural embankment analysis of the following Line D tunnel sections: 6(T/21), 5(21/21), 3(21/21), 2(21/21), 1(21/21), 2(21/24), 6(T/21), 3(23/23), 5(21/21)S, and 5(2/8). The structural assessment is for each section being covered with a 30 ft tuff berm used as shielding in the event of a beam spill. Each tunnel section is subject to vertical and horizontal loads estimated as 115 lbs/ft{sup 2} for each 1 ft or overburden and horizontal loads equivalent to 0.2948 of the vertical load, due to the weight of the tuff berm placed over the structure. The profile of the berm is based on preliminary shielding assessments. Shear, axial and bending stresses are determined with the associated tunnel deformations.

Pye, J.H.

1992-05-28

37

Effect of diatomaceous earths Fossil Shield and Silico-Sec on the egg laying behaviour of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae).  

PubMed

The pulse beetle, Callosobruchus maculatus (F.) is a destructive pest of pulses in both storage and field. It is well known that diatomaceous earth (DE) kill the insects by locally absorbing the epicuticular lipid layers leading to high rate of water loss through the cuticle. However, the effectiveness of DE depends on its ability to kill the adults before copulation and egg-laying. Newly emerged virgin males and females of Callosobruchus maculatus (F.) were exposed to the DEs, Fossil-Shield and Silico-Sec on 30 treated mungbeans (Vigna radita (L)). Fecundity, number of beans used for egg-laying and beans without eggs were evaluated after four days; the number of unhatched eggs was evaluated after ten days. It was determined, that the fecundity of female insects decreased sigmoidely with increasing rate of DE content. Percentages of unhatched eggs and seeds without eggs increased with increasing DE dosages. However, the maximum egg densities (eggs per used secd) occurred at 1200 mg DE/kg for Fossil-Shield and Silico-Sec. The reason for such DE-stimulated behaviour of egg laying expressed as a number of seeds with eggs of C. maculatus is not known, but it may be related to the stress caused by the inert dusts or to the reduction of both chemical and physical (tactile) stimuli. Treatment with DEs altered the surface texture of the beans and caused less cohesion between eggs and the seed surface. Only few larvae managed to penetrate into the grains, possibly due to increased grain roughness and repellent effect of DE. A relatively high number of eggs were laid on the surface of those beans where the amount of dust had been locally reduced by adults' movement and their pick up of DE. Therefore, several larvae tried to penetrate into these treated beans, causing a high larval density per partially cleaned bean. All these reasons lead to a progeny decline. PMID:12703482

Prasantha, B D Rohitha; Reichmuth, Ch; Büttner, C

2002-01-01

38

Earth  

NSDL National Science Digital Library

With three levels to choose from on each page - beginner, intermediate or advanced - this site provides information on our plant Earth. There is a section about water on earth and its many different varities, like freshwater, groundwater, and frozen water. There is information about the chemical make-up of water and many images showing the different water anvironments. There is a section about life in water, such as animals, plants, and plankton.

2008-10-03

39

Earth  

NSDL National Science Digital Library

This NASA (National Aeronautics and Space Administration) planet profile provides data and images of the planet Earth. These data include planet size, orbit facts, distance from the Sun, rotation and revolution times, temperature, atmospheric composition, density, surface materials and albedo. Images with descriptions show Earth features such as the Ross Ice Shelf in Antarctica, Simpson Desert in Australia, Mt. Etna in Sicily, the Cassiar Mountains in Canada, the Strait of Gibraltar, Mississippi River, Grand Canyon, Wadi Kufra Oasis in Libya, and Moon images such as Hadley Rille, Plum Crater, massifs and Moon rocks. These images were taken with the Galileo Spacecraft and by the Apollo missions.

40

Shielding for the variable energy cyclotron at Calcutta  

Microsoft Academic Search

Shielding calculations are done for the AVF Cyclotron under construction at Calcutta. Concrete shields are designed to reduce the fast neutron flux to less than the maximum permissible levels outside the shields. Earth shields are designed to reduce the fast neutron flux outside the building to less than the maximum permissible levels for public exposure. Experimentally measured values of half-value

G. Muthukrishnan; H. Singh; R. Mukherjee

1977-01-01

41

Modular shield  

DOEpatents

A modular system for containing projectiles has a sheet of material including at least a polycarbonate layer held by a metal frame having a straight frame member corresponding to each straight edge of the sheet. Each frame member has a U-shaped shield channel covering and holding a straight edge of the sheet and an adjacent U-shaped clamp channel rigidly held against the shield channel. A flexible gasket separates each sheet edge from its respective shield channel; and each frame member is fastened to each adjacent frame member only by clamps extending between adjacent clamp channels.

Snyder, Keith W. (Sandia Park, NM)

2002-01-01

42

Change in the length of the middle section of the Chandeleur Islands oil berm, November 17, 2010, through September 6, 2011  

USGS Publications Warehouse

On April 20, 2010, an explosion on the Deepwater Horizon oil rig drilling at the Macondo Prospect site in the Gulf of Mexico resulted in a marine oil spill that continued to flow through July 15, 2010. One of the affected areas was the Breton National Wildlife Refuge, which consists of a chain of low-lying islands, including Breton Island and the Chandeleur Islands, and their surrounding waters. The island chain is located approximately 115-150 kilometers north-northwest of the spill site. A sand berm was constructed seaward of, and on, the island chain. Construction began at the northern end of the Chandeleur Islands in June 2010 and ended in April 2011. The berm consisted of three distinct sections based on where the berm was placed relative to the islands. The northern section of the berm was built in open water on a submerged portion of the Chandeleur Islands platform. The middle section was built approximately 70-90 meters seaward of the Chandeleur Islands. The southern section was built on the islands' beaches. Repeated Landsat and SPOT satellite imagery and airborne lidar were used to observe the disintegration of the berm over time. The methods used to analyze the remotely sensed data and the resulting, derived data for the middle section are described in this report.

Plant, N.G., Guy, K.K.

2013-01-01

43

Change in the length of the northern section of the Chandeleur Islands oil berm, September 5, 2010, through September 3, 2012  

USGS Publications Warehouse

On April 20, 2010, an explosion on the Deepwater Horizon oil rig drilling at the Macondo Prospect site in the Gulf of Mexico resulted in a marine oil spill that continued to flow through July 15, 2010. One of the affected areas was the Breton National Wildlife Refuge, which consists of a chain of low-lying islands, including Breton Island and the Chandeleur Islands, and their surrounding waters. The island chain is located approximately 115–150 kilometers north-northwest of the spill site. A sand berm was constructed seaward of, and on, the island chain. Construction began at the northern end of the Chandeleur Islands in June 2010 and ended in April 2011. The berm consisted of three distinct sections based on where the berm was placed relative to the islands. The northern section of the berm was built in open water on a submerged portion of the Chandeleur Islands platform. The middle section was built approximately 70–90 meters seaward of the Chandeleur Islands. The southern section was built on the islands’ beaches. Repeated Landsat and SPOT satellite imagery and airborne lidar were used to observe the disintegration of the berm over time. The methods used to analyze the remotely sensed data and the resulting, derived data for the northern section are described in this report.

Plant, N.G.; Guy, K.K.

2013-01-01

44

Thematic Mapper Research in the Earth Sciences: Tectonic Evaluation of the Nubian Shield of Northeastern Sudan/Southeastern Egypt Using Thematic Mapper Imagery.  

National Technical Information Service (NTIS)

The tectonic evaluation of the Nubian Shield using the Thematic Mapper (TM) imagery is progressing well and shows great promise. The TM tapes for the six LANDSAT 5 scenes covering the northern portion of the Red Sea hills were received, and preliminary ma...

1986-01-01

45

Repair, Evaluation, Maintenance, and Rehabilitation Research Program. Stability of Toe Berm Armor Stone and Toe Buttressing Stone on Rubble-Mound Breakwaters and Jetties. Physical Model Investigation.  

National Technical Information Service (NTIS)

A series of two-dimensional (2-D) and three dimensional (3-D) breakwater stability experiments was developed and conducted to address the sizing of toe berm and toe buttressing stone in breaking wave environments. The 2-D tests focused on sizing of toe st...

D. G. Markle

1989-01-01

46

Skylab Solar Shield  

NASA Technical Reports Server (NTRS)

A sail like sunshade for possible use as a sunscreen for the Skylab Orbital Workshop (OWS) is shown being fabricated in the GE Building across the street from Johnson Space Center, Houston Texas. Three people help the steamstress feed the material through the sewing machine. The three-layered sunshade will be composed of a top layer of aluminized mylar, a middle layer of laminated nylon ripstop, and a bottom layer of thin nylon. Working on the sunshade are from left to right: Dale Gentry, Elizabeth Gauldin, Alyene Baker, and James H. Barnett Jr. Mrs. Baker, a GE employee, operates the double needle Singer sewing machine. Barnett is head of the Crew Equipment Development Section of JSC Crew Systems Division. Mrs. Gauldin is also with the Crew Systems Division. Gentry works for GE. The work shown here is part of the crash program underway to prepare a sunshield for Skylab to replace the orginal shield which was lost when Skylab 1 was launched on May 14, 1973. The improvised solar shield selected to be used will be carried to Earth orbit by the Skylab 2 crewman who will then deploy the reflective parasol to shade part of the OWS from the hot rays of the sun. Loss of the orginal sun shield has caused an overheating problem. in the Orbital Work Shop.

1973-01-01

47

Deep Space Environment and Shielding  

NASA Astrophysics Data System (ADS)

Mission scenarios outside the Earth's protective magnetic shield are being studied. Included are high usage assets in the near-Earth environment for casual trips, for research, for commercial and for operational platforms, in which career exposures will be multimission determined over the astronaut's lifetime. In addition, the exploration beyond these near Earth operational platforms will include single missions of long duration to planets, asteroids, and planetary satellites. The interplanetary environment is evaluated using convective diffusion theory. Local induced environments for each celestial body are modeled by using results from recent targeted spacecraft studies, and integrated into the design environments. Design scenarios are then evaluated for these missions. The underlying assumptions in deriving the model environments and their impact on mission exposures with various shield materials will be discussed.

Wilson, J. W.; Nealy, J. E.; de Angelis, G.; Clowdsley, M. S.; Badavi, F. F.

2003-01-01

48

Corium shield  

DOEpatents

A shield for restricting molten corium from flowing into a water sump disposed in a floor of a containment vessel includes upper and lower walls which extend vertically upwardly and downwardly from the floor for laterally bounding the sump. The upper wall includes a plurality of laterally spaced apart flow channels extending horizontally therethrough, with each channel having a bottom disposed coextensively with the floor for channeling water therefrom into the sump. Each channel has a height and a length predeterminedly selected for allowing heat from the molten corium to dissipate through the upper and lower walls as it flows therethrough for solidifying the molten corium therein to prevent accumulation thereof in the sump.

McDonald, Douglas B. (Pleasanton, CA); Buchholz, Carol E. (San Jose, CA)

1994-01-01

49

Rootless Shield -- Lava Flow  

USGS Multimedia Gallery

Rootless shields grow both in breadth and height through the accumulation of repeated overflows from the summits of the shields. In this photo, a stream of lava is flowing southward down the flank of this emergent shield....

2010-07-19

50

Advanced Multifunctional MMOD Shield: Radiation Shielding Assessment  

NASA Technical Reports Server (NTRS)

Deep space missions must contend with a harsh radiation environment Impacts to crew and electronics. Need to invest in multifunctionality for spacecraft optimization. MMOD shield. Goals: Increase radiation mitigation potential. Retain overall MMOD shielding performance.

Rojdev, Kristina; Christiansen, Eric

2013-01-01

51

Thematic mapper research in the Earth sciences: Tectonic evaluation of the Nubian Shield of northeastern Sudan/southeastern Egypt using thematic mapper imagery  

NASA Technical Reports Server (NTRS)

The tectonic evaluation of the Nubian Shield using the Thematic Mapper (TM) imagery is progressing well and shows great promise. The TM tapes for the six LANDSAT 5 scenes covering the northern portion of the Red Sea hills were received, and preliminary maps and interpretations were made for most of the area. It is apparent that faulting and shearing associated with the major suture zones such as the Sol Hamed are clearly visible and that considerable detail can be seen. An entire quadrant of scene 173,45 was examined in detail using all seven bands, and every band combination was evaluated to best display the geology. A comparison was done with color ratio combinations and color combinations of the eigen vector bands to verify if band combinations of 7-red, 4-green, and 2-blue were indeed superior. There is no single optimum enhancement which provides the greatest detail for every image and no single combination of spectral bands for all cases, although bands 7, 4, and 2 do provide the best overall display. The color combination of the eigen vector bands proved useful in distinguishing fine detailed features.

1986-01-01

52

Comparison of Geomagnetically-shielded Solar Energetic Proton Fluxes Observed at Geostationary Orbit by GOES and in Low-earth Orbit by SAMPEX, POES and MetOp  

NASA Astrophysics Data System (ADS)

On the current (13-15) and upcoming (R+) series of NOAA Geostationary Operational Environmental Satellites (GOES), solar protons are observed from each satellite in the eastward and westward directions. Solar protons that arrive at a given location in the inner magnetosphere have energies greater than their geomagnetic cutoffs, which depend on direction of arrival as well as the strength of geomagnetic disturbances. Protons arriving from the west at geostationary orbit (GEO) have much lower geomagnetic cutoff energies than protons arriving from the east. As a result, GOES westward observations of >4 MeV protons are representative of the interplanetary population near Earth and serve as the basis for NOAA's real-time solar radiation storm alerts. While the GOES westward observations are similar to the Solar, Anomalous and Magnetospheric Particle Explorer (SAMPEX) Proton-Electron Telescope (PET) proton observations in the polar cap (above invariant L = 10), GOES eastward observations more closely approximate the PET observations at invariant L = 4-4.5 in low earth orbit (LEO). Therefore, GOES may potentially provide a real-time, two-point estimate of the radial gradient of solar energetic protons between L = 6.6 and L = 4. However, the PET observations at L = 4-4.5 exhibit a much wider range of variability than the GOES eastward observations. Therefore, the purpose of this study is to determine how representative the GOES two-point gradient estimate is as a function of magnetic local time and geographic longitude. The study encompasses the largest solar proton events (SPE) in Solar Cycle 23 and to date in Solar Cycle 24. From April 1998 through December 2006, GOES 10 provides eastward GEO and SAMPEX PET provides LEO observations of large SPEs. The Solar Cycle 24 GEO observations are provided by GOES 13 and 15. From July 1998 to date, the Space Environment Monitors (SEM-2) on the NOAA Polar Operational Environmental Satellites (POES) and EUMETSAT MetOp-A provide SPE observations in additional LEO orbit planes (six as of August 2012). SEM-2 data that are severely contaminated by relativistic electrons are excluded from the study.

Rodriguez, J. V.; Mazur, J. E.; Green, J. C.; Machol, J. L.

2012-12-01

53

Predictions for Radiation Shielding Materials  

NASA Technical Reports Server (NTRS)

Radiation from galactic cosmic rays (GCR) and solar particle events (SPE) is a serious hazard to humans and electronic instruments during space travel, particularly on prolonged missions outside the Earth s magnetic fields. Galactic cosmic radiation (GCR) is composed of approx. 98% nucleons and approx. 2% electrons and positrons. Although cosmic ray heavy ions are 1-2% of the fluence, these energetic heavy nuclei (HZE) contribute 50% of the long-term dose. These unusually high specific ionizations pose a significant health hazard acting as carcinogens and also causing microelectronics damage inside spacecraft and high-flying aircraft. These HZE ions are of concern for radiation protection and radiation shielding technology, because gross rearrangements and mutations and deletions in DNA are expected. Calculations have shown that HZE particles have a strong preference for interaction with light nuclei. The best shield for this radiation would be liquid hydrogen, which is totally impractical. For this reason, hydrogen-containing polymers make the most effective practical shields. Shielding is required during missions in Earth orbit and possibly for frequent flying at high altitude because of the broad GCR spectrum and during a passage into deep space and LunarMars habitation because of the protracted exposure encountered on a long space mission. An additional hazard comes from solar particle events (SPEs) which are mostly energetic protons that can produce heavy ion secondaries as well as neutrons in materials. These events occur at unpredictable times and can deliver a potentially lethal dose within several hours to an unshielded human. Radiation protection for humans requires safety in short-term missions and maintaining career exposure limits within acceptable levels on future long-term exploration missions. The selection of shield materials can alter the protection of humans by an order of magnitude. If improperly selected, shielding materials can actually increase radiation damage due to penetration properties and nuclear fragmentation. Protecting space-borne microelectronics from single event upsets (SEUs) by transmitted radiation will benefit system reliability and system design cost by using optimal shield materials. Long-term missions on the surface of the Moon or Mars will require the construction of habitats to protect humans during their stay. One approach to the construction is to make structural materials from lunar or Martian regolith using a polymeric material as a binder. The hydrogen-containing polymers are considerably more effective for radiation protection than the regolith, but the combination minimizes the amount of polymer to be transported. We have made composites of simulated lunar regolith with two different polymers, LaRC-SI, a high-performance polyimide thermoset, and polyethylene, a thermoplastic.

Kiefer, Richard L.

2002-01-01

54

Meteoroid/Debris Shielding  

NASA Technical Reports Server (NTRS)

This report provides innovative, low-weight shielding solutions for spacecraft and the ballistic limit equations that define the shield's performance in the meteoroid/debris environment. Analyses and hypervelocity impact testing results are described that have been used in developing the shields and equations. Spacecraft shielding design and operational practices described in this report are used to provide effective spacecraft protection from meteoroid and debris impacts. Specific shield applications for the International Space Station (ISS), Space Shuttle Orbiter and the CONTOUR (Comet Nucleus Tour) space probe are provided. Whipple, Multi-Shock and Stuffed Whipple shield applications are described.

Christiansen, Eric L.

2003-01-01

55

Shielded Bearing Lubrication.  

National Technical Information Service (NTIS)

Precise quantities of lubricant under automatic control are injected through chambers of housings into shielded rolling element bearings. Separate feed line conduits directly deliver the lubricant to the shielded critical surfaces of such bearings and ins...

J. A. Wong T. L. Daugherty G. D. Huntzberry

1996-01-01

56

Rotating shielded crane system  

DOEpatents

A rotating, radiation shielded crane system for use in a high radiation test cell, comprises a radiation shielding wall, a cylindrical ceiling made of radiation shielding material and a rotatable crane disposed above the ceiling. The ceiling rests on an annular ledge intergrally attached to the inner surface of the shielding wall. Removable plugs in the ceiling provide access for the crane from the top of the ceiling into the test cell. A seal is provided at the interface between the inner surface of the shielding wall and the ceiling.

Commander, John C. (Idaho Falls, ID)

1988-01-01

57

Wake Shield Facility  

NASA Technical Reports Server (NTRS)

The Wake Shield Facility is a free-flying research and development facility that is designed to use the pure vacuum of space to conduct scientific research in the development of new materials. The thin film materials technology developed by the WSF could some day lead to applications such as faster electronics components for computers. The WSF Free-Flyer is a 12-foot-diameter stainless steel disk that, while traveling in orbit at approximately 18,000 mph, leaves in its wake a vacuum 1,000 to 10,000 times better than the best vacuums currently achieved on Earth. While it is carried into orbit by the Space Shuttle, the WSF is a fully equipped spacecraft in its own right, with cold gas propulsion for separation from the orbiter and a momentum bias attitude control system. All WSF functions are undertaken by a spacecraft computer with the WSF remotely controlled from the ground. The ultra vacuum, nearly empty of all molecules, is then used to conduct a series of thin film growths by a process called epitaxy which produces exceptionally pure and atomically ordered thin films of semiconductor compounds such as gallium arsenide. Using this process, the WSF offers the potential of producing thin film materials, and the devices they will make possible.

2004-01-01

58

Gravity Scaling of a Power Reactor Water Shield  

NASA Astrophysics Data System (ADS)

Water based reactor shielding is being considered as an affordable option for potential use on initial lunar surface reactor power systems. Heat dissipation in the shield from nuclear sources must be rejected by an auxillary thermal hydraulic cooling system. The mechanism for transferring heat through the shield is natural convection between the core surface and an array of thermosyphon radiator elements. Natural convection in a 100 kWt lunar surface reactor shield design has been previously evaluated at lower power levels (Pearson, 2006). The current baseline assumes that 5.5 kW are dissipated in the water shield, the preponderance on the core surface, but with some volumetric heating in the naturally circulating water as well. This power is rejected by a radiator located above the shield with a surface temperature of 370 K. A similarity analysis on a water-based reactor shield is presented examining the effect of gravity on free convection between a radiation shield inner vessel and a radiation shield outer vessel boundaries. Two approaches established similarity: 1) direct scaling of Rayleigh number equates gravity-surface heat flux products, 2) temperature difference between the wall and thermal boundary layer held constant on Earth and the Moon. Nussult number for natural convection (laminar and turbulent) is assumed of form Nu = CRan. These combined results estimate similarity conditions under Earth and Lunar gravities. The influence of reduced gravity on the performance of thermosyphon heat pipes is also examined.

Reid, Robert S.; Pearson, J. Boise

2008-01-01

59

Gravity Scaling of a Power Reactor Water Shield  

NASA Technical Reports Server (NTRS)

Water based reactor shielding is being considered as an affordable option for use on initial lunar surface power systems. Heat dissipation in the shield from nuclear sources must be rejected by an auxiliary thermal hydraulic cooling system. The mechanism for transferring heat through the shield is natural convection between the core surface and an array of thermosyphon radiator elements. Natural convection in a 100 kWt lunar surface reactor shield design has been previously evaluated at lower power levels (Pearson, 2007). The current baseline assumes that 5.5 kW are dissipated in the water shield, the preponderance on the core surface, but with some volumetric heating in the naturally circulating water as well. This power is rejected by a radiator located above the shield with a surface temperature of 370 K. A similarity analysis on a water-based reactor shield is presented examining the effect of gravity on free convection between a radiation shield inner vessel and a radiation shield outer vessel boundaries. Two approaches established similarity: 1) direct scaling of Rayleigh number equates gravity-surface heat flux products, 2) temperature difference between the wall and thermal boundary layer held constant on Earth and the Moon. Nussult number for natural convection (laminar and turbulent) is assumed of form Nu = CRa(sup n). These combined results estimate similarity conditions under Earth and Lunar gravities. The influence of reduced gravity on the performance of thermosyphon heat pipes is also examined.

Reid, Robert S.; Pearson, J. Boise

2008-01-01

60

A thermal shield concept for the Solar Probe mission  

NASA Technical Reports Server (NTRS)

The Solar Probe spacecraft will travel to within 4 solar radii of the sun's center while performing a variety of fundamental experiments in space physics. Exposure to 2900 earth suns (400 W/sq cm) at perihelion imposes severe thermal and material demands on a solar shield system designed to protect the payload that will reside within the shield's shadow envelope or umbra. The design of the shield subsystem is a thermal/materials challenge requiring new technology development. While currently in the preproject study phase, anticipating a 1995 project start, shield preliminary design efforts are currently underway. This paper documents the current status of the mission concept, the materials issues, the configuration concept for the shield subsystem, the current configuration studies performed to date, and the required material testing to provide a database to support a design effort required to develop the shield subsystem.

Miyake, Robert N.; Millard, Jerry M.; Randolph, James E.

1991-01-01

61

Sea-level proxies extracted from GPR reflection data collected across recently formed berm, beach ridge and swale deposits on the island of Anholt, Denmark  

NASA Astrophysics Data System (ADS)

GPR reflection data have been collected across the most recent part of a berm, beach ridge and swale system formed during the last 130 years on the northern coast of the island of Anholt, the Kattegat, Denmark. The reflected arrivals have a peak frequency of about 250 MHz and they image the subsurface with a vertical resolution of 0.1-0.2 m to a maximum depth of 5 m below the surface. The berm and beach ridges with maximum heights of about 1.8 m and 1.5 m, respectively, appear as mounded features in the GPR sections. The berm ridge also contains low-angle, seaward dipping reflections. Similar sea-ward dipping reflections are also observed below swales, and current swale surfaces appear to constitute erosion surfaces. Reflections downlapping on a package of reflections, which is interpreted to be representative of upper shoreface deposits, are suggested to constitute good proxies of sea level. Tamura et al. (2008) suggested that similar downlapping reflections may represent a depth level of about 1 m below the mean sea level based on investigations of the Kujukuri strand plain in eastern Japan. We have made 17 depth readings of such downlaps along our 159-m-long profile. The average depth of these downlap points is 0.003 m below present mean sea level (pmsl). Individual readings fall in the range of -0.5 m to +0.5 above pmsl, consistent with the majority of current, annual sea-level variations as recorded by the Danish Maritime Safety Administration at a position about 50 km southwest of Anholt. The mean sea level has changed insignificantly in the study area during ridge formation, and we assume that these proxies may form a strong basis for constructing palaeo-sea level curves for fossil (ages of up to about 7500 years), raised beach-ridge systems along the shores of the Kattegat and the Baltic Sea. Reference T. Tamura, F. Murakami, F. Nanayama, K. Watanabe, Y. Saito, 2008. Ground-penetrating radar profiles of Holocene raised-beach deposits in the Kujukuri strand plain, Pacific coast of eastern Japan, Marine Geology, 248, 11-27.

Nielsen, L.; Clemmensen, L. B.

2009-04-01

62

INTOR radiation shielding for personnel access  

SciTech Connect

The INTOR reactor shield system consists of the blanket, bulk shield, penetration shield, component shield, and biological shield. The bulk shield consists of two parts: (a) the inboard shield; and (b) the outboard shield. The distinction between the different components of the shield system is essential to satisfy the different design constraints and achieve various objectives.

Gohar, Y.; Abdou, M.

1981-01-01

63

RF shielded connectors  

NASA Technical Reports Server (NTRS)

Gap, where cable joins connector housing, is shielded effectively by composite RF shielding made from suitable potting resin material (fumed silica, thixotropic prepolymer composition), conductive coating (silver-filled, flexible, polyurethane resin), and protective jacket (wax coated housing formed around another wax form having contours shaped to match configuration).

Fisher, A.; Clatterbuck, C.

1974-01-01

64

Iron shielded MRI optimization  

Microsoft Academic Search

The design of the main current systems of an actively shielded and of an iron shielded MRI device for nuclear resonance imaging, is considered. The model for the analysis of the magnetic induction produced by the current system, is based on the combination of a Boundary Element technique and of the integration of two Fredholm integral equations of the first

C. A. Borghi; M. Fabbri

1998-01-01

65

Gamma ray detector shield  

DOEpatents

A gamma ray detector shield comprised of a rigid, lead, cylindrical-shaped vessel having upper and lower portions with an pneumatically driven, sliding top assembly. Disposed inside the lead shield is a gamma ray scintillation crystal detector. Access to the gamma detector is through the sliding top assembly.

Ohlinger, R.D.; Humphrey, H.W.

1985-08-26

66

EMP Instrumentation Shielding and Evaluation.  

National Technical Information Service (NTIS)

Special purpose hardware was developed to harden recording instrumentation to EMP simulator fields. This included probe shields, instrumentation system shields, and differential voltage attenuators. Calibration and shielding evaluation techniques were als...

B. C. Tupper

1970-01-01

67

Shielding Structures for Interplanetary Human Mission  

NASA Astrophysics Data System (ADS)

Since the end of Apollo missions, human spaceflight has been limited to the Low Earth Orbit (LEO), inside the protective magnetic field of the Earth, because astronauts are, to the largest degree, protected from the harsh radiation environment of the interplanetary space. However, this situation will change when space exploration missions beyond LEO will become the real challenge of the human exploration program. The feasibility of these missions in the solar system is thus strongly connected to the capability to mitigate the radiation-induced biological effects on the crew during the journey and the permanence on the intended planet surface. Inside the International Space Station (ISS), the volumes in which the crew spends most of the time, namely the crew quarters are the only parts that implement dedicated additional radiation shielding made of polyethylene tiles designed for mitigating SPE effects. Furthermore, specific radiation shielding materials are often added to the described configuration to shield crew quarters or the entire habitat example of these materials are polyethylene, liquid hydrogen, etc. but, increasing the size of the exploration vehicles to bring humans beyond LEO, and without the magnetosphere protection, such approach is unsustainable because the mass involved is a huge limiting factor with the actual launcher engine technology. Moreover, shielding against GCR with materials that have a low probability of nuclear interactions and in parallel a high ionizing energy loss is not always the best solution. In particular there is the risk to increase the LET of ions arriving at the spacecraft shell, increasing their Radio-Biological Effectiveness. Besides, the production of secondary nuclei by projectile and target fragmentation is an important issue when performing an engineering assessment of materials to be used for radiation shielding. The goal of this work is to analyze different shielding solutions to increase as much as possible the radiation shielding power of the interplanetary habitat structures, like the spacecraft shell, minimizing the amount of mass used. From the radiation protection point of view the spacecraft shell is an interesting spacecraft system because it surrounds almost homogeneously all the habitat and it is typically composed by the Micrometeorites and Debris Protection Systems (MDPS), the Multilayer Insulation (MLI) for thermal control purposes, and the primary structure that offers the pressure containment functionality. Nevertheless, the spacecraft internal outfitting is important to evaluate the different shielded areas in the habitat. Using Geant4 Monte Carlo simulations toolkit through GRAS (Geant4 Radiation Analysis for Space) tool, different spacecraft structures will be analyzed for their shielding behavior in terms of fluxes, dose reduction and radiation quality, and for their implementation in a real pressurized module. Effects on astronauts and electronic equipments will be also assessed with respect to the standard aluminum structures.

Tracino, Emanuele; Lobascio, Cesare

2012-07-01

68

Large shield volcanoes on the Moon  

NASA Astrophysics Data System (ADS)

volcanic style of the Moon has long been understood to consist almost exclusively of flood basalts erupted from fissures along with minor pyroclastic activity; large central vent shield volcanoes that characterize basaltic volcanism on the other terrestrial planets appeared to be absent. Small (few kilometers diameter) central vent constructs have long been recognized in the lunar maria and often are found clustered in fields throughout the lunar maria. New global topographic data from the LOLA and LROC instruments on LRO reveal that almost all of these volcanic complexes on the Moon occur on large, regional topographic rises in the lunar maria, tens to hundreds of kilometers in extent and between several hundred to several thousand meters high. We propose that these topographic swells are shield volcanoes and are the lunar equivalents of the large basaltic shields found on the Earth, Venus, and Mars. The newly recognized lunar shields are found peripheral to the large, deeply flooded impact basins Imbrium and Serenitatis, suggesting a genetic relation to those features. Loading of the lithosphere by these basalt-filled basins may be responsible for inducing a combination of flexural and membrane stress, inducing a pressure distribution on vertically oriented dikes favorable to magma ascent. This condition would occur in a zone annular to the large circular loads produced by the basins, where the shield volcanoes occur.

Spudis, Paul D.; McGovern, Patrick J.; Kiefer, Walter S.

2013-05-01

69

Constructing earth sheltered housing with concrete  

SciTech Connect

This manual provides a state - of - the - art review of the design and construction of an earth - sheltered house using cast - in - place concrete, precast concrete, and concrete masonry. Based on a literature survey, theoretical work, and discussions with researchers and engineers in the concrete industry, the text is designed for use by architects, engineers, and homebuilders. The features of concrete construction that are current accepted practice for the concrete products discussed are shown to be applicable with reasonable care to building a safe, dry, and comfortable earth - sheltered house. The main considerations underlying the recommendations were the use of the earth's mass and passive solar effects to minimize energy needs, the structural capacity of the separate concrete products and their construction methods, and drainage principles and waterproofing details. Shelter ranging from those with at least 2 feet of earth cover to those with an uncovered roof of usual construction are included. To be considered an earth - sheltered residential building, at least half of the exterior wall and roof area that is in direct contact with the conditioned living space must be sheltered from the environment by earth berm or earthfill. Siting considerations, the fundamentals of passive solar heating, planning considerations, and structural considerations are discussed. Detailed guidelines are provided on concrete masonry construction, joint details in walls and floors, waterproofing, formwork and form removal, concrete construction practices, concrete masonry, and surface finishes. Numerous illustrations, tables, and a list of 32 references are provided. (Author abstract modified).

Spears, R.E.

1981-01-01

70

Gravity Scaling of a Power Reactor Water Shield  

NASA Technical Reports Server (NTRS)

A similarity analysis on a water-based reactor shield examined the effect of gravity on free convection between a reactor shield inner and outer vessel boundaries. Two approaches established similarity between operation on the Earth and the Moon: 1) direct scaling of Rayleigh number equating gravity-surface heat flux products, 2) temperature difference between the wall and thermal boundary layer held constant. Nusselt number for natural convection (laminar and turbulent) is assumed of form Nu = CRa(sup n).

Reid, Robert S.; Pearson, J. Boise

2007-01-01

71

What Is Radiation Shielding?  

NASA Video Gallery

Kerry Lee, NASA Orion radiation system manager, explains how radiation shielding is used to block harmful particles coming into the spacecraft without producing secondary particles that can cause e...

72

Grounding, Shielding, and Bonding.  

National Technical Information Service (NTIS)

In the electromagnetic compatibility design (EMC) of systems and circuits, both grounding and shielding are related to the coupling mechanisms of the system with (radiated) electromagnetic fields. Grounding is more related to the source or victim circuit ...

J. Catrysse

1991-01-01

73

Adhesive particle shielding  

DOEpatents

An efficient device for capturing fast moving particles has an adhesive particle shield that includes (i) a mounting panel and (ii) a film that is attached to the mounting panel wherein the outer surface of the film has an adhesive coating disposed thereon to capture particles contacting the outer surface. The shield can be employed to maintain a substantially particle free environment such as in photolithographic systems having critical surfaces, such as wafers, masks, and optics and in the tools used to make these components, that are sensitive to particle contamination. The shield can be portable to be positioned in hard-to-reach areas of a photolithography machine. The adhesive particle shield can incorporate cooling means to attract particles via the thermophoresis effect.

Klebanoff, Leonard Elliott (Dublin, CA); Rader, Daniel John (Albuquerque, NM); Walton, Christopher (Berkeley, CA); Folta, James (Livermore, CA)

2009-01-06

74

Crash-Resistant Shield  

NASA Technical Reports Server (NTRS)

Impact-resistant shield designed to consist of aluminum honeycomb structure sandwiched between inner and outer aluminum skins. Intended to protect radioisotope thermoelectric generator of spacecraft from impact with ground or water after free fall from upper atmosphere. Designed to absorb impact energy by buckling, while inner and outer skins designed to protect against shrapnel, overpressure, and impact loads. Concept of shield applicable to crashproof compartments for ground vehicles and aircraft.

Bixler, Charles H.

1990-01-01

75

Space Station MMOD Shielding  

NASA Technical Reports Server (NTRS)

This paper describes International Space Station (ISS) shielding for micrometeoroid orbital debris (MMOD) protection, requirements for protection, and the technical approach to meeting requirements. Current activities in MMOD protection for ISS will be described, including efforts to augment MMOD protection by adding shields on-orbit. Observed MMOD impacts on ISS elements such as radiators, modules and returned hardware will be described. Comparisons of the observed damage with predicted damage using risk assessment software will be made.

Christiansen, Eric

2006-01-01

76

Electrodynamic Dust Shield Demonstrator  

NASA Technical Reports Server (NTRS)

The objective of the project was to design and manufacture a device to demonstrate a new technology developed by NASA's Electrostatics and Surface Physics Laboratory. The technology itself is a system which uses magnetic principles to remove regolith dust from its surface. This project was to create an enclosure that will be used to demonstrate the effectiveness of the invention to The Office of the Chief Technologist. ONE of the most important challenges of space exploration is actually caused by something very small and seemingly insignificant. Dust in space, most notably on the moon and Mars, has caused many unforeseen issues. Dirt and dust on Earth, while a nuisance, can be easily cleaned and kept at bay. However, there is considerably less weathering and erosion in space. As a result, the microscopic particles are extremely rough and abrasive. They are also electrostatically charged, so they cling to everything they make contact with. This was first noted to be a major problem during the Apollo missions. Dust would stick to the spacesuits, and could not be wiped off as predicted. Dust was brought back into the spacecraft, and was even inhaled by astronauts. This is a major health hazard. Atmospheric storms and other events can also cause dust to coat surfaces of spacecraft. This can cause abrasive damage to the craft. The coating can also reduce the effectiveness of thermal insulation and solar panels.' A group of engineers at Kennedy Space Center's Electrostatics and Surface Physics Laboratory have developed a new technology, called the Electrodynamic Dust Shield, to help alleviate these problems. It is based off of the electric curtain concept developed at NASA in 1967. "The EDS is an active dust mitigation technology that uses traveling electric fields to transport electrostatically charged dust particles along surfaces. To generate the traveling electric fields, the EDS consists of a multilayer dielectric coating with an embedded thin electrode grid running a multiphase low frequency AC signal. Electrostatically charged particles, such as those encountered on the moon, Mars, or an asteroid, are carried along by the traveling field due to the action of Coulomb and dielectrophoretic forces."2 The technical details have been described in a separate article. This document details the design and construction process of a small demonstration unit. Once finished, this device will go to the Office of the ChiefTechnologist at NASA headquarters, where it will be used to familiarize the public with the technology. 1 NASA KSC FO Intern, Prototype Development Laboratory, Kennedy Space Center, University of Central Florida Kennedy Space

Stankie, Charles G.

2013-01-01

77

Side Shield for Wall Support  

NASA Technical Reports Server (NTRS)

Method employs curved shield on each side of mining machine. In stowed position, shield folded against roof-support columns on one side. In deployed position, shield raised and braced against coal-seam wall by hydraulic cylinder. Shield supports wall until roof and wall properly secured by bolting and cement coating.

Lewis, E. V.

1985-01-01

78

A high-performance magnetic shield with large length-to-diameter ratio.  

PubMed

We have demonstrated a 100-fold improvement in the magnetic field uniformity on the axis of a large aspect ratio, cylindrical, mumetal magnetic shield by reducing discontinuities in the material of the shield through the welding and re-annealing of a segmented shield. The three-layer shield reduces Earth's magnetic field along an 8 m region to 420 ?G (rms) in the axial direction, and 460 and 730 ?G (rms) in the two transverse directions. Each cylindrical shield is a continuous welded tube which has been annealed after manufacture and degaussed in the apparatus. We present both experiments and finite element analysis that show the importance of uniform shield material for large aspect ratio shields, favoring a welded design over a segmented design. In addition, we present finite element results demonstrating the smoothing of spatial variations in the applied magnetic field by cylindrical magnetic shields. Such homogenization is a potentially useful feature for precision atom interferometric measurements. PMID:22755663

Dickerson, Susannah; Hogan, Jason M; Johnson, David M S; Kovachy, Tim; Sugarbaker, Alex; Chiow, Sheng-wey; Kasevich, Mark A

2012-06-01

79

Skylab and Earth Limb  

NASA Technical Reports Server (NTRS)

An overhead view of the Skylab Orbital Workshop in Earth orbit as photographed from the Skylab 4 Command and Service Modules (CSM) during the final fly-around by the CSM before returning home. The space station is contrasted against the pale blue Earth. During launch on May 14, 1973, some 63 seconds into flight, the micrometeor shield on the Orbital Workshop (OWS) experienced a failure that caused it to be caught up in the supersonic air flow during ascent. This ripped the shield from the OWS and damaged the tie downs that secured one of the solar array systems. Complete loss of one of the solar arrays happened at 593 seconds when the exhaust plume from the S-II's separation rockets impacted the partially deployed solar array system. Without the micrometeoroid shield that was to protect against solar heating as well, temperatures inside the OWS rose to 126 degrees fahrenheit. The gold 'parasol' clearly visible in the photo, was designed to replace the missing micrometeoroid shield, protecting the workshop against solar heating. The replacement solar shield was deployed by the Skylab I crew. This enabled the Skylab Orbital Workshop to fulfill all its mission objects serving as home to additional crews before being deorbited in 1978.

1974-01-01

80

EXPERIMENTAL VERIFICATION OF SHIELDING EQUATIONS  

Microsoft Academic Search

S>Building factors for iron shields, lead shields, and laminated iron-; lead shields (1.7 mean free paths of lead and 1 to 3 mean free paths of iron per ; lamination) were determined for shield thicknesses up to 6.8 mean free paths of ; lead, 8.7 mean free paths of iron, and 9.2 mean free paths of laminated shielding. ; A

C. L. Kusik; T. R. Jaworowski; D. C. Morse; D. G. Strawson

1957-01-01

81

Honeycomb thermal shield study  

NASA Technical Reports Server (NTRS)

A honeycomb thermal shield is described which is an economical and reliable alternative to existing thermal shielding methods for reducing the radiated heat loss from elements which will not allow obstructions in the field of view. The device is simply open-face honeycomb of the type used throughout the aerospace industry for structural panels. The honeycomb thermal shield uses only the core of the honeycomb panel, so it has little structural stiffness and is transparent through the cells. It is located in close proximity to, but conductively decoupled from, the element to be shielded (the radiative source) with the axis of the honeycomb cells parallel to the view direction of the source. The source radiates into a 2pi steradian field occupied by the shield. The view field will be transparent along the axis of the honeycomb but will be increasingly obscured as the off-normal view angle increases. The angular dependence is a function of the cell height to width ratio.

Dombroski, R. M.

1975-01-01

82

Regolith-Derived Heat Shield for Planetary Body Entry and Descent System with In-Situ Fabrication  

NASA Technical Reports Server (NTRS)

High-mass planetary surface access is one of NASA's Grand Challenges involving entry, descent, and landing (EDL). Heat shields fabricated in-situ can provide a thermal protection system for spacecraft that routinely enter a planetary atmosphere. Fabricating the heat shield from extraterrestrial regolith will avoid the costs of launching the heat shield mass from Earth. This project investigated three methods to fabricate heat shield using extraterrestrial regolith and performed preliminary work on mission architectures.

Hogue, Michael D.; Mueller, Robert P.; Sibille, Laurent; Hintze, Paul E.; Rasky, Daniel J.

2012-01-01

83

Radiation shielding composition  

DOEpatents

A composition for use as a radiation shield. The shield is a concrete product containing a stable uranium aggregate for attenuating gamma rays and a neutron absorbing component, the uranium aggregate and neutron absorbing component being present in the concrete product in sufficient amounts to provide a concrete having a density between about 4 and about 15 grams/cm.sup.3 and which will at a predetermined thickness, attenuate gamma rays and absorb neutrons from a radioactive material of projected gamma ray and neutron emissions over a determined time period. The composition is preferably in the form of a container for storing radioactive materials that emit gamma rays and neutrons. The concrete container preferably comprises a metal liner and/or a metal outer shell. The resulting radiation shielding container has the potential of being structurally sound, stable over a long period of time, and, if desired, readily mobile.

Quapp, William J. (Idaho Falls, ID); Lessing, Paul A. (Idaho Falls, ID)

2000-12-26

84

Radiation shielding composition  

DOEpatents

A composition for use as a radiation shield. The shield is a concrete product containing a stable uranium aggregate for attenuating gamma rays and a neutron absorbing component, the uranium aggregate and neutron absorbing component being present in the concrete product in sufficient amounts to provide a concrete having a density between about 4 and about 15 grams/cm.sup.3 and which will at a predetermined thickness, attenuate gamma rays and absorb neutrons from a radioactive material of projected gamma ray and neutron emissions over a determined time period. The composition is preferably in the form of a container for storing radioactive materials that emit gamma rays and neutrons. The concrete container preferably comprises a metal liner and/or a metal outer shell. The resulting radiation shielding container has the potential of being structurally sound, stable over a long period of time, and, if desired, readily mobile.

Quapp, William J. (Idaho Falls, ID); Lessing, Paul A. (Idaho Falls, ID)

1998-01-01

85

Radiation shielding composition  

DOEpatents

A composition is disclosed for use as a radiation shield. The shield is a concrete product containing a stable uranium aggregate for attenuating gamma rays and a neutron absorbing component, the uranium aggregate and neutron absorbing component being present in the concrete product in sufficient amounts to provide a concrete having a density between about 4 and about 15 grams/cm{sup 3} and which will at a predetermined thickness, attenuate gamma rays and absorb neutrons from a radioactive material of projected gamma ray and neutron emissions over a determined time period. The composition is preferably in the form of a container for storing radioactive materials that emit gamma rays and neutrons. The concrete container preferably comprises a metal liner and/or a metal outer shell. The resulting radiation shielding container has the potential of being structurally sound, stable over a long period of time, and, if desired, readily mobile. 5 figs.

Quapp, W.J.; Lessing, P.A.

1998-07-28

86

Space Radiation Superconducting Shields  

NASA Astrophysics Data System (ADS)

The interest on shields to protect astronauts I long term missions against GCR has recently grown and several projects have been funded. Due to their large mass, passive shields for large volume habitable modules are no longer an option and the attention is focused on the more complex, technologically challenging active systems. Among the possible solutions, the most promising is based on huge superconducting coils having a bending power sufficient to deflect out of the habitat charged particles with kinetic energy in the order of 1 GeV. Toroidal magnet systems based wound with Ti clad MgB2 conductor is proposed and described.

R-Musenich; Calvelli, V.; Farinon, S.; Burger, W. J.; Battiston, R.

2014-05-01

87

Glove box shield  

SciTech Connect

According to the present invention, a shield for a glove box housing radioactive material is comprised of spaced apart clamping members which maintain three overlapping flaps in place therebetween. There is a central flap and two side flaps, the side flaps overlapping at the interior edges thereof and the central flap extending past the intersection of the side flaps in order to insure that the shield is always closed when the user withdraws his hand from the glove box. Lead loaded neoprene rubber is the preferred material for the three flaps, the extent of lead loading depending upon the radiation levels within the glove box.

Brackenbush, Larry W. (Richland, WA); Hoenes, Glenn R. (Richland, WA)

1981-01-01

88

Glove box shield  

SciTech Connect

According to the present invention, a shield for a glove box housing radioactive material is comprised of spaced apart clamping members which maintain three overlapping flaps in place therebetween. There is a central flap and two side flaps, the side flaps overlapping at the interior edges thereof and the central flap extending past the intersection of the side flaps in order to insure that the shield is always closed when the user withdraws his hand from the glove box. Lead loaded neoprene rubber is the preferred material for the three flaps, the extent of lead loading depending upon the radiation levels within the glove box. 2 figs.

Brackenbush, L.W.; Hoenes, G.R.

1981-02-17

89

Composition for radiation shielding  

DOEpatents

A composition for use as a radiation shield. The shield has a depleted urum core for absorbing gamma rays and a bismuth coating for preventing chemical corrosion and absorbing gamma rays. Alternatively, a sheet of gadolinium may be positioned between the uranium core and the bismuth coating for absorbing neutrons. The composition is preferably in the form of a container for storing materials that emit radiation such as gamma rays and neutrons. The container is preferably formed by casting bismuth around a pre-formed uranium container having a gadolinium sheeting, and allowing the bismuth to cool. The resulting container is a structurally sound, corrosion-resistant, radiation-absorbing container.

Kronberg, James W. (Aiken, SC)

1994-01-01

90

Analysis of face stability and ground settlement in EPB shield tunnelling for the Nanjing metro  

Microsoft Academic Search

Abstract: Nanjing Metro No.1 line is 16.92 km in total length, of which 6.11 km is above ground level and 10.81 km is underground. It passes through very complicated geological terrain such as: shallow hills, rock layers and ancient floodplains. Shield tunnelling was carried out using an earth pressure balanced (EPB) shield along the line. The EPB shield tunnelling machine

SHULIN SUN; HONGJUN PEI; SHUFENG ZHANG

2006-01-01

91

Splicing shielded cables  

NASA Technical Reports Server (NTRS)

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.; Mcgougan, W. R.

1979-01-01

92

Shield For Flexible Pipe  

NASA Technical Reports Server (NTRS)

Cylindrical shield designed to fit around flexible pipe to protect nearby workers from injury and equipment from damage if pipe ruptures. Designed as pressure-relief device. Absorbs impact of debris ejected radially from broken flexible pipe. Also redirects flow of pressurized fluid escaping from broken pipe onto flow path allowing for relief of pressure while minimizing potential for harm.

Ponton, Michael K.; Williford, Clifford B.; Lagen, Nicholas T.

1995-01-01

93

Microwave shielding measurement method  

Microsoft Academic Search

A simple system for measuring the attenuation of microwaves in the frequency range of 700 MHz to 13 GHz is described. It has been used to test a large number of commercially available microwave shielding materials. The standard system for such measurements would require IEEE STD 299 2006. This standard requires a number of different sources and receivers depending on

L. L. Hatfield; B. Schilder

2009-01-01

94

Lightweight blast shield  

DOEpatents

A tandem warhead missile arrangement that has a composite material housing structure with a first warhead mounted at one end and a second warhead mounted near another end of the composite structure with a dome shaped composite material blast shield mounted between the warheads to protect the second warhead from the blast of the first warhead.

Mixon, Larry C. (Madison, AL); Snyder, George W. (Huntsville, AL); Hill, Scott D. (Toney, AL); Johnson, Gregory L. (Decatur, AL); Wlodarski, J. Frank (Huntsville, AL); von Spakovsky, Alexis P. (Huntsville, AL); Emerson, John D. (Arab, AL); Cole, James M. (Huntsville, AL); Tipton, John P. (Huntsville, AL)

1991-01-01

95

A novel shielding material prepared from solid waste containing lead for gamma ray  

NASA Astrophysics Data System (ADS)

Human beings are continuously exposed to cosmogenic radiation and its products in the atmosphere from naturally occurring radioactive materials (NORM) within Earth, their bodies, houses and foods. Especially, for the radiation protection environments where high ionizing radiation levels appear should be shielded. Generally, different materials are used for the radiation shielding in different areas and for different situations. In this study, a novel shielding material produced by a metallurgical solid waste containing lead was analyzed as shielding material for gamma radiation. The photon total mass attenuation coefficients ( ?/ ?) were measured and calculated using WinXCom computer code for the novel shielding material, concrete and lead. Theoretical and experimental values of total mass attenuation coefficient of the each studied sample were compared. Consequently, a new shielding material prepared from the solid waste containing lead could be preferred for buildings as shielding materials against gamma radiation.

Erdem, Mehmet; Baykara, Oktay; Do?ru, Mahmut; Kuluöztürk, Fatih

2010-09-01

96

Light-weight flexible magnetic shields for large-aperture photomultiplier tubes  

NASA Astrophysics Data System (ADS)

Thin flexible sheets of high-permeability FINEMET® foils encased in thin plastic layers have been used to shield various types of 20-cm-diameter photomultiplier tubes from ambient magnetic fields. In the presence of the Earth's magnetic field this type of shielding is shown to increase the collection efficiency of photoelectrons and can improve the uniformity of response of these photomultiplier tubes.

DeVore, P.; Escontrias, D.; Koblesky, T.; Lin, C. J.; Liu, D. W.; Luk, K. B.; Ngan, J.; Peng, J. C.; Polly, C.; Roloff, J.; Steiner, H.; Wang, S.; Wong, J.; Yeh, M.

2014-02-01

97

Artificial neural networks for predicting the maximum surface settlement caused by EPB shield tunneling  

Microsoft Academic Search

Numerous empirical and analytical relations exist between shield tunnel characteristics and surface and subsurface deformation. Also, 2-D and 3-D numerical analyses have been applied to such tunneling problems. Similar but substantially fewer approaches have been developed for earth pressure balance (EPB) tunneling. In the Bangkok MRTA project, data on ground deformation and shield operation were collected. The tunnel sizes are

Suchatvee Suwansawat; Herbert H. Einstein

2006-01-01

98

LOFT. Contextual view of north side of shielded roadway (TAN719) ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

LOFT. Contextual view of north side of shielded roadway (TAN-719) as it looked during use of FET facilities. Camera facing southwest. Sign over door says, "Contained Test Facility." Note earth shielding. Date: March 2004. INEEL negative no. HD-39-3-2 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

99

Aladdin Upgrade Design Study: Shielding.  

National Technical Information Service (NTIS)

The object of this shielding is to examine all aspects of Aladdin operation to ensure that adequate shielding is provided to meet the design objectives. To do this, we will look at shielding necessary for radiation produced during the injection process, d...

P. M. DeLuca R. A. Otte S. W. Schilthelm W. P. Swanson

1985-01-01

100

Solar probe shield developmental testing  

NASA Technical Reports Server (NTRS)

The objectives of the Solar Probe mission and the current status of the Solar Probe thermal shield subsystem development are described. In particular, the discussion includes a brief description of the mission concepts, spacecraft configuration and shield concept, material selection criteria, and the required material testing to provide a database to support the development of the shield system.

Miyake, Robert N.

1991-01-01

101

Primary shield displacement and bowing  

Microsoft Academic Search

The reactor primary shield is constructed of high density concrete and surrounds the reactor core. The inlet, outlet and side primary shields were constructed in-place using 2.54 cm (1 in) thick steel plates as the forms. The plates remained as an integral part of the shields. The elongation of the pressure tubes due to thermal expansion and pressurization is not

1978-01-01

102

Thick Galactic Cosmic Radiation Shielding Using Atmospheric Data  

NASA Technical Reports Server (NTRS)

NASA is concerned with protecting astronauts from the effects of galactic cosmic radiation and has expended substantial effort in the development of computer models to predict the shielding obtained from various materials. However, these models were only developed for shields up to about 120 g!cm2 in thickness and have predicted that shields of this thickness are insufficient to provide adequate protection for extended deep space flights. Consequently, effort is underway to extend the range of these models to thicker shields and experimental data is required to help confirm the resulting code. In this paper empirically obtained effective dose measurements from aircraft flights in the atmosphere are used to obtain the radiation shielding function of the earth's atmosphere, a very thick shield. Obtaining this result required solving an inverse problem and the method for solving it is presented. The results are shown to be in agreement with current code in the ranges where they overlap. These results are then checked and used to predict the radiation dosage under thick shields such as planetary regolith and the atmosphere of Venus.

Youngquist, Robert C.; Nurge, Mark A.; Starr, Stanley O.; Koontz, Steven L.

2013-01-01

103

Capacitive Proximity Sensors With Additional Driven Shields  

NASA Technical Reports Server (NTRS)

Improved capacitive proximity sensors constructed by incorporating one or more additional driven shield(s). Sensitivity and range of sensor altered by adjusting driving signal(s) applied to shield(s). Includes sensing electrode and driven isolating shield that correspond to sensing electrode and driven shield.

Mcconnell, Robert L.

1993-01-01

104

Roof Shield for Advance and Retreat Mining  

NASA Technical Reports Server (NTRS)

Shield sections change their configuration to suit mining mode. Articulation cylinders raise rear shield to advance position, and locking cylinders hold it there. To change to retreat position articulation cylinders lower shield. Locking pins at edge of outermost shield plate latch shield to chock base. Shield accommodates roof heights ranging from 36 to 60 inches (0.9 to 1.52 meters).

Lewis, E. V.

1985-01-01

105

Whipple bumper shield simulations  

SciTech Connect

The Whipple bumper is a space shield designed to protect a space station from the most hazardous orbital space debris environment. A series of numerical simulations has been performed using the multi-dimensional hydrodynamics code CTH to estimate the effectiveness of the thin Whipple bumper design. These simulations are performed for impact velocities of {approximately}10 km/s which are now accessible by experiments using the Sandia hypervelocity launcher facility. For a {approximately}10 km/s impact by a 0.7 gm aluminum flier plate, the experimental results indicate that the debris cloud resulting upon impact of the bumper shield by the flier plate, completely penetrates the sub-structure. The CTH simulations also predict complete penetration by the subsequent debris cloud. 5 refs., 4 figs., 2 tabs.

Hertel, E.S.; Chhabildas, L.C. (Sandia National Labs., Albuquerque, NM (USA)); Hill, S.A. (National Aeronautics and Space Administration, Huntsville, AL (USA). George C. Marshall Space Flight Center)

1991-01-01

106

Visualizing the Shields Parameter  

NSDL National Science Digital Library

This is not so much an activity as it is a useful tool to build an activity around. I created an Excel spreadsheet that calculates the Shields parameter and the grain Reynolds number for a given set of conditions, then plots the resultant values on the Shields diagram. Thus, students can tweak the boundary shear stress value to calculate the stress required to move a given grain size in any fluid, under any gravitational conditions. It is a great way for them to understand how changes in fluid density and viscosity (water vs. air) affect initiation of motion, as well as the effects of grain size. I might use this in a lecture on initiation of motion, asking them to answer some basic questions (see attached example).

Hickson, Tom

107

Gas shielding apparatus  

DOEpatents

An apparatus for preventing oxidation by uniformly distributing inert shielding gas over the weld area of workpieces such as pipes being welded together. The apparatus comprises a chamber and a gas introduction element. The chamber has an annular top wall, an annular bottom wall, an inner side wall and an outer side wall connecting the top and bottom walls. One side wall is a screen and the other has a portion defining an orifice. The gas introduction element has a portion which encloses the orifice and can be one or more pipes. The gas introduction element is in fluid communication with the chamber and introduces inert shielding gas into the chamber. The inert gas leaves the chamber through the screen side wall and is dispersed evenly over the weld area.

Brandt, Daniel (Los Alamos, NM)

1985-01-01

108

Composition for radiation shielding  

DOEpatents

A composition for use as a radiation shield is disclosed. The shield has a depleted uranium core for absorbing gamma rays and a bismuth coating for preventing chemical corrosion and absorbing gamma rays. Alternatively, a sheet of gadolinium may be positioned between the uranium core and the bismuth coating for absorbing neutrons. The composition is preferably in the form of a container for storing materials that emit radiation such as gamma rays and neutrons. The container is preferably formed by casting bismuth around a pre-formed uranium container having a gadolinium sheeting, and allowing the bismuth to cool. The resulting container is a structurally sound, corrosion-resistant, radiation-absorbing container. 2 figs.

Kronberg, J.W.

1994-08-02

109

Shielded Canister Transporter  

Microsoft Academic Search

The Hanford Waste Vitrification Plant (HWVP) will produce canisters filled with high-level radioactive waste immobilized in borosilicate glass. This report discusses a Shielded Canister Transporter (SCT) which will provide the means for safe transportation and handling of the canisters from the Vitrification Building to the Canister Storage Building (CSB). The stainless steel canisters are 0.61 meters in diameter, 3.0 meters

G. G. Jr. Eidem; R. Fages

1993-01-01

110

Ablative shielding for hypervelocity projectiles  

NASA Technical Reports Server (NTRS)

A hypervelocity projectile shield which includes a hollow semi-flexible housing fabricated from a plastic like, or otherwise transparent membrane which is filled with a fluid (gas or liquid) is presented. The housing has a inlet valve, similar to that on a tire or basketball, to introduce an ablating fluid into the housing. The housing is attached by a Velcro mount or double-sided adhesive tape to the outside surface of a structure to be protected. The housings are arrayed in a side-by-side relationship for complete coverage of the surface to be protected. In use, when a hypervelocity projectile penetrates the outer wall of a housing it is broken up and then the projectile is ablated as it travels through the fluid, much like a meteorite 'burns up' as it enters the earth's atmosphere, and the housing is deflated. The deflated housing can be easily spotted for replacement, even from a distance. Replacement is then accomplished by simply pulling a deflated housing off the structure and installing a new housing.

Rucker, Michelle A. (inventor)

1993-01-01

111

Iron shielded MRI optimization  

NASA Astrophysics Data System (ADS)

The design of the main current systems of an actively shielded and of an iron shielded MRI device for nuclear resonance imaging, is considered. The model for the analysis of the magnetic induction produced by the current system, is based on the combination of a Boundary Element technique and of the integration of two Fredholm integral equations of the first and the second kind. The equivalent current magnetization model is used for the calculation of the magnetization produced by the iron shield. High field uniformity in a spherical region inside the device, and a low stray field in the neighborhood of the device are required. In order to meet the design requirements a multi-objective global minimization problem is solved. The minimization method is based on the combination of the filled function technique and the (1+1) evolution strategy algorithm. The multi-objective problem is treated by means of a penalty method. The actively shielded MRI system results to utilize larger amount of conductor and produce higher magnetic energy than the iron shield device. On veut étudier le projet du système des courants principaux d'un MRI à écran en fer et d'un MRI à écran actif. Le modèle d'analyse du champ magnétique produit par le système de courants est basé sur la combinaison d'une technique Boundary Element et de l'intégration de deux équations intégrales de Fredholm de première et de seconde sorte. On utilise pour calculer la magnétisation produite par l'écran en fer le modèle à cou rants de magné ti sa tion équivalents. On exige une élévation uniforme du champ dans une région sphérique au cœur de l'appareil et un bas champ magnétique dispersé à proximité de l'appareil. Dans le but de répondre aux impératifs du projet, on va résoudre un problème multiobjectif de minimisation globale. On utilise une technique de minimisation obtenue par la combinaison des méthodes “Filled Function” et “(1+1) Evolution Strategy”. Le problème multiobjectif est traité avec la méthode des pénalités. Il s'ensuit que le MRI à écran actif utilise une plus grande quantité de conducteur et produit une énergie magnétique plus élevée que le MRI à écran en fer.

Borghi, C. A.; Fabbri, M.

1998-09-01

112

Experimental performance investigation of double-layer shields at power frequency magnetic shielding  

Microsoft Academic Search

Double-layer shields have received attention in magnetic shielding at extremely low frequency. Also, cylindrical shape is one of shielding structures widely used in industry. In this study, cylindrical shaped shields with commonly available and inexpensive materials used for power frequency magnetic field shielding. The magnetic shielding performances are investigated experimentally for single and double-layer shields at power frequencies. The aim

Selim Koroglu; Nurettin Umurkan; Osman Kilic

2008-01-01

113

Novel shielding materials for space and air travel.  

PubMed

The reduction of dose onboard spacecraft and aircraft by appropriate shielding measures plays an essential role in the future development of space exploration and air travel. The design of novel shielding strategies and materials may involve hydrogenous composites, as it is well known that liquid hydrogen is most effective in attenuating charged particle radiation. As precursor for a later flight experiment, the shielding properties of newly developed hydrogen-rich polymers and rare earth-doped high-density rubber were tested in various ground-based neutron and heavy ion fields and compared with aluminium and polyethylene as reference materials. Absorbed dose, average linear energy transfer and gamma-equivalent neutron absorbed dose were determined by means of LiF:Mg,Ti thermoluminescence dosemeters and CR-39 plastic nuclear track detectors. First results for samples of equal aerial density indicate that selected hydrogen-rich plastics and rare-earth-doped rubber may be more effective in attenuating cosmic rays by up to 10% compared with conventional aluminium shielding. The appropriate adaptation of shielding thicknesses may thus allow reducing the biologically relevant dose. Owing to the lower density of the plastic composites, mass savings shall result in a significant reduction of launch costs. The experiment was flown as part of the European Space Agency's Biopan-5 mission in May 2005. PMID:16717109

Vana, N; Hajek, M; Berger, T; Fugger, M; Hofmann, P

2006-01-01

114

Measurement of the transient shielding effectiveness of shielding cabinets  

NASA Astrophysics Data System (ADS)

Recently, new definitions of shielding effectiveness (SE) for high-frequency and transient electromagnetic fields were introduced by Klinkenbusch (2005). Analytical results were shown for closed as well as for non closed cylindrical shields. In the present work, the shielding performance of different shielding cabinets is investigated by means of numerical simulations and measurements inside a fully anechoic chamber and a GTEM-cell. For the GTEM-cell-measurements, a downscaled model of the shielding cabinet is used. For the simulations, the numerical tools CONCEPT II and COMSOL MULTIPHYSICS were available. The numerical results agree well with the measurements. They can be used to interpret the behaviour of the shielding effectiveness of enclosures as function of frequency. From the measurement of the electric and magnetic fields with and without the enclosure in place, the electric and magnetic shielding effectiveness as well as the transient shielding effectiveness of the enclosure are calculated. The transient SE of four different shielding cabinets is determined and discussed.

Herlemann, H.; Koch, M.

2008-05-01

115

Radiation shielding quality assurance  

NASA Astrophysics Data System (ADS)

For the radiation shielding quality assurance, the validity and reliability of the neutron transport code MCNP, which is now one of the most widely used radiation shielding analysis codes, were checked with lot of benchmark experiments. And also as a practical example, follows were performed in this thesis. One integral neutron transport experiment to measure the effect of neutron streaming in iron and void was performed with Dog-Legged Void Assembly in Knolls Atomic Power Laboratory in 1991. Neutron flux was measured six different places with the methane detectors and a BF-3 detector. The main purpose of the measurements was to provide benchmark against which various neutron transport calculation tools could be compared. Those data were used in verification of Monte Carlo Neutron & Photon Transport Code, MCNP, with the modeling for that. Experimental results and calculation results were compared in both ways, as the total integrated value of neutron fluxes along neutron energy range from 10 KeV to 2 MeV and as the neutron spectrum along with neutron energy range. Both results are well matched with the statistical error +/-20%. MCNP results were also compared with those of TORT, a three dimensional discrete ordinates code which was developed by Oak Ridge National Laboratory. MCNP results are superior to the TORT results at all detector places except one. This means that MCNP is proved as a very powerful tool for the analysis of neutron transport through iron & air and further it could be used as a powerful tool for the radiation shielding analysis. For one application of the analysis of variance (ANOVA) to neutron and gamma transport problems, uncertainties for the calculated values of critical K were evaluated as in the ANOVA on statistical data.

Um, Dallsun

116

Exploring the Feasibility of Electrostatic Shielding for Spacecrafts  

NASA Technical Reports Server (NTRS)

NASA is moving forward towards the agency's new vision for space exploration in the 21st Century encompassing a broad range of human and robotic missions including missions to Moon, Mars and beyond. Exposure from the hazards of severe space radiation in deep space long duration missions is the show stopper. Langley has developed state-of-the-art radiation protection and shielding technology for space missions. The payload penalty demands a very stringent requirement on the design of the spacecrafts for human deep space missions. The exploration beyond low Earth orbit (LEO) to enable routine access to more interesting regions of space will require protection from the hazards of the accumulated exposures of space radiation, Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE), and minimizing the production of secondary radiation is a great advantage. There is a need to look to new horizons for newer technologies. The present investigation explores the feasibility of using electrostatic shielding in concert with innovative materials shielding and protection technologies. The asymmetries of the radiation shielding problem would be exploited in the electrostatics shielding process. The goal is to repel enough positive charge ions so that they miss the spacecraft without attracting thermal electrons. Conclusions are drawn about the advantages the electrostatic shielding, should it be successful, would bring to the radiation protection design process.

Tripathi, R. K.; Wilson, J. W.; Youngquist, R. C.

2005-01-01

117

Removable cleanable antireflection shield  

NASA Astrophysics Data System (ADS)

A replaceable anti-reflection shield for the glare surface beneath the windscreen an aircraft is described which comprises a flexible panel of light absorbing material, such as black cloth, velvet, canvas or plastic, of size and configuration corresponding to that of the glare surface for placement on and conformance to the contour of the glare surface beneath the windscreen, and peripheral attaching means such as adhesive strips, snaps. Velcro strips, suction cups, or similar devices, on the flexible panel for detachably securing the peripheral edges of the panel to the glare surface. Whereby the panel is easily removed for cleaning or replacement.

Task, H. L.

1985-01-01

118

Spacecraft ceramic protective shield  

NASA Technical Reports Server (NTRS)

A low areal density protective shield apparatus, and method for making same, for protecting spacecraft structures from impact with hypervelocity objects, including a bumper member comprising a bumper ceramic layer, a bumper shock attenuator layer, and a bumper confining layer. The bumper ceramic layer can be SiC or B.sub.4 C; the bumper shock attenuator layer can be zirconia felt; and the bumper confining layer can be aluminum. A base armor member can be spaced from the bumper member and a ceramic fiber-based curtain can be positioned between the bumper and base armor members.

Larriva, Rene F. (Inventor); Nelson, Anne (M.); Czechanski, James G. (Inventor); Poff, Ray E. (Inventor)

1995-01-01

119

Heat Shields for Aerobrakes  

NASA Technical Reports Server (NTRS)

Performances of three types of heat protectors predicted. Estimates of expected performances of heat shields for conical drag brake presented in paper. Drag brakes, or aerobrakes, being considered as devices for slowing space vehicles when they return to Space Shuttle altitudes from higher satellite altitudes after supply missions. Aerobrakes add less weight than do retro-rockets for same purpose and consume no fuel. Paper provides general information on sensitivity of performance to thermal and physical properties of materials used in aerobrakes. Information useful to both designers of brakes and developers of materials for brake fabrication on aerospace structures.

Pitts, W. C.; Murbach, M. S.

1987-01-01

120

Shielding effects in ceramic superconductors  

Microsoft Academic Search

The shielding properties of high-temperature superconductors in DC and AC magnetic fields are discussed using Bean's critical-state model and models, which account for the field dependence of the critical current density. Experimental work on the shielding properties of superconducting YBa2Cu3O7-delta and conductive (aluminum and cooper) screens is presented. The maximum value of the shielded field for YBa2Cu3O7-delta\\/Ag screens was measured

Halina Niculescu; Rainer Schmidmeier; Betina Topolski; Peter J. Gielisse

1994-01-01

121

Effects of shields on cables  

NASA Technical Reports Server (NTRS)

Aircraft wiring subjected to rapidly changing electromagnetic fields was considered. The ways in which shielded cables reduce surge voltages were studied along with the ways in which common practice regarding the use of shields may be at variance with the use required for the control of lightning effects. Courses in which this apparent conflict of use may be resolved were suggested. Noise currents flowing on shields of cables related to the noise signals coupled onto signal conductors were also investigated.

1977-01-01

122

Hypervelocity impact shield  

NASA Technical Reports Server (NTRS)

A hypervelocity impact shield and method for protecting a wall structure, such as a spacecraft wall, from impact with particles of debris having densities of about 2.7 g/cu cm and impact velocities up to 16 km/s are disclosed. The shield comprises a stack of ultra thin sheets of impactor disrupting material supported and arranged by support means in spaced relationship to one another and mounted to cover the wall in a position for intercepting the particles. The sheets are of a number and spacing such that the impacting particle and the resulting particulates of the impacting particle and sheet material are successively impact-shocked to a thermal state of total melt and/or vaporization to a degree as precludes perforation of the wall. The ratio of individual sheet thickness to the theoretical diameter of particles of debris which may be of spherical form is in the range of 0.03 to 0.05. The spacing between adjacent sheets is such that the debris cloud plume of liquid and vapor resulting from an impacting particle penetrating a sheet does not puncture the next adjacent sheet prior to the arrival thereat of fragment particulates of sheet material and the debris particle produced by a previous impact.

Cour-Palais, Burton G. (inventor); Crews, Jeanne Lee (inventor)

1991-01-01

123

Shielded enclosures for experimental studies of shielding topology  

Microsoft Academic Search

The report discusses the effort to provide shielded enclosures for EMP experimental studies of shielding topology. Section 1 discusses the theoretical modeling for which scattering matrices of subshields and their norms are used to relate the internal signals to the electromagnetic source environment. Both the line and aperture penetrations are included in the scattering matrix formulation. Experimental and analytical methods

F. C. Yang; K. S. H. Lee; S. A. Kokorowski; C. E. Baum; J. Hamm; W. Graf; E. F. Vance

1984-01-01

124

PBF Cubicle 13. Shield wall details illustrate shielding technique of ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

PBF Cubicle 13. Shield wall details illustrate shielding technique of stepped penetrations and brick layout scheme for valve stem extension sleeve. Aerojet Nuclear Company. Date: May 1976. INEEL index no. 761-0620-00-400-195280 - Idaho National Engineering Laboratory, SPERT-I & Power Burst Facility Area, Scoville, Butte County, ID

125

Shield Defense of a Larval Tortoise Beetle  

Microsoft Academic Search

Larvae of the folivorous tortoise beetle, Plagiometriona clavata, carry shields formed from feces and exuviae above their bodies. We used an ecologically relevant predatory ant, Formica subsericea, in a bioassay to determine if shields functioned as simple barriers, as previous studies indicated, or whether they were chemical defenses. Shields were necessary for larval survival; shield removal rendered larvae vulnerable. Shields

Fredric V. Vencl; Timothy C. Morton; Ralph O. Mumma; Jack C. Schultz

1999-01-01

126

Enhanced meteoroid and orbital debris shielding  

Microsoft Academic Search

An innovative, low-weight shield system has been developed by NASA Johnson Space Center (JSC) and Marshall Space Flight Center (MSFC) engineers to enhance the protection of conventional Whipple shields. This shield, the “Stuffed Whipple” shield, includes a flexible blanket combining Nextel™ ceramic fabric and Kevlar™ fabric (or “stuffing”) between the aluminum bumper and rear wall of a Whipple shield. The

E. L. Christiansen; J. L. Crews; J. E. Williamsen; J. H. Robinson; A. M. Nolen

1995-01-01

127

Planet Earth Set to Broil: Thermal Radiation from Chicxulub Ejecta Reentry  

NASA Astrophysics Data System (ADS)

We model the thermal radiation transfer due to the atmospheric reentry of hypervelocity Chicxulub impact ejecta. Self-shielding of downward radiation by the spherules limits the magnitude and duration of the thermal pulse at the Earth’s surface.

Goldin, T. J.; Melosh, H. J.

2009-03-01

128

Electroless techniques for EMI shieldings  

Microsoft Academic Search

This paper discusses the progress made in electroless plating techniques for fabrication of EMI shieldings. Although, there are alternative techniques such as zinc arc spray, Cu or Ni conductive paints and RF\\/magnetron sputtering for deposition of conductive coatings on plastics, electroless techniques have advantage of better uniformity and adhesivity of coatings as well as higher shielding effectiveness. However, these techniques

L. G. Bhatgadde; S. Joseph

1997-01-01

129

Reflective Shields for Artificial Satellites  

NASA Technical Reports Server (NTRS)

Report proposes reflective shield that protects spacecraft from radiant energy. Also gives some protection against particle beams and cosmic rays. Conceptual shield essentially advanced version of decorative multifaceted mirror balls often hung over dance floors. Mirror facets disperse radiant energy in many directions.

Bouquet, F. L.

1986-01-01

130

Radiation Shielding Optimization on Mars  

NASA Technical Reports Server (NTRS)

Future space missions to Mars will require radiation shielding to be optimized for deep space transit and an extended stay on the surface. In deep space, increased shielding levels and material optimization will reduce the exposure from most solar particle events (SPE) but are less effective at shielding against galactic cosmic rays (GCR). On the surface, the shielding provided by the Martian atmosphere greatly reduces the exposure from most SPE, and long-term GCR exposure is a primary concern. Previous work has shown that in deep space, additional shielding of common materials such as aluminum or polyethylene does not significantly reduce the GCR exposure. In this work, it is shown that on the Martian surface, almost any amount of aluminum shielding increases exposure levels for humans. The increased exposure levels are attributed to neutron production in the shield and Martian regolith as well as the electromagnetic cascade induced in the Martian atmosphere. This result is significant for optimization of vehicle and shield designs intended for the surface of Mars.

Slaba, Tony C.; Mertens, Chris J.; Blattnig, Steve R.

2013-01-01

131

Lunar Surface Reactor Shielding Study  

Microsoft Academic Search

A nuclear reactor system could provide power to support long term human exploration of the moon. Such a system would require shielding to protect astronauts from its emitted radiations. Shielding studies have been performed for a Gas Cooled Reactor system because it is considered to be the most suitable nuclear reactor system available for lunar exploration, based on its tolerance

Shawn Kang; Ronald Lipinski; William McAlpine

2006-01-01

132

A Radiation Shielding Code for Spacecraft and Its Validation  

NASA Technical Reports Server (NTRS)

The HZETRN code, which uses a deterministic approach pioneered at NASA Langley Research Center, has been developed over the past decade to evaluate the local radiation fields within sensitive materials (electronic devices and human tissue) on spacecraft in the space environment. The code describes the interactions of shield materials with the incident galactic cosmic rays, trapped protons, or energetic protons from solar particle events in free space and low Earth orbit. The content of incident radiations is modified by atomic and nuclear reactions with the spacecraft and radiation shield materials. High-energy heavy ions are fragmented into less massive reaction products, and reaction products are produced by direct knockout of shield constituents or from de-excitation products. An overview of the computational procedures and database which describe these interactions is given. Validation of the code with recent Monte Carlo benchmarks, and laboratory and flight measurement is also included.

Shinn, J. L.; Cucinotta, F. A.; Singleterry, R. C.; Wilson, J. W.; Badavi, F. F.; Badhwar, G. D.; Miller, J.; Zeitlin, C.; Heilbronn, L.; Tripathi, R. K.

2000-01-01

133

Galactic cosmic ray abundances and spectra behind defined shielding.  

PubMed

LET spectra have been measured for lunar missions and for several near Earth orbits ranging from 28 degrees to 83 degrees inclination. In some of the experiments the flux of GCR was determined separately from contributions caused by interactions in the detector material. Results of these experiments are compared to model calculations. The general agreement justifies the use of the model to calculate GCR fluxes. The magnitude of variations caused by solar modulation, geomagnetic shielding, and shielding by matter determined from calculated LET spectra is generally in agreement with experimental data. However, more detailed investigations show that there are some weak points in modeling solar modulation and shielding by material. These points are discussed in more detail. PMID:11540030

Heinrich, W; Benton, E V; Wiegel, B; Zens, R; Rusch, G

1994-10-01

134

Silica heat shield sizing  

NASA Technical Reports Server (NTRS)

The sensitivity of silica heat shield requirements to gap width, tile edge radius, and heat transfer distribution within tile gaps was investigated. A two-dimensional thermal model was modified and used to determine the effect of two dimensional heat transfer distributions at high temperature reusable surface insulation edges on shuttle thermal protection system (TPS) requirements. The sensitivity of TPS requirements to coating thickness, emissivity, substructure thickness, and changes in gap heating for several locations on shuttle was also studied. An inverse solution technique was applied to temperature data obtained in the Ames 20 MW turbulent duct in order to examine the effect of tile edge radius on TPS requirements. The derived heating values were then used to predict TPS requirements. Results show that increasing tile radius reduces TPS requirements.

Ebbesmeyer, L. H.; Christensen, H. E.

1975-01-01

135

Portable convertible blast effects shield  

DOEpatents

A rapidly deployable portable convertible blast effects shield/ballistic shield includes a set two or more telescoping cylindrical rings operably connected to each other to convert between a telescopically-collapsed configuration for storage and transport, and a telescopically-extended upright configuration forming an expanded inner volume. In a first embodiment, the upright configuration provides blast effects shielding, such as against blast pressures, shrapnel, and/or fire balls. And in a second embodiment, the upright configuration provides ballistic shielding, such as against incoming weapons fire, shrapnel, etc. Each ring has a high-strength material construction, such as a composite fiber and matrix material, capable of substantially inhibiting blast effects and impinging projectiles from passing through the shield. And the set of rings are releasably securable to each other in the telescopically-extended upright configuration, such as by click locks.

Pastrnak, John W. (Livermore, CA); Hollaway, Rocky (Modesto, CA); Henning, Carl D. (Livermore, CA); Deteresa, Steve (Livermore, CA); Grundler, Walter (Hayward, CA); Hagler,; Lisle B. (Berkeley, CA); Kokko, Edwin (Dublin, CA); Switzer, Vernon A (Livermore, CA)

2010-10-26

136

Portable convertible blast effects shield  

DOEpatents

A rapidly deployable portable convertible blast effects shield/ballistic shield includes a set two or more telescoping cylindrical rings operably connected to each other to convert between a telescopically-collapsed configuration for storage and transport, and a telescopically-extended upright configuration forming an expanded inner volume. In a first embodiment, the upright configuration provides blast effects shielding, such as against blast pressures, shrapnel, and/or fire balls. And in a second embodiment, the upright configuration provides ballistic shielding, such as against incoming weapons fire, shrapnel, etc. Each ring has a high-strength material construction, such as a composite fiber and matrix material, capable of substantially inhibiting blast effects and impinging projectiles from passing through the shield. And the set of rings are releasably securable to each other in the telescopically-extended upright configuration, such as by click locks.

Pastrnak, John W. (Livermore, CA); Hollaway, Rocky (Modesto, CA); Henning, Carl D. (Livermore, CA); Deteresa, Steve (Livermore, CA); Grundler, Walter (Hayward, CA); Hagler, Lisle B. (Berkeley, CA); Kokko, Edwin (Dublin, CA); Switzer, Vernon A (Livermore, CA)

2007-05-22

137

Portable convertible blast effects shield  

DOEpatents

A rapidly deployable portable convertible blast effects shield/ballistic shield includes a set two or more frusto-conically-tapered telescoping rings operably connected to each other to convert between a telescopically-collapsed configuration for storage and transport, and a telescopically-extended upright configuration forming an expanded inner volume. In a first embodiment, the upright configuration provides blast effects shielding, such as against blast pressures, shrapnel, and/or fire balls. And in a second embodiment, the upright configuration provides ballistic shielding, such as against incoming weapons fire, shrapnel, etc. Each ring has a high-strength material construction, such as a composite fiber and matrix material, capable of substantially inhibiting blast effects and impinging projectiles from passing through the shield. And the set of rings are releasably securable to each other in the telescopically-extended upright configuration by the friction fit of adjacent pairs of frusto-conically-tapered rings to each other.

Pastrnak, John W. (Livermore, CA); Hollaway, Rocky (Modesto, CA); Henning, Carl D. (Livermore, CA); Deteresa, Steve (Livermore, CA); Grundler, Walter (Hayward, CA); Hagler, Lisle B. (Berkeley, CA); Kokko, Edwin (Dublin, CA); Switzer, Vernon A. (Livermore, CA)

2011-03-15

138

Aladdin upgrade design study: shielding  

SciTech Connect

The object of this shielding is to examine all aspects of Aladdin operation to ensure that adequate shielding is provided to meet the design objectives. To do this, we will look at shielding necessary for radiation produced during the injection process, during normal loss of the stored beam and during accidental loss of the stored beam. It will therefore be necessary to specify shielding not only at the ring, but also along the injection line and the optical beam lines. We will also give special attention to the occupation of the accelerator Vault during injection as this may be a desirable design option. In effect, two shielding plans will be presented, permitting estimates of cost and space requirements for both.

Swanson, W.P.; DeLuca, P.M. Jr.; Otte, R.A.; Schilthelm, S.W.

1985-04-23

139

Welding shield for coupling heaters  

DOEpatents

Systems for coupling end portions of two elongated heater portions and methods of using such systems to treat a subsurface formation are described herein. A system may include a holding system configured to hold end portions of the two elongated heater portions so that the end portions are abutted together or located near each other; a shield for enclosing the end portions, and one or more inert gas inlets configured to provide at least one inert gas to flush the system with inert gas during welding of the end portions. The shield may be configured to inhibit oxidation during welding that joins the end portions together. The shield may include a hinged door that, when closed, is configured to at least partially isolate the interior of the shield from the atmosphere. The hinged door, when open, is configured to allow access to the interior of the shield.

Menotti, James Louis (Dickinson, TX)

2010-03-09

140

Analytic Ballistic Performance Model of Whipple Shields  

NASA Technical Reports Server (NTRS)

The dual-wall Whipple shield is the shield of choice for lightweight, long-duration flight. The shield uses an initial sacrificial wall to initiate fragmentation and melt an impacting threat that expands over a void before hitting a subsequent shield wall of a critical component. The key parameters to this type of shield are the rear wall and its mass which stops the debris, as well as the minimum pressure generated under threat particle impact of the sacrificial wall and the amount of void that is available for expansion. Ensuring the minimum pressure is sufficiently high to achieve large scale fragmentation/melt of the threat particle enables the expansion of the threat and reduces the momentum flux of the debris on the rear wall. Three key factors in the minimum pressure achieved are the thickness of the sacrificial wall relative to the characteristic dimension of the impacting particle, the density and material cohesion contrast of the sacrificial wall relative to the threat particle and the impact speed. The mass of the rear wall and the sacrificial wall are desirable to minimize for launch costs and dynamic concerns making it important to have an understanding of the effects of density contrast and impact speed. In this paper a fourth key parameter is identified related to fragmentation, which corresponds to the ratio of the size of the projectile relative to the transition from brittle to ductile hole growth in the projectile. Ballistic limit equations have been developed to define the failure limits of a MMOD shield, generally in terms of projectile diameter (or mass), impact velocity, and angle. Within the range of impact velocities relevant for Earth-orbiting spacecraft, three distinct regions of penetration phenomenology have been identified for Whipple shields: center dot Low velocity: the projectile is eroded (and possibly deformed) during its passage through the bumper plate, but is not fragmented. Thus, perforation of the rear wall is by a fragment with a mass and speed equal to or less than the original impactor. center dot Intermediate (shatter) velocity: impact velocities are sufficient to induce projectile fragmentation upon impact with the bumper plate, resulting in a coarse debris cloud with large solid fragments. Increasing velocity within the shatter regime results in increased fragmentation, and eventually melting, of the projectile and bumper fragments, generating a finer and more evenly dispersed debris cloud. Failure of the rear wall is a complicated combination of modes observed at low- and hypervelocity. center dot Hypervelocity: the projectile and holed-out bumper material is completely, or nearly completely, melted and/or vaporized by the initial impact. The resultant debris cloud impacts over a dispersed area of the rear wall, loading it impulsively and inducing failure through rupture or petalling. While each of these regimes are well observed with extensive empirical methods to describe these regions, differences in impactor materials, configurations of shields and questions about the limitations of the attainable impact speeds have left questions that are difficult to answer from completely empirical methods.

Miller, J. E.; Bjorkman, M. D.; Christiansen, E. L.; Ryan, S. J.

2014-01-01

141

Performance of solar shields. [Skylab 1 micrometeoroid shield difficulties  

NASA Technical Reports Server (NTRS)

The loss of the micrometeoroid shield from the Orbital Workshop section of Skylab 1 about 63 seconds after lift-off, was the catalyst for a prodigious effort to develop a substitute for the passive portion of the thermal control system. An intensive effort is described in which numerous potential thermal shield materials were assessed, and during which period ten specific shield designs were developed and carried through various stages of development and test. Thermal shield materials data are discussed, including optical, strength, fatigue, outgassing, tackiness, ultraviolet radiation, and material memory properties. Specifically addressed are thermal shield materials selection criteria and the design, development, and test requirements associated with the successful development of Skylab thermal shields, and specifically the two thermal shields subsequently deployed over the exposed gold foil skin of the Orbital Workshop. Also considered are the general performance and thermal improvements provided by both the parasol design deployed by the Skylab 1 crew, and the sail design deployed by the Skylab 2 crew.

Schwinghamer, R. J.

1974-01-01

142

Preliminary design of magnetic shielding by FEM  

SciTech Connect

In this paper, the authors propose an optimization method for magnetic shielding. The main purpose is the weight reduction of shield material. Assuming that the permeability of shield material is infinite, they simplify the magnetic shielding problem. Under this assumption, they design optimal passage for magnetic flux through the shield. They apply this method to designing the magnetic shielding for Maglev and show the effectiveness of this method by experimental and numerical data.

Sasakawa, Takashi; Tagawa, Naoto; Herai, Toshiki; Tomita, Masaru [Railway Technical Research Inst., Kokubunji, Tokyo (Japan)] [Railway Technical Research Inst., Kokubunji, Tokyo (Japan)

1997-03-01

143

Lunar Surface Reactor Shielding Study  

NASA Astrophysics Data System (ADS)

A nuclear reactor system could provide power to support long term human exploration of the moon. Such a system would require shielding to protect astronauts from its emitted radiations. Shielding studies have been performed for a Gas Cooled Reactor system because it is considered to be the most suitable nuclear reactor system available for lunar exploration, based on its tolerance of oxidizing lunar regolith and its good conversion efficiency. The goals of the shielding studies were to determine a material shielding configuration that reduces the dose (rem) to the required level in order to protect astronauts, and to estimate the mass of regolith that would provide an equivalent protective effect if it were used as the shielding material. All calculations were performed using MCNPX, a Monte Carlo transport code. Lithium hydride must be kept between 600 K and 700 K to prevent excessive swelling from large amounts of gamma or neutron irradiation. The issue is that radiation damage causes separation of the lithium and the hydrogen, resulting in lithium metal and hydrogen gas. The proposed design uses a layer of B4C to reduce the combined neutron and gamma dose to below 0.5Grads before the LiH is introduced. Below 0.5Grads the swelling in LiH is small (less than about 1%) for all temperatures. This approach causes the shield to be heavier than if the B4C were replaced by LiH, but it makes the shield much more robust and reliable.

Kang, Shawn; Lipinski, Ronald; McAlpine, William

2006-01-01

144

The solar probe shield\\/antenna materials characterization  

Microsoft Academic Search

This paper describes the development process used to select the shield\\/antenna material satisfying the design requirements of the Solar Probe mission that will encounter a flux at perihelion equivalent to an intensity of 3000 times greater than that at the Earth. A joint U.S.–French testing program was devised that would screen samples of carbon–carbon to determine the fabrication process that

J. Randolph; J. Ayon; R. Dirling; W. Imbriale; R. Miyake; D. Le Queau; G. Olalde; E. Pierson; S. Rawal; B. Rivoire; J. F. Robert; C. Royere; R. Taylor; P. Valentine; W. Vaughn

1999-01-01

145

Radiation Exposure Effects and Shielding Analysis of Carbon Nanotube Materials  

NASA Technical Reports Server (NTRS)

Carbon nanotube materials promise to be the basis for a variety of emerging technologies with aerospace applications. Potential applications to human space flight include spacecraft shielding, hydrogen storage, structures and fixtures and nano-electronics. Appropriate risk analysis on the properties of nanotube materials is essential for future mission safety. Along with other environmental hazards, materials used in space flight encounter a hostile radiation environment for all mission profiles, from low earth orbit to interplanetary space.

Wilkins, Richard; Armendariz, Lupita (Technical Monitor)

2002-01-01

146

A Brief History of Meteoroid and Orbital Debris Shielding Technology for US Manned Spacecraft  

NASA Technical Reports Server (NTRS)

Meteoroid and orbital debris shielding has played an important role from the beginning of manned spaceflight. During the early 60 s, meteoroid protection drove requirements for new meteor and micrometeoroid impact science. Meteoroid protection also stimulated advances in the technology of hypervelocity impact launchers and impact damage assessment methodologies. The first phase of meteoroid shielding assessments closed in the early 70 s with the end of the Apollo program. The second phase of meteoroid protection technology began in the early 80 s when it was determined that there is a manmade Earth orbital debris belt that poses a significant risk to LEO manned spacecraft. The severity of the Earth orbital debris environment has dictated changes in Space Shuttle and ISS operations as well as driven advances in shielding technology and assessment methodologies. A timeline of shielding technology and assessment methodology advances is presented along with a summary of risk assessment results.

Bjorkman, Michael D.; Hyde, James L.

2008-01-01

147

Hubble Space Telescope Bi-Stem Thermal Shield Analyses  

NASA Technical Reports Server (NTRS)

The Hubble Space Telescope (HST) was launched April 24, 1990, and was deployed April 25 into low Earth orbit (LEO). It was soon discovered that the metal poles holding the solar arrays were expanding and contracting as the telescope orbited the Earth passing between the sunlight and the Earth s shadow. The expansion and contraction, although very small, was enough to cause the telescope to shake because of thermal-induced jitters, a detrimental effect when trying to take pictures millions of miles away. Therefore, the European Space Agency (ESA, the provider of the solar arrays) built new solar arrays (SA-11) that contained bi-stem thermal shields which insulated the solar array metal poles. These thermal shields were made of 2 mil thick aluminized-Teflon fluorinated ethylene propylene (FEP) rings fused together into a circular bellows shape. The new solar arrays were put on the HST during an extravehicular activity (EVA), also called an astronaut space walk, during the first servicing mission (SM1) in December 1993. An on-orbit photograph of the HST with the SA-11, and a close up of the bellows-like structure of the thermal shields is provided in Figure 1.

Finlay, Katherine A.

2004-01-01

148

Computational model for the simulation of the shield tunneling process in cohesive soils  

Microsoft Academic Search

A two-dimensional computational model is developed here in order to simulate the continuous advance of the Earth Pressure Balance (EPB) Shield during the tunneling process in cohesive soils. The model is based on the combination of the plane strain transverse-longitudinal sections that can incorporate the three-dimensional deformation of the soil around and ahead of the shield face. This model is

Murad Y. Abu-Farsakh; George Z. Voyiadjis

1999-01-01

149

Radiation shielding for neutron guides  

NASA Astrophysics Data System (ADS)

Models of the neutron guide shielding for the out of bunker guides on the thermal and cold neutron beam lines of the OPAL Reactor (ANSTO) were constructed using the Monte Carlo code MCNP 4B. The neutrons that were not reflected inside the guides but were absorbed by the supermirror (SM) layers were noted to be a significant source of gammas. Gammas also arise from neutrons absorbed by the B, Si, Na and K contained in the glass. The proposed shielding design has produced compact shielding assemblies. These arrangements are consistent with safety requirements, floor load limits, and cost constraints. To verify the design a prototype was assembled consisting of 120 mm thick Pb(96%)Sb(4%) walls resting on a concrete block. There was good agreement between experimental measurements and calculated dose rates for bulk shield regions.

Ersez, T.; Braoudakis, G.; Osborn, J. C.

2006-11-01

150

SNF shipping cask shielding analysis  

SciTech Connect

The Waste Management and Remedial Action Division has planned a modification sequence for storage facility 7827 in the Solid Waste Storage Area (SWSA). The modification cycle is: (1) modify an empty caisson, (2) transfer the spent nuclear fuel (SNF) of an occupied caisson to a hot cell in building 3525 for inspection and possible repackaging, and (3) return the package to the modified caisson in the SWSA. Although the SNF to be moved is in the solid form, it has different levels of activity. Thus, the following 5 shipping casks will be available for the task: the Loop Transport Carrier, the In- Pile Loop LITR HB-2 Carrier, the 6.5-inch HRLEL Carrier, the HFIR Hot Scrap Carrier, and the 10-inch ORR Experiment Removal Shield Cask. This report describes the shielding tasks for the 5 casks: determination of shielding characteristics, any streaming avenues, estimation of thermal limits, and shielding calculational uncertainty for use in the transportation plan.

Johnson, J.O.; Pace, J.V. III

1996-01-01

151

Radiation Distributions for Shielding Calculations.  

National Technical Information Service (NTIS)

Sensitivity studies have indicated that representative neutron and secondary gamma-ray energy and angle distributions can be used for structure shielding analysis thereby eliminating the need for extensive transport calculations using many sources. A revi...

L. G. Mooney

1972-01-01

152

Integral Face Shield Concept for Firefighter's Helmet  

NASA Technical Reports Server (NTRS)

Stowable face shield could be made integral part of helmet worn by firefighters. Shield, made from same tough clear plastic as removable face shields presently used, would be pivoted at temples to slide up inside helmet when not needed. Stowable face shield, being stored in helmet, is always available, ready for use, and is protected when not being used.

Abeles, F.; Hansberry, E.; Himel, V.

1982-01-01

153

Magnetic shielding for magnetically levitated vehicles  

Microsoft Academic Search

The magnetic shielding required for magnetically levitated vehicles is discussed. Shielding is needed to protect passengers in a vehicle from stray dc magnetic fields coming from the superconducting dipoles carried by the vehicle. In addition, the superconducting dipoles must be shielded against various ac magnetic fields. Here we consider shielding of ac magnetic fields generated by the propulsion windings for

YUKIKAZU IWASA; Francis Bitter

1973-01-01

154

Magnetic Shield for Adiabatic Demagnetization Refrigerators (ADR)  

NASA Technical Reports Server (NTRS)

A new method was developed for creating a less expensive shield for ADRs using 1018 carbon steel. This shield has been designed to have similar performance to the expensive vanadium permendur shields, but the cost is 30 to 50% less. Also, these shields can be stocked in a variety of sizes, eliminating the need for special forgings, which also greatly reduces cost.

Chui, Talso C.; Haddad, Nicolas E.

2013-01-01

155

Numerical Approach for Computation of Electromagnetic Shielding  

NASA Astrophysics Data System (ADS)

Disturbing magnetic field (so-called magnetic smog) can be in certain areas suppressed by shielding jacket. Disturbing field is possible to be "lead away" from the shielded area with the use of jacket made of materials with high magnetic permeability (so-called passive shielding, or flux-entrapment shielding). If the disturbing field is time-variable, eddy currents are induced into electrically conductive jacket. Magnetic field generated by these eddy currents suppress the disturbing field (this is called active shielding, or lossy magnetic shielding). Both of these principles can be applied altogether (this is called combined shielding). Presented paper states numerical approach to shielding jacket design and is an introduction to following solution of a real problem of magnetic shielding when the disturbing magnetic field is space-time complicated. Effective design of the magnetic shielding should then be formulated as an optimization task.

Mayer, Daniel; Ulrych, Bohuš

2013-06-01

156

Shielding effectiveness of copper-clad steel materials for communications shielding  

Microsoft Academic Search

The objective of this paper is to determine the shielding effectiveness of copper-clad stainless steel shields in order to compare their performance with other conventional shield materials such as pure copper, copper alloys, and copolymer coated aluminum. A short review of a number of techniques for measuring shielding effectiveness of cable shielding is given. The techniques selected for this paper

O. M. Salati; R. Raman

1986-01-01

157

Evaluation of solders for superconducting magnetic shield  

SciTech Connect

This paper reports on magnetic shield with superconducting winding studied aiming at the practical application of the shield in a magnetic field of higher than 3T. Tubular magnetic shields have been fabricated with superconducting winding using NbTi multifilamentary composite wires. The shields were impregnated with two kinds of solders (wood's metal and indium) to make the electric joint between the wires. The characteristics of the shields are thought to be controlled predominantly by the quality of the solder.

Seo, K.; Nishijima, S.; Katagiri, K.; Okada, T. (ISIR Osaka Univ., Mihogaoka, Ibaraki, Osaka 567 (JP))

1991-03-01

158

Radiation Shielding Materials and Containers Incorporating Same  

DOEpatents

An improved radiation shielding material and storage systems for radioactive materials incorporating the same. The PYRolytic Uranium Compound (''PYRUC'') shielding material is preferably formed by heat and/or pressure treatment of a precursor material comprising microspheres of a uranium compound, such as uranium dioxide or uranium carbide, and a suitable binder. The PYRUC shielding material provides improved radiation shielding, thermal characteristic, cost and ease of use in comparison with other shielding materials. The shielding material can be used to form containment systems, container vessels, shielding structures, and containment storage areas, all of which can be used to house radioactive waste. The preferred shielding system is in the form of a container for storage, transportation, and disposal of radioactive waste. In addition, improved methods for preparing uranium dioxide and uranium carbide microspheres for use in the radiation shielding materials are also provided.

Mirsky, Steven M.; Krill, Stephen J.; and Murray, Alexander P.

2005-11-01

159

Trailer shield assembly for a welding torch  

NASA Technical Reports Server (NTRS)

This invention relates generally to trailer shields for gas shielded arc welding torches, and more particularly to a trailer shield assembly provided with a shield gas manifold for providing an even dispersion of shield gas to the interior of the shield assembly, which generally encloses a joint being welded and a welding trailing portion of hot welded metal. The novelty of the invention lies in providing trailer shield with a manifold tube having a plurality of openings from which shield gas is distributed. A gas manifold region ahead of the torch is also provided with shield gas from a tube to protect metal preheated by the torch. Further novelty lies in constructing portions of sides and housing and portions of side walls of the guide of stainless steel screen having a tight mesh.

Dyer, Gerald E. (inventor)

1989-01-01

160

Jet shielding of jet noise  

NASA Technical Reports Server (NTRS)

An experimental and theoretical study was conducted to develop a validated first principle analysis for predicting the jet noise reduction achieved by shielding one jet exhaust flow with a second, closely spaced, identical jet flow. A generalized fuel jet noise analytical model was formulated in which the acoustic radiation from a source jet propagates through the velocity and temperature discontinuity of the adjacent shielding jet. Input variables to the prediction procedure include jet Mach number, spacing, temperature, diameter, and source frequency. Refraction, diffraction, and reflection effects, which control the dual jet directivity pattern, are incorporated in the theory. The analysis calculates the difference in sound pressure level between the dual jet configuration and the radiation field based on superimposing two independent jet noise directivity patterns. Jet shielding was found experimentally to reduce noise levels in the common plane of the dual jet system relative to the noise generated by two independent jets.

Simonich, J. C.; Amiet, R. K.; Schlinker, R. H.

1986-01-01

161

Analysis of a Lunar Base Electrostatic Radiation Shield Concept  

NASA Technical Reports Server (NTRS)

Space weather can be defined as the total ensemble of radiation in space, as well as on the surface of moons and asteroids. It consists of electromagnetic, charged-particle, and neutral particle radiation. The fundamental goal behind this NIAC Phase I research is to investigate methods of generating a static electric-field potential phi(x, y, z) in the volume above and around a "safe" or protected area on the lunar surface so that trajectories of harmful charged particle radiation are modified (deflected or reflected), thus creating a shadow over that region. Since the charged particles are not neutralized but merely redirected, there will be areas outside of the shadowed protected region that will have a higher flux concentration of radiation. One of the fundamental limitations of the static electric (electrostatic)-field approach to radiation shielding is that complete shadowing is accomplished only by complete reflection, which can only occur for shield voltages greater than or equal to the kinetic energy (in electron volts) of the incoming charged particles. Just as habitats on Earth are protected from severe weather events and conditions, such as extreme temperatures, high winds, and UV radiation, using multiple methods of shielding protection from severe space weather will undoubtedly require multiple strategies. The electrostatic shield concept may be one of many methods employed to protect astronaut habitats on the lunar surface from some of the harmful effects of space weather.

Buhler, Charles R.

2004-01-01

162

Optimized shield materials trade study for lunar/gateway mission  

NASA Astrophysics Data System (ADS)

A critical enabling technology for Human Exploration and Development of Space (HEDS) is provision of adequate radiation protection to the astronauts. Radiation protection has traditionally been an evaluation of the design near the end of the design process and off-optimum solutions to protection problems have resulted with sometimes greatly added costs. It has been shown that material choices have a large impact on shield design. We have prepared software for optimization of shielding across a complex set of transportation and habitation elements for multisegmented missions allowing a rapid evaluation of material trade benefits. In this enabling technology, we have developed methods for optimized shield design over multi- segmented missions involving multiple work and living areas in the transport and duty phase of space missions. The total shield mass over all pieces of equipment and habitats is optimized subject to career dose and dose rate constraints. The career blood forming organ (BFO) constraints are more stringent and play a critical role in the optimization procedure. This software is applied to a Lunar mission scenario through a Gateway located at L1 of the Earth moon system. The short missions to L1 and the Moon mainly need to deal with the possibility of solar particle events. The details of this new method and its impact on space missions and other technologies will be discussed.

Tripathi, R.; Wilson, J.; Cucinotta, F.; Anderson, B.; Simonsen, L.

163

Dynamical and astronomical aspects of a project involving the placement of a solar shield at the first libration point  

Microsoft Academic Search

The astrodynamical and astronomical aspects of a project involving the placement of a space shield at the first inner collinear libration point of the sun-earth system to reduce insolation of the earth are analyzed. The position of the first libration point is calculated within the framework of the photogravitational restricted three-body problem. The analysis presented here also covers the characteristics

E. N. Polyakhova

1993-01-01

164

Shielding vacuum fluctuations with graphene  

NASA Astrophysics Data System (ADS)

The Casimir-Polder interaction of ground-state and excited atoms with graphene is investigated with the aim to establish whether graphene systems can be used as a shield for vacuum fluctuations of an underlying substrate. We calculate the zero-temperature Casimir-Polder potential from the reflection coefficients of graphene within the framework of the Dirac model. For both doped and undoped graphene we show limits at which graphene could be used effectively as a shield. Additional results are given for AB-stacked bilayer graphene.

Ribeiro, Sofia; Scheel, Stefan

2013-10-01

165

The Embedded Self-Shielding Method  

SciTech Connect

The embedded self-shielding method (ESSM) is described for computing resonance-shielded cross sections used in multigroup neutron transport calculations with the SCALE code system. The ESSM - embeds the self-shielding computation within the transport solution. The transport solution provides information for treating heterogeneous self-shielding effects, and the resulting shielded cross sections are fed back to the transport calculation. Iterations are done to obtain self-consistency. This allows self-shielded cross sections to be generated directly in the transport geometry without requiring external computation of Dancoff factors. The ESSM theory and example calculations are presented.

Williams, Mark L [ORNL; Kim, Kang Seog [ORNL

2012-01-01

166

Regolith Derived Heat Shield for Planetary Body Entry and Descent System with In Situ Fabrication  

NASA Technical Reports Server (NTRS)

This NIAC project investigated an innovative approach to provide heat shield protection to spacecraft after launch and prior to each EDL thus potentially realizing significant launch mass savings. Heat shields fabricated in situ can provide a thermal-protection system for spacecraft that routinely enter a planetary atmosphere. By fabricating the heat shield with space resources from materials available on moons and asteroids, it is possible to avoid launching the heat-shield mass from Earth. Regolith has extremely good insulating properties and the silicates it contains can be used in the fabrication and molding of thermal-protection materials. Such in situ developed heat shields have been suggested before by Lewis. Prior research efforts have shown that regolith properties can be compatible with very-high temperature resistance. Our project team is highly experienced in regolith processing and thermal protection systems (TPS). Routine access to space and return from any planetary surface requires dealing with heat loads experienced by the spacecraft during reentry. Our team addresses some of the key issues with the EDL of human-scale missions through a highly innovative investigation of heat shields that can be fabricated in space by using local resources on asteroids and moons. Most space missions are one-way trips, dedicated to placing an asset in space for economical or scientific gain. However, for human missions, a very-reliable heat-shield system is necessary to protect the crew from the intense heat experienced at very high entry velocities of approximately 11 km/s at approximately Mach 33 (Apollo). For a human mission to Mars, the return problem is even more difficult, with predicted velocities of up to 14 km/s, at approximately Mach 42 at the Earth-atmosphere entry. In addition to human return, it is very likely that future space-travel architecture will include returning cargo to the Earth, either for scientific purposes or for commercial reasons. Platinum, titanium, helium 3, and other metals, elements and minerals are all high-value commodities in limited supply on Earth, and it may be profitable to mine these substances throughout the Solar System and return them to Earth, if an economical method can be found. To date, several private corporations have been launched to pursue these goals. Because the heat shield is the last element to be used in an Earth-return mission, a high penalty is paid in the propellant mass required to carry the heat shield to the destination and back. If the heat shield could be manufactured in space, and then outfitted on the spacecraft prior to the reentry at Earth, then significant propellant and mass savings could be achieved during launch and space operations. Preliminary mission architecture scenarios are described, which explain the potential benefits that may be derived from using an in-situ fabricated regolith heat shield. In order to prove that this is a feasible technology concept, this project successfully fabricated heat shield materials from mineral simulant materials of lunar and Martian regolith by two methods: 1) Sintering and 2) Binding the simulant with a "room-temperature vulcanizing" (RTV) silicone formulated to withstand high temperatures. Initially a third type of fabrication was planned using the hot waste stream from regolith ISRU processes. This fabrication method was discarded since the resulting samples would be too dense and brittle for heat shields. High temperature flame tests at KSC and subsequent arc jet tests at Ames Research Center (ARC) have proved promising. These coupon tests show favorable materials properties and have the potential to be a new way of fabricating heat shields for space entry into planetary atmospheres.

Hogue, Michael D.; Meuller, Robert P.; Sibille, Laurent; Hintze, Paul E.; Rasky, Daniel J.

2012-01-01

167

Dynamical and astronomical aspects of a project involving the placement of a solar shield at the first libration point  

NASA Astrophysics Data System (ADS)

The astrodynamical and astronomical aspects of a project involving the placement of a space shield at the first inner collinear libration point of the sun-earth system to reduce insolation of the earth are analyzed. The position of the first libration point is calculated within the framework of the photogravitational restricted three-body problem. The analysis presented here also covers the characteristics of disk rotation near the center of mass, observation of a partial solar eclipse from different areas of the earth, determination of the type of eclipse for an area with specified coordinates, and evaluation of the effects of shield orientation, size, and shape.

Polyakhova, E. N.

1993-01-01

168

Solar wind induced magnetic field around the unmagnetized Earth  

Microsoft Academic Search

The Earth is a planet with a dipolar magnetic field which is agitated by a magnetized plasma wind streaming from the Sun. The magnetic field shields the Earth's surface from penetrating high energy solar wind particles, as well as interstellar cosmic rays. The magnetic dipole has reversed sign some hundreds of times over the last 400 million years. These polarity

G. T. Birk; H. Lesch; C. Konz

2004-01-01

169

Shielded radiation protection quantities beyond LEO  

NASA Astrophysics Data System (ADS)

The National Council on Radiation Protection and Measurements (NCRP) has recommended that the quantities used to evaluate health risk to astronauts due to radiation exposure be effective dose and gray-equivalent. The NCRP recommends that effective dose be the limiting quantity for prevention of stochastic effects. Effective dose is a measure of whole body exposure, a weighted average of dose equivalent to a number body tissues for which the NCRP has adopted tissue weighting factors recommended by the International Commission on Radiation Protection (ICRP). For deterministic effects, the NCRP has recommended that gray-equivalent be used. Gray-equivalent is evaluated for specific critical organs and is the weighted sum of absorbed dose from field components to that organ using the relative biological effectiveness (RBE) number for that field component. RBE numbers recommended by the NCRP are used. The NCRP has provided effective dose limits as well as limits for gray-equivalent to eyes, skin, and blood forming organs (BFO) for astronauts in low earth orbit (LEO). As yet, no such limits have been defined for astronaut operations beyond LEO. In this study, the radiation protection quantities, effective dose and gray-equivalent to the eyes, skin, and BFO, are calculated for several environments beyond LEO. The lunar surface and Martian environments are included. For each environment, these radiation protection quantities are calculated behind varying amounts of various types of shielding materials. The results are compared to the exposure limits for LEO, since limits have not yet been defined for interplanetary missions. The benefits of using shielding material containing hydrogen and choosing optimal mission times are discussed.

Clowdsley, M. S.; Wilson, J. W.; Kim, M. Y.; Anderson, B. M.; Nealy, J. E.

170

Earth's Seasons  

NSDL National Science Digital Library

A computer animation on the reason for the seasons. Voice-over describes the motion of Earth around the sun to show how the sun's light impacts the tilted Earth at different times of the year, causing seasonal changes.

Rochester Museum And Science Center, Strasenburgh P.

171

Topography of the shield volcano, Olympus Mons on Mars  

USGS Publications Warehouse

Olympus Mons, one of the largest known shield volcanoes in the Solar System, covers an area of >3.2 ?? 105 km2and has a diameter of >600 km, excluding its vast aureole deposits. The structure is five times larger than the largest shield volcano on the Earth. It is situated on the north-west flank of the Tharsis volcanic region, a broad topographic rise on the martian surface. The volcano has three physical subdivisions: the summit caldera, the terraced upper flanks, and the lower flanks, which terminate in a scarp 2-10 km high that nearly surrounds the structure. A large block of images of the Tharsis region, including Olympus Mons, was obtained by the Viking mission1. Here we present a topographic map of Olympus Mons, compiled using various combinations of stereo pairs of these images, together with stereoscopic perspective views generated by image processing techniques. ?? 1984 Nature Publishing Group.

Wu, S. S. C.; Garcia, P. A.; Jordan, R.; Schafer, F. J.; Skiff, B. A.

1984-01-01

172

Decontaminating lead bricks and shielding  

Microsoft Academic Search

Lead used for shielding is often surface contaminated with radioisotopes and is therefore a RCRA D008 mixed waste. The technology-based standard for treatment is macroencapsulation. However, decontaminating and recycling the clean lead is a more attractive solution. Los Alamos National Laboratory decontaminates material and equipment contaminated with radioisotopes. Decontaminating lead poses special problems because of the RCRA hazard classification and

Lussiez

1993-01-01

173

Decontaminating lead bricks and shielding  

Microsoft Academic Search

Lead used for shielding is often surface contaminated with radioisotopes and is therefore a RCRA D008 mixed waste. The technology-based standard for treatment is macroencapsulation. However, decontaminating and recycling the clean lead is a more attractive solution. Los Alamos National Laboratory decontaminates material and equipment contaminated with radioisotopes. Decontaminating lead poses special problems because of the RCRA hazard classification and

Lussiez

1994-01-01

174

Improved space radiation shielding methods  

NASA Technical Reports Server (NTRS)

The computing software that was used to perform the charged particle radiation transport analysis and shielding design for the Mariner Jupiter/Saturn 1977 spacecraft is described. Electron fluences, energy spectra and dose rates obtained with this software are presented and compared with independent computer calculations.

Davis, H. S.; Jordan, T. M.

1976-01-01

175

Heat shield reduces water loss.  

PubMed Central

A heat shield covered by polyvinyl chloride film greatly reduced insensible water loss and radiant energy requirements in 12 preterm infants on a radiant cradle. Measured transmittance of radiant energy emitted by the radiant heater was impeded minimally by various thin film plastics but was blocked significantly by Perspex. Images Figure

Fitch, C W; Korones, S B

1984-01-01

176

A Large Superconducting Magnetic Shield.  

National Technical Information Service (NTIS)

A large superconducting magnetic shield was designed and constructed to provide a low intensity field in a temperature controllable volume approximately 30 cm (12 in) long by 10.2 cm (4 in) in diameter. Design, construction and operating techniques are di...

R. H. Lundsten, J. F. Scarzello

1973-01-01

177

Hypervelocity impact on shielded plates  

Microsoft Academic Search

A ballistic limit equation for hypervelocity impact on thin plates is derived analytically. This equation applies to cases of impulsive impact on a plate that is protected by a multi-shock shield, and it is valid in the range of velocity above 6 km\\/s. Experimental tests were conducted at the NASA Johnson Space Center on square aluminum plates. Comparing the center

James P. Smith

1993-01-01

178

Material Effectiveness for Radiation Shielding  

NASA Technical Reports Server (NTRS)

Materials with a smaller mean atomic mass, such as lithium (Li) hydride and polyethylene, make the best radiation shields for astronauts. The materials have a higher density of nuclei and are better able to block incoming radiation. Also, they tend to produce fewer and less dangerous secondary particles after impact with incoming radiation.

2003-01-01

179

Earth Flow  

NSDL National Science Digital Library

This Flash animation with accompanying audio exhibits the different stages involved in the formation of an earth flow. A step-like scarp forms along with a flowage zone at the toe of the earth flow. The sequence concludes with the stabilization of the earth flow with vegetation. Expect long loading times.

Wiley

180

Edible Earth  

NSDL National Science Digital Library

In this activity, learners make a model of the solid Earth's layers that's good enough to eat! Learners use tasty foodstuffs to simulate Earth's inner core, outer core, mantle, and crust. The recipe includes ingredients for one edible Earth, but can be doubled or tripled to accommodate groups of learners. This activity requires adult supervision.

History, American M.

2011-08-20

181

Earth's Layers  

NSDL National Science Digital Library

Complete a poster all about Earth's Layers! Directions: Make a poster about Earth's Layers. (20 points) Include at least (1) large picture (15 points) on your poster complete with labels of every part (10 points). (15 points) Include at least three (3) facts about Earth's Layers. (5 points each) (15 points) Write at least a three sentence summary of your poster ...

Walls, Mrs.

2011-01-30

182

Snowball Earth  

NSDL National Science Digital Library

Audio program from the University of Wisconsin's Earthwatch Radio discusses the notion of the entire planet covered with ice. Doug Macdougall is an earth scientist at the University of California-San Diego and author of a new book called "Frozen Earth." He says the planet-wide freeze is known as "Snowball Earth."

183

Military Review: Desert Shield/Desert Storm.  

National Technical Information Service (NTIS)

CONTENTS: CASCOM Support for DESERT SHIELD/DESERT STORM; Total Army CSS: Providing the Means for Victory; Logistics Automation Support for Desert Storm; Building the DESERT Logistics force; Depot operations Supporting DESERT SHIELD; The Readiness Group's ...

1991-01-01

184

Rotary stripper for shielded and unshielded FCC  

NASA Technical Reports Server (NTRS)

Rotary stripper removes narrow strips of insulation and shielding to any desired depth. Unshielded cables are stripped on both sides with one stroke, shielded cables are stripped in steps of different depths.

Angele, W.; Chambers, C. M.

1971-01-01

185

Electromagnetic coupling through multiconductor cable shields  

SciTech Connect

This paper discusses two approaches to the determination of the distribution of source terms of a shielded multiconductor cable due to electromagnetic coupling through the shield. Comparisons are made of the results of some of these calculations with available data.

Tigner, T.E.; Frederick, D.; Setty, P.N.; Sutton, R.W.

1982-12-01

186

Shielding and grounding in large detectors  

SciTech Connect

Prevention of electromagnetic interference (EMI), or ``noise pickup,`` is an important design aspect in large detectors in accelerator environments. Shielding effectiveness as a function of shield thickness and conductivity vs the type and frequency of the interference field is described. Noise induced in transmission lines by ground loop driven currents in the shield is evaluated and the importance of low shield resistance is emphasized. Some measures for prevention of ground loops and isolation of detector-readout systems are discussed.

Radeka, V.

1998-09-01

187

Recommendations for a Static Cosmic Ray Shield for Enriched Germanium Detectors  

SciTech Connect

This document provides a detailed study of cost and materials that could be used to shield the detector material of the international Tonne-scale germanium neutrinoless double-beta decay experiment from hadronic particles from cosmic ray showers at the Earth's surface. This work was motivated by the need for a shield that minimizes activation of the enriched germanium during storage; in particular, when the detector material is being worked on at the detector manufacturer's facility. This work considers two options for shielding the detector material from cosmic ray particles. One option is to use a pre-existing structure already located near the detector manufacturer, such as Canberra Industries in Meriden, Connecticut. The other option is to build a shield onsite at a detector manufacturer's site. This paper presents a cost and efficiency analysis of such construction.

Aguayo Navarrete, Estanislao; Orrell, John L.; Ankney, Austin S.; Berguson, Timothy J.

2011-09-21

188

Vehicle Shield Optimization and Risk Assessment of Future NEO Missions  

NASA Technical Reports Server (NTRS)

Future human space missions target far destinations such as Near Earth Objects (NEO) or Mars that require extended stay in hostile radiation environments in deep space. The continuous assessment of exploration vehicles is needed to iteratively optimize the designs for shielding protection and calculating the risks associated with such long missions. We use a predictive software capability that calculates the risks to humans inside a spacecraft. The software uses the CAD software Pro/Engineer and Fishbowl tool kit to quantify the radiation shielding properties of the spacecraft geometry by calculating the areal density seen at a certain point, dose point, inside the spacecraft. The shielding results are used by NASA-developed software, BRYNTRN, to quantify the organ doses received in a human body located in the vehicle in a possible solar particle events (SPE) during such prolonged space missions. The organ doses are used to quantify the risks posed on the astronauts' health and life using NASA Space Cancer Model software. An illustration of the shielding optimization and risk calculation on an exploration vehicle design suitable for a NEO mission is provided in this study. The vehicle capsule is made of aluminum shell, airlock with hydrogen-rich carbon composite material end caps. The capsule contains sets of racks that surround a working and living area. A water shelter is provided in the middle of the vehicle to enhance the shielding in case of SPE. The mass distribution is optimized to minimize radiation hotspots and an assessment of the risks associated with a NEO mission is calculated.

Nounu, Hatem, N.; Kim, Myung-Hee; Cucinotta, Francis A.

2011-01-01

189

Orbiting Earth  

NSDL National Science Digital Library

This Flash animation contrasts the geostationary versus polar orbits for satellites. For a geostationary orbit, the satellite remains directly above a fixed point at all times; in time with the Earth's rotation, the satellite circles the earth once every 24 hours, continually viewing the same part of Earth. For the polar orbit, the satellite circles over both poles in a constant plane while earth rotates beneath. Earth's rotation exposes different parts of the surface on each orbit. The animation is useful for a discussion on how remote sensing imagery and Global Positioning Systems (GPS) signals are derived. The animation can be paused and rewound to stress important points.

Loomis, Jennifer; Nasa; Earth, Exploring

190

Some observations about shielding extremely low-frequency magnetic fields by finite width shields  

Microsoft Academic Search

Shielding of extremely low-frequency magnetic fields is limited by fields penetrating through imperfect material and leakage around the edges of shields which do not completely enclose the shielded region. The latter effect, more specifically the effect of source geometry and shield type on leakage, is the subject of this work. Particular attention is paid to elementary cylindrical dipole sources since

Robert G. Olsen; Pablo Moreno

1996-01-01

191

Lightning Shielding of Plastic Telephone Cable  

Microsoft Academic Search

Data are presented on the surge characteristics of various types and combinations of metals when applied as a shield for buried telephone cables. Surge currents were applied to the shield of 500-foot lengths of cable and the potentials developed between the shield and conductors were measured at selected points along the cable length in order to determine relative susceptibility to

E. Fisher; W. Bishop

1970-01-01

192

13C Chemical Shieldings in Solids  

Microsoft Academic Search

Analogous to the importance of 13C isotropic shieldings for chemical analysis of liquids with nuclear magnetic resonance spectroscopy, 13C chemical shielding anisotropies are proving to be valuable in the characterization of solids. Specifically, molecular geometry is revealed by the full shielding anisotropy and molecular motion may be characterized by changes in the powder pattern. In particular, the principal components of

T. M. Duncan

1987-01-01

193

Shielding techniques tackle EMI excesses. V - EMI shielding  

NASA Astrophysics Data System (ADS)

The utilization of shielding gaskets in EMI design is presented in terms of seam design, gasket design, groove design, and fastener spacing. The main function of seam design is to minimize the coupling efficiency of a seam, and for effective shielding, seam design should include mating surfaces which are as flat as possible, and a flange width at least five times the maximum anticipated separation between mating surfaces. Seam surface contact with a gasket should be firm, continuous, and uniform. Gasket height, closure pressure, and compression set as a function of the applied pressure parameters are determined using compression/deflection curves. Environmental seal requirements are given and the most common materials used are neoprene, silicone, butadiene-acrylonitrile, and natural rubber. Groove design is also discussed, considering gasket heights and cross-sectional areas. Finally, fastener spacing is considered, by examining deflection as a percentage of gasket height.

Grant, P.

1982-10-01

194

PLUG STORAGE BUILDING, TRA611, AWAITS SHIELDING SOIL TO BE PLACED ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

PLUG STORAGE BUILDING, TRA-611, AWAITS SHIELDING SOIL TO BE PLACED OVER PLUG STORAGE TUBES. WING WALLS WILL SUPPORT EARTH FILL. MTR, PROCESS WATER BUILDING, AND WORKING RESERVOIR IN VIEW BEYOND PLUG STORAGE. CAMERA FACES NORTHEAST. INL NEGATIVE NO. 2949. Unknown Photographer, 7/30/1951 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

195

Effects of bumper size on high velocity impact damage to Whipple shield  

Microsoft Academic Search

With the increasing number of space mission the impact risk on spacecraft at hypervelocity by space debris is increasing A collision with space debris can cause damage to a spacecraft in low Earth orbit For designing spacecraft protection constructions and developing advanced debris shieldsLhypervelocity impact simulation experiments on the ground and the computer simulation of hypervelocity impact is the important

Y. Ha; G. S. Guan; B. J. Pang; W. Zhang

2006-01-01

196

Modulation of the DNA-damage response to HZE particles by shielding  

Microsoft Academic Search

Ions of high atomic number and energy (HZE particles) pose a significant cancer risk to astronauts on prolonged space missions. On Earth, similar ions are being used for targeted cancer therapy. The properties of these particles can be drastically altered during passage through spacecraft shielding, therapy beam modulators, or the human body. Here, we have used pertinent responses to DNA

Bipasha Mukherjee; Cristel Vanessa Camacho; Nozomi Tomimatsu; Jack Miller; Sandeep Burma

2008-01-01

197

Regolith Biological Shield for a Lunar Outpost from High Energy Solar Protons  

Microsoft Academic Search

Beyond Earth atmosphere, natural space radiation from Galactic Cosmic Rays and Solar Energetic Protons (SEPs) represents a significant hazard to both manned and robotic missions. For lunar settlements, protecting astronauts from SEPs is a key safety issue that needs to be addressed by identifying appropriate shielding materials. This paper investigates the interaction of SEPs with the lunar regolith, and quantifies

Tai T. Pham; Mohamed S. El-Genk

2008-01-01

198

Effect of Shielding Materials from SPEs on the Lunar and Mars Surface  

Microsoft Academic Search

Solar particle events (SPEs) are a health concern for astronauts who are involved in space missions outside the Earth's geomagnetic field. Here we examine the physical compositions and intensities of SPE exposures in sensitive astronaut tissues behind various shielding materials using the lunar and Mars surface environment during some historically large SPEs including the recent events of October 2003 and

Myung-Hee Y. Kim; Francis A. Cucinotta

2005-01-01

199

Discover Earth  

NASA Technical Reports Server (NTRS)

Discover Earth is a NASA-sponsored project for teachers of grades 5-12, designed to: (1) enhance understanding of the Earth as an integrated system; (2) enhance the interdisciplinary approach to science instruction; and (3) provide classroom materials that focus on those goals. Discover Earth is conducted by the Institute for Global Environmental Strategies in collaboration with Dr. Eric Barron, Director, Earth System Science Center, The Pennsylvania State University; and Dr. Robert Hudson, Chair, the Department of Meteorology, University of Maryland at College Park. The enclosed materials: (1) represent only part of the Discover Earth materials; (2) were developed by classroom teachers who are participating in the Discover Earth project; (3) utilize an investigative approach and on-line data; and (4) can be effectively adjusted to classrooms with greater/without technology access. The Discover Earth classroom materials focus on the Earth system and key issues of global climate change including topics such as the greenhouse effect, clouds and Earth's radiation balance, surface hydrology and land cover, and volcanoes and climate change. All the materials developed to date are available on line at (http://www.strategies.org) You are encouraged to submit comments and recommendations about these materials to the Discover Earth project manager, contact information is listed below. You are welcome to duplicate all these materials.

Steele, Colleen

1998-01-01

200

Thermally isolated deployable shield for spacecraft  

NASA Technical Reports Server (NTRS)

A thermally isolated deployable shield for spacecraft is provided utilizing a plurality of lattice panels stowable generally against the craft and deployable to some fixed distance from the craft. The lattice panels are formed from replaceable shield panels affixed to lattice structures. The lattice panels generally encircle the craft providing 360 degree coverage therearound. Actuation means are provided from translating the shield radially outward from the craft and thermally isolating the shield from the craft. The lattice panels are relatively flexible, allowing the shield to deploy to variable diameters while retaining uniform curvature thereof. Restraining means are provided for holding the shield relatively tight in its stowed configuration. Close-out assemblies provide light sealing and protection of the annular spaces between the deployed shield and the crafts end structure.

Redmon, John W., Jr. (inventor); Miller, Andre E. (inventor); Lawson, Bobby E. (inventor); Cobb, William E. (inventor)

1991-01-01

201

Design of magnets inside cylindrical superconducting shields  

NASA Technical Reports Server (NTRS)

The design of magnets inside closed, cylindrical, superconducting shields is discussed. The Green function is given for the magnetic vector potential for cylindrically symmetric currents inside such a shield. The magnetic field everywhere inside the shield can be obtained from this function, which includes the effects of the induced shield currents exactly. The field is given for a thin solenoid as an example and the convergence of the series solution for this case is discussed. The shield can significantly reduce the strength and improve the homogeneity of a magnet. The improvement in homogeneity is of particular importance in the design of correction coils. These effects, and the maximum field on the shield, are examined for a typical solenoid. The results given are also useful, although not exact, for long shields with one or two open ends.

Rigby, K. W.

1988-01-01

202

Mats and fabrics for electromagnetic interference shielding  

NASA Astrophysics Data System (ADS)

Fabrics (with continuous electrically conductive fibers) are more effective than mats (with discontinuous conductive fibers) for electromagnetic interference shielding. Conductive fibers in the form of metal-coated polymer fibers or metal-coated carbon fibers are more effective than those in the form of bare carbon fibers. The highest shielding effectiveness of 53 dB at 1.0 GHz was attained by a metal-coated polymer fabric. The shielding is due mainly to reflection. A higher shielding effectiveness correlates with a higher reflectivity and a lower electrical resistivity. Both shielding effectiveness and reflectivity decrease with increasing frequency from 300 kHz to 1.5 GHz. The shielding effectiveness increases with thickness, as shown for bare carbon fiber mats. A nickel-coated carbon fiber mat of areal weight 9 g/m2 is similar to a bare carbon fiber mat of areal weight 17 g/m2 in shielding effectiveness.

Kim, Taejin; Chung, D. D. L.

2006-06-01

203

S8DR shield examination  

NASA Technical Reports Server (NTRS)

The SNAP 8 developmental reactor lithium hydride shield was examined after being irradiated for over 7000 hours at relatively low temperature. A crack was located in the seam weld of the containment vessel, probably the result of hot short cracking under thermal stress. The LiH was visually examined at two locations and its appearance was typical of low temperature irradiated LiH. The adherence of the chrome oxide emittance coating was found to be excellent.

Mason, D. G.; Mccurnin, W. R.

1973-01-01

204

Shielding calculations for Inshas cyclotron  

NASA Astrophysics Data System (ADS)

Methods used in shielding calculations for the cyclotron vault and experimental rooms of Egypt's first cyclotron laboratory to be erected at the premises of the Nuclear Research Center, Atomic Energy Authority (Inshas) are discussed. Use is made of the removal diffusion theory and of the techniques presented in NCRP-51, Wall and ceiling dimensions are estimated based on radiation protection norms given in the ICRP-60 as issued in 1991.

Comsan, M. N. H.

1996-05-01

205

Steam generator hand hole shielding.  

PubMed

Seabrook Station is an 1198 MWE Pressurized Water Reactor (PWR) that began commercial operation in 1990. Expensive and dose intensive Steam Generator Replacement Projects among PWR operators have led to an increase in steam generator preventative maintenance. Most of this preventative maintenance is performed through access ports in the shell of the steam generator just above the tube sheet known as secondary side hand holes. Secondary side work activities performed through the hand holes are typically performed without the shielding benefit of water in the secondary side of the steam generator. An increase in cleaning and inspection work scope has led to an increase in dose attributed to steam generator secondary side maintenance. This increased work scope and the station goal of maintaining personnel radiation dose ALARA led to the development of the shielding concept described in this article. This shield design saved an estimated 2.5 person-rem (25 person-Smv) the first time it was deployed and is expected to save an additional 50 person-rem (500 person-mSv) over the remaining life of the plant. PMID:10770158

Cox, W E

2000-05-01

206

Photonic Bandgap (PBG) Shielding Technology  

NASA Technical Reports Server (NTRS)

Photonic Bandgap (PBG) shielding technology is a new approach to designing electromagnetic shielding materials for mitigating Electromagnetic Interference (EM!) with small, light-weight shielding materials. It focuses on ground planes of printed wiring boards (PWBs), rather than on components. Modem PSG materials also are emerging based on planar materials, in place of earlier, bulkier, 3-dimensional PBG structures. Planar PBG designs especially show great promise in mitigating and suppressing EMI and crosstalk for aerospace designs, such as needed for NASA's Constellation Program, for returning humans to the moon and for use by our first human visitors traveling to and from Mars. Photonic Bandgap (PBG) materials are also known as artificial dielectrics, meta-materials, and photonic crystals. General PBG materials are fundamentally periodic slow-wave structures in I, 2, or 3 dimensions. By adjusting the choice of structure periodicities in terms of size and recurring structure spacings, multiple scatterings of surface waves can be created that act as a forbidden energy gap (i.e., a range of frequencies) over which nominally-conductive metallic conductors cease to be a conductor and become dielectrics. Equivalently, PBG materials can be regarded as giving rise to forbidden energy gaps in metals without chemical doping, analogous to electron bandgap properties that previously gave rise to the modem semiconductor industry 60 years ago. Electromagnetic waves cannot propagate over bandgap regions that are created with PBG materials, that is, over frequencies for which a bandgap is artificially created through introducing periodic defects

Bastin, Gary L.

2007-01-01

207

Dynamic Earth  

NSDL National Science Digital Library

Dynamic Earth consists of four sections and an assessment. Each section explores one aspect of the earth's structure and the movement of its tectonic plates. Simply follow the instructions on the screen to learn about the layers that make up the earth; how the continents arrived at their current locations; the constant movement of the tectonic plates; and the volcanoes, earthquakes, and other events that result from the movements of the plates. Students will view animations, read explanations, and use their mouse to drag and drop the earth's continents in their correct places, highlight features on a map, and cause earth's tectonic plates to move. At various points, students will check their knowledge by taking a quick quiz or playing a game to see how much they have learned about the Dynamic Earth. Students should read section introductions carefully, as they give a basic overview of concepts, and use the Glossary to look up definitions to unfamiliar terms.

Quinn, Ashlinn

2007-01-01

208

Earth Floor  

NSDL National Science Digital Library

This Classroom of the Future (COTF) website highlights information about the Earth and its development through time. Spheres discusses layers of the Earth's environment such as the hydrosphere, Cycles discusses rock and water cycles, and Diversity illustrates different species and genetic variations that have emerged on Earth. Also covered are biomes, adaptation, geologic time, and plate tectonics. Each of these sections is an in-depth tutorial on these specific topics.

209

Visible Earth  

NSDL National Science Digital Library

NASA's Visible Earth is a searchable directory of images, visualizations, and animations of the Earth. The images are also listed under the following categories: agriculture, atmosphere, biosphere, cryosphere, human dimensions, hydrosphere, land surface, oceans, radiance or imagery, solid earth, locations, and satellites. Accompanying each image are credits, data about the image, the satellite it was taken from, a description of what is shown, and a high-resolution viewable image.

210

Dynamic Earth  

NSDL National Science Digital Library

Dynamic Earth is an interactive Web site where students can learn about the structure of the Earth, the movements of tectonic plates, and the forces that create mountains, valleys, volcanoes, and earthquakes. It consists of four sections, a glossary and an assessment. Each section explores one aspect of the Earth's structure and the movement of its tectonic plates. At various points of the interactive, students can check their knowledge by taking a quick quiz or playing a game to see how much they have learned. Dynamic Earth includes an extensive assessment section designed to evaluate how well students have learned the content and skills.

211

Heat-shield design for glovebox applications.  

SciTech Connect

Heat shields can often be used in place of insulation materials as an effective means of insulating glovebox furnace vessels. If used properly, shields can accomplish two important objectives: thermal insulation of the vessel to maintain a desired process temperature and protection of the glovebox, equipment, and user. A heat-shield assembly can be described as an arrangement of thin, properly-spaced, metal sheets that reduce radiation heat transfer. The main problem encountered in the design of a heat shield assembly is choosing the number of shields. In determining the heat transfer characteristics of a heat-shield assembly, a number of factors must be taken into consideration. The glovebox or outside environment, material properties, geometry, and operating temperature all have varying effects on the expected results. A simple method, for planar-horizontal and cylindrical-vertical shields, allowing the approximation of the outermost shield temperature, the practical number of shields, and the net heat-transfer rate will be presented. Methods used in the fabrication of heat-shield assemblies will also be discussed.

Frigo, A. A.

1998-07-10

212

The Feasibility of Multipole Electrostatic Radiation Shielding  

NASA Technical Reports Server (NTRS)

Although passive shielding appears to be the only workable solution for galactic cosmic radiation (GCR), active shielding may play an important augmenting role to control the dose from solar particle events (SPEs). It has been noted that, to meet the guidelines of NCRP Report No. 98 through the six SPEs of 1989, a crew member would need roughly double the passive shielding that is necessary to control the GCR dose . This would dramatically increase spacecraft mass, and so it has been proposed that a small but more heavily shielded storm shelter may be used to protect the crew during SPEs. Since a gradual SPE may last 5 or more days, staying in a storm shelter may be psychologically and physiologically distressing to the crew. Storm shelters do not provide shielding for the spacecraft itself against the SPE radiation, and radiation damage to critical electronics may result in loss of mission and life. Single-event effects during the radiation storm may require quick crew response to maintain the integrity of the spacecraft, and confining the crew to a storm shelter prohibits their attending to the spacecraft at the precise time when that attention is needed the most. Active shielding cannot protect against GCR because the particle energies are too high. Although lower energy particles are easier to stop in a passive shield, such shielding is more satisfactory against GCR than against SPE radiation because of the tremendous difference in their initial fluences. Even a small fraction of the SPE fluence penetrating the passive shielding may result in an unacceptably high dose. Active shielding is more effective than passive shielding against SPE radiation because it offers 100% shielding effectiveness up to the cutoff energy, and significant shielding effectiveness beyond the cutoff as well.

Metzger, Philip T.; Lane, John E.; Youngquist, Robert C.

2004-01-01

213

Exploratory Environmental Tests of Several Heat Shields  

NASA Technical Reports Server (NTRS)

Exploratory tests have been conducted with several conceptual radiative heat shields of composite construction. Measured transient temperature distributions were obtained for a graphite heat shield without insulation and with three types of insulating materials, and for a metal multipost heat shield, at surface temperatures of approximately 2,000 F and 1,450 F, respectively, by use of a radiant-heat facility. The graphite configurations suffered loss of surface material under repeated irradiation. Temperature distribution calculated for the metal heat shield by a numerical procedure was in good agreement with measured data. Environmental survival tests of the graphite heat shield without insulation, an insulated multipost heat shield, and a stainless-steel-tile heat shield were made at temperatures of 2,000 F and dynamic pressures of approximately 6,000 lb/sq ft, provided by an ethylene-heated jet operating at a Mach number of 2.0 and sea-level conditions. The graphite heat shield survived the simulated aerodynamic heating and pressure loading. A problem area exists in the design and materials for heat-resistant fasteners between the graphite shield and the base structure. The insulated multipost heat shield was found to be superior to the stainless-steel-tile heat shield in retarding heat flow. Over-lapped face-plate joints and surface smoothness of the insulated multi- post heat shield were not adversely affected by the test environment. The graphite heat shield without insulation survived tests made in the acoustic environment of a large air jet. This acoustic environment is random in frequency and has an overall noise level of 160 decibels.

Goodman, George P.; Betts, John, Jr.

1961-01-01

214

Earth Impact  

NSDL National Science Digital Library

This activity poses the question: What would happen if a meteor or comet impacted Earth? Students simulate an impact in a container of sand using various-sized rocks, all while measuring, recording and graphing results and conclusions. Then students brainstorm ways to prevent an object from hitting the Earth.

Integrated Teaching And Learning Program

215

Earth tides  

SciTech Connect

Nineteen papers on gravity, tilt, and strain tides are compiled into this volume. Detailed chapters cover the calculation of the tidal forces and of the Earth's response to them, as well as actual observations of earth tides. Partial Contents: On Earth tides. The tidal forces: Tidal Forces. New Computations of the Tide-Generating Potential. Corrected Tables of Tidal Harmonics. The Theory of Tidal Deformations. Body Tides on an Elliptical, Rotating, Elastic and Oceanless Earth, Deformation of the Earth by Surface Loads. Gravimetric Tidal Loading Computed from Integrated Green's Functions. Tidal Friction in the Solid Earth. Loading Tides Versus Body Tides. Lunar Tidal Acceleration from Earth Satellite Orbit Analysis. Observations: gravity. Tidal Gravity in Britain: Tidal Loading and the Spatial Distribution of the Marine Tide. Tidal Loading along a Profile Europe-East Africa-South Asia-Australia and the Pacific Ocean. Detailed Gravity-Tide Spectrum between One and Four Cycles per Day. Observations: tilt and strain. Cavity and Topographic Effects in Tilt and Strain Measurement. Observations of Local Elastic Effects on Earth Tide Tilts and Strains.

Harrison, J.C.

1984-01-01

216

Earth meandering  

Microsoft Academic Search

In this paper we try to put away current Global Tectonic Model to look the tectonic evolution of the earth from new point of view. Our new dynamic model is based on study of river meandering (RM) which infer new concept as Earth meandering(EM). In a universal gravitational field if we consider a clockwise spiral galaxy model rotate above Ninety

H. Asadiyan; A. Zamani

2009-01-01

217

Earth tides  

Microsoft Academic Search

The main geometrical characteristics and mechanical properties of bodily tides are described, using the convenient elastic parameters of Love. The problem of the Earth's deformation is a problem of spherical elasticity of the sixth order. The importance of Earth tides in astronomy and geophysics is emphasized by their relation to the precession-nutation and tesseral tidal problems, the secular retardation of

Paul Melchior

1974-01-01

218

Investigation of Lightning Rod Shielding Angle  

NASA Astrophysics Data System (ADS)

This paper studies those parameters affecting the shielding angle of the lightning rod (Franklin Rod) above very tall buildings. It was recommended that the shielding angle of the lightning rod is about 45°?60°. The downward lightning leader is modeled by using discrete line charges to consider the exponential distribution of charges through the downward leader. The voltage condition used by Rizk is used to investigate the inception of the upward lightning leader. Different air conditions (relative air density and air humidity) are considered for more practical simulation. The influences of lightning parameters and lightning rod height on the shielding angle are studied. The results shows that, lightning leader parameters, lightning rod height and ground slope have series effects on the lightning rod shielding angle. Based on the results, a lightning rod shielding angle for shielding design is recommended to decrease the lightning stroke to the lightning rod.

Nayel, Mohamed

219

Optimation of cooled shields in insulations  

NASA Technical Reports Server (NTRS)

A method to optimize the location, temperature, and heat dissipation rate of each cooled shield inside an insulation layer was developed. The method is based on the minimization of the entropy production rate which is proportional to the heat leak across the insulation. It is shown that the maximum number of shields to be used in most practical applications is three. However, cooled shields are useful only at low values of the overall, cold wall to hot wall absolute temperature ratio. The performance of the insulation system is relatively insensitive to deviations from the optimum values of the temperature and location of the cooling shields. Design curves for rapid estimates of the locations and temperatures of cooling shields in various types of insulations, and an equation for calculating the cooling loads for the shields are presented.

Chato, J. C.; Khodadadi, J. M.; Seyed-Yagoobi, J.

1984-01-01

220

Miniature, shielded electrical connector with strain relief  

NASA Technical Reports Server (NTRS)

An electrical connector assembly includes a wire bundle having at least one wire with a metal shield surrounding at least a portion of the wire. The shield has an end portion and provides electromagnetic interference protection to the wire. A backshell includes a body and a cover secured to the body together defining an internal cavity with the wire at least partially arranged within the cavity. The backshell provides EMI protection for the portion of the wire bundle not covered by the shield. The backshell includes a hole in a wall of either the body or the cover with the end portion of the shield extending through the hole. The clamp is secured about the body and the cover with the end portion of the shield arranged between the clamp and the backshell grounding the shield to the backshell. The clamp forces the backshell into engagement with the wire bundle to provide strain relief for the wire bundle.

Diep, Chuong H. (Inventor)

2006-01-01

221

Morphometric comparison of Icelandic lava shield volcanoes versus selected Venusian edifices  

NASA Technical Reports Server (NTRS)

Shield volcanoes are common landforms on the silicate planets of the inner Solar System, and a wide variety have recently been documented on Venus by means of Magellan observations. In this report, we emphasize our recently completed morphometric analysis of three representative Icelandic lava shields: the classic Skjaldbreidur edifice, the low-reflief Lambahraun feature, and the monogenetic Sandfellshaed shield, as the basis for comparison with representative venusian edifices (greater than 60 km in diameter). Our detailed morphometric measurements of a representative and well-studied set of Icelandic volcanoes permits us to make comparisons with our measurements of a reasonable subset of shield-like edifices on Venus on the basis of Magellan global radar altimetry. Our study has been restricted to venusian features larger than approximately 60 km in basal diameter, on the basis of the minimum intrinsic spatial resolution (8 km) of the Magellan radar altimetry data. Finally, in order to examine the implications of landform scaling from terrestrial simple and composite shields to larger venusian varieties, we have considered the morphometry of the subaerial component of Mauna Loa, a type-locality for a composite shield edifice on Earth.

Garvin, James B.; Williams, Richard S., Jr.

1993-01-01

222

Development and Evaluation of the Next Generation of Meteoroid and Orbital Debris Shields  

NASA Astrophysics Data System (ADS)

Recent events such as the Chinese anti-satellite missile test in January 2007 and the collision between a Russian Cosmos satellite and US Iridium satellite in February 2009 are responsible for a rapid increase in the population of orbital debris in Low Earth Orbit (LEO). Without active debris removal strategies the debris population in key orbits will continue to increase, requiring enhanced shielding capabilities to maintain allowable penetration risks. One of the more promising developments in recent years for meteoroid and orbital debris shielding (MMOD) is the application of open cell foams. Although shielding onboard the International Space Station is the most capable ever flown, the most proficient configuration (stuffed Whipple shield) requires an additional ˜30% of the shielding mass for non-ballistic requirements (e.g. stiffeners, fasteners, etc.). Open cell foam structures provide similar mechanical performance to more traditional structural components such as honeycomb sandwich panels, as well as improved projectile fragmentation and melting as a result of repeated shocking by foam ligaments. In this paper, the preliminary results of an extensive hypervelocity impact test program on next generation MMOD shielding configurations incorporating open-cell metallic foams are reported.

Ryan, Shannon; Christiansen, Eric

2009-06-01

223

Regolith Biological Shield for a Lunar Outpost from High Energy Solar Protons  

NASA Astrophysics Data System (ADS)

Beyond Earth atmosphere, natural space radiation from Galactic Cosmic Rays and Solar Energetic Protons (SEPs) represents a significant hazard to both manned and robotic missions. For lunar settlements, protecting astronauts from SEPs is a key safety issue that needs to be addressed by identifying appropriate shielding materials. This paper investigates the interaction of SEPs with the lunar regolith, and quantifies the effectiveness of the regolith as a biological shield for a human habitat, compared to aluminum, presently the standard shielding material. Also calculated is the shielding thickness to reduce the dose in the habitat to those recommended by International Radiation Protection Committee and by NASA for operation on the international space station. The present calculations are for the most energetic solar event of February 1956, which included high energy protons up to 1000 MeV. Results show that the lunar regolith is as effective as aluminum for shielding lunar outposts. A large thickness of the regolith (~30 g/cm2) would be needed to reduce the dose in the habitat from high energy protons below the 30 days flight crew limit of 25 Rem (or 250 mSv) and significantly more shielding would be needed (~150 g/cm2) to reduce the dose down to the limit for radiation workers of 5 Rem (or 50 mSv).

Pham, Tai T.; El-Genk, Mohamed S.

2008-01-01

224

Dynamic rotating-shield brachytherapy  

SciTech Connect

Purpose: To present dynamic rotating shield brachytherapy (D-RSBT), a novel form of high-dose-rate brachytherapy (HDR-BT) with electronic brachytherapy source, where the radiation shield is capable of changing emission angles during the radiation delivery process.Methods: A D-RSBT system uses two layers of independently rotating tungsten alloy shields, each with a 180° azimuthal emission angle. The D-RSBT planning is separated into two stages: anchor plan optimization and optimal sequencing. In the anchor plan optimization, anchor plans are generated by maximizing the D{sub 90} for the high-risk clinical-tumor-volume (HR-CTV) assuming a fixed azimuthal emission angle of 11.25°. In the optimal sequencing, treatment plans that most closely approximate the anchor plans under the delivery-time constraint will be efficiently computed. Treatment plans for five cervical cancer patients were generated for D-RSBT, single-shield RSBT (S-RSBT), and {sup 192}Ir-based intracavitary brachytherapy with supplementary interstitial brachytherapy (IS + ICBT) assuming five treatment fractions. External beam radiotherapy doses of 45 Gy in 25 fractions of 1.8 Gy each were accounted for. The high-risk clinical target volume (HR-CTV) doses were escalated such that the D{sub 2cc} of the rectum, sigmoid colon, or bladder reached its tolerance equivalent dose in 2 Gy fractions (EQD2 with ?/?= 3 Gy) of 75 Gy, 75 Gy, or 90 Gy, respectively.Results: For the patients considered, IS + ICBT had an average total dwell time of 5.7 minutes/fraction (min/fx) assuming a 10 Ci{sup 192}Ir source, and the average HR-CTV D{sub 90} was 78.9 Gy. In order to match the HR-CTV D{sub 90} of IS + ICBT, D-RSBT required an average of 10.1 min/fx more delivery time, and S-RSBT required 6.7 min/fx more. If an additional 20 min/fx of delivery time is allowed beyond that of the IS + ICBT case, D-RSBT and S-RSBT increased the HR-CTV D{sub 90} above IS + ICBT by an average of 16.3 Gy and 9.1 Gy, respectively.Conclusions: For cervical cancer patients, D-RSBT can boost HR-CTV D{sub 90} over IS + ICBT and S-RSBT without violating the tolerance doses to the bladder, rectum, or sigmoid. The D{sub 90} improvements from D-RSBT depend on the patient, the delivery time budget, and the applicator structure.

Liu, Yunlong [Department of Electrical and Computer Engineering, University of Iowa, 4016 Seamans Center, Iowa City, Iowa 52242 (United States)] [Department of Electrical and Computer Engineering, University of Iowa, 4016 Seamans Center, Iowa City, Iowa 52242 (United States); Flynn, Ryan T.; Kim, Yusung [Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242 (United States)] [Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242 (United States); Yang, Wenjun [Department of Medical Physics, University of Wisconsin-Madison, 1111 Highland Avenue, Madison, Wisconsin 53705 (United States)] [Department of Medical Physics, University of Wisconsin-Madison, 1111 Highland Avenue, Madison, Wisconsin 53705 (United States); Wu, Xiaodong [Department of Electrical and Computer Engineering, University of Iowa, 4016 Seamans Center, Iowa City, Iowa 52242 and Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242 (United States)] [Department of Electrical and Computer Engineering, University of Iowa, 4016 Seamans Center, Iowa City, Iowa 52242 and Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242 (United States)

2013-12-15

225

Preliminary design of a meteoroid/orbital debris shield system for a Mars mission spacecraft  

NASA Technical Reports Server (NTRS)

A preliminary design of a spacecraft shield system to defeat meteoroids and orbital debris during a Mars mission is presented. The mission scenario is first defined in terms of stage times which include LEO, transit, low-Mars orbit, and Mars surface periods. The environment definitions for earth-orbital space debris, planetary meteoroids, and interplanetary meteoroids are next introduced. Shield system design approaches incorporate stochastic simulation, hydrocode analyses, hypervelocity impact testing, and optimization techniques. Structural design trades presented include spacecraft configuration, mission schedule, penetration risk, and total standoff distance between the bumper and wall.

Robinson, J. H.; Mog, R. A.

1992-01-01

226

Tests of shielding effectiveness of Kevlar and Nextel onboard the International Space Station and the Foton-M3 capsule.  

PubMed

Radiation assessment and protection in space is the first step in planning future missions to the Moon and Mars, where mission and number of space travelers will increase and the protection of the geomagnetic shielding against the cosmic radiation will be absent. In this framework, the shielding effectiveness of two flexible materials, Kevlar and Nextel, were tested, which are largely used in the construction of spacecrafts. Accelerator-based tests clearly demonstrated that Kevlar is an excellent shield for heavy ions, close to polyethylene, whereas Nextel shows poor shielding characteristics. Measurements on flight performed onboard of the International Space Station and of the Foton-M3 capsule have been carried out with special attention to the neutron component; shielded and unshielded detectors (thermoluminescence dosemeters, bubble detectors) were exposed to a real radiation environment to test the shielding properties of the materials under study. The results indicate no significant effects of shielding, suggesting that thin shields in low-Earth Orbit have little effect on absorbed dose. PMID:20364264

Pugliese, M; Bengin, V; Casolino, M; Roca, V; Zanini, A; Durante, M

2010-08-01

227

Simplified model for solar cosmic ray exposure in manned Earth orbital flights  

NASA Technical Reports Server (NTRS)

A simple calculational model is derived for use in estimating solar cosmic ray exposure to critical body organs in low-Earth orbit at the center of a large spherical shield of fixed thickness. The effects of the Earth's geomagnetic field, including storm conditions and the astronauts' self-shielding, are evaluated explicitly. The magnetic storm model is keyed to the planetary index K(sub p).

Wilson, John W.; Khandelwal, Govind S.; Shinn, Judy L.; Nealy, John E.; Townsend, Lawrence W.; Cucinotta, Francis A.

1990-01-01

228

Ballistic limit equations for spacecraft shielding  

Microsoft Academic Search

This paper provides equations describing the ballistic performance capability of meteoroid\\/orbital debris (M\\/OD) shield systems employed on the International Space Station (ISS). Hypervelocity impact (HVI) tests and analysis were used in developing the semi-empirical ballistic limit equations (BLE). A description of each type of shield system, HVI tests and analysis performed to assess shield performance, and ballistic limit equations that

Eric L. Christiansen; Justin H. Kerr

2001-01-01

229

The ORNL-SNAP shielding program  

NASA Technical Reports Server (NTRS)

The effort in the ORNL-SNAP shielding program is directed toward the development and verification of computer codes using numerical solutions to the transport equation for the design of optimized radiation shields for SNAP power systems. A brief discussion is given for the major areas of the SNAP shielding program, which are cross-section development, transport code development, and integral experiments. Detailed results are presented for the integral experiments utilizing the TSF-SNAP reactor. Calculated results are compared with experiments for neutron and gamma-ray spectra from the bare reactor and as transmitted through slab shields.

Mynatt, F. R.; Clifford, C. E.; Muckenthaler, F. J.; Gritzner, M. L.

1972-01-01

230

Accelerator magnet designs using superconducting magnetic shields  

SciTech Connect

Superconducting dipoles and quadrupoles for existing accelerators have a coil surrounded by an iron shield. The shield limits the fringe field of the magnet while having minimal effect on the field shape and providing a small enhancement of the field strength. Shields using superconducting materials can be thinner and lighter and will not experience the potential of a large de-centering force. Boundary conditions for these materials, material properties, mechanical force considerations, cryostat considerations and some possible geometrical configurations for superconducting shields will be described. 7 refs., 3 figs., 3 tabs.

Brown, B.C.

1990-10-01

231

Shielding for thermoacoustic tomography with RF excitation  

NASA Astrophysics Data System (ADS)

Radiofrequency (RF) pulses used to generate thermoacoustic computerized tomography (TCT) signal couple directly into the pulser-receiver and oscilloscope, swamping true TCT signal. We use a standard RF enclosure housing both RF amplifier and object being imaged. This is similar to RF shielding of magnetic resonance imaging (MRI) suites and protects electronics outside from stray RF. Unlike MRI, TCT receivers are ultrasound transducers, which must also be shielded from RF. A transducer housing that simultaneously shields RF and permits acoustic transmission was developed specifically for TCT. We compare TCT signals measured with and without RF shielding.

Mitchell, M.; Becker, G.; Dey, P.; Generotzky, J.; Patch, S. K.

2008-03-01

232

Tilted Earth  

NSDL National Science Digital Library

This is an activity about how the Earth's axial tilt causes its seasons. Learners will make a model using polystyrene spheres and a light bulb to represent the Earth-Sun system, showing why the tilt of the Earthâs spin axis causes its seasons due to variations in day length. This is Activity 7 in the Great Explorations in Math and Science (GEMS) guide titled Real Reasons for Seasons: Sun-Earth Connections. The resource guide is available for purchase from the Lawrence Hall of Science.

233

Decontaminating lead bricks and shielding  

SciTech Connect

Lead used for shielding is often surface contaminated with radioisotopes and is therefore a RCRA D008 mixed waste. The technology-based standard for treatment is macroencapsulation. However, decontaminating and recycling the clean lead is a more attractive solution. Los Alamos National Laboratory decontaminates material and equipment contaminated with radioisotopes. Decontaminating lead poses special problems because of the RCRA hazard classification and the size of the inventory, now about 50 tons and likely to grow substantially of planned decommissioning operations. Thus lead, in the form of bricks and other shield shapes, is surface contaminated with fission products. One of the best methods for contaminated lead is removing the superficial layer of contamination with an abrasive medium under pressure. For lead, a mixture of alumina with water and air at about 40 psig rapidly and effectively decontaminates the lead. The abrasive medium is sprayed onto the lead in a scaled-off area. The slurry of abrasive and particles of lead falls through a floor and is collected in a sump. A pump sends the slurry mixture back to the spray gun, creating a continuous process. The process generates small volumes of lead slurry that can be solidified and, because it passes the TCLP, is not a mixed waste. The decontaminated lead can be released for recycling.

Lussiez, G.

1994-02-01

234

Decontaminating lead bricks and shielding  

SciTech Connect

Lead used for shielding is often surface contaminated with radioisotopes and is therefore a RCRA D008 mixed waste. The technology-based standard for treatment is macroencapsulation. However, decontaminating and recycling the clean lead is a more attractive solution. Los Alamos National Laboratory decontaminates material and equipment contaminated with radioisotopes. Decontaminating lead poses special problems because of the RCRA hazard classification and the size of the inventory, now about 50 tons and likely to grow substantially because of planned decommissioning operations. This lead, in the form of bricks and other shield shapes, is surface contaminated with fission products. One of the best methods for decontaminating lead is removing the thin superficial layer of contamination with an abrasive medium trader pressure. For lead, a mixture of alumina with water and air at about 40 psig rapidly and effectively decontaminates the lead. The abrasive medium is sprayed onto the lead in a sealed-off area. The slurry of abrasive and particles of lead falls through a floor grating and is collected in a sump. A pump sends the slurry mixture back to the spray gun, creating a continuous process. The process generates small volumes of contaminated lead slurry that can be solidified and, because it passes the TCLP, is not a mixed waste. The decontaminated lead can be released for recycling.

Lussiez, G.W.

1993-05-01

235

Decontaminating lead bricks and shielding  

SciTech Connect

Lead used for shielding is often surface contaminated with radioisotopes and is therefore a RCRA D008 mixed waste. The technology-based standard for treatment is macroencapsulation. However, decontaminating and recycling the clean lead is a more attractive solution. Los Alamos National Laboratory decontaminates material and equipment contaminated with radioisotopes. Decontaminating lead poses special problems because of the RCRA hazard classification and the size of the inventory, now about 50 tons and likely to grow substantially because of planned decommissioning operations. This lead, in the form of bricks and other shield shapes, is surface contaminated with fission products. One of the best methods for decontaminating lead is removing the thin superficial layer of contamination with an abrasive medium trader pressure. For lead, a mixture of alumina with water and air at about 40 psig rapidly and effectively decontaminates the lead. The abrasive medium is sprayed onto the lead in a sealed-off area. The slurry of abrasive and particles of lead falls through a floor grating and is collected in a sump. A pump sends the slurry mixture back to the spray gun, creating a continuous process. The process generates small volumes of contaminated lead slurry that can be solidified and, because it passes the TCLP, is not a mixed waste. The decontaminated lead can be released for recycling.

Lussiez, G.W.

1993-01-01

236

The global control of silicate weathering rates and the coupling with physical erosion: new insights from rivers of the Canadian Shield  

Microsoft Academic Search

The chemical evolution of the surface of the Earth is controlled by the interaction of rainwaters, the atmosphere and the continental crust. That is the main reason why the knowledge of the parameters that control chemical denudation on Earth is of crucial importance. We report chemical and isotopic analyses for river waters from the Canadian Shield in order to estimate

Romain Millot; Jérôme Gaillardet; Bernard Dupré; Claude Jean Allègre

2002-01-01

237

Earth Systems  

NSDL National Science Digital Library

This self-contained module on Earth systems includes a range of fun activities that students can perform in the classroom and at home with family members. They impart important concepts such as observation, identification, measurement, and differentiation.

Science, Houghton M.

238

Earth's Surface  

NSDL National Science Digital Library

This self-contained module on Earth's crust includes a range of fun activities that students can perform in the classroom and at home with family members. They impart important concepts such as observation, identification, measurement, and differentiation.

Science, Houghton M.

239

Discover Earth  

NASA Technical Reports Server (NTRS)

Discover Earth is a NASA-funded project for teachers of grades 5-12 who want to expand their knowledge of the Earth system, and prepare to become master teachers who promote Earth system science in their own schools, counties, and throughout their state. Participants from the following states are invited to apply: Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Washington, DC. Teachers selected for the project participate in a two-week summer workshop conducted at the University of Maryland, College Park; develop classroom-ready materials during the workshop for broad dissemination; conduct a minimum of two peer training activities during the coming school year; and participate in other enrichment/education opportunities as available and desired. Discover Earth is a team effort that utilizes expertise from a range of contributors, and balances science content with hands-on classroom applications.

1997-01-01

240

Discover Earth  

NASA Technical Reports Server (NTRS)

Discover Earth is a NASA-funded project for teachers of grades 5-12 who want to expand their knowledge of the Earth system, and prepare to become master teachers who promote Earth system science in their own schools, counties, and throughout their state. Participants from the following states are invited to apply: Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Washington, DC. Teachers selected for the project participate in a two-week summer workshop conducted at the University of Maryland, College Park; develop classroom-ready materials during the workshop for broad dissemination; conduct a minimum of two peer training activities during the coming school year; and participate in other enrichment/education opportunities as available and desired. Discover Earth is a team effort that utilizes expertise from a range of contributors, and balances science content with hands-on classroom applications.

Steele, Colleen

1996-01-01

241

Earth Day  

NSDL National Science Digital Library

The State University of New York at Buffalo presents this History of Earth Day website. The goal of the site is that teachers and students can better understand the development and purpose of Earth Day. In addition to the history, SUNY-Buffalo has compiled a series of websites complete with projects associated with Earth Day, appropriate for children, high school students, and college undergrads. Furthermore, the legal aspect of Earth Day - environmental legislation, EPA standards, and Global Climate Change legislation - are also discussed on the site. A list of further sites is also provided if users want more information on this national effort to help solve environmental issues such as pollution, overpopulation, and global warming. Teachers will find this website both informative and helpful in developing appropriate teaching curricula connected to this holiday, while students can have fun learning and creating projects of their own that contribute to preserving the environment.

2007-04-19

242

Earth Tides.  

National Technical Information Service (NTIS)

The report explains that the effects of ocean tides on Earth tide observations can best be observed by a network of stations, varying in distance to the coast, which systematically monitor the ocean loading or attraction contributions to the observations....

B. D. Zetler J. T. Kus

1971-01-01

243

Simulation analysis for the materials shielding effectiveness of EMP  

Microsoft Academic Search

The theory of shielding is introduced, and the simulation model is built. The software based on the CST is applied to simulate and analyze the pulse waveform. The shielding effectiveness of different pulse width is computed. Comparing the pulse shielding effectiveness with continuous wave shielding effectiveness, there is consistent result approximately. And the shielding effectiveness based on the frequency function

Long Zhang; Xiaofeng Hu; Xinfu Lu; Genchun Zhu; Yongqiang Zhang

2011-01-01

244

Optimal application of multilayer shielding for maximal EM field attenuation  

Microsoft Academic Search

A two-surface cable shield periodic bondings and with either discrete or distributed excitation is analyzed. It is found that the bondings improve the overall shielding effectiveness of the cable shield at certain frequencies, but degrade the shielding at others. Certain criteria are established for better shielding. In the case of distributed excitation, the overall effective transfer functions of a two-surface

F. C. Yang; K. S. H. Lee

1982-01-01

245

Geometrical aspects of magnetic shielding at extremely low frequencies  

Microsoft Academic Search

The magnetic shielding effectiveness for closed and open shield structures is studied at extremely low frequencies. Analytical solutions are used for simple geometries, while more complex structures are evaluated using a finite-element method. Both highly conductive and ferromagnetic materials are studied, and their different shielding behavior is shown. Ferromagnetic shields give good results for small and closed shields and they

Lennart Hasselgren; Jorma Luomi

1995-01-01

246

Earth materials and earth dynamics  

SciTech Connect

In the project ''Earth Materials and Earth Dynamics'' we linked fundamental and exploratory, experimental, theoretical, and computational research programs to shed light on the current and past states of the dynamic Earth. Our objective was to combine different geological, geochemical, geophysical, and materials science analyses with numerical techniques to illuminate active processes in the Earth. These processes include fluid-rock interactions that form and modify the lithosphere, non-linear wave attenuations in rocks that drive plate tectonics and perturb the earth's surface, dynamic recrystallization of olivine that deforms the upper mantle, development of texture in high-pressure olivine polymorphs that create anisotropic velocity regions in the convecting upper mantle and transition zone, and the intense chemical reactions between the mantle and core. We measured physical properties such as texture and nonlinear elasticity, equation of states at simultaneous pressures and temperatures, magnetic spins and bonding, chemical permeability, and thermal-chemical feedback to better characterize earth materials. We artificially generated seismic waves, numerically modeled fluid flow and transport in rock systems and modified polycrystal plasticity theory to interpret measured physical properties and integrate them into our understanding of the Earth. This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL).

Bennett, K; Shankland, T. [and others

2000-11-01

247

Throughput of shielded twisted-pair cables using wire-shield modes in the presence of radio ingress  

Microsoft Academic Search

This paper investigates the achievable throughput of shielded twisted-pair (STP) copper cables exploiting alternative propagation modes. Treating the shield as joint common, we form wire-shield paths. The shield is expected to substantially reduce the amount of radio ingress entering the cable. Thus, we consider the impact of the shield effectiveness on the throughput limits. Using model and measurements presented in

M. Jakovljevic; T. Magesacher; P. O. Borjesson; M. Sanchez; S. Zazo

2009-01-01

248

Current status of methods for shielding analysis  

SciTech Connect

Current methods used in shielding analysis and recent improvements in those methods are discussed. The status of methods development is discussed based on needs cited at the 1977 International Conference on Reactor Shielding. Additional areas where methods development is needed are discussed.

Engle, W.W.

1980-01-01

249

Shielded Aluminum Flat-Conductor Cable  

NASA Technical Reports Server (NTRS)

Thin wiring harness stores compactly. Flat aluminum conductors glued between layers of polyimide. Aluminum shield surrounds insulated conductors. Outer layer polyimide. Aluminum shield reduces flexibility of cable and cable withstand only limited number of repetitions of sharp bending at same spot.

Farina, S.

1984-01-01

250

Thermal neutron shield and method of manufacture  

DOEpatents

A thermal neutron shield comprising concrete with a high percentage of the element Boron. The concrete is least 54% Boron by weight which maximizes the effectiveness of the shielding against thermal neutrons. The accompanying method discloses the manufacture of Boron loaded concrete which includes enriching the concrete mixture with varying grit sizes of Boron Carbide.

Brindza, Paul Daniel; Metzger, Bert Clayton

2013-05-28

251

Undulator Beam Pipe Magnetic Shielding Effect Tests.  

National Technical Information Service (NTIS)

The proposed stainless steel beampipe for the LCLS undulator has a measurable shielding effect on the magnetic field of the LCLS undulators. This note describes the tests used to determine the magnitude of the shielding effect, as well as deviations in th...

Z. Wolf

2010-01-01

252

Thermosetting polymer composites for EMI shielding applications  

Microsoft Academic Search

Efforts have been made towards developing lightweight EMI shielding thermosetting composites materials using room temperature curing epoxy novalac cyclo aliphatic amine hardener system. Average Shielding efficiency (SE) values (100 KHz to 1 GHz) of above 50 dB have been obtained for Carbon Fibre Reinforced Polymeric (CFRP) composite laminates, with variants of glass fabric and aluminium mesh included along with. Sandwich

S. Sankaran; S. Dasgupta; K. Ravi Sekhar; M. N. Jagdish Kumar

2006-01-01

253

Material shields against neutral atomic particle beams  

Microsoft Academic Search

A material shield designed to protect a spacecraft against an atomic particle beam will, of necessity, be quite massive; consequently, even modest fractional-weight savings would be significant. With this goal in mind, the particle stopping power and range in various materials were investigated. The lightest shield materials are compounds composed of hydrogen and other light elements.

S. W. Kash

1985-01-01

254

Chiroshield - A Salisbury/Dallenbach shield alternative  

NASA Astrophysics Data System (ADS)

The enhancement of impedance matching and the increased absorption afforded by the use of chiral materials are here combined with specified coated surfaces which act as screens or shields for use in radar cross-section management and control. These chiral shields offer attractive advantages with respect to broadband frequency response and reduced reflection when compared to their conventional counterparts.

Jaggard, D. L.; Engheta, N.; Liu, J.

1990-08-01

255

WASTE HANDLING BUILDING SHIELD WALL ANALYSIS  

Microsoft Academic Search

The scope of this analysis is to estimate the shielding wall, ceiling or equivalent door thicknesses that will be required in the Waste Handling Building to maintain the radiation doses to personnel within acceptable limits. The shielding thickness calculated is the minimum required to meet administrative limits, and not necessarily what will be recommended for the final design. The preliminary

D. Padula

2000-01-01

256

Whipple shield performance in the shatter regime  

Microsoft Academic Search

A series of hypervelocity impact tests have been performed on aluminum alloy Whipple shields to investigate failure mechanisms and performance limits in the shatter regime. Test results demonstrated a more rapid increase in performance than predicted by the latest iteration of the JSC Whipple shield ballistic limit equation (BLE) following the onset of projectile fragmentation. This increase in performance was

S. Ryan; M. Bjorkman; E. L. Christiansen

2011-01-01

257

Shielding Strategies for Human Space Exploration  

NASA Astrophysics Data System (ADS)

A group of twenty-nine scientists and engineers convened a 'Workshop on Shielding Strategies for Human Space Exploration' at the Lyndon B. Johnson Space Center in Houston, Texas. The provision of shielding for a Mars mission or a Lunar base from the hazards of space radiations is a critical technology since astronaut radiation safety depends on it and shielding safety factors to control risk uncertainty appear to be great. The purpose of the workshop was to define requirements for the development and evaluation of high performance shield materials and designs and to develop ideas regarding approaches to radiation shielding. The workshop was organized to review the recent experience on shielding strategies gained in studies of the 'Space Exploration Initiative (SEI),' to review the current knowledge base for making shield assessment, to examine a basis for new shielding strategies, and to recommend a strategy for developing the required technologies for a return to the moon or for Mars exploration. The uniqueness of the current workshop arises from the expected long duration of the missions without the protective cover of the geomagnetic field in which the usually small and even neglected effects of the galactic cosmic rays (GCR) can no longer be ignored. It is the peculiarity of these radiations for which the inter-action physics and biological action are yet to be fully understood.

Wilson, J. W.; Miller, J.; Konradi, A.; Cucinotta, F. A.

1997-12-01

258

Earth: Earth Science and Health  

NASA Technical Reports Server (NTRS)

A major new NASA initiative on environmental change and health has been established to promote the application of Earth science remote sensing data, information, observations, and technologies to issues of human health. NASA's Earth Sciences suite of Earth observing instruments are now providing improved observations science, data, and advanced technologies about the Earth's land, atmosphere, and oceans. These new space-based resources are being combined with other agency and university resources, data integration and fusion technologies, geographic information systems (GIS), and the spectrum of tools available from the public health community, making it possible to better understand how the environment and climate are linked to specific diseases, to improve outbreak prediction, and to minimize disease risk. This presentation is an overview of NASA's tools, capabilities, and research advances in this initiative.

Maynard, Nancy G.

2001-01-01

259

Regolith-Derived Heat Shield for Planetary Body Entry and Descent System with In Situ Fabrication  

NASA Technical Reports Server (NTRS)

In this paper we will discuss a new mass-efficient and innovative way of protecting high-mass spacecraft during planetary Entry, Descent & Landing (EDL). Heat shields fabricated in situ can provide a thermal-protection system (TPS) for spacecraft that routinely enter a planetary atmosphere. By fabricating the heat shield with space resources from regolith materials available on moons and asteroids, it is possible to avoid launching the heat-shield mass from Earth. Three regolith processing and manufacturing methods will be discussed: 1) oxygen & metal extraction ISRU processes produce glassy melts enriched in alumina and titania, processed to obtain variable density, high melting point and heat-resistance; 2) compression and sintering of the regolith yield low density materials; 3) in-situ derived high-temperature polymers are created to bind regolith particles together, with a lower energy budget.

Hogue, Michael D.; Mueller, Robert P.; Rasky, Daniel J.; Hintze, Paul E.; Sibille, Laurent

2011-01-01

260

Spacesuit Radiation Shield Design Methods  

NASA Technical Reports Server (NTRS)

Meeting radiation protection requirements during EVA is predominantly an operational issue with some potential considerations for temporary shelter. The issue of spacesuit shielding is mainly guided by the potential of accidental exposure when operational and temporary shelter considerations fail to maintain exposures within operational limits. In this case, very high exposure levels are possible which could result in observable health effects and even be life threatening. Under these assumptions, potential spacesuit radiation exposures have been studied using known historical solar particle events to gain insight on the usefulness of modification of spacesuit design in which the control of skin exposure is a critical design issue and reduction of blood forming organ exposure is desirable. Transition to a new spacesuit design including soft upper-torso and reconfigured life support hardware gives an opportunity to optimize the next generation spacesuit for reduced potential health effects during an accidental exposure.

Wilson, John W.; Anderson, Brooke M.; Cucinotta, Francis A.; Ware, J.; Zeitlin, Cary J.

2006-01-01

261

Background simulations and shielding calculations  

SciTech Connect

Key improvements in the sensitivity of the underground particle astrophysics experiments can only be achieved if the radiation causing background events in detectors is well understood and proper measures are taken to suppress it. The background radiation arising from radioactivity and cosmic-ray muons is discussed here together with the methods of its suppression. Different shielding designs are considered to attenuate gamma-rays and neutrons coming from radioactivity in rock and lab walls. Purity of materials used in detector construction is analysed and the background event rates due to the presence of radioactive isotopes in detector components are discussed. Event rates in detectors caused by muon-induced neutrons with and without active veto systems are presented leading to the requirements for the depth of an underground laboratory and the efficiency of the veto system.

Kudryavtsev, Vitaly A. [Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH (United Kingdom)

2011-04-27

262

Radiation Shielding Systems Using Nanotechnology  

NASA Technical Reports Server (NTRS)

A system for shielding personnel and/or equipment from radiation particles. In one embodiment, a first substrate is connected to a first array or perpendicularly oriented metal-like fingers, and a second, electrically conducting substrate has an array of carbon nanostructure (CNS) fingers, coated with an electro-active polymer extending toward, but spaced apart from, the first substrate fingers. An electric current and electric charge discharge and dissipation system, connected to the second substrate, receives a current and/or voltage pulse initially generated when the first substrate receives incident radiation. In another embodiment, an array of CNSs is immersed in a first layer of hydrogen-rich polymers and in a second layer of metal-like material. In another embodiment, a one- or two-dimensional assembly of fibers containing CNSs embedded in a metal-like matrix serves as a radiation-protective fabric or body covering.

Chen, Bin (Inventor); McKay, Christoper P. (Inventor)

2011-01-01

263

Electromagnetic interference shielding effectiveness of monolayer graphene.  

PubMed

We report the first experimental results on the electromagnetic interference (EMI) shielding effectiveness (SE) of monolayer graphene. The monolayer CVD graphene has an average SE value of 2.27 dB, corresponding to ~40% shielding of incident waves. CVD graphene shows more than seven times (in terms of dB) greater SE than gold film. The dominant mechanism is absorption rather than reflection, and the portion of absorption decreases with an increase in the number of graphene layers. Our modeling work shows that plane-wave theory for metal shielding is also applicable to graphene. The model predicts that ideal monolayer graphene can shield as much as 97.8% of EMI. This suggests the feasibility of manufacturing an ultrathin, transparent, and flexible EMI shield by single or few-layer graphene. PMID:23085718

Hong, Seul Ki; Kim, Ki Yeong; Kim, Taek Yong; Kim, Jong Hoon; Park, Seong Wook; Kim, Joung Ho; Cho, Byung Jin

2012-11-16

264

How Does the Sun Affect the Earth?  

NSDL National Science Digital Library

This is a unit of 8 sessions about the Sun-Earth system. Learners will construct a model to show the relative size and scale of the Sun-Earth system, investigate the visible and electromagnetic spectrums, discuss solar flares and solar weather, develop a UV shield, and discuss the results of their investigations. The unit is set in the context of solving a mystery and supports the idea that scientific explanations are based on evidence. This is Unit 1 of the GEMS Space Science Sequence for Grades 6-8, which is available for purchase (see related link).

265

Application of the NASA\\/JSC Whipple shield ballistic limit equations to dual-wall targets under hypervelocity impact  

Microsoft Academic Search

All Earth-orbiting spacecraft are susceptible to damage that can be caused by high-speed impacts with pieces of man-made debris or naturally-occurring meteoroids, and spacecraft at locations other than near Earth are subject to similar naturally-occurring hazards. Traditional protective shield design consists of a “bumper” that is placed at a relatively small distance away from the main “inner wall” of the

W. P. Schonberg; L. E. Compton

2008-01-01

266

Vehicle Shield Optimization and Risk Assessment for Future Human Space Missions  

NASA Technical Reports Server (NTRS)

As the focus of future human space missions shifts to destinations beyond low Earth orbit such as Near Earth Objects (NEO), the moon, or Mars, risks associated with extended stay in hostile radiation environment need to be well understood and assessed. Since future spacecrafts designs and shapes are evolving continuous assessments of shielding and radiation risks are needed. In this study, we use a predictive software capability that calculates risks to humans inside a spacecraft prototype that builds on previous designs. The software uses CAD software Pro/Engineer and Fishbowl tool kit to quantify radiation shielding provided by the spacecraft geometry by calculating the areal density seen at a certain point, dose point, inside the spacecraft. Shielding results are used by NASA-developed software, BRYNTRN, to quantify organ doses received in a human body located in the vehicle in case of solar particle event (SPE) during such prolonged space missions. Organ doses are used to quantify risks on astronauts health and life using NASA Space Cancer Model. The software can also locate shielding weak points-hotspots-on the spacecraft s outer surface. This capability is used to reinforce weak areas in the design. Results of shielding optimization and risk calculation on an exploration vehicle design for missions of 6 months and 30 months are provided in this study. Vehicle capsule is made of aluminum shell that includes main cabin and airlock. The capsule contains 5 sets of racks that surround working and living areas. Water shelter is provided in the main cabin of the vehicle to enhance shielding in case of SPE.

Nounu, Hatem N.; Kim, Myung-Hee; Cucinotta, Francis A.

2011-01-01

267

The Development of Ballistic Limit Equations for Dual-Wall Spacecraft Shielding: A Concise History and Suggestions for Future Development  

Microsoft Academic Search

All earth-orbiting spacecraft are susceptible to impacts by orbital debris particles, which can occur at extremely high speeds and can damage flight- and mission-critical systems. The traditional damage mitigating shield design for this threat consists of a \\

William P. Schonberg

268

MAGNETIC SHIELDING OF EXOMOONS BEYOND THE CIRCUMPLANETARY HABITABLE EDGE  

SciTech Connect

With most planets and planetary candidates detected in the stellar habitable zone (HZ) being super-Earths and gas giants rather than Earth-like planets, we naturally wonder if their moons could be habitable. The first detection of such an exomoon has now become feasible, and due to observational biases it will be at least twice as massive as Mars. However, formation models predict that moons can hardly be as massive as Earth. Hence, a giant planet's magnetosphere could be the only possibility for such a moon to be shielded from cosmic and stellar high-energy radiation. Yet, the planetary radiation belt could also have detrimental effects on exomoon habitability. Here we synthesize models for the evolution of the magnetic environment of giant planets with thresholds from the runaway greenhouse (RG) effect to assess the habitability of exomoons. For modest eccentricities, we find that satellites around Neptune-sized planets in the center of the HZ around K dwarf stars will either be in an RG state and not be habitable, or they will be in wide orbits where they will not be affected by the planetary magnetosphere. Saturn-like planets have stronger fields, and Jupiter-like planets could coat close-in habitable moons soon after formation. Moons at distances between about 5 and 20 planetary radii from a giant planet can be habitable from an illumination and tidal heating point of view, but still the planetary magnetosphere would critically influence their habitability.

Heller, René [McMaster University, Department of Physics and Astronomy, Hamilton, ON L8S 4M1 (Canada)] [McMaster University, Department of Physics and Astronomy, Hamilton, ON L8S 4M1 (Canada); Zuluaga, Jorge I., E-mail: rheller@physics.mcmaster.ca, E-mail: jzuluaga@fisica.udea.edu.co [FACom - Instituto de Física - FCEN, Universidad de Antioquia, Calle 70 No. 52-21, Medellín (Colombia)

2013-10-20

269

Magnetic Shielding of Exomoons beyond the Circumplanetary Habitable Edge  

NASA Astrophysics Data System (ADS)

With most planets and planetary candidates detected in the stellar habitable zone (HZ) being super-Earths and gas giants rather than Earth-like planets, we naturally wonder if their moons could be habitable. The first detection of such an exomoon has now become feasible, and due to observational biases it will be at least twice as massive as Mars. However, formation models predict that moons can hardly be as massive as Earth. Hence, a giant planet's magnetosphere could be the only possibility for such a moon to be shielded from cosmic and stellar high-energy radiation. Yet, the planetary radiation belt could also have detrimental effects on exomoon habitability. Here we synthesize models for the evolution of the magnetic environment of giant planets with thresholds from the runaway greenhouse (RG) effect to assess the habitability of exomoons. For modest eccentricities, we find that satellites around Neptune-sized planets in the center of the HZ around K dwarf stars will either be in an RG state and not be habitable, or they will be in wide orbits where they will not be affected by the planetary magnetosphere. Saturn-like planets have stronger fields, and Jupiter-like planets could coat close-in habitable moons soon after formation. Moons at distances between about 5 and 20 planetary radii from a giant planet can be habitable from an illumination and tidal heating point of view, but still the planetary magnetosphere would critically influence their habitability.

Heller, René; Zuluaga, Jorge I.

2013-10-01

270

Integrated Solar Concentrator and Shielded Radiator  

NASA Technical Reports Server (NTRS)

A shielded radiator is integrated within a solar concentrator for applications that require protection from high ambient temperatures with little convective heat transfer. This innovation uses a reflective surface to deflect ambient thermal radiation, shielding the radiator. The interior of the shield is also reflective to provide a view factor to deep space. A key feature of the shield is the parabolic shape that focuses incoming solar radiation to a line above the radiator along the length of the trough. This keeps the solar energy from adding to the radiator load. By placing solar cells along this focal line, the concentration of solar energy reduces the number and mass of required cells. By shielding the radiator, the effective reject temperature is much lower, allowing lower radiator temperatures. This is particularly important for lower-temperature processes, like habitat heat rejection and fuel cell operations where a high radiator temperature is not feasible. Adding the solar cells in the focal line uses the concentrating effect of the shield to advantage to accomplish two processes with a single device. This shield can be a deployable, lightweight Mylar structure for compact transport.

Clark, David Larry

2010-01-01

271

International Space Station Radiation Shielding Model Development  

NASA Technical Reports Server (NTRS)

The projected radiation levels within the International Space Station (ISS) have been criticized by the Aerospace Safety Advisory Panel in their report to the NASA Administrator. Methods for optimal reconfiguration and augmentation of the ISS shielding are now being developed. The initial steps are to develop reconfigurable and realistic radiation shield models of the ISS modules, develop computational procedures for the highly anisotropic radiation environment, and implement parametric and organizational optimization procedures. The targets of the redesign process are the crew quarters where the astronauts sleep and determining the effects of ISS shadow shielding of an astronaut in a spacesuit. The ISS model as developed will be reconfigurable to follow the ISS. Swapping internal equipment rack assemblies via location mapping tables will be one option for shield optimization. Lightweight shield augmentation materials will be optimally fit to crew quarter areas using parametric optimization procedures to minimize the augmentation shield mass. The optimization process is being integrated into the Intelligence Synthesis Environment s (ISE s) immersive simulation facility at the Langley Research Center and will rely on High Performance Computing and Communication (HPCC) for rapid evaluation of shield parameter gradients.

Qualls, G. D.; Wilson, J. W.; Sandridge, C.; Cucinotta, F. A.; Nealy, J. E.; Heinbockel, J. H.; Hugger, C. P.; Verhage, J.; Anderson, B. M.; Atwell, W.

2001-01-01

272

Graphitic heat shields for solar probe missions  

NASA Technical Reports Server (NTRS)

The feasibility of using a graphitic heat-shield system on a solar probe going to within 4 solar radii of the center of the sun is investigated. An analysis of graphite vaporization, with commonly used vaporization coefficients, indicates that the maximum mass-loss rate from a conical shield as large as 4 m in diameter can be kept low enough to avoid interference with measurements of the solar environment. In addition to the mass-loss problem, the problem of protecting the payload from the high-temperature (up to 2300 K) primary shield must be solved. An analysis of radiation exchange between concentric disks provides a technique for designing the intermediate shielding. The technique is applied to the design of a system for the Starprobe spacecraft, and it is found that a system with 10 shields and a payload surface temperature of 600 K will have a payload diameter of 2.45 m. Since this is 61% of the 4-m diameter of the primary shield, it is concluded that a graphitic heat-shield system is feasible for the Starprobe mission.

Lundell, J. H.

1981-01-01

273

Shielding options for the ITER conceptual design  

SciTech Connect

Several shield options were analyzed for the ITER conceptual design to minimize the nuclear responses in the toroidal field (TF) coils. The total nuclear heating in the physics phase and the insulator dose in the technology phase are the most critical parameters in the design process. The first shield option has type 316 stainless steel and water shielding material. Steel and water also serve as structural material and coolant, respectively. The second option is similar to the first except that borated water is used instead of ordinary water. The other two options include a small layer of lead or boron carbide (B{sub 4}C) at the back of the shield. The last three shield options were considered to reduce the nuclear heating in the toroidal field coils relative to the steel/water shield. An optimization process was performed taking into consideration the thermal-hydraulics and the engineering requirements to define the shield configuration. A careful integration was performed to calculate the total nuclear heating in the toroidal field coils which account for the neutron wall loading distribution, the change in the shield thickness in the poloidal direction, and the space between the toroidal field coils in the divertor zone. The results show that the steel/water/Pb and the steel/borated-water shield options are very close in terms of the total nuclear heating in the toroidal field coils and the dose in the insulator material. The other two options, steel/water and steel/water/B{sub 4}C deposit more nuclear heating in the toroidal field coils. 5 refs., 3 figs., 5 tabs.

Gohar, Y.; Attaya, H. (Argonne National Lab., IL (USA))

1989-10-01

274

Earth Structures  

NSDL National Science Digital Library

This web guide explores several natural phenomena that are constantly changing the face of the Earth. These geologic forces not only impact the physical features of our planet but ultimately affect the biosphere in a dramatic way. Historically, the changes have ranged from gradual (such as with the process of mountain building) to the spontaneous (such as with seismic events).

National Science Teachers Association (NSTA)

2005-04-01

275

Earth Movers  

NSDL National Science Digital Library

This lesson explores plate tectonics and helps students understand how mountains, earthquakes, and volcanoes are related to the movements of plates. Students will learn about the idea of continental drift and the theory of plate tectonics to ascertain a fuller picture of how land formations on the surface of the Earth are shaped by plates moving below the surface.

276

Visible Earth  

NSDL National Science Digital Library

This Web site provides a searchable directory of NASA Earth science images, animations and data visualizations. Most resources are available digitally at multiple resolutions, with captions and metadata. Users can search the database using full text and advanced searches by topic, keyword, sensor, location, parameter, and dates.

2001-01-01

277

Protecting Earth  

Microsoft Academic Search

\\u000a Intense tempests of celestial origin have blown through the skies of Earth, obliterating landscapes and sending towering tsunamis\\u000a through the oceans. Fallout from such events has extinguished vast numbers of living organisms; some of these have been altered\\u000a by geological processes into fossils.

Les Johnson; Gregory L. Matloff; C Bangs

278

MFTF-. cap alpha. + T shield design  

SciTech Connect

MFTF-..cap alpha..+T is a DT upgrade option of the Tandem Mirror Fusion Test Facility (MFTF-B) to study better plasma performance, and test tritium breeding blankets in an actual fusion reactor environment. The central cell insert, designated DT axicell, has a 2-MW/m/sup 2/ neutron wall loading at the first wall for blanket testing. This upgrade is completely shielded to protect the reactor components, the workers, and the general public from the radiation environment during operation and after shutdown. The shield design for this upgrade is the subject of this paper including the design criteria and the tradeoff studies to reduce the shield cost.

Gohar, Y.

1985-01-01

279

Optimization design of electromagnetic shielding composites  

NASA Astrophysics Data System (ADS)

The effective electromagnetic parameters physical model of composites and prediction formulas of composites' shielding effectiveness and reflectivity were derived based on micromechanics, variational principle and electromagnetic wave transmission theory. The multi-objective optimization design of multilayer composites was carried out using genetic algorithm. The optimized results indicate that material parameter proportioning of biggest absorption ability can be acquired under the condition of the minimum shielding effectiveness can be satisfied in certain frequency band. The validity of optimization design model was verified and the scheme has certain theoretical value and directive significance to the design of high efficiency shielding composites.

Qu, Zhaoming; Wang, Qingguo; Qin, Siliang; Hu, Xiaofeng

2013-03-01

280

Low background shielding of HPGe detector.  

PubMed

National Radiation Protection Institute in Prague is equipped with 14 HPGe detectors with relative efficiency up to 150%. Steel shielding with one of these detectors (relative efficiency 100%) was chosen to be rebuilt to decrease minimum detectable activity (MDA). Additional lead and copper shielding was built up inside the original steel shielding to reduce the volume of the inner space and filled with nitrogen by means of evaporating liquid nitrogen. MDA values decreased for Compton background up to 0.67 of original value. PMID:19243960

Trnková, L; Rulík, P

2009-05-01

281

Hot cell shield plug extraction apparatus  

DOEpatents

An apparatus is provided for moving shielding plugs into and out of holes in concrete shielding walls in hot cells for handling radioactive materials without the use of external moving equipment. The apparatus provides a means whereby a shield plug is extracted from its hole and then swung approximately 90 degrees out of the way so that the hole may be accessed. The apparatus uses hinges to slide the plug in and out and to rotate it out of the way, the hinge apparatus also supporting the weight of the plug in all positions, with the load of the plug being transferred to a vertical wall by means of a bolting arrangement.

Knapp, Philip A. (Moore, ID); Manhart, Larry K. (Pingree, ID)

1995-01-01

282

System requirements of Starprobe thermal shield  

NASA Technical Reports Server (NTRS)

The mission of the Starprobe Spacecraft is to do in situ exploration of the solar corona to four solar radii. A thermal shield is required to protect the spacecraft equipment from a 3000 sun incident solar energy level caused by this close approach to the sun. The thermal shield requirements discussed include configuration, material requirements, temperature level, penetrations, outgassing and mass loss, and contamination as referenced to spacecraft mission parameters. Further, the size of the spacecraft will be limited by the space transport system orbiter payload bay dimensions, thus defining the upper limit of the relative sizes and locations of the heat shield and spacecraft equipment.

Miyake, R. N.; Noon, D.; Hultberg, J. A.

1981-01-01

283

Flexible heat resistant neutron shielding resin  

NASA Astrophysics Data System (ADS)

A flexible heat resistant neutron shielding material has been developed, which consists of polymer resin with 1 wt% boron. The neutron shielding performance of the developed resin, examined by the 252Cf neutron source, is almost the same as that of the polyethylene. The outgas of H 2, H 2O, CO and CO 2 from the resin have been measured at ˜250 °C environment. The resin will be applied around the port of the vacuum vessel as an additional shielding material and reduce the neutron streaming from a superconducting tokamak device such as JT-60SA.

Sukegawa, Atsuhiko M.; Anayama, Yoshimasa; Okuno, Koichi; Sakurai, Shinji; Kaminaga, Atsushi

2011-10-01

284

Radiation shielding concrete made of Basalt aggregates.  

PubMed

In spite of the fact that Basalt is a widespread type of rock, there is very little available information on using it as aggregates for concrete radiation shielding. This paper investigates the possibility of using Basalt for the aforementioned purpose. The results have shown that Basalt could be used successfully for preparing radiation shielding concrete, but some attention should be paid to the choice of the suitable types of Basalt and for the neutron activation problem that could arise in the concrete shield. PMID:22933408

Alhajali, S; Yousef, S; Kanbour, M; Naoum, B

2013-04-01

285

Earth meandering  

NASA Astrophysics Data System (ADS)

In this paper we try to put away current Global Tectonic Model to look the tectonic evolution of the earth from new point of view. Our new dynamic model is based on study of river meandering (RM) which infer new concept as Earth meandering(EM). In a universal gravitational field if we consider a clockwise spiral galaxy model rotate above Ninety East Ridge (geotectonic axis GA), this system with applying torsion field (likes geomagnetic field) in side direction from Rocky Mt. (west geotectonic pole WGP) to Tibetan plateau TP (east geotectonic pole EGP),it seems that pulled mass from WGP and pushed it in EGP due to it's rolling dynamics. According to this idea we see in topographic map that North America and Green land like a tongue pulled from Pacific mouth toward TP. Actually this system rolled or meander the earth over itself fractaly from small scale to big scale and what we see in the river meandering and Earth meandering are two faces of one coin. River transport water and sediments from high elevation to lower elevation and also in EM, mass transport from high altitude-Rocky Mt. to lower altitude Himalaya Mt. along 'S' shape geodetic line-optimum path which connect points from high altitude to lower altitude as kind of Euler Elastica(EE). These curves are responsible for mass spreading (source) and mass concentration (sink). In this regard, tiltness of earth spin axis plays an important role, 'S' are part of sigmoidal shape which formed due to intersection of Earth rolling with the Earth glob and actual feature of transform fault and river meandering. Longitudinal profile in mature rivers as a part of 'S' curve also is a kind of EE. 'S' which bound the whole earth is named S-1(S order 1) and cube corresponding to this which represent Earth fracturing in global scale named C-1(cube order 1 or side vergence cube SVC), C-1 is a biggest cycle of spiral polygon, so it is not completely closed and it has separation about diameter of C-7. Inside SVC we introduce cone vergence cube (CVC or geotectonic equator GE) which rotate 45 degree counterclockwise with respect to SVC. Every cube from big scale to small scale fractalize in order of 23 and every '8' shape from big scale to small scale also fractalize in the same order. Three dimensional and fractoscopic imagination about understanding the changing on earth is very important so we should imagine '8' as curved surface, sea floor spreading happened in maximum curvature of these surfaces. '8' formed from pair 'S' string with opposite direction. '8' oscillate in Pole-Pole and Side-Side direction and have saddle geometry with two 'U' path along perpendicular saddle (e.g. Lut/Jazmurian and Helmand/Mashkal basin in Iran actually intersection of this saddle shape with the earth surface and Iceland /Black Sea and CapeVerde/Victoria Lake are also In/Out (small scale polygon) of 'U' shape conduit which followed axial saddle of Side-'S-2' and Okhotsk Sea /Balkhash Lake followed axial saddle conduit of Pole-'S-2' actually intersection of this perpendicular conduit with surface make spot-like-lakes/volcanoes or basin. Global EM in Side-S-1 bounded compression region-TP inside and tension region-East African Rift offside).This is a interesting competing between two kinematic geometry - spherical and isometrical geometry by using the interaction of them we can analyze the earth face in past, present and future apart of the forces that cause this face. C-1 in two dimensional look like six sided big tent which speared over Tibet and main rod driven along GA. Pair S-1 curve. have seven component(fold) and six segment in between,S-7 exactly located on TP(center of S-1). Between two successive fold we have complex geology(e.g. eastern Iran and Afghanistan)mass dragged from North America and Siberian and accumulated gradually during six step in Earth Foundation(Tibet),S-7 bounded Takla Makan Desert (in smaller loop) and TP (in bigger loop) S-7 alter the earth balance and responsible for earth disturbing, another sample of 'S' curve we see around Australia and Kermadec/Tonga Trench, Aleutian ri

Asadiyan, H.; Zamani, A.

2009-04-01

286

Characteristics of Whipple Shield Performance in the Shatter Regime  

NASA Technical Reports Server (NTRS)

Between the onset of projectile fragmentation and the assumption of rear wall failure due to an impulsive load, multi-wall ballistic limit equations are linearly interpolated to provide reasonable yet conservative predictions of perforation thresholds with conveniently simple mathematics. Although low velocity and hypervelocity regime predictions are based on analytical expressions, there is no such scientific foundation for predictions in the intermediate (or shatter) regime. As the debris flux in low earth orbit (LEO) becomes increasingly dominated by manmade pollution, the profile of micrometeoroid and orbital debris (MMOD) risk shifts continually towards lower velocities. For the International Space Station (ISS), encounter velocities below 7 km/s now constitute approximately 50% of the penetration risk. Considering that the transition velocity from shatter to hypervelocity impact regimes described by common ballistic limit equations (e.g. new non-optimum Whipple shield equation [1]) occurs at 7 km/s, 50% of station risk is now calculated based on failure limit equations with little analytical foundation. To investigate projectile and shield behavior for impact conditions leading to projectile fragmentation and melt, a series of hypervelocity impact tests have been performed on aluminum Whipple shields. In the experiments projectile diameter, bumper thickness, and shield spacing were kept constant, while rear wall thickness was adjusted to determine spallation and perforation limits at various impact velocities and angles. The results, shown in Figure 1 for normal and 45 impacts, demonstrated behavior that was not sufficiently described by the simplified linear interpolation of the NNO equation (also shown in Figure 1). Hopkins et al. [2] investigated the performance of a nominally-identical aluminum Whipple shield, identifying the effects of phase change in the shatter regime. The results (conceptually represented in Figure 2) were found to agree well with those obtained in this study at normal incidence, suggesting that shielding performance in the shatter regime could be well described by considering more complex phase conditions than currently implemented in most BLEs. Furthermore, evidence of these phase effects were found in the oblique test results, providing the basis for an empirical description of these effects that can be applied in MMOD risk assessment software. In this paper, results of the impact experiments are presented, and characteristics of target damage are evaluated. A comparison of intermediate velocity impact failure mechanisms in current BLEs are discussed and compared to the findings of the experimental study. Risk assessment calculations have been made on a simplified structure using currently implemented penetration equations and predicted limits from the experimental program, and the variation in perceived mission risk is discussed. It was found that ballistic limit curves that explicitly incorporated phase change effects within the intermediate regime lead to a decrease in predicted MMOD risk for ISS-representative orbits. When considered for all Whipple-based shielding configurations onboard the ISS, intermediate phase change effects could lead to significant variations in predicted mission risk.

Ryan, Shannon; Bjorkman, Michael; Christiansen, Eric L.

2009-01-01

287

Magnetic shielding of interplanetary spacecraft against solar flare radiation  

NASA Astrophysics Data System (ADS)

The ultimate objective of this work is to design, build, and fly a dual-purpose, piggyback payload whose function is to produce a large volume, low intensity magnetic field and to test the concept of using such a magnetic field (1) to protect spacecraft against solar flare protons, (2) to produce a thrust of sufficient magnitude to stabilize low satellite orbits against orbital decay from atmospheric drag, and (3) to test the magsail concept. These all appear to be capable of being tested using the same deployed high temperature superconducting coil. In certain orbits, high temperature superconducting wire, which has now been developed to the point where silver-sheathed high T sub c wires one mm in diameter are commercially available, can be used to produce the magnetic moments required for shielding without requiring any mechanical cooling system. The potential benefits of this concept apply directly to both earth-orbital and interplanetary missions. The usefulness of a protective shield for manned missions needs scarcely to be emphasized. Similarly, the usefulness of increasing orbit perigee without expenditure of propellant is obvious. This payload would be a first step in assessing the true potential of large volume magnetic fields in the US space program. The objective of this design research is to develop an innovative, prototype deployed high temperature superconducting coil (DHTSC) system.

Cocks, Franklin H.; Watkins, Seth

1993-07-01

288

A Solar-Powered Near Earth Object Resource Extractor  

Microsoft Academic Search

This paper is an offshoot of a project to study means of forming massive radiation- shielded structures using Near Earth Object (NEO) materials. The topic is the conceptual design of a solar-powered robotic craft to land on, attach to, and extract materials from, a typical NEO. A solar-powered trajectory to a candidate NEO is used to estimate requirements. A reconfigurable

Thilini Rangedera; Ravi Vanmali; Nilesh Shah; Waqar Zaidi; Narayanan Komerath

2005-01-01

289

Dose in critical body organs in low Earth orbit  

NASA Technical Reports Server (NTRS)

Human exposure to trapped radiations in low Earth orbit (LEO) are evaluated on the basis of a simple approximation of the human geometry for spherical shell shields of varying thickness. A data base is presented that may be used to make preliminary assessment of the impact of radiation exposure constraints on human performance. A sample impact assessment is discussed.

Wilson, J. W.; Cucinotta, F.

1984-01-01

290

High-Speed Computational Applications for Space Radiation Shielding Analysis  

NASA Astrophysics Data System (ADS)

Expanding knowledge of the complexities of the space radiation environment and its interactions with matter, coupled with greater burdens associated with budgetary and time constraints, have given impetus to the need for application of more sophisticated analyses in more abbreviated time spans. Recent work at NASA-LaRC in this area has resulted in development of high efficiency algorithms coupled with high speed computers and visualization hardware and software to analyze space radiation effects and shielding methodologies for advanced missions. Special interfacing with CAD solid models and 3-D immersive visualization equipment plays a major role in this endeavor. Recent applications have included analyses for EVA in a CAD-modeled STS space suit, for vector flux exposure in an ISS habitation module, and for preliminary exposure predictions within a conceptual habitation module at an Earth-Moon libration point. Execution times for these heretofore rather lengthy analyses have been reduced from matters of hours to matters of minutes.

Nealy, John E.; Anderson, Brooke M.; Wilson, John W.; Qualls, Garry D.

2003-01-01

291

Design of Reflective, Photonic Shields for Atmospheric Reentry  

NASA Technical Reports Server (NTRS)

We present the design of one-dimensional photonic crystal structures, which can be used as omnidirectional reflecting shields against radiative heating of space vehicles entering the Earth's atmosphere. This radiation is approximated by two broad bands centered at visible and near-infrared energies. We applied two approaches to find structures with the best omnidirectional reflecting performance. The first approach is based on a band gap analysis and leads to structures composed of stacked Bragg mirrors. In the second approach, we optimize the structure using an evolutionary strategy. The suggested structures are compared with a simple design of two stacked Bragg mirrors. Choice of the constituent materials for the layers as well as the influence of interlayer diffusion at high temperatures are discussed.

Komarevskiy, Nikolay; Shklover, Valery; Braginsky, Leonid; Hafner, Christian; Fabrichnaya, Olga; White, Susan; Lawson, John

2010-01-01

292

Risk assessment and late effects of radiation in low-earth orbits  

Microsoft Academic Search

The radiation dose rates in low-earth orbits are dependent on the altitude and orbital inclination. The doses to which the crews of space vehicles are exposed is governed by the duration of the mission and the shielding, and in low-earth orbit missions protons are the dominant particles encountered. The risk of concern with the low dose rates and the relatively

R. J. M. Fry

1989-01-01

293

The Clinical Testing of Male Gonad Shields.  

National Technical Information Service (NTIS)

Two types of male gonad shields, designed for use with support garments, were tested in a number of hospitals and clinics throughout the United States. The clinical evaluation consisted of: (1) Measuring dose reduction with thermoluminescent dosimeters; a...

W. W. Church, B. M. Burnett

1975-01-01

294

Boron-10 loaded inorganic shielding material  

NASA Technical Reports Server (NTRS)

Shielding material containing Boron 10 and gadoliunium for neutron absorption has been developed to reduce interference from low energy neutrons in measurement of fission neutron spectrum using Li-6 fast neutron spectrometer.

Baker, S. I.; Ryskiewicz, R. S.

1972-01-01

295

Resonance self-shielding methodology in MPACT  

SciTech Connect

The resonance self-shielding methods of the neutron transport code Michigan Parallel Characteristics based Transport (MPACT) are described in this paper. Two resonance-integral table based methods are utilized to resolve the resonance self-shielding effect. The subgroup method is a mature approach used in MPACT as the basic functionality for the resonance calculation. Another new iterative method, named the embedded self-shielding method is also implemented in MPACT. Comparisons of the two methods as well as their numerical verifications are presented. The results show that MPACT is capable of modeling the resonance self-shielding in a variety of PWR benchmarking cases, including difficult fuel lattice cases with poison, control rods or mixed gadolinia fuel rods. (authors)

Liu, Y.; Collins, B.; Kochunas, B.; Martin, W. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Blvd., Ann Arbor, MI, 48109 (United States)] [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Blvd., Ann Arbor, MI, 48109 (United States); Kim, K. S.; Williams, M. [Oak Ridge National Laboratory, One Bethel Valley Road, Oak Ridge, TN 37831-6172 (United States)] [Oak Ridge National Laboratory, One Bethel Valley Road, Oak Ridge, TN 37831-6172 (United States)

2013-07-01

296

Shield Design for Lunar Surface Applications  

NASA Astrophysics Data System (ADS)

A shielding concept for lunar surface applications of nuclear power is presented herein. The reactor, primary shield, reactor equipment and power generation module are placed in a cavity in the lunar surface. Support structure and heat rejection radiator panels are on the surface, outside the cavity. The reactor power of 1,320 kWt was sized to deliver 50 kWe from a thermoelectric power conversion subsystem. The dose rate on the surface is less than 0.6 mRem/hr at 100 meters from the reactor. Unoptimized shield mass is 1,020 kg which is much lighter than a comparable 4? shield weighing in at 17,000 kg.

Johnson, Gregory A.

2006-01-01

297

Projectile Density Effects on Shield Performance  

NASA Technical Reports Server (NTRS)

In the past, the orbital debris environment was modeled as consisting entirely of aluminum particles. As a consequence, most of the impact test database on spacecraft micro-meteoroid and orbital debris (MMOD) shields, and the resulting ballistic limit equations used to predict shielding performance, has been based on using aluminum projectiles. Recently, data has been collected from returned spacecraft materials and other sources that indicate higher and lower density components of orbital debris also exist. New orbital debris environment models such as ORDEM2008 provide predictions of the fraction of orbital debris in various density bins (high = 7.9 g/cu cm, medium = 2.8 g/cu cm, and low = 0.9-1.1 g/cu cm). This paper describes impact tests to assess the effects of projectile density on the performance capabilities of typical MMOD shields. Updates to shield ballistic limit equations are provided based on results of tests and analysis.

Christiansen, Eric L.; Lear, Dana; Lyons, Frankel; Davis, Alan

2009-01-01

298

Shielding Requirements for Particle Bed Propulsion Systems.  

National Technical Information Service (NTIS)

Nuclear Thermal Propulsion systems present unique challenges in reliability and safety. Due to the radiation incident upon all components of the propulsion system, shielding must be used to keep nuclear heating in the materials within limits; in addition,...

S. J. Gruneisen

1991-01-01

299

Injection Molding Compound for Electromagnetic Shielding.  

National Technical Information Service (NTIS)

A thermoplastic injection molding compound with excellent electromagnetic shielding effectiveness has been developed as a material for housings of electronic equipment. The compound contains stainless steel fiber as an electroconductive filler and maintai...

H. Takahama H. Tamaki T. Herai

1988-01-01

300

Charge and Potential Distributions in Shielded Striplines.  

National Technical Information Service (NTIS)

A new method is presented for calculating the charge and potential distribution in shielded microstrip lines with stratified dielectric fillings. The boundary value problem associated with this structure is formulated in a rigorous manner and the solution...

R. Mittra T. Itoh

1969-01-01

301

Fuel Tanks & Berms-McMurdo  

NSF Publications Database

... of fuels contaminated with such substances as water, dirt, oil, or antifreeze. Most waste fuel comes ... or with a metal, open-channel culvert. Dust emissions would be minimized by spraying water during ...

302

X-ray transmissive debris shield  

DOEpatents

A composite window structure is described for transmitting x-ray radiation and for shielding radiation generated debris. In particular, separate layers of different x-ray transmissive materials are laminated together to form a high strength, x-ray transmissive debris shield which is particularly suited for use in high energy fluences. In one embodiment, the composite window comprises alternating layers of beryllium and a thermoset polymer.

Spielman, Rick B. (Albuquerque, NM) [Albuquerque, NM

1994-01-01

303

CDF forward shielding for Run II  

SciTech Connect

Detailed calculations of the accelerator related background in the CDF forward muon spectrometer have been performed with the MARS13 code and a newly developed C++ code for particle tracking in accelerator lattices. Calculated space distributions of background hits are in a good agreement with data taken in Run I. Several shielding configurations in the CDF hall and Tevatron tunnel have been studied. The optimal one provides a 30-fold shielding efficiency compatible with CDF Run II requirements.

Krivosheev, O.E.; Mokhov, N.V.

1998-03-16

304

Nuclear reactor shield including magnesium oxide  

DOEpatents

An improvement in nuclear reactor shielding of a type used in reactor applications involving significant amounts of fast neutron flux, the reactor shielding including means providing structural support, neutron moderator material, neutron absorber material and other components as described below, wherein at least a portion of the neutron moderator material is magnesium in the form of magnesium oxide either alone or in combination with other moderator materials such as graphite and iron.

Rouse, Carl A. (Del Mar, CA); Simnad, Massoud T. (La Jolla, CA)

1981-01-01

305

Optimization of ferromagnetic shields for solenoid SMES  

SciTech Connect

Ferromagnetic shields for solenoidal superconducting magnetic energy storages (SMES) are optimized with respect to the stray field or the mass of the shield. Two optimization strategies of zero order are compared: the deterministic downhill simplex method and the evolution strategy, a stochastic method. Due to the comparison a combination of both methods is tested. To guarantee short computation times the underlying nonlinear field analysis is based on an integral equation method.

Brammer, U.; Rasch, P. [Technische Univ. Muenchen (Germany). Lehrstuhl fuer Elektrische Maschinen] [Technische Univ. Muenchen (Germany). Lehrstuhl fuer Elektrische Maschinen

1996-05-01

306

Undulator Beam Pipe Magnetic Shielding Effect Tests  

SciTech Connect

The proposed stainless steel beampipe for the LCLS undulator has a measurable shielding effect on the magnetic field of the LCLS undulators. This note describes the tests used to determine the magnitude of the shielding effect, as well as deviations in the shielding effect caused by placing different phase shims in the undulator gap. The effect of the proposed Steel strongback which will be used to support the beam pipe, was also studied. A hall probe on a 3 axis movement system was set up to measure the main component of the magnetic field in the Prototype Undulator. To account for temperature variations of the magnetic field of the undulator for successive tests, a correction is applied which is described in this technical note. Using this method, we found the shielding effect, the amount which the field inside the gap was reduced due to the placement of the beampipe, to be {approx}10 Gauss. A series of tests was also performed to determine the effect of phase shims and X and Y correction shims on the shielding. The largest effect on shielding was found for the .3 mm phase shims. The effect of the .3 mm phase shims was to increase the shielding effect {approx}4 Gauss. The tolerance for the shielding effect of the phase shims is less than 1 gauss. The effect of the strongback was seen in its permanent magnetic field. It introduced a dipole field across the measured section of the undulator of {approx}3 gauss. This note documents the tests performed to determine these effects, as well as the results of those tests.

Fisher, Andrew; Wolf, Zachary; /SLAC; ,

2010-11-23

307

Breathing Earth  

NSDL National Science Digital Library

Visual simulation and representation programs and applications have been popping up online in greater numbers, and this recent find is one that will pique the interest of scientists, policy makers, and others who are concerned about carbon dioxide emission rates across the Earth. The Breathing Earth site was created by David Bleja, and he draws on a number of resources (such as the World Factbook and the United Nations) for the data that is utilized to create this site. Visitors can scroll over different countries to learn about their population, their emissions, and their birth and death rate. This interactive map and educational resource also contains a legend in the right-hand corner which explains the various symbols in use here.

Bleja, David

308

Earth Institute  

NSDL National Science Digital Library

The mission of the Earth Institute at Columbia University is to help the world achieve sustainability by expanding understanding of the Earth as one integrated system. Through research, education, and the practical application of research to real-world challenges, the Institute addresses nine interconnected global issues: climate and society, water, energy, poverty, ecosystems, public health, food and nutrition, and hazards and urbanization. The Institute's site offers a collection of videotaped events, including the biannual "State of the Planet" conferences, 2002-08, a Distinguished Lecture series, and the Sustainable Development seminar series, as well as e-seminars and e-briefings, information about funding opportunities, and information about educational opportunities at Columbia.

309

Impact: Earth!  

NSDL National Science Digital Library

What would happen if a large meteorite or other object hit the Earth? It's something that has engaged the minds and talents of astrophysicists (and students of all ages) for decades. Now the generally curious can create their own simulated impact with Purdue University's "Impact Earth" website. Visitors can browse the Famous Craters area to get started. This part includes some "classics," such as the Ries Crater and the Tunguska Fireball. Of course, visitors really must use the handy interface to craft their own impact, projectile, and target parameters to get the full effect on how such an event plays out. Also, the site includes a complete Documentation file (a peer-reviewed article) and a detailed glossary.

2013-01-01

310

Earth plasmas  

NSDL National Science Digital Library

Fusion is the focus of this section of a tutorial about plasma, one of the four states of matter. This section deals with plasmas on Earth. There is little naturally-occurring plasma here because of the Earth's relatively cool (by universe standards) temperature, but human-made plasma is produced for industry and research purposes. The section explores the use of plasmas in experimental fusion reactors, pointing out three categories of significant unresolved issues that stand in the way of fusion becoming a viable energy source. The use of electromagnets to confine plasmas is discussed. Enlargeable images of fusion reactors are provided, and an explanation of the difference between fission and fusion is supplemented by animations of the two reaction types. Copyright 2005 Eisenhower National Clearinghouse

Institute, Space S.

2005-01-01

311

Reliability Methods for Shield Design Process  

NASA Technical Reports Server (NTRS)

Providing protection against the hazards of space radiation is a major challenge to the exploration and development of space. The great cost of added radiation shielding is a potential limiting factor in deep space operations. In this enabling technology, we have developed methods for optimized shield design over multi-segmented missions involving multiple work and living areas in the transport and duty phase of space missions. The total shield mass over all pieces of equipment and habitats is optimized subject to career dose and dose rate constraints. An important component of this technology is the estimation of two most commonly identified uncertainties in radiation shield design, the shielding properties of materials used and the understanding of the biological response of the astronaut to the radiation leaking through the materials into the living space. The largest uncertainty, of course, is in the biological response to especially high charge and energy (HZE) ions of the galactic cosmic rays. These uncertainties are blended with the optimization design procedure to formulate reliability-based methods for shield design processes. The details of the methods will be discussed.

Tripathi, R. K.; Wilson, J. W.

2002-01-01

312

Reliability Methods for Shield Design Process  

NASA Astrophysics Data System (ADS)

Providing protection against the hazards of space radiation is a major challenge to the exploration and development of space. The great cost of added radiation shielding is a potential limiting factor in deep space operations. In this enabling technology, we have developed methods for optimized shield design over multi-segmented missions involving multiple work and living areas in the transport and duty phase of space missions. The total shield mass over all pieces of equipment and habitats is optimized subject to career dose and dose rate constraints. An important component of this technology is the estimation of two most commonly identified uncertainties in radiation shield design, the shielding properties of materials used and the understanding of the biological response of the astronaut to the radiation leaking through the materials into the living space. The largest uncertainty, of course, is in the biological response to especially high charge and energy (HZE) ions of the galactic cosmic rays. These uncertainties are blended with the optimization design procedure to formulate reliability-based methods for shield design processes. The details of the methods will be discussed.

Tripathi, R. K.; Wilson, J. W.

2003-01-01

313

Earth's Water  

NSDL National Science Digital Library

The total amount of water on Earth, the places in which it is found and the percentages of fresh vs. salt are examined in this lesson. A short demonstration allows students to visualize the percentage differences and a coloring exercise illustrates locations. This lesson uses the 5E instructional model. All background information, student worksheets and images/photographs/data are included in these downloadable sections: Teacher's Guide, Student Capture Sheet and PowerPoint Presentation.

314

Earth's Biomes  

NSDL National Science Digital Library

What are the characteristics of Earth's biomes? First, open the Biomes Graphic Organizer Now read through Information on Aquatic Biome (Freshwater) and fill in 5 characterestics of a freshwater biome in your graphic organizer. Now read through Information on Desert and fill in 5 characteristics of a desert biome in your graphic organizer. Now read through Information on Rainforest and fill in 5 characteristics of rainforest biome in your graphic organizer. Now ...

Allman, Ms.

2012-04-05

315

Earth Observatory  

NSDL National Science Digital Library

This Web site includes shares the images, stories and discoveries that emerge from NASA Earth science research, including its satellite missions, in-the-field research and climate models. View global maps of NASA data, check out the Image of the Day and images of current events, and read feature articles and blogs. Also includes special collections of NASA images, including the World of Change series, which documents how our planetâs land, oceans, atmosphere and Sun are changing over time.

2011-01-01

316

Earth Observations  

NASA Technical Reports Server (NTRS)

This document is concentrates on a couple of the missions where the Spacelab hardware was used to do Earth science. The Atmospheric Laboratory for Applications and Science (ATLAS) series of missions and the Lidar in-Space Technology Experiment (LITE) mission, the ATLAS being a series of three Shuttle missions that were very much Spacelab missions, are described. A little bit about the history, what the missions were, some of the instruments that were on them, and results are given.

Kaye, Jack

2000-01-01

317

Impact Earth  

NSDL National Science Digital Library

This 24 minute planetarium show teaches about meteors, meteorites, asteroids, and comets. The show was created for fulldome theaters, but is also available on DVD to be shown in flat version for TVs and computer monitors, and can be freely viewed online. It shows the effects of the Chixulub and Tungusta events, plus the Pallasite impact that resulted in the Brenham meteorite fall, and describes ways that asteroid hunters seek new objects in the solar system, and how ground penetrating radar is used to find meteorites that have survived to the Earth's surface. Narrated by astronaut Tom Jones, it also discusses ways that humans might try to deflect an asteroid or comet that is on a collision course with Earth. The show was created for informal science venues (digital planetariums); it is also useful as supplemental material for middle school science. Impact Earth is available for free if presented directly from the Space Update site (widescreen or fisheye views linked from YouTube). Otherwise, a DVD of the show can be purchased for $10.

318

Space Shielding Materials for Prometheus Application  

SciTech Connect

At the time of Prometheus program restructuring, shield material and design screening efforts had progressed to the point where a down-selection from approximately eighty-eight materials to a set of five ''primary'' materials was in process. The primary materials were beryllium (Be), boron carbide (B{sub 4}C), tungsten (W), lithium hydride (LiH), and water (H{sub 2}O). The primary materials were judged to be sufficient to design a Prometheus shield--excluding structural and insulating materials, that had not been studied in detail. The foremost preconceptual shield concepts included: (1) a Be/B{sub 4}C/W/LiH shield; (2) a Be/B{sub 4}C/W shield; (3) and a Be/B{sub 4}C/H{sub 2}O shield. Since the shield design and materials studies were still preliminary, alternative materials (e.g., {sup nal}B or {sup 10}B metal) were still being screened, but at a low level of effort. Two competing low mass neutron shielding materials are included in the primary materials due to significant materials uncertainties in both. For LiH, irradiation-induced swelling was the key issue, whereas for H{sub 2}O, containment corrosion without active chemistry control was key, Although detailed design studies are required to accurately estimate the mass of shields based on either hydrogenous material, both are expected to be similar in mass, and lower mass than virtually any alternative. Unlike Be, W, and B{sub 4}C, which are not expected to have restrictive temperature limits, shield temperature limits and design accommodations are likely to be needed for either LiH or H{sub 2}O. The NRPCT focused efforts on understanding swelting of LiH, and observed, from approximately fifty prior irradiation tests, that either casting ar thorough out-gassing should reduce swelling. A potential contributor to LiH swelling appears to be LiOH contamination due to exposure to humid air, that can be eliminated by careful processing. To better understand LiH irradiation performance and mitigate the risks in LiH development for a project with an aggressive schedule like JIMO, some background or advanced development effort for LiH should be considered for future space reactor projects.

R. Lewis

2006-01-20

319

Shielding of manned space vehicles against protons and alpha particles  

NASA Technical Reports Server (NTRS)

The available information on the shielding of manned space vehicles against protons and alpha particles is summarized. The emphasis is placed on shielding against Van Allen belt protons and against solar-flare protons and alpha particles, but information on shielding against galactic cosmic rays is also presented. The approximation methods for use by nonexperts in the space shielding field are those that are standard in the space shielding literature.

Alsmiller, R. G., Jr.; Santoro, R. T.; Barish, J.; Claiborne, H. C.

1972-01-01

320

Radiation Protection Quantities for Near Earth Environments  

NASA Technical Reports Server (NTRS)

As humans travel beyond the protection of the Earth's magnetic field and mission durations grow, risk due to radiation exposure will increase and may become the limiting factor for such missions. Here, the dosimetric quantities recommended by the National Council on Radiation Protection and Measurements (NCRP) for the evaluation of health risk due to radiation exposure, effective dose and gray-equivalent to eyes, skin, and blood forming organs (BFO), are calculated for several near Earth environments. These radiation protection quantities are evaluated behind two different shielding materials, aluminum and polyethylene. Since exposure limits for missions beyond low Earth orbit (LEO) have not yet been defined, results are compared to limits recommended by the NCRP for LEO operations.

Clowdsley, Martha S.; Wilson, John W.; Kim, Myung-Hee; Anderson, Brooke M.; Nealy, John E.

2004-01-01

321

Effects of bumper size on high velocity impact damage to Whipple shield  

NASA Astrophysics Data System (ADS)

With the increasing number of space mission the impact risk on spacecraft at hypervelocity by space debris is increasing A collision with space debris can cause damage to a spacecraft in low Earth orbit For designing spacecraft protection constructions and developing advanced debris shieldsLhypervelocity impact simulation experiments on the ground and the computer simulation of hypervelocity impact is the important means The choice of shields modle sizes is a important step both in the experiments and computer simulation Whipple shields are the basic structure configuration for protecting spacecraft from meteoroid and orbital debris and are still extensively adopted This paper explores the bumper size effects on the damage produced by high velocity impacts on Wipple shields Tests were performed using the non-powder two-stage light gas gun facilities at Hypervelocity Impact Research Center at Harbin Institute of Technology The configuration of Wipple shields consisted of various sizes 1 mm thickness bumpers and constant size 3 mm thickness rear wall with 10 cm space btween the bumper and the rear wall The bumpers used for the tests were made up of 8 12 16 and 20 cm square plate made from 2A12 Aluminum All tests were performed with 4 mm in diameter aluminum projectile at velocity ranging from 1 45 to 1 71 km s The limit velocity of projectile impacting on the Whipple shields in over 0 8 probability of penetration of rear wall in probability of no-penetration of rear wall and on critical penetration condition of rear wall was shown to

Ha, Y.; Guan, G. S.; Pang, B. J.; Zhang, W.

322

Earth's Orbit  

NSDL National Science Digital Library

In this activity, learners draw a circle with a single focus, an ellipse with two foci close together, and an ellipse with two foci far apart, and compare the shapes. Learners then measure the Sun in four images each taken in a different season, comparing the apparent size of the Sun in each image to determine when Earth is closest to the Sun. This is the second activity in the SDO Secondary Learning Unit. The activity is reprinted with permission from the Great Explorations in Math and Science (GEMS).

323

Earth Gauge  

NSDL National Science Digital Library

Earth Gauge is a free environmental information service for broadcast meteorologists in major U.S. media markets, based on the 3-5 day forecast. The service is designed to make it easy to talk about the links between weather and the environment on-air with simple "factoids" and viewer action tips. Teachers or students can browse an index of weather conditions, environmental impacts, and viewer action tips for many locations, organized by city, weather type, or environmental topic. There are also links to additional resources, including fact sheets and special features, imagery, video clips, and others.

324

Design considerations for a Space Station radiation shield for protection from both man-made and natural sources  

NASA Technical Reports Server (NTRS)

This study was conducted to analyze scenarios involving the use of nuclear-power vehicles in the vicinity of a manned Space Station (SS) in low-earth-orbit (LEO) to quantify their radiological impact to the station crew. In limiting the radiant dose to crew members, mission planners may (1) shut the reactor down prior to reentry, (2) position the vehicle at a prescribed parking distance, and (3) deploy radiation shield about the shutdown reactor. The current report focuses on the third option in which point-kernel gamma-ray shielding calculations were performed for a variety of shield configurations for both nuclear electric propulsion (NEP) and nuclear thermal rocket (NTR) vehicles. For a returning NTR vehicle, calculations indicate that a 14.9 MT shield would be needed to limit the integrated crew exposure to no more than 0.05 Sv over a period of six months (25 percent of the allowable exposure to man-made radiation sources). During periods of low vehicular activity in LEO, the shield may be redeployed about the SS habitation module in order to decrease crew exposures to trapped proton radiations by approximately a factor of 10. The corresponding shield mass required for deployment at a returning NEP vehicle is 2.21 MT. Additional scenarios examined include the radioactivation of various metals as might be found in tools used in EVA activities.

Bolch, Wesley E.; Peddicord, K. Lee; Felsher, Harry; Smith, Simon

1994-01-01

325

Earth Structure: Layers of the Earth  

NSDL National Science Digital Library

This interactive Flash allows users to explore Earth's structure and processes that occur on Earth such as earthquakes and plate tectonics and how scientists know the composition and state of the Earth's layers. Interactive diagrams and animations with supplementary information make this a helpful overview or review for high school and undergraduate introductory-level courses in physical geology and Earth sciences.

Smoothstone; Mifflin, Houghton

326

Investigation of neutron shielding efficiency and radioactivity of concrete shields containing colemanite  

NASA Astrophysics Data System (ADS)

In this work, colemanite, a boron-bearing ore, was added to ordinary Portland concrete as aggregate. Some concrete blocks containing different amounts of colemanite were produced and their neutron permeability and compressive strength were determined. From the results of the experiments, taking into account the nuclear and structural properties of shielding material, a proper colemanite adding ratio was presented. A neutron transport calculation of the shield containing colemanite was made by using the removal-diffusion technique and the decrease in shield thickness, compared to ordinary Portland concrete, was found. Assuming a 20-year stepwise irradiation, the neutron-induced activity within the shield was calculated. Cooling time after shutdown was taken up to 10 5 years. By comparing the total and elemental activities of the ordinary and colemanite-added Portland concretes, the contribution of colemanite to the shield activity was investigated.

Yarar, Yasemin; Bayülken, Ahmet

1994-09-01

327

Asymmetric Electrostatic Radiation Shielding for Spacecraft  

NASA Technical Reports Server (NTRS)

A paper describes the types, sources, and adverse effects of energetic-particle radiation in interplanetary space, and explores a concept of using asymmetric electrostatic shielding to reduce the amount of such radiation impinging on spacecraft. Typically, such shielding would include a system of multiple inflatable, electrically conductive spheres deployed in clusters in the vicinity of a spacecraft on lightweight structures that would maintain the spheres in a predetermined multipole geometry. High-voltage generators would maintain the spheres at potential differences chosen in conjunction with the multipole geometry so that the resulting multipole field would gradually divert approaching energetic atomic nuclei from a central region occupied by the spacecraft. The spheres nearest the center would be the most positive, so as to repel the positively charged impinging nuclei from the center. At the same time, the monopole potential of the overall spacecraft-and-shielding system would be made negative so as to repel thermal electrons. The paper presents results of computational simulations of energetic-particle trajectories and shield efficiency for a trial system of 21 spheres arranged in three clusters in an overall linear quadrupole configuration. Further development would be necessary to make this shielding concept practical.

Metzger, Philip T.; Youngquist, Robert C.; Lane, John E.

2005-01-01

328

Advances in space radiation shielding codes  

NASA Technical Reports Server (NTRS)

Early space radiation shield code development relied on Monte Carlo methods and made important contributions to the space program. Monte Carlo methods have resorted to restricted one-dimensional problems leading to imperfect representation of appropriate boundary conditions. Even so, intensive computational requirements resulted and shield evaluation was made near the end of the design process. Resolving shielding issues usually had a negative impact on the design. Improved spacecraft shield design requires early entry of radiation constraints into the design process to maximize performance and minimize costs. As a result, we have been investigating high-speed computational procedures to allow shield analysis from the preliminary concept to the final design. For the last few decades, we have pursued deterministic solutions of the Boltzmann equation allowing field mapping within the International Space Station (ISS) in tens of minutes using standard Finite Element Method (FEM) geometry common to engineering design methods. A single ray trace in such geometry requires 14 milliseconds and limits application of Monte Carlo methods to such engineering models. A potential means of improving the Monte Carlo efficiency in coupling to spacecraft geometry is given.

Wilson, John W.; Tripathi, Ram K.; Qualls, Garry D.; Cucinotta, Francis A.; Prael, Richard E.; Norbury, John W.; Heinbockel, John H.; Tweed, John; De Angelis, Giovanni

2002-01-01

329

Correlated Uncertainties in Radiation Shielding Effectiveness  

NASA Technical Reports Server (NTRS)

The space radiation environment is composed of energetic particles which can deliver harmful doses of radiation that may lead to acute radiation sickness, cancer, and even death for insufficiently shielded crew members. Spacecraft shielding must provide structural integrity and minimize the risk associated with radiation exposure. The risk of radiation exposure induced death (REID) is a measure of the risk of dying from cancer induced by radiation exposure. Uncertainties in the risk projection model, quality factor, and spectral fluence are folded into the calculation of the REID by sampling from probability distribution functions. Consequently, determining optimal shielding materials that reduce the REID in a statistically significant manner has been found to be difficult. In this work, the difference of the REID distributions for different materials is used to study the effect of composition on shielding effectiveness. It is shown that the use of correlated uncertainties allows for the determination of statistically significant differences between materials despite the large uncertainties in the quality factor. This is in contrast to previous methods where uncertainties have been generally treated as uncorrelated. It is concluded that the use of correlated quality factor uncertainties greatly reduces the uncertainty in the assessment of shielding effectiveness for the mitigation of radiation exposure.

Werneth, Charles M.; Maung, Khin Maung; Blattnig, Steve R.; Clowdsley, Martha S.; Townsend, Lawrence W.

2013-01-01

330

Microscreen radiation shield for thermoelectric generator  

DOEpatents

The present invention provides a microscreen radiation shield which reduces radiative heat losses in thermoelectric generators such as sodium heat engines without reducing the efficiency of operation of such devices. The radiation shield is adapted to be interposed between a reaction zone and a means for condensing an alkali metal vapor in a thermoelectric generator for converting heat energy directly to electrical energy. The radiation shield acts to reflect infrared radiation emanating from the reaction zone back toward the reaction zone while permitting the passage of the alkali metal vapor to the condensing means. The radiation shield includes a woven wire mesh screen or a metal foil having a plurality of orifices formed therein. The orifices in the foil and the spacing between the wires in the mesh is such that radiant heat is reflected back toward the reaction zone in the interior of the generator, while the much smaller diameter alkali metal atoms such as sodium pass directly through the orifices or along the metal surfaces of the shield and through the orifices with little or no impedance.

Hunt, Thomas K. (Ann Arbor, MI); Novak, Robert F. (Farmington Hills, MI); McBride, James R. (Ypsilanti, MI)

1990-01-01

331

Effective shielding is more than a pretty facade  

NASA Astrophysics Data System (ADS)

The least understood of many elements which the designer has to consider in connection with electromagnetic compatibility problems is, perhaps, related to shielding. Electromagnetic shields are metallic barriers used to contain or reduce the coupling of electromagnetic energy. Maxwell's equations for time-varying fields can be used for an analysis of the effectiveness of a shielding barrier. However, these equations can become quite complex even for simple models. For this reason, transmission line theory, applied to shielding applications, has been employed to determine total shielding effectiveness. The design of suitable shielding barriers is discussed. The material employed can consist of metal, including high-permeability materials, and plastics with a conductive medium. Attention is given to approaches for accessing the interior of the shielded space, the ideal shielding joint, a reusable sealing method, conductive gaskets, conductive elastomers, correct grounding, the shielding of cables, and the use of waveguides.

Scheps, R. D.

1984-10-01

332

High purity silica reflective heat shield development  

NASA Technical Reports Server (NTRS)

A hyperpure vitreous silica material is being developed for use as a reflective and ablative heat shield for planetary entry. Various purity grades and forms of raw materials were evaluated along with various processing methods. Slip casting of high purity grain was selected as the best processing method, resulting in a highly reflective material in the wavelength bands of interest (the visible and ultraviolet regions). The selected material was characterized with respect to optical, mechanical and physical properties using a limited number of specimens. The process has been scaled up to produce a one-half scale heat shield (18 in. dia.) (45.72 cm) for a Jupiter entry vehicle. This work is now being extended to improve the structural safety factor of the heat shield by making hyperpure silica material tougher through the addition of silica fibers.

Nachtscheim, P. R.; Blome, J. C.

1976-01-01

333

Electromagnetic Shielding Efficiency Measurement of Composite Materials  

NASA Astrophysics Data System (ADS)

This paper deals with the theoretical and practical aspects of the shielding efficiency measurements of construction composite materials. This contribution describes an alternative test method of these measurements by using the measurement circular flange. The measured results and parameters of coaxial test flange are also discussed. The measurement circular flange is described by measured scattering parameters in the frequency range from 9 kHz up to 1 GHz. The accuracy of the used shielding efficiency measurement method was checked by brass calibration ring. The suitability of the coaxial test setup was also checked by measurements on the EMC test chamber. This data was compared with the measured data on the real EMC chamber. The whole measurement of shielding efficiency was controlled by the program which runs on a personal computer. This program was created in the VEE Pro environment produced by © Agilent Technology.

D?ínovský, J.; Kejík, Z.

2009-01-01

334

Heating profiles on ICRF antenna Faraday shields  

SciTech Connect

A conceptual design for an uncooled Faraday shield for the BPX ion cyclotron resonance heating (ICRH) antenna, which should withstand the proposed long-pulse operation, has been completed. A high-heat-flux, uncooled Faraday shield has also been designed for the fast-wave current drive (FWCD) antenna on D3-D. For both components, the improved understanding of the heating profiles made it possible to design for heat fluxes that would otherwise have been too close to mechanically established limits. The analytical effort is described in detail, with emphasis on the design work for the BPX ICRH antenna conceptual design and for the replacement Faraday shield for the D3-D FWCD antenna. Results of analyses are shown, and configuration issues involved in component modeling are discussed. 3 refs., 6 figs., 2 tabs.

Taylor, D.J.; Baity, F.W.; Hahs, C.L.; Riemer, B.W.; Ryan, P.M.; Williamson, D.E.

1991-01-01

335

Electronics Shielding and Reliability Design Tools  

NASA Technical Reports Server (NTRS)

It is well known that electronics placement in large-scale human-rated systems provides opportunity to optimize electronics shielding through materials choice and geometric arrangement. For example, several hundred single event upsets (SEUs) occur within the Shuttle avionic computers during a typical mission. An order of magnitude larger SEU rate would occur without careful placement in the Shuttle design. These results used basic physics models (linear energy transfer (LET), track structure, Auger recombination) combined with limited SEU cross section measurements allowing accurate evaluation of target fragment contributions to Shuttle avionics memory upsets. Electronics shielding design on human-rated systems provides opportunity to minimize radiation impact on critical and non-critical electronic systems. Implementation of shielding design tools requires adequate methods for evaluation of design layouts, guiding qualification testing, and an adequate follow-up on final design evaluation including results from a systems/device testing program tailored to meet design requirements.

Wilson, John W.; ONeill, P. M.; Zang, Thomas A., Jr.; Pandolf, John E.; Koontz, Steven L.; Boeder, P.; Reddell, B.; Pankop, C.

2006-01-01

336

Aluminum Shield under Hypervelocity Impact of Mylar Flyer up to 10 km/s.  

NASA Astrophysics Data System (ADS)

The near-earth space environment is cluttered with man-made debris and naturally occurring meteoroids, which is a big menace to the safety of satellites and spacecrafts. This paper is addressed on the failure response of aluminum shield under milligrame level debris or meteorids with around 10 km/s velocity. A compacted electric gun is employed to accelerate mylar flyer with 8-10 mm diameter up to 10 km/s. The spallation is observed in the rear free surface of 4 mm thick monolithic aluminum shield, and its fracture mechanism changes from plastic to brittle when flyer velocity is above 6 km/s. Once the boundary of aluminum plate is fixed except the loaded area, a through hole with 8mm diameter in the impacted area of the shield is observed after which was impacted by 0.1 mm thick mylar flyer with 6km/s. Three layers of shield is impacted by a myler flyer with velocity up to 10 km/s, debris clouds are observed in the first and the second gaps during the impact process by high speed camera, and its leftover can also be observed on the surface of the third plate.

Zhao, Jianheng; Tan, Fuli; Sun, C.; Liu, C.; Ravichandran, G.

2007-06-01

337

Electromagnetic fields and torque for a rotating gyroscope with a superconducting shield  

NASA Technical Reports Server (NTRS)

In a proposed experiment, a measurement is to be made of the angular precession of a rotating superconducting gyroscope for the purpose of testing different general-relativity theories. For various reasons having to do with the design of the experiment, the superconducting shield surrounding the gyroscope is not spherically symmetric and produces a torque. There are two distinct features of the shield which lead to a torque on the gyroscope. First, its shape is a sphere intersected by a plane. If the angular momentum of the gyroscope is not parallel to the rotational symmetry axis of the shield, there is a torque which is calculated. Second, there are small holes in the spherical portion of the shield. The earth's field can penetrate through these holes and give an additional torque which is also calculated. In the actual experiment, these torques must be accurately known or made very small in order to obtain meaningful results. The present calculation is sufficiently general for application over a wide range of experimental design parameters.

Ebner, C.; Sung, C. C.

1975-01-01

338

Sulfur Earth  

NASA Astrophysics Data System (ADS)

Variations in surface tension affect the buoyancy of objects floating in a liquid. Thus an object floating in water will sink deeper in the presence of dishwater fluid. This is a very minor but measurable effect. It causes for instance ducks to drown in aqueous solutions with added surfactant. The surface tension of liquid iron is very strongly affected by the presence of sulfur which acts as a surfactant in this system varying between 1.9 and 0.4 N/m at 10 mass percent Sulfur (Lee & Morita (2002), This last value is inferred to be the maximum value for Sulfur inferred to be present in the liquid outer core. Venting of Sulfur from the liquid core manifests itself on the Earth surface by the 105 to 106 ton of sulfur vented into the atmosphere annually (Wedepohl, 1984). Inspection of surface Sulfur emission indicates that venting is non-homogeneously distributed over the Earth's surface. The implication of such large variation in surface tension in the liquid outer core are that at locally low Sulfur concentration, the liquid outer core does not wet the predominantly MgSiO3 matrix with which it is in contact. However at a local high in Sulfur, the liquid outer core wets this matrix which in the fluid state has a surface tension of 0.4 N/m (Bansal & Doremus, 1986), couples with it, and causes it to sink. This differential and diapiric movement is transmitted through the essentially brittle mantle (1024 Pa.s, Lambeck & Johnson, 1998; the maximum value for ice being about 1030 Pa.s at 0 K, in all likely hood representing an upper bound of viscosity for all materials) and manifests itself on the surface by the roughly 20 km differentiation, about 0.1 % of the total mantle thickness, between topographical heights and lows with concomitant lateral movement in the crust and upper mantle resulting in thin skin tectonics. The brittle nature of the medium though which this movement is transmitted suggests that the extremes in topography of the D" layer are similar in range to those observed on the Earth's surface and are mimicked by lows under the oceans and highs under the altiplanos. Careful and area selective S wave core mantle ellipsometry might be able to discern these core-mantle topographic variations. As such this process demonstrates the validity of the Gaia hypothesis enunciated by Baas Becking(1931) that no ecological niche on our planet is closed off from other niches "nothing in the world is single".

de Jong, B. H.

2007-12-01

339

Prototype V-Groove Radiator Heat Shield  

NASA Technical Reports Server (NTRS)

Report describes design, fabrication, and testing of heat radiator equipped with multi-V-groove radiator heat shield. Device compact, efficient structure which removes heat from infrared detectors, gamma-ray detectors, and similar instruments aboard Mars Observer spacecraft and radiates heat into outer space. Designed to maintain detector for gamma-ray spectrometer at temperature of 80 K in cold vacuum under heat load of 80 mW. Prototype made of aluminum, though production shields made of aluminized sheets of polyethylene terephthalate.

Petrick, S. Walter; Bard, Steven

1990-01-01

340

Tectonic evolution of the Western Australian Shield  

NASA Technical Reports Server (NTRS)

Geological and geochronological studies in the Western Australian Shield were updated. This terrane bears many similarities to the Indian Shield since they were neighboring parts of Gondwanaland. Western Australia consists of two cratons (Pilbara and Yilgarn) and four orogenic belts (Capricorn, Pingarra, Albany-Fraser, and Patterson), as well as some relatively young (1.6 to 0.75 Ga) sedimentary rocks. The two cratonic blocks are both older than about 2.5 Ga, and the orogenic belts range in age from 2.0 to 0.65 Ga.

Myers, John S.

1988-01-01

341

WASTE HANDLING BUILDING SHIELD WALL ANALYSIS  

SciTech Connect

The scope of this analysis is to estimate the shielding wall, ceiling or equivalent door thicknesses that will be required in the Waste Handling Building to maintain the radiation doses to personnel within acceptable limits. The shielding thickness calculated is the minimum required to meet administrative limits, and not necessarily what will be recommended for the final design. The preliminary evaluations will identify the areas which have the greatest impact on mechanical and facility design concepts. The objective is to provide the design teams with the necessary information to assure an efficient and effective design.

D. Padula

2000-01-13

342

Computer subroutines for estimation of human exposure to radiation in low Earth orbit  

NASA Technical Reports Server (NTRS)

Computer subroutines to calculate human exposure to trapped radiations in low Earth orbit (LEO) on the basis of a simple approximation of the human geometry by spherical shell shields of varying thickness are presented and detailed. The subroutines calculate the dose to critical body organs and the fraction of exposure limit reached as a function of altitude of orbit, degree of inclination, shield thickness, and days in mission. Exposure rates are compared with current exposure limits.

Cucinotta, F. A.; Wilson, J. W.

1985-01-01

343

75 FR 57519 - Weather Shield Manufacturing, Medford, WI; Notice of Negative Determination Regarding Application...  

Federal Register 2010, 2011, 2012, 2013

...673] Weather Shield Manufacturing, Medford, WI; Notice...workers of Weather Shield Manufacturing, Inc., Medford, Wisconsin (subject firm). The negative determination...various Weather Shield Manufacturing, Inc....

2010-09-21

344

Solar wind induced magnetic field around the unmagnetized Earth  

NASA Astrophysics Data System (ADS)

The Earth is a planet with a dipolar magnetic field which is agitated by a magnetized plasma wind streaming from the Sun. The magnetic field shields the Earth's surface from penetrating high energy solar wind particles, as well as interstellar cosmic rays. The magnetic dipole has reversed sign some hundreds of times over the last 400 million years. These polarity reversals correspond to drastic breakdowns of the dynamo action. The question arises what the consequences for the Earth's atmosphere, climate, and, in particular, biosphere are. It is shown by kinematic estimates and three-dimensional plasma-neutral gas simulations that the solar wind can induce very fast a magnetic field in the previously completely unmagnetized Earth's ionosphere that is strong enough to protect Earth from cosmic radiations comparable to the case of an intact magnetic dynamo.

Birk, G. T.; Lesch, H.; Konz, C.

2004-06-01

345

Earth-Sun Geometry - Earth Revolution Animation  

NSDL National Science Digital Library

The representation is an animation of the Earth revolving around the sun. The Earth is shown as a solid green sphere with the equator and arctic circle marked with black lines and the dark side of the Earth shaded. The Earth's axis is shown with a red line. As the Earth revolves around the sun, the axis is shown to always be pointing in the same direction. The positions of Earth at the winter solstice, vernal equinox, summer solstice, and autumnal equinox are labeled.

Pidwirny, Michael; Okanagan, Scott J.

346

Optimization of Martian regolith and ultra-high molecular weight polyethylene composites for radiation shielding and habitat structures  

NASA Astrophysics Data System (ADS)

In preparation for long duration missions to the moon, Mars or, even near earth asteroids, one challenge, amongst many others, that the space program faces is shielding against space radiation. It is difficult to effectively shield all sources of space radiation because of the broad range of types and high energies found in space, so the most important goal is to minimize the damaging effects that may occur to humans and electronics during long duration space flight. For a long duration planetary habitat, a shielding option is to use in situ resources such as the native regolith. A possible way to utilize regolith on a planet is to combine it with a binder to form a structural material that also exhibits desirable shielding properties. In our studies, we explore Martian regolith and ultra-high molecular weight polyethylene (UHMWPE) composites. We selected UHMWPE as the binder in our composites due to its high hydrogen content; a desirable characteristic for shielding materials in a space environment. Our initial work has focused on the process of developing the right ratio of simulated Martian regolith and UHMWPE to yield the best results in material endurance and strength, while retaining good shielding characteristics. Another factor in our optimization process is to determine the composite ratio that minimizes the amount of ex situ UHMWPE while retaining desirable structural and shielding properties. This consideration seeks to minimize mission weight and costs. Mechanical properties such as tensile strength of the Martian regolith/UHMWPE composite as a function of its grain size, processing parameters, and different temperature variations used are discussed. The radiation shielding effectiveness of loose mixtures of Martian regolith/ UHMWPE is evaluated using a 200 MeV proton beam and a tissue equivalent proportional counter. Preliminary results show that composites with an 80/20 ratio percent weight of regolith to UHMWPE can be fabricated with potentially useful structural strength. I n addition, Martian regolith, while not as efficient as polyethylene at reducing proton energy as a function of shield thickness, compares well with polyethylene at shielding the 200 MeV protons. These preliminary results indicate that native Martian regolith has promising properties as a habitat material for future human missions. Future work studying the shielding effectiveness and radiation tolerance will also be discussed.

Wilkins, Richard; Gersey, Brad; Baburaj, Abhijit; Barnett, Milan; Zhou, Xianren

2012-07-01

347

Measurement of 56Fe activity produced in inelastic scattering of neutrons created by cosmic muons in an iron shield.  

PubMed

We report on the study of the intensities of several gamma lines emitted after the inelastic scattering of neutrons in (56)Fe. Neutrons were produced via nuclear processes induced by cosmic muons in the 20tons massive iron cube placed at the Earth's surface and used as a passive shield for the HPGe detector. Relative intensities of detected gamma lines are compared with the results collected in the same iron shield by the use of the (252)Cf neutrons. Assessment against the published data from neutron scattering experiments at energies up to 14MeV is also provided. It allowed us to infer the qualitative information about the average energy of muon-created neutrons in the iron shield. PMID:21890368

Krmar, M; Jovan?evi?, N; Nikoli?, D

2012-01-01

348

DNA fragmentation induced by fe ions in human cells: shielding influence on spatially correlated damage  

SciTech Connect

Outside the magnetic field of the Earth, high energy heavy ions constitute a relevant part of the biologically significant dose to astronauts during the very long travels through space. The typical pattern of energy deposition in the matter by heavy ions on the microscopic scale is believed to produce spatially correlated damage in the DNA which is critical for radiobiological effects. We have investigated the influence of a lucite shielding on the initial production of very small DNA fragments in human fibroblasts irradiated with 1 GeV/u iron (Fe) ions. We also used small gamma, Greek-rays as reference radiation. Our results show: (1) a lower effect per incident ion when the shielding is used; (2) an higher DNA Double Strand Breaks (DSB) induction by Fe ions than by small gamma, Greek-rays in the size range 123 kbp; (3) a non-random DNA DSB induction by Fe ions.

Antonelli, F.; Belli, M.; Campa, A.; Chatterjee, A.; Dini, V.; Esposito, G.; Rydberg, B.; Simone, G.; Tabocchini, M.A.

2003-11-19

349

DNA fragmentation induced by Fe ions in human cells: shielding influence on spatially correlated damage  

NASA Technical Reports Server (NTRS)

Outside the magnetic field of the Earth, high energy heavy ions constitute a relevant part of the biologically significant dose to astronauts during the very long travels through space. The typical pattern of energy deposition in the matter by heavy ions on the microscopic scale is believed to produce spatially correlated damage in the DNA which is critical for radiobiological effects. We have investigated the influence of a lucite shielding on the initial production of very small DNA fragments in human fibroblasts irradiated with 1 GeV/u iron (Fe) ions. We also used gamma rays as reference radiation. Our results show: (1) a lower effect per incident ion when the shielding is used; (2) an higher DNA Double Strand Breaks (DSB) induction by Fe ions than by gamma rays in the size range 1-23 kbp; (3) a non-random DNA DSB induction by Fe ions. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

Antonelli, F.; Belli, M.; Campa, A.; Chatterjee, A.; Dini, V.; Esposito, G.; Rydberg, B.; Simone, G.; Tabocchini, M. A.

2004-01-01

350

Reflectivity level of RF shielded anechoic chamber  

Microsoft Academic Search

The reflectivity level of an RF shielded rectangular chamber with a non-uniform absorber lining has been investigated using the geometrical optics approach. The excitation antennas considered are the Hertzian dipole, a halfwave dipole and a pyramidal horn. A simple model is employed for the reflectivity of the absorber lining for normal incidence

S. V. K. Shastry; S. K. Nagesh; D. Binu

1995-01-01

351

Operation Desert Shield and Desert Storm.  

National Technical Information Service (NTIS)

So what did you do in the War, Daddy. As a Battalion Commander of an AH-64 Attack Helicopter Battalion during Operations Desert Shield and Desert Storm, my experiences were many, my memories everlasting. Rather than enumerate a chronology of events, I wil...

A. R. Jones

1992-01-01

352

Shielding Integral Benchmark Archive and Database (SINBAD)  

Microsoft Academic Search

The Shielding Integral Benchmark Archive and Database (SINBAD) collection of benchmarks was initiated in the early 1990s. SINBAD is an international collaboration between the Organization for Economic Cooperation and Development's Nuclear Energy Agency Data Bank (OECD\\/NEADB) and the Radiation Safety Information Computational Center (RSICC) at Oak Ridge National Laboratory (ORNL). SINBAD is a major attempt to compile experiments and corresponding

Bernadette Lugue Kirk; Robert E Grove; I. Kodeli; Enrico Sartori; J. Gulliford

2011-01-01

353

Shielding and Density of States in Alloys.  

National Technical Information Service (NTIS)

A relationship between the shielding of the ion-core potentials and the electron density of states rho(E,c) in disordered alloys of concentration c is shown. When one type of atom in a binary disordered alloy is replaced by another type of atom, there wil...

E. A. Stern

1971-01-01

354

President Clinton Defers Missile Shield Decision  

NSDL National Science Digital Library

President Clinton will announce in a speech at Georgetown University today that he will not begin the initial steps to deploy a national missile defense shield, leaving the final decision to his successor. The decision to not begin construction of a radar site in Alaska, designed to track incoming missiles, was apparently the product of several factors. These include the failure of recent tests, strong opposition from Russia and some US allies, and fears that any decision would inevitably become politicized with the election nearing. Vice-President Al Gore has expressed conditional support for a missile shield, while George W. Bush has called for an even more extensive system. The President made his decision after receiving competing advice on the missile shield. William S. Cohen, the defense secretary, had recommended Mr. Clinton begin, while Samuel R. Berger, the President's national security advisor, and others recommended against construction at this point. Work on the project will continue nonetheless, including additional tests of the "kill vehicle" and a new booster rocket. The next President will decide not only whether to build the radar station and other elements of a missile shield infrastructure, but also whether to field the system and break the 1972 Antiballistic Missile Treaty.

De Nie, Michael W.

355

Shielding Design for PWR in France.  

National Technical Information Service (NTIS)

Shielding calculation scheme used in France for PWR is presented here for 900 MWe and 1300 MWe plants built by EDF the French utility giving electricity. Neutron dose rate at areas accessible by personnel during the reactor operation is calculated and com...

G. Champion Charransol A. Le Dieu de Ville J. C. Nimal T. Vergnaud

1983-01-01

356

Corrosion protection and EMP/EMI shielding  

SciTech Connect

The high-voltage electrical surges which are released from nuclear explosions are called electromagnetic pulses (EMP). Because they can have adverse effects on aircraft and other weapon system electrical circuits, the DOD has evaluated a variety of approaches to providing protection against EMP and electromagnetic interference (EMI). Researchers are now working to develop conductive sealants which can provide corrosion protection while meeting the EMP/EMI shielding requirements of military aircraft and missiles. Test results indicate that shielding effectiveness increases as dc resistance decreases, and shielding effectiveness does not appear to be a strong function of frequency above the 500-1000 MHz test frequency range. The correlations of resistance and shielding effectiveness necessitates that a low resistance exists across a joint or bond. Thus the researchers recommended that the conductive sealants successfully tested be used on existing and future aircraft and missiles where sealants can be liquid-applied. In addition to the test findings and their applications to the operational arena, a primary outcome of these tests is a set of recommended changes to selected military standards, specifications, and handbooks. These recommendations will be used as inputs to any proceedings conducted for the purpose of modifying those documents.

Brahney, J.H.

1990-06-01

357

Passive magnetic shielding in static gradient fields  

NASA Astrophysics Data System (ADS)

The effect of passive magnetic shielding on dc magnetic field gradients imposed by both external and internal sources is studied for two idealized shield models: concentric spherical and infinitely-long cylindrical shells of linear material. It is found that higher-order multipoles of an externally applied magnetic field are always shielded progressively better for either geometry by a factor related to the order of the multipole. In regard to the design of internal coil systems, we determine reaction factors for the general multipole field and provide examples of how one can take advantage of the coupling of the coils to the innermost shell to optimize the uniformity of the field. Furthermore, we provide formulae relevant to active magnetic compensation systems which attempt to stabilize the interior fields by sensing and cancelling the exterior fields close to the outermost shell. Overall this work provides a comprehensive framework that is useful for the analysis and optimization of dc magnetic shields, serving as a theoretical and conceptual design guide as well as a starting point and benchmark for finite-element analysis.

Bidinosti, C. P.; Martin, J. W.

2014-04-01

358

Subsurface Shielding Source Term Specification Calculation  

SciTech Connect

The purpose of this calculation is to establish appropriate and defensible waste-package radiation source terms for use in repository subsurface shielding design. This calculation supports the shielding design for the waste emplacement and retrieval system, and subsurface facility system. The objective is to identify the limiting waste package and specify its associated source terms including source strengths and energy spectra. Consistent with the Technical Work Plan for Subsurface Design Section FY 01 Work Activities (CRWMS M&O 2001, p. 15), the scope of work includes the following: (1) Review source terms generated by the Waste Package Department (WPD) for various waste forms and waste package types, and compile them for shielding-specific applications. (2) Determine acceptable waste package specific source terms for use in subsurface shielding design, using a reasonable and defensible methodology that is not unduly conservative. This calculation is associated with the engineering and design activity for the waste emplacement and retrieval system, and subsurface facility system. The technical work plan for this calculation is provided in CRWMS M&O 2001. Development and performance of this calculation conforms to the procedure, AP-3.12Q, Calculations.

S.Su

2001-04-12

359

New shielding protective equipment for live working  

Microsoft Academic Search

The new protective equipment forms a FARADAY cage, thus protecting the worker from unacceptably strong electrical fields as well as from being invaded by dangerous electric currents. The protective shielding clothing described is a personal protective equipment of the highest category. Therefore, it must be certified by an acknowledged examining and certifying authority. An application with regard to the attestation

Claudia Herzberg; Hartmut Rödel; Eberhard Engelmann

2001-01-01

360

Radiation Shielding Analysis for Deep Space Missions  

Microsoft Academic Search

An environment for radiation shielding analysis for manned deep space mission scenarios has been developed. The analysis is performed by dividing a mission scenario into three possible different phases, namely the interplanetary cruise phase, the final planetary approach and orbit insertion, and the surface phase. In the first phase only Galactic Cosmic Rays and Solar Events particles are used, in

Giovanni de Angelis; Martha S. Clowdsley; John E. Nealy; Robert C. Singleterry; Ram K. Tripathi; John W. Wilson

2003-01-01

361

SCALE radiation shielding V and V package  

SciTech Connect

Verification and validation (V and V) are essential elements of software quality assurance (QA) for computer codes that are used for scientific calculations. The sponsors of the SCALE code system have required a QA plan and a V and V plan. For purposes of validating and verifying the SCALE shielding codes, a set of problems has been assembled and tested.

Emmett, M.B.; Bowman, S.M.; Broadhead, B.L.

1997-12-01

362

Shielded serpentine traveling wave tube deflection structure.  

National Technical Information Service (NTIS)

This invention is comprised of a shielded serpentine slow wave deflection structure having a serpentine signal conductor within a channel groove. The channel groove is formed by a serpentine channel in a trough plate and a ground plane. The serpentine sig...

C. L. Hudson J. Spector

1992-01-01

363

Optimization For Whipple Shields Under Normal Impact  

Microsoft Academic Search

An engineering structural optimization methodology of Whipple Shields is developed designed to defeat hypervelocity impacts of meteoroids and space debris. The major unique of the optimization model presented in the paper is that Hypervelocity Impact Physical Model based on One-Dimension Impact Theory is incorporated into the previous optimization model. A space debris environment model is incorporated into an overall optimization

Song Lin; Yuzhu Zhang; Renwei Xia

2002-01-01

364

Hermetic Sealing and EMI Shielding Gasket.  

National Technical Information Service (NTIS)

A composition is disclosed for forming an EMI shielding gasket for installation against a metal object, such as an aluminum frame member of an aircraft, wherein the composition is comprised of a mixture of a prepolymer composition of a flexible polyuretha...

R. Panayappan J. C. Cooper

1992-01-01

365

Nuclear physics issues in radiation shielding assessment  

Microsoft Academic Search

Protecting the astronauts from the adverse health effects of galactic cosmic radiation is a complicated issue because of uncertainty in the physics of interactions with the nuclei of shielding materials and astronaut tissues. Semi-classical Monte Carlo methods have shown reasonable success and can include quantum fluctuations but lack phase information for evaluation of diffractive and interference effects in the asymptotic

John Wilson; Ram Tripathi; Francis Cucinotta; John Norbury

2000-01-01

366

The Tower Shielding Facility: Its glorious past  

SciTech Connect

The Tower Shielding Facility (TSF) is the only reactor facility in the US that was designed and built for radiation-shielding studies in which both the reactor source and shield samples could be raised into the air to allow measurements to be made without interference from ground scattering or other spurious effects. The TSF proved its usefulness as many different programs were successfully completed. It became active in work for the Defense Atomic Support Agency (DASA) Space Nuclear Auxiliary Power, Defense Nuclear Agency, Liquid Metal Fast Breeder Reactor Program, the Gas-Cooled and High-Temperature Gas-Cooled Reactor programs, and the Japanese-American Shielding Program of Experimental Research, just to mention a few of the more extensive ones. The history of the TSF as presented in this report describes the various experiments that were performed using the different reactors. The experiments are categorized as to the programs which they supported and placed in corresponding chapters. The experiments are described in modest detail, along with their purpose when appropriate. Discussion of the results is minimal, but references are given to more extensive topical reports.

Muckenthaler, F.J.

1997-05-07

367

Shielding analysis of the long length contaminated equipment transportation package  

SciTech Connect

A shielding analysis of a potential long length contaminated equipment transportation package was completed. The analysis was performed to support the design of the transportation package and external shielding.

Nelson, J.V., Westinghouse Hanford

1996-05-10

368

6. View shows Shield 11, looking west. Typical concrete debris ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

6. View shows Shield 11, looking west. Typical concrete debris shield. - Lake Hodges Flume, Along San Dieguito River between Lake Hodges & San Dieguito Reservoir, Rancho Santa Fe, San Diego County, CA

369

Internal Shield Ground Adapter for Kickpipe/Stuffing Tubes.  

National Technical Information Service (NTIS)

The present invention generally relates to electrical grounding equipment and more particularly to a shield ground adapter (SGA) designed to shunt high level electromagnetic (EM) energy from cable shields to a metallic boundary such as kickpipe/stuffing t...

D. S. Dixon

1988-01-01

370

Neutron shielding material based on colemanite and epoxy resin.  

PubMed

In recent years, there has been a need for compact shielding design such as self-shielding of a PET cyclotron or upgradation of radiation machinery in existing facilities. In these cases, high performance shielding materials are needed. Concrete or polyethylene have been used for a neutron shield. However, for compact shielding, they fall short in terms of performance or durability. Therefore, a new type of neutron shielding material based on epoxy resin and colemanite has been developed. Slab attenuation experiments up to 40 cm for the new shielding material were carried out using a 252Cf neutron source. Measurement was carried out using a REM-counter, and compared with calculation. The results show that the shielding performance is better than concrete and polyethylene mixed with 10 wt% boron oxide. From the result, we confirmed that the performance of the new material is suitable for practical use. PMID:16381724

Okuno, Koichi

2005-01-01

371

Light shield and cooling apparatus. [high intensity ultraviolet lamp  

NASA Technical Reports Server (NTRS)

A light shield and cooling apparatus was developed for a high intensity ultraviolet lamp including water and high pressure air for cooling and additional apparatus for shielding the light and suppressing the high pressure air noise.

Meador, T. G., Jr. (inventor)

1974-01-01

372

Early test facilities and analytic methods for radiation shielding: Proceedings  

SciTech Connect

This report represents a compilation of eight papers presented at the 1992 American Nuclear Society/European Nuclear Society International Meeting. The meeting is of special significance since it commemorates the fiftieth anniversary of the first controlled nuclear chain reaction. The papers contained in this report were presented in a special session organized by the Radiation Protection and Shielding Division in keeping with the historical theme of the meeting. The paper titles are good indicators of their content and are: (1) The origin of radiation shielding research: The Oak Ridge experience, (2) Shielding research at the hanford site, (3) Aircraft shielding experiments at General Dynamics Fort Worth, 1950-1962, (4) Where have the neutrons gone , a history of the tower shielding facility, (5) History and evolution of buildup factors, (6) Early shielding research at Bettis atomic power laboratory, (7) UK reactor shielding: then and now, (8) A very personal view of the development of radiation shielding theory.

Ingersoll, D.T. (comp.) (Oak Ridge National Lab., TN (United States)); Ingersoll, J.K. (comp.) (Tec-Com, Knoxville, TN (United States))

1992-11-01

373

Active Shielding in Measurements of DC Near Biomagnetic Fields.  

National Technical Information Service (NTIS)

Measurements of DC near biomagnetic fields are disturbed by low frequency noise, that are not reduced sufficiently by most of the magnetically shielded rooms or gradiometers. An effective SQUID based active shielding system has been developed and installe...

H. Nowak J. Haueisen M. Ziolkowski F. Resmer J. Schueler

2001-01-01

374

Opportunity's Heat Shield in Color, Sol 335  

NASA Technical Reports Server (NTRS)

This image from the panoramic camera on NASA's Mars Exploration Rover Opportunity features the remains of the heat shield that protected the rover from temperatures of up to 2,000 degrees Fahrenheit as it made its way through the martian atmosphere. This two-frame mosaic was taken on the rover's 335th martian day, or sol, (Jan. 2, 2004).

The view is of the main heat shield debris seen from approximately 10 meters (about 33 feet) away from it. Many rover-team engineers were taken aback when they realized the heat shield had inverted, or turned itself inside out. The height of the pictured debris is about 1.3 meters (about 4.3 feet). The original diameter was 2.65 meters (8.7 feet), though it has obviously been deformed. The Sun reflecting off of the aluminum structure accounts for the vertical blurs in the picture.

The fact that the heat shield is now inside out makes it more challenging to evaluate the state of the thermal protection system that is now on the inside. In coming sols, Opportunity will investigate the debris with its microscopic imager.

Engineers who designed and built the heat shield are thrilled to see the hardware on the surface of Mars. This provides a unique opportunity to look at how the thermal protection system material survived the actual Mars entry. Team members hope this information will allow them to compare their predictions to what really happened.

The image is an approximately true-color rendering generated using the panoramic camera's 600, 530 and 480 nanometer filters.

2005-01-01

375

Earth Science Lessons  

NSDL National Science Digital Library

This collection of Earth Science lessons, tests, and activities for middle school students is an accompaniment to the Volcano World website. Topics covered include plate tectonics, Pangea, plate movement, Earth layers, earthquakes, volcanoes, rocks and minerals, and prehistoric Earth.

Johnson, Scott

376

Earth and Space  

NSDL National Science Digital Library

In earth and space science, students study the origin, structure, and physical phenomena of the earth and the universe. Earth and space science studies include concepts in geology, meteorology, oceanography, and astronomy.

K-12 Outreach,

377

Electromagnetic interference shielding mechanisms of CNT\\/polymer composites  

Microsoft Academic Search

The electromagnetic interference (EMI) shielding mechanisms of multi-walled carbon nanotube (MWCNT)\\/polymer composites were analyzed experimentally and theoretically. For the experimental analysis, EMI shielding effectiveness (SE) of MWCNT\\/polypropylene (PP) composite plates made in three different thicknesses and at four different concentrations were studied. A model based on the shielding of electromagnetic plane wave was used to theoretically study the EMI shielding

Mohammed H. Al-Saleh; Uttandaraman Sundararaj

2009-01-01

378

Effective shielding to measure beam current from an ion sourcea)  

NASA Astrophysics Data System (ADS)

To avoid saturation, beam current transformers must be shielded from solenoid, quad, and RFQ high stray fields. Good understanding of field distribution, shielding materials, and techniques is required. Space availability imposes compact shields along the beam pipe. This paper describes compact effective concatenated magnetic shields for IFMIF-EVEDA LIPAc LEBT and MEBT and for FAIR Proton Linac injector. They protect the ACCT Current Transformers beyond 37 mT radial external fields. Measurements made at Saclay on the SILHI source are presented.

Bayle, H.; Delferrière, O.; Gobin, R.; Harrault, F.; Marroncle, J.; Senée, F.; Simon, C.; Tuske, O.

2014-02-01

379

Development of shielding design code for synchrotron radiation beam line  

NASA Astrophysics Data System (ADS)

For the purpose of application to shielding design calculation for beam lines of SPring-8, a 8 GeV class synchrotron radiation facility of Japan, a new shielding code, STAC-8, has been developed on the basis of a shielding design code, PHOTON. Preliminary shielding calculation for the pilot beam lines of SPring-8 is performed with STAC-8. Validity of the code is verified by comparing its calculation with those using a Monte Carlo code EGS4 and PHOTON.

Asano, Yoshihiro; Sasamoto, Nobuo

1994-07-01

380

500 kV shield wires; Sectionalize or ground everywhere  

Microsoft Academic Search

The primary purpose of shield wires on transmission lines in lightning protection. Development of fiber-optic shied wires added communications capabilities. Schemes for adapting fiber-optic shield wires to sectionalized shield wire designs remain untested. It is a present policy to segment and insulate 500 kV shield wires. Computer modeling and supportive field measurements have revealed a characteristic distribution of grounded tower

Tuominen

1992-01-01

381

Designing dual-plate meteoroid shields: A new analysis  

NASA Technical Reports Server (NTRS)

Physics governing ultrahigh velocity impacts onto dual-plate meteor armor is discussed. Meteoroid shield design methodologies are considered: failure mechanisms, qualitative features of effective meteoroid shield designs, evaluating/processing meteoroid threat models, and quantitative techniques for optimizing effective meteoroid shield designs. Related investigations are included: use of Kevlar cloth/epoxy panels in meteoroid shields for the Halley's Comet intercept vehicle, mirror exposure dynamics, and evaluation of ion fields produced around the Halley Intercept Mission vehicle by meteoroid impacts.

Swift, H. F.; Bamford, R.; Chen, R.

1982-01-01

382

Exploring Magnetism on Earth  

NSDL National Science Digital Library

This teacher's guide contains four lessons that provide a way for teachers to introduce students to and elaborate on Earth's changing magnetic field. It covers learning to navigate using Earth's magnetic field and compass, Earth's magnetic pole and its motion across Earth's surface, magnetic reversals on Earth, and Earth's currently declining magnetic field. These lessons have been taught primarily in math, geology, and astronomy classes.

2005-01-01

383

ALTEA-SHIELD: a survey of the radiation in the ISS (USLab)  

NASA Astrophysics Data System (ADS)

In general, radiation exposure represents one of the greatest risks to humans traveling on exploration missions beyond low Earth orbit (LEO). The ALTEA detector (ALTEA-Shield experiment) is used to measure the radiation environment in different places of the ISS-USLab. ALTEA-Shield is part of the ALTEA program, a multidisciplinary research project which aims at obtaining a better understanding of the radiation environment on board the International Space Station, and also at studying the interaction between cosmic rays and the astronauts visual system. The ALTEA-Shield/Survey experiment, financed by the Italian Space Agency (ASI) and sponsored by ESA, uses the six particle detectors (SDUs, Silicon Detector Units) of ALTEA arranged on a 3D isotropic support. It is capable to measure cosmic ray particles coming from three different directions, being able to give an overview on the particle fluxes (in a detectable energy range between 3 and 900 keV/um) in different locations of the USLab. The ALTEA-Shield/Survey experiment started on September 2010 and it was placed in four locations of the USLab, resulting in a total observation time of more than 290 days. We present here the particle fluxes in the four positions, together with previous measurements acquired under the ALTEA-DOSI experimental sessions in 2006-2009; ALTEA is able to discriminate ion species (charge Z) from Z>4 and to measure the trajectory of each particle, so to be able to reconstruct the radiation flux in the three direction XYZ. The differences in the flux measured along these directions (along the ISS main body and two transverse directions) are mostly due to the different amount and quality of shielding materials passed by the incoming nuclei.

Zaconte, Veronica; Di Fino, Luca; Larosa, Marianna; Picozza, Piergiorgio; Narici, Livio; Casolino, Marco

2012-07-01

384

Magnetic field concentration: comparison between several shapes of superconducting shields  

Microsoft Academic Search

This paper deals with a system of flux density concentration using superconducting shields. The development of single grain high, temperature superconductors allows the conception of large sized magnetic shields. These shields force the flux density to be concentrated by modifying its spatial distribution. The authors' system consists of two low field solenoids, which have the same arrangement as Helmoltz coils.

P. Masson; D. Netter; J. Leveque; A. Rezzoug

2001-01-01

385

Dose buildup factor formula for double-layered shields  

Microsoft Academic Search

In radiation shielding, health physics, and radioactive waste management, it is very important to know buildup factors for various materials and their combinations used as multilayer shields. In this work, a general formula that computes buildup factors for double-layer shields was developed on the basis of Monte Carlo photon transport using the MCNP code. Formulas for buildup factors for double-layer

M. Guvendik; N. Tsoulfanidis

1999-01-01

386

Shrinkable sleeve eliminates shielding gap in RF cable  

NASA Technical Reports Server (NTRS)

RF shielding gap between an RF cable and a multipin connector is eliminated by a sleeve assembly installed between the connector and the terminated portion of the shielding. The assembly is enclosed in a heat-shrinkable plastic sleeve which completes the continuous RF shield.

1965-01-01

387

Shielding design for the proposed Advanced Photon Source at Argonne  

Microsoft Academic Search

Bulk shielding was designed for the proposed Argonne Advanced Photon Source. The shielding is for two linacs, the positron converter, booster synchrotron, and the storage ring. Shielding design limits exposure to 20 mrem\\/wk for occupational and 25 mrem\\/y for an individual member of the public from the radiation products, which include high energy neutrons (HEN), giant resonance neutrons (GRN), and

H. J. Moe; V. R. Veluri

1987-01-01

388

Analytical formulation for the shielding effectiveness of enclosures with apertures  

Microsoft Academic Search

An analytical formulation has been developed for the shielding effectiveness of a rectangular enclosure with an aperture. Both the magnetic and electric shielding may be calculated as a function of frequency, enclosure dimensions, aperture dimensions and position within the enclosure. Theoretical values of shielding effectiveness are in good agreement with measurements. The theory has been extended to account for circular

Martin Paul Robinson; Trevor M. Benson; Christos Christopoulos; John F. Dawson; M. D. Ganley; A. C. Marvin; S. J. Porter; David W. P. Thomas

1998-01-01

389

Application of Modal Analysis to Braided-Shield Cables  

Microsoft Academic Search

Transmission-line equations are derived for a braidedshield cable by modal analysis. The parameters of the braided shield appear in the coefficients as well as in the source terms of the equations. The source terms also depend on the currents and charges on the outer surface of the shield with all the shield's apertures shortcircuited.

K. S. H. Lee; CARL E. BAUM

1975-01-01

390

21 CFR 886.4750 - Ophthalmic eye shield.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Ophthalmic eye shield. 886.4750 Section 886.4750...Surgical Devices § 886.4750 Ophthalmic eye shield. (a) Identification. An ophthalmic eye shield is a device that consists of a...

2013-04-01

391

Three dimensional hypervelocity impact simulation for orbital debris shield design  

Microsoft Academic Search

This paper assesses a Whipple shield impact simulation method which is both accurate and computationally efficient. The paper documents the simulation methodology and results of Whipple shield simulations at an oblique impact angle of 30°. These results are compared with HVI experiments to demonstrate the accuracy of the simulation technique. In addition, simulations of Whipple shields in the velocity regime

Justin H. Kerr; Eric P. Fahrenthold

1997-01-01

392

Ballistic limit evaluation of advanced shielding using numerical simulations  

Microsoft Academic Search

The advanced shielding concept employed for the Columbus module of the International Space Station consists of an aluminum bumper and an intermediate shield of Nextel and Kevlar-epoxy. Until recently, the lack of adequate material models for the Nextel cloth and Kevlar-epoxy has precluded the practical usage of hydrocodes in evaluating the response of these shields to hypervelocity impact threats. Recently

Colin J. Hayhurst; Iain H. G. Livingstone; Richard A. Clegg; Roberto Destefanis; Moreno Faraud

2001-01-01

393

Large Scale Spheromak for Magnetic Shielding of Spacecraft  

Microsoft Academic Search

Exposure to the energetic particles associated with solar energetic particle events and galactic cosmic rays are known radiation hazards for human exploration. Material shielding would add substantial mass to the spacecraft and provide shielding over very limited areas. The concept that will be explored here is the prospect of providing the shielding by making use of ambient low density plasma

John Slough

2006-01-01

394

Shielding Analyses for Design of the Upgraded JRR-3 Research Reactor, 2. Shielding of Neutron Beam Holes.  

National Technical Information Service (NTIS)

Shielding analyses of neutron beam holes have been presented for the shield design of the upgraded JRR-3 research reactor. Description is given about the calculational procedures and results for the standard beam hole, the beam hole for neutron radiograph...

T. Ise T. Maruo Y. Miyasaka M. Isshiki T. Kumai

1985-01-01

395

How stable are the 'stable ancient shields'?  

NASA Astrophysics Data System (ADS)

"Archean cratons are relatively flat, stable regions of the crust that have remained undeformed since the Precambrian, forming the ancient cores of the continents" (King, EPSL, 2005). While this type of statement is supported by a wealth of constraints in the case of episodes of thoroughgoing ductile deformation affecting shield regions of Archean and also Peleoproterozoic age, a growing amount of research indicates that shields are not nearly as structurally stable within the broad field of environmental conditions leading to brittle deformation. In fact, old crystalline basements usually present compelling evidence of long brittle deformation histories, often very complex and challenging to unfold. Recent structural and geochronological studies point to a significant mechanical instability of the shield areas, wherein large volumes of 'stable' rocks actually can become saturated with fractures and brittle faults soon after regional cooling exhumes them to below c. 300-350° C. How cold, rigid and therefore strong shields respond to applied stresses remains, however, still poorly investigated and understood. This in turn precludes a better definition of the shallow rheological properties of large, old crystalline blocks. In particular, we do not yet have good constraints on the mechanisms of mechanical reactivation that control the partial (if not total) accommodation of new deformational episodes by preexisting structures, which remains a key to untangle brittle histories lasting several hundred Myr. In our analysis, we use the Svecofennian Shield (SS) as an example of a supposedly 'stable' region with Archean nucleii and Paleoproterozoic cratonic areas to show how it is possible to unravel the details of brittle histories spanning more than 1.5 Gyr. New structural and geochronological results from Finland are integrated with a review of existing data from Sweden to explore how the effects of far-field stresses are partitioned within a shield, which was growing progressively saturated with fractures as time passed from its initial consolidation. The comparison of time-constrained paleostress data derived from three different locations of the shield shows a remarkably similar stress evolution through time, despite the different geological frameworks of the investigated areas. This suggests that the southern SS has behaved as a coherent rigid crustal block since the Late Mesoproterozoic. By that time, the SS had already reached structural maturity with respect to the saturation of brittle structural features. Therefore, structural reactivation rather than generation of new faults and fractures is the key mechanism that has controlled the mechanical evolution of the shield and that will steer its future evolution within the brittle regime. Comparable brittle structural histories within parts of the shield that are far apart also imply that far-field stresses can propagate over large distances and can lead to similar deformational histories, with the local geological conditions only playing a second-order role on the final brittle strain pattern recorded by the rock.

Viola, Giulio; Mattila, Jussi

2014-05-01

396

New Data for Early Earth Atmospheric Modelling  

NASA Astrophysics Data System (ADS)

The timing of the oxygenation of the Earth’s atmosphere is a central issue in understanding the Earth’s paleoclimate. The discovery of mass-independent fractionation (MIF) of sulphur isotopes deposited within Archean and Paleoproterozoic rock samples (> 2.4 Gyrs) and the transition to mass-dependent fractionation found in younger samples, could provide a marker for the rise in oxygen concentrations in the Earth’s atmosphere [1]. Laboratory experiments [2; 3] suggest isotopic self shielding during gas phase photolysis of SO2 present at wavelengths shorter than 220 nm as the dominant mechanism for MIF. The UV absorption of SO2 is dominated by the C1B2-X1A1 electronic system which comprises strong vibrational bands extending from 170 - 230 nm. Within an atmosphere consisting of low O2 and O3 concentrations, such as that predicted for the early Earth, UV radiation would penetrate deep into the ancient Earth’s atmosphere in the 180 - 220 nm range driving the photolysis of SO2. We have conducted the first ever high resolution measurements of the photo absorption cross sections of several isotopologues of SO2, namely 32SO2, 33SO2, 34SO2 and 36SO2, using the Imperial College UV Fourier transform spectrometer [4] which is ideal for high resolution, broad-band, VIS/UV measurements. The cross sections are being measured at Imperial College at initial resolutions of 1.0 cm-1 which will be increased to resolutions < 0.5 cm-1 for inclusion in photochemical models of the early Earth’s atmosphere in order to more reliably interpret the sulphur isotope ratios found in ancient rock samples [5]. For discussion and interpretation of the photochemical models see the abstract by Lyons et al.(this meeting). References [1] J. Farquhar and B.A. Wing. Earth and Planetary Science Letters, 213:1-13, 2003. [2] J. Farquhar, J. Savarino, S. Airieau, and M.H Thiemens. Journal of Geophysical Research,106:32829-32839, 2001. [3] A. Pen and R. N. Clayton.Geochimica et Cosmochimica Acta Supplement,72:734, 2008. [4] J.C. Pickering. Vibrational Spectroscopy, 29(1-2):27 - 43, 2002. [5] J.R. Lyons. Geophys.Res. Lett, 34:L22811, 2007. Initial 1.0 cm-1 resolution photoabsorption cross sections of the 32SO2, 33SO2, and 34SO2 isotopologues recorded at Imperial College.

Blackie, D.; Stark, G.; Lyons, J. R.; Pickering, J.; Smith, P. L.; Thorne, A.

2010-12-01

397

Implementation of ALARA radiation protection on the ISS through polyethylene shielding augmentation of the Service Module Crew Quarters  

NASA Astrophysics Data System (ADS)

With 5-7 month long duration missions at 51.6° inclination in Low Earth Orbit, the ionizing radiation levels to which International Space Station (ISS) crewmembers are exposed will be the highest planned occupational exposures in the world. Even with the expectation that regulatory dose limits will not be exceeded during a single tour of duty aboard the ISS, the "as low as reasonably achievable" (ALARA) precept requires that radiological risks be minimized when possible through a dose optimization process. Judicious placement of efficient shielding materials in locations where crewmembers sleep, rest, or work is an important means for implementing ALARA for spaceflight. Polyethylene (C nH n) is a relatively inexpensive, stable, and, with a low atomic number, an effective shielding material that has been certified for use aboard the ISS. Several designs for placement of slabs or walls of polyethylene have been evaluated for radiation exposure reduction in the Crew Quarters (CQ) of the Zvezda (Star) Service Module. Optimization of shield designs relies on accurate characterization of the expected primary and secondary particle environment and modeling of the predicted radiobiological responses of critical organs and tissues. Results of the studies shown herein indicate that 20% or more reduction in equivalent dose to the CQ occupant is achievable. These results suggest that shielding design and risk analysis are necessary measures for reducing long-term radiological risks to ISS inhabitants and for meeting legal ALARA requirements. Verification of shield concepts requires results from specific designs to be compared with onboard dosimetry.

Shavers, M. R.; Zapp, N.; Barber, R. E.; Wilson, J. W.; Qualls, G.; Toupes, L.; Ramsey, S.; Vinci, V.; Smith, G.; Cucinotta, F. A.

2004-01-01

398

Implementation of ALARA radiation protection on the ISS through polyethylene shielding augmentation of the Service Module crew quarters  

NASA Astrophysics Data System (ADS)

With 5 to 7-month long duration missions at 51.6° inclination in Low Earth Orbit, the ionizing radiation levels to which International Space Station (ISS) crewmembers are exposed will be the highest planned occupational exposures in the world. Even with the expectation that regulatory dose limits will not be exceeded during a single tour of duty aboard the ISS, the "as low as reasonably achievable" (ALARA) precept requires that radiological risks be minimized when possible through an dose optimization process. Judicious placement of efficient shielding materials in locations where crewmembers sleep, rest, or work is an important means for implementing ALARA for spaceflight. Polyethylene (Cn Hn ), is a relatively inexpensive, stable, and, with a low atomic number, an effective shielding material that has been certified for use aboard the ISS. Several designs for placement of slabs or walls of polyethylene have been evaluated for radiation exposure reduction in the Crew Quarters (CQ) of the Zvezda (Star) Service Module. Optimization of shield designs relies on accurate characterization of the expected primary and secondary particle environment and modeling of the predicted radiobiological responses of critical organs and tissues. Results of the studies shown herein indicate that 20% or more reduction in dose equivalent to the CQ occupant is achievable. These results suggest that shielding design and risk analysis are necessary measures for reducing long-term radiological risks to ISS inhabitants and for meeting legal ALARA requirements. Verification of shield concepts requires results from specific designs to be compared with onboard dosimetry.

Shavers, M.; Zapp, N.; Barber, R.; Wilson, J.; Qualls, G.; Toupes, L.; Ramsey, S.; Vinci, V.; Smith, G.; Cucinotta, F.

399

Implementation of ALARA radiation protection on the ISS through polyethylene shielding augmentation of the Service Module Crew Quarters.  

PubMed

With 5-7 month long duration missions at 51.6 degrees inclination in Low Earth Orbit, the ionizing radiation levels to which International Space Station (ISS) crewmembers are exposed will be the highest planned occupational exposures in the world. Even with the expectation that regulatory dose limits will not be exceeded during a single tour of duty aboard the ISS, the "as low as reasonably achievable" (ALARA) precept requires that radiological risks be minimized when possible through a dose optimization process. Judicious placement of efficient shielding materials in locations where crewmembers sleep, rest, or work is an important means for implementing ALARA for spaceflight. Polyethylene (CnHn) is a relatively inexpensive, stable, and, with a low atomic number, an effective shielding material that has been certified for use aboard the ISS. Several designs for placement of slabs or walls of polyethylene have been evaluated for radiation exposure reduction in the Crew Quarters (CQ) of the Zvezda (Star) Service Module. Optimization of shield designs relies on accurate characterization of the expected primary and secondary particle environment and modeling of the predicted radiobiological responses of critical organs and tissues. Results of the studies shown herein indicate that 20% or more reduction in equivalent dose to the CQ occupant is achievable. These results suggest that shielding design and risk analysis are necessary measures for reducing long-term radiological risks to ISS inhabitants and for meeting legal ALARA requirements. Verification of shield concepts requires results from specific designs to be compared with onboard dosimetry. PMID:15880921

Shavers, M R; Zapp, N; Barber, R E; Wilson, J W; Qualls, G; Toupes, L; Ramsey, S; Vinci, V; Smith, G; Cucinotta, F A

2004-01-01

400

Conditions of Exciting Coils Used in Evaluation of Shielding Factor of Magnetically Shielded Rooms for Uniform Magnetic Field  

Microsoft Academic Search

To shield the environmental magnetic noises, magnetically shielded rooms (MSRs) are used for biomagnetic measurements, etc. The sources of environmental noises are far away from the MSR, in such a way that almost uniform magnetic field is applied to the MSR. To evaluate the shielding factor for the uniform magnetic field in a construction site, the magnetic noises are applied

Shunya Odawara; Kazuhiro Muramatsu; Yanhui Gao; Shogo Komori; Keita Yamazaki; Toshifumi Shinnoh; Takao Yamaguchi; Mitsuru Sakakibara; Masao Shimokawa

2011-01-01

401

Dust Abatement in Shield Supports by Means of Extraction and Precipitation of the Fine Dust in the Gaps Between Shields.  

National Technical Information Service (NTIS)

Shield supports are used in coal mines all over the world. The shielding of the face area is not sufficient, however, and dust will be raised especially when the shields are moved. The resulting dust loads often exceed the maximum permissible values, so t...

U. Oden

1981-01-01

402

Design and Development of an In-Space Deployable Sun Shield for the Atlas Centaur  

NASA Technical Reports Server (NTRS)

The Centaur, by virtue of its use of high specific-impulse (Isp) LO2/LH2 propellants, has initial mass-to-orbit launch requirements less than half of those upper stages using storable propellants. That is, for Earth escape or GSO missions the Centaur is half the launch weight of a storable propellant upper stage. A drawback to the use of Liquid oxygen and liquid hydrogen, at 90 K and 20 K respectively, over storable propellants is the necessity of efficient cryogen storage techniques that minimize boil-off from thermal radiation in space. Thermal blankets have been used successfully to shield both the Atlas Centaur and Titan Centaur. These blankets are protected from atmospheric air loads during launch by virtue of the fact that the Centaur is enclosed within the payload fairing. The smaller Atlas V vehicle, the Atlas 400, has the Centaur exposed to the atmosphere during launch, and therefore, to date has not flown with thermal blankets shielding the Centaur. A design and development effort is underway to fly a thermal shield on the Atlas V 400 vehicle that is not put in place until after the payload fairing jettisons. This can be accomplished by the use of an inflatable and deployable thermal blanket referred to as the Centaur Sun Shield (CSS). The CSS design is also scalable for use on a Delta upper stage, and the technology potentially could be used for telescope shades, re-entry shields, solar sails and propellant depots. A Phase I effort took place during 2007 in a partnership between ULA and ILC Dover which resulted in a deployable proof-of-concept Sun Shield being demonstrated at a test facility in Denver. A Phase H effort is underway during 2008 with a partnership between ULA, ILC, NASA Glenn Research Center (GRC) and NASA Kennedy Space Center (KSC) to define requirements, determine materials and fabrication techniques, and to test components in a vacuum chamber at cold temperatures. This paper describes the Sun Shield development work to date, and the future plans leading up to a flight test in the 2011 time frame.

Dew, Michael; Allwein, Kirk; Kutter, Bernard; Ware, Joanne; Lin, John; Madlangbayan, Albert; Willey, Cliff; Pitchford, Brian; O'Neil, Gary

2008-01-01

403

THE STUDY ON THE INFLUENCE TO THE GROUND BY SHIELD TUNNELING CONSIDERING UPHEAVAL AND SUBSIDANCE LIMIT PRESSURE  

NASA Astrophysics Data System (ADS)

We observed upheavals of the earth's surface during excavating the tunnel at shallow overburden ground with the cast-in-place lining method. But remarkable upheavals have not been generally observed on the same situation with the shield tunneling method. The present paper examined the difference between two tunneling methods by keeping our eyes to the consolidating time of grout materials. We definited the influence range and considered that shear stresses don't work only on 2 side walls but also on 4 walls in the Terzaghi's earth pressure and calculated subsidence and upheaval limit pressure. Furthermore, We studied the correlation between the ground deformation and the influence range.

Chishiro, Keizo; Iura, Tomomi; Salto, Jun

404

The early faint sun paradox: Organic shielding of ultraviolet-labile greenhouse gases  

SciTech Connect

Atmospheric mixing ratios of {approximately}10{sup -5 {+-}1} for ammonia on the early Earth would have been sufficient, through the resulting greenhouse warming, to counteract the temperature effects of the faint early sun. One argument against such model atmospheres has been the short time scale for ammonia photodissociation by solar ultraviolet light. Here it is shown that ultraviolet absorption by steady-state amounts of high-altitude organic solids produced from methane photolysis may have shielded ammonia sufficiently that ammonia resupply rates were able to maintain surface temperatures above freezing. 78 refs., 2 figs., 1 tab.

Sagan, C. [Cornell Univ., Ithaca, NY (United States)] [Cornell Univ., Ithaca, NY (United States); Chyba, C. [Univ. of Arizona, Tucson, AZ (United States)] [Univ. of Arizona, Tucson, AZ (United States)

1997-05-23

405

The early faint sun paradox: organic shielding of ultraviolet-labile greenhouse gases  

NASA Technical Reports Server (NTRS)

Atmospheric mixing ratios of approximately 10(-5 +/- 1) for ammonia on the early Earth would have been sufficient, through the resulting greenhouse warming, to counteract the temperature effects of the faint early sun. One argument against such model atmospheres has been the short time scale for ammonia photodissociation by solar ultraviolet light. Here it is shown that ultraviolet absorption by steady-state amounts of high-altitude organic solids produced from methane photolysis may have shielded ammonia sufficiently that ammonia resupply rates were able to maintain surface temperatures above freezing.

Sagan, C.; Chyba, C.

1997-01-01

406

Supplemental heating of deposition tooling shields  

DOEpatents

A method of reducing particle generation from the thin coating deposited on the internal surfaces of a deposition chamber which undergoes temperature variation greater than 100.degree. C. comprising maintaining the temperature variation of the internal surfaces low enough during the process cycle to keep thermal expansion stresses between the coating and the surfaces under 500 MPa. For titanium nitride deposited on stainless steel, this means keeping temperature variations under approximately 70.degree. C. in a chamber that may be heated to over 350.degree. C. during a typical processing operation. Preferably, a supplemental heater is mounted behind the upper shield and controlled by a temperature sensitive element which provides feedback control based on the temperature of the upper shield.

Ohlhausen, James A. (Albuquerque, NM); Peebles, Diane E. (Albuquerque, NM); Hunter, John A. (Albuquerque, NM); Eckelmeyer, Kenneth H. (Albuquerque, NM)

2000-01-01

407

Electronically shielded solid state charged particle detector  

DOEpatents

An electronically shielded solid state charged particle detector system having enhanced radio frequency interference immunity includes a detector housing with a detector entrance opening for receiving the charged particles. A charged particle detector having an active surface is disposed within the housing. The active surface faces toward the detector entrance opening for providing electrical signals representative of the received charged particles when the received charged particles are applied to the active surface. A conductive layer is disposed upon the active surface. In a preferred embodiment, a nonconductive layer is disposed between the conductive layer and the active surface. The conductive layer is electrically coupled to the detector housing to provide a substantially continuous conductive electrical shield surrounding the active surface. The inner surface of the detector housing is supplemented with a radio frequency absorbing material such as ferrite.

Balmer, David K. (155 Coral Way, Broomfield, CO 80020); Haverty, Thomas W. (1173 Logan, Northglenn, CO 80233); Nordin, Carl W. (7203 W. 32nd Ave., Wheatridge, CO 80033); Tyree, William H. (1977 Senda Rocosa, Boulder, CO 80303)

1996-08-20

408

Phase shielding soliton in parametrically driven systems.  

PubMed

Parametrically driven extended systems exhibit dissipative localized states. Analytical solutions of these states are characterized by a uniform phase and a bell-shaped modulus. Recently, a type of dissipative localized state with a nonuniform phase structure has been reported: the phase shielding solitons. Using the parametrically driven and damped nonlinear Schrödinger equation, we investigate the main properties of this kind of solution in one and two dimensions and develop an analytical description for its structure and dynamics. Numerical simulations are consistent with our analytical results, showing good agreement. A numerical exploration conducted in an anisotropic ferromagnetic system in one and two dimensions indicates the presence of phase shielding solitons. The structure of these dissipative solitons is well described also by our analytical results. The presence of corrective higher-order terms is relevant in the description of the observed phase dynamical behavior. PMID:23767606

Clerc, Marcel G; Garcia-Ñustes, Mónica A; Zárate, Yair; Coulibaly, Saliya

2013-05-01

409

Electronically shielded solid state charged particle detector  

DOEpatents

An electronically shielded solid state charged particle detector system having enhanced radio frequency interference immunity includes a detector housing with a detector entrance opening for receiving the charged particles. A charged particle detector having an active surface is disposed within the housing. The active surface faces toward the detector entrance opening for providing electrical signals representative of the received charged particles when the received charged particles are applied to the active surface. A conductive layer is disposed upon the active surface. In a preferred embodiment, a nonconductive layer is disposed between the conductive layer and the active surface. The conductive layer is electrically coupled to the detector housing to provide a substantially continuous conductive electrical shield surrounding the active surface. The inner surface of the detector housing is supplemented with a radio frequency absorbing material such as ferrite. 1 fig.

Balmer, D.K.; Haverty, T.W.; Nordin, C.W.; Tyree, W.H.

1996-08-20

410

Thermoforming plastic in lead shield construction  

SciTech Connect

Radiation treatments using low energy X-rays or electrons frequently require a final field defining shield to be placed on the patient's skin. A custom made lead cut-out is used to provide a close fit to a particular patient's surface contours. We have developed a procedure which utilizes POLYFORM thermoplastic to obtain a negative mold of the patient instead of the traditional plaster bandage or dental impression gel. The Polyform is softened in warm water, molded carefully over the patient's surface, and is removed when set or hardened, usually within five minutes. Then lead sheet cut-outs can be formed within this negative. For shielding cut-outs requiring thicker lead sheet, a positive is made from dental stone using this Polyform negative. We have found this procedure to be neat, fast and comfortable for both patient and the dosimetrist.

Abrahams, M.E.; Chow, C.H.; Loyd, M.D. (Univ. of Texas Medical Branch, Galveston (USA))

1989-09-01

411

Debye shielding in a nonextensive plasma  

SciTech Connect

The phenomenon of Debye Shielding is revisited within the theoretical framework of the Tsallis statistical mechanics. The plasma consists of nonextensive electrons and ions. Both the effective Debye length {lambda}{sub D}{sup q} and the fall-off of the electrostatic potential {Phi} are considered and a parameter study conducted. Owing to electron nonextensivity, the critical Mach number derived from the modified Bohm sheath criterion may become less than unity allowing therefore ions with speed less than ion-acoustic speed to enter the sheath from the main body of the plasma. Considering the wide relevance of collective processes, our analysis may be viewed as a first step toward a more comprehensive Debye shielding and electrostatic plasma sheath in nonequilibrium plasmas.

Ait Gougam, Leila; Tribeche, Mouloud [Faculty of Sciences-Physics, Theoretical Physics Laboratory (TPL), University of Bab-Ezzouar, U.S.T.H.B, B.P. 32, El Alia, Algiers 16111 (Algeria)

2011-06-15

412

Magnetic radiation shielding - An idea whose time has returned?  

NASA Technical Reports Server (NTRS)

One solution to the problem of shielding crew from particulate radiation in space is to use active electromagnetic shielding. Practical types of shield include the magnetic shield, in which a strong magnetic field diverts charged particles from the crew region, and the magnetic/electrostatic plasma shield, in which an electrostatic field shields the crew from positively charged particles, while a magnetic field confines electrons from the space plasma to provide charge neutrality. Advances in technology include high-strength composite materials, high-temperature superconductors, numerical computational solutions to particle transport in electromagnetic fields, and a technology base for construction and operation of large superconducting magnets. These advances make electromagnetic shielding a practical alternative for near-term future missions.

Landis, Geoffrey A.

1991-01-01

413

Enrichment Determination of Uranium in Shielded Configurations  

SciTech Connect

The determination of the enrichment of uranium is required in many safeguards and security applications. Typical methods of determining the enrichment rely on detecting the 186 keV gamma ray emitted by {sup 235}U. In some applications, the uranium is surrounded by external shields, and removal of the shields is undesirable. In these situations, methods relying on the detection of the 186 keV gamma fail because the gamma ray is shielded easily. Oak Ridge National Laboratory (ORNL) has previously measured the enrichment of shielded uranium metal using active neutron interrogation. The method consists of measuring the time distribution of fast neutrons from induced fissions with large plastic scintillator detectors. To determine the enrichment, the measurements are compared to a calibration surface that is created from Monte Carlo simulations where the enrichment in the models is varied. In previous measurements, the geometry was always known. ORNL is extending this method to situations where the geometry and materials present are not known in advance. In the new method, the interrogating neutrons are both time and directionally tagged, and an array of small plastic scintillators measures the uncollided interrogating neutrons. Therefore, the attenuation through the item along many different paths is known. By applying image reconstruction techniques, an image of the item is created which shows the position-dependent attenuation. The image permits estimating the geometry and materials present, and these estimates are used as input for the Monte Carlo simulations. As before, simulations predict the time distribution of induced fission neutrons for different enrichments. Matching the measured time distribution to the closest prediction from the simulations provides an estimate of the enrichment. This presentation discusses the method and provides results from recent simulations that show the importance of knowing the geometry and materials from the imaging system.

Crye, Jason Michael [ORNL; Hall, Howard L [ORNL; McConchie, Seth M [ORNL; Mihalczo, John T [ORNL; Pena, Kirsten E [ORNL

2011-01-01

414

Grounding and shielding in the accelerator environment  

SciTech Connect

Everyday features of the accelerator environment include long cable runs, high power and low level equipment sharing building space, stray electromagnetic fields and ground voltage differences between the sending and receiving ends of an installation. This paper pictures some Fermilab installations chosen to highlight significant features and presents practices, test methods and equipment that have been helpful in achieving successful shielding. Throughout the report are numbered statements aimed at summarizing good practices and avoiding pitfalls.

Kerns, Q.

1991-01-01

415

SINBAD: Shielding integral benchmark archive and database  

SciTech Connect

SINBAD is a new electronic database developed to store a variety of radiation shielding benchmark data so that users can easily retrieve and incorporate the data into their calculations. SINBAD is an excellent data source for users who require the quality assurance necessary in developing cross-section libraries or radiation transport codes. The future needs of the scientific community are best served by the electronic database format of SINBAD and its user-friendly interface, combined with its data accuracy and integrity.

Hunter, H.T.; Ingersoll, D.T.; Roussin, R.W. [and others

1996-04-01

416

Trailing Shield For Welding On Pipes  

NASA Technical Reports Server (NTRS)

Trailing shield ensures layer of inert gas covers hot, newly formed bead between two tubes or pipes joined by plasma arc welding. Inert gas protects weld bead from oxidation by air until cooler and less vulnerable to oxidation. Intended for use on nickel-base alloy pipes, on which weld beads remain hot enough to oxidize after primary inert-gas purge from welding-torch cup has passed.

Coby, John B., Jr.; Gangl, Kenneth J.

1991-01-01

417

Applicability of oxide superconductor to magnetic shielding  

Microsoft Academic Search

Magnetic shielding capability has been investigated on the Y-Ba-Cu-O oxide superconductor, aiming at a practical use of oxide superconductors. Critical-transport-current density and magnetization were measured using the four-terminal and electromagnetic methods at temperatures of 77 K and 4.2 K. The results indicated that the critical-current density by the transport measurement was two orders of magnitude lower than that by the

T. Okada; K. Takahata; S. Nishijima; S. Yoshida; T. Hanasaka

1989-01-01

418

Sandwich composite approach for EMI shielding structures  

Microsoft Academic Search

A sandwich composite approach has been employed to develop epoxy based polymer matrix composite materials to realize a class of lightweight structures capable of shielding electromagnetic interference (EMI). Hollow glass microspheres embedded syntactic foams (thickness ap 2 mm; density ap 0.6 g\\/cc) of two different varieties have been used as core materials in these sandwich constructions (total thickness ap 2.6

S. Dasgupta; K. Ravi Sekhart; B. N. Ravishankar; M. Kumar; S. Sankaran

2008-01-01

419

Activation characteristics of concrete shields containing colemanite  

NASA Astrophysics Data System (ADS)

This paper presents the theoretical results of the activation characteristics of a concrete shield containing colemanite, which is a boron-bearing mineral. Calculations are performed with a computer code, ANITA. The total activity and dose values of the sheilds with or without colemanite are compared for different continuous irradiation periods and neutron fluxes. The effect of colemanite on the activity is discussed by investigating the predominant radioisotopes at the shutdown radioactive inventory and the reactions that produce them.

Yarar, Yasemin

1996-10-01

420

Spallation Neutron Source Radiation Shielding Issues  

SciTech Connect

This paper summarizes results of Spallation Neutron Source calculations to estimate radiation hazards and shielding requirements for activated Mercury, target components, target cooling water, and {sup 7}Be plateout. Dose rates in the accelerator tunnel from activation of magnets and concrete were investigated. The impact of gaps and other streaming paths on the radiation environment inside the test cell during operation and after shutdown were also assessed.

Azmy, Y.Y.; Barnes, J.M.; Drischler, J.D.; Johnston, J.O.; Lillie, R.A.; McNeilly, G.S.; Santoro, R.T.

1999-11-14

421

Fermilab Booster beam collimation and shielding  

Microsoft Academic Search

The beam power in the upgraded Booster at 8 GeV and 10 Hz will be 64 kW. Beam loss can result in high radiation loads in the ring. The purpose of a new beam halo cleaning system is to localize proton losses in specially shielded regions. Calculations show that this 2-stage collimation system will localize about 99% of beam loss

N. V. Mokhovy; A. I. Drozhdin; P. H. Kasper; J. R. Lackey; E. J. Prebys; R. C. Webber

2003-01-01

422

Why Earth Science?  

ERIC Educational Resources Information Center

This article briefly describes Earth science. The study of Earth science provides the foundation for an understanding of the Earth, its processes, its resources, and its environment. Earth science is the study of the planet in its entirety, how its lithosphere, atmosphere, hydrosphere, and biosphere work together as systems and how they affect…

Smith, Michael J.

2004-01-01

423

Crew Earth Observations  

NASA Technical Reports Server (NTRS)

Crew Earth Observations (CEO) takes advantage of the crew in space to observe and photograph natural and human-made changes on Earth. The photographs record the Earth's surface changes over time, along with dynamic events such as storms, floods, fires and volcanic eruptions. These images provide researchers on Earth with key data to better understand the planet.

Runco, Susan

2009-01-01

424

Topographic evidence for shield volcanism on Io  

SciTech Connect

Similarities between terrestrial shield volcanoes and a volcano on Io observed in Voyager I imagery of the satellite at 30/sup 0/ S, 246/sup 0/ W are delineated. A photoclinometry model was used to numerically estimate the slope based on the Minnaert photometric function. The slope values are accurate to within 10 deg on the sun-facing slope and 1 deg on the shadow side. As found with shield volcanoes, the feature has a central edifice, 40-50 km in diameter, and a broad, elliptical base, 77 x 90 km across. The summit of the Io volcano is 2.2-2.8 km above the surrounding plane and contains a caldera about 5 km in diameter. The similarity in shape between basaltic terrestrial shield volcanoes and the Io volcano indicates that the Io feature may also be composed of basalt. The composition could be sulfur if the heat flow was under 0.05 W/sq m, as it might have been in later stages of formation. 9 references.

Moore, J.M.; Mcewen, A.S.; Albin, E.F.; Greeley, R.

1986-07-01

425

GRAVITATIONAL FIELD SHIELDING AND SUPERNOVA EXPLOSIONS  

SciTech Connect

A new mechanism for supernova explosions called gravitational field shielding is proposed, in accord with a five-dimensional fully covariant Kaluza-Klein theory with a scalar field that unifies the four-dimensional Einsteinian general relativity and Maxwellian electromagnetic theory. It is shown that a dense compact collapsing core of a star will suddenly turn off or completely shield its gravitational field when the core collapses to a critical density, which is inversely proportional to the square of mass of the core. As the core suddenly turns off its gravity, the extremely large pressure immediately stops the core collapse and pushes the mantle material of supernova moving outward. The work done by the pressure in the expansion can be the order of energy released in a supernova explosion. The gravity will resume and stop the core from a further expansion when the core density becomes less than the critical density. Therefore, the gravitational field shielding leads a supernova to impulsively explode and form a compact object such as a neutron star as a remnant. It works such that a compressed spring will shoot the oscillator out when the compressed force is suddenly removed.

Zhang, T. X. [Physics Department, Alabama A and M University, Normal, AL 35762 (United States)

2010-12-20

426

The anticoincidence shield of the PAMELA space experiment  

NASA Astrophysics Data System (ADS)

The PAMELA space experiment will be launched in 2005 onboard a Russian Resurs DK1 satellite, orbiting Earth at an altitude varying between 300 and 600 km. The main scientific goal is a study of the antimatter component of the cosmic radiation. The semipolar orbit (71°) allows PAMELA to investigate a wide range of energies for antiprotons (80 MeV 190 GeV) and positrons (50 MeV 270 GeV). Three years of data taking will provide unprecedented statistics in this energy range and will set the upper limit for the ratio He¯/He below 10-7. PAMELA is built around a permanent magnet silicon spectrometer, surrounded by a plastic scintillator anticoincidence shield. The anticounter scintillators are used to aid in the rejection of background from particles which do not cleanly enter the acceptance of the experiment but which are responsible for coincidental energy deposits in the trigger scintillators (‘false triggers’). Information from the anticounter system can be included as a veto in a second level trigger, to exclude the acquisition of events generated by such false triggers. The construction of the anticounter system is described, along with its functionality and performance. The read-out electronics and the LED-based monitoring system are also described. Test-beam and simulation studies of the system are reviewed.

Orsi, S.; Carlson, P.; Lund, J.; Lundquist, J.; Pearce, M.

427

The Anticoincidence Shield of the PAMELA Space Experiment  

NASA Astrophysics Data System (ADS)

The PAMELA space experiment will be launched in 2004 onboard a Russian Resurs DK1 satellite, orbiting Earth at an altitude of 300-600 km. The main scientific goal is a study of the antimatter component of the cosmic radiation. The semipolar orbit (71°) allows PAMELA to investigate a wide range of energies for antiprotons (80 MeV-190 GeV) and positrons (50 MeV-270 GeV). Three years of data taking will provide unprecedented statistics in this energy range and will set the upper limit for the ratio He{bar}/He below 10-7. PAMELA is built around a permanent magnet silicon spectrometer, surrounded by a plastic scintillator anticoincidence shield. The anticounter scintillators are used to aid in the rejection of background from particles not cleanly entering the acceptance of the tracker. Information from the anticounter system will be included as a veto in a second level trigger, to exclude the acquisition of events generated by false triggers. The construction of the anticounter system is described, along with its functionality and performance. The custom read-out electronics and the LED-based monitoring system are also described in detail. Test-beam, simulation and qualification studies of the system are reviewed.

Orsi, S.; Carlson, P.; Lund, J.; Lundquist, J.; Pearce, M.

428

Earth Observatory Glossary  

NSDL National Science Digital Library

The Earth Observatory Glossary defines words from space science, ecology and Earth science. It is part of the NASA Earth Observatory site, which provides new satellite imagery and scientific information about Earth with a focus on climate and environmental change. The new glossary mode allows users to browse the Earth Observatory site with special terms highlighted that, when selected, will take you to the appropriate entry in the glossary.

429

Earth's Radiation Belts: The View from Juno's Cameras  

NASA Astrophysics Data System (ADS)

Juno's cameras, particle instruments, and ultraviolet imaging spectrograph have been heavily shielded for operation within Jupiter's high radiation environment. However, varying quantities of >1-MeV electrons and >10-MeV protons will be energetic enough to penetrate instrument shielding and be detected as transient background signatures by the instruments. The differing shielding profiles of Juno's instruments lead to differing spectral sensitivities to penetrating electrons and protons within these regimes. This presentation will discuss radiation data collected by Juno in the Earth's magnetosphere during Juno's October 9, 2013 Earth flyby (559 km altitude at closest approach). The focus will be data from Juno's Stellar Reference Unit, Advanced Stellar Compass star cameras, and JunoCam imager acquired during coordinated proton measurements within the inner zone and during the spacecraft's inbound and outbound passages through the outer zone (L ~3-5). The background radiation signatures from these cameras will be correlated with dark count background data collected at these geometries by Juno's Ultraviolet Spectrograph (UVS) and Jupiter Energetic Particle Detector Instrument (JEDI). Further comparison will be made to Van Allen Probe data to calibrate Juno's camera results and contribute an additional view of the Earth's radiation environment during this unique event.

Becker, H. N.; Joergensen, J. L.; Hansen, C. J.; Caplinger, M. A.; Ravine, M. A.; Gladstone, R.; Versteeg, M. H.; Mauk, B.; Paranicas, C.; Haggerty, D. K.; Thorne, R. M.; Connerney, J. E.; Kang, S. S.

2013-12-01

430

Tidal effects in the controlled-source ULF electromagnetic field on the Baltic crystalline shield  

NASA Astrophysics Data System (ADS)

The results of the experiment on studying the dynamics of the electromagnetic field (EM) generated by the stationary controlled ULF-band source during 30 days on the Baltic crystalline shield are presented. Diurnal variations in the EM fields and slow variations in the surface impedance with a period of about 14 days are revealed. The diurnal variations in the fields are mainly due to the fluctuations in the ionospheric parameters caused by the changes in the daytime ionization of the ionosphere by solar radiation. By comparing the harmonic component with a period of about 14 days, which was established in the time series of surface impedance, with the slow tidal deformations of the Earth's crust, we revealed the correlation between the EM variations and tidal processes in the Earth. The estimates for the probable changes induced by tidal deformations in the structure and conductivity of the underlying medium are obtained by modeling.

Tereshchenko, E. D.; Sidorenko, A. E.; Grigoriev, V. F.

2014-01-01

431

Comparison of Martian Meteorites and Martian Regolith as Shield Materials for Galactic Cosmic Rays  

NASA Astrophysics Data System (ADS)

Theoretical calculations of radiation attenuation due to energetic galactic cosmic rays behind Martian rock and Martian regolith material have been made to compare their utilization as shields for advanced manned missions to Mars because the detailed chemical signature of Mars is distinctly different from Earth. The modified radiation fields behind the Martian rocks and the soil model were generated by solving the Boltzmann equation using a HZETRN system with the 1977 Solar Minimum environmental model. For the comparison of the attenuation characteristics, dose and dose equivalent are calculated for the five different subgroups of Martian rocks and the Martian regolith. The results indicate that changes in composition of subgroups of Martian rocks have negligible effects on the overall shielding properties because of the similarity of their constituents. The differences for dose and dose equivalent of these materials relative to those of Martian regolith are within 0.5 and 1 percent, respectively. Therefore, the analysis of Martian habitat construction options using in situ materials according to the Martian regolith model composition is reasonably accurate. Adding an epoxy to Martian regolith, which changes the major constituents of the material, enhances shielding properties because of the added hydrogenous constituents.

Kim, Myung-Hee Y.; Thibeault, Sheila A.; Simonsen, Lisa C.; Wilson, John W.

1998-10-01

432

Comparison of Martian Meteorites and Martian Regolith as Shield Materials for Galactic Cosmic Rays  

NASA Technical Reports Server (NTRS)

Theoretical calculations of radiation attenuation due to energetic galactic cosmic rays behind Martian rock and Martian regolith material have been made to compare their utilization as shields for advanced manned missions to Mars because the detailed chemical signature of Mars is distinctly different from Earth. The modified radiation fields behind the Martian rocks and the soil model were generated by solving the Boltzmann equation using a HZETRN system with the 1977 Solar Minimum environmental model. For the comparison of the attenuation characteristics, dose and dose equivalent are calculated for the five different subgroups of Martian rocks and the Martian regolith. The results indicate that changes in composition of subgroups of Martian rocks have negligible effects on the overall shielding properties because of the similarity of their constituents. The differences for dose and dose equivalent of these materials relative to those of Martian regolith are within 0.5 and 1 percent, respectively. Therefore, the analysis of Martian habitat construction options using in situ materials according to the Martian regolith model composition is reasonably accurate. Adding an epoxy to Martian regolith, which changes the major constituents of the material, enhances shielding properties because of the added hydrogenous constituents.

Kim, Myung-Hee Y.; Thibeault, Sheila A.; Simonsen, Lisa C.; Wilson, John W.

1998-01-01

433

Peralkaline and peraluminous granites and related mineral deposits of the Arabian Shield, Kingdom of Saudi Arabia  

USGS Publications Warehouse

In the Precambrian Arabian Shield, granitoid plutonic rocks are widespread and range in age from 800 to 550 Ma old; but the mineral-resource potential associated with these plutonic rocks is restricted mainly to the younger, postorogenic granites. Two granite types of current economic interest are zirconium- niobium-enriched per alkaline granites and tin-tungsten-enriched peraluminous granites. Both types are highly evolved, are enriched in lithium, rubidium, and fluorine, and have distinctive mineralogy, textures, and chemistry. The zirconium-niobium-enriched granites are related to medium- to large-sized plutons and complexes of peralkaline granite, and the tin-tungsten-enriched granites are related to medium-sized plutons of biotite or biotite-muscovite granite. Existing geochemical and geologic data for many parts of the Arabian Shield were compiled as a basis for evaluating the resource potential of the granites of the Shield. Commodities associated with granites that have potential for economic mineral deposits include tin, tungsten, molybdenum, beryllium, niobium, tantalum, zirconium, uranium, thorium, rare-earth elements, and fluorite. Prospecting methods useful in discriminating those granites having significant economic potential include reconnaissance geologic mapping, petrographic and mineralogic studies, geochemical sampling of rock and wadi sediment, and radiometric surveying.

Elliott, James E.

1983-01-01

434

Detecting the oldest geodynamo and attendant shielding from the solar wind: Implications for habitability  

NASA Astrophysics Data System (ADS)

The onset and nature of the earliest geomagnetic field is important for understanding the evolution of the core, atmosphere and life on Earth. A record of the early geodynamo is preserved in ancient silicate crystals containing minute magnetic inclusions. These data indicate the presence of a geodynamo during the Paleoarchean, between 3.4 and 3.45 billion years ago. While the magnetic field sheltered Earth’s atmosphere from erosion at this time, standoff of the solar wind was greatly reduced, and similar to that during modern extreme solar storms. These conditions suggest that intense radiation from the young Sun may have modified the atmosphere of the young Earth by promoting loss of volatiles, including water. Such effects would have been more pronounced if the field were absent or very weak prior to 3.45 billion years ago, as suggested by some models of lower mantle evolution. The frontier is thus trying to obtain geomagnetic field records that are ?3.45 billion-years-old, as well as constraining solar wind pressure for these times. In this review we suggest pathways for constraining these parameters and the attendant history of Earth’s deep interior, hydrosphere and atmosphere. In particular, we discuss new estimates for solar wind pressure for the first 700 million years of Earth history, the competing effects of magnetic shielding versus solar ion collection, and bounds on the detection level of a geodynamo imposed by the presence of external fields. We also discuss the prospects for constraining Hadean-Paleoarchean magnetic field strength using paleointensity analyses of zircons.

Tarduno, John A.; Blackman, Eric G.; Mamajek, Eric E.

2014-08-01

435

Radiation shielding for future space exploration missions  

NASA Astrophysics Data System (ADS)

Scope and Method of Study. The risk to space crew health and safety posed by exposure to space radiation is regarded as a significant obstacle to future human space exploration. To countermand this risk, engineers and designers in today's aerospace community will require detailed knowledge of a broad range of possible materials suitable for the construction of future spacecraft or planetary surface habitats that provide adequate protection from a harmful space radiation environment. This knowledge base can be supplied by developing an experimental method that provides quantitative information about a candidate material's space radiation shielding efficacy with the understanding that (1) shielding is currently the only practical countermeasure to mitigate the effects of space radiation on human interplanetary missions, (2) any mass of a spacecraft or planetary surface habitat necessarily alters the incident flux of ionizing radiation on it, and (3) the delivery of mass into LEO and beyond is expensive and therefore may benefit from the possible use of novel multifunctional materials that could in principle reduce cost as well as ionizing radiation exposure. The developed method has an experimental component using CR-39 PNTD and Al2O3:C OSLD that exposes candidate space radiation shielding materials of varying composition and depth to a representative sample of the GCR spectrum that includes 1 GeV 1H and 1 GeV/n 16O, 28Si, and 56Fe heavy ion beams at the BNL NSRL. The computer modeling component of the method used the Monte Carlo radiation transport code FLUKA to account for secondary neutrons that were not easily measured in the laboratory. Findings and Conclusions. This study developed a method that quantifies the efficacy of a candidate space radiation shielding material relative to the standard of polyethylene using a combination of experimental and computer modeling techniques. The study used established radiation dosimetry techniques to present an empirical weighted figure of merit (WFoM) approach that quantifies the effectiveness of a candidate material to shield space crews from the whole of the space radiation environment. The results of the WFoM approach should prove useful to designers and engineers in seeking alternative materials suitable for the construction of spacecraft or planetary surface habitats needed for long-term space exploration missions. The dosimetric measurements in this study have confirmed the principle of good space radiation shielding design by showing that low-Z¯ materials are most effective at reducing absorbed dose and dose equivalent while high-Z¯ materials are to be avoided. The relatively high WFoMs of carbon composite and lunar- and Martian-regolith composite could have important implications for the design and construction of future spacecraft or planetary surface habitats. The ground-based measurements conducted in this study have validated the heavy ion extension of FLUKA by producing normalized differential LET fluence spectra that are in good agreement with experiment.

DeWitt, Joel Michael

436

Cross Section Evaluation Group shielding benchmark compilation. Volume II  

SciTech Connect

At the time of the release of ENDF/B-IV in 1974, the Shielding Subcommittee had identified a series of 12 shielding data testing benchmarks (the SDT series). Most were used in the ENDF/B-IV data testing effort. A new concept and series was begun in the interim, the so-called Shielding Benchmark (SB) series. An effort was made to upgrade the SDT series as far as possible and to add new SB benchmarks. In order to be designated in the SB class, both an experiment and analysis must have been performed. The current recommended benchmark for Shielding Data Testing are listed. Until recently, the philosophy has been to include only citations to published references for shielding benchmarks. It is now our intention to provide adequate information in this volume for proper analysis of any new benchmarks added to the collection. These compilations appear in Section II, with the SB5 Fusion Reactor Shielding Benchmark as the first entry.

Rose, P.F.; Roussin, R.W.

1983-12-01

437

The Spallation Neutron Source (SNS) conceptual design shielding analysis  

SciTech Connect

The shielding design is important for the construction of an intense high-energy accelerator facility like the proposed Spallation Neutron Source (SNS) due to its impact on conventional facility design, maintenance operations, and since the cost for the radiation shielding shares a considerable part of the total facility costs. A calculational strategy utilizing coupled high energy Monte Carlo calculations and multi-dimensional discrete ordinates calculations, along with semi-empirical calculations, was implemented to perform the conceptual design shielding assessment of the proposed SNS. Biological shields have been designed and assessed for the proton beam transport system and associated beam dumps, the target station, and the target service cell and general remote maintenance cell. Shielding requirements have been assessed with respect to weight, space, and dose-rate constraints for operating, shutdown, and accident conditions. A discussion of the proposed facility design, conceptual design shielding requirements calculational strategy, source terms, preliminary results and conclusions, and recommendations for additional analyses are presented.

Johnson, J.O.; Odano, N.; Lillie, R.A.

1998-03-01

438

Shielding Design of the Spallation Neutron Source (SNS)  

SciTech Connect

The shielding design is important for the construction of an intense high-energy accelerator facility like the proposed Spallation Neutron Source (SNS) due to its impact on conventional facility design, maintenance operations, and since the cost for the radiation shielding shares a considerable part of the total facility costs. A calculational strategy utilizing coupled high energy Monte Carlo calculations and multi-dimensional discrete ordinates calculations, along with semi-empirical calculations, was implemented to perform the conceptual design shielding assessment of the proposed SNS. Biological shields have been designed and assessed for the proton beam transport system and associated beam dumps, the target station, and the target service cell and general remote maintenance cell. Shielding requirements have been assessed with respect to weight, space, and dose-rate constraints for operating, shutdown, and accident conditions. A discussion of the proposed facility design, conceptual design shielding requirements, calculational strategy, source terms, preliminary results and conclusions, and recommendations for additional analyses are presented.

Johnson, J.O.

1998-09-17

439

Structural Monitoring of Metro Infrastructure during Shield Tunneling Construction  

PubMed Central

Shield tunneling construction of metro infrastructure will continuously disturb the soils. The ground surface will be subjected to uplift or subsidence due to the deep excavation and the extrusion and consolidation of the soils. Implementation of the simultaneous monitoring with the shield tunnel construction will provide an effective reference in controlling the shield driving, while how to design and implement a safe, economic, and effective structural monitoring system for metro infrastructure is of great importance and necessity. This paper presents the general architecture of the shield construction of metro tunnels as well as the procedure of the artificial ground freezing construction of the metro-tunnel cross-passages. The design principles for metro infrastructure monitoring of the shield tunnel intervals in the Hangzhou Metro Line 1 are introduced. The detailed monitoring items and the specified alarming indices for construction monitoring of the shield tunneling are addressed, and the measured settlement variations at different monitoring locations are also presented.

Ran, L.; Ye, X. W.; Ming, G.; Dong, X. B.

2014-01-01

440

Early shielding research at Bettis Atomic Power Laboratory  

SciTech Connect

Reminiscences of shielding research at Bettis Atomic Power Laboratory (BAPL) always have in the background the reason for its existence - the design of efficient and safe reactors. Shielding is essential for personnel safety. However, the only computational tools available in the early 1950s were slide rules and desk calculators. Under these conditions, any shield desing calculation accurate within a factor of 2 was a good one, and the phrases close enough for shielding purposes' and including a factor for conservation' became a permanent part of the shielding vocabulary. This early work instilled a respect for hand calculations and the requirements that nay result, no matter how calculated, must meet the test of being reasonable and in line with previous experience. Even today, with sophisticated shielding programs available on the latest computers, calculated results must pass the same test.

Shure, K.; Wallace, O.J. (Westinghouse Electric Corp., West Mifflin, PA (United States))

1992-01-01

441

Snow shielding factors for cosmogenic nuclide dating inferred from Monte Carlo neutron transport simulations  

NASA Astrophysics Data System (ADS)

Conventional formulations of changes in cosmogenic nuclide production rates with snow cover are based on a mass-shielding approach, which neglects the role of neutron moderation by hydrogen. This approach can produce erroneous correction factors and add to the uncertainty of the calculated cosmogenic exposure ages. We use a Monte Carlo particle transport model to simulate fluxes of secondary cosmic-ray neutrons near the surface of the Earth and vary surface snow depth to show changes in neutron fluxes above rock or soil surface. To correspond with shielding factors for spallation and low-energy neutron capture, neutron fluxes are partitioned into high-energy, epithermal and thermal components. The results suggest that high-energy neutrons are attenuated by snow cover at a significantly higher rate (shorter attenuation length) than indicated by the commonly-used mass-shielding formulation. As thermal and epithermal neutrons derive from the moderation of high-energy neutrons, the presence of a strong moderator such as hydrogen in snow increases the thermal neutron flux both within the snow layer and above it. This means that low-energy production rates are affected by snow cover in a manner inconsistent with the mass-shielding approach and those formulations cannot be used to compute snow correction factors for nuclides produced by thermal neutrons. Additionally, as above-ground low-energy neutron fluxes vary with snow cover as a result of reduced diffusion from the ground, low-energy neutron fluxes are affected by snow even if the snow is at some distance from the site where measurements are made.

Zweck, Christopher; Zreda, Marek; Desilets, Darin

2013-10-01

442

X-ray transmissive debris shield  

DOEpatents

An X-ray debris shield for use in X-ray lithography that is comprised of an X-ray window having a layer of low density foam exhibits increased longevity without a substantial increase in exposure time. The low density foam layer serves to absorb the debris emitted from the X-ray source and attenuate the shock to the window so as to reduce the chance of breakage. Because the foam is low density, the X-rays are hardly attenuated by the foam and thus the exposure time is not substantially increased.

Spielman, Rick B. (Albuquerque, NM) [Albuquerque, NM

1996-01-01

443

X-ray transmissive debris shield  

DOEpatents

An X-ray debris shield for use in X-ray lithography that is comprised of an X-ray window having a layer of low density foam exhibits increased longevity without a substantial increase in exposure time. The low density foam layer serves to absorb the debris emitted from the X-ray source and attenuate the shock to the window so as to reduce the chance of breakage. Because the foam is low density, the X-rays are hardly attenuated by the foam and thus the exposure time is not substantially increased.

Spielman, R.B.

1996-05-21

444

Shielded serpentine traveling wave tube deflection structure  

DOEpatents

A shielded serpentine slow wave deflection structure (10) having a serpene signal conductor (12) within a channel groove (46). The channel groove (46) is formed by a serpentine channel (20) in a trough plate (18) and a ground plane (14). The serpentine signal conductor (12) is supported at its ends by coaxial feed through connectors 28. A beam interaction trough (22) intersects the channel groove (46) to form a plurality of beam interaction regions (56) wherein an electron beam (54) may be deflected relative to the serpentine signal conductor (12).

Hudson, Charles L. (Santa Barbara, CA); Spector, Jerome (Berkeley, CA)

1994-01-01

445

Equivalent-spherical-shield neutron dose calculations  

SciTech Connect

Neutron doses through 162-cm-thick spherical shields were calculated to be 1090 and 448 mrem/h for regular and magnetite concrete, respectively. These results bracket the measured data, for reinforced regular concrete, of /approximately/600 mrem/h. The calculated fraction of the high-energy (>20 MeV) dose component also bracketed the experimental data. The measured and calculated doses were for a graphite beam stop bombarded with 100 nA of 800-MeV protons. 6 refs., 2 figs., 1 tab.

Russell, G.J.; Robinson, H.

1988-01-01

446

SHIELD: Stellar Mass Estimates from Spitzer Imaging  

NASA Astrophysics Data System (ADS)

The Survey of HI in Extremely Low-mass Dwarfs (SHIELD) is an ongoing study of twelve galaxies with HI masses between 106 and 107 Solar masses, detected by the Arecibo Legacy Fast ALFA (ALFALFA) survey. The distribution of stellar mass in each system is a crucial component of our understanding of the baryonic and dark matter contents of these galaxies. Using Spitzer Space Telescope 3.6 and 4.5 micron imaging, we have measured the flux of each galaxy. In conjunction with distances derived from Hubble Space Telescope imaging, we have determined the stellar mass and its distribution as a function of radius for ten of the twelve systems.

Cannon, John M.; Marshall, M.; Cave, I.; Larson, E.; Moody, S.; Adams, E. A.; Dolphin, A. E.; Elson, E. C.; Giovanelli, R.; Haynes, M. P.; McQuinn, K. B.; Ott, J.; Saintonge, A.; Salzer, J. J.; Skillman, E. D.

2013-01-01

447

Concerning the system earth during geomagnetic polarity transitions: Impact on the neutral atmosphere  

Microsoft Academic Search

During a geomagnetic polarity transition, the strength and structure of the earth geomagnetic field can vary very much from the current state. This means that regions which are at the moment shielded from extraterrestrical energetic particles can become subject to particle precipition. We use a 2 dimensional chemistry, photolysis and transport model of the atmosphere to investigate how different configurations

M. von Koenig; J. Burrows; K. Kuenzi; E. Wolff; M. Kallenrode

2003-01-01

448

Hydrogeologic Controls on the Deep Terrestrial Biosphere - Chemolithotrophic Energy for Subsurface Life on Earth and Mars  

Microsoft Academic Search

As exploration for gold, diamonds and base metals expand mine workings to depths of almost 3 km below the Earth's surface, the mines of the Canadian Shield provide a window into the deep biosphere as diverse, but to date less well-explored than the South African Gold Mines. To date investigations of the deep biosphere have, in most cases, focused on

B. Sherwood Lollar; J. Moran; S. Tille; K. Voglesonger; G. Lacrampe-Couloume; T. Onstott; L. Pratt; G. Slater

2009-01-01

449

Formulas Giving Buildup Factor for Double-Layered Shields  

Microsoft Academic Search

Formulas that give absorbed dose buildup factors for two-layered shields have been developed based on gamma-ray absorption buildup factors computed with the Monte Carlo Neutral Particle Transport Code System (MCNP). The shielding materials considered were water, lead, steel, concrete, and some of their combinations for two-layered shields with thicknesses between 1 to 10 mfp. Gamma energy considered ranged from 0.5

Mevlut Guvendik; Nicholas Tsoulfanidis

2000-01-01

450

An Improved Model of Loads Acting on Shield  

Microsoft Academic Search

Shield tunneling technologies have been developed for constructing tunnels in soft ground especially with groundwater. However,\\u000a the automatic deviation correction systems are based on empirical relationships or theoretical model including a great deal\\u000a of unknown parameters. In this paper, the shield-segment system is considered as underground parallel manipulators, so the\\u000a shield behavior can be represented by the rotation of motion

Xiangtao Hu; Zhouping Yin; Yongan Huang

2009-01-01

451

Fast neutron shielding and neutron transport studies at YAYOI  

Microsoft Academic Search

The fast neutron shielding experiments at the fast neutron source reactor YAYOI of the University of Tokyo were summarized. The experiments were grouped into the following four types; 1.(1)|experiments for shield design of fast breeder reactor,2.(2)|fast neutron transmission experiments,3.(3)|fast neutron streaming experiments,4.(4)|neutron skyshine experiment. The experimental data are useful for shield design and assessing the accuracy of the calculational methods.The

Y. Oka; K. Furuta; S. An

1998-01-01

452

Polyethylene/Boron Composites for Radiation Shielding Applications  

SciTech Connect

Multifunctional composites made with boron are absorbers of low energy nuetrons, and could be used for structural shielding materials. Polyethylene/boron carbide composites were fabricated using conventional polymer processing techniques, and were evaluated for mechanical and radiation shielding properties. Addition of neat boron carbide (powder and nanoparticles) to an injection molding grade HPDE showed superior mechanical properties compared to neat HDPE. Radiation shielding measurements of a 2 wt% boron carbide composite were improved over those of the neat polyethylene.

Harrison, Courtney; Grulke, Eric [Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506 (United States); Burgett, Eric; Hertel, Nolan [Neely Nuclear Research Center, Georgia Institute of Technology, Atlanta, GA 30332 (United States)

2008-01-21

453

31P NMR chemical shielding tensor of 2-aminoethylphosphonic acid  

Microsoft Academic Search

The symmetric part of the 31P NMR chemical shielding tensor was determined in a single crystal of 2-aminoethylphosphonic acid (AEP). The principal values, relative to 85% H3PO4, are ?11=87.1, ?22=15.6, and ?33=?47.5 ppm. Four orientations of the chemical shielding tensor on the molecule are possible, but only one of them shows correlation with the bond directions. The two most shielded

Marie-Rose Van Calsteren; George I. Birnbaum; Ian C. P. Smith

1987-01-01

454

BrowserShield: Vulnerability-driven filtering of dynamic HTML  

Microsoft Academic Search

Abstract Vulnerability-driven filtering of network data can offer a fast and easy-to-deploy alternative or intermediary to software patching, as exemplified in Shield [43]. In this paper, we take Shield’s vision to a new domain, inspect- ing and cleansing not just static content, but also dy- namic,content. The dynamic,content we target is the dynamic HTML in web pages, which have become

Charles Reis; John Dunagan; Helen J. Wang; Opher Dubrovsky; Saher Esmeir

2007-01-01

455

Major uncertainties influencing entry probe heat shield design  

NASA Technical Reports Server (NTRS)

Factors influencing the design of an outer planet probe heat shield are discussed. Major factors included are: uncertainties in composition and scale height of the planet atmospheres; the augmentation/attenuation of entry heating by ablation products requires more computer study and testing; carbon heat shields, especially carbon phenolic, possessing improved resistance to spallation need developing; and white silica reflecting heat shields with improved resistance to bulk vitrification need further developing.

Congdon, W.

1974-01-01

456

Hypervelocity impact simulation for micrometeorite and debris shield design  

NASA Technical Reports Server (NTRS)

A new capability has been developed for direct computer simulation of hypervelocity impacts on multi-plate orbital debris shields, for combinations of low shield thickness and wide shield spacing which place extreme demands on conventional Eulerian analysis techniques. The modeling methodology represents a novel approach to debris cloud dynamics simulation, a problem of long term interest in the design of space structures. Software implementation of the modeling methodology provides a new design tool for engineering analysis of proposed orbital debris protection systems.

Fahrenthold, Eric P.

1992-01-01

457

SHIELDING OF A FAST BREEDER REACTOR--I. THE PRIMARY SHIELD  

Microsoft Academic Search

The differing shieldmg requirements of a fast breeder reactor and a ; thermal reactor are discussed. The functions of a stainless steel layer inside ; the reactor vessel of a fast breeder are outlined: neutron reflector, gamma-ray ; absorbing thermal shield, and an inelastic neutron scatterer to protect the ; vessel walls against radiation damage. The use of borated graphite

Hungerford

1957-01-01

458

Earth on the Move.  

ERIC Educational Resources Information Center

Provides background information on the layers of the earth, the relationship between changes on the surface of the earth and its insides, and plate tectonics. Teaching activities are included, with some containing reproducible worksheets and handouts to accompany them. (TW)

Naturescope, 1987

1987-01-01

459

Effective shielding to measure beam current from an ion source.  

PubMed

To avoid saturation, beam current transformers must be shielded from solenoid, quad, and RFQ high stray fields. Good understanding of field distribution, shielding materials, and techniques is required. Space availability imposes compact