Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Nuclear Structure”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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

At least 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Track Structure and the Biological Effectiveness of Accelerated Particles for the Induction of Chromosome Damage

Track structure models predict that at a fixed value of LET, particles with lower charge number, Z will have a higher biological effectiveness compared to particles with a higher Z. In this report we investigated how track structure effects induction of chromosomal aberration in human cells. Human lymphocytes were irradiated in vitro with various energies of accelerated iron, silicon, neon, or titanium ions and chromosome damage was assessed in using three color FISH chromosome painting in chemically induced PCC samples collected a first cell division post irradiation. The LET values for these ions ranged from 30 to195 keV/micron. Of the particles studied, Neon ions have the highest biological effectiveness for induction of total chromosome damage, which is consistent with track structure model predictions. For complex-type exchanges 64 MeV/ u Neon and 450 MeV/u Iron were equally effective and induced the most complex damage. In addition we present data on chromosomes exchanges induced by six different energies of protons (5 MeV/u to 2.5 GeV/u). The linear dose response term was similar for all energies of protons suggesting that the effect of the higher LET at low proton energies is balanced by the production of nuclear secondaries from the high energy protons.

George, K.↗
NASA NTRS2012

The Biological Effectiveness of Accelerated Particles for the Induction of Chromosome Damage: Track Structure Effects and Cytogenetic Signatures of High-LET Exposure

Track structure models predict that at a fixed value of LET, particles with lower charge number, Z will have a higher biological effectiveness compared to particles with a higher Z. In this report we investigated how track structure effects induction of chromosomal aberration in human cells. Human lymphocytes were irradiated in vitro with various energies of accelerated iron, silicon, neon, or titanium ions and chromosome damage was assessed in using three color FISH chromosome painting in chemically induced PCC samples collected a first cell division post irradiation. The LET values for these ions ranged from 30 to 195 keV/micrometers. Of the particles studied, Neon ions have the highest biological effectiveness for induction of total chromosome damage, which is consistent with track structure model predictions. For complex-type exchanges 64 MeV/ u Neon and 450 MeV/u Iron were equally effective and induced the most complex damage. In addition we present data on chromosomes exchanges induced by six different energies of protons (5 MeV/u to 2.5 GeV/u). The linear dose response term was similar for all energies of protons suggesting that the effect of the higher LET at low proton energies is balanced by the production of nuclear secondaries from the high energy protons. All energies of protons have a much higher percentage of complex-type chromosome exchanges than gamma rays, signifying a cytogenetic signature for proton exposures.

George, K.↗
NASA NTRS1979

To the solar foci

Earlier authors showed that the sun is likely to act as a lens for gravitational radiation, with focui in the outer solar system. They suggested that missions to these foci have the potential of directly measuring the density structure of the sun. Other applications include gravitational wave astronomy and tests of general relativity. This idea is reexamined, concentrating on the engineering aspects of focal missions; primarily spacecraft design and performance. Other topics studied include solar optics, gravitational wave detectors, navigation, and the design of missions for different purposes. Specifically, it is shown that shuttle launched chemical rockets have a substantial capability for reaching some foci; and that all can be reached with large payloads using nuclear isotope-electric propulsion.

Sonnabend, D.↗
NASA NTRS1981

Unpulsed X-rays from pulsars

Preliminary results of several programs to detect thermal X-ray emission from isolated neutron stars are presented. Results of Einstein pulsar surveys indicate that either the majority of supernovas which leave remnants do not produce neutron stars, or the cooling calculations are in need of substantial revision. When appropriate relativistic thermodynamics and updated high energy nuclear physics are included, the new calculations predict significantly lower temperatures for standard neutron star equations of state. X-ray results give strong evidence that five of the seven historical remnants and a large majority of the other remnants of less than 1000 yr do not contain radio pulsars. A survey of known radio pulsars is also presented, which is designed to test the heating mechanisms required by various theories of pulsar emission and neutron star structure, and consists of a survey of all known pulsars within 300 pc.

Helfand, D. J.↗
NASA NTRS1984

Results of the Purdue University GAS-1 payload

The Purdue University GAS-1 payload was flown on STS-7. Results of the three experiments included in the payload are summarized. The experiments conducted were: (1) the detection of nuclear particles in near-Earth space environment, (2) an investigation of the effect of microgravity on the germination of sunflower seeds, and (3) an examination of the motion of mercury under low gravity conditions. Results of the payload experiments are discussed from an engineering design standpoint. Data were obtained from one of the experiments, but electrical and mechanical malfunctions prevented the operation of the other two. The thermal control design maintained the desired temperatures and the structure successfully supported all components. The microprocessor collected and stored temperature readings and other data during the flight. A series of recommendations based on these results are included herein.

Perez, R.↗
NASA NTRS2005

The Spaceflight Revolution Revisited

This essay will first consider whether technological breakthroughs in space technology and the rational motives of ordinary institutions have the capacity to break out of this relatively static situation. Then we will survey the roles that social movements of various kinds might play and conclude with an examination of one particular nascent movement that might possibly build the foundation for a spacefaring civilization. A third of a century ago, practical nuclear fission rockets were under development, but this approach now seems environmentally unacceptable. It is hard to devise a more environmentally benign propellant than the hydrogen and oxygen used by the main engines of the Space Shuttle. There is some hope that nanotechnology will save the day with materials based on carbon nanotubes that are vastly stronger yet lighter than metals.6 However, the X-33 failure shows that it is not easy to work with radically new structural materials in demanding aerospace applications, and we may be many decades away from being able to manufacture propellant tanks, wings, and other large structures from carbon nanotubes. Satellites in low-Earth and synchronous orbit are of great importance in the collection and distribution of information, thus essential to the information economy. The wide range of civilian applications includes telephone, data transmission, television, navigation, weather observation, agriculture monitoring, and prospecting for natural resources.8 The technology is largely perfected, and incremental progress can be achieved by improvement in information systems and simply by investing in more relatively small satellites of the kinds we already have.

Bainbridge, William Sims↗
NASA NTRS2012

NARloy-Z-Carbon Nanotube Composites

Motivation: (1) NARloy-Z (Cu-3%Ag-0.5%Zr) is the state of the art, high thermal conductivity structural alloy used for making liquid rocket engine main combustion chamber liner. It has a Thermal conductivity approx 80% of pure copper. (2) Improving the thermal conductivity of NARloy-Z will help to improve the heat transfer efficiency of combustion chamber. (3)Will also help to reduce the propulsion system mass and increase performance. It will also increases thrust to weight ratio. (4) Improving heat transfer helps to design and build better thermal management systems for nuclear propulsion and other applications. Can Carbon nanotubes (CNT) help to improve the thermal conductivity (TC)of NARloy-Z? (1)CNT's have TC of approx 20X that of copper (2) 5vol% CNT could potentially double the TC of NARloy-Z if properly aligned (3) Improvement will be less if CNT s are randomly distributed, provided there is a good thermal bond between CNT and matrix. Prior research has shown poor results (1) No TC improvement in the copper-CNT composite reported (2)Reported values are typically lower (3) Attributed to high contact thermal resistance between CNT and Cu matrix (4)Results suggest that a bonding material between CNT and copper matrix is required to lower the contact thermal resistance It is hypothesized that Zr in NARloy-Z could act as a bonding agent to lower the contact thermal resistance between CNT and matrix.

Bhat, Biliyar N.↗
NASA NTRS2005

Nuclear Radiation Fields on the Mars Surface: Risk Analysis for Long-term Living Environment

Mars, our nearest planet outward from the sun, has been targeted for several decades as a prospective site for expanded human habitation. Background space radiation exposures on Mars are expected to be orders of magnitude higher than on Earth. Recent risk analysis procedures based on detailed dosimetric techniques applicable to sensitive human organs have been developed along with experimental data regarding cell mutation rates resulting from exposures to a broad range of particle types and energy spectra. In this context, simulated exposure and subsequent risk for humans in residence on Mars are examined. A conceptual habitat structure, CAD-modeled with duly considered inherent shielding properties, has been implemented. Body self-shielding is evaluated using NASA standard computerized male and female models. The background environment is taken to consist not only of exposure from incident cosmic ray ions and their secondaries, but also include the contribution from secondary neutron fields produced in the tenuous atmosphere and the underlying regolith.

Brooke M Anderson↗
NASA NTRS1991

Origins of the 12-200 micron flux in NGC 6946 - Starlight and continuum dust emission from AN Sc galaxy

Infrared maps and optical CCD images of NGC 6946, a nearly face-on spiral with evidence of active star formation, are presented. Consideration is given, at 1-3 kpc spatial scales, to the relationship of the infrared continuum to spiral and radial structure, tracers of the interstellar medium, and ionizing and nonionizing sources of stellar radiation. Two infrared components were revealed - one with surface brightnesses of 20-60 Jy per 45 arcsec aperture at 160 microns, and the other with a surface brightness of less than 20 Jy. Various continuum distributions show discrete sources coinciding with giant H II regions superposed on a smooth unresolved disk background which decreases exponentially with the radius. The optical and spectral properties of the nuclear source and the disk are described. Dust properties and heating conditions, and far-infrared emitting phases are discussed.

Engargiola, G.↗
NASA NTRS1975

Nuclear emulsion measurements of the astronauts' radiation exposures on Skylab missions 2, 3, and 4

On the Skylab missions, Ilford G.5 and K.2 emulsions were flown as part of passive dosimeter packs carried by the astronauts on their wrists. Due to the long mission times, latent image fading and track crowing imposed limitations on a quantitative track and grain count analysis. For Skylab 2, the complete proton energy spectrum was determined within reasonable error limits. A combined mission dose equivalent of 2,490 millirems from protons, tissue stars and neutrons was measured on Skylab 2. A stationary emulsion stack, kept in a film vault drawer on the same mission, displayed a highly structured directional distribution of the fluence of low-energy protons (enders) reflecting the local shield distribution. On the 59 and 84-day mission 3 and 4, G.5 emulsions had to be cut on the microtom to 5-7 microns for microscopic examination. Even so, the short track segments in such thin layers precluded a statistically reliable grain count analysis. However, the K.2 emulsions still allowed accurate proton ender counts without special provisions.

Schaefer, H. J.↗
NASA NTRS1995

Preliminary Design of a SP-100/Stirling Radiatively Coupled Heat Exchanger

Several methods for coupling the SP-100 space nuclear reactor to the NASA Lewis Research Center's Free Piston Stirling Power Convertor (FPSPC) are presented. A 25 kWe, dual opposed Stirling convertor configuration is used in these designs. The concepts use radiative coupling between the SP-100 lithium loop and the sodium heat pipe of the Stirling convertor to transfer the heat from the reactor to the convertor. Four separate configurations are presented. Masses for the four designs vary from 41 to 176 kgs. Each design's structure, heat transfer characteristics, and heat pipe performance are analytically modeled.

Schmitz, Paul↗
NASA NTRS1999

How cells (might) sense microgravity

This article is a summary of a lecture presented at an ESA/NASA Workshop on Cell and Molecular Biology Research in Space that convened in Leuven, Belgium, in June 1998. Recent studies are reviewed which suggest that cells may sense mechanical stresses, including those due to gravity, through changes in the balance of forces that are transmitted across transmembrane adhesion receptors that link the cytoskeleton to the extracellular matrix and to other cells (e.g., integrins, cadherins, selectins). The mechanism by which these mechanical signals are transduced and converted into a biochemical response appears to be based, in part, on the finding that living cells use a tension-dependent form of architecture, known as tensegrity, to organize and stabilize their cytoskeleton. Because of tensegrity, the cellular response to stress differs depending on the level of pre-stress (pre-existing tension) in the cytoskeleton and it involves all three cytoskeletal filament systems as well as nuclear scaffolds. Recent studies confirm that alterations in the cellular force balance can influence intracellular biochemistry within focal adhesion complexes that form at the site of integrin binding as well as gene expression in the nucleus. These results suggest that gravity sensation may not result from direct activation of any single gravioreceptor molecule. Instead, gravitational forces may be experienced by individual cells in the living organism as a result of stress-dependent changes in cell, tissue, or organ structure that, in turn, alter extracellular matrix mechanics, cell shape, cytoskeletal organization, or internal pre-stress in the cell-tissue matrix.--Ingber, D. How cells (might) sense microgravity.

NASA Discipline Cell Biology↗
NASA NTRS1973

Nuclear characteristics of a fissioning uranium plasma test reactor with light-water cooling

An analytical study was performed to determine a design configuration for a cavity test reactor. Test section criteria were that an average flux of 10 to the 15th power neutrons/sq cm/sec (E less than or equal to 0.12 eV) be supplied to a 61-cm-diameter spherical cavity at 200-atm pressure. Design objectives were to minimize required driver power, to use existing fuel-element technology, and to obtain fuel-element life of 10 to 100 full-power hours. Parameter calculations were made on moderator region size and material, driver fuel arrangement, control system, and structure in order to determine a feasible configuration. Although not optimized, a configuration was selected which would meet design criteria. The driver fuel region was a cylindrical annular region, one element thick, of 33 MTR-type H2O-cooled elements (Al-U fuel plate configuration), each 101 cm long. The region between the spherical test cavity and the cylindrical driver fuel region was Be (10 vol. % H2O coolant) with a midplane dimension of 8 cm. Exterior to the driver fuel, the 25-cm-thick cylindrical and axial reflectors were also Be with 10 vol. % H2O coolant. The entire reactor was contained in a 10-cm-thick steel pressure vessel, and the 200-atm cavity pressure was equalized throughout the driver reactor. Fuel-element life was 50 hr at the required driver power of 200 MW. Reactor control would be achieved with rotating poison drums located in the cylindrical reflector region. A control range of about 18 percent delta k/k was required for reactor operation.

Whitmarsh, C. L., Jr.↗
NASA NTRS1999

Solar Stirling for Deep Space Applications

A study was performed to quantify the performance of solar thermal power systems for deep space planetary missions. The study incorporated projected advances in solar concentrator and energy conversion technologies. These technologies included inflatable structures, lightweight primary concentrators, high efficiency secondary concentrators, and high efficiency Stirling convertors. Analyses were performed to determine the mass and deployed area of multi-hundred watt solar thermal power systems for missions out to 40 astronomical units. Emphasis was given to system optimization, parametric sensitivity analyses, and concentrator configuration comparisons. The results indicated that solar thermal power systems are a competitive alternative to radioisotope systems out to 10 astronomical units without the cost or safety implications associated with nuclear sources.

Mason, Lee S.↗
NASA NTRS1976

Physical processes in comets

The paper discusses physical processes in comets which involve solar and nuclear radial forces that affect the motions of gases and icy grains, gas-phase chemistry very close to the nuclei of large comets near the sun, sublimation of icy grains, dissociation of parent molecules into radicals and of radicals into atoms, and ionization by sunlight and collisions. The composition and dimensions of nuclei are examined along with variations in intrinsic brightness, the nature of volatiles, gas production rates in the coma, characteristics of icy grains in the coma, and the structure of streamers, ion tails, and dust tails. The structure of the coma is described in detail on the basis of spectroscopic observations of several comets. The origin of comets is briefly reviewed together with the relation of comets to earth, the interplanetary complex, and the interstellar medium. Desirable future observations are noted, especially by space missions to comets.

Whipple, F. L.↗
NASA NTRS1994

Near-infrared continuum and 3.3 micrometer(s) polycyclic aromatic hydrocarbon imaging of the starburst ring in the type 1 Seyfert galaxy NGC 7469

High resolution near-infrared images of the type 1 Seyfert galaxy NGC 7469 have been obtained to probe its dusty nuclear environment. Direct J, H, and K images are relatively featureless, but residual images created by subtracting a smooth model based on best-fitting elliptical isophotes reveal a tight inner spiral whose high surface-brightness portions correspond to a previously detected 3 sec (1 kpc) diameter ring of radio continuum emission. The inner infrared spiral arms extended approximately equal to 4 sec NW and SE from the nucleus, and the NW arm joins up with large-scale spiral structure visible in the R band. The residual images also show a bar-like structure aligned with the brightest infrared/radio hotspots at PA approximately equal to 50 deg. Three infrared hotspots are detected which align remarkably well with 6 cm radio continuum sources. The near-infrared ring and the hotspots are visible in the residual images, and in a high-resolution direct K-band image restored to an effective resolution of 0.65 sec (FWHM) using the Richardson-Lucy algorithm. The infrared hotspots have luminosities of nuL(sub nu) (2.2 micrometer(s)) approximately equal to 10(exp 8) solar luminosity (M(sub k) approximately equal to -16 mag), suggesting they are either giant H II regions or individual supernovae. The two brightest regions may be associated with enhanced star formation triggered by orbit crowding of gas where spiral arms emerge from an inner bar. Narrowband (delta lambda/lambda approximately 1.5%) imaging in the 3.28 micrometer(s) dust emission feature and surrounding continuum confirms the 3 sec diameter 3.28 micrometer(s) emission region detected previously using multiaperture photometry. The extended polycyclic aromatic hydrocarbon (PAH) emission is slightly elongated and aligned with published 1O III1 line emission and 12.5 micrometer(s) continuum emission, apparently tracing the starburst. The presence of approximately equal to 25% of the total 3.28 micrometer(s) PAH emission within R less than 1 sec demonstrates that a starburst within the central few hundred parsecs must supply a significant fraction of the infrared continuum from the nucleus, and there is apparently sufficient shielding material between the starburst and the active galactic nucleus (AGN) to preserve the PAHs along our line of sight to the nucleus.

Mazzarella, J. M.↗
NASA NTRS1992

The alpha-process and the r-process

The paper explores the alpha-rich freeze-out for values of neutron excesses larger than previously treated, and reports the discovery of nuclear systematics that, for neutron excesses greater than about 0.05, allow the creation of heavier elements all the way up to A of about 100, even when most of the ejecta is in the form of heavy elements. It is found that a large part of the nuclear flow in the r-process may be carried by charged particle reactions up to about A of about 100. It is speculated that the site of these processes is the high-entropy 'wind' of a young neutron star in which neutrino energy deposition is driving mass loss. The pass of r-process ejected per supernova is expected to be about 0.0001 solar mass per Type II or Ib supernova, but this is sensitive to details of the presupernova structure, the explosion mechanism, and the amount of material that falls back onto the neutron star when the reverse shock arrives there.

Woosley, S. E.↗
NASA NTRS1996

Second International Airborne Remote Sensing Conference and Exhibition

The conference provided four days of displays and scientific presentations on applications, technology, a science of sub-orbital data gathering and analysis. The twelve displayed aircraft equipped with sophisticated instrumentation represented a wide range of environmental and reconnaissance missions,including marine pollution control, fire detection, Open Skies Treaty verification, thermal mapping, hydrographical measurements, military research, ecological and agricultural observations, geophysical research, atmospheric and meterological observations, and aerial photography. The U.S. Air Force and the On-Site Inspection Agency displayed the new Open Skies Treaty verification Boeing OC 135B that promotes international monitoring of military forces and activities. SRl's Jetstream uses foliage and ground penetrating SAR for forest inventories, toxic waste delineation, and concealed target and buried unexploded ordnance detection. Earth Search Sciences's Gulfstream 1 with prototype miniaturized airborne hyperspectral imaging equipment specializes in accurate mineral differentiation, low-cost hydrocarbon exploration, and nonproliferation applications. John E. Chance and the U.S. Army Corps of Engineers displayed the Bell 2 helicopter with SHOALS that performs hydrographic surveying of navigation projects, coastal environment assessment, and nautical charting surveys. Bechtel Nevada and U.S. DOE displayed both the Beech King AIR B-200 platform equipped to provide first response to nuclear accidents and routine environmental surveillance, and the MBB BO-105 helicopter used in spectral analysis for environmental assessment and military appraisal. NASA Ames Research Center's high-altitude Lockheed ER-2 assists in earth resources monitoring research in atmospheric chemistry, oceanography, and electronic sensors; ozone and greenhouse studies and satellite calibration and data validation. Ames also showcased the Learjet 24 Airborne Observatory that completed missions in Venus cloud cover analysis, Quadantid meteor shower studies, extra-solar far infrared ionic structure lines measurement, Cape Kennedy launch support, and studies in air pollution, The Products and Services Exhibit showcased new sensor and image processing technologies, aircraft data collection services, unmanned vehicle technology, platform equipment, turn-key services, software a workstations, GPS services, publications, and processing and integration systems by 58 exhibitors. The participation of aircraft users and crews provided unique dialogue between those who plan data collection a operate the remote sensing technology, and those who supply the data processing and integration equipment. Research results using hyperspectral imagery, radar and optical sensors, lidar, digital aerial photography, a integrated systems were presented. Major research and development programs and campaigns we reviewed, including CNR's LARA Project and European Space Agency's 1991-1995 Airborne Campaign. The pre-conference short courses addressed airborne video, photogrammetry, hyperspectral data analysis, digital orthophotography, imagery and GIS integration, IFSAR, GPS, and spectrometer calibration.

Source record↗