SEARCH · Engineering Papers

Results for “Long-Lived”

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.

SourceResearch connectionFrom yearThrough year

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

At least 199 records · Page 11

All sources NASA NTRS DOE OSTI

NASA NTRS1987

Drilling Holes in Graphite/Epoxy

Relatively long-lived bit produces high-quality holes. Effective combination of cutting-tool design, feed, and speed determined for drilling 3/16-and-1/4-in. (0.48-and 0.65-cm) diameter holes in 0.18 in. (0.46cm) thick GM3013A or equivalent graphite/epoxy corrugated spar without backup material and without coolant. Developed to produce holes in blind areas, optimal techniques yielded holes of high quality, with minimal or acceptable delamination and/or fiber extension on drill-exit side.

Minlionica, Ronald↗

NASA NTRS1986

Advanced solar dynamic space power systems perspectives, requirements and technology needs

Projected NASA, Civil, Commercial, and Military missions will require space power systems of increased versatility and power levels. The Advanced Solar Dynamic (ASD) Power systems offer the potential for efficient, lightweight, survivable, relatively compact, long-lived space power systems applicable to a wide range of power levels (3 to 300 kWe), and a wide variety of orbits. The successful development of these systems could satisfy the power needs for a wide variety of these projected missions. Thus, the NASA Lewis Research Center has embarked upon an aggressive ASD reserach project under the direction of NASA's Office of Aeronautics and Space Technology (DAST). The project is being implemented through a combination of in-house and contracted efforts. Key elements of this project are missions analysis to determine the power systems requirements, systems analysis to identify the most attractive ASD power systems to meet these requirements, and to guide the technology development efforts, and technology development of key components.

Dustin, M. O.↗

NASA NTRS1987

SP-100 Advanced Technology Program

The goal of the triagency SP-100 Program is to develop long-lived, compact, lightweight, survivable nuclear reactor space power systems for application to the power range 50 kWe to 1 MWe. The successful development of these systems should enable or significantly enhance many of the future NASA civil and commercial missions. The NASA SP-100 Advanced Technology Program strongly augments the parallel SP-100 Ground Engineering System Development program and enhances the chances for success of the overall SP-100 program. The purpose of this paper is to discuss the key technical elements of the Advanced Technology Program and the progress made in the initial year and a half of the project.

Sovie, Ronald J.↗

NASA NTRS1986

The sun and the heliosphere in three dimensions; Proceedings of the Nineteenth ESLAB Symposium, Les Diablerets, Switzerland, June 4-6, 1985

Papers are presented on coronal magnetic fields, the heliospheric energy source, stereoscopic measurement of hard solar X-rays, and OVI diagnostics of solar-wind generation. Also considered are coronal transients at high heliospheric latitudes, the solar-cycle dependence of coronal mass ejections, comets and three-dimensional wind structure, and interplanetary scintillation observations of the solar wind at high latitudes. Other topics include three-dimensional coronal and heliospheric structure from radio observations, multispacecraft observations of Type III radio bursts, the acceleration of energetic particles at solar-wind shocks, and a spatially confined, long-lived stream of solar particles.

Marsden, R. G.↗

NASA NTRS1984

The potential impact of new power system technology on the design of a manned Space Station

Larger, more complex spacecraft of the future such as a manned Space Station will require electric power systems of 100 kW and more, orders of magnitude greater than the present state of the art. Power systems at this level will have a significant impact on the spacecraft design. Historically, long-lived spacecraft have relied on silicon solar cell arrays, a nickel-cadmium storage battery and operation at 28 V dc. These technologies lead to large array areas and heavy batteries for a Space Station application. This, in turn, presents orbit altitude maintenance, attitude control, energy management and launch weight and volume constraints. Size (area) and weight of such a power system can be reduced if new higher efficiency conversion and lighter weight storage technologies are used. Several promising technology options including concentrator solar photovoltaic arrays, solar thermal dynamic and ultimately nuclear dynamic systems to reduce area are discussed. Also, higher energy storage systems such as nickel-hydrogen and the regenerative fuel cell (RFC) and higher voltage power distribution which add system flexibility, simplicity and reduce weight are examined. Emphasis placed on the attributes and development status of emerging technologies that are sufficiently developed so that they could be available for flight use in the early to mid 1990's.

Fordyce, J. S.↗

NASA NTRS1986

A reflection grating spectrometer for the X-ray Multi-Mirror (XMM) space observatory - Design and calculated performance

Attention is given to a spectrometer design candidate for the X-ray Multi-Mirror observatory, being planned by the European Space Agency as a long-lived large-area array of telescopes. The science requirement of moderate resolution spectroscopy in a two octave region with extremely high throughput leads to the use of grazing incidence reflection gratings. It is noted that the sensitivity of the instrument is sufficient to permit the first spectral detection of soft X-ray features in external galaxies.

Hettrick, Michael C.↗

NASA NTRS1986

Simulations of the gross solar magnetic field during sunspot cycle 21

Regarding new bipolar magnetic regions as sources of flux, the evolution of the radial component of the solar photospheric magnetic field during 1976-1984 has been simulated with a spatial resolution of about 34,000 km, and the corresponding evolution of its absolute value averaged over the visible disk is derived. For nominal values of the transport parameters, this simulated gross field is in close, though imperfect, agreement with the observed gross field and its associated indices of solar activity. By analyzing the response of the simulated gross field to variations in the transport parameters and the source properties, it is found that the simulated field originates in newly erupted bipolar regions. The lifetimes of these regions are almost always less than three mo. Consequently, the strength of the simulated gross field is a measure of the current level of solar activity, and any recurrent patterns with lifetimes in excess of six mo must reflect the continuing eruption of new flux at 'active longitudes' rather than the persistence of old flux in long-lived magnetic structures.

Sheeley, Neil R., Jr.↗

NASA NTRS1987

Atmospheric dynamics

The paper presents an overview of U.S. contributions in the period of 1983-1986, to the analysis and study of the atmosphere's motion and of the role of this motion in the thermodynamics and chemistry of the atmosphere. Special attention is given to the linear and quasi-linear studies of the dynamics of atmospheric disturbances; studies of the wave breaking phenomenon; and investigations of various long-lived features, ranging from climatological stationary waves to long-period oscillations in the tropics. Consideration is also given to diagnostics for the interactions among disturbances and the mean flow, nontraditional approaches to instability and disturbance growth, and dynamical systems and multiple equilibria.

Lindzen, Richard S.↗

NASA NTRS1987

Atmospheric distribution of Kr-85 simulated with a general circulation model

A three-dimensional chemical tracer model for the troposphere is used to simulate the global distribution of Kr-85, a long-lived radioisotope released at northern midlatitudes by nuclear industry. Simulated distributions for the period 1980-1983 are in excellent agreement with data from six latitudinal profiles measured over the Atlantic. High concentrations of Kr-85 are predicted over the Arctic in winter, advected from European sources, and somewhat smaller enhancements arising from the same sources are predicted over the tropical Atlantic in summer. Latitudinal gradients are steepest in the northern tropics, with distinctly different seasonal variations over the Pacific, as compared to the Atlantic. The global inventory of Kr-85 is reconstructed for the period 1980-1983 by combining the concentrations measured over the Atlantic with the global distributions predicted by the model. The magnitude of the Soviet source is derived. The interhemispheric exchange time is calculated as 1.1 years, with little seasonal dependence.

Jacob, Daniel J.↗

NASA NTRS1987

Antiferromagnetism of La2CuO(4-y) studied by muon-spin rotation

Zero-field spin precession of positive muons has been observed in the antiferromagnetic state of La2CuO(4-y). Sharp onsets of the sublattice magnetization are found at temperatures close to those of the susceptibility maxima of different specimens. The long-lived precession signal indicates a microscopically homogeneous distribution of spin density at each Cu atom below the Neel temperature. A combination of the present results and neutron-scattering studies indicates the ordered moment per Cu atom to be significantly less than 1 mu(B).

Uemura, Y. J.↗

NASA NTRS1987

An overview of STIP interval 18: September 1985, the G-Z encounter

The primary period of interest during September 1985 is the few days surrounding the ICE encounter with comet Giacobini-Zinner(G-Z) which occurred at 1102 UT on 11 September. To place into perspective the actual in situ observations measured during the comet encounter it is necessary to understand the prevailing solar and interplanetary conditions. Starting two solar rotations prior to and extending through the rotation after the encounter the interplanetary stream structure was very uniform, similar to the 1973-4 long-lived structure. Prior to the arrival of the corotating high-speed stream at 5 UT on 11 September, ICE was already measuring the effects of G-Z on the surrounding interplanetary medium. An overview of available solar, interplanetary, and ICE data for the cometary interval is presented.

Zwickl, R. D.↗

NASA NTRS1988

Evidence of the in situ decay of Al-26 in a Semarkona chondrule

A long-standing problem in the study of meteorites, with broad implications for the evolution of the solar system, is the source of heat for melting small planets. Meteorites, such as the eucrites, were obviously the result of a melting process on a small planet, yet the decay of the long-lived radionuclides present on the earth, K-40, U-235, U-238, and Th-232, could not have provided nearly enough heat to initiate melting approximately 4.5 aeons ago, even on bodies 1000 km in diameter. This problem addressed by H.C. Urey in 1955, who recognized that the presence of short-lived (and now extinct) radionuclides such as Al-26 (half-life of approximately 720,000 y) in the early solar system would have provided an abundant heat source for melting small asteroid-size bodies. Since any Al-26 initially present in the solar nebula would have completely decayed after only a few tens of millions of years, the problem became one of finding evidence of Al-26, in the form of excess Mg-26, in meteorites. The search for evidence of the Al-26 is briefly examined.

Hutcheon, I. D.↗

NASA NTRS1987

SP-100 Advanced Technology Program

Sovie, Ronald J.↗

NASA NTRS1987

Sensitivity studies and a simple ozone perturbation experiment with a truncated two-dimensional model of the stratosphere

The 1-1/2-D model of Holton (1986), which is actually a highly truncated two-dimensional model, describes latitudinal variations of tracer mixing ratios in terms of their projections onto second-order Legendre polynomials. The present study extends the work of Holton by including tracers with photochemical production in the stratosphere (O3 and NOy). It also includes latitudinal variations in the photochemical sources and sinks, improving slightly the calculated global mean profiles for the long-lived tracers studied by Holton and improving substantially the latitudinal behavior of ozone. Sensitivity tests of the dynamical parameters in the model are performed, showing that the response of the model to changes in vertical residual meridional winds and horizontal diffusion coefficients is similar to that of a full two-dimensional model. A simple ozone perturbation experiment shows the model's ability to reproduce large-scale latitudinal variations in total ozone column depletions as well as ozone changes in the chemically controlled upper stratosphere.

Stordal, Frode↗

NASA NTRS1987

Secular cooling of the earth as a source of intraplate stress

As a result of secular cooling and contraction of the earth, an increasingly extensional horizontal stress is imposed on the central portions of the plates. While the rate of increase of this stress is small in most situations, it is enhanced for large plates and during any episodes of accelerated global cooling. This source of stress may have contributed to the rifting and breakup of long-lived supercontinental plates.

Solomon, Sean C.↗

NASA NTRS1987

Trace constituents in the mesosphere

The paper examines recent composition measurements, the large-scale distributions of trace constituents, and the interpretation of these global patterns in the light of the current understanding of chemistry and transport. Attention is given to results from the following space missions: the Nimbus 7 LIMS and SAMS experiments; the SMM UV spectrometer solar occultation experiment; the SME UVS and AGS experiments; and the Spacelab 1 solar occultation experiment. A brief summary of measurements and their implications is presented for three long-lived species, CO, NO, and H2O. The reactive or short-lived species OH and O3 are also examined.

Thomas, Gary E.↗

NASA NTRS1988

Space science at NASA - Retrospect and prospect

Following a brief overview of past accomplishments in space science, a status report is given concerning progress toward recovering from the Challenger accident and a number of trends are described which are likely to have a major influence on the future of the NASA Space Science program. Key changes in process include a trend toward a program centered on the use of large, long-lived facilities, the emergence of strong space capabilities outside the U.S., and steps being taken toward the diversification of NASA's launch capability. A number of recent planning activities are also discussed. Major considerations which will specifically need to be taken into account in NASA's prgram planning include the need for provision of a spectrum of flight activities and the need to recognize likely resource limitations and to do more realistic program planning.

Rosendhal, Jeffrey D.↗

NASA NTRS1988

Interplanetary protons (Ep of about 1 MeV) 1973-1986 and out to 22.4 AU

This paper uses annual mean counting rate data from detectors on two long-lived spacecraft, Pioneer 11 and IMP 8, to study the temporal and heliocentric radial distance variations of the intensity of interplanetary protons (Ep of about 1 MeV) over solar activity cycle 21. The Pioneer 11 data cover the time period April 1973 through 1986 and the heliocentric radial distance range r of between 1.0 and 2.4 AU. IMP 8, in an approximately circular geocentric orbit of semimajor axis 35 earth radii, provides comparable data at 1 AU over the time period 1974-1986. The combination of the two bodies of data shows that the annual mean intensity of such protons varies as the inverse square of the distance from the sun, irrespective of solar activity as measured by the annual mean sunspot number S. Also it is found that the annual intensity at 1 AU is approximately proportional to S, except for anomalously low values in 1979 and 1980, and that the product of the annual mean intensity at Pioneer 11 by r-squared is also approximately proportional to S, except for anomalously low values in 1979, 1980 (in particular), and 1981. The common 1980 'anomaly' is attributed to gross changes in interplanetary conditions associated with the reversal of the polarity of the sun's polar magnetic field.

Van Allen, J. A.↗