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Results for “areal density”

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

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Ceramic composite protection for turbine disc bursts

Ceramic composite turbine disc protection panels for the A300B were developed using armor technology. Analytical predictions for modifying the ballistic projectile armor system were verified by a test program conducted to qualify the rotor containment system. With only a slight change in the areal density of the armor system a more than two-fold increase in kinetic energy protection level was achieved. Thickness of the fiberglass reinforced plastic backing material was increased to achieve an optimum ratio of ceramic thickness to backing thickness for the different ballistic defeat condition.

Gardner, P. B.↗
NASA NTRS1979

Space reflector technology and its system implications

The technical feasibility of providing nearly continuous solar energy to a world-distributed set of conversion sites by means of a system of orbiting, large-area, low-areal-density reflecting structures is examined. Requisite mirror area to provide a chosen, year-averaged site intensity is shown. A modeled reflector structure, with suitable planarity and ability to meet operational torques and loads, is discussed. Typical spatial and temporal insolation profiles are presented. These determine the sizing of components and the output electric power from a baselined photovoltaic conversion system. Technical and economic challenges which, if met, would allow the system to provide a large fraction of future world energy needs at costs competitive to circa-1995 fossil and nuclear sources are discussed.

Billman, K. W.↗
NASA NTRS1981

Response of large cavity ion chambers to space protons

The assumption that spherical-shell ion chamber rssponse is equal to the dose in the center of the cavity is found to be a poor approximation for ion chambers used for area monitoring in the space program. The dose response is calculated using the appropriate areal density distribution function. Effects of nuclear reaction are evaluated using proton buildup factors. Errors of up to 100% are found for some components of the space radiation environments.

Wilson, J. W.↗
NASA NTRS1983

Entwined and parallel bundled orbits as alternative models for narrow planetary ringlets

Particle orbits can be bundled in two different ways to produce narrow, Uranus-type ringlets. The usual assumption is that they are packed in a parallel manner in a structure that is essentially only two-dimensional, but it is then difficult to explain the large numbers of particles per unit area of the ring plane that are inferred from the observations. The alternative of a bundle of entwined orbits produces a three-dimensional structure of potentially large projected areal density. A start has been made in identifying possible mechanisms for stabilizing these structures, but much remains to be done, particularly for the less-studied model of entwined orbits. The two models might be discriminated observationally by differences in the motion of the line of intersection of the orbital and equatorial planes, and by the predicted radial reversal (entwined) or nonreversal (parallel) of features in occultation signatures taken at certain longitudes.

Eshleman, V. R.↗
NASA NTRS1985

Small-scale flux emergence and the evolution of equatorial coronal holes

To study the formation and development of coronal holes, their association with X-ray bright points has been investigated. The areal density of X-ray bright points was measured within the boundaries of coronal holes and was found to increase linearly with time for each of the three, long-lived, equatorial coronal holes of the Skylab era. Analysis of the data shows that the effect is not the result of global changes in bright point number and is therefore a property of the restricted longitude region which contains the coronal hole. The bright point density at the time of the hole's formation was also measured and, although the result is more uncertain, was found to be similar to the bright point number over the solar surface. No association was found between bright points and the rate of change of coronal hole area.

Davis, J. M.↗
NASA NTRS1985

Development of structural-composite reflector panels for a submillimeter space telescope

Reflector panels for the Large Deployable Reflector (LDR) for a 20m, Earth-orbiting, submillimeter and infrared telescope were designed. The panels must be 1 to 2 m in diameter with surface precision and thermal stability of a few microns, and an areal density of or = 10 kg/sqm. Using a combination of design, analytical modeling, panel fabrication, and testing, two sizes of graphite/epoxy panels were produced. One is 15 sqcm the other 60 sqcm, both weighing 5 to 7 kg/sqm with manufactured surface accuracies of a few tenths of a micron and thermal stability at LDR orbital temperatures of a few microns.

Freeland, R. E.↗
NASA NTRS1989

Impact cratering and the surface age of Venus: The Pre-Magellan controversy

The average surface age of a planet is a major indicator of the level of its geologic activity and thus of the dynamics of its interior. Radar images obtained by Venera 15/16 from the northern quarter of the Venus (lat 30 to 90 degs) reveal about 150 features that resemble impact craters, and they were so interpreted by Soviet investigators B. A. Ivanov, A. T. Basilevsky, and their colleagues. These features range in diameter from about 10 to 145 km. Their areal density is remarkably similar to the density of impact structures found on the American and European continental shields. The basic difference between the Soviet and American estimates of the average surface age of Venus's northern quarter is due to which crater-production rate is used for the Venusian environment. Cratering rates based on the lunar and terrestrial cratering records, as well as statistical calculations based on observed and predicted Venus-crossing asteroids and comets, have been used in both the Soviet and American calculations. The single largest uncertainty in estimating the actual cratering rates near Venus involves the shielding effect of the atmosphere.

Schaber, Gerald G.↗
NASA NTRS1989

Primary mirror and mount technology for the Stratospheric Observatory for Infrared Astronomy (SOFIA) telescope

Candidate technologies for a lightweight primary mirror for the SOFIA telescope are evaluated for both mirror blank fabrication and polishing. Two leading candidates for the type mirror blank are considered: the frit-bonded, structured form, and the thin meniscus form. The feasible mirror is required to be very lightweight with an areal density of approximately 100 kg/sq m, have an f/ratio near 1.0, and have surface quality that permits imaging in the visible as well as the infrared. Also considered are the results of a study conducted to assess the feasibility of designing a suitable mounting system for the primary mirror. The requirements for the mount design are given both in terms of the environmental conditions and the expected optical performance. PATRAN and NASTRAN programs are used to model mirror and mounting. The sandwich-type mirror made of ultra low expansion silica with square cells in the core, is modeled using equivalent solid elements for the core. The design study produces primary mirror surface deflections in 1g as a function of mirror elevation angles. The surface is analyzed using an optical analysis program, FRINGE, to give a prediction of the mirror optical performance. Results from this analysis are included.

Melugin, Ramsey K.↗
NASA NTRS1991

Surface activation of Concorde by Be-7

Activation analysis of two airframe parts from Concorde aircraft has identified the presence of Be-7, a nuclide which was found by other investigators to have been collected on the forward edge of the Long Duration Exposure Facility (LDEF) structure. The results of the Concorde analysis indicate that this phenomenon is very much a surface effect, and that the areal densities of the Be-7 are comparable to those found for LDEF. The collection of Be-7 by the aircraft must be greater than in the case of LDEF (since the duration for which Concorde is accumulating the nuclide is shorter) and is of the order of 1.9 to 40 nuclei sq cm/s, depending upon assumptions made regarding the efficiency of the process which removes the radionuclide.

Truscott, P. R.↗
NASA NTRS1991

Gallium Arsenide solar cell radiation damage experiment

Gallium arsenide (GaAs) solar cells for space applications from three different manufactures were irradiated with 10 MeV protons or 1 MeV electrons. The electrical performance of the cells was measured at several fluence levels and compared. Silicon cells were included for reference and comparison. All the GaAs cell types performed similarly throughout the testing and showed a 36 to 56 percent power areal density advantage over the silicon cells. Thinner (8-mil versus 12-mil) GaAs cells provide a significant weight reduction. The use of germanium (Ge) substrates to improve mechanical integrity can be implemented with little impact on end of life performance in a radiation environment.

Maurer, R. H.↗
NASA NTRS1991

The ejecta deposit of the ancient basin Herschel - An example of a generally unrecognized Martian sedimentological unit

This paper discusses geomorphic features of Martian impact basins and of the basin ejecta landforms, with special attention given to the Hershel Basin (14 deg S, 230 deg W; 300-km diam) and its interior and exterior landforms. A map of geomorphic features in and around Hershel Basin is presented together with data on the basin's areal densities. It is estimated that the impact that formed Herschel Basin occurred during the Late Noachian Epoch upon an already heavily cratered Middle Noachian surface.

Edgett, K. S.↗
NASA NTRS1991

Evolution of optical coatings in earth orbit

High-resolution medium-energy backscattering analyses have been performed on SiO and SiO2 optical coatings that were exposed to the space environment aboard the NASA long-duration experiment module flight. The data show an increase in areal density of 1 percent (resolved at the 10 sigma level) in the SiO film as a result of this exposure. It appears that this effect has been produced by the incorporation of atomic oxygen from the ambient environment. Data on the SiO2 film are less compelling but are consistent with some loss of material from the surface. These analyses set a new standard for profiling film thicknesses by ion backscattering.

Mendelhall, Marcus H.↗
NASA NTRS1991

Large deployable antenna program. Phase 1: Technology assessment and mission architecture

The program was initiated to investigate the availability of critical large deployable antenna technologies which would enable microwave remote sensing missions from geostationary orbits as required for Mission to Planet Earth. Program goals for the large antenna were: 40-meter diameter, offset-fed paraboloid, and surface precision of 0.1 mm rms. Phase 1 goals were: to review the state-of-the-art for large, precise, wide-scanning radiometers up to 60 GHz; to assess critical technologies necessary for selected concepts; to develop mission architecture for these concepts; and to evaluate generic technologies to support the large deployable reflectors necessary for these missions. Selected results of the study show that deployable reflectors using furlable segments are limited by surface precision goals to 12 meters in diameter, current launch vehicles can place in geostationary only a 20-meter class antenna, and conceptual designs using stiff reflectors are possible with areal densities of 2.4 deg/sq m.

Rogers, Craig A.↗
NASA NTRS1992

Surface activation of Concorde by Be-7

Activation analysis of two airframe components from the Concorde aircraft has identified the presence of Be-7, a nuclide found by other investigators that was deposited on the forward edge of the Long Duration Exposure Facility (LDEF) structure. The results of the Concorde analysis indicate that this phenomenon is very much a surface effect, and that the areal densities of the Be-7 are comparable to those found for LDEF. The collection of Be-7 by the aircraft must be greater than in the case of LDEF (since duration for which Concorde is accumulating the nuclide is shorter) and is of the order of 1.2 to 41 nuclei/sq cm(-)s(exp -1) depending upon assumptions made regarding the altitude at which collection becomes appreciable, and the efficiency of the process which removes the radionuclide.

Truscott, P. R.↗
NASA NTRS1992

A conceptual design of a large aperture microwave radiometer geostationary platform

A conceptual design of a Large Aperture Microwave Radiometer (LAMR) Platform has been developed and technology areas essential to the design and on-orbit viability of the platform have been defined. Those technologies that must be developed to the requirement stated here for the LAMR mission to be viable include: advanced radiation resistant solar cells, integrated complex structures, large segmented reflector panels, sub 3 kg/m(exp 2) areal density large antennas, and electric propulsion systems. Technology areas that require further development to enhance the capabilities of the LAMR platform (but are not essential for viability) include: electrical power storage, on-orbit assembly, and on-orbit systems checkout and correction.

Garn, Paul A.↗
NASA NTRS1991

Development of structural composite mirror technology for submillimeter space telescopes

The technical approach to the design, manufacturing, testing, and analytical simulation of lightweight graphite/epoxy mirrors is described. The precision segmented reflector (PSR) program has produced (1) 1.0-m graphite/epoxy panels with areal densities of 7 kg/sq m as-manufactured surface precision near 1 micron rms, (2) 0.5-m panels with figure changes less than 1 micron rms for temperature reductions of 100 K, (3) analytical performance-prediction capability with submicron accuracy relative to panel thermal distortion, and (4) a unique thermal vacuum test facility for structural composite mirrors.

Freeland, R. E.↗
NASA NTRS1992

An enhanced Whipple Bumper system - Impact resistance of composite materials

For long-duration space flights where human occupation is expected, micrometeroid and debris shields are necessary to prevent puncture of the pressure vessels. Current 'Whipple Bumper' designs range from single thin sheets of aluminum to complicated structures of many energy absorbing layers. This paper details the results of an experimental program tao determine the increased protection afforded by intermediate bumpers made of composite material structures. Various configurations of honeycomb support structures sandwiched between layers of materials such as Kevlar, Spectra, aluminum, and others are inserted between the bumper and pressure shell. The areal densities of each new material structure are maintained constant so that the results compare directly with single-sheet aluminum intermediate bumpers.

Zwiener, J.↗
NASA NTRS1992

Venus - Satellite orbital decay, ephemeral ring formation, and subsequent crater production

The question of whether most or even all of the observed impact features on the surface of Venus can be derived from satellitic material is addressed. Consideration is given to the hypothesis that the craters retained on the surface of Venus were all emplaced within a relatively short interval, as collisional fragments of a former satellite impacted the surface. It is concluded that the areal density of craters may provide no absolute age information at all: the craters may be as recent as the last significant satellite loss event.

Bills, Bruce G.↗