Search NASA⌕ Search

SEARCH · Search NASA

Results for “21”

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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

USSR Space Life Sciences Digest, issue 21

This is the twenty-first issue of NASA's USSR Space Life Sciences Digest. It contains abstracts of 37 papers published in Russian language periodicals or books or presented at conferences and of a Soviet monograph on animal ontogeny in weightlessness. Selected abstracts are illustrated with figures and tables from the original. A book review of a work on adaptation to stress is also included. The abstracts in this issue have been identified as relevant to 25 areas of space biology and medicine. These areas are: adaptation, biological rhythms, body fluids, botany, cardiovascular and respiratory systems, cytology, developmental biology, endocrinology, enzymology, equipment and instrumentation, exobiology, gravitational biology, habitability and environmental effects, hematology, human performance, life support systems, mathematical modeling, metabolism, microbiology, musculoskeletal system, neurophysiology, operational medicine, perception, psychology, and reproductive system.

Hooke, Lydia Razran↗
NASA NTRS1988

High resolution chronology of late Cretaceous-early Tertiary events determined from 21,000 yr orbital-climatic cycles in marine sediments

A number of South Atlantic sites cored by the Deep Sea Drilling Project (DSDP) recovered late Cretaceous and early Tertiary sediments with alternating light-dark, high-low carbonate content. The sedimentary oscillations were turned into time series by digitizing color photographs of core segments at a resolution of about 5 points/cm. Spectral analysis of these records indicates prominent periodicity at 25 to 35 cm in the Cretaceous intervals, and about 15 cm in the early Tertiary sediments. The absolute period of the cycles that is determined from paleomagnetic calibration at two sites is 20,000 to 25,000 yr, and almost certainly corresponds to the period of the earth's precessional cycle. These sequences therefore contain an internal chronometer to measure events across the K/T extinction boundary at this scale of resolution. The orbital metronome was used to address several related questions: the position of the K/T boundary within magnetic chron 29R, the fluxes of biogenic and detrital material to the deep sea immediately before and after the K/T event, the duration of the Sr anomaly, and the level of background climatic variability in the latest Cretaceous time. The carbonate/color cycles that were analyzed contain primary records of ocean carbonate productivity and chemistry, as evidenced by bioturbational mixing of adjacent beds and the weak lithification of the rhythmic sequences. It was concluded that sedimentary sequences that contain orbital cyclicity are capable of providing resolution of dramatic events in earth history with much greater precision than obtainable through radiometric methods. The data show no evidence for a gradual climatic deterioration prior to the K/T extinction event, and argue for a geologically rapid revolution at this horizon.

Herbert, Timothy D.↗
NASA NTRS1989

Space power technology 21: Photovoltaics

The Space Power needs for the 21st Century and the program in photovoltaics needed to achieve it are discussed. Workshops were conducted in eight different power disciplines involving industry and other government agencies. The Photovoltaics Workshop was conducted at Aerospace Corporation in June 1987. The major findings and recommended program from this workshop are discussed. The major finding is that a survivable solar power capability is needed in photovoltaics for critical Department of Defense missions including Air Force and Strategic Defense Initiative. The tasks needed to realize this capability are described in technical, not financial, terms. The second finding is the need for lightweight, moderately survivable planar solar arrays. High efficiency thin III-V solar cells can meet some of these requirements. Higher efficiency, longer life solar cells are needed for application to both future planar and concentrator arrays with usable life up to 10 years. Increasing threats are also anticipated and means for avoiding prolonged exposure, retraction, maneuvering and autonomous operation are discussed.

Wise, Joseph↗
NASA NTRS1988

Imaging spectroscopy II; Proceedings of the Meeting, San Diego, CA, Aug. 20, 21, 1987

The conference presents papers on airborne imaging spectrometers, imaging spectrometry analysis, and spaceborne imaging spectrometers. Consideration is given to an imaging spectrometer for ocean and land remote sensing, an advanced solid-state array spectroradiometer, airborne visible/infrared imaging spectrometer design and performance, and a signal chain for the airborne visible/infrared imaging spectrometer. Other topics include imaging spectrometry as a tool for botanical mapping, the estimation of forest canopy characteristics and nitrogen cycling using lasing spectrometry, and a continuous readout photon counting imaging detector.

Vane, Gregg↗
NASA NTRS1988

Solar rotation measurements at Mount Wilson. V - Reanalysis of 21 years of data

The procedure for reducing the data acquired during the Mt. Wilson Observatory synoptic program is described, and a program for acquiring as many scans per day as possible of the solar magnetic and velocity fields is discussed. A fitting formula which removes the background velocity field from each scan has been derived. It is suggested that the difference between the limb shift along the north-south axis and the east-west axis may be due to the meridional circulation.

Ulrich, Roger K.↗
NASA NTRS1989

A search for the solar roots of the most disturbed interplanetary field intervals of solar cycle 21

During the course of the Pioneer Venus Orbiter mission, fairly continuous interplanetary plasma and magnetic field data were obtained which span the interval from prior to the last solar maximum to the current solar minimum recovery. Within this nearly complete solar cycle interval, several periods of exceptional disturbance of the interplanetary field stand out. The available solar data have been examined to determine what features, if any, distinguish these periods. Neither flare nor coronal mass ejection reports show particularly unusual behavior. However, these periods appear to occur in conjunction with marked changes in the interplanetary sector structure. This suggests that heliospheric current sheet reconfiguration is an indicator of the level of interplanetary disturbance distinct from the more traditional solar activity data.

Luhmann, J. G.↗
NASA NTRS1989

The Teton-Yellowstone Tornado of 21 July 1987

The Teton-Yellowstone Tornado, rated F4, crossed the Continental Divide at 3070 m, leaving behind a damage swath 39.2-km long and 2.5-km wide. A detailed damage analysis by using stereo-pair and color photos revealed the existence of four spinup swirl marks and 72 microburst outflows inside the damage area. The tornado was spawned by a mesocyclone that formed at the intersection of a mesohigh boundary and a warm front. The parent cloud of the tornado, tracked on eight infrared-temperature maps from GOES East and West, moved at 25 m s-1 and the number of cold temperature pixels below -60 C reached a distinct peak during the tornado time. Identified and tracked also are two warm spots enclosed inside the cold anvil cloud. On the basis of their identity and movement, an attempt was made to explain the cause of these spots as being the stratospheric cirrus clouds.

Fujita, T. Theodore↗
NASA NTRS1988

Technology for Large Space Systems: a Bibliography with Indexes (Supplement 21)

This bibliography lists 745 reports, articles, and other documents introduced into the NASA scientific and technical information system between January 1, 1989 and June 30, 1989. Its purpose is to provide helpful information to the researcher, manager, and designer in technology development and mission design according to system, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion, and solar power satellite systems.

Source record↗
NASA NTRS1989

Evolution of the sun's polar fields during sunspot cycle 21 - Poleward surges and long-term behavior

Longitudinally averaged observations of the photospheric field during 1976-1986 are analyzed using a flux transport model. The way in which source eruptions, supergranular diffusion, and meridional flow collaborate to produce strong, highly concentrated polar fields near sunspot minimum is clarified as follows: (1) widespread eruptions of individual bipolar magnetic regions, with their leading polarity flux equatorward of their trailing polarity flux, collectively establish a large-scale separation of polarities in latitude; (2) the low-latitude, leading polarity flux diffuses across the equator and merges with its opposite hemisphere counterpart; and (3) meridional flow carries the resulting surplus of trailing polarity flux to the poles, and concentrates it there against the spreading effect of diffusion. Episodic 'surges' of flux to the poles are induced by fluctuations in the source eruption rate. Simulations indicate that relatively weak, trailing polarity surges may occur even in a steady flow field. However, in order to account for the giant surges of alternating polarity and the resulting oscillations in the polar field strength observed during 1980-1982, both accelerated flow and enhanced eruption rates are required.

Wang, Y.-M.↗
NASA NTRS1989

Average properties of bipolar magnetic regions during sunspot cycle 21

The statistical properties of some 2700 bipolar magnetic regions (BMRs) with magnetic fluxes equal to or greater than 3 x 10 to the 20th Mx, which erupted during 1976-1986, are examined. The analysis shows the following: (1) the average flux per BMR declined between 1977 and 1985; (2) the average tilts of BMRs relative to the east-west line increase toward higher latitudes; (3) weaker BMRs had larger root-mean-square tilt angles than stronger BMRs at all latitudes; and (4) over the interval 1976-1986, BMRs with their leading poles equatorward of their trailing poles contributed a total of 4 times as much flux as BMRs with inverted tilts, but the relative amount of flux contributed by BMRs with inverted or zero tilts increased as the sunspot cycle progressed.

Wang, Y.-M.↗
NASA NTRS1990

Spatial gradients in the heliospheric magnetic field - Pioneer 11 observations between 1 AU and 24 AU, and over solar cycle 21

The large-scale temporal behavior and spatial gradients in the heliospheric magnetic field were investigated using magnetic field observations by Pioneer 11 and ISEE 3/ICE satellites, including observations out to a radial distance of 24 AU and over a time interval that includes the recent solar minimum. It was found that, to first order, the gradients in the magnetic field magnitude and in the azimutal component agree well with the Parker (1958) model. The analysis of the Pioneer data confirms previous reports of a magnetic field flux deficit of about 1 percent/AU, so that at 20 AU the relative deficit is of the order of 20 percent. It is argued that most of the magnetic field deficit is in the radial gradient.

Winterhalter, Daniel↗
NASA NTRS1990

Solar proton events during solar cycles 19, 20, and 21

Earlier studies based on a single solar cycle had resulted in a sharp division of events into 'ordinary' and 'anomalously large' events. Two such entirely separate distributions imply two entirely separate acceleration mechanisms, one common and the other very rare. The sharp division is neither required nor justified by this larger sample. Instead the event intensity forms a smooth distribution for intensities up to the largest observed implying that any second acceleration mechanism cannot be rare. Also, a clear bimodal variation of annual integrated flux with solar cycle phase but no statistically significant tendency for the large events to avoid sunspot maximum is found. There is almost no relation between the maximum sunspot number in a solar cycle and the solar cycle integrated flux. It is also found that for annual sunspot numbers greater than 35 there is no relation whatsoever between the annual sunspot numbers and annual integrated flux.

Feynman, J.↗
NASA NTRS1991

Observations of intermediate- and high-degree p-mode oscillations during sunspot cycles 21 and 22

Extensive time series of resolved solar images have been available for helioseismological investigations since the late 1970's. The paper presents examples of the frequencies, power levels, modal energies, and widths of solar intermediate-degree and high-degreee p-modes obtained at the Mt. Wilson Observatory's 60-Foot Solar Tower Telescope during the rising phase of the current sunspot cycle. It is shown that the inclusion of frequency splittings from the high-degree p-modes has made it possible to demonstrate that the sun's internal equatorial angular velocity is not constant with radius but varies systematically with radius throughout the solar convection zone and below.

Rhodes, E. J.↗
NASA NTRS1991

Elemental abundance analyses with DAO spectrograms. VII - The late normal B stars Pi Ceti, 134 Tauri, 21 Aquilae, and Nu Capricorni and the use of Reticon spectra

This paper presents elemental abundance analyses of sharp-lined normal late B stars. These stars exhibit mostly near-solar abundances, but each star also shows a few abundances which are a factor of 2 less than solar. The coadded photographic spectrograms are supplemented with Reticon data. A comparison of 261 equivalent widths on 2.4 A/mm spectra of sharp-lined B and A stars shows that the Reticon equivalent widths are about 95 percent of the coadded equivalent mean. The H-gamma profiles of the coadded and Reticon spectra for eight sharp-lined stars show generally good agreement. The generally high quality of the coadded data produced from 10 or more spectrograms is confirmed using the REDUCE graphics-oriented computed reduction code. For five stars, metal lines which fall in the gap between the U and V plates are analyzed using Reticon data.

Adelman, Saul J.↗
NASA NTRS1991

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 21: Technological innovation and technical communications: Their place in aerospace engineering curricula. A survey of European, Japanese, and US Aerospace Engineers and Scientists

Aerospace engineers and scientists from Western Europe, Japan, and the United States were surveyed as part of the NASA/DoD Aerospace Knowledge Diffusion Research Project. Questionnaires were used to solicit their opinions regarding the following: (1) the importance of technical communications to their profession; (2) the use and production of technical communications; and (3) their views about the appropriate content of an undergraduate course in technical communications. The ability to communicate technical information effectively was very important to the aerospace engineers and scientists who participated in the study. A considerable portion of their working week is devoted to using and producing technical information. The types of technical communications used and produced varied within and among the three groups. The type of technical communication product used and produced appears to be related to respondents' professional duties. Respondents from the three groups made similar recommendations regarding the principles, mechanics, and on-the-job communications to be included in an undergraduate technical communications course for aerospace majors.

Pinelli, Thomas E.↗
NASA NTRS1992

Small Business Innovation Research. Program solicitation. Closing date: July 21, 1992

The National Aeronautics and Space Administration (NASA) invites small businesses to submit Phase 1 proposals in response to its Small Business Innovation Research (SBIR) Program Solicitation 92-1. Firms with research or research and development capabilities (R/R&D) in science or engineering in any of the areas listed are encouraged to participate. This, the tenth annual SBIR solicitation by NASA, describes the program, identifies eligibility requirements, describes the proposal evaluation and award selection process, and provides other information to assist those interested in participating in NASA's SBIR program. It also identifies, in Section 8.0, the technical topics and subtopics in which SBIR Phase 1 proposals are solicited in 1992. These topics and subtopics cover a broad range of current NASA interests but do not necessarily include all areas in which NASA plans or currently conducts research. The NASA SBIR program seeks innovative approaches that respond to the needs, technical requirements, and new opportunities described in the subtopics. The focus is on innovation through the use of emerging technologies, novel applications of existing technologies, exploitation of scientific breakthroughs, or new capabilities or major improvements to existing technologies. NASA plans to select about 320 high-quality research or research and development proposals for Phase 1 contract awards on the basis of this Solicitation. Phase 1 contracts are normally six months in duration and funded up to $50,000, including profit. Selections will be based on the competitive merits of the offers and on NASA needs and priorities.

Source record↗
NASA NTRS1991

Measurements of ClO and O3 from 21 deg N to 61 deg N in the lower stratosphere during February 1988 - Implications for heterogeneous chemistry

The decline in stratospheric ozone at northern midlatitudes in wintertime may be caused by chlorine photochemistry that has been enhanced by heterogeneous reactions. The possibility that the heterogeneous reaction of N2O5 on sulfate aerosols is the cause of this decadal ozone decline is examined by comparing ClO and O3 measurements made in the lower stratosphere during February, 1988, with results from a 2D model. At midlatitudes, the abundances, latitudinal, and seasonal gradients of the observed ClO are similar to the results of a model with heterogeneous chemistry, but are in strong disagreement with the results from the model with only gas-phase chemistry. At low latitudes, agreement is best with the results of the model with only gas-phase chemistry. Limited observations indicate that the amount of reactive chlorine is being enhanced, and that heterogeneous chemistry is a likely cause.

King, J. C.↗
NASA NTRS1991

Free-space laser communication technologies III; Proceedings of the Meeting, Los Angeles, CA, Jan. 21, 22, 1991

The present volume on free-space laser communication technologies discusses system analysis, performance, and applications, pointing, acquisition, and tracking in beam control, laboratory demonstration systems, and transmitter and critical component technologies. Attention is given to a space station laser communication transceiver, meeting intersatellite links mission requirements by an adequate optical terminal design, an optical approach to proximity-operations communications for Space Station Freedom, and optical space-to-ground link availability assessment and diversity requirements. Topics addressed include nonmechanical steering of laser beams by multiple aperture antennas, a free-space simulator for laser transmission, heterodyne acquisition and tracking in a free-space diode laser link, and laser terminal attitude determination via autonomous star tracking. Also discussed are stability considerations in relay lens design for optical communications, liquid crystals for lasercom applications, and narrowband optical interference filters.

Begley, David L.↗