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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

An experimental study of heat induced surface-tension driven flow

Laser Doppler anemometry, radiation thermometry, and time-lapse photography have been used to study heat induced surface-tension driven flows in silicone oil and Fluorinert FC-43 in large open containers. For silicone oil, the effect of the surface tension gradient on the velocity field was not apparent enough to be detected. Because of its high viscosity, the oil was insensitive to outside disturbances, and the flow was steady. In the case of FC-43, the fluid was noticeably influenced by outside disturbances, and the flow was unsteady. The work reported here is part of an effort to develop experimental techniques and select test fluids for future space experiments on fluid motion in materials processing.

Kamotani, Y.↗
NASA NTRS1985

Process thresholds: Report of Working Group Number 3

The Process Thresholds Working Group concerned itself with whether a geomorphic process to be monitored on satellite imagery must be global, regional, or local in its effect on the landscape. It was pointed out that major changes in types and magnitudes of processes operating in an area are needed to be detectable on a global scale. It was concluded from a review of geomorphic studies which used satellite images that they do record change in landscape over time (on a time-lapse basis) as a result of one or more processes. In fact, this may be one of the most important attributes of space imagery, in that one can document land form changes in the form of a permanent historical record. The group also discussed the important subject of the acquisition of basic data sets by different satellite imaging systems. Geomorphologists already have available one near-global basis data set resulting from the early LANDSAT program, especially images acquired by LANDSATs 1 and 2. Such historic basic data sets can serve as a benchmark for comparison with landscape changes that take place in the future. They can also serve as a benchmark for comparison with landscape changes that have occurred in the past (as recorded) by images, photography and maps.

Williams, R. S., Jr.↗
NASA NTRS1984

High resolution evidence for the Garrett-Munk spectrum of stratospheric gravity waves

Vertical profiles of scalar horizontal winds have been measured at high resolution (10 m) in the 13 to 37 km region of the stratosphere. This resolution (at that range of altitude) represents the state-of-the-art, and is unique. The technique used smoke trails laid by rockets in the stratosphere, and were taken by AFGL at Wallops Island, VA, White Sands Missile Range, NM, and Ft. Churchill, Canada, in the 1977-78 time period. Two or three cameras were used to give the time-lapse photographs. The goal was to ascertain whether or not the internal waves of the stratosphere behave consistently with the Garrett-Munk model which was originally created for oceanic internal waves. Five profiles of horizontal wind are presented. It is concluded: (1) stratospheric internal waves obey the Garrett-Munk model for vertical wave numbers; (2) there is not statistically significant evidence for a break in the curve at high wave numbers when due allowance is made for aliasing effects; and (3) the power density level of the spectra are almost equal on a log-log scale in spite of the difference in time, season, and geographical location.

Dewan, E. M.↗
NASA NTRS1985

Studies of Model Immiscible Systems

The objectives are to use model transparent monotectics to obtain fundamental information applicable to two-phase systems in general, to apply this understanding to materials of interest in the Microgravity Science and Applications program, and to interpret results of flight experimental involving monotectic alloys. A number of model immiscible systems are in use to study various aspects of two-phase behavior within the miscibility gap and during solidification. Particle growth, coalescence and particle motions are under investigation using a holographic microscopy system. The system is capable of working with particle densities up to 10 to the 7th power particles/cubic centimeters through a 100 micron depth and can resolve particles of the order of 2 to 3 micron in diameter throughout the entire cell volume. Particle size, distribution changes with respect to time and temperature are observable from sequential holograms. Initial experiments using diethylene glycol/ethyl salicylate (DEG/ES) have demonstrated the usefulness of the technique. The thermal system controls temperature to at least plus or minus 0.001 K over the course of an experiment. A time-lapse film, made from holograms, of a succinonitrile/water solution shows particle size and number distribution changes with time under isothermal conditions. The observations are consistent with Ostwald ripening theory.

Frazier, D. O.↗
NASA NTRS1984

Study of eutectic formation

A theory was developed for the influence of convection on the microstructure of lamellar eutectics. Convection is predicted to produce a coarser microstructure, especially at low freezing rates and large volume fractions of the minority phase. Similary convection is predicted to lower the interfacial undercooling, especially at low freezing rates. Experiments using spin-up/spin-down were performed on the Mn-Bi eutectic. This stirring had a dramatic effect on the microstructure, not only making it coarser but at low freezing rates also changing the morphology of the MnBi. The coarsering persisted to moderately high freezing rates. At the lowest freezing rate, vigorous stirring caused the MnBi to be concentrated at the periphery of the ingot and absent along the center. Progress was made on developing a technique for revealing the three-dimensional microstructure of the MnBi eutectic by time-lapse videotaping while etching.

Wilcox, W. R.↗
NASA NTRS1986

A comparison between high-altitude horizon photography and direct sampling of El Chichon cloud particles

Perturbations to the visible radiation by the El Chichon aerosol layers in the stratosphere observed on May 18, 1982 in Laredo, Texas using in situ, time-lapsed photography are analyzed. The densitometric data are compared with optical counter data. Good correlation is detected for the scattered light intensities of the sky estimated with the two techniques. It is observed that the optical thickness of the stratosphere from 18.8 km to the top of the atmosphere = 0.18 and the residual optical thickness at 27 km = 0.0007. The relationship between the isodensity contours and the height of the observations, cloud cover, specific vertical aerosol distribution, and earth curvature is examined.

Coletti, A.↗
NASA NTRS1986

Small-scale eruptive filaments on the quiet sun

A study of a little known class of eruptive events on the quiet sun was conducted. All of 61 small-scale eruptive filamentary structures were identified in a systematic survey of 32 days of H alpha time-lapse films of the quiet sun acquired at Big Bear Solar Observatory. When fully developed, these structures have an average length of 15 arc seconds before eruption. They appear to be the small-scale analog of large-scale eruptive filaments observed against the disk. At the observed rate of 1.9 small-scale eruptive features per field of view per average 7.0 hour day, the rate of occurence of these events on the sun were estimated to be greater than 600 per 24 hour day.. The average duration of the eruptive phase was 26 minutes while the average lifetime from formation through eruption was 70 minutes. A majority of the small-scale filamentary sturctures were spatially related to cancelling magnetic features in line-of-sight photospheric magnetograms. Similar to large-scale filaments, the small-scale filamentary structures sometimes divided opposite polarity cancelling fragments but often had one or both ends terminating at a cancellation site. Their high numbers appear to reflect the much greater flux on the quiet sun. From their characteristics, evolution, and relationship to photospheric magnetic flux, it was concluded that the structures described are small-scale eruptive filaments and are a subset of all filaments.

Hermans, Linda M.↗
NASA NTRS1990

Demo of three ways to use a computer to assist in lab

The objective is to help the slow learner and students with a language problem, or to challenge the advanced student. Technology has advanced to the point where images generated on a computer can easily be recorded on a VCR and used as a video tutorial. This transfer can be as simple as pointing a video camera at the screen and recording the image. For more clarity and professional results, a board may be inserted into a computer which will convert the signals directly to the TV standard. Using a computer program that generates movies one can animate various principles which would normally be impossible to show or would require time-lapse photography. For example, you might show the change in shape of grains as a piece of metal is cold worked and then show the recrystallization and grain growth as heat is applied. More imaginative titles and graphics are also possible using this technique. Remedial help may also be offered via computer to those who find a specific concept difficult. A printout of specific data, details of the theory or equipment set-up can be offered. Programs are now available that will help as well as test the student in specific areas so that a Keller type approach can be used with each student to insure each knows the subject before going on to the next topic. A computer can serve as an information source and contain the microstructures, physical data and availability of each material tested in the lab. With this source present unknowns can be evaluated and various tests simulated to create a simple or complex case study lab assignment.

Neville, J. P.↗
NASA NTRS1989

A video atlas of TOMS ozone data, 1978-88

The Total Ozone Mapping Spectrometer (TOMS), on-board NASA's Nimbus-7 weather satellite, has been observing ozone over the earth once daily for the last 10 yr. A time-lapse atlas of 3440 color-coded images drawn from the TOMS archive from 1978 to 1988 has been visualized on a standard VHS videotape that is now available from NASA. The rapid and complex ozone variations presented demonstrate the difficulty of separating man-induced climate changes from natural variability. This article presents a few images from the atlas and describes interesting features in the animation, such as the correlation between ozone and 'the weather', and the recent deepening of the annual ozone hole over the South Pole. Originally intended as a browsing tool for the TOMS digital database, the videotape is a vivid presentation of the earth's atmospheric dynamics and chemistry that is recommended for scientists, educators, policy makers, and citizens concerned about the global environment.

Chesters, D.↗
NASA NTRS1992

A spaceflight experiment to investigate the effects of a range of unilateral blue light phototropic stimulations on the movements of wheat coleoptiles (6-IML-1)

In 1978, in response to an announcement of opportunity by NASA, two independent groups proposed related investigations to study the response of seedling plants to photostimulations at microgravity. The spaceflight experiment is known by its NASA acronym, FOTRAN. The scientific objectives behind the experiment are outlined, and a brief description of the spaceflight equipment and the experimental procedures developed to accomplish the aims of the experiment are presented. By reference to the results of ground-based studies, the likely scientific returns of the FOTRAN experiment will be assessed. The experiment is designed to investigate the effects of a range of blue light stimulations on the movements of wheat coleoptiles at zero-g. The seedlings will be dark-grown, and their movements assessed from infrared time-lapse video recordings made during flight. The photostimulus may be expected to modulate circumnutations of the coleoptiles, by synchronizing, initiating or amplifying these rhythmic movements, and to initiate the classic phototropic response.

Heathcote, David G.↗
NASA NTRS1993

The correspondence between X-ray bright points and evolving magnetic features in the quiet sun

The results of a study of X-ray bright points (XBPs) and small-scale evolving magnetic structures are presented. X-ray images obtained during rocket flights, full-disk magnetograms, and time-lapse magnetograms of multiple fields make up the coordinated data set. XBPs were found to be more frequently associated with pre-existing magnetic features of opposite polarity which appeared to be cancelling than with new or emerging flux regions. Most of the XBPs appeared to correspond to opposite polarity magnetic features which were converging towards each other, and some of which had not yet begun cancelling. It is suggested that most XBPs are created when converging flow brings together oppositely directed field lines. This leads to reconnection and heating in the low corona of the newly-formed loops.

Webb, D. F.↗
NASA NTRS1994

The gravitational plant physiology facility-Description of equipment developed for biological research in spacelab

In January 1992, the NASA Suttle mission STS 42 carried a facility designed to perform experiments on plant gravi- and photo-tropic responses. This equipment, the Gravitational Plant Physiology Facility (GPPF) was made up of a number of interconnected units mounted within a Spacelab double rack. The details of these units and the plant growth containers designed for use in GPPF are described. The equipment functioned well during the mission and returned a substantial body of time-lapse video data on plant responses to tropistic stimuli under conditions of orbital microgravity. GPPF is maintained by NASA Ames Research Center, and is flight qualifiable for future spacelab missions.

Heathcote, D. G.↗
NASA NTRS1997

Comparison of Satellite-Derived with Ground-Based Measurements of the Fluctuations of the Margins of Vatnajokull, Iceland 1973-1992

Vatnajokull, Iceland, is the Earth's most studied ice cap and represents a classical glaciological field site on the basis of S. Palsson's seminal glaciological field research in the late 18th century. Since the 19th century, Vatnajokull has been the focus of an array of glaciological studies by scientists from many nations, including many remote-sensing investigations since 1951. Landsat-derived positions of the termini of 11 outlet glaciers of Vatnajokull were compared with frontal positions of six of these 11 outlet glaciers determined by field observations during the period 1973-92. The largest changes during the 19 year period (1973-92) occurred in the large lobate, surge-type outlet glaciers along the southwestern, western, and northern margins of Vatnajokull, Tungnaarjokull receded - 1413 +/- 112 m (1380 +/- 1 m from ground observations), and Bruarjokull receded -1975 +/- 191 m (-2096 +/- 5 m from extrapolated ground observations) between 1973 and 1992. Satellite images can be used to delineate glacier margin changes on a time-lapse basis, if the glacier margin can be spectrally discriminated from terminal moraines and sandur deposits and if the advance/recession is larger than maximum image pixel size. "Local knowledge" of glaciers is critically important, however, in the accurate delineation of glacier margins on Landsat images.

Williams, Richard S., Jr.↗
NASA NTRS1995

Gravitropic responses of the Avena coleoptile in space and on clinostats. II. Is reciprocity valid?

Experiments were undertaken to determine if the reciprocity rule is valid for gravitropic responses of oat coleoptiles in the acceleration region below 1 g. The rule predicts that the gravitropic response should be proportional to the product of the applied acceleration and the stimulation time. Seedlings were cultivated on 1 g centrifuges and transferred to test centrifuges to apply a transverse g-stimulation. Since responses occurred in microgravity, the uncertainties about the validity of clinostat simulation of weightlessness was avoided. Plants at two stages of coleoptile development were tested. Plant responses were obtained using time-lapse video recordings that were analyzed after the flight. Stimulus intensities and durations were varied and ranged from 0.1 to 1.0 g and from 2 to 130 min, respectively. For threshold g-doses the reciprocity rule was obeyed. The threshold dose was of the order of 55 g s and 120 g s, respectively, for two groups of plants investigated. Reciprocity was studied also at bending responses which are from just above the detectable level to about 10 degrees. The validity of the rule could not be confirmed for higher g-doses, chiefly because the data were more variable. It was investigated whether the uniformity of the overall response data increased when the gravitropic dose was defined as (gm x t) with m-values different from unity. This was not the case and the reciprocity concept is, therefore, valid also in the hypogravity region. The concept of gravitropic dose, the product of the transverse acceleration and the stimulation time, is also well-defined in the acceleration region studied. With the same hardware, tests were done on earth where responses occurred on clinostats. The results did not contradict the reciprocity rule but scatter in the data was large.

Flight Experiment↗
NASA NTRS1993

Effects of inversion on plastid position and gravitropism in Ceratodon protonemata

When dark-grown tip cells of protonemata of the moss Ceratodon purpureus are turned to the horizontal, plastids first sediment towards gravity in a specific zone and then the tip curves upward. To determine whether gravitropism and plastid sedimentation occur in other orientations, protonemata were reoriented to angles other than 90 degrees. Qualitative and quantitative light microscopic observations show that plastid sedimentation along the cell axis occurs in both upright and inverted cells. However, only some plastids fall and sedimentation is incomplete; plastids remain distributed throughout the length of the cell, and those plastids that sediment do not fall all the way to the bottom of the cell. Tip cells are gravitropic regardless of stimulation angle, and as in higher plants, the maximal rate of initial curvature is in response to a 120 degrees reorientation. Infrared videomicroscopy, time-lapse studies of living, inverted protonemata indicate that amyloplast sedimentation precedes upward curvature. Together, these data further support (i) the hypothesis that amyloplast sedimentation functions in gravitropic sensing in these cells, and (ii) the idea that gravity affected the evolution of cell organization.

NASA Program Space Biology↗
NASA NTRS1990

Rapid, bilateral changes in growth rate and curvature during gravitropism of cucumber hypocotyls: implications for mechanism of growth control

The growth response of etiolated cucumber (Cucumis sativus L.) hypocotyls to gravitropic stimulation was examined by means of time-lapse photography and high-resolution analysis of surface expansion and curvature. In comparison with video analysis, the technique described here has five- to 20-fold better resolution; moreover, the mathematical fitting method (cubic splines) allows direct estimation of local and integrated curvature. After switching seedlings from a vertical to horizontal position, both upper and lower surfaces of the stem reacted after a lag of about 11 min with a two- to three-fold increase in surface expansion rate on the lower side and a cessation of expansion, or slight compression, on the upper surface. This growth asymmetry was initiated simultaneously along the length of the hypocotyl, on both upper and lower surfaces, and did not migrate basipetally from the apex. Later stages in the gravitropic response involved a complex reversal of the growth asymmetry, with the net result being a basipetal migration of the curved region. This secondary growth reversal may reflect oscillatory and/or self-regulatory behaviour of growing cells. With some qualifications, the kinetics and pattern of growth response are consistent with a mechanism involving hormone redistribution, although they do not prove such a mechanism. The growth kinetics require a growth mechanism which can be stimulated by two- to three-fold or completely inhibited within a few minutes.

Non-NASA Center↗
NASA NTRS2000

Physiology of a microgravity environment selected contribution: effects of spaceflight during pregnancy on labor and birth at 1 G

The events of parturition (labor, delivery, maternal care, placentophagia, and onset of nursing) were analyzed in female Norway rats (Rattus norvegicus) flown on either 11- or 9-day-long spaceflights beginning at the approximate midpoint of their pregnancies. Each space shuttle flight landed on the 20th day of the rats' pregnancies, just 48-72 h before parturition. After spaceflight, dams were continuously monitored and recorded by time-lapse videography throughout the completion of parturition and onset of nursing (days 22 and 23). Analyses of parturition revealed that, compared with ground controls, flight dams displayed twice the number of lordosis contractions, the predominant labor contraction type in rats. The number of vertical contractions (those that immediately precede expulsion of a pup from the womb), the duration of labor, fetal wastage, number of neonates born, neonatal birth weights, placentophagia, and maternal care during parturition, including the onset of nursing, were comparable in flight and ground control dams. Our findings indicate that, with the exception of labor contractions, mammalian pregnancy and parturition remain qualitatively and quantitatively intact after spaceflight during pregnancy.

Non-NASA Center↗