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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Resistance of mature Arabidopsis plants to mechanical deformation in relation to g-force during development

Arabidopsis plants were grown in centrifuge tubes under well standardized culture conditions. Each plant was subjected to centrifugation (roots out) for 10 min at one of a series of centripetal forces between 7 and 390g. No deformation was observed in plants centrifuged at less than 35g. An 'average' degree of deformation was attained at about 60g. All plants exposed to more than 95g were maximally deformed but none was broken nor otherwise damaged irreversibly even at 390g. In every case new shoot growth continued normally after the centrifugation. A plant population grown on horizontal clinostats (0.5 rpm) under culture conditions exactly the same as for the upright plants responded to centrifugation stress in a way that was not substantially different from the response pattern of the plants cultured upright at 1g.

Brown, A. H.↗
NASA NTRS1984

Mature thunderstorm cloud-top structure and dynamics - A three-dimensional numerical simulation study

The present investigation is concerned with results from an initial set of comparative experiments in a project which utilize a three-dimensional convective storm model. The modeling results presented are related to four comparative experiments, designated Cases A through D. One of two scientific questions considered involves the dynamical processes, either near the cloud top or well within the cloud interior, which contribute to organize cloud thermal patterns such as those revealed by IR satellite imagery for some storms having strong internal cloud-scale rotation. The second question is concerned with differences, in cloud-top height and temperature field characteristics, between thunderstorms with and without significant internal cloud-scale rotation. The four experiments A-D are compared with regard to both interior and cloud-top configurations in the context of the second question. A particular strong-shear experiment, Case B, is analyzed to address question one.

Schlesinger, R. E.↗
NASA NTRS1985

Development and Maturation of the Neuromuscular Junciton in Cell Culture Under Conditions of Simulated Zero-gravity

Alterations in gravitational conditions which alter the normal development and interactions of nerve and muscle cells grown in culture is examined. Clinostat conditions, similating Og, which produce changes in cell morphology and growth patterns is studied. Data show that rotation of cocultures of nerve and muscle cells results in morphologic changes which are predicted to significantly alter the functional interactions between the elements of a prototypic synapse. It is further predicted that similar alterations may occur in central synapses which may therefore affect the development of the central nervous system when subjected to altered gravitational conditions.

Gruener, R.↗
NASA NTRS1985

Effects of Simulated Weightlessness on Mammalian Development. Part 2: Meiotic Maturation of Mouse Oocytes During Clinostat Rotation

In order to understand the role of gravity in basic cellular processes that are important during development, the effects of a simulated microgravity environment on mammalian gametes and early embryos cultured in vitro are examined. A microgravity environment is simulated by use of a clinostat, which essentially reorients cells relative to the gravity vector. Initial studies have focused on assessing the effects of clinostat rotation on the meiotic progression of mouse oocytes. Modifications centered on providing the unique in vitro culture of the clinostat requirements of mammalian oocytes and embryos: 37 C temperature, constant humidity, and a 5% CO2 in air environment. The oocytes are observed under the dissecting microscope for polar body formation and gross morphological appearance. They are then processed for cytogenetic analysis.

Wolgemuth, D. J.↗
NASA NTRS1986

Effect of rotopositioning on the growth and maturation of mandibular bone in immobilized Rhesus monkeys

The rates of bone formation and mineralization in the mandibular cortex of juvenile Rhesus monkeys exposed to immobilization/rotopositioning are evaluated. The monkeys were restrained in a supine position and rotated 90 deg every 30 minutes through a full 360 deg for 14 days. The microscopic distribution of mineral densities in osteonal bone and the porosity of cortical bone are studied using microradiographs, and osteon closure rates are assessed using tetracycline labeling; normal distributions of osteons of different mineral density and cortical bone porosity values are observed. It is concluded that 14 days of immobilization/rotopositioning did not cause abnormal changes in osteon mineralization, cortical porosity, and osteon closure rates.

Simmons, D. J.↗
NASA NTRS1986

Mature data transport and command management services for the Space Station

The duplex space/ground/space data services for the Space Station are described. The need to separate the uplink data service functions from the command functions is discussed. Command management is a process shared by an operation control center and a command management system and consists of four functions: (1) uplink data communications, (2) management of the on-board computer, (3) flight resource allocation and management, and (4) real command management. The new data service capabilities provided by microprocessors, ground and flight nodes, and closed loop and open loop capabilities are studied. The need for and functions of a flight resource allocation management service are examined. The system is designed so only users can access the system; the problems encountered with open loop uplink access are analyzed. The procedures for delivery of operational, verification, computer, and surveillance and monitoring data directly to users are reviewed.

Carper, R. D.↗
NASA NTRS1988

Laminar flow control is maturing

Recent research demonstrates that laminar flow (LF) can be reliable in flight and that the support system need not be complex. Shaping produces favorable pressure gradients for maintaining natural laminar flow (NLF), and laminar flow control (LFC) techniques such as full chord suction promise a fuel-saving payoff of up to 30 percent on long-range missions. For large aircraft, current research is concentrated on hybrid LFC concepts which combine suction and pressure-gradient control. At NASA Ames, an F-14 with variable wing sweep has been flight tested with smooth surface gloves on the wings; preliminary results indicate high transition Reynolds numbers to sweep angles as large as 25 deg. In addition, a 757 was flight tested with an NLF glove on the right wing just outboard of the engine pylon; and the LF was found to be suprisingly robust.

Wagner, Richard D.↗
NASA NTRS1987

LFC: A maturing concept

The existence of both turbulent and laminar flow was known for a long time, but it was not until the middle of the last century that the first systematic tests with fluids were conducted to establish the physical relationships and governing laws. The importance of turbulent and laminar airflows in aeronautics was recognized as early as the 1930's, but actual laminar flow control (LFC) investigations were not undertaken until the 1940's. This overview briefly touches on some of the historical development of LFC leading up to current activities. It then examines the technical problems being addressed and potential long-term LFC applications. Past and current Douglas activities are examined and the required future testing involving hybrid laminar flow control (HLFC) is discussed.

Morris, John↗
NASA NTRS1990

A structure for maturing intelligent tutoring system student models

A special structure is examined for evolving a detached model of the user of an intelligent tutoring system. Tutoring is used in the context of education and training devices. A detached approach to populating the student model data structure is examined in the context of the need for time dependent reasoning about what the student knows about a particular concept in the domain of interest. This approach, to generating a data structure for the student model, allows an inference engine separate from the tutoring strategy determination to be used. This methodology has advantages in environments requiring real-time operation.

Holmes, Willard M.↗
NASA NTRS1990

Towards a mature measurement environment: Creating a software engineering research environment

Software engineering researchers are building tools, defining methods, and models; however, there are problems with the nature and style of the research. The research is typically bottom-up, done in isolation so the pieces cannot be easily logically or physically integrated. A great deal of the research is essentially the packaging of a particular piece of technology with little indication of how the work would be integrated with other prices of research. The research is not aimed at solving the real problems of software engineering, i.e., the development and maintenance of quality systems in a productive manner. The research results are not evaluated or analyzed via experimentation or refined and tailored to the application environment. Thus, it cannot be easily transferred into practice. Because of these limitations we have not been able to understand the components of the discipline as a coherent whole and the relationships between various models of the process and product. What is needed is a top down experimental, evolutionary framework in which research can be focused, logically and physically integrated to produce quality software productively, and evaluated and tailored to the application environment. This implies the need for experimentation, which in turn implies the need for a laboratory that is associated with the artifact we are studying. This laboratory can only exist in an environment where software is being built, i.e., as part of a real software development and maintenance organization. Thus, we propose that Software Engineering Laboratory (SEL) type activities exist in all organizations to support software engineering research. We describe the SEL from a researcher's point of view, and discuss the corporate and government benefits of the SEL. The discussion focuses on the benefits to the research community.

Basili, Victor R.↗
NASA NTRS1992

Seamless transitions from early prototypes to mature operational software - A technology that enables the process for planning and scheduling applications

New and innovative software technology is presented that provides a cost effective bridge for smoothly transitioning prototype software, in the field of planning and scheduling, into an operational environment. Specifically, this technology mixes the flexibility and human design efficiency of dynamic data typing with the rigor and run-time efficiencies of static data typing. This new technology provides a very valuable tool for conducting the extensive, up-front system prototyping that leads to specifying the correct system and producing a reliable, efficient version that will be operationally effective and will be accepted by the intended users.

Hornstein, Rhoda S.↗
NASA NTRS1992

Small experiments for the maturation of orbital cryogenic transfer technologies

The no-vent method is a promising approach to handling the problems of low-g venting during propellant transfer. A receiver tank is first cooled to remove thermal energy from the tank wall and the resultant vapor vented overboard. The nozzles mix the incoming liquid and residual vapor in the tank maintaining a thermodynamic state which allows the tank to fill with liquid without venting. Ground based testing at NASA Lewis Research Center (LeRC) has demonstrated the no-vent fill process and attempted to bound its low-gravity performance. But, low-gravity testing is required to validate the method. As an alternative to using a dedicated spacecraft for validation, several small scale experiments to study no-vent fill in low-g were formulated. Cost goals quickly limited the search to two possibilities: a secondary payload on the space shuttle, or a small scale sounding rocket experiment. The key issues of small scale experimentation are discussed, and a conceptual design of a sounding rocket experiment with liquid hydrogen for studying the fill process is presented.

Chato, David J.↗
NASA NTRS1992

Small experiments for the maturation of orbital cryogenic transfer technologies

The no-vent fill method is a promising approach to handle the problems of low-g venting during propellant transfer. A receiver tank is first cooled to remove thermal energy from the tank wall and the resultant vapor vented overboard. Then nozzles mix the incoming liquid and residual vapor in the tank maintaining a thermodynamic state which allows the tank to fill with liquid without venting. Ground based testing at NASA Lewis Research Center (LeRC) has demonstrated the no-vent fill process and attempted to bound its low-gravity performance. But, low-gravity testing is required to validate the method. As an alternative to using a dedicated spacecraft for validation the authors have formulated several small scale experiments to study no-vent fill in low-g. Cost goals quickly limited the search to two possibilities: a secondary payload on the Space Shuttle, or a small scale sounding rocket experiment. This paper will discuss the key issues of small scale experimentation and present a conceptual design of a sounding rocket experiment with liquid hydrogen for studying the fill process.

Chato, David J.↗
NASA NTRS1994

Completing below-ground carbon budgets for pastures, recovering forests, and mature forests of Amazonia

The objective of this grant was to complete below-ground carbon budgets for pastures and forest soils in the Amazon. Profiles of radon and carbon dioxide were used to estimate depth distribution of CO2 production in soil. This information is necessary for determining the importance of deep roots as sources of carbon inputs. Samples were collected for measuring root biomass from new research sites at Santana de Araguaia and Trombetas. Soil gases will be analyzed for CO2 and (14)CO2, and soil organic matter will be analyzed for C-14. Estimates of soil texture from the RADAMBRASIL database were merged with climate data to calculate soil water extraction by forest canopies during the dry season. In addition, a preliminary map of areas where deep roots are needed for deep soil water was produced. A list of manuscripts and papers prepared during the reporting periods is given.

Davidson, Eric A.↗
NASA NTRS1993

The maturing of the quality improvement paradigm in the SEL

The Software Engineering Laboratory uses a paradigm for improving the software process and product, called the quality improvement paradigm. This paradigm has evolved over the past 18 years, along with our software development processes and product. Since 1976, when we first began the SEL, we have learned a great deal about improving the software process and product, making a great many mistakes along the way. Quality improvement paradigm, as it is currently defined, can be broken up into six steps: characterize the current project and its environment with respect to the appropriate models and metrics; set the quantifiable goals for successful project performance and improvement; choose the appropriate process model and supporting methods and tools for this project; execute the processes, construct the products, and collect, validate, and analyze the data to provide real-time feedback for corrective action; analyze the data to evaluate the current practices, determine problems, record findings, and make recommendations for future project improvements; and package the experience gained in the form of updated and refined models and other forms of structured knowledge gained from this and prior projects and save it in an experience base to be reused on future projects.

Basili, Victor R.↗
NASA NTRS1993

Microscopic iron metal on glass and minerals - A tool for studying regolith maturity

A novel method of producing mixtures of glass or minerals with iron metal is presented. A portion of the Fe(2+) in basaltic glass and minerals can be reduced to metal in a few hours at 1100 C and an oxygen fugacity well below the iron-wustite buffer. Part of the iron metals forms rounded submicrometer blebs on the surfaces and in some cases within the grains. A concentration of such blebs equivalent to 20-30 percent of a grain's surface area can totally dominate the reflectance spectra of basaltic glass, pyroxene, and olivine. The production of optically opaque iron metal blebs, combined with the decline in Fe(2+), affects the glass and mineral reflectance spectra in three ways: by lowering the overall reflectivity, reducing the spectral contrast of absorption features, and producing a continuum with a general rise in reflectivity toward longer wavelengths.

Allen, C. C.↗