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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 1,423 records · Page 79
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Alterations in glucose and protein metabolism in animals subjected to simulated microgravity

Reduction of physical activity due to disease or environmental restraints, such as total bed rest or exposure to spaceflight, leads to atrophy of skeletal muscle and is frequently accompanied by alterations in food intake and the concentration of metabolic regulatory hormones such as insulin. Hindlimb suspension of laboratory rats, as a model for microgravity, also shows marked atrophy of gravity-dependent muscles along with a reduced gain in body weight. Suspended rats exhibit enhanced sensitivity to insulin-induced glucose uptake when compared with normal control rats and resistance to insulin action when compared with control rats matched similarly for reduced body weight gain. These changes are accompanied by decreased insulin binding and tyrosine kinase activity in soleus but not plantaris muscle, unchanged glucose uptake by perfused hindlimb and decreased sensitivity but not responsiveness to insulin-induced suppression of net proteolysis in hindlimb skeletal muscle. These findings suggest that loss of insulin sensitivity during muscle atrophy is associated with decreased insulin binding and tyrosine kinase activity in atrophied soleus muscle along with decreased sensitivity to the effects of insulin on suppressing net protein breakdown but not on enhancing glucose uptake by perfused hindlimb.

Mondon, C. E.↗
NASA NTRS1992

Microwave processing of materials in microgravity

The Jet Propulsion Laboratory is investigating the use of microwave energy as a controlled heating and positioning source for the processing of materials in the microgravity environment of space. Ground-based studies of the positioning capabilities of microwave forces are presented. The ability to quickly and efficiently control the heating of a variety of materials is demonstrated, and the heating of several representative materials is presented. A compact cold-wall microwave furnace compatible with future flight experiments in a shuttle mid-deck cannister is evaluated. The development of a hybrid containerless processing facility that will serve both as an acoustic positioning chamber and a microwave-heating cavity is also proposed. The design characteristics of a cold-wall furnace and hybrid heater/positioner are reviewed.

Barmatz, M.↗
NASA NTRS1992

A Microgravity Science and Applications Program overview

The Microgravity Science and Space Applications Program (MSSAP) is described in terms of the research it supports in fields related to physical processes and materials. Three primary fields are reviewed which include fundamental sciences such as transport phenomena, materials science, and biotechnology issues such as macromolecular crystal growth. The program strategy is to begin with MSSAP studies in ground-based facilities such as drop towers and to evolve to flight experiments as the research achieves technical maturity. Ground-based experiments in progress include the Acceleration Characterization and Analysis Project and the Solid Surface Combustion Experiment (SSCE). Several furnace experiments for materials studies are described including flight tests for the SSCE, and reference is given to a flight for the Protein-Crystal Growth Experiment.

Kicza, M. E.↗
NASA NTRS1992

Effects of a simulated microgravity model on cell structure and function in rat testis and epididymis

The effect of simulated microgravity on the structure and function of the testis and epididymis cells was investigated in rats subjected to 7 days of tail suspension. Results of a histological examination revealed presence of disorganized seminiferous tubules and accumulation of large multinucleated cells and spermatids in the lumen of the epididymis. In addition, decreases in the content of testis protein and in testosterone levels in the testis, the interstitial fluid, and the epididymis were observed.

Hadley, Jill A.↗
NASA NTRS1992

Crystal Growth Furnace - An overview of the system configuration and planned experiments on the First United States Microgravity Laboratory mission

The Crystal Growth Furnace (CGF) system configuration for the First United States Microgravity Laboratory (USML-1) mission is reviewed, and the planned on-orbit experiments are briefly described. The CGF is configured to accommodate four scientific experiments involving crystal growth which are based on the classical Bridgman method and CVT method, including vapor transport crystal growth of mercury cadmium telluride; crystal growth of mercury zinc telluride by directional solidification; seeded Bridgman growth of zinc-doped cadmium telluride; and Bridgman growth of selenium-doped gallium arsenide.

Srinivas, R.↗
NASA NTRS1992

The Burning of Metals and Alloys in Microgravity

The NASA-Lewis 2.2-sec drop tower has been used to characterize the oxygen-atmosphere burning of several representative spacecraft environment metallic materials in microgravity; these included rods of 2219 Al alloy, 316 stainless steel, Fe, and Ti, as well as sheets and meshes of 316 stainless steel. The absence of buoyant forces does not preclude extinguishment of the combustion process, and the regression rate of the melting interface of the cylindrical rods is significantly greater than in normal gravity. The flammability of such sample shapes as thin sheets, which are known to extinguish in normal gravity, is enhanced. Volatile combustion products are generated, in contrast to the normal gravity regime.

Steinberg, Theodore A.↗
NASA NTRS1992

Stability limits for bioconvective fractals - Microgravity prospects

Fractal objects are delicate aggregates which show self-similar behavior and vanishing density for increasing length scales. In practice real fractals in nature however possess only a limited region of verifiable self-similarity. As natural fractal objects increase in size, they become easier to disrupt mechanically. Herein the effects of thermal vibrations and gravity are investigated as deforming forces on fractal aggregation. Example calculations are carried out on a biological fractal formed from the surface aggregation of various cells such as alga and bacteria. For typical cell parameters, the predicted diameter of this so-called 'bioconvective' fractal agrees well with the observed limits of about 5 cm. On earth, this size represents an experimental maximum for finding bioconvective fractal objects. To extend this size range of fractals available for statistical study, a reduced gravity environment offers one way to achieve larger fractals. For these enhanced sizes, the present scaling predicts that microgravity can yield up to a 35-fold improvement in extending statistical resolution.

Noever, David A.↗
NASA NTRS1992

Development of task network models of human performance in microgravity

This paper discusses the utility of task-network modeling for quantifying human performance variability in microgravity. The data are gathered for: (1) improving current methodologies for assessing human performance and workload in the operational space environment; (2) developing tools for assessing alternative system designs; and (3) developing an integrated set of methodologies for the evaluation of performance degradation during extended duration spaceflight. The evaluation entailed an analysis of the Remote Manipulator System payload-grapple task performed on many shuttle missions. Task-network modeling can be used as a tool for assessing and enhancing human performance in man-machine systems, particularly for modeling long-duration manned spaceflight. Task-network modeling can be directed toward improving system efficiency by increasing the understanding of basic capabilities of the human component in the system and the factors that influence these capabilities.

Diaz, Manuel F.↗
NASA NTRS1992

Heat and Mass Transport from Thermally Degrading Thin Cellulosic Materials in a Microgravity Environment

Attention is given to a theoretical model describing the behavior of a thermally thin cellulosic sheet heated by external thermal radiation in a quiescent microgravity environment. This model describes thermal and oxidative degradation of the sheet and the heat and mass transfer of evolved degradation products from the heated cellulosic surface into the gas phase. Two calculations are carried out: heating without thermal degradation, and heating with thermal degradation of the sheet with endothermic pyrolysis, exothermic thermal oxidative degradation, and highly exothermic char oxidation. It is shown that pyrolysis is the main degradation reaction. Self-sustained smoldering is controlled and severely limited by the reduced oxygen supply.

Kushida, G.↗
NASA NTRS1992

Optimal microgravity vibration isolation - An algebraic introduction

Certain experiments contemplated for space platforms must be isolated from the accelerations of the platforms. An optimal active control is developed for microgravity vibration isolation, using constant state feedback gains (identical to those obtained from the Linear Quadratic Regulator (LQR) approach) along with constant feedforward (preview) gains. The quadratic cost function for this control algorithm effectively weights external accelerations of the platform disturbances by a factor proportional to (1/omega) (exp 4). Low frequency accelerations (less than 50 Hz) are attenuated by greater than two orders of magnitude. The control relies on the absolute position and velocity feedback of the experiment and the absolute position and velocity feedforward of the platform, and generally derives the stability robustness characteristics quaranteed by the LQR approach to optimality. The method as derived is extendable to the case in which only the relative positions and velocities and the absolute accelerations of the experiment and space platform are available.

Hampton, R. D.↗
NASA NTRS1991

Embryogenic plant cells in microgravity

In view of circumstantial evidence for the role of gravity (g) in shaping the embryo environment, normal embryo development may not occur reliably and efficiently in the microgravity environment of space. Attention must accordingly be given to those aspects of higher plant reproductive biology in space environments required for the production of viable embryos in a 'seed to seed to seed' experiment. It is suggested that cultured cells can be grown to be morphogenetically competent, and can be evaluated as to their ability to simulate embryogenic events usually associated with fertilized eggs in the embryo sac of the ovule in the ovary.

Krikorian, Abraham D.↗
NASA NTRS1992

Microgravity human factors workstation development

Microgravity evaluations of workstation hardware as well as its system components were found to be very useful for determining the expected needs of the Space Station crew and for refining overall workstation design. Research at the Johnson Space Center has been carried out to provide optimal workstation design and human interface. The research included evaluations of hand controller configurations for robots and free flyers, the identification of cursor control device requirements, and the examination of anthropometric issues of workstation design such as reach, viewing distance, and head clearance.

Whitmore, Mihriban↗
NASA NTRS1992

Effects of microgravity on renal stone risk assessment

Physiologic changes induced during human exposure to the microgravity environment of space may contribute to an increased potential for renal stone formation. Renal stone risk factors obtained 10 days before flight and immediately after return to earth indicated that calcium oxalate and uric acid stone-forming potential was increased after space flights of 4-10 days. These data describe the need for examining renal stone risk during in-flight phases of space missions. Because of limited availability of space and refrigerated storage on spacecraft, effective methods must be developed for collecting urine samples in-flight and for preserving (or storing) them at temperatures and under conditions commensurate with mission constraints.

Pietrzyk, R. A.↗
NASA NTRS1992

A review of microgravity surgical investigations

The likelihood of performing a surgical procedure in space will increase as the Soviet Mir space station is expanded and the Space Station Freedom becomes operational. A review of previous research and hardware development, performed mostly in parabolic flight both in the Soviet Union and the U.S., reveals an interest in surgical chambers to prevent cabin atmosphere contamination. Surgical techniques appear to be no more difficult than in a 1-G environment if a restraint system is used. Minimizing the changes of wound infection from the high particle count spacecraft atmosphere is an additional concern. Additional research is necessary to delineate the clinical significance of these problems and to further develop surgical techniques in microgravity.

Campbell, Mark R.↗
NASA NTRS1993

Microwave Dielectrophoretic Levitation In Microgravity

Two reports propose use of dielectrophoresis in microwave resonant cavities to levitate samples of materials for containerless processing in microgravity in vacuum or in any suitable atmosphere. Also describe experiments undertaken to verify feasibility of proposal.

Watkins, John L.↗