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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Thermion: Verification of a thermionic heat pipe in microgravity

The design and development is examined of a small excore heat pipe thermionic space nuclear reactor power system (SEHPTR). The need was identified for an in-space flight demonstration of a solar powered, thermionic heat pipe element. A demonstration would examine its performance and verify its operation in microgravity. The design of a microsatellite based technology demonstration experiment is proposed to measure the effects of microgravity on the performance of an integrated thermionic heat pipe device in low earth orbit. The specific objectives are to verify the operation of the liquid metal heat pipe and the cesium reservior in the space environment. Two design configurations are described; THERMION-I and THERMION-II. THERMION-I is designed for a long lifetime study of the operations of the thermionic heat pipe element in low earth orbit. Heat input to the element is furnished by a large mirror which collects solar energy and focuses it into a cavity containing the heat pipe device. THERMION-II is a much simpler device which is used for short term operation. This experiment remains attached to the Delta II second stage and uses energy from 500 lb of alkaline batteries to supply heat energy to the heat pipe device.

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NASA NTRS1992

Microgravity combustion science: Progress, plans, and opportunities

An earlier overview is updated which introduced the promise of microgravity combustion research and provided a brief survey of results and then current research participants, the available set of reduced gravity facilities, and plans for experimental capabilities in the space station era. Since that time, several research studies have been completed in drop towers and aircraft, and the first space based combustion experiments since Skylab have been conducted on the Shuttle. The microgravity environment enables a new range of experiments to be performed since buoyancy induced flows are nearly eliminated, normally obscured forces and flows may be isolated, gravitational settling or sedimentation is nearly eliminated, and larger time or length scales in experiments are feasible. In addition to new examinations of classical problems, (e.g., droplet burning), current areas of interest include soot formation and weak turbulence, as influenced by gravity.

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NASA NTRS1992

A microgravity vibration isolation rig

It is well known that the spacecraft environment deviates from a state of zero gravity due to various random as well as repetitive sources. Science experiments that require a microgravity environment must therefore be isolated from these disturbances. Active control of noncontact magnetic actuators enables such isolation. A one degree of freedom test rig has been constructed to demonstrate the isolation capability achievable using magnetic actuators. A cylindrical mass on noncontacting electromagnetic supports simulates a microgravity experiment on board an orbiter. Disturbances generated by an electrodynamic shaker are transmitted to the mass via dashpots representing umbilicals. A compact Lorentz actuator has been designed to provide attenuation of this disturbance.

Banerjee, Bibhuti B.↗
NASA NTRS1991

Sample positioning in microgravity

Repulsion forces arising from laser beams are provided to produce mild positioning forces on a sample in microgravity vacuum environments. The system of the preferred embodiment positions samples using a plurality of pulsed lasers providing opposing repulsion forces. The lasers are positioned around the periphery of a confinement area and expanded to create a confinement zone. The grouped laser configuration, in coordination with position sensing devices, creates a feedback servo whereby stable position control of a sample within microgravity environment can be achieved.

Sridharan, Govind↗
NASA NTRS1992

Hollow fiber clinostat for simulating microgravity in cell culture

A clinostat for simulating microgravity on cell systems carried in a fiber fixedly mounted in a rotatable culture vessel is disclosed. The clinostat is rotated horizontally along its longitudinal axis to simulate microgravity or vertically as a control response. Cells are injected into the fiber and the ends of the fiber are sealed and secured to spaced end pieces of a fiber holder assembly which consists of the end pieces, a hollow fiber, a culture vessel, and a tension spring with three alignment pins. The tension spring is positioned around the culture vessel with its ends abutting the end pieces for alignment of the spring. After the fiber is secured, the spring is decompressed to maintain tension on the fiber while it is being rotated. This assures that the fiber remains aligned along the axis of rotation. The fiber assembly is placed in the culture vessel and culture medium is added. The culture vessel is then inserted into the rotatable portion of the clinostat and subjected to rotate at selected rpms. The internal diameter of the hollow fiber determines the distance the cells are from the axis of rotation.

Rhodes, Percy H.↗
NASA NTRS1991

AIAA/IKI Microgravity Science Symposium, 1st, Moscow, USSR, May 13-17, 1991, Proceedings

The state of the art of microgravity science is examined in reviews and reports. Consideration is given to fluid physics; modeling and numerical analysis; crystal growth of electronic materials, proteins, metals, alloys, glasses, and ceramics; biotechnology, combustion science, microgravity hardware, and fundamental phenomena; and education. Particular attention is given to containerless science and technology, a low-gravity two-phase flow with heat transfer, numerical investigation on Benard instability in a finite liquid layer, synthesis and crystallization of refractory compounds from solutions in metallic melts under microgravitation conditions, the long duration protein crystallization experiment aboard the Mir Space Station, directional solidification in immiscible systems, formation of periodic layer structure in oxide melts under different gravity values, opposed flow flame spread in normal, enhanced, and reduced gravity, automatic equipment for semiconductor production in space, and consort and joust sounding rocket missions.

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NASA NTRS1991

Protein crystal growth in microgravity

A series of protein-crystal growth experiments were performed on Space Shuttle flight STS-26 in September 1988 and STS-29 in March 1989. These proteins had been studied extensively in crystal-growth experiments on earth prior to the microgravity experiments. For those proteins which produced crystals of adequate size, 3D intensity data sets with electronic area detector systems were collected. Comparisons show that the microgravity-grown crystals of these proteins are larger, display more uniform morphologies, and yield diffraction data to significantly higher resolutions. Analyses of the 3D data sets indicate that the space-grown crystals are more highly ordered at the molecular level than their earth-grown counterparts.

Snyder, Robert↗
NASA NTRS1991

Operational perspectives for performing microgravity science in orbit

The combination of automation and operator-based technologies is discussed with respect to orbital microgravity experiments in order to optimize the performance and results. A list of five design objectives is presented, and each item is examined in terms of on-orbit flight history to identify relevant examples. It is suggested that human factors be considered in hardware design and that in-flight maintenance operations be considered an integral part of a program. The operational design can produce more effective results when it is established for 'failures' and mission success operations. The design must also be approached in terms of both the limitations and advantages of microgravity. The overarching theme of the investigation is that the mix of automation and operator interaction should be optimized by automating routine tasks and using the operator for critical assessments.

Dunbar, Bonnie J.↗
NASA NTRS1991

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

Attention is given to the Crystal Growth Furnace (CGF) currently in the Level IV integration cycle at the Kennedy Space Center in preparation for its maiden flight on the first United States Microgravity Laboratory (USML-1) mission to be launched in May 1992. CGF was developed for NASA under the Microgravity Science and Application division programs at NASA Headquarters. An overview of the CGF system and the system configuration for the USML-1 mission are presented, and the planned on-orbit experiments are described. The four important scientific experiments selected from industry and educational institutions for the CGF USML-1 mission will enable a better understanding of the complex phenomena inherent in materials processing that will lead to the ultimate improvement of both processes and materials. Crystal growth by chemical vapor transport has resulted in improved growth conditions with crystal morphology, lower defect densities, and higher growth rates than terrestrially observed.

Srinivas, R.↗
NASA NTRS1991

Extinction of a Free Methanol Droplet in Microgravity

The combustion of isolated, unsupported methanol droplets under microgravity conditions has been studied in the NASA-Lewis 2.2-sec drop tower. The substitution of O2/He mixtures for O2/N2 mixtures results in a substantial increase in the oxygen index required for ignition, the rate of gasification, and the diameter at extinction. As a result, droplets with initial size larger than 1 mm can be produced, deployed, ignited, and burned to extinction, all under microgravity conditions in this facility. A comprehensive time dependent numerical model incorporating detailed multicomponent molecular transport mechanisms and complex elementary chemical kinetics was developed and applied to simulate the entire transient droplet combustion processes (ignition/quasi-steady burning/extinction). Model outputs show good agreement with the experimental measurements, without parameter adjustment. Analysis of modeling results shows that the thermal conductivity of the gas phase under combustion environments increased by a factor of two when the 50-percent O2/50 percent He mixture is used instead of air. The increased thermal conductivity accelerates the heat transfer from the flame front to the droplet surface, resulting in a factor of two increase in the burning rate.

Cho, S. Y.↗
NASA NTRS1990

Opposed-flow flame spread with implications for combustion at microgravity

Various regimes of the flame spread phenomenon in an opposing flow environment are classified here depending on the mechanism of flame spread. Simple analyses of energy balances at the tip of the flame are used to complement more sophisticated numerical analysis of the field problem associated with flame spreading in microgravity. The microgravity flames are shown to constitute a separate regime or class by themselves and are discussed in some detail.

Altenkirch, Robert A.↗
NASA NTRS1991

The NASA Microgravity Combustion Space Experiment Program

This paper summarizes the scientific objectives of the expanded microgravity combustion science program including efforts in laminar and turbulent premixed-gas flames, laminar and turbulent gas-jet diffusion flames, droplet combustion, smoldering, flame spreading, pool fires, and metals combustion. Secondly, the paper will summarize the flight hardware that is currently flying and new hardware being proposed to carry out this extensive program of microgravity combustion experiments.

Sacksteder, Kurt↗
NASA NTRS1990

Reaction-compensation technology for microgravity laboratory robots

Robots operating in the microgravity environment of an orbiting laboratory should be capable of manipulating payloads such that the motion of the robot does not disturb adjacent experiments. The current results of a NASA Lewis Research Center technology program to develop smooth, reaction-compensated manipulation based on both mechanism technology and trajectory planning strategies are present. Experimental validation of methods to reduce robot base reactions through the use of redundant degrees of freedom is discussed. Merits of smooth operation roller-driven robot joints for microgravity manipulators are also reviewed.

Rohn, Douglas A.↗
NASA NTRS1992

Self-pressurization of a spherical liquid hydrogen storage tank in a microgravity environment

Thermal stratification and self-pressurization of partially filled liquid hydrogen (LH2) storage tanks under microgravity condition is studied theoretically. A spherical tank is subjected to a uniform and constant wall heat flux. It is assumed that a vapor bubble is located in the tank center such that the liquid-vapor interface and tank wall form two concentric spheres. This vapor bubble represents an idealized configuration of a wetting fluid in microgravity conditions. Dimensionless mass and energy conservation equations for both vapor and liquid regions are numerically solved. Coordinate transformation is used to capture the interface location which changes due to liquid thermal expansion, vapor compression, and mass transfer at liquid-vapor interface. The effects of tank size, liquid fill level, and wall heat flux on the pressure rise and thermal stratification are studied. Liquid thermal expansion tends to cause vapor condensation and wall heat flux tends to cause liquid evaporation at the interface. The combined effects determine the direction of mass transfer at the interface. Liquid superheat increases with increasing wall heat flux and liquid fill level and approaches an asymptotic value.

Lin, C. S.↗
NASA NTRS1992

Transient pool boiling in microgravity

Transient nucleate pool boiling experiments using R113 are conducted for short times in microgravity and in earth gravity with different heater surface orientations and subcoolings. The heating surface is a transparent gold film sputtered on a quartz substrate, which simultaneously provides surface temperature measurements and permits viewing of the boiling process from beneath. For the microgravity experiments, which have uniform initial temperatures and no fluid motion, the temperature distribution in the R 113 at the moment of boiling inception is known. High speed cameras with views both across and through the heating surface record the boiling spread across the heater surface, which is classified into six distinct categories.

Ervin, J. S.↗
NASA NTRS1991

Microgravity science experiment integration - When the PI and the PED differ

This paper addresses issues related to the integration of principal investigators (PIs) and payload-element developers (PEDs) for conducting effective microgravity experiments. The Crystal Growth Furnace (CGF) is used as an example to demonstrate the key issues related to the integration of a PI's sample into a facility run by a different organization. Attention is given to the typical preflight timeline, documentation required for experimental implementation, and hardware deliverables. A flow chart delineates the payload-integration process flow, and PI inputs required for an experiment include equipment and procedure definitions, detailed design and fabrication of the experiment-specific equipment, and specifications of the contract-end item. The present analysis is of interest to the coordination of effective microgravity experiments on the Space Station Freedom that incorporate PIs and PEDs from different organizations.

Baer-Peckham, M. S.↗
NASA NTRS1991

Microgravity and the lung

Results are presented from studies of the effect of microgravity on the lungs of rats flown on the Cosmos 2044 mission, and from relevant laboratory experiments. The effects of microgravity fall into five categories: topographical structure and function, the lung volumes and mechanics, the intrathoracic blood pressures and volumes, the pulmonary deposition of aerosol, and denitrogenaton during EVA. The ultrastructure of the left lungs of rats flown for 14 days on the Cosmos 2044 spacecraft and that of some tail-suspended rats disclosed presence of red blood cells in the alveolar spaces, indicating that pulmonary hemorrhage and pulmonary edema occurred in these rats. Possible causes for this phenomenon are discussed.

West, John B.↗
NASA NTRS1992

Cosmic dust analogue material condensation in microgravity: The Stardust programme - First results and future activities

Initial results are presented from airborne experiments investigating the vapor phase condensation in microgravity, carried out in the framework of the Stardust international program. Special attention is given to the design and operation of the experimental equipment, which includes the furnace for producing vapors from different materials and the cloud chamber in which the vapor nucleation occurs. A two-part mathematical model was developed to describe the transport processes in the nucleation chamber. Results obtained from three experimental series were conducted with Mg and Zn aboard NASA's KC-135 reduced-gravity research aircraft showed that nucleation front (smoke cloud) was quite different in appearance in microgravity from that typically observed at 1-g condition. The Mg and Zn particles exhibited significant differences in shape; there was some evidence of coagulation.

Ferguson, F.↗