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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Gravity Effects Observed In Partially Premixed Flames

Partially premixed flames (PPFs) contain a rich premixed fuel air mixture in a pocket or stream, and, for complete combustion to occur, they require the transport of oxidizer from an appropriately oxidizer-rich (or fuel-lean) mixture that is present in another pocket or stream. Partial oxidation reactions occur in fuel-rich portions of the mixture and any remaining unburned fuel and/or intermediate species are consumed in the oxidizer-rich portions. Partial premixing, therefore, represents that condition when the equivalence ratio (phi) in one portion of the flowfield is greater than unity, and in another section its value is less than unity. In general, for combustion to occur efficiently, the global equivalence ratio is in the range fuel-lean to stoichiometric. These flames can be established by design by placing a fuel-rich mixture in contact with a fuel-lean mixture, but they also occur otherwise in many practical systems, which include nonpremixed lifted flames, turbulent nonpremixed combustion, spray flames, and unwanted fires. Other practical applications of PPFs are reported elsewhere. Although extensive experimental studies have been conducted on premixed and nonpremixed flames under microgravity, there is a absence of previous experimental work on burner stabilized PPFs in this regard. Previous numerical studies by our group employing a detailed numerical model showed gravity effects to be significant on the PPF structure. We report on the results of microgravity experiments conducted on two-dimensional (established on a Wolfhard-Parker slot burner) and axisymmetric flames (on a coannular burner) that were investigated in a self-contained multipurpose rig. Thermocouple and radiometer data were also used to characterize the thermal transport in the flame.

Puri, Ishwar K.↗
NASA NTRS1992

Gravity effects on cellulose assembly

The effect of microgravity on cellulose synthesis using the model system of Acetobacter xylinum was the subject of recent investigations using The National Aeronautics and Space Administration's Reduced Gravity Laboratory, a modified KC-135 aircraft designed to produce 20 sec of microgravity during the top of a parabolic dive. Approximately 40 parabolas were executed per mission, and a period of 2 x g was integral to the pullout phase of each parabola. Cellulose biosynthesis was initiated on agar surfaces, liquid growth medium, and buffered glucose during parabolic flight and terminated with 2.0% sodium azide or 50.0% ethanol. While careful ground and in-flight controls indicated normal, compact ribbons of microbial cellulose, data from five different flights consistently showed that during progression into the parabola regime, the cellulose ribbons became splayed. This observation suggests that some element of the parabola (the 20 sec microgravity phase, the 20 sec 2 x g phase, or a combination of both) was responsible for this effect. Presumably the cellulose I alpha crystalline polymorph normally is produced under strain, and the microgravity/hypergravity combination may relieve this stress to produce splayed ribbons. An in-flight video microscopy analysis of bacterial motions during a parabolic series demonstrated that the bacteria continue to synthesize cellulose during all phases of the parabolic series. Thus, the splaying may be a reflection of a more subtle alteration such as reduction of intermicrofibrillar hydrogen bonding. Long-term microgravity exposures during spaceflight will be necessary to fully understand the cellulose alterations from the short-term microgravity experiments.

manned↗
NASA NTRS2004

Exploring Space on the Computer

For the past year Dennis Stocker has been in the process of developing pencil and paper games, which are fun, challenging, and educational for middle school and high school students. The latest version of these pencil and paper games is Spaceship Commander. The objective of the game is to earn points by plotting the flight path of a spaceship so astronauts can perform microgravity experiments, and make short-range measurements of other planets. During my ten weeks here at the GRC my goal is to create a computer based version of Spaceship commander. During the development of this game the primary focus has been on making it as educational and fun for the student as possible. The main educational objective of this game is to give students an understanding of forces and motion, including gravity. This is done by incorporating Newton's laws into the game. For example a spacecraft in the video game experiences a gravitational force applied to it by planets. The software I am using to create this game is a freeware application called Game Maker. Game Maker allows novice computer programmers like me to create arcade style games using a visual drag and drop interface. By using functions provided by Game Maker and a few I have written myself, I have been able to create a few simple computer games. Currently the computer game allows the student to navigate a space ship around planets, and asteroids by using the arrow keys on the numeric keypad. Each time an arrow key is pressed by the student the corresponding acceleration of the space ship is seen on the screen. Points are earned by navigating the space ship close enough to planets to gather scientific data. However the game encourages the student to plan his or her course carefully, because if the student gets too close to a planet they may not be able to escape the planet s gravity, and crash into the planet. The next step in the game development is to include a launch sequence which allows the student to launch from their home planet at a speed and direction determined by the student. Additional information is included in the original extended abstract.

Bozym, Patrick↗
NASA NTRS2010

Visual Impairment and Intracranial Hypertension: An Emerging Spaceflight Risk

What is the risk? Given that astronauts exposed to microgravity experience a cephalad fluid shift, and that both symptomatic and asymptomatic astronauts have exhibited optic nerve sheath edema on MRI, there is a high probability that all astronauts have some degree of increased intracranial pressure (ICP; intracranial hypertension), and that those susceptible (via eye architecture, anatomy, narrow optic disc) have a high likelihood of developing papilledema (optic disc edema, globe flattening), choroidal folds, and/or hyperopic shifts and that the degree of edema may determine long-term or permanent vision impairment or loss. Back to back panels on this topic have been developed to address this emerging risk. The first panel will focus on the 6 clinical cases with emphasis on ophthalmic findings and imaging techniques used pre-, in-, and post-flight. The second panel will discuss the operational mitigation and medical requirements, the potential role of CO2 on ISS, and the research approach being developed. In total these back to back panels will explore what is known about this risk, what has been done immediately to address it, and how an integrated research model is being developed.

Fogarty, Jennifer A.↗
NASA NTRS2010

NASA's Spaceflight Visual Impairment and Intracranial Hypertension Research Plan: An accelerated Research Collaboration

To date six long duration astronauts have experienced in flight visual changes and post flight signs of optic disc edema, globe flattening, choroidal folds, hyperoptic shifts and or raised intracranial pressure. In some cases the changes were transient while in others they are persistent with varying degrees of visual impairment. Given that all astronauts exposed to microgravity experience a cephalad fluid shift, and that both symptomatic and asymptomatic patients have exhibited optic nerve sheath edema on MRI, there is a high probability that all astronauts develop in-flight idiopathic intracranial hypertension to some degree. Those who are susceptible, have an increased likelihood of developing treatment resistant papilledema resulting in visual impairment and possible long-term vision loss. Such an acquired disability would have a profound mission impact and would be detrimental to the long term health of the astronaut. The visual impairment and increased intracranial pressure phenomenon appears to have multiple contributing factors. Consequently, the working "physiological fault bush" with elevated intracranial pressure at its center, is divided into ocular effects, and CNS and other effects. Some of these variables have been documented and or measured through operational data gathering, while others are unknown, undocumented and or hypothetical. Both the complexity of the problem and the urgency to find a solution require that a unique, non-traditional research model be employed such as the Accelerated Research Collaboration(TM) (ARC) model that has been pioneered by the Myelin Repair Foundation. In the ARC model a single entity facilitates and manages all aspects of the basic, translational, and clinical research, providing expert oversight for both scientific and managerial efforts. The result is a comprehensive research plan executed by a multidisciplinary team and the elimination of stove-piped research. The ARC model emphasizes efficient and effective communication between management and investigators; and real-time sharing of scientific discoveries in an effort to solve complex problems.

Otto, Christian↗
NASA NTRS2011

On Transients in Detached Bridgman Growth

In detached Bridgman growth, a gap exists between the growing crystal and the crucible wall. According to crystal shape stability theory, only specific gap widths will be dynamically stable. Beginning with a crystal diameter that differs from stable conditions, the transient crystal growth process is analyzed. The transient shapes are calculated assuming that the growth angle is constant. Anisotropy and dynamic contact angle effects are considered. In microgravity, dynamic stability depends only on capillary effects and is decoupled from heat transfer. However, heat transfer will influence the crystal-melt interface shape. The local angles and the crystal-melt-vapor triple junction are analyzed and the applicability of the Herring formula is discussed. A potential microgravity experiment is proposed which would enhance our understanding of the detached growth dynamic stability problem.

Mazuruk, K.↗
NASA NTRS1994

DYNAMX: A Low Temperature Microgravity Investigation of Phase Transitions

The Critical Dynamics in Microgravity Experiment, DYNAMX, will investigate the effects on the superfluid transition in 4 He of currents generated by heat flow, measuring the thermal conductivity in the fluid as a function of applied heat. DYNAMX will also take advantage of the weightless environment to measure the conductivity properties in the region of the interface between the two phases. Thus, DYNAMX represents an experiment that will explore a system driven far from equilibrium. This paper will describe the science objectives, the current design of the experiment apparatus, the steps being taken to prepare this experiment for flight, and the results of ground-based feasibility demonstrations now underway.

superfluid↗
NASA NTRS1993

NASA Ultra-Sensitive Miniature Accelerometer

Using micro-machined silicon technology, an ultra-sensitive miniature accelerometer can be constructed which meets the requirements for microgravity experiments in the space environment. Such an accelerometer will have a full scale sensitivity of 10 -2 g, a resolution of 10 -8 g, low cross-axis sensitivity, and low temperature sensitivity. Mass of the device is approximately five grams and its footprint is 2 cm x 2 cm.

miniature↗
NASA NTRSDate not supplied

Experimental, Computational, Theoretical and Analytical Investigation of Flow Boiling in Reduced Gravity

Two-phase thermal management systems are far superior to their single-phase counterparts because of their ability to capitalize on the coolant’s both sensible and latent heats, thereby yielding orders of magnitude higher heat transfer coefficients and smaller system footprints. A vital knowledge necessary for their implementation in future space systems is performance in microgravity. Long-duration microgravity experiments are necessary to obtain reliable databases, which would then be used to build reliable predictive tools. To achieve this goal, investigators at the Purdue University Boiling and Two-Phase Flow Laboratory (PU-BTPFL) and the NASA Glenn Research Center (NASA-GRC) have been collaborating towards the development of the Flow Boiling and Condensation Experiment (FBCE) and eventual execution onboard the International Space Station (ISS). FBCE has now matured to a point where it is ready for transport to the ISS, where first tests will be conducted using the Flow Boiling Module (FBM). In preparation for the ISS tests, a series of pre-launch Mission Sequence Tests (MSTs) was performed at GRC in Earth gravity with FBM mounted in a vertical upflow orientation using n-perfluorohexane as working fluid. The pre-launch tests included variations of flow rate, surface heat flux, inlet conditions, and both single-sided and double-sided wall heating. This presentation will summarize experimental results from these tests as well as both analytic and theoretical tools for prediction of two-phase heat transfer coefficient and critical heat flux (CHF). Also discussed will be an assessment of predictive accuracy of these tools against the experimental data.

Mission Sequence tests↗
NASA NTRSDate not supplied

Extinction of the Stagnation Point Diffusion Flame: Effect of Conductive Heat Loss into Solid Interior

The planned microgravity experiment Growth and Extinction Limit (GEL) is designed to study the material flammability and extinction of thermally thick solid with an emphasis to quantify the effect of conductive heat loss into the solid interior by measuring the in-depth temperature profile. To obtain a more detailed understanding of the extinction phenomena, a previously developed one-dimensional axisymmetric stagnation-point diffusion flame model is expanded to account for the excessive heat loss into the solid beyond the steady burning state. This is important because for thick solids, this is important because the burning period can have a long and slow solid transient with a quasi-steady gas -phase. A non-dimensional excessive conductive heat loss parameter Ψ is defined in the paper and extensive numerical computations have been performed to determine the extinction boundary and the characteristics of near-limit flames. The classical U-shaped flammability boundary in the oxygen vs. stretch rate plot now becomes a series of U-shaped boundaries as a function of Ψ. For a given oxygen ambient, extinction boundary is a function of Ψ. The boundary consists of a blowoff branch and a radiative quenching branch. This is similar to the steady burning flammability boundary (Ψ =0) in the oxygen vs stretch rate plot. Extensive computed data including flame and pyrolysis temperatures, burning rate, flame standoff distance, and reaction rate are presented along the extinction boundaries. In particular, we note that the non-dimensional gas reaction rate is the ratio of diffusion reaction time to the reaction diffusion time, so it has the classical Damhkoler number character. By examining the maximum non-dimensional reaction rates, we observe that along the extinction boundaries, they are approximate constant across the entire range of stretch rates (from quenching to blow-off). These critical values are of the order unity but may vary in different oxygen ambient. The implication will be discussed in the presentation together with the near-limit flame structures.

Chengyao Li↗
NASA NTRSDate not supplied

Structural Requirements and Scaling Analysis of a Fluidic Mirror Space Telescope Support Structure

The NASA FLUTE project proposes large-scale (50m) fluidic telescopes for astronomy applications. To continue to explore the universe, astronomers require larger and larger telescope apertures. The highest priority astrophysics targets such as exoplanets and early galaxies are extremely faint, motivating larger telescope apertures. However, mission costs depend on aperture diameter, and scaling apertures beyond 10-m apertures faces economic and technological viability challenges. An unsegmented primary mirror made in space via fluidic microgravity shaping would provide a scalable and cost-effective method to scale apertures to 50-m scale while achieving sub-nanometer (root mean square) surface quality. Such microgravity fluidic shaping has been demonstrated in laboratory neutral buoyance environments, parabolic microgravity experiments, as well aboard the International Space Station. One of the main components of a fluidic observatory is the mirror frame. The frame must provide a stable bounding circular ring which the edges of the fluid mirror surface can wet. The frame can optionally provide a ‘floor’ surface on the interior of the ring to provide additional fluid support and reduce required fluid volume. In this work, we evaluate several classes of structural frame architectures potentially suitable for a fluidic telescope support structure. We start by estimating stability requirements, orbital, station keeping, and slew loads based on a notional CONOPS. The scaling of overall fluid mass required for each architecture is evaluated. Preliminary results elucidate the importance of a support floor for overall mission viability above 10-m diameter. We then investigate the scaling of a tetrahedral truss frame support structure. We show that segmented solid shell support surfaces can provide sufficient stability at modest mass fractions. We estimate that the total fluid and frame mass for a 50-m telescope could be on the order of 15,000 kg. Finally, implementation considerations are discussed, including deployment/assembly methodologies. The results of this study establish feasibility of a large-scale fluidic telescope and will guide further architecture development and detailed structural design.

Christine Gregg↗
NASA NTRS2002

DMA Modulus as a Screening Parameter for Compatibility of Polymeric Containment Materials with Various Solutions for use in Space Shuttle Microgravity Protein Crystal Growth (PCG) Experiments

Protein crystals are grown in microgravity experiments inside the Space Shuttle during orbit. Such crystals are basically grown in a five-component system containing a salt, buffer, polymer, organic and water. During these experiments, a number of different polymeric containment materials must be compatible with up to hundreds of different PCG solutions in various concentrations for durations up to 180 days. When such compatibility experiments are performed at NASA/MSFC (Marshall Space Flight Center) simultaneously on containment material samples immersed in various solutions in vials, the samples are rather small out of necessity. DMA4 modulus was often used as the primary screening parameter for such small samples as a pass/fail criterion for incompatibility issues. In particular, the TA Instruments DMA 2980 film tension clamp was used to test rubber O-rings as small in I.D. as 0.091 in. by cutting through the cross-section at one place, then clamping the stretched linear cord stock at each end. The film tension clamp was also used to successfully test short length samples of medical/surgical grade tubing with an O.D. of 0.125 in.

Wingard, Charles Doug↗
NASA NTRS1986

Nucleation experiments in a microgravity environment

A simple experimental apparatus is described in which a wide variety of vapor phase nucleation studies of refractory materials could be performed aboard NASA's KC-135 Research Aircraft. The chief advantage of a microgravity environment for these studies is the expected absence of thermally driven convective motions in the gas. The absence of convection leads to much more accurate knowledge of both the temperature distribution in the system and the time evolution of the refractory vapor concentration as a function of distance from the crucible.The evolution of the apparatus will be described as more experience is gained with the microgravity environment. Such experiments will be used to prepare for similar ones carried out aboard either the shuttle or Space Station where considerably longer duration experiments are possible.

Nuth, J. A.↗
NASA NTRS2004

Design of a Microgravity Spray Cooling Experiment

An analytical and experimental study was conducted for the application of spray cooling in a microgravity and high-g environment. Experiments were carried out aboard the NASA KC-135 reduced gravity aircraft, which provided the microgravity and high-g environments. In reduced gravity, surface tension flow was observed around the spray nozzle, due to unconstrained liquid in the test chamber and flow reversal at the heat source. A transient analytical model was developed to predict the temperature and the spray heat transfer coefficient within the heated region. Comparison of the experimental transient temperature variation with analytical results showed good agreement for low heat input values. The transient analysis also verified that thermal equilibrium within the heated region could be reached during the 20-25s reduced gravity portion of the flight profile.

Baysinger, Kerri M.↗
NASA NTRS1998

Microgravity Materials and Biotechnology Experiments

Presentation will deal with an overview of the Materials Science and Biotechnology/Crystal Growth flight experiments and their requirements for a successful execution. It will also deal with the hardware necessary to perform these experiments as well as the hardware requirements. This information will serve as a basis for the Abstract: workshop participants to review the poss7ibilifies for a low cost unmanned carrier and the simple automation to carry-out experiments in a microgravity environment with little intervention from the ground. The discussion will include what we have now and what will be needed to automate totally the hardware and experiment protocol at relatively low cost.

Vlasse, Marcus↗
NASA NTRS1987

Containerless high-pressure petrology experiments in the microgravity environment of the Space Station

The genesis of igneous rocks on terrestrial planets can only be understood through experiments at pressures corresponding to those in planetary mantles (10 to 50 kbar). Such experiments typically require a piston-cylinder apparatus, and an apparatus that has the advantage of controllable pressure and temperature, adequate sample volume, rapid sample quench, and minimal danger of catastrophic failure. It is proposed to perform high-pressure and high-temperature piston-cylinder experiments aboard the Space Station. The microgravity environment in the Space Station will minimize settling due to density contrasts and may, thus, allow experiments of moderate duration to be performed without a platinoid capsule and without the sample having to touch the container walls. The ideal pressure medium would have the same temperatures. It is emphasized, however, that this proposed experimental capability requires technological advances and innovations not currently available.

Boynton, W. V.↗
NASA NTRS1999

Material Science Experiments on Mir

This paper describes the microgravity materials experiments carried out on the Shuttle/Mir program. There were six experiments, all of which investigated some aspect of diffusivity in liquid melts. The Liquid Metal Diffusion (LMD) experiment investigated the diffusivity of molten Indium samples at 185 C using a radioactive tracer, In-114m. By monitoring two different gamma ray energies (190 keV and 24 keV) emitted by the samples it was possible to measure independently the diffusion rates in the bulk and at the surface of the samples. The Queens University Experiment in Liquid Diffusion (QUELD) was the furnace facility used to process 213 samples for the five other experiments. These experiments investigated the diffusion, ripening, crystal growth, and glass formation in metal, semiconductor, and glass samples. This facility had the capability to process samples in an isothermal or gradient configuration for varying periods of time at temperatures up to 900 C. Both the LMD and the QUELD furnaces were mounted on the Microgravity Isolation Mount (MIM) which provided isolation from g-jitter. All the microgravity experiments were supported by the Space Acceleration Measurement System (SAMS); a three head three axes acceleration monitoring system which measured and recorded the acceleration environment.

Kroes, Roger L.↗