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NASA NTRS1998

Internal Flows in Free Drops (IFFD)

Within the framework of an Earth-based research task investigating the internal flows within freely levitated drops, a low-gravity technology development experiment has been designed and carried out within the NASA Glovebox facility during the STS-83 and STS-94 Shuttle flights (MSL-1 mission). The goal was narrowly defined as the assessment of the capabilities of a resonant single-axis ultrasonic levitator to stably position free drops in the Shuttle environment with a precision required for the detailed measurement of internal flows. The results of this entirely crew-operated investigation indicate that the approach is fundamentally sound, but also that the ultimate stability of the positioning is highly dependent on the residual acceleration characteristic of the Spacecraft, and to a certain extent, on the initial drop deployment of the drop. The principal results are: the measured dependence of the residual drop rotation and equilibrium drop shape on the ultrasonic power level, the experimental evaluation of the typical drop translational stability in a realistic low-gravity environment, and the semi-quantitative evaluation of background internal flows within quasi-isothermal drops. Based on these results, we conclude that the successful design of a full-scale Microgravity experiment is possible, and would allow accurate the measurement of thermocapillary flows within transparent drops. The need has been demonstrated, however, for the capability for accurately deploying the drop, for a quiescent environment, and for precise mechanical adjustments of the levitator.

Trinh, E. H.↗

NASA NTRS1998

Third United States Microgravity Payload: One Year Report

This document reports the one year science results for the Third United States Microgravity Payload (USMP-3). The USMP-3 major experiments were on a support structure in the Space Shuttle's payload bay and operated almost completely by the Principal Investigators through telescience. The mission included a Glovebox where the crew performed additional experiments for the investigators. Together about seven major scientific experiments were performed, advancing the state of knowledge in fields such as low temperature physics, solidification, and combustion. The results demonstrate the range of quality science that can be conducted utilizing orbital laboratories in microgravity and provide a look forward to a highly productive space station era.

Currieri, P. A.↗

NASA NTRS1998

Radiative Ignition and Transition to Spread Investigation (RITSI)

A total of 25 experiments was conducted in the Glovebox Facility on the Third United States Microgravity payload (USMP3) mission to study the behavior of both flaming and smoldering ignition events, the transition from ignition to the flame/smoldering spread, and the flame/smoldering growth pattern in air. Twenty one of the 25 experiments were flaming experiments and the remainder were smoldering experiments. Ignition was initiated by a heated wire across a thermally thin filter paper in the middle of the sample for the two-dimensional configuration and by a focused beam from a halogen/tungsten lamp at the center of the sample for the three-dimensional configuration. The external air flow velocity was varied from 0 cm/s to 6.5 cm/s. The ignition and subsequent flame spread events were recorded by a video camera, a 35 mm camera, and 6 thermocouples (2 in the gas phase and 4 in the sample). The results indicate that non-piloted radiative ignition of the paper by external thermal radiation tends to occur more easily than in normal gravity. In the two-dimensional configuration, the transition from ignition to downstream flame spread never occurred; only the transition to upstream spread took place. In the three-dimensional configuration, a char growth pattern emerged in the shape of a fan, with the ignited area as the center of the fan and the fan spreading in the upstream direction. The internal angle of the fan increased with an increase in external flow velocity (higher flow velocity gave a more opened fan pattern). At an external flow velocity of 5 cm/s, the flame was horseshoe-shaped and the char pattern became an elongated semicircle toward upstream. It appears that the peak upstream flame spread rate was reached at a higher external velocity than for the two-dimensional flame front. Flame spread much faster along open edges of the sample paper than along the sample face, presumably due to there being larger supply of oxygen and energy feedback at the open edges than at the surface. These results indicate the possible importance of the effect of the flame front shape such as the curvature of the flame front on spread rate and flame strength. A complex, unexpected finger-shaped char growth pattern was observed during the smoldering experiment. Higher external flow velocity increased the number of localized smoldering fronts, of the char fingers they left behind, and frequency of bifurcations from the fingers. At present, it is not clear what caused such a complex char growth pattern.

Kashiwagi, Takashi↗

NASA NTRS1998

Comparative Soot Diagnostics: 1 Year Report

The motivation for the Comparative Soot Diagnostics (CSD) experiment lies in the broad practical importance of understanding combustion generated particulate. Depending upon the circumstances, particulate matter can affect the durability and performance of combustion equipment, can be a pollutant, can be used to detect fires and, in the form of soot, can be the dominant source of radiant energy from flames. Bright sooty fires are desirable for efficient energy extraction in furnaces and power equipment. In contrast, soot-enhanced radiation is undesirable in many propulsion systems (e.g. jet engines). The non-buoyant structure of most flames of practical interest (turbulent) makes understanding of soot processes in low gravity flames important to our ability to predict fire behavior on earth. These studies also have direct applications to fire safety in human-crew spacecraft, since smoke is the indicator used for automated detection in current spacecraft. In addition, recent tests conducted on MIR showed that a candle in a truly quiescent spacecraft environment can burn for tens of minutes. Consequently, this test and many earlier tests have demonstrated that fires in spacecraft can be considered a credible risk. In anticipation of this risk, NASA has included fire detectors on Skylab, smoke detectors on the Space Shuttle (STS), and smoke detectors in the design for the International Space Station (ISS). In the CSD experiment, these smoke detectors were tested using, quasi-steady, low-gravity, particulate generating materials. Samples of the particulate were also obtained from these low-gravity sources. This experiment provides the first such measurements aimed toward understanding of soot processes here on earth and for the testing and design of advanced spacecraft smoke detection systems. This paper describes the operation and preliminary results of the CSD experiment which was was conducted in the Middeck Glovebox Facility (MGBX) on USMP-3. The objectives of CSD are to examine the particulate emission from a variety of pyrolyzing and combusting sources and to quantify the performance of several particulate-sensing diagnostic techniques. This paper presents the results of the microgravity portion of the CSD experiment. The results include the temporal response of the detectors and average sizes of the primary and aggregate particles captured on the thermophoretic probes. Complete assessment of the microgravity data and its combination with the normal-gravity data are still in process.

Urban, David L.↗

NASA NTRS1999

Some Recent Observations on the Burning of Isolated N-Heptane and Alcohol Droplets

In a joint program involving Prof F.A. Williams of the University of California, San Diego and Dr. Vedha Nayagam of the National Center for Microgravity Research on Fluid and Combustion, the combustion of liquid fuel droplets having initial diameters between about 1 mm and 6 mm is being studied. The objectives of the work are to improve fundamental knowledge of droplet combustion dynamics through microgravity experiments and theoretical analyses. The Princeton contributions to the collaborative program supports the engineering design, data analysis, and data interpretation requirements for the study of initially single component, spherically symmetric, isolated droplet combustion studies through experiments and numerical modeling. The complementary UCSD contributions apply asymptotic theoretical analyses and are described in the published literature and in a companion communication in this volume. Emphases of the Princeton work are on the study of simple alcohols (methanol, ethanol), alcohol/water mixtures, and pure alkanes (n-heptane, n-decane) as fuels, with time dependent measurements of drop size, flame-stand-off, liquid-phase composition, and finally, extinction. Ground based experiments have included bench-scale studies at Princeton and collaborative experimental studies in the 2.2 and 5.18 second drop towers at NASA-Glenn Research Center. Spacelab studies have included fiber-supported droplet combustion (FSDC) experiments in the Glovebox facility with accompanying numerical analyses. Experiments include FSDC-1, performed on the USML-2 mission in October, 1995 (STS-73) and FSDC-2, on the second flight of the MSL-1 mission in July, 1997 (STS-94).

Dryer, F. L.↗

NASA NTRS1999

Fourth United States Microgravity Payload: One Year Report

This document reports the one year science results for the Fourth United States Microgravity Payload (USMP-4). The USMP-4 major experiments were on a support structure in the Space Shuttle's payload bay and operated almost completely by the Principal Investigators through telescience. The mission included a Glovebox where the crew performed additional experiments for the investigators. Together about eight major scientific experiments were performed, advancing the state of knowledge in fields such as low temperature physics, solidification, and combustion. The results demonstrate the range of quality science that can be conducted utilizing orbital laboratories in microgravity and provide a look forward to a highly productive Space Station era.

Ethridge, Edwin C.↗

NASA NTRS1999

Muscle Deoxygenation Causes Muscle Fatigue

Muscle fatigue is a common musculoskeletal disorder in the work place, and may be a harbinger for more disabling cumulative trauma disorders. Although the cause of fatigue is multifactorial, reduced blood flow and muscle oxygenation may be the primary factor in causing muscle fatigue during low intensity muscle exertion. Muscle fatigue is defined as a reduction in muscle force production, and also occurs among astronauts who are subjected to postural constraints while performing lengthy, repetitive tasks. The objectives of this research are to: 1) develop an objective tool to study the role of decreased muscle oxygenation on muscle force production, and 2) to evaluate muscle fatigue during prolonged glovebox work.

Murthy, G.↗

NASA NTRS1999

Fourth United States Microgravity Payload: One Year Report

Ethridge, E. C.↗

NASA NTRS2000

Microgravity Vibration Isolation for the International Space Station

The International Space Station (ISS) is being envisioned as a laboratory for experiments in numerous microgravity (micrograms) science disciplines. Predictions of the ISS acceleration environment indicate that the ambient acceleration levels ill exceed levels that can be tolerated by the science experiments. Hence, microgravity vibration isolation systems are being developed to attenuate the accelerations to acceptable levels. While passive isolation systems are beneficial in certain applications, active isolation systems are required to provide attenuation at low frequencies and to mitigate directly induced payload disturbances. To date, three active isolation systems have been successfully tested in the orbital environment. A fourth system called g-LIMIT is currently being developed for the Microgravity Science Glovebox and is manifested for launch on the UF-1 mission. This paper presents an overview of microgravity vibration isolation technology and the g-LIMIT system in particular.

Whorton, Mark S.↗

NASA NTRS2000

Microgravity Research Results and Experiences from the NASA Mir Space Station Program

The Microgravity Research Program Office (MRPO) participated aggressively in Phase I of the International Space Station Program using the Russian Mir Space Station. The Mir Station offered an otherwise unavailable opportunity to explore the advantages and challenges to long duration microgravity space research. Payloads with both NASA and commercial backing were included as well as cooperative research with the Canadian Space Agency (CSA). From this experience, much was learned about dealing with long duration on orbit science utilization and developing new working relationships with our Russian partner to promote efficient planning, operations, and integration to solve complexities associated with a multiple partner program. Microgravity participation in the NASA Mir Program began with the first joint NASA Mir flight to the Mir Space Station. The earliest participation setup acceleration measurement capabilities that were used throughout the Program. Research, conducted by all Microgravity science disciplines, continued on each subsequent increment for the entire three-year duration of the Program. The Phase I Program included the Microgravity participation of over 30 Fluids, Combustion, Materials, and Biotechnology Sciences and numerous commercially sponsored research payloads. In addition to the research gained from Microgravity investigations, long duration operation of facility hardware was tested. Microgravity facilities operated on Mir included the Space Acceleration Measurement System (SAMS), the Microgravity Glovebox (MGBX), the Biotechnology System (BTS) and the Canadian Space Agency sponsored Microgravity Isolation Mount (MIM). The Russian OPTIZONE Furnace was also incorporated into our material science research. All of these efforts yielded significant and useful scientific research data. This paper focuses on the microgravity research conducted onboard the Mir space station. It includes the Program preparation and planning necessary to support this type of cross increment research experience; the payloads which were flown; and summaries of significant microgravity science findings. Most importantly this paper highlights the various disciplines of microgravity research conducted during the International Space Station, Phase 1 Program onboard the Mir Station. A capsulation of significant research and the applicability of our findings are provided. In addition, a brief discussion of how future microgravity science gathering capabilities, hardware development and payload operations techniques have enhanced our ability to conduct long duration microgravity research.

Schagheck, R. A.↗

NASA NTRS2000

Design and Analysis of Precise Pointing Systems

The mathematical models of Glovebox Integrated Microgravity Isolation Technology (g- LIMIT) dynamics/control system, which include six degrees of freedom (DOF) equations of motion, mathematical models of position sensors, accelerometers and actuators, and acceleration and position controller, were developed using MATLAB and TREETOPS simulations. Optimal control parameters of G-LIMIT control system were determined through sensitivity studies and its performance were evaluated with the TREETOPS model of G-LIMIT dynamics and control system. The functional operation and performance of the Tektronix DTM920 digital thermometer were studied and the inputs to the crew procedures and training of the DTM920 were documented.

Kim, Young K.↗

NASA NTRS2000

Mechanisms for the Crystallization of ZBLAN

A number of research teams have observed that glass forming melts that are solidified in low-g exhibit enhanced glass formation. This project will examine one of these glasses, the heavy metal fluoride glass ZBLAN. A four year ground based research program has been approved to examine the crystallization of ZBLAN glasses with the purpose of testing a theory for the crystallization of ZBLAN glass. The theory could explain the general observations of enhanced glass formation of other glasses melted and solidified in low-g. Fluid flow in 1-g results from buoyancy forces and surface tension driven convection. This fluid flow can introduce shear in undercooled liquids in 1-g. In low-g it is known that fluid flows are greatly reduced so that the shear rate in fluids in low-g are extremely low. It is believed that fluids may have some weak structure in the absence of flow. Even very small shear rates could cause this structure to collapse in response to the shear. A general result would be shear thinning of the fluid. The hypothesis of this research is that: Shear thinning in undercooled liquids increases the rate of nucleation and crystallization of glass forming melts. Shear of the melt can be reduced in low-g enhancing undercooling and glass formation. Samples will be melted and quenched in 1-g under quiescent conditions at a number of controlled cooling rates to determine times and temperatures of crystallization and heated at controlled heating rates to determine kinetic crystallization parameters. Experiments will also be performed on the materials while under controlled vibration conditions and compared with the quiescent experiments in order to evaluate the effect of shear in the liquid on crystallization kinetics. After the experimental parameters are well known, experiments will be repeated under low-g (and 2-g) conditions on the KC-135 aircraft during low-g parabolic maneuvers. The results will determine the effects of shear on crystallization. Our experimental setups will be designed with low-g experiments in mind and will be tested as breadboard low-g experiments. It is very likely that the thermal analysis instrumentation can be adapted to be run in the microgravity glovebox facilities. Critical space experiments may result to test the theory at longer low-g time experiments in space.

Ethridge, Edwin C.↗

NASA NTRS1999

Ground-Based Studies of Thermocapillary Flows in Levitated Laser-Heated Drops

The fluid flow phenomena are studied together with the thermal effects on drops levitated in acoustic and/or electrostatic fields. While the study is concerned primarily with particles in strong acoustic fields to overcome gravity, some results for microgravity have also been obtained. The study also includes an analysis and an experimental investigation of the thermocapillary flow in a spot-heated drop. Results of a Glovebox experiment on the MSL-1 mission, one of whose objectives was to evaluate the acoustic stability criteria in microgravity, are also discussed.

Sadhai, S. S.↗

NASA NTRS2000

Clean and Cold Sample Curation

Curation of Mars samples includes both samples that are returned to Earth, and samples that are collected, examined, and archived on Mars. Both kinds of curation operations will require careful planning to ensure that the samples are not contaminated by the instruments that are used to collect and contain them. In both cases, sample examination and subdivision must take place in an environment that is organically, inorganically, and biologically clean. Some samples will need to be prepared for analysis under ultra-clean or cryogenic conditions. Inorganic and biological cleanliness are achievable separately by cleanroom and biosafety lab techniques. Organic cleanliness to the <50 ng/sq cm level requires material control and sorbent removal - techniques being applied in our Class 10 cleanrooms and sample processing gloveboxes.

Allen, C. C.↗

NASA NTRS2001

A New Direction for NASA Materials Science Research Using the International Space Station

NASA recently created a fifth Strategic Enterprise, the Office of Biological and Physical Research (OBPR), to bring together physics, chemistry, biology, and engineering to foster interdisciplinary research. The Materials Science Program is one of five Microgravity Research disciplines within this new enterprise's Division of Physical Sciences Research. The Materials Science Program will participate within this new enterprise structure in order to facilitate effective use of ISS facilities, target scientific and technology questions and transfer scientific and technology results for Earth benefits. The Materials Science research will use a low gravity environment for flight and ground-based research in crystallization, fundamental processing, properties characterization, and biomaterials in order to obtain fundamental understanding of various phenomena effects and relationships to the structures, processing, and properties of materials. Completion of the International Space Station's (ISS) first major assembly, during the past year, provides new opportunities for on-orbit research and scientific utilization. Accommodations will support a variety of Materials Science payload hardware both in the US and international partner modules with emphasis on early use of Express Rack and Glovebox facilities. This paper addresses the current scope of the flight investigator program. These investigators will use the various capabilities of the ISS to achieve their research objectives. The type of research and classification of materials being studied will be addressed. This includes the recent emphasis being placed on nanomaterials and biomaterials type research. Materials Science Program will pursue a new, interdisciplinary approach, which contributes, to Human Space Flight Exploration research. The Materials Science Research Facility (MSRF) and other related American and International experiment modules will serve as the foundation for this research. Discussion will be included to explain the changing concept for materials science research processing capabilities aboard the ISS along with the various ground facilities necessary to support the program. Finally, the paper will address the initial utilization schedule and strategy for the various materials science payloads including their corresponding hardware.

Schlagheck, Ronald↗

NASA NTRS2001

Space Station Biological Research Project Habitat: Incubator

Developed as part of the suite of Space Station Biological Research Project (SSBRP) hardware to support research aboard the International Space Station (ISS), the Incubator is a temperature-controlled chamber, for conducting life science research with small animal, plant and microbial specimens. The Incubator is designed for use only on the ISS and is transported to/from the ISS, unpowered and without specimens, in the Multi-Purpose Logistics Module (MPLM) of the Shuttle. The Incubator interfaces with the three SSBRP Host Systems; the Habitat Holding Racks (HHR), the Life Sciences Glovebox (LSG) and the 2.5 m Centrifuge Rotor (CR), providing investigators with the ability to conduct research in microgravity and at variable gravity levels of up to 2-g. The temperature within the Specimen Chamber can be controlled between 4 and 45 C. Cabin air is recirculated within the Specimen Chamber and can be exchanged with the ISS cabin at a rate of approximately equal 50 cc/min. The humidity of the Specimen Chamber is monitored. The Specimen Chamber has a usable volume of approximately equal 19 liters and contains two (2) connectors at 28v dc, (60W) for science equipment; 5 dedicated thermometers for science; ports to support analog and digital signals from experiment unique sensors or other equipment; an Ethernet port; and a video port. It is currently manifested for UF-3 and will be launched integrated within the first SSBRP Habitat Holding Rack.

Nakamura, G. J.↗

NASA NTRS2000

G-LIMIT

Dynamic modeling and controller design efforts were conducted at the University of Alabama in Huntsville (UAH) on the Glovebox Integrated Microgravity Isolation Technology (g-LIMIT), under NAG8-1598; the funded period of performance was 8/26/98 through 12/31/00. The title of the grant was 'Support of g-LIMIT for Isolation of Space Science Experiments: Dynamic Modeling and Optimal Controller Synthesis.' Design codes were developed for implementation of a steady-state H infinity controller design method using the frequency weighted plant for the MDOF g-LIMIT design case.

Hampton, R. David↗

NASA NTRS2001

Numerical Simulation of an Enclosed Laminar Jet Diffusion Flame in Microgravity Environment: Comparison with ELF Data

Enclosed diffusion flames are commonly found in practical combustion systems, such as the power-plant combustor, gas turbine combustor, and jet engine after-burner. In these systems, fuel is injected into a duct with a co-flowing or cross-flowing air stream. The diffusion flame is found at the surface where the fuel jet and oxygen meet, react, and consume each other. In combustors, this flame is anchored at the burner (i.e., fuel jet inlet) unless adverse conditions cause the flame to lift off or blow out. Investigations of burner stability study the lift off, reattachment, and blow out of the flame. Flame stability is strongly dependent on the fuel jet velocity. When the fuel jet velocity is sufficiently low, the diffusion flame anchors at the burner rim. When the fuel jet velocity is increased, the flame base gradually moves downstream. However, when the fuel jet velocity increases beyond a critical value, the flame base abruptly jumps downstream. When this "jump" occurs, the flame is said to have reached its lift-off condition and the critical fuel jet velocity is called the lift-off velocity. While lifted, the flame is not attached to the burner and it appears to float in mid-air. Flow conditions are such that the flame cannot be maintained at the burner rim despite the presence of both fuel and oxygen. When the fuel jet velocity is further increased, the flame will eventually extinguish at its blowout condition. In contrast, if the fuel jet velocity of a lifted flame is reduced, the flame base moves upstream and abruptly returns to anchor at the burner rim. The fuel jet velocity at reattachment can be much lower than that at lift off, illustrating the hysteresis effect present in flame stability. Although there have been numerous studies of flame stability, the controlling mechanisms are not well understood. This uncertainty is described by Pitts in his review of various competing theories of lift off and blow out in turbulent jet diffusion flames. There has been some research on the stability of laminar flames, but most studies have focused on turbulent flames. It is also well known that the airflow around the fuel jet can significantly alter the lift off, reattachment and blow out of the jet diffusion flame. Buoyant convection is sufficiently strong in 1-g flames that it can dominate the flow-field, even at the burner rim. In normal-gravity testing, it is very difficult to delineate the effects of the forced airflow from those of the buoyancy-induced flow. Comparison of normal-gravity and microgravity flames provides clear indication of the influence of forced and buoyant flows on the flame stability. The overall goal of the Enclosed Laminar Flames (ELF) investigation (STS-87/USMP-4 Space Shuttle mission, November to December 1997) is to improve our understanding of the effects of buoyant convection on the structure and stability of co-flow diffusion flame, e.g., see http://zeta.lerc.nasa.gov/expr/elf.htm. The ELF hardware meets the experiment hardware limit of the 35-liter interior volume of the glovebox working area, and the 180x220-mm dimensions of the main door. The ELF experiment module is a miniature, fan-driven wind tunnel, equipped with a gas supply system. A 1.5-mm diameter nozzle is located on the duct's flow axis. The cross section of the duct is nominally a 76-mm square with rounded corners. The forced air velocity can be varied from about 0.2 to 0.9 m/s. The fuel flow can be set as high as 3 std. cubic centimeter (cc) per second, which corresponds to a nozzle exit velocity of up to 1.70 m/s. The ELF hardware and experimental procedure are discussed in detail in Brooker et al. The 1-g test results are repeated in several experiments following the STS-87 Mission. The ELF study is also relevant to practical systems because the momentum-dominated behavior of turbulent flames can be achieved in laminar flames in microgravity. The specific objectives of this paper are to evaluate the use reduced model for simulation of flame lift-off and blowout.

Jia, Kezhong↗