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At least 235 records · Page 13

Adiabatic demagnetization refrigerator for use in zero gravity

In this effort, a new design concept for an adiabatic demagnetization refrigerator (ADR) that is capable of operation in zero gravity has been developed. The design uses a vortex precooler to lower the initial temperature of magnetic salt from the initial space superfluid helium dewar of 1.8 K to 1.1 K. This reduces the required maximum magnetic field from 4 Tesla to 2 Tesla. The laboratory prototype vortex precooler reached a minimum temperature of 0.78 K, and had a cooling power of 1 mW at 1.1 K. A study was conducted to determine the dependence of vortex cooler performance on system element configuration. A superfluid filled capillary heat switch was used in the design. The laboratory prototype ADR reached a minimum temperature of 0.107 K, and maintained temperatures below 0.125 K for 90 minutes. Demagnetization was carried out from a maximum field of 2 T. A soft iron shield was developed that reduced the radial central field to 1 gauss at 0.25 meters.

Dingus, Michael L.↗

Breaking Kelvin-Helmholtz waves and cloud-top entrainment as revealed by K-band Doppler radar

Radars have occasionally detected breaking Kelvin-Helmholtz (KH) waves under clear-air conditions in the atmospheric boundary layer and in the free troposphere. However, very few direct measurements of such waves within clouds have previously been reported and those have not clearly documented wave breaking. In this article, we present some of the most detailed and striking radar observations to date of breaking KH waves within clouds and at cloud top and discuss their relevance to the issue of cloud-top entrainment, which is believed to be important in convective and stratiform clouds. Aircraft observations reported by Stith suggest that vortex-like circulations near cloud top are an entrainment mechanism in cumuliform clouds. Laboratory and modeling studies have examined possibility that KH instability may be responsible for mixing at cloud top, but direct observations have not yet been presented. Preliminary analyses shown here may help fill this gap. The data presented in this paper were obtained during two field projects in 1991 that included observations from the NOAA Wave Propagation Laboratory's K-band Doppler radar (wavelength = 8.7 mm) and special rawinsonde ascents. The sensitivity (-30 dBZ at 10 km range), fine spatial resolution (375-m pulse length and 0.5 degrees beamwidth), velocity measurement precision (5-10 cm s-1), scanning capability, and relative immunity to ground clutter make it sensitive to non-precipitating and weakly precipitating clouds, and make it an excellent instrument to study gravity waves in clouds. In particular, the narrow beam width and short pulse length create scattering volumes that are cylinders 37.5 m long and 45 m (90 m) in diameter at 5 km (10 km) range. These characteristics allow the radar to resolve the detailed structure in breaking KH waves such as have been seen in photographic cloud images.

Martner, Brooks E.↗

Laboratory on the Moon: Equipping and Testing of a Habitat Laboratory for the Scientific Exploration of the Moon by Humans

A human habitat on the Moon is predestined to house a laboratory, especially if it is built for scientific missions on the Moon. This laboratory could be used for (1) conducting experiments utilizing the lunar gravity and prepare experiments to be placed outside the laboratory in the lunar environment, (2) conducting analyses of lunar rock and regolith in high volume, and (3) performing preliminary analyses and screening of samples to be sent to Earth for more detailed, specialized analysis. In the past, spaceflight missions have often been implemented by adding scientific instruments after most of the engineering work is already finished, limiting scientific studies to relatively scattered, insular topics. However, if prepared appropriately, a research laboratory on the Moon can help address scientific questions thoroughly and at a fundamental level. Moreover, the challenge of creating a viable habitat is not only an engineering one, but one that requires input from architects, designers, and psychologists. After all, the crew not only works inside the habitat laboratory, but they spend (close to) their entire time on the Moon inside the habitat and under the isolation and confinement that comes with it. We combine science, engineering, and architecture to create a habitat laboratory that meets their conflicting requirements: The laboratory of the Moon and Mars Base Analog (MaMBA) has been designed with inputs from (1) scientists of selected disciplines, particularly geology, materials science, chemistry, biology, and medicine, (2) space architects specializing on extraterrestrial bases, and (3) engineers for the constraints imposed by the lunar environment. The MaMBA laboratory was built in 2019 into the mock-up of the first MaMBA module (out of six). Subsequently, the laboratory was tested by volunteer scientists for its usability. The scientists used the laboratory for work deemed representative of lunar scientific analyses; the complete test runs lasted one week each, with one test run in June 2019 and the second test run in late September 2019 following some modifications suggested by the scientists. Here, we will present an overview of the scientific topics that we think should be addressed on the Moon, together with a suggestion of scientific instrumentation that would be helpful for such investigations. Moreover, we present the MaMBA laboratory, equipped with the proposed instrumentation, and the outcomes of the test runs with a particular focus on the lessons learned regarding the equipping of the laboratory.

Christiane Heinicke↗

Developing Tests of Visual Dependency

Astronauts develop neural adaptive responses to microgravity during space flight. Consequently these adaptive responses cause maladaptive disturbances in balance and gait function when astronauts return to Earth and are re-exposed to gravity. Current research in the Neuroscience Laboratories at NASA-JSC is focused on understanding how exposure to space flight produces post-flight disturbances in balance and gait control and developing training programs designed to facilitate the rapid recovery of functional mobility after space flight. In concert with these disturbances, astronauts also often report an increase in their visual dependency during space flight. To better understand this phenomenon, studies were conducted with specially designed training programs focusing on visual dependency with the aim to understand and enhance subjects ability to rapidly adapt to novel sensory situations. The Rod and Frame test (RFT) was used first to assess an individual s visual dependency, using a variety of testing techniques. Once assessed, subjects were asked to perform two novel tasks under transformation (both the Pegboard and Cube Construction tasks). Results indicate that head position cues and initial visual test conditions had no effect on an individual s visual dependency scores. Subjects were also able to adapt to the manual tasks after several trials. Individual visual dependency correlated with ability to adapt manual to a novel visual distortion only for the cube task. Subjects with higher visual dependency showed decreased ability to adapt to this task. Ultimately, it was revealed that the RFT may serve as an effective prediction tool to produce individualized adaptability training prescriptions that target the specific sensory profile of each crewmember.

Kindrat, Alexandra N.↗

Plans and Recent Developments for Fluid Physics Experiments Aboard the ISS

From the very first days of human spaceflight, NASA has been conducting experiments in space to understand the effect of weightlessness on physical and chemically reacting systems. NASA Glenn Research Center (GRC) in Cleveland, Ohio has been at the forefront of this research looking at both fundamental studies in microgravity as well as experiments targeted at reducing the risks to long duration human missions to the moon, Mars, and beyond. In the current International Space Station (ISS) era, we now have an orbiting laboratory that provides the highly desired condition of long-duration microgravity. This allows continuous and interactive research similar to Earth-based laboratories. Because of these capabilities, the ISS is an indispensable laboratory for low gravity research. NASA GRC has been actively involved in developing and operating facilities and experiments on the ISS since the beginning of a permanent human presence on November 2, 2000. As the lead Center for Fluid Physics, NASA GRC is developing and testing the Pack Bed Reactor Experiment (PBRE), Zero Boil Off (ZBOT) Two Phase Flow Separator Experiment (TPFSE), Multiphase Flow Heat Transfer (MFHT) Experiment and the Electro-HydroDynamic (EHD) experiment. An overview each experiment, including its objectives, concept and status will be presented. In addition, data will be made available after a nominal period to NASAs Physical Science Informatics PSI database to the scientific community to enable additional analyses of results.

Two phase flow↗

Life sciences biomedical research planning for Space Station

The Biomedical Research Project (BmRP), a major component of the NASA Life Sciences Space Station Program, incorporates a laboratory for the study of the effects of microgravity on the human body, and the development of techniques capable of modifying or counteracting these effects. Attention is presently given to a representative scenario of BmRP investigations and associated engineering analyses, together with an account of the evolutionary process by which the scenarios and the Space Station design requirements they entail are identified. Attention is given to a tether-implemented 'variable gravity centrifuge'.

Primeaux, Gary R.↗

Microgravity combustion science: A program overview

The promise of microgravity combustion research is introduced by way of a brief survey of results, the available set of reduced gravity facilities, and plans for experimental capabilities in the Space Station era. The study of fundamental combustion processes in a microgravity environment is a relatively new scientific endeavor. A few simple, precursor experiments were conducted in the early 1970's. Today the advent of the U.S. space shuttle and the anticipation of the Space Station Freedom provide for scientists and engineers a special opportunity, in the form of long duration microgravity laboratories, and need, in the form of spacecraft fire safety and a variety of terrestrial applications, to pursue fresh insight into the basic physics of combustion. 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 become permissible. The range of experiments completed to date was not broad, but is growing. Unexpected phenomena have been observed often in microgravity combustion experiments, raising questions about the degree of accuracy and completion of our classical understanding and our ability to estimate spacecraft fire hazards. Because of the field's relative immaturity, instrumentation has been restricted primarily to high-speed photography. To better explain these findings, more sophisticated diagnostic instrumentation, similar to that evolving in terrestrial laboratories, is being developed for use on Space Station Freedom and, along the way, in existing microgravity facilities.

Source record↗

An imaging spectrometer for microgravity application

Flame structure is the result of complex interaction of mechanisms operating in both unwanted fires and controlled combustion systems. The scientific study of gas-jet diffusion flames in reduced-gravity environment is of interest because the effects of buoyancy on flow entrainment and acceleration are lessened. Measurements of flames have been restricted to cinematography, thermocouples, and radiometers. SSG, Inc. is developing an MWIR imaging spectrometer (MIS) for microgravity flame measurements. The device will be delivered to NASA Lewis at the end of this project to demonstrate flame measurements in the laboratory. With proper modifications, the MIS can be used to monitor a gas-jet flame under microgravity on a NASA Learjet or DC-9.

Wong, Wallace K.↗

Experiment 6: Surface Tension Driven Convection Experiment-2 (STDCE-2)

Results are reported from the Second Surface Tension Driven Convection Experiment (STDCE-2) performed aboard the Second United States Microgravity Laboratory (USML-2), which flew as Space Shuttle mission STS-73 and launched on October 20, 1995. Oscillatory thermocapillary flows were investigated in open cylindrical containers filled with 2 centistokes kinematic viscosity (Pr=27 at 25 C) silicone oil. Two different heating modes were investigated in detail. The main objectives of the experiments were to determine the onset of oscillatory thermocapillary flow under highly reduced buoyancy and gravity conditions and to study the important features of the oscillatory flow. The onset conditions were determined in three different size containers (1.2-, 2-, and 3-cm diameter) and for various free surface shapes (flat and curved). Numerical and scaling analyses were also performed to understand the basic steady flows. The analysis shows that the main flow is viscous-dominated near the onset of oscillations. The onset conditions determined in the present experiments together with our earlier ground-based data show that one could not describe the oscillation phenomenon if the fluid free surface is assumed to be rigid. Therefore, a parameter representing free surface deformation was derived, and the data are shown to be correlated well by that parameter. The oscillation patterns and frequencies are also presented.

Ostrach, Simon↗

Zero-G experiments in two-phase fluids flow regimes

The two-phase flows studied were liquid and gas mixtures in a straight flow channel of circular cross-section. Boundaries between flow regimes have been defined for normogravity on coordinates of gas quality and total mass velocity; and, when combined with boundary expressions having a Froude number term, an analytical model was derived predicting boundary shifts with changes in gravity level. Experiments with air and water were performed, first in the normogravity environment of a ground laboratory and then in 'zero gravity' aboard a KC-135 aircraft flying parabolic trajectories. Data reduction confirmed regime boundary shifts in the direction predicted, although the magnitude was a little less than predicted. Pressure drop measurements showed significant increases for the low gravity condition.

Heppner, D. B.↗

Microgravity particle research on the Space Station - The gas-grain simulation facility

In the gravitational field on earth, the large settling rate of micron-sized particles and the effects of gravity-induced convection prohibit many interesting studies of phenomena such as coagulation, collisions, and mutual interactions of droplets, dust grains and other particles. Examples of exobiology experiments involving these phenomena are the simulation of organic aerosol formation in Titan's atmosphere, studies of the role of comets in prebiotic chemical evolution, and simulations of carbon grain interactions in various astrophysical environments. The Gas-Grain Simulation Facility (GGSF) is a proposed earth-orbital laboratory that will allow present ground-based experimental programs which study processes involving small particles and weak interactions to be extended to a new domain. Physics issues that scientists wishing to propose GGSF experiments must consider are reviewed in this paper. Specifically, coagulation, motion in gases and vacua, and wall deposition of particles in a microgravity environment are discussed.

Fogleman, G.↗

Studies of Radiation-Driven and Buoyancy-Driven Fluid Flows and Transport

It is well known that radiative heat transport influences many types of buoyant flows due to its effect on the temperature and thus density field in the fluid medium. It is of interest to study gaseous flows driven solely by radiation in the absence of buoyancy, particularly because of its application to astrophysical flows that are well known from astronomical observations and numerical simulation. However, no laboratory-scale experiments of this phenomenon have ever been conducted. To study the possibility of obtaining such flows in the laboratory, an apparatus was built to produce large temperature differences (Delta (T)) up to 300 K in a gas confined between flat parallel plates. SF6 was used as the radiatively-active gas because its Planck absorption length is much shorter than that of any other common non-reactive gas. The NASA-Lewis 2.2 second drop tower was used to obtain reduced gravity in order to suppress buoyancy effects. To image the resulting flows, a laser shearing interferometer was employed. Initial results indicate the presence of flow that does not appear to be attributable to the residual flow resulting from buoyancy influences before the drop. For Delta(T) greater than 70 K, slight deformations in the interferometer fringes seen at lower Delta(T) became large unsteady swirls. Such behavior did not occur for radiatively-inactive gases, suggesting that a flow driven solely by radiation was obtained in SF6 and to a lesser extent in CO2. This was more pronounced at higher pressures and plate spacings, consistent with our scaling predictions.

Ronney, Paul D.↗

Studies of Radiation-Driven and Buoyancy-Driven Fluid Flows and Transport

It is well known that radiative heat transport influences many types of buoyant flows due to its effect on the temperature and thus density field in the fluid medium. It is of interest to study gaseous flows driven solely by radiation in the absence of buoyancy, particularly because of its application to astrophysical flows that are well known from astronomical observations and numerical simulation. However, no laboratory-scale experiments of this phenomenon have ever been conducted. To study the possibility of obtaining such flows in the laboratory, an apparatus was built to produce large temperature differences (Delta T) up to 300 K in a gas confined between flat parallel plates. SF6 was used as the radiatively-active gas because its Planck absorption length is much shorter than that of any other common non-reactive gas. The NASA-Lewis 2.2 second drop tower was used to obtain reduced gravity in order to suppress buoyancy effects. To image the resulting flows, a laser shearing interferometer was employed. Initial results indicate the presence of flow that does not appear to be attributable to the residual flow resulting from buoyancy influences before the drop. For Delta T greater than 70 K, slight deformations in the interferometer fringes seen at lower Delta T became large unsteady swirls. Such behavior did not occur for radiatively-inactive gases, suggesting that a flow driven solely by radiation was obtained in SF6 and to a lesser extent in CO2 This was more pronounced at higher pressures and plate spacings, consistent with our scaling predictions.

Ronney, Paul D.↗

Studies of Islands on Freely Suspended Bubbles of Smectic Liquid Crystal

We have constructed an optical system for observing the internal structure of freely suspended smectic liquid crystal bubbles using a reflected light microscope. Liquid crystal bubbles can have thicker circular regions (islands) which can easily be generated by shrinking the bubble diameter. The diameter of these islands is approximately 10 microns and they are typically up to five times thicker than the surrounding liquid crystal film (500 angstroms). In the Laboratory, the location of the islands is strongly influenced by gravity, which causes the majority of islands to migrate to the bottom half of the bubble. We will describe the size and thickness distributions of islands and their time evolution, and also discuss two-dimensional hydrodynamics and turbulence of smectic bubbles, the shapes of islands and holes affected by bubble vibrations, and the interactions between islands, which we have probed using optical tweezers.

Pattanaporkratana, A.↗

TPSAS-NF1676L-11435-DND

Acoustical studies of atmospheric events like convective storms, shear-induced turbulence, acoustic gravity waves, microbursts, hurricanes, and clear air turbulence (CAT) over the past thirty years have established that these events are strong emitters of infrasound. Several mechanisms for the production of infrasound have been proposed, for example by the acceleration of vorticity or by space-time correlations of the turbulent Reynolds stresses (Lighthill theory). Electromagnetic (EM) sensors suffer two severe disadvantages in the detection of clear air turbulence and severe storms. The first is the inability to receive returns in clear air, where reflective targets (precipitation, particulate matter) are absent. The second disadvantage is that EM systems, being active, require scanning to locate an event, as opposed to a passive infrasonic array, which receives infrasonic radiation independently of event location. Further, EM systems, even weather radar ("NEXRAD"), do not have the extensive range (hundreds of miles) characteristic of infrasound. The leading laboratory for studies on atmospheric infrasound over the past thirty years has been the Environmental Technology Laboratory of the National Oceanic and Atmospheric Administration. This laboratory conducted measurements of infrasound from many sources, among which clear air turbulence was but a small part of the overall program. The summary of the results of this program suggests for development of a practical detection system. In other words, despite the progress made in this area, there does not exist today a National network of stations to monitor infrasound from turbulence. Under Innovative Partnership Program, Researchers at NASA Langley Research Center have been working to achieve that goal. As a first step, NASA Langley has designed and developed a portable infrasonic detection system which can be used to make useful infrasound measurements at a location where it was not possible previously. The design and results of the compact system, based upon laboratory and field experiments, will be presented.

Qamar Shams↗

Developmental Gene Regulation and Mechanisms of Evolution

The Marine Biological Laboratory and the National Aeronautics and Space Administration have established a cooperative agreement with the formation of a Center for Advanced Studies 'in the Space Life Sciences (CASSLS) at the MBL. This Center serves as an interface between NASA and the basic science community, addressing issues of mutual interest. The Center for Advanced Studies 'in the Space Life Sciences provides a forum for scientists to think and discuss, often for the first time, the role that gravity and aspects of spaceflight may play 'in fundamental cellular and physiologic processes. In addition the Center will sponsor discussions on evolutionary biology. These interactions will inform the community of research opportunities that are of interest to NASA. This workshop is one of a series of symposia, workshops and seminars that will be held at the MBL to advise NASA on a wide variety of topics in the life sciences, including cell biology, developmental biology, mg evolutionary biology, molecular biology, neurobiology, plant biology and systems biology.

Source record↗

An Overview of the Materials Science Research at the Marshall Space Flight Center Electrostatic Levitator Facility and Recent CDDF Efforts

Containerless processing is an important tool for materials research. The freedom from a crucible allows processing of liquid materials in a metastable undercooled state, as well as allowing processing of high temperature and highly reactive melts. Electrostatic levitation (ESL) is a containerless method which provides a number of unique advantages, including the ability to process non-conducting materials, the ability to operate in ultra-high vacuum or at moderate gas pressure (approx. = 5 atm), and the decoupling of positioning force from sample heating. ESL also has the potential to reduce internal flow velocities below those possible with electromagnetic, acoustic, or aero-acoustic techniques. In electrostatic levitation, the acceleration of gravity (or residual acceleration in reduced gravity) is opposed by the action of an applied electric field on a charged sample. Microgravity allows electrostatic levitation to work even more effectively. The ESL facility at NASA s Marshall Space Flight Center is in use for materials research and thermophysical property measurement by a number of different internal and external investigators. Results from the recent CDDF studies on the high energy X-ray beamline at the Advanced Photon Source of Argonne National Laboratory will be presented. The Microgravity Research Program supports the facility.

Source record↗

Transport processes research

Fundamental research in reduced gravity on transport processes occurring during crystallization and/or during solidification processes was studied. The details of the transport processes in various materials processing modes will be systematically studied. A Shuttle experiment will be planned to provide a better understanding of the role of fluid motion on the formation of morphological patterns and roles of these patterns in solid composition. The approach to the research will involve theoretical modeling of transport processes, non-incursive ground-based laboratory measurements of model systems, and the definition of requirements for space experimentation.

Saville, D. A.↗