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At least 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Simulation-Aided Design and Interpretation of Results of Microgravity-Based Solidification Experiments

The preparation and interpretation of microgravity experiments conducted on the International Space Station (ISS) can be challenging because of the remote location of the equipment. Although a “ground unit” is typically available on Earth, it is not located in the laboratory of the principal investigator. Furthermore, test experiments in the ground unit cannot fully duplicate heat transfer conditions of the weightless environment, and thus be a reliable reference for experiment design. Under such conditions, numerical simulations are a valuable tool both for preparing the experiments and interpreting the results obtained under terrestrial and micro-gravity conditions. In this work, we developed a detailed 3D model of the “SUBSA” furnace located at the ISS, and demonstrate its use in our present investigation which includes melt growth and vapor growth of InI crystals on the ISS. In 2002, the SUBSA furnace was designed and built for the growth of InSb crystals in the Microgravity Science Glovebox (MSG) at the ISS. The SUBSA furnace features a transparent section without heating elements, where the axial temperature gradient is high. In our present investigation, we have used the same furnace to grow four InI crystals from the melt, and two InI crystals from the vapor phase (2018-2021). InI crystals have ~20 times lower thermal conductivity than InSb crystals. As a result, during melt growth, the InI crystals were exposed to extremely high temperature gradients. To reduce the axial temperature gradient, we added external jackets made from high thermal conductivity material to the growth ampoules. The SUBSA furnace could not be modeled as asymmetric because of its rectangular shape and right-angled transparent section, which contains a convoluted geometry. The rectangular shape of the transparent section further complicates modelling of radiative heat transfer, which dominates in the zone. At present, numerical simulations are being conducted to resolve an apparent discrepancy between the readings of the 5 thermocouples located in the SUBSA furnace, and the observed position of the solid and molten material. The 3D simulation will be presented, along with the calibration and growth experiment results conducted in microgravity and in the SUBSA ground unit. The developed model should be useful for upcoming microgravity investigations planned to be conducted in the SUBSA facility.

V Riabov↗
NASA NTRS2005

Multicompartment Liquid-Cooling/Warming Protective Garments

Shortened, multicompartment liquid-cooling / warming garments (LCWGs) for protecting astronauts, firefighters, and others at risk of exposure to extremes of temperature are undergoing development. Unlike prior liquid-circulation thermal-protection suits that provide either cooling or warming but not both, an LCWG as envisioned would provide cooling at some body locations and/or heating at other locations, as needed: For example, sometimes there is a need to cool the body core and to heat the extremities simultaneously. An LCWG garment of the type to be developed is said to be shortened because the liquid-cooling and - heating zones would not cover the whole body and, instead, would cover reduced areas selected for maximum heating and cooling effectiveness. Physiological research is under way to provide a rational basis for selection of the liquid-cooling and -heating areas. In addition to enabling better (relative to prior liquid-circulation garments) balancing of heat among different body regions, the use of selective heating and cooling in zones would contribute to a reduction in the amount of energy needed to operate a thermal-protection suit.

Koscheyev, Victor S.↗
NASA NTRS2017

Increasing Resiliency to Extreme Weather

We work at NASA's Goddard Institute for Space Studies, integrating the agency's satellite imagery and projections of extreme weather events into urban planning. In recent weeks, we have watched as Christian's hometown, Houston, has been ransacked by historic rainfall and flooding and Hurricane Irma has battered the U.S. Virgin Islands, Puerto Rico and Florida. Then, Hurricane Maria devastated Puerto Rico leaving millions of people without power. Sea-level rise, storm surge, warm ocean temperatures, and extreme rainfall interacted to exacerbate the damages incurred by Hurricanes Harvey, Irma, and Maria. Coastal flooding combined with inland flooding to wreak extraordinary havoc.

Rosenzweig, Cynthia↗
NASA NTRS1972

The Nimbus 4 infrared spectroscopy experiment. I - Calibrated thermal emission spectra.

Measurement of the infrared spectrum of the earth and atmosphere between 400 and 1600/cm. In an effort to obtain spectra with high absolute accuracy, it was necessary to incorporate many factors into the calibration, including small departures from unity in the emissivity of the on-board calibration source, imbalance between cold and warm calibration ports, and effects due to orbital variations in instrument temperature. The inclusion of such higher order corrections, along with careful data screening processes, has ensured a high quality data set that can be used in a variety of geophysical and meteorological investigations. Representative samples of data are presented that illustrate the behavior of the thermal emission spectra under a variety of conditions encountered in a typical orbit, including extremes in temperature, surface reststrahlung (or residual ray) effects, and various types of cloud conditions.

Hanel, R. A.↗
NASA NTRS1993

Turntable mechanism

In vacuum plasma spraying a turntable must be provided which not only makes it possible to rotate and tilt a heavy workpiece, but to operate at vacuum plasma temperatures to do so. In the vacuum plasma coating of large parts such as combustion chambers of rocket engines, the workpiece must not only be rotated, but it must be tilted. Hence, the turntable must be capable not only of supporting heavy parts, but of angulating such heavy workpieces. And this must be done without drive means failure due to extremely high temperatures under which the turntable mechanism is operated. A turntable mechanism is provided which is capable of operating under such conditions. For cooling the turntable drive mechanism, internal cooling means are included.

Myers, William Neill↗
NASA NTRS2004

Overview of NASA Glenn Seal Developments

Turbine engine studies have shown that reducing high pressure turbine (HPT) blade tip clearances will reduce fuel burn, lower emissions, retain exhaust gas temperature margin and increase range. Dr. Lattime presented the design and development status of a new Active Clearance Control Test rig aimed at demonstrating advanced ACC approaches and sensors. Mr. Melcher presented controls considerations for turbine active clearance control. Mr. Geisheimer of Radatech presented an overview of their microwave blade tip sensor technology. Microwave tip sensors show promise of operation in the extreme gas temperatures present in the HPT location. Mr. Justak presented an overview of non-contacting seal developments at Advanced Technologies Group. Dr. Braun presented investigations into a non-contacting finger seal under development by NASA GRC and University of Akron. Dr. Stango presented analytical assessments of the effects of flow-induced radial loads on brush seal behavior. Mr. Flaherty presented innovative seal and seal fabrication developments at FlowServ. Mr. Chappel presented abradable seal developments at Technetics. Dr. Daniels presented an overview of NASA GRC s acoustic seal developments. NASA is investigating the ability to harness high amplitude acoustic waves, possible through a new field of acoustics called Resonant Macrosonic Synthesis, to effect a non-contacting, low leakage seal. Dr. Daniels presented early results showing the ability to restrict flow via acoustic pressures. Dr. Athavale presented numerical results simulating the flow blocking capability of a pre-prototype acoustic seal.

Steinetz, Bruce M.↗
NASA NTRS1989

Life without water

Anhydrobiosis, or life without water is commonly demonstrated by a number of plants and animals. These organisms have the capacity to loose all body water, remain dry for various periods, and then be revived by rehydration. While in the anhydrobiotic state, these organisms become highly resistant to several environmental stresses such as extremely low temperatures, elevated temperatures, ionizing radiation, and high vacuum. Since water is commonly thought to be essential for life, survival of anhydrobiotic organisms with an almost total loss of water is examined. A search of literature reveal that many anhydrobiotic organisms make large quantities of trehalose or other carbohydrates. Laboratory experiments have shown that trehalose is able to stabilize and preserve microsomes of sarcoplasmic reticulum and artificial liposomes. It was demonstrated that trehalose and other disaccharides can interact directly with phosopipid headgroups and maintain membranes in their native configuration by replacing water in the headgroup region. Recent studies show that trehalose is an effective stabilizer of proteins during drying and that it does so by direct interaction with groups on the protein. If life that is able to withstand environmental extremes has ever developed on Mars, it is expected that such life would have developed some protective compounds which can stabilize macromolecular structure in the absence of water and at cold temperatures. On Earth, that role appears to be filled by carbohydrates that can stabilize both membrane and protein stuctures during freezing and drying. By analog with terrestrial systems, such life forms might develop resistance either during some reproductive stage or at any time during adult existence. If the resistant form is a developmental stage, the life cycle of the organism must be completed with a reasonable time period relative to time when environmental conditions are favorable. This would suggest that simple organisms with a short life cycle might be most sucessful.

Crowe, Lois M.↗
NASA NTRS1999

Miniature Heat Transport System for Nanosatellite Technology

The scientific understanding of key physical processes between the Sun and the Earth require simultaneous measurements from many vantage points in space. Nano-satellite technologies will enable a class of constellation missions for the NASA Space Science Sun-Earth Connections. This recent emphasis on the implementation of smaller satellites leads to a requirement for development of smaller subsystems in several areas. Key technologies under development include: advanced miniaturized chemical propulsion; miniaturized sensors; highly integrated, compact electronics; autonomous onboard and ground operations; miniatures low power tracking techniques for orbit determination; onboard RF communications capable of transmitting data to the ground from far distances; lightweight efficient solar array panels; lightweight, high output battery cells; lightweight yet strong composite materials for the nano-spacecraft and deployer-ship structures. These newer smaller systems may have higher power densities and higher thermal transport requirements than seen on previous small satellites. Furthermore, the small satellites may also have a requirement to maintain thermal control through extended earth shadows, possibly up to 8 hours long. Older thermal control technology, such as heaters, thermostats, and heat pipes, may not be sufficient to meet the requirements of these new systems. Conversely, a miniature two-phase heat transport system (Mini-HTS) such as a Capillary Pumped Loop (CPL) or Loop Heat Pipe (LBP) is a viable alternative. A Mini-HTS can provide fine temperature control, thermal diode action, and a highly efficient means of heat transfer. The Mini-HTS would have power capabilities in the range of tens of watts or less and provide thermal control over typical spacecraft ranges. The Mini-HTS would allow the internal portion of the spacecraft to be thermally isolated from the external radiator, thus protecting the internal components from extreme cold temperatures during an eclipse. The Mini-HTS would transport the beat from these components to a radiator during their operational modes, and it would be shutdown during non-operational or eclipse modes. Shutdown of the Mini-HTS would be accomplished with small heaters and has been successfully demonstrated on numerous occasions, both in the lab and on flight experiments. Efforts are now underway to miniaturize two-phase heat transport systems for the Nanosatellite project, with potential application to other small satellite programs. 'ne goal of this project is to design, build, and test miniature heat transport systems (MHTS) that would demonstrate the feasibility of a small Capillary Pumped Loop (CPL) or Loop Heat Pipe (LBP).

Douglas, Donya M,↗
NASA NTRS2003

Facesheet Delamination of Composite Sandwich Materials at Cryogenic Temperatures

The next generation of space transportation vehicles will require advances in lightweight structural materials and related design concepts to meet the increased demands on performance. One potential source for significant structural weight reduction is the replacement of traditional metallic cryogenic fuel tanks with new designs for polymeric matrix composite tanks. These new tank designs may take the form of thin-walled sandwich constructed with lightweight core and composite facesheets. Life-time durability requirements imply the materials must safely carry pressure loads, external structural loads, resist leakage and operate over an extremely wide temperature range. Aside from catastrophic events like tank wall penetration, one of the most likely scenarios for failure of a tank wall of sandwich construction is the permeation of cryogenic fluid into the sandwich core and the subsequent delamination of the sandwich facesheet due to the build-up of excessive internal pressure. The research presented in this paper was undertaken to help understand this specific problem of core to facesheet delamination in cryogenic environments and relate this data to basic mechanical properties. The experimental results presented herein provide data on the strain energy release rate (toughness) of the interface between the facesheet and the core of a composite sandwich subjected to simulated internal pressure. A unique test apparatus and associated test methods are described and the results are presented to highlight the effects of cryogenic temperature on the measured material properties.

Gates, Thomas S.↗
NASA NTRS1990

Investigations of a turbulence-driven solar wind model

This work presents an investigation of the properties of the one-dimensional, two-fluid turbulence-driven solar wind model introduced by Hollweg and Johnson (1988). It is found that the model has serious difficulties in reproducing the observed high-speed wind at 1 AU. In particular, the model proton temperatures are lower than those observed by a factor of 2 or more, and the highest temperature models yield excessive wave intensities at 1 AU. It appears that the problem stems from the specific spatial distribution of heat deposition in the model. Thus this study does not rule out a turbulence-driven fast solar wind, since other forms of the turbulent evolution could probably achieve better results. A three-fluid version of the model is also presented to show that the addition of alpha particles does not significantly reduce the extreme proton temperatures displayed near the sun by the Hollweg and Johnson work. Finally, it is suggested that the additional heating needs to be located well beyond the critical point, implying that the heating mechanism for the fast solar wind is likely not the same as that heating the solar corona.

Isenberg, Philip A.↗
NASA NTRS2006

Cryogenic Durability of a Carbon Fiber Reinforced Cyanate Ester Composite: Degree-of-Cure Effect

The James Webb Space Telescope (JWST) will be located approximately 1.5 million kilometers from Earth, producing extremely cold temperatures on the optical portion of the observatory. Specifically, the Optical Telescope Element (OTE) and Integrated Science Instrument Module (ISIM) will operate at approximately -240 C. Construction of the structural components of the OTE and ISIM require bonding dissimilar materials together, e.g. Invar-36 (an iron-nickel alloy) to a carbon fiber reinforced cyanate ester composite (CFRCE) with an epoxy adhesive. While these materials enable the cryogenic stability required for optical performance, their joint strength at these extreme conditions presents a unique design challenge. Therefore, the current study presents a detailed investigation into the optimization of cryogenic composite durability. It is demonstrated that by controlling the degree-of-cure of a laminate, one can achieve an enhanced resistance to microcracking and an improved residual strength following cryogenic cycling to -253 C.

Polis, Daniel L.↗
NASA NTRS1991

Refractory materials from lunar resources

Refractories - materials which are able to withstand extremely high temperatures - are sure to be an important part of any processing facility or human outpost which is built on Mars. Containers for processing lunar oxygen will need high temperature components. Fabrication of structural material from lunar resources need both containment vessels to hold high temperature melts and molds in which to form the final shapes. Certainly, it would be desirable to fabricate such vessels and molds on the Moon, rather than carrying them up from the Earth. At first glance, this might appear to be a trivial task, since the Moon's surface consists of a variety of refractory compositions. To turn the regolith into a useful fire brick or mold, however, will require water or other binders and additives which are likely to be in extremely short supply on the Moon. The steps needed to make fire bricks and molds for lunar-derived structural materials are examined, pointing out the critical steps and resources which will be needed. While these processes and applications may seem somewhat mundane, it is emphasized that it is precisely these rudimentary processes which must be mastered before discussing making aerobrakes, and other fancier refractories from lunar resources.

Fabes, B. D.↗
NASA NTRS2012

Drilling, Coring and Sampling Using Piezoelectric Actuated Mechanisms: From the USDC to a Piezo-Rotary-Hammer Drill

NASA exploration missions are increasingly including sampling tasks but with the growth in engineering experience (particularly, Phoenix Scout and MSL) it is now very much recognized that planetary drilling poses many challenges. The difficulties grow significantly with the hardness of sampled material, the depth of drilling and the harshness of the environmental conditions. To address the requirements for samplers that could be operated at the conditions of the various bodies in the solar system, a number of piezoelectric actuated drills and corers were developed by the Advanced Technologies Group of JPL. The basic configuration that was conceived in 1998 is known as the Ultrasonic/Sonic Driller/Corer (USDC), and it operates as a percussive mechanism. This drill requires as low preload as 10N (important for operation at low gravity) allowing to operate with as low-mass device as 400g, use an average power as low as 2- 3W and drill rocks as hard as basalt. A key feature of this drilling mechanism is the use of a free-mass to convert the ultrasonic vibrations generated by piezoelectric stack to sonic impacts on the bit. Using the versatile capabilities f the USDC led to the development of many configurations and device sizes. Significant improvement of the penetration rate was achieved by augmenting the hammering action by rotation and use of a fluted bit to remove cuttings. To reach meters deep in ice a wireline drill was developed called the Ultrasonic/Sonic Gopher and it was demonstrated in 2005 to penetrate about 2-m deep at Antarctica. Jointly with Honeybee Robotics, this mechanism is currently being modified to incorporate rotation and inchworm operation forming Auto-Gopher to reach meters deep in rocks. To take advantage of the ability of piezoelectric actuators to operate over a wide temperatures range, piezoelectric actuated drills were developed and demonstrated to operate at as cold as -200oC and as hot as 500oC. In this paper, the developed mechanisms will be reviewed and discussed including the configurations, capabilities, and challenges.

ultrasonic/Sonic Driller/ Corer (USDC)↗
NASA NTRS2009

Testing of a Microwave Blade Tip Clearance Sensor at the NASA Glenn Research Center

The development of new active tip clearance control and structural health monitoring schemes in turbine engines and other types of rotating machinery requires sensors that are highly accurate and can operate in a high temperature environment. The use of a microwave sensor to acquire blade tip clearance and tip timing measurements is being explored at the NASA Glenn Research Center. The microwave blade tip clearance sensor works on principles that are very similar to a short range radar system. The sensor sends a continuous microwave signal towards a target and measures the reflected signal. The phase difference of the reflected signal is directly proportional to the distance between the sensor and the target being measured. This type of sensor is beneficial in that it has the ability to operate at extremely high temperatures and is unaffected by contaminants that may be present in turbine engines. The use of microwave sensors for this application is a new concept. Techniques on calibrating the sensors along with installation effects are not well quantified as they are for other sensor technologies. Developing calibration techniques and evaluating installation effects are essential in using these sensors to make tip clearance and tip timing measurements. As a means of better understanding these issues, the microwave sensors were used on a bench top calibration rig, a large axial vane fan, and a turbofan. Background on the microwave tip clearance sensor, an overview of their calibration, and the results from their use on the axial vane fan and the turbofan will be presented in this paper.

Woike, Mark R.↗
NASA NTRS2009

Testing of a Microwave Blade Tip Clearance Sensor at the NASA Glenn Research Center

The development of new active tip clearance control and structural health monitoring schemes in turbine engines and other types of rotating machinery requires sensors that are highly accurate and can operate in a high-temperature environment. The use of a microwave sensor to acquire blade tip clearance and tip timing measurements is being explored at the NASA Glenn Research Center. The microwave blade tip clearance sensor works on principles that are very similar to a short-range radar system. The sensor sends a continuous microwave signal towards a target and measures the reflected signal. The phase difference of the reflected signal is directly proportional to the distance between the sensor and the target being measured. This type of sensor is beneficial in that it has the ability to operate at extremely high temperatures and is unaffected by contaminants that may be present in turbine engines. The use of microwave sensors for this application is a new concept. Techniques on calibrating the sensors along with installation effects are not well quantified as they are for other sensor technologies. Developing calibration techniques and evaluating installation effects are essential in using these sensors to make tip clearance and tip timing measurements. As a means of better understanding these issues, the microwave sensors were used on a benchtop calibration rig, a large axial vane fan, and a turbofan. Background on the microwave tip clearance sensor, an overview of their calibration, and the results from their use on the axial vane fan and the turbofan will be presented in this paper.

Woike, Mark R.↗
NASA NTRS1989

Low temperature storage container for transporting perishables to space station

Two storage containers are disclosed within which food or biological samples may be stored for transfer in a module by the space shuttle to a space station while maintaining the food or samples at very low temperatures. The container is formed in two parts, each part having an inner shell and an outer shell disposed about the inner shell. The space between the shells is filled with a continuous wrap multi-layer insulation and a getter material. The two parts of the container have interlocking members and when connected together are sealed for preventing leakage from the space between the shells. After the two parts are filled with frozen food or samples they are connected together and a vacuum is drawn in the space between the shells and the container is stored in the module. For the extremely low temperature requirements of biological samples, an internal liner having a phase change material charged by a refrigerant coil is disposed in the space between the shells, and the container is formed from glass fiber material including honeycomb structural elements. All surfaces of the glass fiber which face the vacuum space are lined with a metal foil.

Owen, James W.↗
NASA NTRSDate not supplied

Measurements of Temperature and Enthalpy in NASA Ames 60-MW Arcjet using Atomic Oxygen and Atomic Nitrogen Absorption

We report on measurements of temperature and enthalpy in the 60-MW Interaction Heating Facility (IHF) Arcjet at the NASA Ames Research Center. These quantities were measured at sub-second temporal resolution using tunable diode laser absorption spectroscopy, employing four Distributed Feedback (DFB) lasers to simultaneously probe the arcjet flow. Optical access was achieved through a specially-designed optical disk mounted in series with the modules of the arc heater in the add-air plenum of the column, which is positioned between the downstream electrodes and the nozzle. Gas at this measurement location serves as the reservoir condition for the ensuing supersonic expansion. Conditions in the reservoir are extreme, with temperatures between 5000-8000 K and pressures between 1-9 atm. Absorption from the 5S state of atomic oxygen at 777.2 nm and the 4P state of atomic nitrogen at 868.0 nm, two electronically-excited quantum states, formed the basis of the flow characterization measurements. Fiber-coupled laser light was pitched through the IHF via 1/8" ports in the optical disks, permitting optical access with minimal intrusion to the flow. Data was collected at 3 nominal conditions, a Low condition (1600 A, 2000 V, 0.13 kg/s), a Medium condition (3500 A, 5700 V, 0.61 kg/s), and a High condition (5900 A, 6800 V, 0.84 kg/s). Measurements suggest agreement within 1-2% between excited oxygen and excited nitrogen thermometry, indicating approximate thermal and chemical equilibration of the arcjet reservoir state, a result in keeping with long-standing assumptions of CFD modelling. Spatial gradients are found in the flow due to enthalpy loss to the facility walls, but the measured spatial non-uniformities are consistent with axi-symmetry. Measurements of specific enthalpy in the reservoir are also made utilizing excited oxygen and excited nitrogen absorption under the assumption of chemical equilibration.

Peter M. Finch↗
NASA NTRS1998

Impact of the 1997-1998 El-Nino of Regional Hydrology

The 1997-1998 El-Nino brought with it a range of severe local-regional hydrological phenomena. Record high temperatures and extremely dry soil conditions in Texas is an example of this regional effect. The El-Nino and La-Nina change the continental weather patterns considerably. However, connections between continental weather anomalies and regional or local anomalies have not been established to a high degree of confidence. There are several unique features of the recent El-Nino and La-Nina. Due to the recognition of the present El-Nino well in advance, there have been several coupled model studies on global and regional scales. Secondly, there is a near real-time monitoring of the situation using data from satellite sensors, namely, SeaWIFS, TOVS, AVHRR and GOES. Both observations and modeling characterize the large scale features of this El-Nino fairly well. However the connection to the local and regional hydrological phenomenon still needs to be made. This paper will use satellite observations and analysis data to establish a relation between local hydrology and large scale weather patterns. This will be the first step in using satellite data to perform regional hydrological simulations of surface temperature and soil moisture.

Lakshmi, Venkataraman↗