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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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Viewgraphs on the Permeable Membrane Experiment are presented. An experiment overview is given. The Membrane Phase Separation Experiment, Membrane Diffusion Interference Experiment, and Membrane Wetting Experiment are described. Finally, summary and conclusions are discussed.
Polymer dispersed liquid crystal thin films have been deposited on a glass substrate, utilizing the processes of polymerization and solvent evaporation induced phase separation. Liquid crystal microdroplets trapped on the upper surface of the thin film respond to the shear stress due to air or gas flow on the surface layer. Response to an applied step shear stress input on the surface layer has been measured by measuring the time response of the transmitted light intensity. Initial results on the measurements of the light transmission as a function of the air flow differential pressure indicate that these systems offer features suitable for boundary layer and gas flow sensors.
The Superfluid Helium On-Orbit Transfer (SHOOT) Flight Demonstration is a shuttle attached payload designed to demonstrate the technology necessary to resupply liquid helium dewars in space. Many SHOOT components will also have use in other aerospace cryogenic systems. The first of two SHOOT dewar systems has been fabricated. The ground performance testing of this dewar is described. The performance tests include measurements of heat leak, impedances of the two vent lines, heat pulse mass gauging accuracy, and superfluid transfer parameters such as flow rate and efficiency. A laboratory dewar was substituted for the second flight dewar for the transfer tests. These tests enable a precise analytical model of the transfer process to be verified. SHOOT performance is thus quantified, except for components such as the liquid acquisition devices and a phase separator which cannot be verified in one gravity.
Filter removes foam from soapy water stream discharged by primary phase separator of water-reclamation system. Uses no antifoam chemicals, contains no moving parts and requires no energy input other than small energy needed to pump water through filter.
We outline our plans for incorporating a Neural Network Prototyping Package into the IRAF environment. The package we are developing will allow the user to choose between different types of networks and to specify the details of the particular architecture chosen. Neural networks consist of a highly interconnected set of simple processing units. The strengths of the connections between units are determined by weights which are adaptively set as the network 'learns'. In some cases, learning can be a separate phase of the user cycle of the network while in other cases the network learns continuously. Neural networks have been found to be very useful in pattern recognition and image processing applications. They can form very general 'decision boundaries' to differentiate between objects in pattern space and they can be used for associative recall of patterns based on partial cures and for adaptive filtering. We discuss the different architectures we plan to use and give examples of what they can do.
The 1993 Advanced Design Project at the University of Alaska Fairbanks was to design a spacecraft as a technology demonstration of wireless power transmission (WPT). With cost effectiveness as a design constraint, a micro-satellite in low earth orbit (LEO) was chosen for the mission. Existing and near term technologies were analyzed and selected for the project. In addition to the conceptual design of the payload, support systems, and structure, the analysis included attention to safety, environmental impact, cost, and schedule for construction and operation. Wireless power beaming is not a new concept. Experimental demonstrations and study efforts have continued since the early 1960's. With the latest progress in transmitter and receiver technology, the next natural step is to beam power from earth to space. This proposed flight demonstration will advance the science of power beaming and prove the viability of various applications of WPT in space. Two methods of power beaming will be examined during the two separate phases of the spacecraft life. The first phase will demonstrate the technology and examine the theory of microwave power transmission at a high frequency. Special aspects of the first phase will include a highly accurate attitude control system and a 14 m inflatable parabolic antenna. The second phase will investigate the utilization of high intensity laser power using modified photovoltaic arrays. Special instrumentation on the spacecraft will measure the conversion efficiency from the received microwave or laser power to direct current power.
The objectives are to: (1) Understand the influence in low gravity of flow on interface shape. For example, document and control the influence of axial flow on the Plateau-Rayleigh instability of a liquid bridge; and (2) Extend the ground-based density-matching technique of low gravity simulation to situations with flow; that is, develop Plateau chamber experiments for which flow can be controlled. Containerless containment of liquid by surface tension has broad importance in low gravity. For space vehicles, the behavior of liquid/gas interfaces is crucial to successful liquid management systems. In microgravity science, free interfaces are exploited in various applications. Examples include float-zone crystal growth, phase separation near the critical point of liquid mixtures (spinoidal decomposition) and quenching of miscibility gap molten metal alloys. In some cases, it is desired to stabilize the capillary instability while in others it is desired to induce capillary breakup. In all cases, understanding the stability of interface shape in the presence of liquid motion is central.
Theoretical models of the cooling of flare plasma are reexamined. By assuming that the cooling occurs in two separate phase where conduction and radiation, respectively, dominate, a simple analytic formula for the cooling time of a flare plasma is derived. Unlike earlier order-of-magnitude scalings, this result accounts for the effect of the evolution of the loop plasma parameters on the cooling time. When the conductive cooling leads to an 'evaporation' of chromospheric material, the cooling time scales L(exp 5/6)/p(exp 1/6), where the coronal phase (defined as the time maximum temperature). When the conductive cooling is static, the cooling time scales as L(exp 3/4)n(exp 1/4). In deriving these results, use was made of an important scaling law (T proportional to n(exp 2)) during the radiative cooling phase that was forst noted in one-dimensional hydrodynamic numerical simulations (Serio et al. 1991; Jakimiec et al. 1992). Our own simulations show that this result is restricted to approximately the radiative loss function of Rosner, Tucker, & Vaiana (1978). for different radiative loss functions, other scaling result, with T and n scaling almost linearly when the radiative loss falls off as T(exp -2). It is shown that these scaling laws are part of a class of analytic solutions developed by Antiocos (1980).
The rapid changes in our world precipitated by technology have created new problems and new challenges for education and training. A knowledge 'explosion' is occurring as our society moves toward a service oriented economy that relies on information as the major resource. Complex computer systems are beginning to dominate the workplace, causing alarming growth and change in many fields. The rapidly changing nature of the workplace, especially in fields related to information technology, requires that our knowledge be updated constantly. This characteristic of modern society poses seemingly unsolvable instructional problems involving coverage and obsolescence. The sheer amount of information to be learned is rapidly increasing, while at the same time some information becomes obsolete in light of new information. Education, therefore, must become a lifelong process that features learning of new material and skills as needed in relation to the job to be done. Because of the problems cited above, the current model of learning in advance may no longer be feasible in our high-technology world. In many cases, learning in advance is impossible because there are simply too many things to learn. In addition, learning in advance can be time consuming, and often results in decontextualized knowledge that does not readily transfer to the work environment. The large and growing discrepancy between the amount of potentially relevant knowledge available and the amount a person can know and remember makes learning on demand an important alternative to current instructional practices. Learning on demand takes place whenever an individual must learn something new in order to perform a task or make a decision. Learning on demand is a promising approach for addressing the problems of coverage and obsolescence because learning is contextualized and integrated into the task environment rather than being relegated to a separate phase that precedes work. Learning on demand allows learners to see for themselves the usefulness of new knowledge for actual problem situations, thereby increasing the motivation for learning new information. Finally, learning on demand makes new information relevant to the task at hand, leading to more informed decision making, better quality products, and improved performance.
Boiling is an effective mode of heat transfer since high heat flux levels are possible driven by relatively small temperature differences. The high heat transfer coefficients associated with boiling have made the use of these processes increasingly attractive to aerospace engineering. Applications of this type include compact evaporators in the thermal control of aircraft avionics and spacecraft environments, heat pipes, and use of boiling to cool electronic equipment. In spite of its efficiency, cooling based on liquid-vapor phase change processes has not yet found wide application in aerospace engineering due to specific problems associated with the low gravity environment. After a heated surface has reached the superheat required for the initiation of nucleate boiling, bubbles will start forming at nucleation sites along the solid interface by evaporation of the liquid. Bubbles in contact with the wall will continue growing by this mechanism until they detach. In terrestrial conditions, bubble detachment is determined by the competition between body forces (e.g. buoyancy) and surface tension forces that act to anchor the bubble along the three phase contact line. For a given body force potential and a balance of tensions along the three phase contact line, bubbles must reach a critical size before the body force can cause them to detach from the wall. In a low gravity environment the critical bubble size for detachment is much larger than under terrestrial conditions, since buoyancy is a less effective means of bubble removal. Active techniques of heat transfer enhancement in single phase and phase change processes by utilizing electric fields have been the subject of intensive research during recent years. The field of electrohydrodynamics (EHD) deals with the interactions between electric fields, flow fields and temperature fields. Previous studies indicate that in terrestrial applications nucleate boiling heat transfer can be increased by a factor of 50 as compared to values obtained for the same system without electric fields. Imposing an external electric field holds the promise to improve pool boiling heat transfer in low gravity, since a phase separation force other than gravity is introduced. The goal of our research is to experimentally investigate the potential of EHD and the mechanisms responsible for EHD heat transfer enhancement in boiling in low gravity conditions.
Work during the second year under this grant (NAG8-1161) resulted in several major achievements. We have characterized protein impurities as well as microheterogeneities in the proteins hen egg white lysozyme and horse spleen apoferritin, and demonstrated the effects of these impurities on nucleation and crystallization. In particular, the purification of apoferritin resulted in crystals with an X-ray diffraction resolution of better than 1.8 A, i.e. a 1 A improvement over earlier work on the cubic form. Furthermore, we have shown, in association with studies of liquid-liquid phase separation, that depending on the growth conditions, lysozyme can produce all growth morphologies that have been observed with other proteins. Finally, in connection with our experimental and simulation work on growth step bunching, we have developed a system-dependent criterion for advantages and disadvantages of crystallization from solution under reduced gravity. In the following, these efforts are described in some detail.
A new mathematical ansatz is developed for solution of the time-dependent Ginzburg-Landau nonlinear partial differential equation describing metastable state relaxation in binary (solute+solvent) non-critical solutions with non-conserved scalar order parameter in presence of a gravitational field. It has been demonstrated analytically that in such systems metastability initiates heterogeneous solute redistribution which results in the formation of a non-equilibrium singly-periodic spatial solute structure in the new solute-rich phase. The critical radius of nucleation and the induction time in these systems are gravity-dependent. It has also been proved that metastable state relaxation in vertical columns of supersaturated non-critical binary solutions leads to formation of the solute concentration gradient. Analytical expression for this concentration gradient is found and analysed. It is concluded that gravity can initiate phase separation (nucleation or spinodal decomposition).
Experimental and simulation studies of the nucleation and growth kinetics of proteins have revealed phenomena that are specific for macromolecular crystallization, and others that provide a more detailed understanding of solution crystallization in general. The more specific phenomena, which include metastable liquid-liquid phase separations and gelation prior to solid nucleation, are due to the small ratio of the intermolecular interaction-range to the size of molecules involved. The apparently more generally applicable mechanisms include the cascade-like formation of macrosteps, as an intrinsic morphological instability that roots in the coupled bulk transport and nonlinear interface kinetics in systems with mixed growth rate control. Analyses of this nonlinear response provide (a) criteria for the choice of bulk transport conditions to minimize structural defect formation, and (b) indications that the "slow" protein crystallization kinetics stems from the mutual retardation of growth steps.
One of the goals of NASA''s HEDS enterprise is to establish a long-term human presence on Mars at a fraction of the cost of employing today''s technology. The most direct method of reducing mission cost is to reduce the launch mass of the spacecraft. If the propellants for the return phase of the mission are produced on Mars, the total spacecraft mass could be reduced significantly. An interim goal is a Mars Sample Return (MSR) mission, which is proposed to demonstrate the feasibility of in-situ propellant production (ISPP). Five candidate ISPP systems for producing two fuels and oxygen from the Martian atmosphere are considered in this design trade-off study:(1) Zirconia cell with methanol synthesis, (2) Reverse water gas shift (RWGS) with water electrolysis and methanol synthesis, (3) Sabatier process for methane production with water electrolysis, (4) Sabatier process with water electrolysis and partial methane pyrolysis, and (5) Sabatier/RWGS combination with water electrolysis. These systems have been the subject of numerous previous analytical studies and laboratory demonstrations. In this investigation, the systems are objectively compared on the basis of thermochemical performance models using a commonly used chemical plant analysis software package. The realistic effects of incomplete chemical conversion and gas phase separator performance are included in these models. This study focuses on the chemical processing and product separation subsystems. The CO2 compression upstream of the chemical plane and the liquefaction/storage components are not included here.
Pretreatment of urine using Oxone and sulfuric acid is baselined in the International Space Station (ISS) waste water reclamation system to control odors, fix urea and control microbial growth. In addition, pretreatment is recommended for long term flight use of urine collection and two phase separation to reduce or eliminate fouling of the associated hardware and plumbing with urine precipitates. This is important for ISS application because the amount of maintenance time for cleaning and repairing hardware must be minimized. This paper describes the development of a chemical pretreatment system based on solid tablet shapes which are positioned in the urine collection hose and are dissolved by the intrained urine at the proper ratio of pretreatment to urine. Building upon the prior success of the developed and tested solid Oxone tablet a trade study was completed to confirm if a similar approach, or alternative, would be appropriate for the sulfuric acid injection method. In addition, a recommended handling and packaging approach of the solid tablets for long term, safe and convenient use on ISS was addressed. Consequently, the solid tablet concept with suitable packaging was identified as the Urine Pretreat / Prefilter Assembly (UPPA). Testing of the UPPA configuration confirmed the disolution rates and ratios required by ISS were achieved. This testing included laboratory controlled methods as well as a 'real world' test evaluation that occurred during the 150 day Stage 10 Water Recovery Test (WRT) conducted at NASA Marshall Space Flight Center (MSFC).
The Performance Goal for NASA's Microgravity Materials Science Program reads "Use microgravity to establish and improve quantitative and predictive relationships between the structure, processing and properties of materials." The advent of the International Space Station will open up a new era in Materials Science Research including the ability to perform long term and frequent experiments in microgravity. As indicated the objective is to gain a greater understanding of issues of materials science in an environment in which the force of gravity can be effectively switched off. Thus gravity related issues of convection, buoyancy and hydrostatic forces can be reduced and the science behind the structure/processing/properties relationship can more easily be understood. The specific areas of research covered within the program are (1) the study of Nucleation and Metastable States, (2) Prediction and Control of Microstructure (including pattern formation and morphological stability), (3) Phase Separation and Interfacial Stability, (4) Transport Phenomena (including process modeling and thermophysical properties measurement), and (5) Crystal Growth, and Defect Generation and Control. All classes of materials, including metals and alloys, glasses and ceramics, polymers, electronic materials (including organic and inorganic single crystals), aerogels and nanostructures, are included in these areas. The principal experimental equipment available to the materials scientist on the International Space Station (ISS) will be the Materials Science Research Facility (MSRF). Each of these systems will be accommodated in a single ISS rack, which can operate autonomously, will accommodate telescience operations, and will provide real time data to the ground. Eventual plans call for three MSRF racks, the first of which will be shared with the European Space Agency (ESA). Under international agreements, ESA and other partners will provide some of the equipment, while NASA covers launch and integration costs. The MSRF facilities will include modular components, which can be exchanged to provide inserts specifically matched to the engineering requirements of the particular Principal Investigator. To defray costs and avoid duplication of engineering effort NASA is also pursuing the possibility of using facilities provided by international partners. By this means it is anticipated that all of the types of research outlined in the previous paragraph can be done on the ISS.
Container and containerless processing was employed to determine liquidus temperatures and to examine microstructural development in the Cu-Nb system. The Cu-Nb phase diagram of an S-shaped, near-horizontal liquidus, has been confirmed by both the temperature-time profiles and resultant microstructures with only Nb dendrites in a Cu matrix, which were obtained from crucible experiments under clean conditions. However, the microstructural pathways of Cu-Nb alloys are particularly sensitive to processing variables. By the addition of oxygen impurities or rapid solidification, droplet-shaped morphology was observed for some compositions, implying occurrence of a liquid-phase separation. The effects of impurities and cooling rates are analyzed in connection with a stable and metastable liquid miscibility gap, respectively.
Thermo-physical properties of two bulk metallic glass forming alloys, Ti34Zr11Cu47Ni8 (VIT 101) and Zr57Nb5Ni12.6Al10CU15.4 (VIT 106), were investigated in the stable and undercooled melt. Our investigation focused on measurements of the specific heat in the stable and undercooled liquid using the method of AC modulation calorimetry. The VIT 106 exhibited a maximum undercooling of 140 K in free radiative cooling. Specific heat measurements could be performed in stable melt down to an undercooling of 80 K. Analysis of the specific heat data indicate an anomaly near the equilibrium liquidus temperature. This anomaly is also observed in y the temperature dependencies of the external relaxation time, the specific volume, and the surface tension; it is tentatively attributed to a phase separation in the liquid state. The VIT 101 specimen exhibited a small undercooling of about 50 K. Specific heat measurements were performed in the stable and undercooled melt. These various results will be combined with ground based work such as the measurement of T-T-T curves in the electrostatic levitator and low temperature viscosity and specific heat measurements for modeling the nucleation kinetics of these alloys.