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Prospects and Challenges for Magnetic Propellant Positioning in Low-Gravity
Abstract
[The final version of this paper can be found in https://doi.org/10.1016/j.actaastro.2021.06.045]
The sloshing of liquids in low-gravity entails several technical challenges for spacecraft designers and operators. Those include the generation of significant attitude disturbances, the uncontrolled displacement of the center of mass of the vehicle or the production of gas bubbles, among others. Magnetic fields can be used to control the position of a magnetically susceptible propellant and transform a highly stochastic fluid system (non-linear sloshing) into a deterministic problem (linear sloshing). The employment of magnetic settling forces also produces an increase of the natural sloshing frequencies and damping ratios of the liquid. Despite being proposed in the early 1960s, this approach remains largely unexplored. A recently developed magnetic sloshing control model is here presented and extended, and potential space applications are explored. Technical challenges associated with the reachability, scaling and stability of paramagnetic and ferromagnetic systems are discussed, unveiling a roadmap for the implementation of this technology.
... The understanding of this phenomenon is of major importance for the study and characterization of the dynamics of space vehicles [2,3]. As a way to control the position of liquids in low-gravity environments, the application of electric [4] and magnetic [5][6][7][8][9][10] fields has been proposed to generate a gravity-equivalent restoring force. The magnetic approach receives the name of Magnetic Positive Positioning (MP 2 ). ...
... The characterization of the natural oscillation frequencies of magnetic liquids is a first and fundamental step towards the development of MP 2 technologies, such as Tuned Magnetic Liquid Dampers [11,12] or passive and active positioning devices [10]. The need for accurate simulation frameworks has motivated the development of coupled quasi-analytic [13] and numerical models [14], as well as the execution of microgravity experiments [15,16]. ...
This paper addresses the operation in microgravity of the surface reconstruction device whose design is detailed in the first part of the manuscript. The system, employed during the drop tower campaign of the UNOOSA DropTES 2019 StELIUM experiment, studies the axisymmetric and lateral oscillations of a ferrofluid solution in microgravity. The free liquid surface is reconstructed in a cylindrical tank and relevant metrics of the magnetic sloshing problem, such as contact angles, hysteresis parameters, natural oscillation frequencies, or damping ratios, are derived. The result is a rich and unique database where several phenomena of scientific and technological interest are reported for the first time. The dependence of the fundamental axisymmetric and lateral modal frequencies with the applied magnetic field is consistent with the literature and past experiments. Although the detection system was designed and built using low-cost hardware, high-quality results are obtained.
... The study unveils a high risk of arcing inside the tanks and highlights the need for large, heavy and noisy power sources [5]. The magnetic equivalent, named Magnetic Positive Positioning (MP 2 ), has also been suggested to exploit the inherent properties of paramagnetic, diamagnetic, and ferromagnetic liquids [6][7][8]. ...
... This is appropriate for lowsusceptibility fluids, such as liquid oxygen or liquid hydrogen. The development of coupled magnetohydrodynamic simulation frameworks has however been identified as a key step towards the design of novel magnetic liquid sloshing devices [8]. Since the position of a highly-susceptible fluid modifies the magnetic field distribution, such numerical models should simultaneously solve the Navier-Stokes (fluid-dynamic) and Maxwell (magnetic) equations. ...
The term sloshing refers to the movement of liquids in partially filled containers. Low-gravity sloshing plays an important role in the configuration of space vehicles, as it affects their dynamics and complicates the propellant management system design. Magnetic forces can be used to position a susceptible fluid, tune its natural frequencies, and increase its damping ratios in low-gravity. However, prior work shows that the analysis of this phenomenon, named magnetic liquid sloshing, requires advanced modeling capabilities. This paper introduces a coupled magnetohydrodynamic (MHD) model for the study of low-gravity axisymmetric magnetic liquid oscillations. The incompressible, viscous mass and momentum balances are solved together with the steady-state Maxwell equations by following a monolithic solution scheme. The method is fully implicit, allowing to reach a steady-state solution in a single time step. Five regions are used to discretize the simulation domain, that combines non-singular mappings and a meshfree approach. The steady-state solution (basic flow) is verified with equivalent computations from Comsol Multiphysics assuming the geometry and physical properties of the ESA Drop Your Thesis! 2017 drop tower experiment. Future steps include the study of linear oscillations, free surface stability properties, and lateral oscillations, among others.
... More recently, the ESA Drop Your Thesis! 2017 experimental campaign measured the axisymmetric sloshing of ferrofluids when subjected to an inhomogeneous magnetic field in microgravity (32; 33; 34). Quasi-analytical magnetic sloshing models (35) and feasibility analyses (36) have also been presented. ...
... Based on the existing bibliography on the topic, the lateral sloshing of magnetic liquids in microgravity can be regarded as an almost unexplored phenomenon with potential applications in space. Those include passive MP 2 , active MP 2 for center of mass positioning, and propellant sloshing damping, among others (36). Defining characteristics, such as the magnetic deformation of the meniscus or the shift of natural sloshing frequencies and damping ratios, have to be explored in relevant environments in order to improve our physics understanding and modeling capabilities. ...
Liquid sloshing represents a major challenge for the design and operation of space vehicles. In low-gravity environments, a highly non-linear movement can be produced due to the lack of stabilizing forces. This gives rise to significant disturbances that impact on the propulsion and attitude control systems of the spacecraft. The employment of magnetically susceptible fluids may open an interesting avenue to address this problem, but their dynamics in low gravity remain practically unexplored. The UNOOSA DropTES StELIUM project aims at filling this gap by studying the lateral sloshing of a ferrofluid solution subjected to an inhomogeneous magnetic field in microgravity. This paper describes the design process, challenges and preliminary results of the experiment, which was successfully launched at ZARM's drop tower in November 2019. The outcomes will be employed to validate the quasi-analytical models developed by the authors and set the path for the design of magnetic propellant positioning devices in space.
... Magnetic fields can be used to control liquid sloshing if the fluid responds to such stimulus [30]. This approach, known as Magnetic Positive Positioning, has been explored in the past for cryogenic propellants [12,31,32] and can be also employed to adjust the frequencies and damping ratios of a fluid system [33]. ...
This paper describes an inexpensive, non-invasive, and highly adaptable surface reconstruction device for opaque liquids. The instrument was developed to study the lateral sloshing of ferrofluids in microgravity as part of the UNOOSA DropTES 2019 StELIUM project. Its design is driven by the geometrical and mechanical constraints imposed by ZARM’s drop tower, where the experiment was launched in November 2019. The launch catapult and deceleration systems impose strong axial g-loads to a system that is confined in the reduced capsule environment. Redundant procedures are implemented to measure the first two lateral sloshing frequencies and damping ratios of the magnetic liquid, as well as its equilibrium surface in microgravity. Ideal vertical resolutions between 0.25 and 0.4 mm/px can be achieved with the configuration here proposed. The final performance depends, among other factors, on the correct application of the robust calibration procedure that is documented in this work.
... The study unveiled a high risk of arcing inside the tanks and highlighted the need of large, heavy and noisy power sources. Instead, it has been suggested to make use of the inherent magnetic properties of paramagnetic and diamagnetic liquids, a strategy known as Magnetic Positive Positioning (Papell 1963;Martin and Holt 2000;Romero-Calvo et al. 2020d). A relevant work in this field is the NASA Magnetically Actuated Propellant Orientation (MAPO) experiment, that studied the magnetic positioning of liquid oxygen through a series of parabolic flight experiments with ferrofluids (Martin and Holt 2000). ...
The sloshing of liquids in low-gravity entails several technical challenges for spacecraft designers due to its effects on the dynamics and operation of space vehicles. Magnetic settling forces may be employed to position a susceptible liquid and address these issues. Although proposed in the early 1960s, this approach remains largely unexplored. In this paper, the equilibrium meniscus and axisymmetric oscillations of a ferrofluid solution in a cylindrical tank are studied for the first time while subject to a static inhomogeneous magnetic field in microgravity. Coupled fluid-magnetic simulations from a recently developed inviscid magnetic sloshing model are compared with measurements collected at ZARM's drop tower during the ESA Drop Your Thesis! 2017 campaign. The importance of the fluid-magnetic interaction is explored by means of an alternative uncoupled framework for diluted magnetic solutions. The coupled model shows a better agreement with experimental results in the determination of the magnetic deformation trend of the meniscus, but the uncoupled framework gives a better prediction of the magnetic frequency response which finds no theoretical justification. Although larger datasets are required to perform a robust point-by-point validation, these results hint at the existence of unmodeled physical effects in the system.
... This phenomenon is known as magnetic buoyancy and has been applied to terrestrial boiling experiments with ferrofluids [31,32]. Previous works on low-gravity magnetohydrodynamics have explored the diamagnetic manipulation of air bubbles in water [33,34], the positioning of diamagnetic materials [35], air-water separation [36], protein crystal growth [37], magnetic positive positioning [38][39][40][41][42], magnetic liquid sloshing [43,44], or combustion enhancement [34], among others. The application of Lorentz's force on liquid electrolytes has also been studied as a way to enhance hydrogen production [45][46][47][48][49][50][51][52][53][54][55]. ...
[The final version of this paper can be found in http://arc.aiaa.org/doi/abs/10.2514/1.A35021]
The management of fluids in space is complicated by the absence of strong buoyancy forces. This raises significant technical issues for two-phase flows applications, such as water electrolysis or boiling. Different approaches have been proposed and tested to induce phase separation in low-gravity; however, further efforts are still required to develop efficient, reliable, and safe devices. The employment of magnetic buoyancy is proposed as a complement or substitution of current methods, and as a way to induce the early detachment of gas bubbles from their nucleation surfaces. The governing magnetohydrodynamic equations describing incompressible two-phase flows subjected to static magnetic fields in low-gravity are presented, and numerical simulations are employed to demonstrate the reachability of current magnets under different configurations. The results support the employment of new-generation neodymium magnets for centimeter-scale electrolysis and phase separation technologies in space, that would benefit from reduced complexity, mass, and power requirements.
The formulation of the total force exerted by magnetic fields on ferrofluids has historically been a subject of intense debate and controversy. Although the theoretical foundations of this problem can now be considered to be well established, significant confusion still remains regarding the implementation of the associated expressions. However, the development of future applications in low-gravity environments is highly dependent on the correct modeling of this force. This paper presents a contextualized analysis of different proposed calculation procedures and validation in a space-like environment. Kinematic measurements of the movement of a ferrofluid droplet subjected to an inhomogeneous magnetic field in microgravity are compared with numerical predictions from a simplified physical model. Theoretical results are consistent with the assumptions of the model and show an excellent agreement with the experiment. The Kelvin force predictions are included in the discussion to exemplify how an incomplete modeling of the magnetic force leads to significant errors in the absence of gravity.
The sloshing of liquids in microgravity is a relevant problem of applied mechanics with important implications for spacecraft design. A magnetic settling force may be used to avoid the highly non-linear dynamics that characterize these systems. However, this approach is still largely unexplored. This paper presents a quasi-analytical low-gravity sloshing model for magnetic liquids under the action of external inhomogeneous magnetic fields. The problems of free and forced oscillations are solved for axisymmetric geometries and loads by employing a linearized formulation. The model may be of particular interest for the development of magnetic sloshing damping devices in space, whose behavior can be easily predicted and quantified with standard mechanical analogies.
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Abstract presented to the 26th European Low Gravity Research Association Biennial Symposium and General Assembly.
On June 29 th 2018 the student experiment PAPELL (Pump Application using Pulsed Electromagnets for Liquid reLocation) was launched as part of the commercial resupply mission CRS-15 on a Dragon vehicle to the International Space Station. During the "Uberflieger" competition, organized by the German Aerospace Center (DLR), three proposed student experiments were selected to be conducted on the International Space Station (ISS). The experiment was designed and built by members of the Small Satellite Student Society University of Stuttgart (KSat e.V). and is going to utilize electromagnets to manipulate ferrofluid, a liquid with suspended iron oxide nanoparticles. This gives the liquid paramagnetic properties, and allows to realise a pumping mechanism without mechanical components inside a container of 10 x 10 x 15 cm. As a result of surface tension and magnetic forces the ferrofluid forms droplets, which can be moved along by utilising the magnetic fields of phased activated electromagnets. The space in between individual droplets will be used to transport small solids through a pipe system. This paper analyses and describes the interaction between the electromagnetic fields of electromagnets and ferrofluid. The ferrofluid is nominally non-magnetic, but when introduced to a sufficiently strong magnetic field the ferrofluid is magnetized and is attracted to the magnetic field source. This is due to the fact that suspended iron oxide nanoparticles will align with the magnetic field. Results from experiments on Earth will be used to improve the analysis of the in-orbit behaviour.
This article deals with magnetic nano-fluids, which are the part of transformer oil ITO 100 and their behavior is influenced by a permanent magnetic field. We performed an IRC analysis in the time domain on the three different samples. Measurements were made before and after radiation of an electromagnetic field. The main objective was to examine changes in the properties of the samples due to the influence of the electromagnetic field. The measurements depend on the orientation of the external magnetic field. This behavior occurs especially during the structuring of the nanoparticles in the sample exposed to the magnetic field. These processes change the polarization of the liquid because the nanoparticles concentration is contained in the fluid.
The aim of the presented work was to investigate the stability of biocompatible magnetic fluid, i.e. water-based magnetic fluid containing magnetite nanoparticles stabilized by surfactant sodium oleate and modified by bovine serum albumin (BSA) after electron irradiation. Samples with the same concentration of Fe3O4 but different mass ratio BSA/Fe3O4 (w/w= 0:25, 1.0 and 2.5) were studied. The electron irradiation caused about 10% reduction of the saturation magnetization in the samples with w/w BSA/Fe3O4 ratio of 0.25 and less than 5% in the samples with w/w BSA/Fe3O4 ratio of 1 and 2.5.
The magnetic particles in the water-based magnetic fiuids were sterically stabilized by natrium oleate to prevent their agglomeration and consequently the adsorption of poly-ethylene-glycol (PEG) was carried out to improve the biocompatibility of the magnetic particles. Two sets of samples were prepared. The first set of the samples was with different molar weight of PEG (Mw = 400, 1000, 10 000 and 20 000) at the constant weight ratio of PEG/Fe 3O 4 = 0.25 and the second one was with different weight ratio of PEG/Fe 3O 4 and constant molar weight of PEG (Mw = 1000). The samples were irradiated with 20 Gy. The same reduction of saturated magnetization (about 10%) after electron irradiation with 20 Gy was observed for all prepared samples.
This paper is concerned with the interaction between the applied magnetic field and the magnetic fluid surface. Liquid responses of magnetic fluids under the magnetic and vibrating fields were investigated. Experiments were performed on a vibration-testing system which provided lateral and longitudinal excitation. The effect of the magnetic field gradient on liquid surface motion in an open circular cylindrical tank was noted. Details of surface responses of a magnetic fluid in the cylindrical container excited longitudinally under an applied magnetic field were revealed. Some similarities and differences between single magnetic spike oscillation and the symmetric free surface mode (0, 1) of magnetic liquid sloshing in the presence of a magnetic field were investigated. It was found that the elongation of the symmetric free surface mode (0, 1) and single magnetic spike were based on the same mechanism. The formation and the disappearance of magnetic drops formed by surface disintegration in the cylindrical container subject to horizontal vibration were also investigated. It was observed that the number of floating drops induced by vibrating the cylindrical container laterally with the natural frequency of the fluid-container system, decreased greatly with the magnetic field intensity.
The variation of the magnetic susceptibility of condensed oxygen with temperature and hydrostatic pressure up to 0.6 GPa has been investigated. The results yield an empirical relation between the exchange parameter and the intermolecular distance. High-field magnetisation data on alpha -oxygen indicate a spin-flop; the corresponding anisotropy agrees fairly well with results of magnetic dipole calculations which also include a prediction for the direction of the magnetisation axis. Evidence is presented for magnetic long-range order in beta -oxygen.
Magnetic colloids are relatively new man-made nanomaterials whose magnetic susceptibility is several orders of magnitude larger
than that of natural substances. Experiments conducted in magnetic fluids show that strengthening or weakening of thermal
convection in colloids is dictated by a competition between the gravitational and magnetic mechanisms as well as by the effect
of the fluid density stratification due to gravitational sedimentation of magnetic particles and their aggregates. Therefore
experiments in microgravity conditions are required to eliminate gravitational sedimentation. This will enable an accurate
investigation of convection in magnetic fluids and unambiguous study of the interaction of a magnetic field with a magnetopolarized
medium. Such experiments are also needed to perform an accurate measurement of fluid’s transport coefficients.
Analytical centrifugation is used for the first time to measure sedimentation equilibrium concentration profiles of a ferrofluid, a concentrated colloidal dispersion of strongly absorbing magnetic nanoparticles. To keep the optical absorbance from becoming too strong, the optical path length is restricted to 50 μm by placing the dispersion in a flat glass capillary. The concentration profile is kept from becoming too steep, despite the relatively high buoyant mass of the nanoparticles, by making novel use of a low-velocity analytical centrifuge that was not designed to measure equilibrium profiles. The experimental approach is validated by comparison with profiles obtained using an analytical ultracentrifuge. At concentrations of a few hundred grams per liter, the osmotic pressures calculated from the equilibrium profiles are lower than expected for hard spheres or non-interacting particles, due to magnetic dipolar interactions. By following the presented experimental approach, it will now also be possible to characterize the interparticle interactions of other strongly absorbing colloidal particles not studied before by analytical centrifugation.
[The final version of this work can be found at https://doi.org/10.1016/j.actaastro.2021.08.029 and https://doi.org/10.1016/j.actaastro.2021.07.020] Liquid level measurement devices are required in experimental sloshing research. Several techniques with different capabilities and degrees of complexity have been historically proposed to cover this need. This paper describes an inexpensive, non-invasive and highly adaptable surface reconstruction device for opaque liquids. The instrument was developed to study the lateral sloshing of ferrofluids in microgravity as part of the UNOOSA DropTES StELIUM project. Its design is driven by the highly demanding geometrical and mechanical constraints imposed by ZARM’s drop tower, where the experiment will be launched in November 2019. The device implements redundant procedures to measure the first three lateral sloshing frequencies and damping ratios of the liquid, as well as its equilibrium surface in microgravity. Ideal vertical resolutions of 0.4 mm/px can be achieved with the configuration here implemented. The actual performance depends, among other factors, on the application of a robust calibration procedure.
In situ resource utilization (ISRU), the use of materials available on-site to replenish supplies or manufacture components during a mission, is vital to sustaining human presence in space. ISRU has been identified by NASA as one of the key technologies in the Human Exploration Destination Systems Technology Area. In recent years, the abundance of water in the solar system has been made increasingly clear. Extraterrestrial water, liquid water especially, is of great scientific interest, as targets where water is available are often desirable for future exploration. ISRU with water is therefore a particularly high priority. This paper considers the implications of in situ water on the design of space systems, with the use of water for multiple purposes on the CisLunar Explorers EM-1 secondary payload as a case study. Water onboard the CisLunar Explorers is used in every subsystem: as propellant, for slosh-damping, as a heat sink, and as a radiation shield. The CisLunar Explorers spacecraft do not collect water in situ but, instead, serve as a pathfinder for demonstrating the utility and versatility of water for future ISRU.
Ferrofluids are colloidal suspensions of magnetic nanoparticles in a carrier liquid. It is beneficial, for both fundamental research and future applications of ferrofluids in space, to obtain reliable measurements of the dynamics of ferrofluids in microgravity. This field remains unexplored since experiments in microgravity are expensive and the access to associated facilities is limited. In this ongoing project, the free surface displacement of a ferrofluid solution was measured in microgravity conditions in the ZARM Drop Tower in Bremen as part of the Drop Your Thesis! 2017 programme run by the ESA Education Office. The ferromagnetic solution is subjected to a controlled magnetic field while an initial percussion is imposed. Preliminary results point to significant contributions to the analysis of ferrofluid dynamics and sloshing dynamics in microgravity.
Hematite represents the most common burning rate modifier used in propellant production. The tuning of burning rate is obtained even for amounts ranging below 1 wt% of the total composition. Different studies have evidenced a role in ammonium perchlorate dissociation while there are not enough literature documents to clearly support or oppose its capability to enhance binder decomposition. The acceptance of such ingredient in an industrial environment is based mostly on the verification of few parameters, relevant to catalytic action (namely, particle size, specific surface area). The complexity of the iron oxide family shows a wide set of features, neglected in standard quality check but important for a detailed characterization. Such properties assist in defining a unique fingerprint of the material and can be used for detailed identification of batch-to-batch reproducibility, for new supplier qualification, or for improvement of basic knowledge. The present paper is an extract of a detailed characterization activity performed on different batches of nominally identical propellant-grade hematite. Reported results show peculiar properties of the ingredients and characterization methodologies specifically employed for the scope, proposing an end-to-end batch analysis for full ingredient back-trace capability in the supply chain.
A colloidal ferrofluid (FF) with superparamagnetic iron oxide nanoparticles (SPION) has been investigated for the AC breakdown strength during the accelerated thermal aging test. Three volume concentrations of a transformer oil based FF were subjected to the accelerated thermal tests at the temperature 90 °C. AC breakdown strength (BDS) tests were carried out every 200 h period for up to 600 h. The breakdown probabilities were calculated according Weibull distribution function. Measured BDS populations were compared with a base carrier oil. The BDS median of the clear carrier oil has been observed to fall down 1.54 times, however for particular FF samples it dropped 2.31, 2.90 and 3.63 times, respectively, when comparing properties of the samples before testing with the samples after aging. Final BDS probability distributions show that the dielectrics withstand voltage of FF became lower than that of the carrier oil. The long-term thermal load of the particular FF is critical for its colloidal stability, which is deduced to be the main reason of such a significant BDS reduction. The impact of the thermal aging on the AC magnetic susceptibility is briefly documented, too.
An experimental and computational study is presented on the interfacial dynamics of a colloidal fluid having both high electric conductivity and high magnetic permeability in the presence of simultaneous electric and magnetic stresses on the fluid/air interface. A transient computational model is developed that simultaneously solves the Navier-Stokes equation and Maxwells’ static equations to predict the transient geometry of the fluid subject to electric and magnetic stresses. This model is first applied to predict the onset of spray emission from a capillary needle electrospray source subjected to a magnetic field. The experimentally determined onset of emissions at each magnetic field agreed well with those predicted by the simulation tool. The predictive modeling tool was then applied to analyze the interfacial profile of a sessile droplet subjected to both electric and magnetic fields. The model captured the geometric evolution of the droplet for voltages up to approximately 85% of the critical onset voltage; near the onset, the model slightly overpredicted the droplet deformation. Using the interfacial stress obtained from the modeling tool, a quantitative discussion is made regarding the roles and magnitudes of the electric and magnetic stress components on the lead-up to the emission instability.
At present, very few CubeSats have flown in space featuring propulsion systems. Of those that have, the literature is scattered, published in a variety of formats (conference proceedings, contractor websites, technical notes, and journal articles), and often not available for public release. This paper seeks to collect the relevant publically releasable information in one location. To date, only two missions have featured propulsion systems as part of the technology demonstration. The IMPACT mission from the Aerospace Corporation launched several electrospray thrusters from Massachusetts Institute of Technology, and BricSAT-P from the United States Naval Academy had four micro-Cathode Arc Thrusters from George Washington University. Other than these two missions, propulsion on CubeSats has been used only for attitude control and reaction wheel desaturation via cold gas propulsion systems. As the desired capability of CubeSats increases, and more complex missions are planned, propulsion is required to accomplish the science and engineering objectives. This survey includes propulsion systems that have been designed specifically for the CubeSat platform and systems that fit within CubeSat constraints but were developed for other platforms. Throughout the survey, discussion of flight heritage and results of the mission are included where publicly released information and data have been made available. Major categories of propulsion systems that are in this survey are solar sails, cold gas propulsion, electric propulsion, and chemical propulsion systems. Only systems that have been tested in a laboratory or with some flight history are included.
Telemetry data from three 445 N engine burns of the Cassini spacecraft are used to characterize the high-g slosh characteristics of bipropellants in cylindrical tanks with spherical end domes. Comparisons between flight data and theoretical results indicate that high-g clean tank slosh frequency and high-g sector mode frequency could be predicted with errors of 3–5%. However, at lower tanks’ fill fractions of 5%. Also, high-g full-tank slosh mode in a tank with an eight-panel propellant management device could be modeled using an annular cylindrical tank. Again, prediction error of full-tank slosh frequency degraded with decreasing fill fractions. Based on these results, the high-g sector and full-tank propellant slosh frequencies could be well predicted using simple analytical techniques before these predictions are refined by liquid slosh computer modeling tools. A set of small-ampli...
Ferrofluidic feedthrough (FF) rotary seals containing either NdFeB or SmCo-type permanent magnets have been considered for use in the target and beam dump systems of the Facility for Rare Isotope Beams (FRIB). To evaluate their performance under irradiation three FF seals were irradiated in a mixed field consisting of fast neutrons, protons and γ-rays to an average absorbed dose of 0.2, 2.0, and 20.0 MGy at the Brookhaven Linac Isotope Producer facility (BLIP). The radiation types and energy profiles mimic those expected at the FRIB facility. Degradation of the operational performance of these devices due to irradiation is expected to be the result of the de-magnetization of the permanent magnets contained within the seal and the changes in the ferrofluid properties. Post-irradiation performance was evaluated by determining the ferrofluidic seal vacuum tightness and torque under static and dynamic conditions. The study revealed that the ferrofluidic feedthrough seal irradiated to a dose of 0.2 MGy maintained its vacuum tightness under both static and rotational condition while the one irradiated to a dose of 2.0 MGy exhibited signs of ferrofluid damage but no overall performance loss. At 20 MGy dose the effects of irradiation on the ferrofluid properties (viscosity and particle agglomeration) were shown to be severe. Furthermore, limited de-magnetization of the annular shaped Nd2Fe14B and Sm2Co27 magnets located within the irradiated FFs was observed for doses of 0.2 MGy and 20 MGy respectively.
The sedimentation equilibrium of dipolar particles in a ferrofluid is studied using experiment, theory, and computer simulation. A theory of the particle-concentration profile in a dipolar hard-sphere fluid is developed, based on the local-density approximation and accurate expressions from a recently introduced logarithmic free energy approach. The theory is tested critically against Monte Carlo simulation results for monodisperse and bidisperse dipolar hard-sphere fluids in homogeneous gravitational fields. In the monodisperse case, the theory is very accurate over broad ranges of gravitational field strength, volume fraction, and dipolar coupling constant. In the bidisperse case, with realistic dipolar coupling constants and compositions, the theory is excellent at low volume fraction, but is slightly inaccurate at high volume fraction in that it does not capture a maximum in the small-particle concentration profile seen in simulations. Possible reasons for this are put forward. Experimental measurements of the magnetic-susceptibility profile in a real ferrofluid are then analysed using the theory. The concentration profile is linked to the susceptibility profile using the second-order modified mean-field theory. It is shown that the experimental results are not consistent with the sample being monodisperse. By introducing polydispersity in the simplest possible way, namely by assuming the system is a binary mixture, almost perfect agreement between theory and experiment is achieved.
Mechanical models of damped low-gravity sloshing are developed using a proposed analytical method for arbitrary axisymmetric tanks. It is shown that (a) the complex amplitudes of the force and moment caused by the conventional mechanical model do not coincide with the complex amplitudes of the force and moment calculated from the modal equation of sloshing and (b) these differences arise not only from the damping ratio but also from the surface tension although the surface tension does not cause energy dissipation. A mechanical model for correcting these differences is developed. The mass of this correction model is found to be equal to the mass of the liquid that fills the domain bounded by the meniscus and the plane that includes the contact line of the meniscus with the tank wall. With decreasing Bond number, the correction model mass as well as the damping ratio increase and, therefore, the correction becomes important. The force and moment caused by the conventional uncorrected mechanical model have phase lag with respect to the force and moment calculated from the modal equation of sloshing near the resonant frequency. Therefore, the correction is important for the dynamics and control analysis of a space vehicle.
Chemical-looping combustion (CLC) has emerged as a promising technology for fossil fuel combustion which produces a sequestration ready concentrated CO2 stream in power production. A CLC system is composed with two reactors, an air and a fuel reactor. An oxygen carrier such as hematite (94%Fe2O3) circulates between the reactors, which transfers the oxygen necessary for the fuel combustion from the air to the fuel. An important issue for the CLC process is the selection of metal oxide as oxygen carrier, since it must retain its reactivity through many cycles. The primary objective of this work is to develop a global mechanism with respective kinetics rate parameters such that CFD simulations can be performed for large systems. In this study, thermogravimetric analysis (TGA) of the reduction of hematite (Fe2O3) in a continuous stream of CH4 (15%, 20%, and 35%) was conducted at temperatures ranging from 700 to 825 degrees C over ten reduction cycles. The mass spectroscopy analysis of product gas indicated the presence of CO2 and H2O at the early stage of reaction and H-2 and CO at the final stage of reactions. A kinetic model based on two parallel reactions, (1) first-order irreversible rate kinetics and (2) Avrami equation describing nucleation and growth processes, was applied to the reduction data. It was found, that the reaction rates for both reactions increase with, both, temperature and the methane concentration in inlet gas. Published by Elsevier B.V.
A computational simulation of magnetic positive positioning is used to model cryogenic propellant reorientation in reduced gravity. A magnetic bond number is defined for this process and preliminary data in the literature suggest that a threshold value limit may exist above which liquid reorientation will occur. Results of magnetic positive positioning simulations in two different small scale tanks are presented and evaluated. An analysis of the data is provided and evidence is presented which supports the conclusion that the magnetic Bond number may be a viable predictor of magnetically actuated propellant reorientation.
Liquid sloshing constitutes a broad class of problems of great practical importance with regard to the safety of liquid transportation systems, such as tank trucks on highways, liquid tank carriages on rail roads, ocean going vessels and propellant tanks in liquid rocket engines. The present work attempts to give a review of some selected experimental investigations carried out during the last couple of decades. This paper highlights the various parameters attributed to the cause of sloshing followed by effects of baffles, tank inclination, magnetic field, tuned liquid dampers, electric field etc. Further, recent developments in the study of sloshing in micro and zero gravity fields have also been reported. In view of this, fifteen research articles have been carefully chosen, and the work reported therein has been addressed and discussed. The key issues and findings have been compared, tabulated and summarized.
Sloshing of a magnetic fluid can be controlled through altering the
sloshing natural frequency by applying magnetic fields. The magnetic
field is applied by two permanent magnets. The intensity of the applied
magnetic field is changed by varying the position of the magnets and the
magnet type. The dynamic pressure responses on the inner wall surface
were used to gain an understanding of the sloshing phenomenon in this
investigation. Several frequency response spectra are obtained in each
experimental condition. These results indicated that the free surface
disturbance caused by the sloshing was suppressed by the applied
magnetic field.
An established biomimetic process for the synthesis of aqueous ferrofluids using polymers has been subjected to systematic microwave irradiation at different wattages primarily to see if the magnetization could be increased by microwave irradiation and if so how would it affect the stability of the fluid. Care has been taken to maintain ambient conditions of synthesis even after three cycles of microwave irradiation before oxidation and ten cycles after it, so as not to violate the basic principles of the process. Detailed characterization using, x-ray diffractometry, transmission electron microscopy, fourier transform infra-red spectroscopy, dynamic light scattering, thermo-gravimetric analysis, differential thermal analysis and vibrating sample magnetometry showed that these fluids containing iron oxide nanoparticles-poly(vinyl) alcohol nanocomposites are highly stable in the proportions established by us. Measurements at five different wattages double the saturation magnetization but the stability remains unaffected compared to the one without microwave irradiation, forcing us to believe that the incubation of the iron salt solution and the polymer in the right proportion before oxidation is what contributes to the stability and that increasing the number of cycles of microwave irradiation at this stage, perhaps, would have led to a more pronounced effect.
The current state of our knowledge of the burning characteristics of carbon, aluminum and boron slurries is discussed. Particle agglomeration, and in many cases the formation of semiporous shells increase the overall combustion time, thereby requiring a burner of longer characteristic length. Current thoughts about the probable causes of particle agglomeration, in a slurry fuel, are reviewed and the techniques of drop fragmentation as a means of eliminating large agglomerates are discussed. Large agglomerates burn slowly and are responsible for lower combustion efficiency, unacceptable combustion chamber deposits and an increased particulate emission in the exhaust. Possible applications of coal/water and coal oil/slurry fuels are discussed briefly in a separate section. Details of reaction kinetics of either metal or coal combustion are beyond the scope of this paper.
The surface responses of a magnetic fluid in a container subject to a magnetic field and vertical vibration are examined. Three kinds of observations were made in these experiments: mapping stability boundaries, determining nonlinear surface responses, and a comparison between cases with and without magnetic fields.
This paper presents a procedure to analyze the free and forced liquid sloshing motions in an axisymmetric tank of arbitrary shape at low-gravity environments. The free-vibration problem is solved by extending the analysis of Satterlee and Reynolds for a circular cylindrical tank with a flat bottom. The forced-motion problem is solved by first expanding the velocity potential, the interface wave height, and the forcing functions in terms of the normal mode shapes obtained in the free-vibration analysis. The solutions hold for any arbitrary horizontal translational motion of the tank.
Summary form only given. The treatment of cancer, in its present form, implies the corroboration of several therapeutic methods, including the hyperthermia. In general, the latter does not provide a therapy by itself, but is used rather as a complementary part during chemotherapy and radiotherapy. The scientific literature proves that the degradation of the stabilizing coating of nanoparticles from ferrofluids, due to biochemical processes, can in general lead to a degradation of the magnetic energy-heat converter properties; this may lead to an inefficiency of the ferrofluid use for oncologic hyperthermia. Starting from these considerations, we decided to investigate the behaviour of a medical ferrofluid infiltrated in a tumor and exposed to gamma-ray treatment. The study followed the effect of ferrofluid irradiation with doses specific to the intensive therapy. The ferrofluids studied were obtained by chemical precipitation of the magnetite, its dispersion in kerosene or in water and the stabilization with oleic acid or with dodecyl amine, respectively.
A tuned magnetic fluid damper (TMFD) is a dynamic absorber using a magnetic fluid. A characteristic of the TMFD is changing natural frequency of a magnetic fluid sloshing under a magnetic field. The magnetic fluid sloshing in a coaxial cylindrical container was analyzed theoretically under the axisymmetrical magnetic field. The theoretical results showed that a radial component of the magnetic field also changed the natural sloshing frequency. A policy of the suitable design of the TMFD was presented and the effect of the radial component of the magnetic field was verified experimentally.
Effective viscosity of magnetic fluid is calculated numerically based on the diffusion equation for the spherical particles with permanent magnetic moment. The result is compared with that of the classical constitutive equation proposed by Shliomis. It is found that unlike Shliomis's equation, the viscosity remains monovalued as a function of the shear rate. A new constitutive equation which reproduces the numerical result is proposed.
Sloshing is a phenomenon that occurs when a liquid with a free surface is severely agitated in a liquid storage container. In an axisymmetric container, even though the excitation is lateral, the liquid oscillates with rotational movement around the central axis of the container. This phenomenon is called swirling and may be unstable swirling or stable swirling. We measure the velocity profile of a sloshing magnetic fluid using an ultrasonic Doppler velocimetry method called UVP, and examine the relationship between internal velocity profiles and swirling phenomena, in particular, stable swirling phenomena. We calculated power spectra from the velocity data using a fast Fourier transform and observed that the most dominant peak in the power spectrum moved to higher frequencies as the magnetic field intensity was increased, whereas a derived peak at a lower frequency moved to lower frequencies as the magnetic field intensity was increased.
The effect of decrease of magnetization of kerosene and diester based ferrofluids after gamma-radiation has been observed. The gamma-radiation induced aggregation and sedimentation have been suggested for the explanation of experimental facts.
Ferrofluids are being considered as potential candidates both in basic and applied research owing to their novel optical and magneto-optical properties. We have synthesised surfactant (N-Cetyl-N,N,N-trimethylammonium bromide, CTAB)-coated nanoscale gadolinium oxide (Gd2O3) based ferrofluids and then irradiated by gamma (γ-) rays with doses in the range of 32 Gy–2.635 kGy. High-resolution transmission electron microscope (HRTEM) analysis shows that the particles have developed intragranular defects owing to γ-ray irradiation. Fourier transform infrared (FT-IR) and photoluminescence (PL) studies also support the formation of defect ordering upon irradiation. Further, PL study indicates abrupt change of the symmetry factor with increase in γ-dose. By viewing the nature of variation between relative intensity of the defect-related emission and dose-dependent symmetry factor, one can predict the tunability of PL response. A proper understanding of the PL response of the irradiated nanoscale rare-earth oxides would find new avenues for lasing and other optoelectronic/photonic devices.
This volume provides a useful guide to the basic properties of all types of chemical propellants, explaining their uses in various types of propulsion. This knowledge will enable the propulsion engineer to know the possibilities, and strengths and weaknesses, of many types of fuel, thus enabling him to cut through the copious, but often meaningless, data on the subject. (Author)
Heat transfer of a two-layer fluid system has been of great importance in a variety of industrial applications. For example, the phenomena of immiscible fluids can be found in materials processing and heat exchangers. Typically in solidification from a melt, the convective motion is the dominant factor that affects the uniformity of material properties. In the layered flow, thermocapillary forces can come into an important play, which was first emphasized by a previous investigator in 1958. Under extraterrestrial environments without gravity, thermocapillary effects can be a more dominant factor, which alters material properties in processing. Control and optimization of heat transfer in an immiscible fluid system need complete understanding of the flow phenomena that can be induced by surface tension at a fluid interface. The present work is focused on understanding of the magnetic field effects on thermocapillary convection, in order to optimize material processing. That is, it involves the study of the complicated phenomena to alter the flow motion in crystal growth. In this effort, the Marangoni convection in a cavity with differentially heated sidewalls is investigated with and without the influence of a magnetic field. As a first step, numerical analyzes are performed, by thoroughly investigating influences of all pertinent physical parameters. Experiments are then conducted, with preliminary results, for comparison with the numerical analyzes.
A combination of both experimental and computational simulation results have recently provided strong evidence that magnetic
positioning may be a feasible alternative technology for managing cryogenic propellants onboard spacecraft. One prerequisite
in the assessment of magnetic propellant management is the ability of predicting propellant reorientation in full-scale propellant
tanks. A computational simulation is used to model magnetically induced liquid oxygen (LOX) flows in reduced gravity. Simulations
of magnetic positive positioning of LOX are presented and the influence of the magnetic field and background acceleration
on reorientation timing is explored. A dimensionless reorientation time is sought to compliment the magnetic Bond number and
Bond number as an additional predictive correlating parameter for scaling this process. Evidence is provided that supports
the continued use of these correlating parameters to predict the magnetic fields required to reorient cryogenic propellants
in full-scale spacecraft tanks. Further, this study supports the conclusion that magnetic positive positioning appears to
be a viable emerging technology for cryogenic propellant management systems that merits further computational investigation
and space-based experimentation to establish the technology base required for future spacecraft design.
Experimental and computational studies have shown that a sufficiently strong magnetic field can influence a magnetically susceptible liquid. An improved simulation integrates an electromagnetic field model and incompressible flow model to predict fluid reorientation using realistic magnetic fields. Flow fields are presented incorporating several realistic magnetic fields to verify and validate the connectivity of the integrated models. Conclusions are drawn about the fidelity of the integrated simulation in modeling magnetically induced fluid flows. The simulation is used to model the application of magnetic positive positioning of LOX in a reduced gravity experiment utilizing a realistic magnetic field. Preflight experiment predictions of the performance of the magnetic field in reorienting LOX are presented and recommendations are made for future design.
Characteristics of a tuned magnetic fluid damper are examined. The optimal depth of a
magnetic fluid in a cylindrical container is calculated using a linear analysis of a
magnetic fluid sloshing. In order to avoid swirling in lower depth fluids, several
experiments using greater fluid depths are carried out and a good damping range is
obtained.
This paper presents a non-exhaustive overview of magnetic force formulations mainly used in ferrohydrodynamics. All of these formulations give the same global result but the local force density is different from each other. We propose to compare these formulations in order to highlight which one is the best representation of the local force density. In order to find a reference of local force distribution, computations have been carried out using the virtual work method on particles surrounded by thin layers of air. The whole particles and air have been homogenized to create a linear uniform material. Finally, force distributions have been computed and have been compared to the reference calculated by virtual work method.
This users manual is the second part of a two-part report describing the NASA Lewis CEA (Chemical Equilibrium with Applications) program. The program obtains chemical equilibrium compositions of complex mixtures with applications to several types of problems. The topics presented in this manual are: (1) details for preparing input data sets; (2) a description of output tables for various types of problems; (3) the overall modular organization of the program with information on how to make modifications; (4) a description of the function of each subroutine; (5) error messages and their significance; and (6) a number of examples that illustrate various types of problems handled by CEA and that cover many of the options available in both input and output. Seven appendixes give information on the thermodynamic and thermal transport data used in CEA; some information on common variables used in or generated by the equilibrium module; and output tables for 14 example problems. The CEA program was written in ANSI standard FORTRAN 77. CEA should work on any system with sufficient storage. There are about 6300 lines in the source code, which uses about 225 kilobytes of memory. The compiled program takes about 975 kilobytes.
This report details the results of a series of fluid motion experiments to investigate the use of magnets to orient fluids in a low-gravity environment. The fluid of interest for this project was liquid oxygen (LO2) since it exhibits a paramagnetic behavior (is attracted to magnetic fields). However, due to safety and handling concerns, a water-based ferromagnetic mixture (produced by Ferrofluidics Corporation) was selected to simplify procedures. Three ferromagnetic fluid mixture strengths and a nonmagnetic water baseline were tested using three different initial fluid positions with respect to the magnet. Experiment accelerometer data were used with a modified computational fluid dynamics code termed CFX-4 (by AEA Technologies) to predict fluid motion. These predictions compared favorably with experiment video data, verifying the code's ability to predict fluid motion with and without magnetic influences. Additional predictions were generated for LO2 with the same test conditions and geometries used in the testing. Test hardware consisted of a cylindrical Plexiglas tank (6-in. bore with 10-in. length), a 6,000-G rare Earth magnet (10-in. ring), three-axis accelerometer package, and a video recorder system. All tests were conducted aboard the NASA Reduced-Gravity Workshop, a KC-135A aircraft.
A theory of magnetic fluid sloshing in a solenoidal magnetic field is developed herein. It shows that (a) the free-surface waves on a magnetic fluid are dynamically similar to the waves on an ordinary liquid in a reduced gravity field, and (b) the apparent reduction in gravity depends on the strength of the applied magnetic field. But, a deviation from true low-gravity behavior occurs whenever the Bond number (ratio of effective gravitational force to surface tension force) is much smaller than 1.0 lite deviation is caused by a magnetic interaction that induces a jump in pressure across the free surface. To verify the conclusions of the theory and to evaluate the usefulness of magnetic sloshing as a low-g-avity sloshing simulation, an exploratory series of tests was conducted using a magnetic-colloid liquid, and a large solenoidal electromagnet. Measured slosh natural frequencies agreed well with theory, but the measured slosh damping was larger than predicted by existing correlation equations.