Download or read book Numerical Modeling of Ion Dynamics in a Carbon Nanotube Field ionized Thruster written by Sarah F. Michael and published by . This book was released on 2011 with total page 105 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotube field ionization technology has the potential to make ion propulsion feasible for use in micro and nano-satellites. To better understand the phenomenon and optimize the ion thruster design, it is useful to have an accurate model of the system. Numerical modeling of large-scale electron bombardment ion engines is a relatively mature field, but modeling of field-ionized ion engines is in its infancy. A simpler code may be appropriate for the early modeling stages of carbon nanotube field ionization technology; one such software package is spiffe. Spiffe is intended for modeling axisymmetric radio frequency guns, but it contains all the code necessary for basic modeling of ion optics in a field-ionized ion thruster. This work analyzes the feasibility of spiffe software for use in modeling field-ionized ion thrusters. It also provides detailed procedures for its use. In this work, spiffe is first verified to agree with theoretical predictions of limits in a one-dimensional approximation using electrons. Two primary geometries and their boundary conditions are investigated. The geometry is then varied to test the limits of the one-dimensional approximation. This was further altered to simulate singly-charged Argon ions and verified against theoretical onedimensional limits. A supplemental user's guide was developed to aid students with minimal programming experience to quickly become familiar with the methods used in spiffe and the impact of program options on the results. A guide to quickly post-processing the data was also developed.
Download or read book Numerical Modelling and Optimisation of Radio frequency Ion Thrusters written by Martin Felix Closs and published by Herbert Utz Verlag. This book was released on 2002 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Design and Installation of a Field Ionization Test Chamber for Ion Thrusters written by Paul W. Camp and published by . This book was released on 2011 with total page 75 pages. Available in PDF, EPUB and Kindle. Book excerpt: The utilization of carbon nanotube arrays for field ionization in ion thrusters allows for a substantial reduction in thruster size and weight. The availability of miniature ion thrusters may enable the development of a suitable propulsion system for nano- and picosatellites, and can realize substantial weight, volume, and cost savings in existing satellite platforms. This research focuses on the design of a field ionization test chamber that can be used to determine a comprehensive performance metric for the carbon nanotube field ionization micro-ion thruster (CNTFIMIT). Using the knowledge gathered from two previously employed test chamber designs, a third generation apparatus with higher precision and improved capabilities is constructed. This new design incorporates a mass flow controller for propellant flow rate measurements, a high-voltage source-measure unit for ionization current measurements, and a linear shift with position feedback for adjusting the distance between the carbon nanotubes and the counter electrode during field-ionization. The design emphasizes user-friendly operation by simplifying the sample exchange and by reducing the chamber volume under vacuum for a faster turn-around time between experiments. The proposed design is highly modular, allowing for easy installation of additional analytic capabilities and other future upgrades.
Download or read book A Carbon Nanotube Pillar Array Ionizer for Miniature Ion Thruster Applications written by and published by . This book was released on 2008 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt: Satellites of the 'micro' class and smaller require scalable propulsion systems that minimize mass, volume and power. With a substantial reduction in ionizer size, ion thrusters may fulfill all of these requirements. This work explores field ionization with nanotube arrays for a highly-scalable ionizer. Fabrication and testing of carbon nanotube pillar array (CPA) ionizers is undertaken at the Nanotechnology Center, NASA Ames Research Center. The devices are built using conventional photolithography, ion beam sputtering and thermal chemical vapor deposition processes. Fabrication tribulations and solutions discovered are discussed. Testing is performed under both ultrahigh vacuum and low-pressure static gas atmospheres, with the devices configured as field electron emitters and as field gas ionizers. Argon is used as a propellant to demonstrate its suitability as an alternative to xenon. The four test samples turn on at applied fields as low as 5.3 V/um and produce ion current densities greater than 10 mA/cm2. Tested as field emitters, the devices show very strong correlation with Fowler-Nordheim theory and exhibit field enhancement factors as high as 1500. A qualitative analysis is made of pre- and post-test CPA characterizations.
Download or read book Numerical Simulation of Ion Thruster Optics written by and published by . This book was released on 2003 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fully Kinetic Numerical Modeling of a Plasma Thruster written by James Joseph Szabo and published by . This book was released on 2001 with total page 375 pages. Available in PDF, EPUB and Kindle. Book excerpt: A Hall effect plasma thruster with conductive acceleration channel walls was numerically modeled using 2D3V Particle-in-Cell (PIC) and Monte-Carlo Collision (MCC) methodolo- gies. Electron, ion, and neutral dynamics were treated kinetically on the electron time scale to study transport, instabilities, and the electron energy distribution function. Axisymmet- ric R-Z coordinates were used with a non-orthogonal variable mesh to account for important small-scale plasma structures and a complex physical geometry. Electric field and sheath structures were treated self-consistently. Conductive channel walls were allowed to float electrically. The simulation included, via MCC, elastic and inelastic electron-neutral colli- sions, ion-neutral scattering and charge exchange collisions, and Coulomb collisions. The latter were also treated through a Langevin (stochastic) differential equation for the particle trajectories in velocity space. Ion-electron recombination was modeled at the boundaries, and neutrals were recycled into the flow. The cathode was modeled indirectly by inject- ing electrons at a rate which preserved quasineutrality. Anomalous diffusion was included through an equivalent scattering frequency. Free space permittivity was increased to allow a coarser grid and longer time-step. A method for changing the ion to electron mass ratio and retrieving physical results was developed and used throughout. Results were compared with theory, experiments. Gradients and anisotropy in electron temperature were observed. Non-Maxwellian electron energy distribution functions were observed. The thruster was numerically redesigned; substantial performance benefits were predicted.
Download or read book Numerical Modelling of a Radio frequency Micro Ion Thruster written by Michael Meng-Tsuan Tsay and published by . This book was released on 2006 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: A simple performance model is developed for an inductively-coupled radio-frequency micro ion thruster. Methods of particle and energy balance are utilized for modeling the chamber plasma discharge. A transformer model is incorporated in the equations of energy balance for investigating the effect of plasma on the primary circuit and for calculating the absorbed power by the plasma. A simple and one-dimensional ion extraction model is developed based on experimental observation and the result is validated with experimental data. Performance of the RF micro ion thruster is satisfactory with thrust and specific impulse of approximately 2 mN and 2000 seconds, respectively. Comparison is made with a miniature bombardment-type ion thruster, and the RF ion thruster is found to be more efficient when the coupling efficiency is above 80%. Optimization in driving frequency increases power absorption and ionization fraction tremendously. It has a positive but limited effect on propulsive performance as the ion beam current is space-charge limited.
Download or read book Two dimensional Numerical Modeling of Radio Frequency Ion Engine Discharge written by Michael Meng-Tsuan Tsay and published by . This book was released on 2010 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt: Small satellites are gaining popularity in the space industry and reduction in spacecraft size requires scaling down its propulsion system. Low-power electric propulsion poses a unique challenge due to various scaling penalties. Of high-performance plasma thrusters, the radio-frequency ion engine is most likely to succeed in scaling as it does not require an externally applied magnetic field and is structurally simple to construct. As part of a design package an original two-dimensional simulation code for radio-frequency ion engine discharge is developed. The code models the inductive plasma with fluid assumption and resolves the electromagnetic wave in the time domain. Major physical effects considered include magnetic field diffusion and coupling, plasma current induction and ambipolar plasma diffusion. The discharge simulation is benchmarked with data from an experimental thruster. It shows excellent performance in predicting the load power and the internal power loss of the plasma. Predictability of anode current depends on the operating power but is generally adequate. Optimum skin depth on the order of half of chamber radius is suggested by the simulation. The code also demonstrates excellent scaling ability as it successfully predicts the performance of a smaller thruster with errors less than 10%. Using the code a brief optimization study was conducted and the results suggest the maximum thrust efficiency does not necessarily occur at the same frequency that maximizes the power coupling efficiency of the matching circuit.
Download or read book Numerical Simulation of Ion Thruster and Stationary Plasma Thruster Exhaust Beam Electrostatic Potential Fields written by Michael Sanghun Rhee and published by . This book was released on 1995 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Models of Hall Thruster Ionization Oscillations written by Ewan Samuel Kay and published by . This book was released on 2016 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, low frequency ionization oscillations in Hall thrusters resembling the breathing mode are studied through computational simulation. The relationship between wall erosion and discharge current oscillations is analyzed using particle-in-cell simulation, and a series of parametric simulations is used to determine the effects of macro-particle size, floating body potential, electron injection region, ion time step size, grid refinement, heavy particle mass reduction, and an artificial permittivity factor. These studies help to determine the parameters that will produce accurate simulations in the future, and identify the parts of the model that need improvement. One-dimensional steady and unsteady Hall thruster models, as well as a generalized sheath model are then developed, and the effects of the parameters that determine stability on the thruster’s operating conditions are determined.
Download or read book Micropropulsion for Small Spacecraft written by Michael Matthew Micci and published by AIAA. This book was released on 2000 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 1044 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Evaluation of Low current Orificed Hollow Cathodes written by Matthew Thomas Domonkos and published by . This book was released on 1999 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Reusable Booster System written by National Research Council and published by National Academies Press. This book was released on 2013-01-10 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: On June 15, 2011, the Air Force Space Command established a new vision, mission, and set of goals to ensure continued U.S. dominance in space and cyberspace mission areas. Subsequently, and in coordination with the Air Force Research Laboratory, the Space and Missile Systems Center, and the 14th and 24th Air Forces, the Air Force Space Command identified four long-term science and technology (S&T) challenges critical to meeting these goals. One of these challenges is to provide full-spectrum launch capability at dramatically lower cost, and a reusable booster system (RBS) has been proposed as an approach to meet this challenge. The Air Force Space Command asked the Aeronautics and Space Engineering Board of the National Research Council to conduct an independent review and assessment of the RBS concept prior to considering a continuation of RBS-related activities within the Air Force Research Laboratory portfolio and before initiating a more extensive RBS development program. The committee for the Reusable Booster System: Review and Assessment was formed in response to that request and charged with reviewing and assessing the criteria and assumptions used in the current RBS plans, the cost model methodologies used to fame [frame?] the RBS business case, and the technical maturity and development plans of key elements critical to RBS implementation. The committee consisted of experts not connected with current RBS activities who have significant expertise in launch vehicle design and operation, research and technology development and implementation, space system operations, and cost analysis. The committee solicited and received input on the Air Force launch requirements, the baseline RBS concept, cost models and assessment, and technology readiness. The committee also received input from industry associated with RBS concept, industry independent of the RBS concept, and propulsion system providers which is summarized in Reusable Booster System: Review and Assessment.
Download or read book Cold Plasma Cancer Therapy written by Michael Keidar and published by Morgan & Claypool Publishers. This book was released on 2019-04-01 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cold atmospheric plasma (CAP) emerges as a possible new modality for cancer treatment. This book provides a comprehensive introduction into fundamentals of the CAP and plasma devices used in plasma medicine. An analysis of the mechanisms of plasma interaction with cancer and normal cells including description of possible mechanisms of plasma selectivity is included. Recent advances in the field, the primary challenges and future directions are presented.
Download or read book Carbon Nanotube Reinforced Polymers written by Roham Rafiee and published by Elsevier. This book was released on 2017-10-06 with total page 588 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon Nanotube-Reinforced Polymers: From Nanoscale to Macroscale addresses the advances in nanotechnology that have led to the development of a new class of composite materials known as CNT-reinforced polymers. The low density and high aspect ratio, together with their exceptional mechanical, electrical and thermal properties, render carbon nanotubes as a good reinforcing agent for composites. In addition, these simulation and modeling techniques play a significant role in characterizing their properties and understanding their mechanical behavior, and are thus discussed and demonstrated in this comprehensive book that presents the state-of-the-art research in the field of modeling, characterization and processing. The book separates the theoretical studies on the mechanical properties of CNTs and their composites into atomistic modeling and continuum mechanics-based approaches, including both analytical and numerical ones, along with multi-scale modeling techniques. Different efforts have been done in this field to address the mechanical behavior of isolated CNTs and their composites by numerous researchers, signaling that this area of study is ongoing. Explains modeling approaches to carbon nanotubes, together with their application, strengths and limitations Outlines the properties of different carbon nanotube-based composites, exploring how they are used in the mechanical and structural components Analyzes the behavior of carbon nanotube-based composites in different conditions
Download or read book Carbon Nanotubes written by M. Meyyappan and published by CRC Press. This book was released on 2004-07-28 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes, with their extraordinary mechanical and unique electronic properties, have garnered much attention in the past five years. With a broad range of potential applications including nanoelectronics, composites, chemical sensors, biosensors, microscopy, nanoelectromechanical systems, and many more, the scientific community is more moti
