Hall Thruster Erosion

Hall thruster (HT) is one of the thrusters that are systematically applied in space. If to compare HT with plasma ion thrusters, it has lower lifetime and specific impulse. HT has a set of advantages, and that is why interest to this plasma thruster is high. It has relatively simple design and technology of production. HT does not require a complex power supply unit, and it is very important for spacecraft. Propulsion system on the base of HT has lower mass, simpler technology, and less time of production. One of the main HT characteristics that require improvement is the lifetime of thruster. As it is known, one of the main factors that decrease thruster lifetime is the wear of discharge chamber (DCh). With the analysis of demands to HT, it is understandable that the required lifetime is more than 10 years. So the question about lifetime of the HT is still open. This chapter presents the overview of the thruster elements lifetimes and the overview of methods of thruster erosion investigation. It shows advantages and disadvantages of optical methods of DCh erosion rate investigation. Chapter presents modified method of optical investigation. The results of HT research under various modes of operation and results of tests with different ceramic are presented

O uso dos diferentes tipos de cimentos de ionômero de vidro restauradores utilizados na prática clínica em cavidades classe v: revisão de literatura / The use of different types of restorative glass ionomer cements used in clinical practice in class v cavities: literature review

Os materiais restauradores têm o desafio de proporcionar ao paciente uma restauração adaptada estética e duradoura, dependendo do tipo de cavidade esse resultado é um verdadeiro desafio, um exemplo disso são as restaurações em classe V, que apresentam dificuldades devido o íntimo contato do material restaurador com a saliva. Nesses tipos de caso o uso do cimento de ionômero de vidro é a primeira escolha, pois no quesito preservação da estrutura dental, onde, para essa cavidade deve-se ter o mínimo de desgaste é o cimento com melhores propriedades, pois possui adesão química e coeficiente de expansão térmica semelhante ao da estrutura dentária, atuando também no processo de remineralização através da liberação de flúor. Contudo, mesmo que indicado para esse tipo de cavidade pode ocorrer microinfiltrações e fraturas, assim o aprimoramento desses cimentos busca ao máximo reduzir esse tipo de problema. Atualmente o mercado conta com uma diversidade de apresentações dos cimentos de ionômero de vidro para a prática clínica, a fim de viabilizar adaptação marginal, evitar recidiva de cárie e consequentemente a perda da restauração.  Esse artigo mostra que existe necessidade de realizar mais pesquisas sobre os diferentes tipos de cimento de ionômero de vidro utilizados em cavidades classe V na prática clínica, mas aponta o uso desse cimento como melhor opção em virtude de sua biocompatibilidade

DINÁMICA DEL USO DEL SUELO Y SU RELACIÓN CON LA CALIDAD DE VIDA DE LOS HABITANTES DE LA ISLA DE CARATATEUA, BELÉM, PARÁ

RESUMO: O presente trabalho teve como objetivo avaliar a dinâmica do uso do solo, entre os anos de 1984 e 2015, por meio do processamento digital de imagens, e aplicação de questionários para avaliar a relação do uso do solo com a qualidade de vida dos moradores da ilha de Caratateua, Belém, Pará. Foram utilizadas imagens do satélite LANDSAT-5, bandas 3, 4 e 5, dos anos 1984, 1999, 2008 e 2015, as quais foram submetidas à classificação supervisionada por máxima verossimilhança. Posteriormente, obteve-se mapas com classes de uso do solo, sendo mais expressivas a Vegetação Densa, Capoeira (Floresta Secundária), Solo Exposto e Área Urbana. Foram aplicados 50 questionários com a pergunta: Quais os principais problemas que interferem na qualidade de vida da população da ilha de Caratateua? O período entre os anos de 1984 a 1989 foi o de maior crescimento urbano na ilha. A falha na gestão ambiental e urbanística, associados ao processo de crescimento desordenado, que, aliado a outros fatores, resultou no aumento desordenado de áreas urbanas e vem gerando impactos sociais, em especial com o aumento da violência e da carência de saneamento básico, e ambientais, por meio do uso indiscriminado dos recursos naturais e do solo.PALAVRAS-CHAVE: Monitoramento ambiental, Processamento de imagens digitais,  Sensoriamento remoto.ABSTRACT: The objective of this study was to evaluate the dynamics of soil use between 1984 and 2015 through digital image processing and questionnaires to evaluate the relationship between soil use and the quality of life of the (LANDSAT-5), bands 3, 4 and 5, from 1984, 1999, 2008 and 2015, which were submitted to supervised classification by maximum likelihood. Subsequently, maps with classes of land use were obtained, being more expressive the Dense Vegetation, Capoeira (Secondary Forest), Exposed Ground and Urban Area. Fifty questionnaires were applied with the question: What are the main problems that interfere in the quality of life of the population of the island of Caratateua? The period between the years 1984 to 1989 was the one of greater urban growth in the island. The lack of environmental and urban management associated with the disorderly growth process, which, combined with other factors, has resulted in the disorderly increase of urban areas and has generated social impacts, especially with increasing violence and lack of basic sanitation, and through the indiscriminate use of natural resources and soil.KEYWORDS: Environmental monitoring, Processing of digital images, Remote sensing. RESUMEN: El presente trabajo tuvo como objetivo evaluar la dinámica del uso del suelo, entre los años 1984 y 2015, por medio del procesamiento digital de imágenes, y aplicación de cuestionarios para evaluar la relación del uso del suelo con la calidad de vida de los habitantes de los años 1984, 1999, 2008 y 2015, las cuales fueron sometidas a la clasificación supervisada por máxima verosimilitud. Posteriormente, se obtuvieron mapas con clases de uso del suelo, siendo más expresivas la Vegetación Densa, Capoeira (Bosque Secundaria), Solo Exposto y Área Urbana. Se aplicaron 50 cuestionarios con la pregunta: ¿Cuáles son los principales problemas que interfieren en la calidad de vida de la población de la isla de Caratateua? El período entre los años 1984 a 1989 fue el de mayor crecimiento urbano en la isla. La falla en la gestión ambiental y urbanística, asociados al proceso de crecimiento desordenado, que, aliado a otros factores, resultó en el aumento desordenado de áreas urbanas y viene generando impactos sociales, en especial con el aumento de la violencia y la carencia de saneamiento básico, y ambientales, a través del uso indiscriminado de los recursos naturales y del suelo.PALABRAS CLAVE: Detección remota, Monitoreo ambiental, Procesamiento de imágenes digitales

Метод визначення відносної швидкості ерозії ізоляторів стаціонарного плазмового двигуна

Despite the fact that for many years the stationary plasma thruster (SPT) has been used in space, this technology has not yet been fully studied. One of the research directions to improve SPT characteristics is the increase of thruster lifetime. This can be achieved with the research of the discharge chamber (DCh) walls erosion rate as a function of different thruster operational modes.The analysis of the SPT DCh wear rate diagnostics methods was carried out. It is shown that the considered methods cannot provide measurements of the insulators erosion rate separately during the experiment.The method of optical emission spectroscopy with plasma scanning through collimator (OESSC) was developed. The method allows registration of radiation separately for each of SPT DCh walls directly during the experiment. According to this, the experimental time of different SPT operational regimes research was reduced by 98 %.Experimental equipment of the OESSC method was developed, produced and tested. It consists of the high-resolution spectral block with the range of 240...820 nm and the optical detector positioning system.A set of experiments were provided with the OESSC method. As a result, the inner and outer insulators erosion rates are researched as functions of thruster operational regimes. It is shown that for the outer and inner coils currents of 5 and 6 A, respectively, there is a uniform wear of DCh walls. For such SPT operational regime, the difference in the insulators specific relative erosion rates is 2 %.The results of the OESSC method measurements allowed increasing the anode block lifetime significantlyРазработан метод оптической эмиссионной спектроскопии со сканированием плазмы через коллиматор (ОЭССК), который позволяет регистрировать излучение отдельно с каждой стенки разрядной камеры (РК) стационарного плазменного двигателя. В результате эксперимента методом ОЭССК получены зависимости относительной скорости эрозии внутреннего и наружного изоляторов от токов катушек. Определены токи катушек, при которых наблюдается практически равномерный износ стенок РК  Розроблено метод оптичної емісійної спектроскопії зі скануванням плазми через коліматор (ОЕССК). який дозволяє реєструвати випромінювання окремо з кожної стінки розрядної камери (РК) стаціонарного плазмового двигуна. В результаті експерименту методом ОЕССК отримані залежності відносної швидкості ерозії внутрішнього і зовнішнього ізоляторів від струмів котушок. Визначено струми котушок, при яких спостерігається практично рівномірний знос стінок РК

Розробка зіткненно-радіаційної моделі ксенону для діагностики плазми холлівського двигуна

Hall Effect thrusters (HET) have demonstrated its applicability on satellites for the Low earth orbit (LEO), Geo-stationary earth orbit (GEO) and long duration missions. High thrust density and long lifetimes are attractive parameters of the HET. In order to improve the thruster performance and lifetimes, decades of efforts are made to understand the plasma physics.Several intrusive and non-intrusive diagnostics techniques are employed for HET investigation. Simple and precise diagnostics technique is attractive to delineate the characteristics of the thruster. Optical emission spectroscopy provides several advantages over the other methods which are used for the HET diagnostics. Using this diagnostics tool in correlation with the collisional radiative model, the information of electron kinetics is extracted instantaneously.Collisional radiative model is developed by using the xenon near-infrared emission lines. This kinetic model can be used to determine the local electron temperature with error less than 15 % for investigating the HET physics.Холловские двигателя являются перспективным типом плазменного двигателя, который нашел свое применение в космосе. Несмотря на это, с каждым годом отмечается рост требований к xолловской двигателей. Разработка современных моделей холловской двигатели нуждается в совершенствовании теоретической и диагностической базыХоллівські двигуни є перспективним типом плазмового двигуна, який знайшов своє застосування в космосі. Незважаючи на це, з кожним роком відбувається зростання вимог до холлівських двигунів. Розробка нових сучасних моделей холлівських двигунів потребує вдосконалення теоретичної і діагностичної баз

Method for the Erosion Rate Measurements of Stationary Plasma Thruster Insulators

Despite the fact that for many years the stationary plasma thruster (SPT) has been used in space, this technology has not yet been fully studied. One of the research directions to improve SPT characteristics is the increase of thruster lifetime. This can be achieved with the research of the discharge chamber (DCh) walls erosion rate as a function of different thruster operational modes.The analysis of the SPT DCh wear rate diagnostics methods was carried out. It is shown that the considered methods cannot provide measurements of the insulators erosion rate separately during the experiment.The method of optical emission spectroscopy with plasma scanning through collimator (OESSC) was developed. The method allows registration of radiation separately for each of SPT DCh walls directly during the experiment. According to this, the experimental time of different SPT operational regimes research was reduced by 98 %.Experimental equipment of the OESSC method was developed, produced and tested. It consists of the high-resolution spectral block with the range of 240...820 nm and the optical detector positioning system.A set of experiments were provided with the OESSC method. As a result, the inner and outer insulators erosion rates are researched as functions of thruster operational regimes. It is shown that for the outer and inner coils currents of 5 and 6 A, respectively, there is a uniform wear of DCh walls. For such SPT operational regime, the difference in the insulators specific relative erosion rates is 2 %.The results of the OESSC method measurements allowed increasing the anode block lifetime significantl

РЕЗУЛЬТАТЫ ИСПЫТАНИЙ ЭМИТТЕРА ДЛЯ МИКРОКАТОДОВ

The article presents simulation results and experimental data obtained during the emitter investigation in diode mode of activation process and emitter operating parameters, which can used in cathodes with a discharge current range up to 0,5 A and a power consumption not more than 10 W. The article presents the results of emitter assembling thermal conditions modeling. It is found that the activation time of the emitter in the diode mode operation is about 18 hours. It is shown that the experimentally confirmed current density of the activated emitter for a microcathode was 1,25 A cm2, but the emitter worked in underheated mode, which requires further improvement in the design of the cathode emitter assembling in order to reduce thermal losses. В статье изложены результаты моделирования и экспериментальные данные, полученные при исследовании в диодном режиме процесса активации и рабочих параметров эмиттера для катодов с разрядным током до 0,5 А и потребляемой мощностью не более 10 Вт. В статье приведены результаты моделирования теплового состояния конструкции эмиттерного узла. Получено, что время активации эмиттера в диодном режиме работы составляет порядка 18 часов. Показано, что экспериментально подтвержденная плотность тока активированного эмиттера для микрокатода составила 1,25 А/см2, однако эмиттер работал в недогретом режиме, что требует дальнейшего усовершенствования конструкции эмиттерного узла катода с целью снижения тепловых потерь

ИССЛЕДОВАНИЕ ПРОЧНОСТНЫХ СВОЙСТВ ТЕРМОДРОССЕЛЯ

The article presents an analysis of the thermo-throttle construction under the influence of starting and thermal loads, namely broadband harmonic and random vibration, shock and pace-temperature-voltage during operation. The results of preliminary calculations of own resonant frequencies (modal analysis), are shown the presence of the resonance frequencies in the region below 2000 Hz, within the range of broadband random vibration rocket. Also it is defined strain arising as a consequence of thermal expansion during operation. It is shown that stress and strain in structural elements of the engine do not exceed the allowable values for the materials of which these parts are made.В статье представлен анализ конструкции термодросселя под действием стартовых и тепловых нагрузок, а именно гармонической и широкополосной случайной вибрации, ударных нагрузок и температурных напряжений во время работы. Приведены результаты предварительных расчетов на собственные резонансные частоты (модальный анализ), которые показали наличие резонансных частот в области ниже 2000 Гц, входящих в диапазон широкополосной случайной вибрации ракетоносителя. Также определены напряжение возникающие в следствии температурных расширений в процессе работы. Показано, что напряжения и деформации в элементах конструкции термодросселя не превышают допустимых значений для материалов, из которых изготовлены данные детали

РАЗРАБОТКА ВАКУУМНОЙ ВЫСОКОТЕМПЕРАТУРНОЙ ПЕЧИ С МИНИМАЛЬНОЙ НЕРАВНОМЕРНОСТЬЮ ТЕМПЕРАТУРЫ В РАБОЧЕЙ ЗОНЕ

In article is described necessity to provide maxim temperature uniformity in the zone of vacuum soldering and annealing of electric propulsion unit details. The methodology of vacuum heater with minimum temperature nonuniformity development is described. It is proposed an alternative for three section heater – a heater with variable section. It is shown, that increasing of cylindrical hater central part section is leaded to reducing of Joule heat, which deposited in this part, and providing heat rearrangement by heater length. It is demonstrated by modeling that it is a capability to reduce temperature nonuniformity on complex detail to 10-15° for temperature rage 1100-1200 °C The construction of heater with variable section is designed. В статье раскрыта необходимость обеспечения максимальной равномерности температуры в зоне вакуумной пайки и отжига деталей электроракетных двигательных установок. Описано методику разработки вакуумной печи с минимальной температурной неравномерностью. Предложена альтернативная трехзонному нагревателю конструк­ция, а именно нагреватель с переменным сечением. Показано, что увеличение сечения центральной части цилиндрического нагревателя приводит к снижению доли джоулева тепла, выделяемой в данной зоне, что обеспечивает перераспределение тепловой мощ­ности по длине нагревателя. Путем моделирования продемонстрирована возможность снижения температурной неравномерности на детали сложной формы до 10-15° при 1100-1200° С. Разработана конструкция нагревателя

КОНФИГУРАЦИЯ ВНЕШНЕГО МАГНИТНОГО ПОЛЯ МАЛОМОЩНОГО ГЕЛИКОННОГО ЭРД

The paper presents construction and working princi ples of helicon plasma thruster, expends experimental investigation results of outer magnetic field configuration influence on low power helicon thruster efficiency in operating frequency range between 10-14 MGs and RF power level up to 50 W. Developed outer magnetic field configuration and its features are presented. It is shown that applying of developed configuration allow to increase thrust efficiency of low power helicon thruster up to 13-19% in consumption power range 10-50 W and magnetic inductance level lower than 115 mTl. Scientific novelty and practical significance of done activity are presented in article. Further modernization ways of developed outer magnetic field configuration are outlined.В статье приведены конструкция и принцип работы геликонного ЭРД, изложены результаты экспериментального исследования влияния конфигурации внешнего магнитного поля на эффективность работы маломощного геликонного двигателя с рабочей частотой 10-14 МГц и уровнем ВЧ мощности до 50 Вт. Представлена разработанная конфигурация внешнего магнитного поля, описаны ее особенности. Показано, что применение данной конфигурации позволяет повысить тяговый к.п.д. маломощного геликонного двигателя до 13-19% в диапазоне мощности 10-50 Вт и индукции внешнего магнитного поля менее 115 мТл. Изложена научная новизна и практическая значимость проведенных работ. Намечены пути дальнейшего совершенствования разработанной конфигурации внешнего магнитного поля