Статьи журнала - Siberian Aerospace Journal
Все статьи: 341
Статья научная
According to the specific energy consumption, the shaping processes are arranged in three energy levels. Electrophysical and electrochemical methods of metal processing are at the third level, where the specific energy consumption is more than 6·104 J/cm3. The analysis of the literature data showed the inconsistency of the specific costs of some authors. The specific energy consumption of electrical contact processing cannot be commensurate with the costs of electrochemical processing due to the different sizes of the particles removed from the surface of the workpiece. There are no literature data on the specific energy consumption of electro-contact-chemical treatment of metals with a vibrating instrument in the electrolyte, therefore, experiments have been carried out with the fixation of current, voltage and interelectrode gap oscillograms. The method of calculation of specific energy consumption according to the oscillograms of the process is given. The energy costs for vibration of the electrode-tool are calculated, which are an order of magnitude less for electro-contact-chemical treatment. When the vibration amplitude decreases or the voltage on the electrodes increases, the process in the interelectrode gap turns into dimensional arc processing. When electro-contact-chemical treatment of metals with a vibrating tool in water, the specific energy consumption is equal to (3.5–3.8) · 105 J/cm3, which corresponds to electrocontact treatment. It is assumed that the use of aqueous solutions of neutral salts will lead to a reduction in energy costs.
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Статья научная
Active development of science-intensive technologies in the aerospace industry requires consideration of the operation of devices and instruments under extreme conditions; it is important to study the degradation of materials during rapid heating and cooling. On the basis of the theoretical and experimental work performed, the authors of the paper consider the degradation of cadmium telluride detectors caused by the development and evolution of a network of point defects resulting from pulsed exposure with a heat dose of about 1,000º С for no more than 10 s, simulating an extreme situation of a short circuit near the detector or direct heating by light pulses. The study showed that the crystalline material quickly degrades under such extreme conditions due to the rapid evolution of the defect network. The phenomenological model of the formation and distribution of defects during short-term exposure of the detector to thermal radiation has been improved. Electron microscopic studies of samples exposed to pulsed infrared radiation showed the development of a dense defect network, vacancy and interstitial defects, their clusters and other damage in all samples.
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Spraying plasmatron coatings with powder supply to plasma flow
Статья научная
The efficiency of using plasma energy when applying coatings is largely determined by the design of a plasma-tron. The main difference of the developed plasmatron PM-1 is the supply of transporting gas with powder to the plaza flow, which allows us to ensure more efficient and uniform heating of the material being sprayed. This paper presents the results of measuring a material usage factor (MUF), which is an important and indicative characteristic of plasmatrons, showing their economy and productivity. The authors calculated the cost of electricity and con-ducted studies of the sprayed samples for thermal shock.
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Статья научная
The article presents the problem of optimizing the structure of information processing computer appli-ances for real-time control systems used, among other things, in the rocket and space industry. In addition, the features of this problem that affect the choice of optimization methods are studied. It’s concluded that this problem can be effectively solved using evolutionary optimization methods. Existing performance models allow you to determine the minimum hardware configuration of a multi-processor computing system. The approach proposed in this article allows us to find configurations that have hardware redundancy (compared to the minimum configuration), but, due to this, have a greater probability of being in states that provide performance sufficient to achieve the goals of functioning of the designed real-time control system. The described approach is more flexible than simply duplicating all hardware components of the minimum configuration, which can be used to reduce the cost of creating and operating the designed control system. The proposed model can be used to optimize the performance of multiprocessor hardware and software complexes of real-time control systems. At the same time, it should be taken into account that the resources allocated for the creation and operation of the hardware and software complex are always limited. There-fore, it is advisable to consider the problem of performance optimization as a multi-criterion: one criterion will be performance, and the other-the cost of creating a hardware and software complex.
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Статья научная
The S-box is the most important component of modern cryptographic algorithms which largely determines the quality of cryptographic transformation. The modern method of estimating the S-boxes quality employs their representation as component Boolean functions to which cryptographic quality criteria are applied. Such criteria include: nonlinearity, correlation immunity, an error propagation criterion, and a strict avalanche criterion. Nevertheless, it is obvious that a cryptanalyst is not constrained in the ways of representing the cipher components, in particular, using the functions of many-valued logic. The design features of modern cryptographic algorithms allow their representation in the form of 4-logic functions, which determines the need to research cryptographic properties of the S-boxes represented as component 4-functions. In the literature today there are methods for measuring the nonlinearity of 4-functions; nevertheless, there are no similar methods for researching the differential properties of 4-functions, in particular, involving their compliance with the strict avalanche criterion. In this paper the strict avalanche criterion is generalized to the case of 4-functions and the compliance of the S-boxes component 4-functions of the “Magma” cryptoalgorithm to the strict avalanche criterion has been researched. All balanced 4-functions of length N = 16 satisfying the strict avalanche criterion were synthesized using the restricted brute-force method. The basic properties of the constructed class of 4-functions are determined, and bijective S-boxes based on them are constructed. It has been established that S-boxes of length N = 16 satisfying the strict avalanche criterion, both in terms of component Boolean functions and in terms of 4-functions, also possess optimal nonlinear properties. This circumstance allows us to recommend S-boxes satisfying the strict avalanche criterion of component 4-functions for use in modern cryptographic algorithms.
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Structural-phase state and properties of hypereutectic silumin treated with a pulsed electron beam
Статья научная
Hypereutectic silumin composition are promising modern materials of wide application (mechanical engineering, aviation, instrumentation, medicine, etc.). Disadvantages of hypereutectic silumin, significantly limiting their scope of application, are pores and cavities, large (about 100 µm) inclusions of lamellar and needle-shaped second phases. As a result of the studies carried out in this work, the possibility of forming structural-phase states in the surface layer of silumin, the size and morphology of which can purposefully change in the range from tens of micrometers to tens of nanometers, is demonstrated. The irradiation modes that allow more than 5 times to increase the microhardness (15 J/cm2, 150 µs, 0.3 s–1, 5 imp.) and more than 3 times to increase the wear resistance (50 J/cm2, 150 µs, 0.3 s–1, 5 imp.) of silumin were revealed.
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Статья научная
The purpose of this work is to reveal the patterns of formation of the structure of the surface layer of high-chromium steel subjected to nitriding in a low-pressure gas discharge plasma using a plasma genera-tor with a hot cathode "PINK". Heating of the samples to the nitriding temperature was carried out by the ionic component of the plasma, as well as by the electron and ionic components of the plasma (elion mode). The object of the study was heat-resistant corrosion-resistant steel of the austenitic class grade 20X23H18 (foreign analogue is AISI 310S). The relevance of research is due to the relatively low level of hardness and wear resistance of steels of this class. Nitriding of steel was carried out on the TRIO installation, retro-fitted with a switching unit for implementing the aelion (electronic and ionic) processing mode. It has been established that the thickness of the hardened layer is (55–60) μm and weakly depends on the method of nitriding, temperature (in the range of 793–873 K), and duration (3–5 hours) of the process. A nitriding regime has been revealed that makes it possible to form a surface layer with a microhardness of 13.7 GPa (ionic heating mode) and 10.8 GPa (elion heating mode). It has been revealed that the high strength and tribological properties of nitrided steel are due to the formation of a nanocrystalline structure in the surface layer, the main phases of which are iron nitrides Fe4N and chromium nitrides CrN. It is shown that heating the samples to the nitriding temperature in the aelion mode, which uses the electron and ion components of the plasma, leads to a significantly lower level of material roughness compared to the samples heated during nitriding by the ion component of the plasma.
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Structure, network protocols of the internet of things for quality production control
Статья научная
The subject of research is the model and structure of the Internet of things (IoT) network for product quality control in industry and agriculture. The purpose of the article is to analyze communication protocols and structures of IoT networks. The method of analysis and structural design of IoT networks is applied. The field of application is automation of monitoring products of enterprises of the aerospace industry. The article provides an overview and analysis of existing IoT technology; it considers the protocols and composition of IoT networks, and provides variations in the structures of building such networks. 4 levels of IoT architecture are described, as well as the communication protocols are used. The directions of building the Internet of things network for product quality control are defined. A multi-agent model of such system is presented, for the implementation of which the structure of the IoT network is given. The structure of a multi-agent system (MAS) for monitoring product quality in industry and agriculture includes many agents, such as product quality agents, communication agents, database agents, agents for analyzing information received from sensor agents, and decision-making agents. This MAS implements functions to ensure the required class of product quality and it is based on building a local network of the Internet of things. The research proposes an algorithm for processing information in such an IoT network. Analyzers (sensors) product qualities will be periodically polled and their values will be recorded in the server database. The decision-making subsystem sends data on product quality compliance to the enterprise administrator on a mobile device. The server structure is implemented using cloud IoT platforms, for which a brief overview is provided. The one IoT network implementation is developed using LTE NBIoT technology. This approach can be used in the aerospace industry for product quality control within automation 4.0.
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Статья научная
This paper discusses and estimates the effect of some design parameters on the value of axial thrust appearing during functioning of the core component of a spacecraft’s (SC) thermal control subsystem – electric pump unit (EPU). The major causes of axial forces in centrifugal pumps of in-line arrangement are described and analysed. Design parameters having an effect of axial thrust value are: impeller position relatively to EPU diffuser (position was chosen based on dimension chain calculation), presence and size of discharging holes in the impeller, number and shape of impeller vanes (numbers of 14 & 16 were considered). EPU impellers with different number and shape of vanes were designed and manufactured. A series of experiments was carried out in order to research the effects of all aforementioned parameters: measurements of head vs flow curves and axial thrust values at given flow values. Each parameter’s contribution in the value of axial thrust appearing during EPU functioning is evaluated. Vibration measurements were obtained and analysed for electric motor DBE 63-25-6.3 fitted with different impellers. In this study, a DLP additive process was used for impellers manufacturing, which significantly sped up the tests. Obtained results will extend knowledge of processes taking place in EPU impellers, enable choice of the aforementioned parameters at design phase so to minimise axial thrust appearing during functioning of a centrifugal EPU of a spacecraft’s thermal control subsystem. Outcomes of this study are capable of improving SC reliability at all phases of its life because EPU axial thrust causes its premature loss of operability.
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Study of structural properties of bismuth pyrostannate by Raman and IR spectroscopy
Статья научная
Chromium-substituted bismuth pyrostannates with a pyrochlore structure were synthesized by the solid-phase reaction method. The X-ray structural analysis performed at room temperature showed that the samples Bi2(Sn1-xCrx)2O7, x = 0; 0.05, 0.1 are single-phase and belong to the Pc monoclinic structure. Polymorphic transformations of the synthesized samples were studied by Raman and IR spectroscopy. IR spectra were obtained at the temperature range 110–525 K and frequencies 350–1100 cm–1. Raman spectra were measured at room temperature at frequencies of 100–3000 cm–1. Heterovalent substitution of Sn4+ for Cr3+ modifies the spectra of pure Bi2Sn2O7. The crystal structure of Bi2Sn2O7 consists of two oxygen sublattices: SnO6 and Bi2O'. Chromium ions substituted tin ions in the SnO6 oxygen octahedra, distorting the local structure in the vicinity of bismuth ions. Phonon modes are softening in the vicinity of phase transitions. А shift of the phase boundaries of polymorphic transitions is observed for Bi2(Sn1-хCrх)2O7, x = 0.05, 0.1. The frequencies of stretching vibration modes were determined from IR and Raman spectra. The substitution of chromium for tin ions resulted in the appearance of two new modes at frequencies of 581 and 822 cm–1 in the Raman spectra. The absence of an inversion center in the crystal structure of Bi2(Sn1-xCrx)2O7 is confirmed by Raman spectroscopy. IR spectra of chromium-substituted samples consist of complex lines, which decompose into 2 and 3 Lorentzian lines. The softening and broadening of optical absorption modes are associated with the electronic contribution. Impurity states of electrons form polarons.
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Study of the influence of alphanizing on the structure and properties of the alloy BT6
Статья научная
The paper considers the influence of two technologies of alphanizing (oxidation) on the structure and properties of the deformable titanium alloy BT6, which is used, in particular, in the aviation and space industries. The application of oxide coating by methods of chemical-thermal treatment (CTO) allows to compensate for the main drawback of the alloy – low wear resistance of the surface. The initial set of properties increases. The objects of research are titanium alloy BT6 and its oxide coatings. Two samples of the part with oxide coatings obtained by different technologies were compared. The first technology is alphanizing in finegrained graphite, the second one is alphanizing in a vacuum. The aim of the work is to find out the influence of two technologies of alphanizing on the structure and properties of the BT6 alloy. Alphanizing was carried out: 1) in fine-grained graphite at a temperature of 800 ± 10 ° C with exposure for 8 hours; 2) in an electric furnace at a temperature of 760–780 ° C in a vacuum of 10-1 – 10-3 mm Hg. for 1.5–2 hours. A study of the microstructure (light and electron microscopy) was performed. We used a microscope type Carl Zeiss Axio Observer A1m using a digital camera, adapter devices for converting an optical signal, a computer. Statistical processing was carried out according to the SIAMS700 program. Electron microscopic studies were performed using a scanning electron microscope (SEM) EVO 50 with an energy-dispersive microanalyzer INCA Energ 350. X-ray phase analysis was carried out using an X-ray diffractometer Shimadzu XRD7000, Japan (CuKa radiation, monochromator), in the following mode: range from 5 to 70 ° on a scale of 2θ, increments of 0.03°, scanning speed of 1.5 ° / min. Powders obtained from two types of coatings were investigated. The microhardness of the samples was measured on the DM8 microhardometer according to GOST 9450–76. The wear resistance of the alloy was assessed at a special laboratory installation. The phase composition and structure of the BT6 alloy after alphanizing were clarified. In the diffusion layer, the following points were detected: after alphanizing in graphite – TiO2 phases; Ti3O; TiN. After carbonation in vacuum – TiO2; Ti6O11. In the alphad layer, after processing in graphite, grains of α – solid solution, intermetallics Ti–Al-V, Ti–V and Ti–Al were detected; the alphanized layer contains more titanium after treatment in vacuum, and areas with 100% (at.) titanium have also been identified; the region of solid solution (α) and the intermetallics Ti–Al-V, Ti–V and Ti–Al are visible. The thickness of the oxidized layer is on average 103.6 μm (graphite), and in a vacuum – 66.8 μm. The average grain size in the layer is 17.2 μm (graphite); 6.0 μm (vacuum). It has been established that chemical-thermal treatment (alphanizing) contributes to a significant increase in microhardness in the diffusion layer. The hardness of HV580 (vacuum) and HV724 (graphite) was obtained on the surface. Alphanizing in graphite and in vacuum ensures the wear resistance of the product, but the best result is obtained after alphanizing in a vacuum. Both technologies improve the properties, but it is more profitable to carry out alphanizing in a vacuum, since in this case the process is carried out within 2 hours instead of 8 hours in graphite. Alphanizing (oxidation) provides wear resistance of the BT6 alloy, which contributes to the reliable operation of the product during operation.
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Study of the influence of hybrid filler on the strain sensitivity of a nanocomposite material
Статья научная
The reflector of spacecraft is in operation in the unfolded and folded position, thus an urgent task is to develop strain gauges that determine the position of the reflector. The paper presents a study of the influence of hybrid filler on the value of the strain resistance coefficient of a flexible strain-resistive element made of a nanocomposite material and describes the technological process of its manufacture using the vacuum infusion method. As hybrid filler, a composition containing an electrically conductive component (carbon nanotubes) and a solid component (silicon carbide), which promotes uniform distribution of the filler in the polymer matrix, were used. Using a rotational rheometer, the content of the carbon nanotubes (CNTs), at which the limiting level of viscosity for impregnation of glass fiber with a binder is achieved, was determined. The distribution features of the filler in the nanocomposite material were studied using a scanning electron microscope at the Krasnoyarsk Regional Centre for Collective Use of the Federal Research Centre KSC SB RAS. In the course of the work, the influence of the content of hybrid filler on the strain-resistive properties of the nanocomposite material was determined. The maximum values of the strain resistance coefficient were observed at the initial stage of the study (0.05 % tension): at 0.1 mm tension at a total length of 200 mm for the samples of a nanocomposite material with SiC hybrid filler of 1, 5 and 10 % and is 38, 40 and 40. The strain resistance coefficient of the nanocomposite material samples containing 1, 5 and 10 % SiC hybrid filler at maximum tensile (1 %) is approximately 19, 21 and 22 respectively.
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Study of the payload extraction trajectory heavy class carrier rocket
Статья научная
As the weight and complexity of the payload that needs to be launched into orbit increases, the relevance of rational trajectory selection to ensure maximum efficiency and minimum costs for delivering the payload to a given orbit increases. Rational choice of the trajectory of a heavy-class launch vehicle has a number of important practical applications. Firstly, it allows you to increase the payload capacity of the launch vehicle and reduce the cost of delivering payload to the target orbit. This is especially important in the context of the development of the space industry, when more and more companies and organizations are showing interest in launching their own satellites and other spacecraft in conditions of fierce economic competition. Choosing a rational trajectory for launching a payload into orbit will significantly reduce the cost of launches and make them available to a wider range of potential customers. Secondly, the choice of launch vehicle trajectory parameters is important for ensuring safety and minimizing risks during spacecraft launches. Thanks to the rational choice of trajectory, it is possible to reduce adverse impacts on the environment and eliminate the possibility of emergency situations associated with loss of control over the flight of the launch vehicle. Rational selection of launch vehicle trajectory parameters is a complex task that requires comprehensive research and consideration of various factors, such as aerodynamic parameters of the atmosphere, mass and characteristics of the payload (spacecraft), engine operating parameters, characteristics of the target orbit, features of the launch of the launch vehicle and many other factors. A more thorough and systematic study of the influence of these parameters will significantly improve the efficiency and reliability of launching spacecraft into orbit. Thus, the choice of rational parameters for the launch vehicle trajectory is a relevant and important topic for scientific research. Increasing the rocket's payload capacity, reducing the cost of delivering a spacecraft to a given orbit, and ensuring launch safety are tasks that depend on the chosen shape and parameters of the rocket's trajectory. Such research has important practical significance and can become the basis for the development of new technologies and methods in the space industry. The purpose of the study is to study and select rational parameters for the trajectory of a heavy-class launch vehicle when launching a payload. The main task is to determine the flight path parameters that will allow achieving maximum efficiency and accuracy in delivering the payload to a given orbit. To achieve the goal of the study, the analysis of various factors influencing the launch parameters of the spacecraft is required, such as structural and aerodynamic characteristics of the rocket, the influence of aerodynamic factors and the Earth’s gravitational field on the flight path. Taking these factors into account, numerical calculations were carried out on the basis of a system of differential equations of motion using a computer program created in the MAPLE software package. Based on the calculations, modeling of the shape and parameters of the launch vehicle flight path was carried out. Research results. During the study, the rational parameters of the trajectory of a heavy-class launch vehicle were selected. The calculations were carried out using numerical modeling of the parameters of payload launch trajectories, and the analysis of the resulting trajectories was carried out. Minimizing the rocket's flight time was identified as the main criterion for the rational choice of a trajectory, which allows increasing launch efficiency and saving energy resources. An increase in payload mass and minimization of fuel consumption were adopted as additional criteria. Conclusion. The procedure for choosing rational parameters for the trajectory of a heavy-class launch vehicle proposed in this work will improve the delivery accuracy and reliability of spacecraft launches at the stage of ballistic analysis when designing rockets. The results of the study have practical significance for the development of future heavy-lift launch vehicle missions and improving the efficiency of space launches.
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Статья научная
Due to the constant tightening of flight safety requirements in the country and abroad, with the constant growth of air traffic, more and more requirements are imposed on the reliability, non-failure operation of air navigation systems and methods for updating their air navigation databases. Besides, there arises the problem of the relevance of the databases used in accordance with the AIRAC cycle, since the risk of emer-gency situations or disasters increases in the case of using non-updated aeronautical information in the flight management system (FMS), flight management computer system (FMCS), satellite navigation system (SNS), ground proximity warning system (GPWS). The paper proposes to consider the issues of improving aircraft navigation systems and updating databases using FMS-type computing systems. Russian aircraft use FMCS-95-1V, onboard ground proximity early warning systems (GPWS) and onboard satellite naviga-tion systems operating with an orbital satellite constellation (GPS, Glonass). All of them are equipped with aeronautical databases, which, in accordance with the AIRAC cycle, are updated on the ground by engi-neering and technical personnel every 28 days. The frequency of updating depends on the receipt of chang-es in navigation data for the operation of these systems. The paper considers the issues of operational characteristics analysis, methods of data transmission to onboard aircraft systems, development of an aer-onautical data transmission system, development of a remote transmission control system, as well as the development of data transmission algorithms, theoretical and experimental justification of the choice of a transmission system model. The use of the considered complex leads to a qualitatively new level of efficien-cy, reliability of updating air navigation databases in the FMS, SNS, GPWS, FMCS, which will affect the increase in flight safety, as well as the regularity of flights in the absence of aircraft downtime according to the criterion of operational updating databases under the AIRAC cycle.
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Studying dynamics and classification of attacks to corporate network web services
Статья научная
The article presents a study of the dynamics of attacks onto the web services using the classification of cyber threats by types due to the example of the corporate network of the Krasnoyarsk Scientific Center of the Siberian Branch of the Russian Academy of Sciences. The analysis is carried out on the basis of web services logs and it allows to solve urgent problems of ensuring the integrated security of web services, including identifying both existing and potential cybersecurity threats. The article demonstrates a review of the main approaches to the processing and analyzing logs. The authors describe the type and composition of data sources and provide a list of the software used. A feature of the study is a long observation period. The structure of the processing system is proposed and software tools for attack analysis and classification are implemented. The research shows that the use of classified samples allows to detect periodicity and reveal trends of certain types of attacks. Unclassified attacks have similar distribution parameters for different years, while in the case of classification, the distribution parameters have changed significantly, which makes it possible to track risks in automated intrusion prevention systems. A correlation matrix by type of attack is constructed. The analysis shows that most attack types have weak correlation, with the exception of the attacks “command injection”, “directory browsing”, “Java code injection”, which can be aggregated. The authors propose a heuristic method of risk comparison based on cyber threat classification. The method uses statistical parameters of sample distributions and permits to deal with different time intervals. The paper georeferences the IP addresses from which the attacks are carried out, builds attack profiles for different countries, and provides a list of countries with a stable attack profile. The conclusion indicates the features of the proposed method and outlines the prospects for its use in other areas.
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Studying static stability of a model rocket
Статья научная
Relevance. When designing flying models of rockets, one of the difficult tasks is to ensure the static stability of the rocket in flight along a given trajectory. Static stability refers to the ability of a model to return to an equilibrium position disturbed by external forces (wind, model asymmetry, etc.). In this case, the model must be stabilized in terms of the angle between the longitudinal axis of the model and the direction of flight (velocity vector), that is to maintain a zero angle of attack. The condition for ensuring the static stability of the rocket model is the location of its center of gravity ahead of the center of pressure. In this case, when the angle of attack is different from zero, the aerodynamic forces will create a stabilizing moment, which will return the model to a zero angle of attack. The purpose of the study is to develop and compare methods for determining the position of the center of pressure of a rocket and determining its static stability. The research considers a simplified method, an analytical calculation, a graphical method, and various practical approaches that can be used in rocket modeling. As research methods, an analytical approach, a graphical method and finite element modeling in the SolidWorks Flow Simulation program were used. In addition, a number of approximate calculation methods were considered. The study analyzes the capabilities of the considered methods for determining the static stability of a model rocket and the error of their application. To confirm the results of the calculation, a computer experiment was carried out in the form of blowing a finite element model of a rocket using the SolidWorks Flow Simulation program. The results of computer simulation confirmed the reliability of the proposed methods for determining the static stability of a model rocket. Research results. Simplified methods for determining the static stability of a rocket are the simplest and most reliable when designing model rockets. It is advisable to use it for launching demonstration rockets with an allowable misalignment error of 15% or more. Analytical methods are useful for designing sports models of rockets with high flight requirements, for example, for international competitions. Conclusion. The proposed method for ensuring the static stability of a model rocket makes it possible to simplify the design process of both demonstration and sports models of rockets for reliable demonstration launches.
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Studying the factor of ice of icing field loss from fresh water in the millimeter range
Статья научная
This research aimed at measuring the microwave radiation attenuation in an artificially formed icing field on the ice covering a freshwater lake within the millimeter range. The measurements were made using microwave radiometry at frequencies of 22, 34, 90, and 125 GHz with a cyclic change in the ambient temperature within the range from –19 to –31 C. A special technique is used, which makes it possible to determine the microwave radiation attenuation in it from the increments of radio brightness temperature between ice cover and without icing field. In the proposed method, the loss factor is found under the condition that attenuation in ice is determined by electromagnetic losses in the medium. The measurements were carried out on the ice cover of a fresh lake with a water salinity of about 100 mg/l. As a result of the study, it was found that the formation of radiation by ice is strongly influenced by scattering on the medium inhomogeneities. This conclusion was made based on comparing the calculations of the expected ice loss factor of icing field and the data obtained from measurements by the method used. The greatest difference in the loss factor (several tens of times) was found at frequencies of 90 and 125 GHz. It has been suggested that radiation scattering occurs on crystalline hydrates of salts and can be caused by increased electrical conductivity of thin water films on the crystal surface. This feature can arise, as it has been recently established, during the formation of ice 0 crystals in the medium. This ice is formed from deeply supercooled water at temperatures below –23 C. The observed effect is of interest for developing radar measurements of fresh natural ice at low temperatures and low concentrations in salts (about 100 mg/kg). Such ice can form from slightly salty water with a salt content of up to several grams per liter or when water with a salinity of ~ 100 mg/l freezes in a confined space. The results obtained are of interest for microwave aerospace determination of the ice areas with its structural disturbances, through which the water of the reservoir can penetrate to the ice surface with subsequent freezing. At the same time, radars can be effective at icing field temperatures below –20 °C, when liquid inclusions almost completely freeze out. For the temperature range above the eutectic point, where liquid inclusions appear, passive radiometric measurements can be effective.
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Synthesis and study by electron microsco-py of inverse opals from zirconium oxide
Статья научная
Zirconia has a high dielectric constant and high thermal stability. There are many methods for the syn-thesis of nanocrystalline materials from zirconium dioxide. These include hydrothermal synthesis, gas-phase chemical reactions, cryochemical synthesis, plasma chemistry methods - these methods are expen-sive and complex. In this work, we propose a relatively simple method for controlling the growth of zirco-nia nanocrystals by synthesis in polymer templates (template synthesis of inverse opals). Inverse opals have unique physical and chemical properties, so they can be widely used in optics, optoelectronics, biological research, catalysis, functional ceramics, which is also relevant in the rocket and space industry. As a start-ing material, we used a water-alcohol solution of zirconium oxychloride, with which we impregnated tem-plates of monodisperse submicron spherical particles of polymethyl methacrylate. After impregnation of these templates, the solution solidified in a limited pore space of 20–40 nm. After that, we annealed the result-ing templates to remove the polymer matrix. In this case, structures consisting of zirconium dioxide nano-crystals were formed. Using the methods of scanning and transmission electron microscopy, we assessed the morphology of the obtained materials, and showed that under conditions of limited diffusion, zirconia forms crystals with a size of 10–30 nm. Also, depending on the calcination temperature, materials with dif-ferent crystalline modifications are obtained. As a result, we have shown that water-alcoholic solutions of zirconium oxychloride are a convenient means for obtaining nanocrystalline materials, including inverse opals from zirconium dioxide, by template synthesis.
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System analysis of dynamic problems of anisotropic plasticity theory
Статья научная
Dynamic problems are the least studied area of plasticity theory. These problems arise in various fields of engineering and science, but the complexity of the original differential equations do not allow to develop accurate solutions and correctly solve numerical boundary value problems. This is even more typical of dynamic equations of anisotropic plasticity. Anisotropy reduces the group of symmetries allowed by the equations, and therefore narrows the number of invariant solutions. One-dimensional dynamic plasticity problems are well studied, but two-dimensional problems cause insurmountable mathematical difficulties due to the nonlinearity of the basic equations, even in the isotropic case. The study of the symmetries of the plasticity equations allowed us to find some exact solutions. The most known solution was found by B. D. Annin, who described the unsteady compression of a plastic layer made of isotropic material by rigid plates. Annin's solution is linear in two spatial variables, however, it includes arbitrary functions of time. Symmetries are also used in the proposed work. Point symmetries are first calculated for dynamic plasticity equations in the anisotropic case and are presented in the paper. The Lie algebra generated by the found symmetries appeared to be infinite-dimensional. This circumstance made it possible to apply the method of constructing new classes of nonstationary solutions. Symmetry can transform the exact solution of stationary dynamic equations in non-stationary solutions. The framed solutions include arbitrary functions and arbitrary constants. The outline of the article is as follows: according to the method of Lie group of point symmetries allowed by the equations of anisotropic plasticity is calculated. Two classes of new stationary invariant solutions are framed. These stationary solutions, by means of transformations generated by point symmetries, are transformed into new non-stationary solutions. In conclusion, a new selfsimilar solution of unsteady equations of anisotropic plasticity is framed; Annin's solution is generalized for the anisotropic case. The framed solutions can be used to describe the compression of plastic material between rigid plates, as well as to test programs, designed to solve anisotropic plastic problems.
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Technical system simulation with Python
Статья научная
The results of the development of a scheduler for the joint execution of simulation models of multicomponent systems are presented. The software is implemented in Python, which allows integration with numerous libraries for control and data analysis. Data exchange is carried out via UDP packets that support different programming languages. This simplifies the implementation of hardware-in-the-loop technology, improving the development of control systems. An example of using the scheduler is demon-strated on the model of the attitude determination and condtrol system of a CubeSat spacecraft with a magnetic orientation system. The B-Dot algorithm and the results of simulating the transient process are provided. The source code is available under the BSD license on GitFlic, and the documentation is available on ReadTheDocs.
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