68-й выпуск электронного журнала «Труды МАИ» является тематическим и содержит 28 научных статей, подготовленных на основе докладов, поставленных на IV Всероссийском межотраслевом молодежном научно-техническом форуме «Молодежь и будущее авиации и космонавтики-2012» и признанных экспертными группами и Организационным комитетом победителями, как соответствующими общепризнанным критериям высокого научного уровня. Заседания IV Всероссийского межотраслевого молодежного научно-технического форума «Молодежь и будущее авиации и космонавтики» состоялись 30 октября 2012 года во Всероссийском выставочном центре. В работе форума приняли участие более 800 молодых ученых, специалистов, аспирантов и студентов – представителей более ста организаций Москвы, Московской области и регионов России, сотрудничающих с Московским авиационным институтом по научно–техническим вопросам и в области подготовки инженерных кадров. В рамках форума по девяти направлениям (авиационная техника; двигатели и энергетические установки; системы управления, информатика и электроэнергетика; системы радиолокации, радионавигации и связи в аэрокосмической сфере; ракетная и космическая техника; робототехника, интеллектуальные системы и авиационное вооружение; математические методы в аэрокосмической сфере; материалы аэрокосмического применения; экономика и менеджмент в аэрокосмической сфере) из 187 работ, поступивших на конкурс, экспертными комиссиями было отобрано во второй тур и заслушано на форуме 93 доклада по актуальным вопросам научно-технологического развития аэрокосмической отрасли и смежных высокотехнологичных отраслей промышленности. Организационный комитет IV Всероссийского межотраслевого молодежного научно-технического форума «Молодежь и будущее авиации и космонавтики» выражает надежду, что издание данного выпуска будет полезным для дальнейшего развития в Российской Федерации высоких технологий и кадрового потенциала таких технологий.
Mathematics. Physics. Mechanics
It is the numerical investigation of the natural convection flow pattern and heat transfer rate inside rectangular box heated from below and cooled from above with insulated sidewalls. The box is inclined from horizontal to vertical position and back round the shortest side. This is the longitudinal configuration of the inclined layer for which the transversal rolls are typical.
Direct numerical simulation (DNS) of Navier-Stokes equations for incompressible fluid is applied. The numerical method is based on a second-order central difference approximation in space and on integration for time by a third-order semi-implicit Runge–Kutta method. Spatial discretization retains some important properties of the Navier–Stokes equations, including energy conservation by the nonlinear and pressure-gradient terms. The scheme is supplied with a local error estimation and time-step control algorithm.
The hysteresis with subject to changing the inclination of the box has been confirmed. Different convection interactions have been detected. It is noted that there are oscillations of flow for some angles at high Rayleigh numbers. The comparison of regime diagram for spatial and plane flow showed the discrepancy in number of rolls and the borders of their number change.
The study is limited by laminar regime for incompressible fluid for which Boussinesq approximation is right. The observable fluid was air. The Rayleigh number is varied between 103 and 105 and the angle range from 0 up to 90°.
This is the study of spatial pattern and heat transfer rate of convection interactions in the longitudinal layer defined by the aspect ratios of the box. The diagram of the interactions regime was sketched.
Keywords: Navier-Stokes equation, Boussinesq approximation, modeling, natural convection, bifurcations, hysteresis, slope layer
The purpose of the research is to enhance sensitivity of the device that measures pressure and its change rate; to increase the speed of response and decrease discrimination threshold of the system intended for measurement of pressure and its change rate.
The paper considers the most known methods of measurement of pressure change rate. The analysis shows that the existing systems used for measuring pressure change rate have certain shortcomings. The systems, which make measurements based on pressure drop, are characterized by low sensitivity and substantial time lag. Other systems, which measure pressure change rate by deriving electric signal from pressure, are characterized by low interference resistance due to existence of high-frequency noise in output signal. The paper proposes the construction principle, which expands the functionality of the known methods via application of the convectional jet converter as the main converter of signal energy kind. The output signal of such converter is the mass rate of air flow, which contains information both about pressure and its change rate. The analysis is carried out and structural layout of a version of the system intended for measurement of pressure and its change rate is substantiated. The proposed version is based on convectional jet converter and is characterized by advanced metrological performance.
The proposed concept of pressure measurement system provides comfortable conditions in airplane passenger cabin. This is attained via improved accuracy and speed of response of the process of control and adjustment of gasdynamic parameters within the airplane cabin, in particular, via maintaining the given level of air pressure and its change rate.
The main problem of expansion of operation range of systems of gasdynamic parameters monitoring consists in widening the range of their invariance to the effects of thermal agitations. Additional research is required to solve this problem.
Acquisition of measurement information is based on information redundancy of the output signal of the anemometric-sensitive element, which acts as a basic element of the system sensor. Preliminary research of the model sample of the system sensor confirmed the possibility of its application within systems, which are intended for monitoring pressure change rate in airplane passenger cabin.
The scientific research results can also be used for information support during monitoring icing parameters of filtration probes of compressors of surface gas compressor stations and other gas-hydrodynamic objects.
Keywords: systems, structure, gasdynamic parameters within the aircraft cabin, pressure, pressure change rate
Ritz polynomial calculation of short wing flutter stability is considered by the example of a rudder bar in subsonic flow. Eigen frequencies and forms of the first two oscillation tones are identified. A flutter stability boundary is determined in accordance with relative density of air.
Deformation of a short wing is representing as deformation of its middle surface in relation to the straight normal hypothesis. Ritz polynomial calculation allows to describe a deformation function in the form of coordinates polynomial series in direction of flow and wingspread. Mathematical powers of the polynom depend on boundary conditions of a short wing and number of freedom degrees, which is necessary for finding the predetermined number of oscillation tones. A short wing is modeled with the help of specific units allowing to increase the precision of output.
Calculation of flutter stability considered by the example of a rudder bar in subsonic flow has shown a good convergence with the experimental results. This fact confirms the highest precision of methodology. Simplicity of the mathematical model, quickness of data preparation and computation speed give the base for calculation efficiency of a flutter stability boundary.
Ritz polynomial calculation can be applied for flutter stability computation of both single aircraft unit and whole aircraft. If initial data is initialized exactly or if they can be corrected on the basis of results of ground frequency test, then it is possible to get calculation accuracy within 1-5% diapason.
Ritz polynomial calculation is realized as independent engineering software showing high accuracy of calculation. The important feature is application of the straight normal hypothesis. This approach is applicable for construction, which assumes realization of this hypothesis, only.
Keywords: flutter, method of polynomials, modeling of the aircraft, subsonic flow
The increasing number of various mission types, which are fulfilled by unmanned aerial vehicles (UAVs), leads to the continuous increment of the importance of human operator and his responsibility for the efficiency and safety of the system. The aim of the research is to study the work of a human operator during the control of unmanned aerial vehicle.
The paper presents the results of the development and approbation of simulation complex, which allows investigating the performance of the human operator during manual UAV control. The main specific feature of the research simulator consists in combination of the relative interface simplicity with the full simulation of the UAV dynamics. This approach allows using relatively simple software that is developed by the researchers themselves. At the same time the most important advantage is that the usage of the program is fully controlled by the researchers and can quickly change depending on the task. The considered version of the research simulator allows for implementing the following: the complete equations of UAV spatial motion; the model of the aerodynamic coefficients and algorithms of the remote control system (RCS), which was selected for the UAV modeling; standard atmosphere and wind models.
Experimental studies of the human operator during the control of dynamic systems with various structures were conducted.
The presented study provides a starting-point for further research of the performance of the human operator in dynamic systems
The paper aims at developing analytical methods for optimal design of UAV control and guidance systems, which can solve the problem of matching the dynamic characteristics of the systems with control capabilities of human operator. The solution of this problem significantly influences the performance of human operator and thus has a great impact on performance indicators of unmanned aircraft systems as a whole.
Keywords: man-in-the-loop simulation, research simulator, human operator, the activity performance, unmanned aerial vehicle
The purpose of the article are definition of applicability of active thermionic thermal protection of hypersonic flight vehicle elements at their aerodynamic heating, and also study of structure of constructive shape of hypersonic flight vehicle elements with thermionic thermal protection.
In activity it was established that heat flows of electronic cooling can reach values in 1.5MW/m2. This means that hypersonic flight vehicle can move in atmosphere in the conditions of heat flows 3MW/m2 that essentially expands operating conditions hypersonic flight vehicle on speed and altitude.
The new kind of thermal protection based on the phenomenon of thermionic emission is offered.
At movement in atmosphere with hypersonic speeds the external cover is heated up to temperatures at which at the expense of thermal energy got at aerodynamic heating hot electrons are emitted from the internal surface of external cover and then are besieged on the internal cover (anode). Further, at the expense of the received energy electrons can performuseful work under load in the onboardpower consumers. After that electrons return to the cathode and a cooling cycle is repeated again. Thus, simultaneously there is an electronic cooling and electric energy is generated.
The border of applicability of thermionic thermal protection from the heat flows, typical for functioning of thermionic thermal protection is determined. Some aspects and features of application of thermionic protection were determined.
The given research is a component of thermionic thermal protection research.
The novelty is that the phenomenon of thermionic emission is first used for thermal protection systems. The temperature of hypersonic flight vehicle elements as a result decreases and electric energy is simultaneously generated.
Keywords: thermionic emission, electronic cooling, electric energy, hypersonic vehicle, thermal protection
The paper presents the results of calculation and experimental research on increase of efficiency of high-lift devices of light transport airplane.
The purpose of the research is to estimate the efficiency of various versions of adaptive high-lift devices during landing. This is done via usage of a program, which provides numerical solution of the Navier–Stokes equations.
The result of estimation of the efficiency of adaptive high-lift devices is presented. One of the main elements of these high-lift devices is the rear rotary part of the wing, which is situated above the flap.
Four versions (angles) of double-slotted flap deflection were studied: 20 degrees (take-off configuration); 32 degrees (landing configuration) and large angles (35 degrees and 40 degrees). Also the influence of the size of the slot between the deflector and the main part of the wing on flap efficiency was investigated.
Computational research was carried out via FINE/HexaTM computational software system by NUMECA Int. (Belgium). The airplane model tests were carried out in T-102 wind tunnel in TsAGI.
Computational research revealed the specific features of viscous flow streamlining of airfoil with adaptive high-lift devices and its advantages over the “normal” high-lift devices.
Utsage of adaptive high-lift devices leads to considerable lift increase. For example, the deflection of the rear wing part onto an angle δ=5º increases the lift coefficient of model take-off configuration by 28% in comparison with the basic version. The lift coefficient increase for model landing configuration in this case would be around 11÷13 %. Deflection of the adaptive element onto an angle δ=10º increases lift coefficient by 20%.
It is possible to make the following conclusions according to the results of the conducted research: Modification of double-slotted flaps increases their efficiency. The lift performance of the high-lift devices version with adaptive single-slotted flaps is only slightly worse than that of “normal” double-slotted flaps. Other aerodynamic performance of these versions is almost identical. Thus the results of analysis and experiments allow recommending the version of high-lift devices with adaptive elements for further investigation of structure design variants.
The development of wing high-lift devices for modern airplanes remains a topical and complex problem in modern aerodynamics. Airplane take-off and landing modes become more and more complex due to increase of take-off and landing weights and speeds as well as more rigid flight safety requirements. Thus the research on development of improved concepts of high-lift devices, which can provide for necessities of the advanced created airplanes, has great practical value. The paper elaborates one of such concepts and addresses the abovementioned issues.
Keywords: light transport airplane, adaptive high-lift devices, efficiency, wind tunnel
The optimization of flight trajectories to the Moon of spacecraft with electric propulsion system is the subject of this study.
The problem of flight of spacecraft with electric propulsion system between the low-Earth and low-Lunar orbit in condition of minimal time with searching for program of optimal thrust vector control in terms of minimizing consumption of characteristic velocity is considered in this work. The main aim of this work was to develop a methodology for determination of optimal trajectory for interorbital flight between low-Earth and low-Lunar orbits with low thrust in condition of restricted problem of three bodies.
Optimal flight trajectory was determined with taking into account the gravitational fields of the Earth and the Moon (restricted problem of three-bodies) and without the division into sections. Direction of thrust vector was defined by the law obtained using the maximum principle of Pontryagin. Thrust and density impulse was assumed as constant for the total trajectory. The continuous working mode of electric propulsions has been considered. Moon ephemerides were determined according to the EPM 2008 model developed by "Institute of Applied Astronomy RAS".
Methodical software for calculation of optimal flight trajectories with low thrust between low-Earth and low-lunar orbits in condition of restricted three-body problem without dividing the trajectory on sections has been developed. The estimation of characteristic velocity consumption for flight from the Moon artificial satellite orbit to the Earth artificial satellite orbit has been received.
Results of this work can be used for effectively solution to the transportation problems connected with payloads delivery into low-lunar orbit in the case of decision about step-by-step deployment and operation of ongoing lunar base (including with astronauts) with the respect to investigation and exploration of the Moon.
Keywords: electric propulsion engine, low thrust, flight Earth - Moon
Orbit inclination correction problem of spacecraft with inertial actuators is considered, spacecraft is found on high elliptic orbit, correction is provided by using the electrojet engines under undisturbance orbit period. Main complexity of this problem is non-linear changing of angular rate and it leads to the difficulty of determination of elector jet cyclogram.
Given algorithm was developed based on equations for undisturbance orbit period and equations for inertial actuators angular momentum. Equations for orbit period were obtained from 3rd Kepler law. Equations for angular momentum of inertial actuators were obtained from angular momentum variation law. Spacecraft inertia tensor is considered as diagonal matrix.
This algorithm can be used in spacecraft software in the cases when spacecraft is found on high elliptic orbit and it uses inertial actuators for attitude control.
The present study provides a starting-point for further research and optimizing this algorithm to apply it for satellite angular momentum control while orbit correction is in progress. Body reference frame coincides with the orbital reference frame (it is similar to LVLH – local vertical local horizontal) while orbit correction is in progress.
Equations for operating engines cyclogram calculation and angular momentum estimation at the end of orbit correction were developed. This algorithm probably will be used in future satellite software to optimize orbit correction.
Keywords: high elliptic orbit, orbit correction, electrojet engines, orbit period, inertial actuators
The number of CubeSats launched every year for carrying out of technological experiments and for educational purposes is steadily increasing. The main problem is searching for inexpensive opportunities for launches of such small satellites into orbit. As a rule, they are launched in condition of piggy-back launch with the priority of main payload. The traditional method for CubeSats nanosatellites separation is a device, which uses a spring pusher, for example, the ISIPOD separation device, which is produced by the company ISIS located in Netherlands. However, if a group of CubeSats needs to be launched with the help of these devices there will be the problems caused by the impossibility of operative influence on the speed of CubeSats separation.
In order to eliminate this lack and to provide controlled deployment of CubeSats group, it is proposed to use a device, which allows to change the separation speed of each CubeSat and based on usage of electromagnetic forces. Experimental research on the magnetic-pulsed drive designed for nanosatellite separation on the example of CubeSat nanosatellite were carried out. Experimental test-bed for testing of CubeSat mass-dimensional analogue was created.
The new separation device is based on the principle of non-contact action on the object.
The main advantage of this action is the absence of damage probability on separated object during the time of removal into an orbit. Advantages also include the possibility to control the separation speed with the help of stored energy.
The positive results were obtained during testing and CubeSat mass-dimensional analogue was separated with 0.5 - 3.0 m/s velocity.
The results can be used for creation of nanosatellites separation device, allowing to quickly set up the required separation speed.
The prototype of the separation device was made and verified. The positive conclusion has been received for patent № 2011118259/11 (027041) RU, 20.06.2012 МPК В64С 1/10 “Method for the nanosatellite piggy-back launching and device for its separation.”
Keywords: the deployment device, magnetic field, inductor, nanosatellite, payload, , , separation velocity, cluster, adapter module, control unit
This work can be used at designing small-size spacecraft with electric propulsion engine. It shows one possible option of design and layout scheme of small-size spacecraft with electric propulsion engine. The opportunity of producing such spacecraft is shown.
The main results of this research are the design and system characteristics of small-size spacecraft. It was taken into account that spacecraft transfers to the Moon after packet launch.
The flight scheme consists of the following stages:
Coplanar interorbital flight from pericenter of starting high elliptical orbit (circular orbit H = 42164 km, i = 51.4°) to an intermediate circular orbit;
Transfer from an intermediate orbit to collinear libration point L1 of the Earth-Мoon system;
Transfer from L1 to target polar circle orbit of Moon satellite with altitude 100km.
As a propulsion system was chosen engine КМ-60 (power 670 Wt, thrust 36 мН, spesific impulse 1716 sec, service life 4100 hours), mounted on two-stage drive.
Mass balance spacecraft for starting orbit H = 42164 km, i = 51.4° is:
Board control - 26,4 kg;
Radio system and antenna system - 7,2 kg;
Power system – 70 kg;
Propulsion system (with working body) - 118,3 kg.;
Thermal condition system - 4,00 kg;
Cable network - 9,00 kg;
Construction - 12,00 kg;
Brackets, small parts, standards - 5,00 kg;
Reserve – 20,00 kg;
Adapter with separation system - 13,00 kg;
Total – 296,70 kg.
Time of flight to polar Moon orbit 100km-high in described work statement is near 700 days.
There are some questions that have to be solved while designing this spacecraft. Some systems have to be miniaturized and adapted for use at small-size spacecraft, for example, electric propulsion engines are rarely used at spacecraft and work systems have low standardization and used for heavy spacecraft have high mass-and-dimensional characteristics. Mainly it refers to electric power supply which power is high due to presence of electric propulsion.
However Russian astronautics has got backlog of producing high-efficiency electric power systems with small mass-and-dimensional characteristics
That’s why in producing small-sized spacecraft the main attention should be paid to electric power systems design. . It is also worth noting that for the chosen engine the guaranteed life at the moment is less than the required
The results of this work can also be used in design of spacecraft for researches of asteroids that orbiting at Earth orbit. As orbits of such asteroids have different inclination it is useful to choose orbits with inclination close to future orbits of heavy-weight Spacecrafts. It’ll give an opportunity to reduce flight time and increase mass of the payload.
Keywords: small-size spacecrafts, electric propulsion engine, design, Moon researchers, on-board equipment
Use of energy of electrostatic charges will allow to receive a new power source on the satellite of any size and to compensate decrease in term of life of solar panels.
Reports of use of energy of the electrostatic charge received on a surface of the satellite is presented. The ability to use this energy in a regular power supply system of the satellite is considered.Use of possibility of accumulation of energy of static electricity and its application for additional recharge of satellites storage batteries will allow raising their resource and energy efficiency of a power supply system
Use in a power supply system of the saved-up electrostatic charge will allow to increase energy efficiency of the satellite, but also, will promote decrease in an adverse effect on work the onboard equipment of electromagnetic fields that will lead to increase in service life of the satellite.Electrostatic charging systems will bring reduction of malfunctions at the expense of decrease harmful impacts of electrization on onboard equipment of the satellite
Wide use of miniaturized satellite demands to increase service life of such devices. Now it is very difficult. Use of energy of an electrostatic charge will provide opportunities to develop small spacecraft.
Practical application is possible on various satellites, in particular miniaturized satellite. Introduction of electrostatic charging systems will make the minimum constructive additions to the satellite, and subsequently, can become its important part.
Electrostatic energy is accumulated in regular battery satellite, by means of electrostatic charging systems intended for preservation of solar energy. Usage this solution will reduce the influence of the space factors on service life of the spacecraft.
Keywords: energy efficiency, solar battery, electric power supply system, energy of electrostatic charges, chargeable electrode, active shelf life, reliability
Increase energy-ballistic efficiency missiles of the near tactical zone.
The article describes ways to increase energy-ballistic efficiency missiles of the near tactical zone by the use of acceleration-affecting propulsion system, adaptive control elements and creating torque with threaded grooves. The advantages and disadvantages of these methods were indentified. The results of numerical experiments that reveal the enormous potential of these areas were presented.
For example, application of the acceleration-affecting propulsion system allows to increase the available overload just before hitting the target by an average of 6-8 units, and reduce the probability of missiles miss at 5-20%.
Adaptive control elements provide increase in the probability of the target destruction, as anti-aircraft and anti-tank systems of precision weapon. They have advantages over conventional aerodynamic control elements such as: the ability to control the lift force, rapid action capability to control the lift force through the use of piezoelectric elements, and work in a wide range of angles of attack.
The investigations can be concluded that using of the torque effect for supporting a slew rate of the unmanned air vehicle may be realized only with stabilizing aerodynamic surfaces installed without angle relative to a longitudinal axis of the rocket, while achieving a significant reduction of drag of the aircraft. Also, this method can be used for leveling, which eliminate manufacturing errors of stabilized block of guided missiles.
The present study is a starting-point for further research of the increase energy-ballistic efficiency of the near tactical zone missiles.
In the Russian Federation during the last two decades the development of weapons systems concentrated on the extensive area. In this regard, the development of high-precision missile system formed by the direction of improvement structural and technological parameters and energy ballistic performance aircraft. In this area, for small guided missiles is possible to improve their performance characteristics by applying acceleration and affecting propulsion system adaptive controls, as well as ways of creating torque with threaded grooves that are innovative in this area.
Keywords: acceleration-affecting propulsion, warhead, adaptive controls, rifled grooves, downwash air
Aerospace propulsion engineering
The subject of the inquiry is a problem of high-speed aircraft service life extension as one of the central problems of modern aviation. The author deals with a problem of short life time (less than 100 flight hours) of a high-speed aircraft air intake panel. A high-speed aircraft air intake panel has been analyzed with relation to fracture pattern, aircraft operation conditions, statistics of operating hours prior to fracturing.
Service life extension of a local area on a perforated screen of a high-speed aircraft air intake.
The real cause is air intake nose part torsion motion which appears as a result action stalling of boundary layer on an air-intake structure.
The common version that air intake perforated screen damage is caused by dynamic pressure in Mmax mode is shown to be baseless. The real cause is air intake nose part torsion motion which appears as a result action of boundary layer stalling on an air intake structure.
Measurements of vibration overloads and stress in an air intake nose part (place of forward panel attachment) show that significant oscillations are set up in descent (with an elevated angle of attack). Frequency tests of an air intake nose part have shown that torsion motion of an air intake nose part (f=170Hz) excites torsion motion of a front screen whereby a loading diagram of a perforated screen has been suggested in the article. For practicing perforated screen repair vibration tests have been conducted on a full-scale panel and subscale demonstrators corresponding to perforated screen parameters (material, thickness, and configuration). Fractures appeared as a result of conducted tests correspond with service fractures. Repair works have been performed by welding with specially selected additives.
Tests of overhauled samples have shown service life extension of the repaired with additives samples by 5-10 times in comparison with original samples which provides more than 2000 hours of service life for a front screen of an air intake (takeoff and landing).
Keywords: CALS, service life, acoustic loads, , air intake nose panel, statistics of operating hours
The purpose is to develop the optimal law of head extension sliding for rocket engines nozzle. To maximize the effectiveness of the sliding nozzle usage, it is proposed to develop a controlled drive for the head extension, using a stepping electric motor with high torque, set in one of the links in the hinge-lever mechanism.
Offers of the theoretical study are based on the analysis of the Russian and foreign patented design developments of rocket engine nozzles.
The analysis of existing concepts of extension, which are used before starting the engine, was carried out.
Strengths and weaknesses of structures were identified with subsequent conclusions.
Based on the findings, it is proposed to create a new drive for rocket engines sliding nozzle with head extension.
It’s possible, for example, to apply the theoretical framework for the study of the control law to reduce impact loads to nozzle of rocket engines. Described method of head extension with the controlled electric drive allows to reduce significantly the impact loads at minimal time of head extension.
The present study provides a starting-point for further research in the field of rocket engines. The application of this electric drive is also possible for sliding nozzles of liquid and solid rocket engines.
The proposed scheme can significantly reduce the impact loads on structure and keeps high-speed characteristics of extension nozzle.
Moreover, it is possible to consider the nozzle structure in which the hinge-lever mechanism for extension with electric drive is installed on the inner surface of the bell that allows to drop the entire extension system after fixing the head in the operating position, thus reducing the nozzle mass.
Keywords: nozzle, head, extension, lever, drive, loads, electric, hinge, speed
The purpose of current research work is to examine the modern mathematical methods used in the calculation of new generation thermionic space nuclear power unit.
The calculation of characteristics of space nuclear power unit is divided into a set of problems, three of which are examined in current research work. The problem of three-dimensional numerical calculation of the electrical and thermal characteristics of the electricity generating channel is solved with the help of modified software suit Comsol with numerical solver developed by the authors which makes it possible to simulate the thermionic problem in three-dimensional formulation using the experimental current-voltage characteristic of the thermionic converter. The problem of optimization of the reactor core structure is solved with the use of the simulation model to calculate the neutron-physical characteristics of the reactor and techniques of genetic algorithm to optimize the structure of the core. And the problem of optimization of the weight and size characteristics for the radiation shield is solved with the use of artificial bee colony algorithm for finding the optimal profile of the radiation shield.
Application of considered modern mathematical tools enables to solve the problem of calculating the characteristics of space nuclear power unit quickly and effectively.
Conducted research is the first step to the creation of the modern computational code for calculation of the characteristics of space nuclear power unit in solving large-scale space challenges of today.
Keywords: thermionic converter, electricity generating channel, three-dimensional numerical calculation, optimization of radiation shield, bee colony optimization, optimization of nuclear reactor, genetic algorithm
Theoretical engineering. Mechanical engineering
The purpose of research is improving the accuracy of machine tools for processing on the basis of management's executive bodies on the results of predicting the thermal displacement.
The main direction of improving the accuracy of manufacturing precision products aviation and missile technology is to improve the quality of the machine tools. At the same quality criteria are the performance, accuracy and reliability. These indicators are closely related to thermal processes taking place in machine.
The development of an automated control system of executive bodies of machine tool to compensate temperature deformation is the subject for study in this work.
During execution of field experiments the regularities of changes in the thermal characteristics of machine tool, depending on the mode of its operation were obtained.
Increasing the machining accuracy of numerical control machine tools is realized on use of original algorithm for compensation of thermal deformations based on forecast mathematical models.
This algorithm permits to provide the thermal displacements along spindle axis within the limits of 10 microns regardless to duration of technological operation performed on machine tool.
The article presents the scientific based technological solutions to increase the machining accuracy on metal-cutting machine tools that have a significant importance for domestic machine tool construction. The possible limits of precision with usage the algorithm developed for the compensation of temperature deformation are identified.
The method of predicting, allowing to form the thermal characteristics of machine tools is proposed. The control method of thermo-deformation condition of machine tool based on automated predicting thermal displacement of executive bodies is developed.
Keywords: numerical control machine tool, thermal deformation, compensation algorithm
Control and navigation systems
The subject of research in the proposed article is a set of geostationary Earth orbit (GEO) and high-elliptical orbit (HEO) satellites autonomous navigation system functioning algorithms.
The main purpose of the space vehicles under consideration is tele- and radiocommunication functioning providing. The required accuracy of satellite positioning is achieved by periodical download of navigational solution from a ground control complex. The development of autonomous navigation systems will increase reliability of space vehicle functioning and simultaneously decrease a load on the ground control complex. A concept and an architecture of the autonomous navigation system based on Global Navigation Satellite System (GNSS) receiver and optical star tracker were described in [1, 2]. Accuracy estimates of the proposed system [1, 2] were acquired with space vehicle on-board integrated navigation system functioning simulation modeling. The goal of the research is to enhance accuracy of a navigation task solution. It is intended to achieve by modifying structure, parameters and functioning algorithms of the on-board integrated navigation system. Particularly, application of satellite-to-satellite measurements and phase measurements, adding a secondary GNSS-antenna to the on-board space vehicle navigation system, primary GNSS-antenna aperture modification.
Different methods of mathematical modeling, theory of probability and statistics, optimal filtering, object-oriented programming were used. The main applied methods of navigational solution obtainment were methods of optimal Kalman filtering, including its scalar modification .
Acquired results prove effectiveness of the proposed methods and algorithms. The accuracy of acquired navigational solution increased from 0.005 to 0.001 (RMS) by eccentricity for satellites on GEO and from 0.03 to 0.003 (RMS) for satellites on HEO.
These results may be used in the development of on-board integrated astro-satellite system prototypes for space vehicles on GEO and HEO.
Keywords: navigation, integrated system, gnss navigation system, Kalman filter, GLONASS, astrosensor, geostationary orbit
The problem of measuring the composition and characteristics of the Earths' atmosphere is a priority for a number of science and human activities. Domestic equipment able to conduct such measurements does not currently exist. Foreign scientific equipment usage and data is not enough to solve the problem of monitoring gas composition of the atmosphere, even on Russian territory.
To solve these problems, a special scientific device is introduced: a spectrometer for atmospheric gas composition SA-MP (for UV, visible and NIR range). High resolution capability of SA-MP is enough to find traces of gas components in the atmosphere at pixel level, and a wide spectral range will define the characteristics of aerosols and clouds.
In oder to get the resulting data in SA-MP, it is proposed to process the spectral density of a light beam luminance with DOAS method (developed IUP in Bremen).
DOAS is a method used to determine the concentrations and total amounts of atmospheric trace gases from remote sensor measurements. The light traveling through the atmosphere is partly absorbed by trace gas components along the way according to BougerLambert-Beer’s law of absorption.
A list of possible problems with the DOAS method usage is described, and computational methods of removing approximation are discussed in the article. Methods for processing information from specific spectral ranges SA-MP (part of the DOAS method) are also provided.
The positive and negative aspects of DOAS method are identified and a final conclusion on the applicability of the DOAS method in spectrometer SA-MP is reached.
Keywords: method DOAS, Beer-Lambert-Bouguer law, Ring Effect, Fraunhofer lines
Radio engineering. Electronics
This work is devoted to consideration of engineering issues of designing up-to-date wind-power stations. The aim of the paper is development of a design procedure for inverted construction of synchronous generators with permanent magnets (PM) for wind-power stations and small-scale hydro power engineering.
Determination of the main parameters of generators on the base of calculation of two-dimensional magnetic field in active zone of a generator is the theme of this article.
Calculation of the stationary two-dimensional magnetic fields of a synchronous generator is based on the analytical solution of the Poisson equation in various areas of the active zone of the electrical machine with PM.
Based on the analytical solutions the expressions for determination of the main parameters of a generator with PM have been obtained. It was showed that for greater number of ports magnetic field is mainly concentrated in the air gap and rapidly decreases outside of it.
New analytical expressions for estimating rational parameters of wind-energy generators were obtained. Using the presented approach the parameters of synchronous generator with output power of 10 MW were calculated.
The article provides a starting-point for further research in the field of synchronous generators with PM design for wind-power stations and small-scale hydro power engineering.
Keywords: two dimensional magnetic field, analytical method, inverted design of synchronous generator with permanent magnets, wind energy, hydro energy
Radio engineering. Electronics. Telecommunication systems
This paper introduces a neural network based technique for the identification of complex targets in ultra-wideband radar systems. This technique is based on the known multi-scatterer complex-valued model for representing two-dimension radar images synthesized by common ultra-wideband radar systems. The neural networks are built via structure diagrams representing the whole net implementing the desired transformation as a set of interacting adaptive elements, each of them in turn implements the partially transfer functions of bidirectional (forward and backward propagation) data signal processing. The class of radial basis feed-forward artificial neural networks learned by error back-propagation supervised methods is chosen due to the ability of such networks to highlight the local feature of the presented data. It was shown that a stable approximation result could be achieved if the number of elements in hidden layer of the networks corresponds to the number of scatterers necessary for the accurate fitting of artificial targets. The simulation showed that the importances of scatterer parameters are different, thus the estimation of center positions of scatterers can be carried out more accurately than their widths. The accuracy of the scatterer parameters estimation depends on the distance between a chosen scatterer and others and signal to noise ratio. The simulation results reveal the high sensitivity of the accuracy to the level of noise while scatterers are placed closely in the radar image. The proposed neural processing method is a relatively new but promising approach for the problem to be solved. The main benefits and drawbacks of this methods are examined in the conclusion as well as comparison with another system identification technique traditionally used for the considered problem.
Keywords: , ultra-wideband radar, multi-scatterer model, artificial neural network, radial basis functions, system identification, ultra-wideband systems, mathematical model simulation
Due to upgrading target characteristics of S/C of different missions the necessity of developing advanced on-board antenna systems appears. These antennae include multipath switched antenna systems. Such systems change beam position of gain pattern without collimation in channels but by switching multidirectional emitters. The article reviews two X-range antenna systems with 7 and 16 radiating elements. This systems have low mass-dimensional parameters, scan by multiplexing emitters and without moving parts in semi-sphere of angles. Multiplexing systems works successfully with air communication systems that confirms the necessity of their studying and integration on S/C. Multiplexing antenna systems consist of emitters, switching system and UHF channel. To provide communication in set angle sector emitters are specifically oriented. As emitters for this antennae are chosen microstrip radiator. In comparison with other types of emitters (ex. horns) this one has smaller dimensions, are easy to combine to each other and sometimes are easier to allow isolation from neighbor antenna systems.
The Input data for one Multiplexing system were:
- amplification factor not less than 5 dB;
-antenna must work in semi-sphere of angles;
-signal power not less than 10 W;
-Working frequency band 8,1-8,5 GHz (right elliptical polarization).
An emmiter with waveguide powering has been designed as emmiter for the antenna.
It allows to minimize the number of dielectric materials in the design of emmiter.
On the amplification level of 5 dB the emmiter has the width of antenna directivity diagram of about 75 degrees, V.S.W.R. ≤ 1,1 , S1 parametr ≥ of 0.7.
A form of regular truncated pyramid approaches for these antenna systems.
AS should consist of seven emmiters situated on the faces of regular truncated pyramid for operation in semisphere of angles with amplification of 5dB (there are 6 emmiters located on the side faces and an emmiter on the upper face.
AS consisting of 16 emitters will have a form of a half of icosahedrons which has emmiters on the faces. In this case, AS in semisphere of angles will have amplification of 8dB. But in this case it should consist of two types (because the faces of icosahedron are hexagons and pentagons). Therefore increase of antenna gain will complicate the AS and increase its mass-dimensional specifications.
According to this work it is possible and actual to construct multiplexing antenna systems for application on spacecraft. Multiplexing antenna systems can be used in transmissing lines of spacecraft that change the orientation in a wide range. Multiplexing equipment of such spacecraft requires use of nonmechanical retargerting devices.
Using of the described multiplexing antenna systems consisted of seven emmiters on low-orbit spacecraft increases the informativity of radio link to 200 Mbit/sec and higher.
Keywords: gain pattern, multiplexing equipment, multiplexing antenna systems, spacecraft, gain ratio, radiating element, ground station, phased antenna array, target data
The purpose for this research was to find the main regularities of direct scattering problem solutions applying to elongated objects. Since the analytical solution of direct scattering problem exists only for objects with simple geometry, the numerical methods are required for scattered field calculation. In this research, space-time samples of scattered field were calculated using finite differences time domain method (FDTD) because of its possibility to cover wide frequency ranges with a single simulation. Compared to other methods, FDTD is simple and can be performed by any personal computer, since it does not require great computational resources. In this research, the objects were considered as ideally conducting and elongated one and only parallel polarization, where an electric field vector is parallel to the cylinder axis, was studied. It allowed using 2D models and calculating only 3 of total 6 vector field components, which reduces the numerical solution. The analysis of the obtained results shows that the main diffraction lobe direction and the direction of the incident plane wave usually are the same. The growth of object electric radius causes the growth of side lobe number. It also causes narrowing of the main lobe as well as radar cross-section growth. Plane wave incidence on square and triangular cylinders raises the side lobe level in specified directions. If the plane wave incidence direction is normal to the triangular (or square) cylinder's side, the back reflection level is only 1-2 dB less than main lobe level. Otherwise, when the wave is incident on the edge of the object, the back reflection is nearly unnoticeable. These results may be used for geometry and electromagnetic parameters retrieval in the inverse problem solution which is common in ground penetrating radar and the similar applications.
Keywords: scattering, diffraction, space-time signal, FDTD method, numerical simulation, radar cross-section
In the article, a new design of the TEM horn antenna is proposed and studied. The effective design of the circle array by these new elements is considered and studied theoretically in ultra-wide frequency band. The author discloses advantages and disadvantages of using TEM horn antennas as an element of a circle array.
Proposed new design of the TEM horn lens antenna is under consideration whereas the horn lens is studied as an element of a circle array in the ultra-wide frequency band. Antenna’s matching and radiation characteristics are calculated by the numerical simulating carried out with the method of the finite elements. Different geometries of the lens and different methods of the excitation of the TEM horn are considered.
The paper reveals the simulation results for the circle array of the proposed TEM horn lens antennas. One can notice a good matching characteristic of the model and very small interference between different elements of the circle array. On the other hand the width of the radiation pattern of the TEM horn lens antenna is very small which can be a disadvantage when one uses the TEM horn lens antenna as an element of a circle array.
The paper provides engineers and scientists involved in ultra-wide band antennas and ultra-wide band radio monitoring with the obtained results for their future research.
Keywords: circle antenna array, UWB antenna array, UWB antenna, lens antenna, horn antenna
Some problems dealt with infrared and radar perceptibility of different objects are discussed in this paper. Currently used methods of the ambient medium modification for the perceptibility attenuation had been analyzed and a number of their defects had been revealed. Thus, such methods cannot provide the required defense for a long time, that leads to additional financial expenditure and pollute environment.
A fundamentally new idea based on the radiation attenuation by means of water ionized by electromagnetic waves vapor is suggested for the problem of infrared and radar perceptibility solving. Water vapor is a part of the environment and omnipresent, but has faint absorbing properties in infrared and radar ranges. One needs to find a way to impart the required absorbing properties to the water vapor.
A number of experiments with water vapor modified by UV radiation and penetrated by millimeter electromagnetic waves is suggested. A laboratory device consisting of glass box, UV lamp and a plate with hot water is developed and described in the present work. Different conditions are involved to prove that the modified water vapor strongly attenuate millimeter waves indeed. The derived medium can efficiently attenuate millimeter electromagnetic waves up to 2 dB/m and it has considerable (about 10…15 minutes) lifetime.
The effects under consideration can be applied for the defense of artificial objects from millimeter and centimeter range waves. In this case, the object has to contain a roentgen source on-board only.
Keywords: modified water vapor, perceptibility attenuation, electromagnetic radiation
The aim of the presented research consists in the choice of the junction type of cooling channels and headers of the active phased array’s cooling system, junction testing and operability of thin-walled tubes estimation. An analysis of the obtained results has been performed.
Deforming thin-walled metal cooling channels are an efficient solution for heat sink. The swelling by the internal pressure of the thin-walled tube secures a tight stable mechanical and thermal contact of cooling channel and cooled surface, then the heated coolant liquid flows ot through the exhaust manifold to the heat exchanger.
The main requirements to the coolant system are the tight contact of the thin-walled tube and the heat transferring surface to adjoining in the area of width about 30mm, the reliable joints securing leaks’ absence.
To minimize the thermal resistance in the contact the cooling channels should be mechanically tighten to the cooled object but the modern phased arrays do not allow place the clamping mechanism. An efficient alternative method consists in using of the coolant’s pressure to swell the thin wall pipes and provide contact of the cooled wall and the pipe. To investigate the proposed approach the stainless steel pipe 12X18H10T with wall thickness 0.25mm rolled out to the flat tube with dimensions 45x3.5x0.25mm was chosen.
On the basis of the preliminary computation it was found that the pipe sections with a gap of 0.1 mm secures the required contact area length of 30 mm at a pressure of 2 bar. The experimental results have shown that the required area length can be provided at a pressure 1.5bar.
The tests have shown that the soldered joint has sprung a leak that appears under cyclic loading of the pipe. The leak was avoided by increasing the tinning zone up to 20mm; the improved section stood for 3000 cycles.
One of the tested specimens has the soldered joint of the pipes to the collector. The small pipe’s thickness results the deformation of the pipes heated during the soldering so that the required tight contact of the pipe and the collector can’t be secured. This deformation can be avoided by using some supplementary parts so that results structure’s fragility and damaging of the soldered joints during transporting and installing of the radiator in tests device.
A laser welding was used as another joint method. The welding was carried out on the specimen similar to this used to test the soldered joints. A collector’s fragment and a small section of thin-walled tube were used as a specimen to test at pressures up to 5 bar and no leak was found.
It was shown that the cooling system with thin deformable tube can be efficient but requires more careful design including the use of other materials (e.g. 36NHTYU). It has been found that the laser welding provides the joint of the best strength. The most accessible and maintainable are the mechanical and solder ones.
The proposed cooling system can be used in the array antennas with high-density radiating elements / modules of a stationary or mobile systems.
The main disadvantage of the proposed cooling system is the probability of foreign objects into the gap between the cooled wall and the thin-walled pipe so that decreases the heat contact patch and results deformation and damage of the thin pipe. The dust protection of the antenna system must be used to avoid the mentioned defect.
Keywords: active phased-array antenna, the system cooling, thin-walled tubes
Wear-resistant coatings are an important part of modern tool materials. The coatings are applied to the most advanced tools.
Coating technology allows us to give them the characteristics needed for specific processing conditions and to ensure that the coating effectively complements the physical and mechanical properties of the substrate of hard alloys.
Optimizing the coatings architecture (change their composition and thickness), it is possible to create a universal hard alloys for different workpiece materials and operations.
Studies have found that the internal stresses and the boundary conditions in the coating lead to its significant bending.
Coating bending leads to the creation of compressive stresses.
That causes the development of a crack near the interface between the coating and the base.
Compressive stresses at the surface of the coating stop the growth of cracks originating from the interface between the coating and the base.
The cracks in the coating depend on the properties of the coating and the intermediate layer. Although crack growth can occur near the surface of the coating, internal cracks may appear, which are not fully spread to the surface of the coating.
The system of "coating- sublayer-substrate" is sensitive to the properties of its components, so it is possible to optimize the coating.
To control machining with using coated tools the complex optimization problem should be solved. It was necessary to relate the criteria describing the properties of the coating to the physical processes in the cutting zone.
Architecture of the multilayer coating for a specific machining process for different materials is selected from the developed optimization techniques. You can define the cutting conditions for maximum coated tool life.
The advantage of the technique is that it provides a selection of the most resistant coating on the tool. Harnessing the power of multi-layer wear resistant coating and machining equipment increases the number of tool regrinding, increase tool life period between regrinds, and improve the quality of the machined surface.
Keywords: solid carbide end mills, multilayer wear-resistant nanostructured coatings, coating defects, optimization
The corrosion resistance of the metal depending on operation conditions significantly effects to the operability of aluminum alloy structural elements. One of the most promising methods of protective coatings application is a microarc oxidation (MAO) due to the high wear and corrosion resistance, insulating and decorative properties of coatings. The effect of the application process’ parameters on the structure and properties of oxide coatings is not investigated adequately. The insufficient study results together with the absence of technologies and standards limits the use of MAO, so the study of the properties of MAO coatings is an important problem.
Corrosion resistance, electrical and other properties of the coatings depend on the porosity. Therefore estimation of the protective properties of the coating must consider its porosity.
Several methods for determining the porosity of the protective or protective and decorative coatings are known. The simplest and most common measurement methods are corrosive electroplating methods based on treatment with a special solution or applying the paste.
To identify the effect of process’ parameters on the porosity of the MAO coating the aluminum alloy AD33 and AMg6 specimens of thickness of 1 mm and 2.5 mm and in-plane dimensions 50x50 mm were used. Coating formation was carried out in two electrolytes, calcium silicate and aluminate, for the following modes of MAO: current density - 15 ... 60 A/dm2, the duration of oxidation - 60 min., the ratio of the cathode and anode component of the current Ik / Ia of 0.6 to 1, 2, bath temperature - 15 ... 60C.
After coating application the phase and structural composition of MAO coatings were investigated. The maximum content of solid oxide Al2O3 on the surface of the has been observed when the ratio of the anodic and cathodic current component Ia / Ik was equal to 0.6.
Since the porosity effects on the corrosion resistance of coatings the in rapid testing for corrosion resistance have been made.
To estimate the rate of corrosion both qualitative and quantitative properties were used. The change the look of the metal surface and the microstructure variation were the used to estimate the corrosion rate qualitatively.
Investigation of the corrosion resistance in laboratory was based on the accelerated corrosion tests by creating conditions of increasing environment aggressivity allowing rapid corrosion attack. Signs of corrosion were observed after 7 days of test. On the uncoated specimens the corrosion attack was observed on about 70% of the surface. On the conventional anodized specimens slight pockets of corrosion were observe and the specimens with micro-arc oxidation coatings survived the tests without any surface damage.
Thus, the investigation revealed that the protective properties of the coating are significantly depending on the technology. It was found that the coatings obtained by microplasma processing have good barrier properties (corrosion resistance) in the marine environment compared as compared with coatings of the classical anodizing.
Keywords: microarc oxdation, corrosion resistance, porosity, protective coating
Economics and management
Accordingly to the aviation experts the growth of air traffic will increase the number of the flight accidents. The development of the flight accident prevention methods is an actual task of the aviation industry. This task can be solved by developing the risk management system for flight safety in airlines.
In this paper the approach for development of the risk management system is considered based on the forecasting of flight accidents in the forthcoming flight, the identification of the most significant hazards and the development of measures for flight accidents prevention. The forecasting method includes modeling of the possible scenarios of flight accidents and their probability estimation. The models of flight accidents can be represented as «trees». The input data for the models is the following: flight date, aircraft reliability information, weather forecast and other. So it’s possible to assess the possibility of flight accident in every flight under specific conditions.
As an example, a model of one of the possible scenarios of aircraft overrun is presented in this paper. There were developed the full models of different types of flight accidents such as controlled flight into terrain, runway excursion, loss of control in flight and other types. The models describe the most typical and shortest scenarios of flight accidents that present the major threat for flight safety.
The developed method of the flight accidents’ forecasting and flight accidents models was introduced in the Automated system of flight accidents’ forecasting and prevention in Volga-Dnepr airline. After trial operation and revision of the system it can be used by other airlines.
Application of the developed method in airlines will reduce the number of flight accidents in Russian aviation.
Keywords: risk, flight safety, management, forecasting, prevention, flight accident