Vol 25, No 1 (2024)

Articles

Non-coplanar rendezvous in near-circular orbit with the use a low thrust engine

Baranov A.A., Olivio A.P.

Abstract

Presented method allows one to calculate the of maneuvers performed on several turns using a low-thrust engine. These maneuvers ensure the flight of an active spacecraft within a given area of the target space object. The flight is carried out in the vicinity of a circular orbit. Simplified mathematical models of motion are used to solve this problem. The influence of the non-centrality of the gravitational field and atmosphere is not taken into account in the calculations. The process of determining the parameters of the maneuvers is divided into several stages: in the first and third stages, the parameters of the impulse transfer and the transfer carried out by the low-thrust engine are calculated using analytical methods. In the second stage, the distribution of maneuvering between turns, ensuring a successful solution to the meeting problem, is determined by changing one variable. This method is characterized by its simplicity and high reliability in determining the parameters of maneuvers, which makes it applicable on board a spacecraft. As part of the study, an analysis of the dependence of the total characteristic velocity of solving the meeting problem on the amount of engine thrust was also carried out. The maneuver parameters can be refined using an iterative procedure to take into account the main disturbances.

RUDN Journal of Engineering Research. 2024;25(1):7-20
pages 7-20 views

Matematicheskoe modelirovanie optimal'nogo planirovaniya ekonomiki s uchetom nalogov s pomoshch'yu prikladnogo vychislitel'nogo paketa Maple

Perepelkina Y.V., Litvin O.N., Zadiranov A.N.

Abstract

We consider a particular issue of optimal economic planning based on models of intersectoral balance which taxes are additionally introduced as one of the controlling factors. The analysis of describing applications of optimal control methods in economics for various models, as well as an overview of applied software for the development of economic and mathematical models and calculations. The mathematical apparatus used in solving the problem is considered in detail, the formulation of the modeling problem and the rules for calculating the mathematical model using the applied package of numerical and symbolic modeling Maple are described. The mathematical model of the macroeconomic system optimal planning as an optimal task for speed is given, the mathematical apparatus of the optimality conditions is highlighted, the dependence of the planning results on the influence of the taxation factor is established. The degree of economy optimization at its fastest transition from one state and its dependence on certain combinations in the combination of control functions, such as total costs, capital intensity, consumption functions, the amount of taxes collected and production capacity, etc., are investigated.

RUDN Journal of Engineering Research. 2024;25(1):21-29
pages 21-29 views

Failure Analysis of a Kaplan Turbine Blade in Iraq’s Haditha Hydropower Plant

Khalid W.M., Reza Kashyzadeh K., Ghorbani S.

Abstract

Kaplan turbines are widely used in low-water-head and large-capacity hydropower plants. The design of such systems is based on long-term performance. Nevertheless, many failures are reported in the industry, which lead to economic losses for the purpose of major repairs or replacement of a part of the system. Therefore, it is very important to know the failures, their causes, and finally provide useful solutions for their prevention or early treatment. In the present article, the authors focused on the failure detection of a Kaplan turbine blade in an Iraqi hydropower plant, and then, determined the direction of their future research. Quantometric test, tensile test, compression test, microhardness test, metallographic examination and study of the damaged surface were conducted from damaged runner blade. It was revealed that the raw material for manufacturing runner blade of Kaplan turbine was 304 stainless steel by employing cold drawing or rolling process. In addition, annealing treatment has also been done. In addition, it was found that the predominant damage in the studied part was severe cavitation.

RUDN Journal of Engineering Research. 2024;25(1):30-37
pages 30-37 views

The Choice of Optimal Cutting Conditions, Taking into Account the Quality of the Machined Surface of the Part on the Roland MDX20 Milling Machine

Allenov D.G., Yakovleva N.A., Deinova K.B., Danilov D.V., Azanov M.V.

Abstract

The results of optimizing the milling process on the Roland MDX-20 machine are presented: the maximum allowable and optimal cutting conditions for parts made of foam, hard and soft modeling plastics, and hardwood are empirically established. At the first stage of the study, a complete list of types of strategies for roughing and finishing, presented in the CAM-system Modela Player 4 (MP4), was studied, as a result of which the optimal one for the intended experiment was chosen (9 virtual tests were carried out), processing time was taken as the analyzed parameter. To understand the specifics of the work on the machine under study and to check the suitability of using the processing parameters and the type of strategy, test processing of the foam was carried out. The main optimization criteria are speed, expressed as processing time, and the quality of the resulting surface. At the second stage of the study - experiment - methods for roughing horizontal surfaces of 20×20 mm models, consisting of a truncated pyramid and a hemisphere, are described on a Roland MDX-20 milling machine using MP4. As cutting tools in both studies, a Hanita 400305002 ∅6 mm cylindrical cutter was used for roughing, and a Hanita 400103002 ∅3 mm spherical cutter was used for finishing. The recommended cutting conditions have been established, which allow reducing the processing time of parts by 40-50 % without deteriorating the quality of the machined surfaces.

RUDN Journal of Engineering Research. 2024;25(1):38-51
pages 38-51 views

Ultrathin high-efficiency solar cells based on AIIIBV/Ge heterostructures for space applications

Nikiforov A.I., Pakhanov N.A., Pchelyakov O.P., Latyshev A.V.

Abstract

The analysis of the prospects for the creation of ultrathin, lightweight and highly efficient solar cells based on  AIIIBV/Ge heterostructures. Technological problems and prospects of various options are discussed. As the most promising method, it is proposed to use chemical thinning of  AIIIBV/Ge heterostructures using a temporary technological carrier. A solar cell grown on a germanium substrate with a contact grid, an antireflection coating and radiation-proof glass, but without a back metal contact, is glued face-on to a technological carrier. Next, the Ge substrate is etched to the desired thickness and a back contact is created, and the carrier is removed by heating. This technique makes it possible to thin the Ge substrate to several tens of microns and significantly increase the percentage of yield of suitable devices almost without the risk of destroying the heterostructure. Measurement of the current-voltage characteristics of a thinned solar cell showed that for the terrestrial spectrum, the values of the parameters of the thinned sample coincide with the initial values. The idling voltage is 2.67 V, the current density is 14 mA/cm2.This opens up the possibility of creating highly efficient thin and light solar cells for space batteries based on currently mass-produced heterostructures -  AIIIBV/Ge.

RUDN Journal of Engineering Research. 2024;25(1):52-56
pages 52-56 views

Optimizing MEMS-based navigation sensors for aerospace vehicles

Alizadeh A., Saltykova O.A., Novinzadeh A.B.

Abstract

This comprehensive study delves deeply into the intricate domain of optimizing Micro-electromechanical Systems (MEMS)-based navigation sensors for aerospace vehicles. It entails a meticulous examination of MEMS sensors, focusing on their role in guidance, navigation, and control, with particular emphasis on MEMS inertial sensors and crucial performance metrics. The study investigates a spectrum of techniques for sensor optimization, including strategies for enhancing fabrication and production through smart structures and mathematical modeling. Additionally, it explores methodologies and mechanisms for improving navigation sensor fabrication, along with the incorporation of optimizer techniques to manage computational complexities effectively. The key findings underscore the challenges tied to material selection and structural intricacies in optimizing these sensors for aerospace applications. Integration of sensors into integrated circuits, development of advanced mathematical models, and harmonization with artificial intelligence algorithms are vital for boosting sensor performance, while calibration and error mitigation during user deployment are essential. Furthermore, the study underscores the imperative for addressing limitations in sensor accuracy and precision through refined calibration mechanisms and error correction processes. The trajectory for future research involves advancing material selection, mathematical models, and innovative calibration techniques to comprehensively enhance sensor performance and reliability in aerospace applications.

RUDN Journal of Engineering Research. 2024;25(1):57-74
pages 57-74 views

Highly Efficient Photovoltaic Laser Power Converters

Andreev V.M., Kalyuzhnyy N.A., Malevskaya A.V., Nakhimovitch M.V., Shvarts M.Z.

Abstract

Photovoltaic conversion of laser radiation has found wide application in fiberoptic communication lines. Energy transfer via a laser beam is also relevant for remote power supply systems on Earth and in space. These systems can be used to power unmanned aerial vehicles, to transfer laser energy between spacecraft and from space solar panels to Earth. One of the main tasks in creating such systems is to ensure high efficiency of photovoltaic converters at high power (more than 100 W/cm2) of laser radiation. The article presents the results of research and development of photovoltaic converters of highpower laser radiation based on nanoheterostructures obtained by MOCVD epitaxy. The reduction of losses was achieved by embedding the “dielectric-silver” rear combined reflector into the structure. An increase in the generated voltage was achieved by shifting the volume charge region into the wide-gap layer of the p-GaAs-n-AlxGa1-xAs heterojunction. Thanks to an additional reduction in ohmic losses, efficiency values of > 60 % have been achieved at laser radiation (λ = 860 nm) powers in the range of 50-400 W/cm2.

RUDN Journal of Engineering Research. 2024;25(1):75-85
pages 75-85 views

Analysing the Feasibility of Adopting Gas Turbine Technology for Electric Power Generation in Iraq

Alaabidy W.H., Al-Rubaiawi M.S., Chertousov M.A., Frolov M.Y.

Abstract

A study was undertaken to understand the status of electric power demand, generation and supply in Iraq and the feasibility for adopting gas turbine technology for generating electric power. Based on the climatic and weather data, it was found that Iraq in general experiences a hot and dry climate with cooler nights. Apart from the coastal regions of the country, the relative humidity is generally low. This was found to be an encouraging factor for adopting cost effective evaporative cooling systems for the air entering gas turbine used for power generation (GTPG). The higher frequency dust storms in Iraq can result in operational problems, shorter life span and higher maintenance costs for GTPG, making air filtration mandatory for efficient operation of GTPG. Taking into account the district wise climatic and weather conditions, the district of Nineweh was found to be more suitable for the establishment of gas turbine plant for electric power generation (GTPEG). Among the different cooling systems available taking into to account the cost effectiveness and the simplicity in design, construction, operation and maintenance, it was found that evaporative cooling system was more suitable. Further, it was found that the effectiveness of evaporative cooling system can be enhanced by taking advantage of the low night temperature and cooling the water to be used in the evaporative cooling system. Analysing the performance of the gas turbine, it was found that adopting the cooling system will result in reducing the power loss from 6.68-46.89 % to 2.77 to 21.17 %.

RUDN Journal of Engineering Research. 2024;25(1):86-104
pages 86-104 views

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