Original Article
Telecommunication
elham sharifi; Arash Ahmadi; Mohammad Fazaelifar
Abstract
The antenna of a high throughput satellite payload should generate multiple spot beams simultaneously to provide frequency reuse by creating cellular coverage for the satellite. The phased array antenna is a proper option for this application. In geostationary orbit, the satellite field of view is limited, ...
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The antenna of a high throughput satellite payload should generate multiple spot beams simultaneously to provide frequency reuse by creating cellular coverage for the satellite. The phased array antenna is a proper option for this application. In geostationary orbit, the satellite field of view is limited, and dividing it to several tight beams poses many challenges to the antenna design. The large dimensions of the radiating aperture, high number of radiant elements, the need for dividing the array into several sub-arrays, which lead to appearance of grating lobes, and the orthogonality of the beams with tiny angular distance from each other, are the challenges of the antenna design. In this article, a multiple beam phased array antenna in Ka-band with microwave beam forming network has been synthesized and designed to meet aforementioned challenges. The sub-beam technique has been used for decreasing the array dimensions. For eliminating the grating lobes, the array has been divided into interleaved sub-arrays in two dimensions. A new beam forming network has been designed in this paper which can generate several simultaneous orthogonal beams for interleaved sub-arrays
reviewed article
Ehsan Mousivand; Sajjad Ghazanfarinia; Yaser Saffar; Masoud Khoshsima
Abstract
Satellite Constellations are the new approach to achieve the capabilities that were previously expected from large and complex satellites. This paper reviews activities and related satellite constellation of about 130 companies and research institutes in the world, with the aim of reviewing the approach ...
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Satellite Constellations are the new approach to achieve the capabilities that were previously expected from large and complex satellites. This paper reviews activities and related satellite constellation of about 130 companies and research institutes in the world, with the aim of reviewing the approach of missions carried out under the name of satellite constellation. Based on the investigations, the main missions performed by these constellations have been with the aim of providing communication services and include 27% of all missions ((Including internet of Things with a 16% and Machine to Machine Services with a 6%) Another important mission is Earth Observation (with 19%), which is carried out with the aim of continuous monitoring and beter management of the earth planet.The most favorite configuration in constellations is based on microsatellites with 42% of all configurations. In this article, by presenting the analysis and results of this studied sample, the tendency towards satellite constellations and the role of Cubesats in this category of space missions have been investigated. The aim of this reseach is to highlight the impact of theses space systems in the space industry and economy by providing Solutions based on constellations. Results discuss the Future of Constellations and Cubesats and their common effect on New Space both in Space Industry Level and Space Economy. This review may help researchers to work on similar studies with business approaches, too
Original Article
mohamad ali amirifar; alireza rajabi; nooredin ghadiri masoom; Zahra Amirsardari
Abstract
In this study, the pulse mode performance of a monopropellant hydrazine thruster has been studied. For this purpose, a laboratory sample of a monopropellant hydrazine thruster under atmospheric pressure was fabricated and tested. The catalyst of this thruster is synthesized natively. The pulse mode performance ...
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In this study, the pulse mode performance of a monopropellant hydrazine thruster has been studied. For this purpose, a laboratory sample of a monopropellant hydrazine thruster under atmospheric pressure was fabricated and tested. The catalyst of this thruster is synthesized natively. The pulse mode performance of this monopropellant hydrazine thruster has been evaluated experimentally and the results have been presented. The results of this study show that the monopropellant hydrazine thruster made with a synthesized catalyst produces reproducible impulses for pulses less than 10 milliseconds wide. The minimum impulse of this monopropellant hydrazine thruster is measured at 32 mNS. Also, the standard deviation of the impulse is less than 6% for 100 pulses. The thruster response time is also very reproducible. The results of this study showed that the centroid of the thruster changes linearly with the pulse width. However, the transient behavior of the chamber pressure is relatively slow, leading to a large centroid
Original Article
Telecommunication
Arda Afzali; Bahman Ghorbani Vaghei
Abstract
Finding the best possible scheduling to maximize observations and transfer them to the ground station as a function of satellite characteristics, orbital mechanics, attitude control system, field of view and observational objectives, is very important. The combination of the agility of the satellite ...
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Finding the best possible scheduling to maximize observations and transfer them to the ground station as a function of satellite characteristics, orbital mechanics, attitude control system, field of view and observational objectives, is very important. The combination of the agility of the satellite with regard to the ability to quick maneuver along the three axes of roll, pitch and yaw, with a suitable software can significantly improve the response rate, revisit time and satellite coverage and respond to users’ needs. In this regard, the design of a comprehensive scheduling that automatically creates an optimal operational sequence for the maximum utilization of agile Earth observation satellites during a certain period of time in order to respond to the needs and priorities of the users and to satisfy the operational limitations of the satellites. Therefore, in this article, the design of an automatic software for scheduling Earth observation satellites is presented, which after receiving observational targets from the user and assigning observation priority to each task, the ability to implement and execute observation tasks is checked by the attitude control subsystem to satisfy the attitude maneuver limit around the roll and pitch axes and orbital mechanics subsystem to satisfy the target access time window limit. Then, by using discrete event supervisory control, constraints are applied to the transfer system to add specific features and requirements to the mission. With the help of an optimal search algorithm based on the Bellman-Ford method, the optimal program sequence for the maximum use of the satellite while meeting the operational limitations of the mission is obtained automatically. Finally, a remote sensing mission is simulated to demonstrate the planned verification
Original Article
Seyed Mohammad Navid Ghoreishi; Mohammad Aminjafari; Amir Sedaghati; Ehsan Zabihian
Abstract
The structure of a satellite, during its operational life, must be tolerated all applied mechanical loads which the most important of them is vibration loads during the launch. To ensure the verification of design of the satellite structure, finite element analysis and vibration tests should be performed ...
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The structure of a satellite, during its operational life, must be tolerated all applied mechanical loads which the most important of them is vibration loads during the launch. To ensure the verification of design of the satellite structure, finite element analysis and vibration tests should be performed on the structure of satellite according to the ECSS standard. In this paper, while simultaneously examining the optimal design process for a satellite structure with an increase in the strength to mass ratio, the required finite element analyzes along with the mechanical tests of the structure of a telecommunication satellite, including random vibrations, sinusoidal vibrations, shock and quasi-static, are fully presented. The results showed that by employing the cross section design for the satellite structure, the natural frequency of the satellite in the longitudinal direction have increased appreciably, which increases the strength of the satellite in the longitudinal direction. Also, the results of the conducted tests proved that the designed structure meets the frequency requirements of the launcher while tolerate the mechanical loads during launch. The results of the tests were in good agreement with the finite element analysis, including the modal analysis, random and sine vibrations and indicate the verification of the design of the satellite structure
Original Article
Mona Zahednamazi; Alireza Toloei; Reza Ghasemi
Abstract
One of the best attitude sensors for space applications is the star sensor. This sensor determines the attitude using stars in the field of view. One of the main advantages of this sensor is attitude initialization using lost-in-space star identification algorithms. This paper presents a new lost-in-space ...
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One of the best attitude sensors for space applications is the star sensor. This sensor determines the attitude using stars in the field of view. One of the main advantages of this sensor is attitude initialization using lost-in-space star identification algorithms. This paper presents a new lost-in-space star identification algorithm based on Hausdorff distance. Using Hausdorff distance, two different identification algorithms have been proposed, and their results have been compared. The first approach is designed based on pivot star, and the second approach uses the segmentation of the celestial sphere. The performance of these two approaches has been investigated using the simulation of 200 random directions of the star sensor in different magnitudes. The results show the approach of the pivot star has a better performance, and its identification rate is 93.5% at the magnitude of 6. Also, the identification time of the Hausdorff algorithm has been compared with the pyramid algorithm and some geometric algorithms. The results show that the Hausdorff identification algorithm has the shortest identification time which makes it suitable for real-time applications
reviewed article
Material science
Maedeh sadat Zoei; S. Javid Mirahmadi; Mojtaba Forghani; mohammad chiani; Saeed Asghari
Abstract
Thermal barrier coatings (TBCs), are advanced ceramic systems that are usually applied to the surface of hot industrial parts to improve equipment performance at higher temperatures. During each thermal cycle, due to the mismatch in the coefficients of thermal expansion of TBC layers, these layers expand ...
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Thermal barrier coatings (TBCs), are advanced ceramic systems that are usually applied to the surface of hot industrial parts to improve equipment performance at higher temperatures. During each thermal cycle, due to the mismatch in the coefficients of thermal expansion of TBC layers, these layers expand and contract unbalanced. The resulting thermal stresses cause the nucleation and growth of microcracks in the TBC system. After several hundreds of thermal cycles, the microcracks eventually combine and form a relatively large crack that causes spallation and separation of the coating, exposing the parts to high temperatures and ultimately leading to catastrophic failure of the entire equipment. The creation of self-healing capability provides the ability to repair cracks spontaneously. In this article, various types of technologies for achieving self-healing in YSZ thermal barrier coatings and the structure and properties of the resulting coatings have been introduced and reviewed. After extracting the technologies of applying self-healing thermal barrier coating and comparing them with each other, it is possible to obtain coatings with self-healing properties according to the needs of each industry and then determined the proper composition of the self-healing coating, the proper thickness of the self-healing coating layer, the proper arrangement of the self-healing coating layer and the parameters of the coating process
Original Article
adel Pourtaghi Marzrood; Arezoo Esmaeili; adel Pourtaghi marzrood; Moharram Shameli
Abstract
Backflow is a phenomenon that occurs due to the increase of upstream pressure compared to downstream pressure. In converging-diverging nozzles, by increasing the outlet pressure compared to the design pressure, the phenomenon of backflow is observed in the divergent part, which causes a decrease in the ...
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Backflow is a phenomenon that occurs due to the increase of upstream pressure compared to downstream pressure. In converging-diverging nozzles, by increasing the outlet pressure compared to the design pressure, the phenomenon of backflow is observed in the divergent part, which causes a decrease in the output velocity and thrust. In this paper, a converging- diverging nozzle with suitable expansion ratio for vacuum condition is selected and the propellant flow, which is considered as butane in this research, is simulated by finite volume method for output pressure equal to vacuum pressure and atmospheric pressure conditions. It has seen that in the atmospheric pressure, backflow occurs in the nozzle in order to determine the appropriate expansion ratio for the nozzle operating in atmospheric pressure, the flow inside the nozzle is simulated for the different expansion ratios and the average outlet axial velocity at the output of theses nozzles is obtained. According to the results, the most suitable expansion ratio of the surface has the highest average axial velocity. Also, to verify the obtained results from finite element simulation, four nozzles with different surface expansion ratios were manufactured and the thrust force obtained from experimental test on the measuring stand with equivalent results obtained from the simulations were compared
Original Article
Material science
maryam salvatifar
Abstract
One of the most serious problems of the industrialized world is heavy metal contamination. As a heavy metal, lead has very harmful effects on human health even in small amounts. Therefore, removing it from water is one of the most important challenges in public health system. Microorganism application ...
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One of the most serious problems of the industrialized world is heavy metal contamination. As a heavy metal, lead has very harmful effects on human health even in small amounts. Therefore, removing it from water is one of the most important challenges in public health system. Microorganism application is very useful and safe in this field. Creatures living on Earth are constantly under the influence of gravity, and if it changes, they will be affected by a unique shock. Such a change has effects on the structure and function of cells by interfering with biochemical pathways and gene expression. Investigating these changes, in addition to maintaining the health of astronauts, will also be useful for improving the quality of human life on earth. In this study, the efficiency of Lactobacillus acidophilus ATCC 4356 bacteria in the bioremoval of lead from aqueous solution was investigated in microgravity and Mars gravity conditions. The results showed a decrease in lead concentration after 24-hour treatment by 82.1% under microgravity conditions, 79.6% under simulated Mars gravity conditions and 70.6% under natural Earth gravity conditions. Therefore, by reducing the gravity, it is possible to increase the efficiency of L. acidophilus in the bioremoval of lead metal
Original Article
Telecommunication
Hossein Eskandari; Razieh Narimani; Elham Hosseini
Abstract
In this paper a waveguide antenna to create a saddle shaped pattern for remote sensing satellite applications has been introduced, and a method to excite a waveguide as feeding X-band antenna with the aim of achieving circular polarization has been presented. With the use of a circular microstrip probe, ...
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In this paper a waveguide antenna to create a saddle shaped pattern for remote sensing satellite applications has been introduced, and a method to excite a waveguide as feeding X-band antenna with the aim of achieving circular polarization has been presented. With the use of a circular microstrip probe, the mode inside the cylindrical waveguide is stimulated in such a way that the antenna has circular polarization with only one feeding input, and in addition, the input impedance of the antenna is fifty ohms. To achieve the saddle-shaped pattern, plus-shaped guides have been used. These guides are printed as microstrips on the Rogers 5880 substrate. The innovation of this article is in the simultaneous use of directional elements to create a saddle-shaped pattern and a circular probe to create circular polarization in order to design a suitable antenna for LEO remote sensing satellites. After simulation, the antenna was fabricated and tested. The test results show that the antenna has a real gain of more than 3 dBi at angles of θ = ±65. The axial ratio of the antenna is less than 3 dB in the working frequency for θ values between ±50, which shows that the antenna has a desired circular polarization in this θ angle range.
Original Article
Space engineering
Roya Sanaie; Pouya Talebinejad; Seyed Mohammadjavad Tabatabiee; Mahdi Fakoor
Abstract
The solar array ,one of the main parts of the satellite's electrical power subsystem, is responsible for providing the required electrical power for the satellite during the mission. Micrometeorites and small space debris are considered serious risk for the satellite mission. Due to the number of satellites ...
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The solar array ,one of the main parts of the satellite's electrical power subsystem, is responsible for providing the required electrical power for the satellite during the mission. Micrometeorites and small space debris are considered serious risk for the satellite mission. Due to the number of satellites in orbit, space debris is increasing. The impact of micrometeorites or orbital debris on the solar panels of the satellite can damage the internal structure of the panel, which causes a drop in the electrical power of the satellite. In this article, along with the numerical and geometrical simulation of the solar panels of the MEO communication satellite, an algorithm based on the direct random impact of micrometeorites and orbital debris on the solar panels has been presented, and their damage rate has been calculated. The size of meteorites and space debris is determined based on the average size of the particles in the earth's orbit. After summarizing the collision results, the redundant solar panel has been simulated based on the minimum and maximum damage to compensate for the satellite power loss. The results show that the redundant solar panel can compensate the loss of satellite power after the collision and estimate the extent of damage as soon as possible
Original Article
Amirreza Kosari; Elahe Khatoonabadi; Aida Kazemi; reza amjadifard; Vahid Bohlouri
Abstract
This paper investigates solar activities and its phenomena from the perspective of risks on the functioning of urban infrastructures, industrial systems and economic structure affected by such phenomena. Also, according to the existing analyzes and results, the basic requirements to prevent the severity ...
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This paper investigates solar activities and its phenomena from the perspective of risks on the functioning of urban infrastructures, industrial systems and economic structure affected by such phenomena. Also, according to the existing analyzes and results, the basic requirements to prevent the severity of the resulting injuries have been introduced. Space weather events can cause disruptions in the power grid, telecommunications and radio communications, airlines, railways, and in addition cause damage to pipelines, oil and mining industry, and aviation each of these cases it is examined as an economic infrastructure in this paper. Also, the effect of these phenomena in damage and dysfunction in satellites that are used for global positioning, telecommunications and weather forecasting has been investigated. Considering the importance of the items mentioned in this article, an attempt has been made to investigate the research done in some other countries regarding the impact of space weather phenomena on socio-economic systems and to study the disruptions and failures caused by this impacts in the industries and socio-economic infrastructures of the society. This studies can help in the formation of the necessary fields and preventive actions in facing the dangers of space weather in order to lead the scientific community to investigate similar cases in the country in order to create management arrangements and related technological
