Propulsion
Sahar noori; Rojin Shokri Khanghah; mohammad nadafipour meibody
Abstract
Microwave electrothermal thruster is the propellant that converts microwave energy into heat energy. nowadays, with the technology development of electric thrusters are very important in terms of producing high specific impact and low fuel consumption. These thrusters can produce acceptable thrust over ...
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Microwave electrothermal thruster is the propellant that converts microwave energy into heat energy. nowadays, with the technology development of electric thrusters are very important in terms of producing high specific impact and low fuel consumption. These thrusters can produce acceptable thrust over a long period of time, which are suitable for spiral orbital transfer missions. In this type of propulsion, the propellant gas is heated and expanded, which produces the propulsion force. This paper presents the conceptual design process of a microwave thermal thruster. The propulsion system includes propellant, propulsion storage tank, amplification chamber, and power plant, which includes batteries and solar arrays. In this paper, the method of calculating the mass and the characteristics of each are presented in detail. Finally, in order to validate the conceptual design process presented in this study, the necessary studies have been discussed. Conceptual design has been done for a 100 kg satellite, which is desirable to travel in a week from an orbital height of 300 to 800 km during a spiral treansfer. The propulsion system and mass of each subsystem are obtained.
Control
ali safi; ali taghavian; Esmaeel Khanmirza
Abstract
Due to various and complex phenomena in hybrid dynamical systems, the control of these types of systems has faced a challenge. Space systems also have hybrid dynamics due to different missions and operational modes. Therefore, to deal with these systems, we must first familiarize ourselves with the standard ...
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Due to various and complex phenomena in hybrid dynamical systems, the control of these types of systems has faced a challenge. Space systems also have hybrid dynamics due to different missions and operational modes. Therefore, to deal with these systems, we must first familiarize ourselves with the standard examples that have been studied before. Consequently, in the field of hybrid control science, various examples have been reviewed and researched. In order to improve the performance comparison of control methods or to check their comprehensiveness, some of these examples are used as benchmark examples. Therefore, this article has been tried to collect benchmark examples with different characteristics in the hybrid control field and compare them with each other. It should be noted that benchmark examples were selected based on the number of repetitions and recognition. Therefore, the performance of the developing controllers can be examined on these examples and compared with the results of other controllers. As a result, the researchers can choose their desired benchmark more accurate and efficient with the investigation and design of the controller
control
Morteza Farhid; Hossein Beheshti; Masoud Abbaspour; Mohammad Aslanimanesh
Abstract
In this paper, the results of the process of analyzing potential failure situations on the operational product of the reaction wheel condition control operator are discussed and the effects of the identified failure situations are eliminated or reduced. The technique of analyzing failure modes and their ...
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In this paper, the results of the process of analyzing potential failure situations on the operational product of the reaction wheel condition control operator are discussed and the effects of the identified failure situations are eliminated or reduced. The technique of analyzing failure modes and their effects is the first technique in meeting the requirements of reliability in design. In this regard, the block diagram of the functional flow of the reaction wheel is presented for the first time and the dependence of the functions is presented statically in the form of a matrix. To achieve this goal, the different parts of this operation are identified and their failure modes and the cause of failures of each part are determined. Also, the effects of failure of different levels will be determined locally, at the equipment level, at the subsystem level and at the system level. In addition, the way to diagnose failure and deal with the effect of failure is presented and related analysis is performed, which is a quantitative analysis and will determine the parameters of severity of error effect, probability number and criticality number, calculation and critical items. Then, based on the identified critical sections, a list of critical items is also extracted. The information extracted from the analysis of failure modes and their effects, while helping to improve the reliability of the design of the reaction wheel operator, will provide the designer with important data for fault and error management during the test and mission stages
Structure
Maedeh sadat Zoei; hadi gorabi; mohammadreza asharf khorasani; saeed asghari; S. Javid Mirahmadi
Abstract
Space systems in Low Earth Orbit (LEO) expose to the destructive parameter of atomic oxygen. In long-term missions, the rate of degradation of the material resulting from the reaction with atomic oxygen is significant and reduces the performance of the structure. Due to the harmful effects of atomic ...
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Space systems in Low Earth Orbit (LEO) expose to the destructive parameter of atomic oxygen. In long-term missions, the rate of degradation of the material resulting from the reaction with atomic oxygen is significant and reduces the performance of the structure. Due to the harmful effects of atomic oxygen on materials, the choice of atomic oxygen resistant materials or the use of durable surface coatings is very common. In this study, the corrosion resistance of atomic oxygen of an interconnector part of a solar cell has studied by applying a silicone base coating. In order to investigate the corrosion behavior of atomic oxygen, ground test method with equivalent conditions of LEO orbit has used by DC plasma equipment. Initially, the parameters of the atomic oxygen corrosion ground test determined under the equivalent conditions of the LEO orbit. The results of atomic oxygen application in this study showed that the amount of atomic oxygen erosion yield of silicon coating is significantly lower than the amount of atomic oxygen erosion yield of silver substrate. The study of the coating surface after applying atomic oxygen by SEM images led to the determination of the optimal coating thickness. EDX results showed that after applying atomic oxygen, no significant change in the chemical composition of the coating has achieved
Mission design
Yaser Saffar; Sajjad Ghazanfarinia; Masoud Khoshsima; Shiva Emami
Abstract
In This paper, a domestic regional and independent satellite navigation system, known as "IRANSS" has been designed and analyzed to cover user needs in the Middle East Region. The Space Segment of this constellation is composed of nine satellites in four orbits, in such a way three satellites have been ...
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In This paper, a domestic regional and independent satellite navigation system, known as "IRANSS" has been designed and analyzed to cover user needs in the Middle East Region. The Space Segment of this constellation is composed of nine satellites in four orbits, in such a way three satellites have been considered in one GEO orbit [1] and two satellites are considered in each of three IGSO orbits [2]. Two main Tracking and Control Ground Stations and twenty wide area reference stations, assigned only for augmentation, form the Ground Segment. The focus of this research is on space segment and specially design a navigation constellation and satellites’ system design, and evaluation of the performance of the navigation system in combination with other satellite-based navigation systems, since Augmentation Systems prepare correction signals for a specific Navigation System by ground segment. STK is the main software used to design and analyze the performance of the system by DOP as a reference for Ranging Errors based on Constellation Geometry. All of design parameters are computed in a way to minimize GDOP with four satellites. The parameters of navigation accuracy have been compared with other active GNSS [3] constellations to evaluate error in the designed system. Analysis results express that the geometric accuracy of the designed system is solely 16 meters in 95% of a day in all points of the desired area and would be improved to 14 and 12.5 meters in the case of combination with BeiDou and GPS, respectively
Propulsion
mohamad ali amirifar; alireza rajabi; nooredin ghadiri masoom; zahra amirsardari; majid kamranifar
Abstract
In this research, the performance of a monopropellant hydrazine thruster in atmospheric conditions has been investigated experimentally. For this purpose, after designing and constructing the thruster according to the functional requirements of the thruster, a test was designed and after that, the desired ...
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In this research, the performance of a monopropellant hydrazine thruster in atmospheric conditions has been investigated experimentally. For this purpose, after designing and constructing the thruster according to the functional requirements of the thruster, a test was designed and after that, the desired thruster was tested in atmospheric conditions. The test results show that the tested thruster can generate 2000 pulses with a width of 0.5 seconds and a periodicity of one second with reproducibility. It was shown that the life of this thruster is more than 2000 pulses and the thruster was able to produce very small beats of 3 mNS in reproducibility. Also, comparing the results of the current thruster sample with the experimental results of other thrusters showed how by selecting the appropriate dimensions for the injector, catalyst chamber and nozzle, the characteristics of pressure rise time, minimum impulse, pulse centroid and pressure drop time in the Thruster can be well controlled. Reducing the injector diameter (by keeping the flow rate constant by increasing the injection pressure) reduces the impulse (within a constant pulse width) and increases the pressure rise time. Reducing the dimensions of the catalyst chamber also reduces the increase and decrease time of the pressure, resulting in a smaller pulse centroid
software
Fatemeh SalarKaleji; Parvin Shavandi; Alireza Omranian; Oveys Kazemi; Farzad Emami; shahrokh jalilian; Alireza Khani; Abolfazl Dayyani; Mohammad Sayanjali
Abstract
PARS1 Satellite is a Remote Sensing satellite with a 3-years mission. The main mission of this satellite is imaging the earth by three cameras named MS, SWIR and TIR. PARS1 OnBoard Software (OBSW) is developed as a performance platform, satellite components control, manage their data, algorithm management ...
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PARS1 Satellite is a Remote Sensing satellite with a 3-years mission. The main mission of this satellite is imaging the earth by three cameras named MS, SWIR and TIR. PARS1 OnBoard Software (OBSW) is developed as a performance platform, satellite components control, manage their data, algorithm management included normal status control and event handling. OBSW is more important than other satellite subsystems due to its complexity and different features. So, the design, development and test of the PARS1 satellite OBSW is a useful platform to gain valuable experiences in the field of satellite onboard software which is very wide and complicated in its field. Therefore, in this paper decided to present experiences which gained in this field, in the form of summary of achievements and lessons learned. These experiences is gained from development and test phase of the satellite and using of these experiences will be very useful and effective in smoothing of test and development path in future projects of the Satellite Research Institute
Mission Analysis
Mohammad Haji Jafari; Sahar Aminabadi
Abstract
In this paper, we investigate the orbital characteristics of a constellation consisting of 24 LEO satellites. All the configurations are based on the Walker Delta model, which include single- regulated (one constellation) and double- regulated (intertwined two constellations) models. For the sake of ...
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In this paper, we investigate the orbital characteristics of a constellation consisting of 24 LEO satellites. All the configurations are based on the Walker Delta model, which include single- regulated (one constellation) and double- regulated (intertwined two constellations) models. For the sake of comparability, it is assumed that the orbital period of all satellites is 127 minutes and regarding the maximum altitude of 2000 km, the three eccentricities of zero (circle), 0.19 (with an apogee of 2000 km) and 0.097 (=0.19/2) with the longest presence time on the mission area, are considered. In order to limit the search space, the inclination of all orbits is assumed 40 degrees and three values of 320, 340 and 360 degrees are considered for the argument of perigee in elliptical orbits. Examining the various scenarios, it can be seen that, Assuming the need for at least two observable satellites, basically, it can be found that for the argument of perigee of 320 degrees provides the best coverage beside the least standard deviation. As expected, the higher eccentric orbits perform better regardless of changes in signal strength. on the other hand, Double-regulated configurations can be associated with a larger number of satellites in view, which generally is accompanied by higher standard deviations. In General, a configuration may be chosen according to mission requirements and no one should be regarded as the absolute optimum.
Structure
hassan Naseh; Hadiseh Karimaei; mohammad lesani
Abstract
In this paper, the structural optimization of a space capsule has been discussed by approximating a thin-walled cylindrical shell with a certain length under the axial compression force and constant lateral pressure. Design variables include the outer diameter and cylinder thickness. The purpose of optimization ...
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In this paper, the structural optimization of a space capsule has been discussed by approximating a thin-walled cylindrical shell with a certain length under the axial compression force and constant lateral pressure. Design variables include the outer diameter and cylinder thickness. The purpose of optimization is to minimize the mass and maximize the frequency of the first vibration shape mode of the cylinder. The design constraints include the buckling load multiplier (buckling safety factor) above 1.5 and Von Mises stress below 100 MPa. In this article, first, according to the permissible limits of the design variables, a design of experiment (DOE) and then a sensitivity analysis was carried out to check the sensitivity of the objective functions and constraints to the design variables. After numerically solving the output values with the help of Ansys software and preparing the response surface, the optimal design point has been identified with the help of the two objectives optimization Genetic algorithm. Then, with the numerical simulation of the optimal point, the accuracy of the values obtained from the response surface method was checked and their accuracy was confirmed. The results show that at the selected design point, Von Mises stress becomes less than its allowed value, i.e. 100 MPa, and also the buckling load factor is more than twice its minimum allowed value. However, this point has the smallest distance from the origin and the optimum point has been chosen as the knee point
control
Sayyed Mohammad Mousavi; Sayyed Majid Esmailifar; Mohammad Chiniforoushan
Abstract
In this research, the time-optimal 6 degrees of freedom (6DOF) orbital rendezvous maneuver problem for an inertially asymmetric rigid spacecraft with independent attitude and position control actuators has been investigated. It is also assumed that the spacecraft is equipped with the thruster actuators ...
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In this research, the time-optimal 6 degrees of freedom (6DOF) orbital rendezvous maneuver problem for an inertially asymmetric rigid spacecraft with independent attitude and position control actuators has been investigated. It is also assumed that the spacecraft is equipped with the thruster actuators and the control forces and torques are generated along the three principal axes of the spacecraft. In order to obtain the time-optimal 6DOF maneuver state and control trajectories, at first, the relative translational and rotational dynamics of the spacecraft are described. Then, the Gauss pseudospectral method is used to solve the time-optimal control problem in the presence of constraints on control forces and torques. Also, the costates are estimated to first-order optimality proof of the obtained solutions. The Numerical simulation results show that for the assumed time-optimal 6DOF maneuver problem, the control structure for all of the control forces and torques is ‘bang-bang’. Eventually, the optimality of the obtained solutions is verified by checking the fulfillment of Pontrygain’s minimum principle
Propulsion
Nematollah Fouladi; sina afkhami; Mahmood PasandidehFard
Abstract
In the present study, the effect of pre- evacuation on starting process of a second throat exhaust diffuser has been investigated experimentally by examining a thrust optimized parabolic nozzle. An experimental setup called high- altitude test facility has been used with compressed air as operating fluid. ...
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In the present study, the effect of pre- evacuation on starting process of a second throat exhaust diffuser has been investigated experimentally by examining a thrust optimized parabolic nozzle. An experimental setup called high- altitude test facility has been used with compressed air as operating fluid. According to the importance of area ratio parameter (Ad/Ast) of a second throat diffuser, the effect of this parameter variation has been examined on the start- up performance of the nozzle and diffuser. In each of the diffuser geometries, in order to evaluate the instantaneous performances, the pressure in the nozzle chamber has charged instantly in two modes; with and without pre- evacuation. Then, the vacuum chamber pressure and static pressure distribution along the diffuser were measured by a data acquisition system. The results show that pre- evacuation in the test chamber reduces the start- up time of the diffuser by 50 to 60%. In addition, pre- evacuating the test chamber eliminates the destructive transition phenomenon from the flow separation pattern during start- up of the nozzle and diffuser. Also, It has been observed that with the narrowing of the diffuser’s second throat duct, the minimum starting pressure of the diffuser increases and eventually flow chocks at the second throat in a certain area ratio.
Structure
mohammadreza alijani nargesi; hasan haddadpour; Saeed Shakhesi
Abstract
One of the key issues in the operations of on orbit servicing to unmanned satellites is to provide a safe and reliable docking process. This paper investigates the dynamic behavior of a flexible probe in the central docking mechanism of unmanned satellites. For simulating the impact phenomenon, ...
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One of the key issues in the operations of on orbit servicing to unmanned satellites is to provide a safe and reliable docking process. This paper investigates the dynamic behavior of a flexible probe in the central docking mechanism of unmanned satellites. For simulating the impact phenomenon, a dynamic analysis software (MSC. Adams) has been applied and a three-dimensional model has created based on the assumption of a flexible clamped beam as a shock absorber. The results are in good agreement with similar theoretical and experimental results. additionally, it is possible to consider the parameters such as the type of connection between the beam and the concentrated mass, angular and translational velocity of chaser and target satellites, in order to determine the optimum condition to perform a successful docking operation. The results of this study indicate that the use of a spherical joint for the ball attached to the probe, significantly reduces the maximum value of impact force. Also, the rotation of the sphere leads to less change in the linear and angular velocity of the target satellite and increases the probability of successful mating of the satellites. On the other hand, the movement of the conical area relative to the target satellite reduces the maximum impact force and shock resulting on the satellites structure. As a result, the chance of successful docking increases.
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
Reza Amjadi Fard; Farhad Bagheroskouei
Abstract
Reliability assessment of power converters is extremely important due to the degradation of the converter performance under the thermal and electrical stresses. The space environment is one of the stressful environments for electronic components and equipment due to the range and high speed of temperature ...
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Reliability assessment of power converters is extremely important due to the degradation of the converter performance under the thermal and electrical stresses. The space environment is one of the stressful environments for electronic components and equipment due to the range and high speed of temperature changes.The normal or abnormal operation of a converter depends on the quality of the manufacturing process and the environmental and operating conditions. The failure indices usually are obtained based on the previous failures data which are calculated using the history of the main parameter of the converter. These indices are strongly influenced by the aging process. In this article, a new real-time indicator is introduced using the monitoring of the main parameters of the converter. The indicators are calculated using Replicator Neural Network (RNN). In fact, these indicators are obtained based on a comparison between a reference model of the converter in normal conditions and the estimation of abnormal operation of the converter in the future. In the proposed method, a normal distribution function is used to find the limits of error signals. The proposed method has several advantages such as considering all the uncertainties during the process of manufacturing the device, no need for the aging test data, and including all the failure types. In the Electrical power subsystem of a spacecraft, the reliability of power converters can be assessed based on the obtained data from the qualification models, benefiting the proposed method.
Telecommunication
Sahar Abdi; Morteza Cheheltanan
Abstract
In this paper, a wideband high-gain microstip patch array antenna for high resolution synthetic aperture radar applications is presented. The antenna operation frequency is in the X-band and the antenna structure is a four-layer configuration consisting of radiating patches, slots, coupling cavities, ...
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In this paper, a wideband high-gain microstip patch array antenna for high resolution synthetic aperture radar applications is presented. The antenna operation frequency is in the X-band and the antenna structure is a four-layer configuration consisting of radiating patches, slots, coupling cavities, and a corporate feeding network, which in turn is fed by a coaxial probe. The increased frequency bandwidth of the radiating patch is achieved by employing a square slot, which appears as a cavity for it, and improves the gain and impedance bandwidth of the antenna array by isolating the patch feeding slot and eliminating the mutual coupling effect. The whole antenna structure is fabricated by using a combination of the milling process and printed circuit technology. Measurement results show a relative gain bandwidth of more than 10%, in which the antenna gain is measured above 28.8 dBi over the frequency band of more than 1 GHz. Moreover, the relative impedance bandwidth of the antenna for VSWR>2 is more than 16%.
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
Material science
Zahra Amirsardari; Babak Afzali; Mohammad Reza Amirsoleimani
Abstract
To discuss the potential role of iridium (Ir) nanoparticles loaded under atmospheric conditions, we prepared a series of catalysts with the same active phase but different contents of 10wt%, 15wt%, and 20wt% on gamma-alumina for decomposition of hydrazine. The performance of the catalysts was better ...
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To discuss the potential role of iridium (Ir) nanoparticles loaded under atmospheric conditions, we prepared a series of catalysts with the same active phase but different contents of 10wt%, 15wt%, and 20wt% on gamma-alumina for decomposition of hydrazine. The performance of the catalysts was better with 15wt% and 20wt% of the Ir nanoparticles, and also the selectivity to hydrogen was about 27%. An increase in the reaction rate from 181 h-1 to 218 h−1 was observed in the loading of 15% by weight of iridium particles due to the good dispersion of the active phases by preventing surface agglomeration. As a satisfactory result of this investigation, Ir catalysts with different weight percentage (15wt% and 20wt%) showed the same activity and selectivity, and are suitable substitutes for each other. Using a catalyst with a lower weight percentage of the active phase and high activity is economically acceptable due to its low cost.
Material science
mojtaba forghani; Maedeh sadat Zoei; Mohammad Reza Pakmanesh; mohammad chiani; Saeed Asghari
Abstract
The sandwich panel is an important element of the satellite structure which various metal and composite materials are used to make its faces. Anodizing is used as a conversion coating in order to achieve the final properties of the panel surface and stability in the space environment. Anodizing is an ...
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The sandwich panel is an important element of the satellite structure which various metal and composite materials are used to make its faces. Anodizing is used as a conversion coating in order to achieve the final properties of the panel surface and stability in the space environment. Anodizing is an electrochemical process in which an oxide layer is formed using electricity. During the anodizing process, concentration polarization is created and the process is stopped when the limiting current resulting from the movement of electrical charges between the surface of the anodic layer and the electrolyte is increased. By stopping the process without spending enough time to obtain a thickness sufficient for colorability, a black anodic layer for use in space coatings is not obtained. In this research, by performing the anodizing process in four container of 250, 500, 2000 and 40000 cm3, the effect of the volume of the electrolyte on the wear and corrosion and optical-thermal properties of the layer obtained in each of the processes was investigated. The results showed that with the increase in the volume of the electrolyte caused by the increase in the volume of the container, the stopping time of the process increases. The evaluation of optical-thermal properties, wear resistance and corrosion resistance was done by infrared emission coefficient and solar absorption test, pin on disk test and salt spray test, respectively. The results of measuring optical-thermal and wear and corrosion properties for three container with volume of 500, 2000 and 40000 cm3 showed that with the increase in the volume of electrolyte and the process completion time of the process, the thickness of the anodic layer increased, which improved the optical-thermal properties, corrosion and wear resistance.
Power Electronics
Ashkan Nahvibayani; Shaghayegh Baktashian; Mohsen Babaiee; Rahim Eqra
Abstract
One of the reasons for the increasing popularity of lithium- ion batteries is the improvement of their rate capability and power density. All components of a battery, including the anode, cathode, electrolyte, and separator, can limit the capability of lithium-ion batteries. While most efforts have focused ...
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One of the reasons for the increasing popularity of lithium- ion batteries is the improvement of their rate capability and power density. All components of a battery, including the anode, cathode, electrolyte, and separator, can limit the capability of lithium-ion batteries. While most efforts have focused on the new electrode architecture and electrolyte formulation to improve battery performance, studies on separators have focused mainly on their mechanical and physical properties and little attention has been paid to their effect on the performance of lithium-ion batteries. In this study, a comprehensive study of the physical, thermal and electrochemical properties of disassembled high drain lithium- ion battery separator (HDLIB) with high discharge rate capability and commercial polyethylene separator with a thickness of 16µm (G16) is reported. According to the research, it has been shown that HDLIB separator has 26% less contact angle and better wettability than commercial polyethylene separator. Also, HDLIB separator at 150°C has shrunk by 55.6% less than G16, which may be due to the presence of boehmite ceramic particles in its structure. In addition, it shows that HDLIB separator can play an important role in improving the rate performance and safety of lithium- ion batteries
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
Control dynamics
Somayeh Jamshidi; mehdi mirzaei
Abstract
This paper compares spacecraft attitude control in the presence of disturbance torque using an adaptive backstepping controller and an extended state observer-based backstepping controller. Firstly, the adaptive backstepping controller is designed, in which the unknown parameters in a specific disturbance ...
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This paper compares spacecraft attitude control in the presence of disturbance torque using an adaptive backstepping controller and an extended state observer-based backstepping controller. Firstly, the adaptive backstepping controller is designed, in which the unknown parameters in a specific disturbance model are estimated using an adaptive law so that the closed-loop system is stable. Afterward, the backstepping control based on the extended state observer is designed. In this approach, the standard backstepping controller is initially designed, and then disturbances with a completely unknown model are estimated by the extended state observer, and the disturbance is rejected by applying the feed-forward law. The simulation results for two different disturbance models show that the backstepping controller based on the extended state observer demonstrates very good results compared to the adaptive backstepping controller when no disturbance information is available. This is for the reason that the extended state observer estimates the uncertainties more accurately.
Heat control
Nematollah Fouladi; Mohammad Farahani; Milad Mahdian Dowlatabadi
Abstract
The aim of this study is to evaluate the performance of water-jacket cooling system for thermal protection of exhaust large dimension diffuser at high heat fluxes in a wide range of coolant pressure. For this purpose, using the developed calculation code, the parameters of the water-jacket cooling system ...
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The aim of this study is to evaluate the performance of water-jacket cooling system for thermal protection of exhaust large dimension diffuser at high heat fluxes in a wide range of coolant pressure. For this purpose, using the developed calculation code, the parameters of the water-jacket cooling system are determined so that in addition to satisfying the temperature conditions of the metal body, the total pressure drop has remained in the desired range. In the following, the capability of numerical code to design and performance analysis of the cooling system has been evaluated in coolant pressure of 3 to 50 bar and high heat fluxes up to 3.5 MW/m2. The present studies show that the proper selection of coolant pressure is very important in the design of the cooling system with optimal mass flow rate and minimum coolant dimensions, especially at high heat fluxes, so that increasing the coolant pressure from 3 to 10 bar, in addition to significantly reducing the dimensions of the cooling system, reduces the mass flow rate by 75%.
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
Telecommunication
mohammadhossein ashouri; saeed fakhte; IMAN ARYANIAN
Abstract
This article presents a solution for reducing the height of magneto-electric dipole antennas by using an artificial magnetic conductor structure as the antenna's ground plane. Two types of antennas were investigated: a linearly polarized antenna and a right-handed circularly polarized antenna. For the ...
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This article presents a solution for reducing the height of magneto-electric dipole antennas by using an artificial magnetic conductor structure as the antenna's ground plane. Two types of antennas were investigated: a linearly polarized antenna and a right-handed circularly polarized antenna. For the linearly polarized antenna, a 7 x 7 array of artificial magnetic conductor cells (AMCs) was designed at 3.5 GHz and placed on the antenna's ground plane. By adding artificial magnetic conductors, the height of the first antenna was reduced to 0.16 λ. The simulation results show that the impedance bandwidth for values of |S11|<[-10dB] is 1.9 GHz from 2.3 GHz to 4.2 GHz (58.46%), while the measured impedance bandwidth of fabricated prototype is 2.13 GHz from 2.21 GHz to 4.34 GHz (65.03%). The second antenna, which is a right-handed circularly polarized magneto-electric dipole antenna fed by a Y-shaped feed line, has also been improved using an artificial magnetic conductor structure on its ground plane. A 5 x 5 array of AMC cells is used to reduce the height of the antenna to 0.13 λ. The simulation results show an impedance bandwidth of 1.24 GHz from 2.46 GHz to 3.7 GHz (40.25%), while the fabricated prototype has an impedance bandwidth of 1.3 GHz from 2.38 GHz to 3.68 GHz (44.52%).
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
