Original Article
Propulsion
Mohammad Hossein mansouri Moghari; Hassan Naseh; Sahar Noori
Abstract
Accurate solving of complex systems such as space systems and specifically space propulsion system is very costly and time consuming. By developing and building a surrogate model, the solution time and the cost can be reduced. The closer the surrogate model is to the actual model, the more accurate the ...
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Accurate solving of complex systems such as space systems and specifically space propulsion system is very costly and time consuming. By developing and building a surrogate model, the solution time and the cost can be reduced. The closer the surrogate model is to the actual model, the more accurate the solution and the lower the error rate. High-precision successor models are called metamodels. The basis of producing a high-precision meta-model is to perform high-precision sensitivity analysis with a suitable method. Sensitivity analysis can show the effect of input variables on output variables and produce a surrogate model by eliminating ineffective input variables. Therefore, sensitivity analysis is of great value in solving complex systems. The purpose of this paper is to analyze the sensitivity of the multidisciplinary design of a monopropellant liquid propulsion system by the Latin Hypercube Sampling method. In this article, the topics related to the liquid monopropellant propulsion system are divided into six parts: High pressure gas tank, liquid fuel tank, injector, decomposition chamber, catalytic bed and nozzle. By determining the input and output variables of each subject, the results of sensitivity analysis are displayed in two ways: the sensitivity of the input variables to the output and the two-by-two correlation of the parameters with each other. In the results, as can be seen, the specific impulse input variable, in the high-pressure gas tank and the liquid fuel tank, has no effect on the output variables. In the injector, the number of grooves, groove angles and fuel tank pressure do not have a significant effect on the output variables. In the decomposition chamber sensitivity analysis diagram, the radius of the granule and for the catalyst bed, in addition to the radius of the granule, the percentage of ammonia decomposition are also ineffective. Finally, the sensitivity analysis for the nozzle shows that the ratio of specific heat has no effect on the output variables.
Original Article
Heat control
Mehrnoosh Farahani; Vafa Sedghi; seyed mostafa safavi homami; Hamid Mesforoush
Abstract
The ions in the space environment cause the surface and internal charging phenomenon in satellites. The accumulated potential during the charging phenomenon can cause electrostatic discharge and seriously endanger the satellite telecommunication components. The purpose of this paper is to investigate ...
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The ions in the space environment cause the surface and internal charging phenomenon in satellites. The accumulated potential during the charging phenomenon can cause electrostatic discharge and seriously endanger the satellite telecommunication components. The purpose of this paper is to investigate the possibility of electrostatic discharge on satellite surfaces in low earth orbit (LEO) environment and to reduce this possibility in order to reduce the risk of damage to satellite surfaces and components. First, the surface charging phenomenon is simulated in an aluminum satellite in low earth orbit and then in polar aurora by SPIS software. Then multi-layer thermal insulation is applied to the system and its effects on the charging phenomenon are investigated. Research has shown that adding MLI layers will increase the risk of electrostatic discharge. Therefore, in the next steps, the effect of the grounding system in reducing the risk was investigated. By connecting the layers to the ground in a proper way, the possibility of discharge between the layers and the body and between the layers with each other is minimized, which leads to the achievement of an optimal system.
Original Article
Propulsion
masumeh kiantaj; morteza farhid; mohammadmehdi shafie; Mohammad reza morad
Abstract
In this article, the characteristics of the hollow cathode plasma particles in the spt-100 hall effect thruster are investigated by two-dimensional particle-in-cell simulation. One of the main and important components of the hall thruster is hollow cathode which plays two important tasks: one part of ...
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In this article, the characteristics of the hollow cathode plasma particles in the spt-100 hall effect thruster are investigated by two-dimensional particle-in-cell simulation. One of the main and important components of the hall thruster is hollow cathode which plays two important tasks: one part of the electrons that come from the cathode used for anode propellant ionization, and the other part plays the important role of neutralizing the ion beam coming out of the thruster. Therefore, the study of the hollow cathode characteristic is importance. Krypton is used as fuel in this system. The behavior of the potential, the density of electrons and ions and the temperature of particles has been studied. The results show that corresponding the electrons, the ion density also decreases exponentially from the maximum value in the cathode ionization region through outer chamber. Also, analyzing normalized radius regard to electron density shows that the cathode effective area in which the radius electron temperature reaches maximum value is located about 1.5mm from the center line of the hallow cathode.
Original Article
mechanic
Sajjad Ghazanfarinia; Ehsan Mousivand; Masoud Khoshsima; Yaser Saffar
Abstract
This research is going to present design of a LEO Constellation for Navigation service with minimum number of Satellites. The goal is to achieve Dilution Of Precision (DOP) less than 6. This Requirement is going to be achieved using predefined launch vehicles limitation on orbit which is 500 km in circular ...
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This research is going to present design of a LEO Constellation for Navigation service with minimum number of Satellites. The goal is to achieve Dilution Of Precision (DOP) less than 6. This Requirement is going to be achieved using predefined launch vehicles limitation on orbit which is 500 km in circular orbit altitude and 55 degrees for orbit inclination. Design has been done based on Analyses resulting in Optimization for least number of Satellites in this orbit, to satisfy all requirements for Navigation Performance and in conformance with the constraints related to launch and orbit. Multiple analyses have been done resulted in Constellation with 324 satellites, formed in 18 Orbits with 18 Satellites in each. This design shows the performance of 4.7 in DOP for a User located in Tehran, however, the distribution of DOP over the target area shows that the requirement has been passed through the whole region.
Original Article
Structure
Alireza Zarezadeh; Mohammad Hossein Allaee; Mohsen Heydari Beni; Ali Davar; Jafar Eskandari Jam
Abstract
The filament winding process is one of the most important and widely used processes in the manufacture of composite structures in order to achieve high strength and rigidity. In this process, there are important parameters such as fiber tension, how the fibers are twisted, the effect of layering, twisting ...
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The filament winding process is one of the most important and widely used processes in the manufacture of composite structures in order to achieve high strength and rigidity. In this process, there are important parameters such as fiber tension, how the fibers are twisted, the effect of layering, twisting angle, twisting pattern of fibers, materials, etc. which can play a significant role in this process. In this regard, the twisting pattern has been less studied by researchers than other parameters. In this research, the effect of fiber twisting pattern on the hydrostatic pressure threshold of epoxy glass cylinder has been investigated. For this purpose, glass/epoxy cylinders with 4 different twisting patterns were made with ± 54 arrangement and subjected to hydrostatic test with internal pressures of 5-50 bar, where the amount of radial displacement in the middle of the cylinder was measured experimentally. In the following, the radial displacement of cylinders due to the internal pressure was also modeled using numerical analysis (Abaqus) and compared with experimental results. In order to validate the experimental and numerical results, theoretical model was used and the results were compared. All of the results obtained were in acceptable limits and showed that the pattern having finer texture has a higher compressive strength. Also, the simulation results showed a good agreement with the experimental results.
Original Article
Propulsion
Nematollah Fouladi; Alireza Mohammadi
Abstract
The purpose of this research is to evaluate a ground test bed of an orbital transmission engine with pre-evacuation of the engine's internal space. In the usual tests on the ground, the initial pressure of the engine is atmospheric pressure. While during the orbital mission, the internal space of the ...
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The purpose of this research is to evaluate a ground test bed of an orbital transmission engine with pre-evacuation of the engine's internal space. In the usual tests on the ground, the initial pressure of the engine is atmospheric pressure. While during the orbital mission, the internal space of the engine may be in the vacuum pressure. Therefore, it is necessary to test the performance by pre-evacuating its internal space. In this research, the suitability of an exhaust diffuser for this type of test is investigated numerically. The unsteady numerical simulations have been done by applying the pressure-time profiles of the engine as the boundary condition of the inlet pressure. Investigations show that the two phenomena of flow being supersonic in the diffuser at very low engine pressures and the discharge of the return flow to the vacuum chamber prevent the significant influence of environmental conditions on the flow inside the nozzle. So, from the initial moment to the stable working of the diffuser, the flow in the first half of the nozzle is in the supersonic state. Therefore, the internal ballistics of the engine is evaluated independently of the conditions of the outside environment.
Original Article
control
Elham Kowsari; Hadi Makarem
Abstract
Star tracker is one of the most important devices used on satellites for attitude determination. Since its output is discontinuous, it needs to be aided to complement its discontinuity. Using gyroscope unit is the most suitable choice for aiding the star tracker. However, using these two kinds of sensor ...
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Star tracker is one of the most important devices used on satellites for attitude determination. Since its output is discontinuous, it needs to be aided to complement its discontinuity. Using gyroscope unit is the most suitable choice for aiding the star tracker. However, using these two kinds of sensor simultaneously has some challenges. In other words, not only biases lead to low accuracy in the attitude determination, but also the installation error has a significant effect on the accuracy. In this paper after presenting the important role of installation errors between star tracker and gyroscope in the accuracy of attitude determination, an effective method is proposed to determine the misalignment error between these two sensors which is based only on their measurements, and the mathematical formulation is presented in detail. Then, to validate the performance of the proposed method, it is implemented to calculate the instantiation error of an experimental dataset gathered in the Mount Pooladkaf, for which the results are reported.
Original Article
Material science
Sajede Aghasi; Seyed Hassan Jafari; Mahdi Golriz
Abstract
One of the methods for improving thermal conductivity of epoxy adhesives is the incorporating of conductive ceramic, metal or carbon fillers. As the main goal of this research, is to improve thermal conductivity of epoxy resin and keep its electrically insulating property, Alumina (Al2O3) ceramic filler, ...
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One of the methods for improving thermal conductivity of epoxy adhesives is the incorporating of conductive ceramic, metal or carbon fillers. As the main goal of this research, is to improve thermal conductivity of epoxy resin and keep its electrically insulating property, Alumina (Al2O3) ceramic filler, individually and in combination with Boron Nitride (BN) ceramic filler with high thermal conductivity and electrical resistivity. Scanning Electron Microscopy (SEM) observations showed a good dispersion and an acceptable connection between fillers. Thermal diffusivity measurements revealed that by incorporating conductive ceramic fillers, either individually or in combination with each other, regardless of the type of the hardener, thermal diffusivity would increase as a result of the formation of thermal conductive networks. Although, in hybrid system, because of bridging effect between particles, thermal diffusivity will notably increase. Therefore, using hybrid system of Alumina/BN along with long chain polyamine curing agent is a suitable choice for the preparation of thermally conductive yet electrically insulating epoxy adhesives in space industries. The results show that the thermal conductivity of hybrid system of Alumina/BN have been raised to 1.7 (W/mK) instead of 0.4 (W/mK) which is belong to pure epoxy system. The most important point of this work is that the good thermal conductivity obtained by kept of mechanical properties, dielectric constant, as well as lap shear strength of Alumina/BN hybrid system meet all acceptable range of thermal conductive adhesive for space application.
reviewed article
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 studied before. Consequently, multiple examples have been reviewed and researched in hybrid control science. Some of these examples are used as benchmarks to improve the performance comparison of control methods or to check their comprehensiveness. Therefore, this article has 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 being well recognized. 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 accurately and efficiently and proceed with the investigation and design of the controller.
Original Article
Mission design
Yaser Saffar; Sajjad Ghazanfarinia; Masoud Khoshsima; Shiva Emami
Abstract
This paper reviews design of Constellation for independent satellite-based navigation system with Middle East region coverage for regional positioning and augmentation service. Space segment of this constellation is composed of nine satellites in four orbits in such way three satellites have been placed ...
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This paper reviews design of Constellation for independent satellite-based navigation system with Middle East region coverage for regional positioning and augmentation service. Space segment of this constellation is composed of nine satellites in four orbits in such way three satellites have been placed on one GEO and two satellites on each three IGSO. In the coverage area, ground segment includes eleven ground monitoring stations, two masters and tracking control stations and twenty wide area reference stations are assigned only for augmentation with their master and uplink stations. Here we centered on space segment and specially design a navigation constellation system as a main orientation in this investigation and evaluation of the performance of the navigation system by combination with other satellite-based navigation systems. Hence, the parameters corresponding to navigation accuracy have been analyzed and compared with other active GNSS constellations. Analyses results express that geometric accuracy (GACC) of the designed system is solely 16 meters in 95% of a day in all points of desired area and in the case of combination with BeiDou and GPS the GACC would be improved to 14 and 12.5 meters respectively.
Original Article
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. Main mission is imaging from earth by three camera named MS, SWIR, TIR. PARS1 OnBoard Software (OBSW) is developed as a performance platform, satellite components control, data management, algorithm management included normal status ...
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PARS1 Satellite is a Remote Sensing satellite with a 3-years mission. Main mission is imaging from earth by three camera named MS, SWIR, TIR. PARS1 OnBoard Software (OBSW) is developed as a performance platform, satellite components control, data management, algorithm management included normal status control and event handling. Because of OBSW complexity and its different features, it has more priority than other subsystems in satellite. So PARS1 satellite OBSW design, development and test is a useful platform for gaining of worthwhile experiences in the field of satellite onboard software which is very wide and complicated in its field. So we decided in this paper to present here as lesson-learned and results experiences. These results is gained from development and test phase from developer and tester view. Use of these experiences will be very efficient in smoothing of test and development path in future projects and works in Satellite Research Institute.
Original Article
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. Design constraints include the buckling load multiplier (buckling safety factor) above 1.5 and Von Mises stress below 100 MPa. In this problem, first, according to the permissible limits of the design variables, a design of experiment and then a sensitivity analysis have been 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 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. It has also been observed that at the selected design point, Von Mises stress is 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.
