Journal of Space Science and Technology
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Journal of Space Science and Technologyendaily1Wed, 22 Jun 2022 00:00:00 +0430Wed, 22 Jun 2022 00:00:00 +0430Active Vibration Control of a Maneuvering Flexible Spacecraft using Hybrid Actuators: A Lyapunov-Based Control Approach
http://jsst.ias.ir/article_122467.html
This paper presents a study concerning active vibration control of a smartو flexible spacecraft during attitude maneuver using thrusters and reaction wheels (RW) in combination and piezoelectric (PZT) sensor/actuator patches. The large-angle maneuver and residual vibration of the spacecraft are controlled using an extended Lyapunov-based design (ELD) and strain rate feedback (SRF) theory for a two-mode mission. The overall stability of the system including all energetic terms has been proved and the control law has been derived accordingly. A pulse-width pulse-frequency (PWPF) modulation is used to alleviate the excitations of high-frequency flexible modes. Hence, the SRF algorithm using PZT is applied to prepare further vibration suppression. A great feature of the proposed hybrid actuator system is the switching time of the thrusters and RW, which is based on total systems energy. The numerical results for a flexible spacecraft with agile and precise maneuver requirements through a comparative study verify the merits of the proposed approach.کنترل وضعیت سه محوره یک ماهواره با استفاده از روش پارامتر متغیر
http://jsst.ias.ir/article_137254.html
This article introduces a parameter estimation method from continuous-time models for a variable parameter system. In the variable parameter linear method, which is used to express systems with time-varying state-space matrices, the stability and performance of the feedback system are guaranteed, and there is a significant potential for improving efficiency. The dynamics of these systems depend on a variable parameter with time, considered in this research as the angular velocity of the reaction wheel. The values of this parameter are during an unknown period but can be measured by system performance. Using the tabulation gain technique, the stability of the variable parameter system is checked, and the tabulation parameter is selected for estimating practical control factors. The convex algorithm can solve the extracted sufficient conditions converted into linear matrix inequality conditions. By solving these controlling conditions, the tabulated gain is obtained to guarantee the stability and performance of the variable parameter system. Numerical simulation results show the success of the proposed method.Extensive Regional Telecommunications Coverage in Emergency Condition using Tethered-Balloon Equipped with Antenna Pointing Mechanism – Part 1: Kinematic and Dynamic Modeling
http://jsst.ias.ir/article_132806.html
In emergency situations, where there is no possibility of using terrestrial-based or space-based telecommunication platforms or when there is a need for providing telecommunication services in remote, rural or hilly areas which are faced with lacking telecommunication infrastructures, typically using tethered balloon-based telecommunication technology is the best choice. Despite all the advantages of using this technology, small and limited coverage area is the biggest drawback of using tethered balloon platforms. In this paper, using a tethered balloon equipped with antenna pointing mechanism is proposed in order to, extend their small coverage area to a large region, in addition to benefit from inherent tethered balloons technology advantages. In this regard, dynamic and kinematic modeling of the proposed antenna pointing mechanism is discussed. In this research, the kinematic model is validated using RoboAnalyzer software and Robotics MATLAB toolbox. Antenna pointing mechanism provides the rotation ability for the antenna in two Azimuth and Elevation directions which increased the coverage area dramatically.3-dimensional Direct Simulation Monte Carlo Simulation of Thruster Plumes
http://jsst.ias.ir/article_137263.html
The interaction of thruster plumes with satellite components can have undesirable effects, such as disturbance force/torque, thermal loading, and species deposition in the surfaces. The purpose of this paper is to use the Direct Simulation Monte Carlo (DSMC) method to analyze the 3D plume impingement flows and investigate its effects. Two impingement problems are computed. The impact of a jet of nitrogen on an inclined flat plate is considered. Good agreement is found between surface quantities calculated by DSMC and experimental data. The plume of a hydrazine control thruster firing in a model satellite configuration is simulated. Surface quantities and net impingement effects are calculated. The effects of partial displacement of the thruster locations on the results have also been investigated. The results show that a 20% displacement of the thruster location can change the disturbance force/torque by up to 15% of the initial values.Collision Prediction of Spacecraft for Space Traffic Management
http://jsst.ias.ir/article_130642.html
In this article collision probability method is used to satellite collision risk analysis. Among different methods introduced for determining collision probability, Patera's (2005) and Chan methods are chosen to define Noor satellite collision to the other space objects. According to criteria described in the article, Advanced Conjunction Analysis Tools of STK software applied for collision risk analysis. The software, determine position of each object in space using Two Line Elements and appropriate propagation model according to altitude of the orbit. So collision probability calculated by one of the cpllision probability methods. If derived prababilty is larger than 10-3, so its necessary to schdule for suitable maneuver to avoid collision.System Design and Simulation of Air-spacecraft Aerospike Nozzle by Utilizing the Computational Fluid Dynamics (CFD) Method
http://jsst.ias.ir/article_132762.html
The main purpose is to introduce the performance system design and optimization method of aerospike nozzle for different aero-space conditions. For this purpose, some of the important parameters of the aerospike nozzle structure and cold flow condition tests in the nozzle optimization are studied. The methods of designing the Aerospike nozzle and its governing equations are described and the proposed design model is described and important factors are expressed in this type of nozzle. therefore, the design of a complete nozzle is made by aerospike and is supported by an existing design sample. Then, in order to optimize the nozzle, three cuts of 20%, 40% and 60% of the nozzle end are analyzed. The standard for comparison and optimization in these three slices is the Mach number of the output current. The results of this comparison show that the most efficient aerospike nozzle is a 40% cut nozzle based on the flow charts and contours of this aerospace nozzle.Numerical study on the effects of nozzle geometry and creating swirly flow inside the injector nozzle on the performance of an engine
http://jsst.ias.ir/article_132933.html
In this study, the effects of geometry and spiral rifling like guides inside the injection nozzle on the performance of an engine are investigated, using AVL Fire software. To do so, firstly injectors with different nozzle geometries and their resultant spray patterns were simulated. Numerical results of this step show that creation of spiral rifling like guides inside the nozzle increases the spray cone angle and improves fuel atomization quality. In the next step, effects of using forgoing nozzle geometries on sample engine characteristics were studied and the related results compared to those of common cylindrical injectors. Numerical results of this step clearly show the superior performance of nozzles with spiral rifling like guides. In this case, SFC reduces up to 32 percent while the engine power and it's torque rises more than 63 percent. Also the amount of pollutants like NOx reduces 12 percent with respect to common cylindrical nozzles.Effect of Simulated microgravity condition on cells proliferation and myostatin gene expression in differentiated skeletal muscle cells (C2C12)
http://jsst.ias.ir/article_133109.html
Muscle atrophy is one of the problems that astronauts face after returning to earth. Myostatin is a known negative regulator of muscle growth. This study aimed to investigate the effects of simulated microgravity condition on mouse myotube cells (C2C12) growth and the myostatin gene expression. The morphological studies and MTT cytotoxicity assay showed no significant alternation in cells after 48h simulation microgravity, however, after 72h ~40% of cell death accrued (p&lt;0.05). The AO/PI staining and DNA fragmentation analysis confirmed this observation too. Analysis of the gene expression revealed that simulated microgravity reduced myostatin gene expression significantly after 48h (p&lt;0.0001), however, after 72h, increased significantly (P&lt;0.001). So, inhibition of myostatin expression in differentiated myocyte cells of astronauts could be an effective procedure to reduce skeletal muscle atrophy under microgravity condition.experimental study of dynamic stability for a entry capsule in supersonic flow
http://jsst.ias.ir/article_137255.html
Due to the lack of existence of control surfaces in entry capsules, the subject of static and dynamic stability is always important. In this paper, these coefficients are investigated experimentally for the case of forced oscillation at supersonic flow. In this experimental study, the effects of freestream Mach number, mean attack angle and pitch frequency on dynamic stability coefficients were evaluated. According to the results, in Mach 1.8, the geometry starts to be dynamically unstable. One approach to overcome this problem is to change the average attack of angle of the model. This change in the mean attack of angle, similar to the results presented for the five-degree mean angle, will lead to dynamic stability.Design and Simulation of Single Capillary Injector and Circular Injector Plate for a Monopropellant Thruster
http://jsst.ias.ir/article_137256.html
In this research, design and simulation of a single capillary injector and three-hole circular injector plate of a 10N Hydrazine monopropellant thruster were performed. Ansys Fluent software was used to simulate the injector and injector plate . Volume of fluid (VOF) method was used to simulate such a flow and turbulence was simulated by k-e model. The characteristics of the injector and injector plate including mass flow rate and average velocity in the injector nozzle were calculated by changing the inlet pressure. The results showed that the injector and the injector plate have the ability to supply the desired mass flow rate of the monopropellant thruster at a known design pressure. In fact the capillary injector has replaced swirl injector with hollow cone spray used in the previous version of this thruster. The dimension of the chamber was significantly reduced by using the capillary injector, which reduces both the volume of the expensive iridium catalyst and weight of the thruster.Thermal Effects of the Space Environment on the Radiation Characteristics of a Reflector Antenna in LEO Spacecrafts
http://jsst.ias.ir/article_137257.html
Antennas, which are usually installed on the outer shell of these systems, are therefore always exposed to the thermal fluctuations of the space environment. Thermal fluctuations cause the antenna surfaces to expand, contract and distort and can cause the antenna to malfunction. In this paper, the effects of thermal expansion and contraction due to an LEO orbital mission on the radial characteristics of two X-band reflective antennas, one broadband antenna and the other narrowband, And the resulting radiation characteristics are compared with the characteristics of equivalent sample antennas at ambient temperature. Analyses show that narrowband antennas are very vulnerable to thermal fluctuations and, therefore, it is necessary to choose the material of the antennas from materials whose thermal expansion coefficient is very small. In addition, choosing the appropriate protection method to maintain the optimal performance of the antenna is one of the most essential activities in the construction of space antennas.Design and Configuration of Ground Sample Components of Low Propulsion Monopropellant Thruster Using Some Engineering Software
http://jsst.ias.ir/article_137258.html
Monopropellant thruster are used to inject a satellite into orbit or control its position on three axes in space missions. One of them is hydrazine thruster which is widely used. In this research, design of the injector, decomposition chamber and nozzle of a 10N hydrazine monopropellant thruster have been performed. The capillary injector was designed using Fluent software for this thruster which was able to supply the mass flow rate of the thruster (5 gr/sec). The decomposition chamber contains catalyst granules and its dimensions were selected based on the complete decomposition of hydrazine. The nozzle was designed by RPA software. The validation of the design with RPA software was checked by a numeric code. This code was able to calculate the dimensions of the decomposition chamber based on the amount of hydrazine decomposition. Accordingly, the results of both design methods are strongly consistent with each other. At the end of the design, the final thruster design and drawings were prepared.Optimized Dimension Design of Catalytic Chamber of a 10 N Thruster
http://jsst.ias.ir/article_137259.html
In this paper, the catalyst bed of a 10 N hydrazine monopropellant thruster was designed. The catalyst bed is including iridium granules, which is used to decompose the hydrazine in monopropellant thruster. Hydrazine must be decomposed almost completely in the catalytic chamber, because it is a carcinogenic chemical fuel and on the other hand, achieving the maximum power from the thruster is also an important goal. As a result, the effect of change in catalytic chamber length on the mass fraction of chemical species including hydrazine, ammonia, nitrogen, and oxygen was studied. Also, after determining the length of the catalytic chamber, the diameter of the nozzle throat corresponding to the same length was determined.Study of the effect of the microgravity on the expression of angiogenesis marker in endothelial progenitor cells
http://jsst.ias.ir/article_137260.html
A study of the effect of microgravity on the endothelial progenitor cells is useful both in understanding cardiac changes in astronauts and in using microgravity as angiogenic stimuli. The aim of the present study was to investigate the effect of microgravity on VEGFR-2 and CD34 angiogenesis markers. Following extraction of progenitor cells from peripheral blood and its confirmation, gene expression was assessed by real-time PCR, and cell viability was assessed by MTT assay. The extracted cells were endothelial progenitor cells in terms of shape and surface markers CD31 and CD144. Microgravity increased the VEGFR-2 gene expression by 3.5 times after 24 hours. CD34 expression increased by 50% after 3 h but reached control level after 24 hours. Microgravity appears to have a positive effect on the expression of angiogenic markers and stimulation of endothelial progenitor cells, and it may be used as a new environment to differentiate these cells into blood vessels and to treat heart disease.Parametric Study of Aeroelastic Instability Boundaries of Space Launch Vehicle in Subsonic Flow
http://jsst.ias.ir/article_137261.html
In the present work, the frequency-domain aeroelastic stability analysis of space launch vehicle body in the flight condition of initial launch phase is presented for a range of geometric parameters, structural characteristics, and other parameters such as thrust force. The aeroelastic model is derived using structural assumed modes and quasi-steady aerodynamics. The pressure distribution of subsonic flow on the 3D configuration is determined by boundary element method. Non-uniform Euler-Bernoulli beam including torsion spring junctions along the body with free-free ends is used to model the structure, and its modal analysis is performed by finite difference method. Concluded results illustrate variation in parameters not only could vary the aeroelastic instability boundary, but also might cause the instability type changed (from divergence to flutter), which its main reason is replacement the second instability of the aeroelastic system with the first one. Furthermore, it is demonstrated that the follower thrust force restricts the aeroelastic stability but maintains the instability type.Experimental study of the effect of using space sandwich structures for protection against space radiation
http://jsst.ias.ir/article_137262.html
Sandwich panels are used in various industries due to their high special strength. It is used in ultra-light aerospace structures. In this paper the protective effect of sandwich structures used in ultralight space structures against gamma rays is investigated. Eight structures of the most widely used structures used in space structures such as telecommunication antennas and satellite bodies are exposed to radioisotopic sources of gamma rays (Amercium barium and cesium) with energies of 60 kV, 80 kV, 382 and 66 kV, have been compared to each other. Surface material (aluminum and carbon), surface thicknesses and honeycomb cell dimensions are the most important evaluation parameters. In this paper, different structures have been compared using the "special protection" parameter and the best structure from a protection perspective has been identified and reported.Form-Finding and Free Vibration Analysis of a Class-One Triplex Tensegrity Prism
http://jsst.ias.ir/article_137436.html
This paper deals with form-finding and free vibration analysis of a pre-stressed class-one triplex tensegrity structure. The form-finding is performed via a two-step procedure, the nodal coordinates connectivity matrix, and structural element force density determination. Accordingly, the possible states for the nodal coordinates and the structural force density of the triplex prism have been determined by trial and error (based on topology and member type knowledge) to satisfy the force density, and equilibrium matrices rank requirements. Based on different structural topologies, the equation of the motion in the frequency domain for free vibration analysis of the system is derived using the spectral element approach and dynamic shape functions. Simulations are provided for different system heights and the top-bottom aria ratios and compared with the FEM. The numerical simulations in the form of a comparative study of the natural frequencies of triplex tensegrity prism with different heights and cross-sections represent the system&rsquo;s robustness with different topologies for single or multi-stage applications.Cost Estimation for Space Propulsion Systems and Human Resource Cost and The Project Implementation Time optimization
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The purpose of this paper is to present the cost estimation and optimization of space propulsion systems. Thus, choosing optimal propulsion system (from fuel and oxidizer aspect) is done in order to increase the efficiency and decrease the cost. Also, human resource cost and technology development time based on the consideration of labor cost effect on the personals motivation have been optimized. To this end, cost estimation and optimization algorithm has been drawn and suggested. The suggested algorithm has two steps. The first step in the algorithm is concern to cost estimation for seven fuel and oxidizer components. In the second step, labor cost and project implementation time is estimated and optimized based on the optimal space propulsion system derived from the previous step. Here, the objective functions are propulsion system technology development cost and time. On the other hand, the purpose is to consider the salary enhancement and consequently efficiency enhancement, time decrease and cost decrease.Extensive Regional Telecommunications Coverage in Emergency Condition using Satellite and Tethered-Balloon Equipped with Antenna Pointing Mechanism – Part 2: Operation Modes and Controller Design
http://jsst.ias.ir/article_143733.html
In this paper, in order to provide telecommunication coverage for a wide geographical area, the use of a network consisting of an LEO satellite and a Tethered-Balloon equipped with antenna pointing mechanism is proposed. The proposed telecommunication network is able to send the collected data to a mission center outside the covered region and receive the required telecommands, while providing a telecommunication link between the users in the covered region. To control and point the antenna beams towards desired targets, an Adaptive Dynamic Surface Controller is designed. Determining the required operating modes, designing a mode management algorithm and extracting the appropriate reference trajectories for each operating mode are among the discussed issues in this paper. The Uniform Ultimate Boundary (UUB) stability of the closed-loop system is proved and the performance of the control system is studied by simulation. The proposed communication network and control system are able to provide wide telecommunication coverage in remote areas or emergency situations.Adaptive Generalized-Minimum-Variance Attitude Control of a High Pointing-accuracy Remote Sensing Satellite
http://jsst.ias.ir/article_143734.html
Many studies have investigated the problem of external disturbance rejection and also increasing the attitude control system&#039;s robustness against the parametric uncertainties. Due to stochastic properties, noise effect minimization becomes an interesting and challenging problem in the field of spacecraft attitude control that has been underestimated, while control actuators and attitude sensors themselves are important sources of noise generation., the main purpose of this paper is to (i)control the satellite&rsquo;s attitude and (ii)minimize the variance of output, simultaneously. The Minimum Variance controller, which is considered the simplest type of model predictive controller, has a powerful capability for minimizing the effects of output noise. This feature makes it a suitable control scheme for space-based high-resolution photography missions. so,, we described the conventional Minimum Variance regulator method at first, then an Incremental version of the regulator has been presented to solve the tracking problem. Finally, the generalized minimum variance controller which can control both minimum-phase and non-minimum-phase systems is derived for a high pointing accuracy spacecraft. The simulation results show the efficiency of the proposed controller to restrain the noise effects in a high-resolution tri-stereo imaging mission.Investigation on Performance Characteristics of Hydrazine Monopropellant Thruster according to Reaction Chamber Adiabatic Temperature
http://jsst.ias.ir/article_143736.html
In this paper, by creating and developing a code based on thermodynamics and gas dynamics equations, the performance characteristics of a 1N hydrazine monopropellant thruster such as thrust force, specific impulse, characteristic exhaust velocity, and propellant mass flow rate have been studied theoretically in terms of reaction chamber temperature. In this regard, by taking into account the adiabatic assumption, the reaction chamber temperature of monopropellant thruster has been analyzed zero-dimensionally using the ammonia dissociation rate as an independent variable under equilibrium and non-equilibrium conditions and it has been analyzed one-dimensionally using the hydrazine and ammonia homogeneous and heterogeneous reaction rate constants. Also, the effect of nozzle throat thermal expansion on reaction chamber pressure, thrust force, and propellant mass flow rate and the effect of reaction chamber pressure on ammonia dissociation rate and consequently on reaction chamber adiabatic temperature under thermodynamic equilibrium conditions have been studied.Design of an nonlinear extended state observer to estimate unmeasurable information on the problem of flying objects guidance
http://jsst.ias.ir/article_144706.html
Proportional navigation is one of the most widely used methods in guiding flying objects. This method requires the rotation rate of the line between the interceptor and the target to calculate the guidance command. For a variety of reasons, including cost savings, simple sensors are used to measure tracking information, including line of sight angle. Therefore, some non-measurable information such as the angular velocity of the line of sight must be estimated using mathematical equations. Due to the noise and other problems, the use of derivatives is not desirable in this situation. Therefore, in this paper, an extended nonlinear observer is used to estimate the angular velocity of the line. Due to the nonlinear dynamics of the intercepting of flying objects, a nonlinear type of observer has been selected. By performing a computer simulation, the correct operation of the proposed observer is shown.Attitude and Vibration Control of a Flexible Spacecraft using Hybrid Adaptive Super-Twisting Non-singular Terminal Sliding Mode Control
http://jsst.ias.ir/article_145937.html
In this paper, a robust adaptive hybrid control approach based on a combination of super-twisting and non-singular terminal sliding mode control (STNSMC) approaches for vibration and attitude control of a flexible spacecraft with fully coupled dynamic is developed. The proposed adaptation law eliminates the need for bounds knowledge of external disturbances and uncertainties. Then an ST-based NSMC generates a continuous control signal to reject the Chattering phenomenon, the non-singular terminal switching control law with the ability to generate continuous control commands to eliminate the chattering phenomenon. Moreover, finite-time convergence is achieved, and the singularity problem has been avoided. The overall stability of the system has been demonstrated using the Lyapunov theory. One of the essential features of the proposed control algorithm is to prevent overestimation of control gains and faster convergence rates comparing to conventional ST and non-singular terminal SMC approaches. The simulations in the form of a comparative study for large-angle maneuver reveal the advantage of the proposed approach.Bearing only tracking for maneuver target using nonlinear second-order Markov model
http://jsst.ias.ir/article_146179.html
In this paper, in addition to investigation and analyzing the dynamic model of a maneuver target, a new method based on the Interaction Multiple Model (IMM) method is presented to solve the tracking problem in presence of measurement noise. In this procedure, two models are used along with an extended Kalman filter for each model, for estimation of the states related to stochastic target model. To this end, a specific weight is calculated adaptively for each model and the final estimation of the target is obtained from the weighted sum of the modes related to each model. In this paper, second order Markov models are used to better describe the system behavior which leads to a decrease in the number of required motion models. This means that the previous two models are used to decide on the next model, and a much better algorithm is provided than the first-order IMM algorithm.Effects of Injector Pressure Drop on the Performance of a Monopropellant Hydrazine Thruster
http://jsst.ias.ir/article_146180.html
The effects of injector pressure drop on the performance of a catalytic reactor are studied experimentally. The injectors were simple orifices. Dynamic interactions between the injector and the reactor determine the transient behavior of the system. Results showed that the injector pressure drop affected neither the decomposition reaction efficiency nor the ignition delay time. However, pressure response time increased, and pressure roughness decreased with increasing injector pressure drop. Interestingly, the response time curve had a slope change at a 20% pressure drop. As discussed in the paper, the slope change is a result of cavitation phenomena in high pressure drop. It is concluded that cold injector tests are not enough for injector design validation, and performance tests are necessary tasks.Data Augmentation Investigating in improving the performance of deep learning model for building segmentation using aerial images
http://jsst.ias.ir/article_146181.html
Deep learning is a modern method of image processing and data analysis that has entered the field of urban management with promising results and high potential. The purpose of this study is to investigate data augmentation techniques in improving the results of segmentation of buildings using aerial images with high spatial resolution and deep learning method. For this purpose, MSB building data set and MapNet model were used. The model was trained and evaluated in three stages without data augmentation, with data augmentation of geometric transformations and with data augmentation of geometric and photometric transformations. The results of model evaluation showed that using geometric transformations as data enhancement techniques, F-1 and IoU score evaluation criteria have increased by 0.5 and 0.55%, respectively, and using data techniques Incremental geometric and photometric transformations increased by 1.41 and 1.57 percent. This increase was visually observed in the improvement of the segmentation of dense areas of the building and the discontinuity of large-scale buildings.System-level evaluation of the operation of different solar array structures for various CubeSat configurations
http://jsst.ias.ir/article_146184.html
In this paper, the feasibility and performance of using solar arrays equipped with sun concentrators, along with other conventional solar array structures, in CubeSats, is investigated for the first time. For this purpose, seven different structures of solar arrays have been defined and implemented for more than 24 different CubeSat configurations from 0.25U to 27U. Then, by calculating important system-level parameters such as power generation density, power generation cost, reliability of solar arrays, and also a newly proposed parameter, called shape fit factor, the performance of these structures for the introduced configurations are evaluated and compared. To this end, and by considering rational coefficients, a cost function consisting of the four above-mentioned parameters is defined as the degree of merit of different solar array structures used in each CubeSat configuration. The results show that alongside the use of deployable solar arrays, using concentrating solar arrays can provide new capabilities for CubeSats to overcome the challenge of generating sufficient power.Military use and arms race in space from the perspective of international law
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Today, one of the main concerns of the Committee for the Peaceful Use of Outer Space (COPUOS) and its subcommittees is the issue of militarization in space law. Top space countries such as the United States, Russia and China have added to this concern by using advanced space military equipment. Therefore, the international community must look for desirable and practical solutions to solve this problem in order to prevent militarization and the creation of an arms race in space. Based on this, the present article tries to investigate the military prohibitions governing space activities in order to prohibit such activities in outer space by analyzing the military use of space and legal documents and explaining the conventional and customary system governing space treaties and by examining some dual-use space-based weapons; Conduct a descriptive analysis and reveal more about the negative aspects of the military use of space.A New Adaptive Controller for The Three ‎Axis Satellite Simulator Based on Continuous ‎Time Delay Petri Nets Tool
http://jsst.ias.ir/article_155434.html
This paper presents a new control methodology based on Continuous Time Delay Petri Nets (CTDPN) tool for the attitude control of satellite simulator. The graphical and mathematical features of this tool help the expert designer to design an appropriate controller using graphical model easily, and then apply the necessary changes to the mathematical model. In this approach, the controller gains are derived from the states and some other variables. Thus, the system states and variables must be available. The new gain tuning algorithm consists of three stages. First, A simulation environment is made for mathematical modeling based on the CTDPN tool and controller design. Secondly, using optimal methods, the controller gains are calculated at any given time and the data are collected. Finally, using the database, a relationship between the set of variables and the gains are derived. Experimental results indicate the promising performance of the controller in comparison to the conventional controller applied to the satellite simulator platform. The results indicate that the designed controller is robust against variation of parameters, as the controller gains are tuned based on the system state and variables.Design, fabrication, and test of a cryogenic liquid oxygen-ethanol engine
http://jsst.ias.ir/article_155436.html
The aim of the present research is to obtain the ability to use the cryogenic propellant engines on a laboratory scale. In this regard, it is necessary to build some experimental motors and investigate the their performance parameters. The liquid oxygen as a common oxidizer and ethanol as a green fuel have been selected as propellant components. The engine is designed to produce 400 kgf force at the nominal condition. The pintle type injector has been chosen in which liquid oxygen and fuel are flowed in the axial and radial directions, respectively. The combustion chamber has been protected against overheating by applying the regenerative cooling. However, the laboratory feature of the engine design has provided the using of water instead the cooling propellant. All main components of the engine such as injector, igniter, and flow controllers, are examined by the cold tests. A comprehensive test facility is designed and set up for hot fire tests in which the performance of almost all parameters can be evaluated. Fifteen fire tests have been performed. Maximum obtained pressure and evaluated combustion efficiency were about 75% of design values.Miss Distance analysis of First-Order Explicit Guidance Law with/without radome effect
http://jsst.ias.ir/article_155438.html
The miss distance analysis of the first-order explicit guidance law (EGL) is carried out using linearized equation of motion in the normalized form in order to obtain normalized miss distance curves. The initial heading error, constant target, acceleration limit, radome refraction error, and fifth-order binomial control system are considered. Moreover, body rate feedback is added to the explicit guidance law as a well-known classical compensation method of the radome effect as in proportional navigation. The analysis is performed for different values of the power of the alpha function, defined as the time decrease rate of the zero-effort miss to unit control input. As a special case, the EGL with unit power gives the first-order optimal guidance strategy for minimizing the integral of the square of the commanded acceleration during the total flight time. For the performance/stability analysis, the rms miss distance versus turning rate time constant and radome slope can be plotted for different values of the power of alpha function.Design and Dynamic Analysis for Vertical and Horizontal Cylindrical Body in Reentry Flight
http://jsst.ias.ir/article_155439.html
To create drag and reduce the speed of space payloads in the phase of entering the atmosphere, the payload body itself can be used as brake mechanisms without using additional tools. The approach analyzed in this paper is the separation of the nose and then the stability of the cylindrical body in horizontal or vertical mode. First, by
numerical solution, the cylindrical body is aerodynamically simulated in the flight conditions entering the
atmosphere, and the location of the center of mass is designed to achieve static stability. Then, by developing the equations of motion of atmospheric reentry using aerodynamic coefficients and derivatives calculated by DATCOM, the flight parameters for both modes are compared and evaluated. The simulation results show that the horizontal flight is more efficient and is able to create better conditions for opening the parachute and landing. Another advantage of atmospheric reentry flight in horizontal mode is the proper distribution of aerodynamic heating and reduction of heat load in certain points of the payload.Heterologous Expression of Shiga-Like Toxin Type 2 in Microgravity Condition
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Gravity is an influential force on living organisms on earth, including microorganisms. E. coli O157: H7 causes complications such as bloody diarrhea and hemolytic uremic syndrome in humans and immunization is the main way to fight it. Subunit B of Shiga-like toxin type 2 (STX2B), binding agent of bacterial toxin to target cells, is a candidate for the recombinant vaccine to prevent disease. Due to the quantitative and qualitative increase in the expression of some recombinant proteins under microgravity, the STX2B recombinant protein expression was examined under simulated microgravity conditions on clinostat device. After confirmation of the recombinant by immunological methods, its expression was performed under microgravity and after the protein purification by chromatographic column, its amount was measured. The results showed that despite the decrease in expression under microgravity, which was probably due to lack of proper aeration of the culture medium, recombinant protein was still produced under microgravity condition.