Shahrokh Marzban; Kamal Mohamedpour; Somye Pirzadi
Volume 5, Issue 3 , October 2012, , Pages 21-31
Abstract
After setteling the LEO satellite in the given circuit, the ground station needs to communicate with it for the received of information and control of its subsystems. Due to the fact that satellite communication channels are influenced by shadowing conditions, if a line of sight (LOS) signal exists between ...
Read More
After setteling the LEO satellite in the given circuit, the ground station needs to communicate with it for the received of information and control of its subsystems. Due to the fact that satellite communication channels are influenced by shadowing conditions, if a line of sight (LOS) signal exists between the receiver and the transmitter, then the radio channels conditions are good and the Additive White Gaussian Noise channel is modeled as Rician distribution. However, under poor conditions and in the lack of LOS, channel model is Rayleigh, and due to the radio link conditions the channel will be switched between these two models. In a proper model, the time varying behavior of the station – satellite radio link should be considered. The importance attached to this issue is due to its considerable effect on the selection of modulation type, design of channel access method, and error control. In this view, the present study has sought to momentarily determine the range of variations in error probability. Through calculations and simulation, the Bit Error Rate received during the satellite trajectory has been obtained for any given moment and its range of variations has been determined.
E. Aminzadeh; Y. Allagheband Hosseini
Volume 6, Issue 1 , April 2013, , Pages 21-30
Abstract
Astrounats, as envoys of mankind in outer space, are always faced with innumerable perils. Thus, their rescue and return has always been in the forefront of Humankind’s endevours to regulate outer Space activities. outer Space Treaty as lex generalis and The rescue and return Agreement as lex especialis ...
Read More
Astrounats, as envoys of mankind in outer space, are always faced with innumerable perils. Thus, their rescue and return has always been in the forefront of Humankind’s endevours to regulate outer Space activities. outer Space Treaty as lex generalis and The rescue and return Agreement as lex especialis are both relevant in this regard. Although there has never been an opportunity to put their provisions on this matter into test, no one can deny the magnitude of the duty to rescue and return in developing mankind’s activities in ouer space and its harmonizing effect on interntional co-operation. However scientific and technological advancement of the last decade coupled with the ever increasing possibility of space tourism endevours in outer space has caused new debates concerning the possibility of applying the provisions of the rescue and return agreement to space tourists. This article is an attempt to find an answer to this question.
Sh. Amiri; M. Fahami
Volume 6, Issue 2 , July 2013, , Pages 21-28
Abstract
In this paper GPS radio occultation has been introduced as a way to extract the electron density of the ionosphere. A GPS radio occultation occurs when a receiver on-board a LEO spacecraft tracks a GPS satellite as it sets or rises through the earth’s atmosphere. The recorded occulted signal phase ...
Read More
In this paper GPS radio occultation has been introduced as a way to extract the electron density of the ionosphere. A GPS radio occultation occurs when a receiver on-board a LEO spacecraft tracks a GPS satellite as it sets or rises through the earth’s atmosphere. The recorded occulted signal phase and amplitude of the tracked satellite can then be analyzed to derive atmospheric electron density.TEC Monitoring has been studied tocorrect the error caused by the ionospher electron density in the telecommunication satellite global positioning system are briefly introduced as a tool for this method. One occultation event studied near one of the brazilion oson destations and the electron density curves obtained from the data reported Brazil Ionosonde are compared with radio methods.
seyed aliakbar kasaeian; Masoud Ebrahimi
Volume 11, Issue 2 , September 2018, , Pages 21-31
Abstract
The present study aims to present a safe, robust and fast orbital rendezvous guidance. The scheme improves the rate of convergence to equal point until the chaser spacecraft reaches the proximity target. Then, the robust guidance structure is transformed in order to avoid singularity and provide safe ...
Read More
The present study aims to present a safe, robust and fast orbital rendezvous guidance. The scheme improves the rate of convergence to equal point until the chaser spacecraft reaches the proximity target. Then, the robust guidance structure is transformed in order to avoid singularity and provide safe rendezvous for reaching the target. Switching is conducted in the guidance scheme by utilizing a self-defined sign function. Moreover, a new modified saturation function is employed instead of the discontinuous part of the sliding mode. The Lyapunov function approach guarantees the asymptotic stability. Numerical simulations are conducted by both linear and nonlinear models of relative dynamics. Mean anomaly, angular velocity, and eccentricity of target orbit are considered as the uncertainties. Finally, the results indicate the performance and robustness of the proposed guidance in the presence of non-linearity, uncertainties, and disturbances, compared to the conventional sliding mode.
Amie ali Nikkhah; farsahd somayehee; Jafar Roshanian
Volume 11, Issue 3 , December 2018, , Pages 21-32
Abstract
In this paper, the aim is to simulate night-sky images for use in star-sensor designing software. For this purpose, a comprehensive and precise algorithm was developed to simulate night sky images based on the ideal pinhole method and the use of Gaussian distribution functions. Then, in order to create ...
Read More
In this paper, the aim is to simulate night-sky images for use in star-sensor designing software. For this purpose, a comprehensive and precise algorithm was developed to simulate night sky images based on the ideal pinhole method and the use of Gaussian distribution functions. Then, in order to create more realism, sources of random and systematic errors, the elongated images due to the high dynamics of the platform, as well as the asymmetric back-lighting of the moon, the sun, and the planets of the solar system have been simulated. Finally, considering the importance of realism in the problem-solving simulation approach, the use of precision ray tracking method as an alternative to the ideal pinhole method is suggested.
GPS and navigation GPS)، GLONASS، GALILEO
Tania Mansour Fallah; Behzad Voosoghi; Seyyed Reza Ghaffari-Razin
Volume 17, Issue 1 , March 2024, , Pages 21-36
Abstract
In this paper, the aim is to use the least squares support vector regression (LS-SVR) for spatio-temporal modeling of the ionospheric total electron content (TEC). In order to do this, the observations of 15 GPS stations in the north-west of Iran have been used in the period from 193 to 228 at 2012. ...
Read More
In this paper, the aim is to use the least squares support vector regression (LS-SVR) for spatio-temporal modeling of the ionospheric total electron content (TEC). In order to do this, the observations of 15 GPS stations in the north-west of Iran have been used in the period from 193 to 228 at 2012. Comparing the results of the new model with support vector regression (SVR), artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS), Kriging model, GIM and international reference ionosphere 2016 (IRI2016) as well as TEC obtained from GPS. The analyzes performed show that the averaged RMSE of ANN, ANFIS, SVR, LS-SVR, Kriging, GIM and IRI2016 models in two interior control stations are 3.91, 2.73, 1.27, 1.04, 2.70, 3.02 and 6.93 TECU, respectively. Also, the averaged relative error of the models in two interior control stations was calculated as 15.98%, 9.39%, 7.85%, 6.09%, 11.60%, 12.54% and 26.56%, respectively. Analysis of the PPP method shows an improvement of 50 mm in the coordinate components using the LS-SVR model. The results of this paper show that the LS-SVR model can be considered as an alternative to global and empirical models of the ionosphere in the study area.
A. Rezaiha; M. Anbarloi; M. Farshchi
Volume 3, Issue 2 , January 2011, , Pages 23-30
Abstract
Although Pulsed Plasma Thruster (PPT) has first been utilized in a space mission in 1964 but after more than four decades, it is still a space rated technology which has performed various propulsion tasks from stationkeeping tasks to three-axis attitude control for a variety of former missions. With ...
Read More
Although Pulsed Plasma Thruster (PPT) has first been utilized in a space mission in 1964 but after more than four decades, it is still a space rated technology which has performed various propulsion tasks from stationkeeping tasks to three-axis attitude control for a variety of former missions. With respect to the rapid growth inthe small satellite communityand the growing interest for smaller satellites in recent years, PPT is one of the promising electric propulsion devices for small satellites (e.g. CubeSats) as the following advantages: simplicity, lightweight, robustness, low power consumptions, low production costs and small dimensions. In spite of the fact thatthe issues relating to μPPT scaling have been investigated to a certain degree in recent years, it is felt that for an application on CubeSats this topic has to be investigated in greater detail for even smaller dimensions and better performance. Therefore a laboratory benchmark rectangular breech-fed pulsed plasma thruster (PPT) was designed, developed and successfully tested in a bell-type vacuum chamber at 10-6 mbar for the first time in west Asia (Iran). The PPT has been tested while the main capacitor, which is a 35 μF, 2.5 kV oil-filled capacitor, has been charged with a wide range of voltage, ranging from 250 V to 1750 V making the system stored energy range from less than 1 J to 60 J, producing the impulse bit varying from 30 μN-s to 1.3 mN-s. This work initiated a research program in Iran for working on PPTs and miniaturization of PPTs while increasing the performance parameters. The present paper reviews the PPT design and the development briefly.
A. Ebrahimi; H. R. Fayazbakhsh
Volume 4, Issue 1 , July 2011, , Pages 23-28
Abstract
Within operational life of satellites according to their mission, need to change their operational orbits. This change can includes change in semi-major axis, inclination or plane of orbit (RAAN angle). For this propose, we can use Electrical Propulsion (EP). With respect to light weight of EP in cases ...
Read More
Within operational life of satellites according to their mission, need to change their operational orbits. This change can includes change in semi-major axis, inclination or plane of orbit (RAAN angle). For this propose, we can use Electrical Propulsion (EP). With respect to light weight of EP in cases which there is weight constraint, we use EP for transfer satellite to desired orbit. In this paper, we consider minimum-time transfer problem for these transfers. Initial and final orbits are circular and we assume thrust is continuous. Assuming constant acceleration, elements of orbit uniformly change and these changes analyze with Edelbaum Analysis
J. Roshanian; M. Ebrahimi; A. Bataleblu
Volume 4, Issue 2 , January 2012, , Pages 23-34
Abstract
The purpose of this paper is introducing the concept of nondeterministic optimal design or optimal design in the presence of uncertainty based on researches done in the past two decades. Therefore, after an introduction about uncertainty, the uncertainty and uncertainty modeling techniques are described. ...
Read More
The purpose of this paper is introducing the concept of nondeterministic optimal design or optimal design in the presence of uncertainty based on researches done in the past two decades. Therefore, after an introduction about uncertainty, the uncertainty and uncertainty modeling techniques are described. After that, thetraditionalmethodof dealingwith uncertaintyin thedesignis described. The importance of paying attention to the uncertainty and its benefits for different projects and companies is described. The third section is dedicated to introducing the methods of interval analysis, fuzzy logic and probability analysis, which are used in the analysis of uncertainty.The two general categories of nondeterministic design problems, the robust optimal design and reliability-based optimal design are reviewed. The next section introduces the application of nondeterministic design methods in the different disciplines and recent researches in the world on this topic. Finally, future aspects and challenges of the nondeterministic design are addressed.
S. Boorboor; S. A. H. Feghhi; H. Jafari
Volume 6, Issue 4 , January 2014, , Pages 23-28
Abstract
Shape and size of sensitive volume are the most important parameters to model electronic devices for calculation of the SEU rate from space radiations. So far different models have been proposed for estimation of the sensitive volume. In this work, results of three models including RPP, Tetrahedral and ...
Read More
Shape and size of sensitive volume are the most important parameters to model electronic devices for calculation of the SEU rate from space radiations. So far different models have been proposed for estimation of the sensitive volume. In this work, results of three models including RPP, Tetrahedral and Nested in calculation of sensitive volume have been compared with experimental result for AT60142 SRAM. GEANT4 as a Monte Carlo code has been used to calculate energy loss and energy straggling of ions with considering metallization and oxide layers. Comparisons between Monte Carlo and experimental results shows that RPP model estimates the SEU cross section with a large deviation in whole LET range, tetrahedral has good response in low LET's but don't follow experimental result for high LET particles and nested sensitive volume produce acceptable results for whole of LET range.
F. RasiMarzabadi; R. Meshkani; H. Pouryavi; M. A. Farsi; M. Ebrahimi
Volume 7, Issue 2 , July 2014, , Pages 23-33
Abstract
According to the importance of knowing aerodynamic parameters of parachutes used as recovery system of a sounding rocket, some launching tests were conducted to achieve the acceptable reliability. A testing rocket which simulated the recovery condition of the sounding rocket was used in these tests. ...
Read More
According to the importance of knowing aerodynamic parameters of parachutes used as recovery system of a sounding rocket, some launching tests were conducted to achieve the acceptable reliability. A testing rocket which simulated the recovery condition of the sounding rocket was used in these tests. Furthermore, the results of the tests used for validating a simulation code written for investigating the aforementioned two stage recovery system process. Some aerodynamic parameters of parachutes such as drag coefficient, opening force coefficient, and filling time, filling distance and drag area increase during inflation process were estimated from the tests in various conditions. The results show that for the first and second used drogue chutes with large canopy-loading, in contrast to the main parachute with small canopy-loading, the inflation parameters were not dependent on the height or air density. The drag area versus time shows linear variation for the first drogue chute, and shows second and third function for the other two parachutes. The situation of the second drogue chute in front of the main parachute affects the filling time of the main parachute. The distance between the parachutes, the ratio of their canopy areas and the air velocity are some parameters that affect the filling time. The results of this investigation could be worth for the design of a decelerator system, preciously.
M.M. Gheisari; S. M. Mirsajedi
Volume 7, Issue 3 , October 2014, , Pages 23-32
Abstract
In this research, second order level set method for simulation of grain burn-back analysis is presented and compared with the first order level set according to discretisation technique, accuracy , and CPU time. In this manner and at the first step, we describe total necessities of level set method that ...
Read More
In this research, second order level set method for simulation of grain burn-back analysis is presented and compared with the first order level set according to discretisation technique, accuracy , and CPU time. In this manner and at the first step, we describe total necessities of level set method that are grid generation, minimum distance function calculation, relative condition estimation, ballistic characteristics calculation, and obtaining results. Then, at the second step, we improve forth necessity of level set method by second order model. For validation of presented model, we consider many type of simple and complex grains and evaluate grain burn-back analysis. The obtained results indicate that second order model is more accurate than the first order model for simulation of complex grains. But, at the simple grains with more CPU time related to second order model, accuracy of two models are similar. A compromise between accuracy and CPU time suggest that one can use second order model for simulation of complex grains and first order model for simulation of simple grains.
Mehran Nosrat Elahi; Ali Reza Basohbat Novinzadeh; Mostafa Zakeri; Vali Bemani; Yazdan Emadi Noori
Volume 7, Issue 4 , January 2015, , Pages 23-37
Abstract
The design method presented in this paper is for utilizing, fast and easy system designing of orbital transfer block for transferring satellite from park orbit to destination orbit. The main purpose of this paper is system designing liquid propellant orbital transfer block with a new approach for ideal ...
Read More
The design method presented in this paper is for utilizing, fast and easy system designing of orbital transfer block for transferring satellite from park orbit to destination orbit. The main purpose of this paper is system designing liquid propellant orbital transfer block with a new approach for ideal orbital transfer and presenting a simple interfered systematic method for designing aerospace products. Designing orbital transfer block consists of designing all subsystems and integrating all parts of design. Designing all subsystems can be achieved with a meaningful connection between all system and subsystem constraints. In addition to systematic design approach to each of the design sub- algorithms, creating subsystem optimization environment according to physical performance of subsystem and also general integration of orbital transfer block system design in an optimized environment have been carried out. Final result of orbital transfer block design for a specific mission is through mass-dimension convergence of equations in integrated design. Design integration according to design matrix and optimizations and convergences of the design is discussed in the paper. According to presented method, which is scientific, functional and extensible to final design of the product, parametric process of results is briefly validated. So in this paper new method is provided for integrating the design in an optimized and collaborative convergence environment maintaining all systemic constraints and limitations to specify specifications of orbital transfer block systems and subsystems.
Hossein Mahdavy-Moghaddam; mohammad hadi Hamedi
Volume 10, Issue 2 , September 2017, , Pages 23-32
Abstract
Recently, a novel technique using dual throat nozzles is introduced for thrustvectoring applications. The present paper discusses this new technique. All thrustvectoring techniques are evaluated with some common parameters: nozzle dischargecoefficient, system thrust ratio, thrust vector angle and thrust ...
Read More
Recently, a novel technique using dual throat nozzles is introduced for thrustvectoring applications. The present paper discusses this new technique. All thrustvectoring techniques are evaluated with some common parameters: nozzle dischargecoefficient, system thrust ratio, thrust vector angle and thrust vectoring efficiency. For agiven micro turbine nozzle geometry, a double throat nozzle is designed usingdimensional scaling or geometrical analogy. Then, by comparing the results obtainedfrom a designed geometry for discharge coefficient, thrust vector angle and thrust vectorefficiency, the DTN performance is reported. The designed DTN deflected the vectorangle of 18 degrees with the fluidic injection flow rate equal to 10 percent of the primaryflow rate.
Behzad Mohasel afshari; Javad Haghshenas; Mohsen Abedi; Masoud Khoshsima
Volume 11, Issue 4 , December 2018, , Pages 23-30
Abstract
In this paper, a precise method for calculating albedo and IR heat flux applied to a satellite is presented. For obtaining albedo heat flux applied to a satellite, a point on the earth’s surface that sun flux reflected at that point and reach to the satellite is obtained, hence albedo heat flux ...
Read More
In this paper, a precise method for calculating albedo and IR heat flux applied to a satellite is presented. For obtaining albedo heat flux applied to a satellite, a point on the earth’s surface that sun flux reflected at that point and reach to the satellite is obtained, hence albedo heat flux reaches to a satellite is obtained as a function of longitude, attitude and longitude. IR heat flux is integration of emitting heat flux for points on the earth surface that in satellite’s view. Atmospheric transparency for calculating albedo and IR heat is considered for sun light and IR spectrum using MODTRAN algorithm using PcModWin software. For a generic LEO satellite, IR and albedo heat fluxes are calculated at a time period and compare with reference values. Obtained heat fluxes are used to obtain temperature variation of satellite’s components during its mission.
Amirhossein Edalatpour; Fatholah Ommi; Zoheir Saboohi
Volume 12, Issue 1 , April 2019, , Pages 23-40
Abstract
Micro-propulsion Systems are low thrust engines that be used in space missions like keeping satellite in orbit and changing orbit. These engines have several kinds and liquid propellant micro-propulsion is used in this project. In two propellant micro-propulsion systems, various fuels and oxidizers can ...
Read More
Micro-propulsion Systems are low thrust engines that be used in space missions like keeping satellite in orbit and changing orbit. These engines have several kinds and liquid propellant micro-propulsion is used in this project. In two propellant micro-propulsion systems, various fuels and oxidizers can be used. Kerosene is used as fuel and liquid oxygen is used as oxidizer in this project. First of all, a micro-propulsion is designed and analysis of combustion, heat transfer, nozzle exit flow and amount of performance’s parameters is done with RPA software. Similar to big engines, micro-propulsion systems have injectors, injection plate, combustion chamber and nozzle. Design of all of this parts will be explained. With manufacturing of designed model and perform hot fire test, accurate performance of engine is observed. Finally, performance’s parameters in hot fire test are compared with performance’s parameters in RPA.
mohammad shahbazi; mohammad razmjooei; Fatholah Ommi
Volume 12, Issue 2 , September 2019, , Pages 23-41
Abstract
In this research, the 3D grain burnback with quasi-one-dimensional internal ballistic in a solid rocket motor is simulated using the Level set theory and the utilization of Sections method, while achieving high accuracy in the simulation of green's post-back analysis time can also be significantly reduced. ...
Read More
In this research, the 3D grain burnback with quasi-one-dimensional internal ballistic in a solid rocket motor is simulated using the Level set theory and the utilization of Sections method, while achieving high accuracy in the simulation of green's post-back analysis time can also be significantly reduced. By using Section method, 3D grains are divided to many 2D grain, then 2D Level set is utilized to analyse grain burnback. Finally, the burning port of 3D grains are calculated by means of Interpolation. Also, to predict the internal pressure of the motor and the burning rate, a numerical code is written and coupled with grain burnback programme.
Space subsystems design: (navigation, control, structure and…)
Ehsan Maani; Peyman Nikpey; Ehsan Zabihian
Volume 14, Issue 1 , March 2021, , Pages 23-33
Abstract
n GEO communicational satellites, thrusts are being used for many missions such as station keeping, longitude change maneuver and actuators desaturation. These types of actuators need fuel and its estimation requires many complicated calculations. In this paper, a novel method based on availed data for ...
Read More
n GEO communicational satellites, thrusts are being used for many missions such as station keeping, longitude change maneuver and actuators desaturation. These types of actuators need fuel and its estimation requires many complicated calculations. In this paper, a novel method based on availed data for previous satellites is proposed for estimation of satellite fuel mass and it does not need mathematical modeling of satellite dynamics. Two methods, least square method and artificial intelligence, are used to this aim and two mathematical model are proposed for satellite fuel mass estimation. By applying the models to several previous satellites, it is shown that the models have lower than 5% average error. The proposed method in this paper is quick and accurate and can be utilized for GEO satellites feasibility study and conceptual design
Remote sensing
Kobra Yaghoubi; Alireza Safdarinezhad; Marzieh Jafari
Volume 14, Issue 3 , September 2021, , Pages 23-37
Abstract
Image fusion is known as a synergetic process for merging multispectral and panchromatic images contents. So far, various methods have been developed in which the usage of the frequency domain is one of them. The frequency-based image fusion techniques are performed using high and low pass filters. So, ...
Read More
Image fusion is known as a synergetic process for merging multispectral and panchromatic images contents. So far, various methods have been developed in which the usage of the frequency domain is one of them. The frequency-based image fusion techniques are performed using high and low pass filters. So, the determination of the sizes of these filters would be a challenge. In this paper, a weighted index is proposed to determine the sizes and shapes of the low and high filters in fusion of the panchromatic and multispectral images. In the proposed method, the weights of the spectral and spatial indicators are independently estimated for each image. So, the effects of the differentiation of the image contents and different range of the indicators are properly adjusted to reach the optimum filtering. The comparison of the best results obtained from the proposed method with the other well-known fusion methods, in the used datasets, was indicated an average improvement of 58% in RMSEs.
Space New Technologies
Hassan Naseh; Ali Alipoor
Volume 16, Issue 1 , March 2023, , Pages 23-34
Abstract
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 ...
Read More
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.
Remote sensing
somaye karimpour; Javad Sadidi; Seyed Mohammad Tavakoli Sabour
Volume 15, Issue 3 , September 2022, , Pages 23-32
Abstract
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 building using aerial images ...
Read More
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 building 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.
M. Tahaye Abadi; H. Kashani; N. Ariaeifar
Volume 2, Issue 1 , April 2009, , Pages 25-34
Abstract
The paper presents a kinematical model for a random positioning system which simulates microgravity conditions on the ground. The random positioning system contains two frames, with an experiment platform. The frames are rotated around two perpendicular axes by a random angular velocity that it causes ...
Read More
The paper presents a kinematical model for a random positioning system which simulates microgravity conditions on the ground. The random positioning system contains two frames, with an experiment platform. The frames are rotated around two perpendicular axes by a random angular velocity that it causes continuous changes in the orientation of experimental sample relative to the gravity’s vector. The angular velocity between random values is changed based on specific function in order to limit the generated spurious acceleration below a preselected threshold. The kinematical model yields criteria to evaluate the microgravity conditions on ground base. Such criteria are defined based on the mean values of acceleration and gravity components which are sensed by the rotating experimental sample.
M. Mirshams; L. Khaladjzadeh
Volume 3, Issue 1 , July 2010, , Pages 25-36
Abstract
Designing a manned spacecraft carrying one or two persons to low Earth orbits needs to recognize system level requirements and acquire technical data developed in this eria. Revising manned spacecrafts’ characteristics leads to recognize system level requirements and achieve applicable results ...
Read More
Designing a manned spacecraft carrying one or two persons to low Earth orbits needs to recognize system level requirements and acquire technical data developed in this eria. Revising manned spacecrafts’ characteristics leads to recognize system level requirements and achieve applicable results which are needed to design and development of such a spacecraft. Manned spacecraft characteristics comparing charts and figures show a roughly analogous pattern in terms of mass and dimensions and confirm the parallel subsystems have similar performance.
M. H. Korayem; M. Nazemizadeh; H. N. Rahimi
Volume 5, Issue 2 , July 2012, , Pages 25-34
Abstract
Flexible manipulators have plentiful applications in Aero-Space fields, due to their less weight and maneuverability. In fact, the ratio of their load carrying capacity to their weight, make them more excellent over their rigid ones. Moreover, these manipulators are known as good candidates in Aero-Space ...
Read More
Flexible manipulators have plentiful applications in Aero-Space fields, due to their less weight and maneuverability. In fact, the ratio of their load carrying capacity to their weight, make them more excellent over their rigid ones. Moreover, these manipulators are known as good candidates in Aero-Space applications because of their less energy consumption, and smaller actuators. In this paper, the dynamic modeling of the flexible manipulators are performed using Finite Element Method (FEM), and optimal control of point-to-point motion of robot is done via optimal control method. To dynamic modeling of flexible manipulator, each link of the robot is divided into sufficient elements, and total displacement of the element is presumed as summation of a rigid displacement and a displacement because of flexibility. By means of Lagrange’s principle, dynamic equations of the flexible robot are derived, and the effect of number of the on dynamic motion of the robot is considered. Also, for the optimal point-to-point motion planning of the elastic manipulator, the nonlinear dynamic equations of the robot is assumed as constraints of optimal control problem, and a proper cost function is defined including torque and speed terms. Then, variation of calculus and Pontryagin’s minimum principle are employed and optimality conditions are resulted in a set of nonlinear differential equations, which is solved numerically. The priority of the optimal control method on the optimal motion planning of the flexible manipulator is discussed, and simulations for a single-link elastic robot illustrate the applicability of the method.
M. A. Farsi; A. A. Eslami; R. Gorgin
Volume 7, Issue 1 , April 2014, , Pages 25-31
Abstract
Separation system is one of the most important systems in rockets. The influence of this system on mission success cannot be ignored. In this paper, reliability of a sounding rocket separation system is determined using block diagram and FMEA . This system is based on the flexible linear shape charge ...
Read More
Separation system is one of the most important systems in rockets. The influence of this system on mission success cannot be ignored. In this paper, reliability of a sounding rocket separation system is determined using block diagram and FMEA . This system is based on the flexible linear shape charge cross-section and a spring mechanism to accelerate separation. In this investigation, the reliability block diagram of the separation system including mechanical and electrical mechanisms is determined. By considering reliability of each component based on expert opinion and using separation system reliability block diagram, reliability of separation system is determined. Moreover, since spring mechanism is one of the most important parts of separation system, a complete FMEA analysis is conducted for this mechanism. According to this analysis, piston, cylinder, pin, and springs have the highest RPN number. Hence, these parts must have a high reliability. On the other hand, results are shown that bracket and bush have the lowest RPN number; therefore, it is not important for these parts to have a high reliability.
