Research Paper
Ghasem Kahe; Maysam Mohammadi-Amin; Arash Sefidan Benisi
Volume 10, Issue 1 , June 2017, Pages 1-13
Abstract
Various strategies have been developed to increase the safety of spacecraft crews, among which the Launch Abort System has been widely considered by the space centers across the world. The launch abort system should be able to carry the crew module away from the failed launcher or rocket in a short time ...
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Various strategies have been developed to increase the safety of spacecraft crews, among which the Launch Abort System has been widely considered by the space centers across the world. The launch abort system should be able to carry the crew module away from the failed launcher or rocket in a short time in accordance with the predetermined profile and recover the crew module on the ground. While the main part of the vehicle flight consists of the tracking, reorientation, and settling phase; attitude control in the flight path is done via the roll and pitch channel. Non-linear dynamic inversion flight control is considered for the attitude control of the LAS. Tracking the predetermined profile for the angle of attack as well as the sideslip angle and maintaining the stability of the vehicle in the flight path are considered as the control objectives based on the requirements. Simulations and analytical evaluations indicate the outperformance of the proposed controller for the attitude control of LAS in line with the predetermined profile.
Research Paper
Mostafa Esmaeili
Volume 10, Issue 1 , June 2017, Pages 15-25
Abstract
Trapped vortex combustor (TVC) is a compact combustor which represents the high efficiency in flame stabilization. In this study, turbulent reacting flow through trapped vortex combustor is numerically simulated. In order to model turbulence, the K-ω-SST and scale adaptive simulation (SAS) models, ...
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Trapped vortex combustor (TVC) is a compact combustor which represents the high efficiency in flame stabilization. In this study, turbulent reacting flow through trapped vortex combustor is numerically simulated. In order to model turbulence, the K-ω-SST and scale adaptive simulation (SAS) models, and to model combustion, the species transport and probability density function (PDF) approaches are used. To verify the numerical model, numerical results are compared with the available experimental data. There is a good agreement between the mean and RMS values of temperature and emission indices (CO, unbernt hydrocarbon (UHC) and NOx) obtained from numerical results and experimental data. Moreover, simulation is performed for different values of equivalence ratios and mainstream inlet temperatures and results show that with a constant value of equivalence ratio, by increasing the mainstream inlet temperature, combustion efficiency increases, while CO and UHC emission indices decrease.
Research Paper
fatemeh Sadeghi-kia
Volume 10, Issue 1 , June 2017, Pages 27-34
Abstract
This study focuses on the characteristics of plasma antennas for their application in space communication systems. Structural and functional characteristics of plasma antenna are presented to evaluate their capability of being used in space missions. Numerical and experimental analysis results of the ...
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This study focuses on the characteristics of plasma antennas for their application in space communication systems. Structural and functional characteristics of plasma antenna are presented to evaluate their capability of being used in space missions. Numerical and experimental analysis results of the plasma antenna show that the resonant frequency of the antenna is controllable by changing the applied power, thus allowing different transmitting frequencies with a single element. This property leads to the reduction of the antenna elements in a limited area and the simplification in the layout of onboard communication systems as well as a decrease in the interferences of the electromagnetic waves. Analysis of the circular array of plasma antenna shows a novel beam forming mechanism with a high directivity in the space.
Research Paper
Javad Vaziri Naein Nejad; F. Ommi; Seyed Hossein Moosavi
Volume 10, Issue 1 , June 2017, Pages 35-45
Abstract
The addition of proper-sized metal particles to the effervescent fuels increases the density of exhaust gases from rocket engines and the trust consequently. On the other hand, the addition of non-optimized metal particles causes combustion instability. Thus, the separation of proper-sized metal particles ...
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The addition of proper-sized metal particles to the effervescent fuels increases the density of exhaust gases from rocket engines and the trust consequently. On the other hand, the addition of non-optimized metal particles causes combustion instability. Thus, the separation of proper-sized metal particles is under consideration here. In this study, among different methods of separating the aluminum particles in the fuel, the performance of the conic cyclone separator has been studied and the numerical results are validated by the experimental data. With a specific particle diameter and speed, the less the angle between the cyclone body and the horizon, the higher would be the separation efficiency. In addition, for increasing the separation efficiency of aluminum particle, it is recommended to build the inlet section of cyclone at the lower point of cyclone body.
Research Paper
amirhossein tavakoli; ali faghihi; S.Mohammad Mehdi Dehghan
Volume 10, Issue 1 , June 2017, Pages 47-53
Abstract
Simulating environmental conditions for the satellite attitude sensors is a fundamental requirement of hardware in the loop tests of attitude determination and control subsystem. In this paper, a new design for simulating sun vector and magnetic vector is presented. The operating environment for attitude ...
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Simulating environmental conditions for the satellite attitude sensors is a fundamental requirement of hardware in the loop tests of attitude determination and control subsystem. In this paper, a new design for simulating sun vector and magnetic vector is presented. The operating environment for attitude sensors is simulated using a sun simulator, a two-degree-of-freedom table for changing the attitude of the sun sensor, and a three-axis Helmholtz coil. The sensors measurements showed that with this setup, the sun and magnetic vectors can be created with an acceptable accuracy using the orbital position and the attitude of the satellite. So, the test bed can be used for attitude determination of hardware in the loop tests.
Research Paper
Alireza Rezaee; Niloofar Nobahari; Hakime Barghi Zanjani
Volume 10, Issue 1 , June 2017, Pages 55-60
Abstract
This paper aims to propose the interference and also investigates the channel effect on power allocation issue. Here, the particle swarm optimization (PSO) method is employed in order to find the optimal solution. Because of the value of resources in the satellite telecommunication systems, optimizing ...
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This paper aims to propose the interference and also investigates the channel effect on power allocation issue. Here, the particle swarm optimization (PSO) method is employed in order to find the optimal solution. Because of the value of resources in the satellite telecommunication systems, optimizing the use of power allocation is very important. In these systems, because of non-zero side lobe, there exists an interference between beams that affects the allocation problem. To assess the efficiency of PSO algorithm, the obtained results are compared with the Duality Theory. The analogy is conducted through three different scenarios: In the first scenario, it is supposed to have interference between each beam and the three adjacent beams. The second scenario assumes that the first beam interferes with other beams. Finally, in the third scenario, the analysis of channel conditions of each beam and its effect on the power allocation problem is provided. The objective functions for the proposed method are the total system capacity and sum of the square of difference between the requested traffic and the allocated beam power. The results indicate that the proposed algorithm improves the solution in each scenario and implements justice to the power allocation issue.