Journal of Space Science and Technology
Year:2020 | Volume:13 | Issue:2 (43)|Papers Count:8

In the present work, the performance of True Proportional Navigation (TPN) with different profiles for effective navigation ratio in terms of the relative velocity angle with respect to line-of-sight is investigated due to initial heading errors and target maneuvers. Since an appropriate profile of effective navigation ratio for heading error is almost in contrary with the appropriate profile for maneuvering targets, a variable effective navigation ratio in terms of the relative velocity angle and its rate is introduced. In this way, the miss distance (MD) for the first two peaks of the normalized MD graph versus normalized final time, for example under an effective navigation ratio of 4, is reduced together. The analysis is carried out using normalized equations in polar coordinates for perfect and binomial fifth-order control systems without acceleration limit. Due to practical consideration, the effective navigation ratio is tuned and limited between 3 and 5.

In this paper, the heat transfer and ablation thermal insulators in solid rocket motor are investigated. Therefore, by collecting and solving the thermal ablation equations, a computer program, using MATLAB software, is developed which can predict the thermal response of insulators in different operating conditions and compare the performance of these insulators. The heat and mass transfer equations are considered in two dimensions in a solid body. We used the equations, finite volume method with implicit formulation for time dependency to solve equations. The reaction equation which written in the form of Arrhenius, is solved using Runge-Kutta method, and the density and the flux of the gas produced at each step are obtained. Also we represent a model for the rate of recession.

This paper aims to use H2 and H∞ norms to optimally place sensor/actuator patches on a flexible structure. Unlike most existing optimization methods, the proposed approach not only increases the norms of the controlled modes of the system but also it can reduce the system's spillover problems by taking into account the residual modes and reducing systems H2 and H∞ norms. The residual vibration of the system is captured considering sandwich structures and the finite element analysis. In order to show the optimal placement effect of piezoelectric patches, the vibrational behavior of the closed-loop system is controlled using strain rate feedback controller. Numerical simulation is performed to study the debonding effects between the sandwich layers.

In this study, a method for designing a thermal optimum reentry path based on aerodynamic database management has been developed using the Kriging and Co-Kriging methods. For the design of the reentry path in the conceptual design phase, the more precise the dynamical model of the reentry vehicle, the closer the path is to reality. One of the issues affecting the accuracy of the dynamic model of return vehicle is the aerodynamic coefficients in its flight envelope. For this purpose, in the present study using the new method, accurate aerodynamic data has been developed by combining the data from different solvers in the device flight envelope at the appropriate time. In the following, using the dynamic model and the developed reentry path design algorithm, the thermal optimal return path of the Orion device with constant coefficients and the exact aerodynamic database are compared, and the important parameters of reentry path, such as thermal flux and final velocity, are evaluated.

The CANSAT design, a simple and small scale of a satellite, is an experience for preparing for the design of a Life cycle of the space project. In this paper, the process of design and construction of ARTA CanSat, which is participated in the scientific-exploratory class of international competition in CANSAT Iran, has been written. The operation scenario is that an automatic scanner system, lands after releasing from 300 meters above ground level with using a recovery subsystem (parachute), which is controlled its downfall and landing position by the parachute controller system. During the descent, the data is transmitted by the sensors and sent to the ground station. After touchdown, the Hotwire system's operates and separates the parachute from the Rover section; Then CanSat with the moving on the ground by using the simpler section embedded underneath the structure, performing excavation while moving to the target point. Throughout the mission, the health of the biological payload is preserved.

The final phase of orbital rendezvous and docking has been studied in this article. The main objective is to control the position of a chaserthat can reach to the target in the minimum time, or in the other words, by passing the optimal path. Another important objective of this paper is the minimum energy consumption. In dynamic simulation, the equations of the linear form of Clohessy-Wiltshire (CWH) equationshave been utilized. In linear CWH equations, the change in either direction of X or Y will result the change in another direction and will affect the orbitaldocking operation. Inorder to achieve the objectives of this paper, the design variables should be optimized; To optimize the design variables, two methods i. e. genetic algorithm (GA) and particle swarm optimization (PSO) have been used. Finally, to evaluate the real conditions, the results will be investigated by applying uncertainty in the outputs of thrusters.

This paper presents a new unit to design dual linearly polarized reflectarray antenna at ku for satellite telecommunication. Two orthogonal sets of parallel dipoles are used for each polarization to achieve more degree of freedom in the design and wider phase variation in the unit cells, consequently. A 0. 3m Reflectarray Antenna with two distinct beams is fabricated and measured in an anechoic chamber. The measurements have been carried out for both polarizations (X and Y ) in the azimuth and elevation planes. This antenna has x-polarized beam at (θ 0=30º , ϕ 0=90º ) with 23. 7 dBi gain and y-polarized beam at (θ 0=30º , ϕ 0=0º ) with 24. 2 dBi gain at Ku-band. The proposed design has one layer and simple structure compared to the references as well as dual band and dual polarization capabilities.