Journal of Space Science and Technology
Year:2013 | Volume:6 | Issue:3 (16)|Papers Count:9

In this paper, a particular propulsion system including, liquid rocket engine, fuel and oxidizer tank and related pressurizing system, have been surveyed. The procedure is based on a nonlinear mathematical model which has been simulated in Matlab Simulation environment. In propulsion systems, identifying system performance is essential, because if we can accept ability describe the dynamic behavior of the system components in nominal and transient regimes; we can reduce the associated costs during design and development. Following, results of Propulsion system hot test are compared with model that shows acceptable accuracy of simulator code. In addition to leading research, how to use this model to identify the causes of failure is shown. Match analysis and compatibility testing, after disassembling objective observations show considerable performance model for similar applications.

This paper presents an explicit guidance method which could be used in the problems of orbit correction for sub-orbital modules. This method is based on solving the Lambert problem. Two efficient methods of solving the Lambert problem are introduced and compared. Using of the selected method a guidance scenario is developed which is capable of solving the problem under investigation. All of the methods of solving the Lambert problem are based on spherical gravitational field and aerodynamic forces are not considered by them. In order to consider those important factors, a method is presented which increases the accuracy of guidance block computations. Finally using of developed method, two sample problems are investigated. Applying the developed method, a guidance block is prepared which performs the required maneuvers in a mission. Monte Carlo simulation confirms the ability of developed method in different conditions.

In this paper predicting of position of satellite based on extended kalman filter with considering hardware implementation consideration and simultaneously maintaining desired accuracy is investigated. For this purpose, first, effective forces on orbital dynamic and nonlinear equation of orbital motion are presented. In order to increasing accuracy of prediction in position of satellite, J2, J3 and J4 harmonics of potential function of the earth are considered and future position of satellite is predicted using linearized dynamic model and applying EKF on this model. Here Measurement data are position and velocity vector of satellite which are extracted by GPS receivers. Since in this paper systematic satellite design is considered, scenario of “ON TIME” of GPS receivers based on power consumption considerations is discussed. Finally simulation results for a LEO satellite and comparing these results with STK results, shows accuracy of presented modeling and equations.

When a solver is used for analyzing the hypersonic reentry vehicles, high speed and accuracy of the solver results are the basic parameters in the design process. In the present study, the results obtained by solution of laminar boundary layer equations using integral matrix method and approximate method are assessed in aero heating prediction around hypersonic axisymmetric reentry bodies. The results show that the applied methods have suitable accuracy in aero heating and high computational speed for reentry vehicle design. Space marching method in numerical simulation of boundary layer equations and applying less grid point in the boundary layer due to use of integral matrix method rather than other methods efficiently decrease computational costs. Also, high robustness of approximate method in the heat flux prediction over the reentry surface makes it useful for design process. Using a special approximate relation for stagnation region improves the aero-thermodynamics results.

In this paper design of transfer trajectory from Earth park orbit to a halo orbit around L1 of Earth-Moon system and return trajectory from halo orbit to the Earth are investigated. Since satisfying constraints and boundary conditions at the end of trajectory is an important point in trajectory design, we deal with a two point boundary value problem. Considered constraints in this paper include height, orthogonally of position and velocity vectors for reducing required Del-V for orbital transfer and flight path angle. Due to complex dynamics of three body problem and also in order to satisfying these constraints and suitable trajectory design, the multiple shooting methods based on differential correction is used.

Space radiation environment has concerned about proper performance of electronic systems and equipment used in the space due to a variety of space radiations. The radiation hardening techniques are required to all parts of the system in such environment. Therefore careful studies should be done on the mechanism of radiation damage in these systems. Shielding is one of radiation hardening technique. The radiation effects on electronic components can be done using radiation simulating softwares. In this work, displacement damage, vacancies and ionization values in silicon and gallium arsenide with layers of metal as a shield have been calculated using TRIM software. The results showed that the more thickness and more elements with high atomic number of shield made more resistance to radiation. Thus, damage in electronic devices would be less. Also, the damages resulted from the incident beam of helium ions is much higher than that of hydrogen ions.

To improve the performance of satellite antennas, use of a high-impedance surface is purposed. High impedance surfaces are known as artificial magnetic conductors. The designed magnetic conductor includes an array of a Jerusalem Cross frequency selective surface which is connected to the ground via four pins. All conducting parts are made of Aluminum. The dielectric is Arlon AD 270 that fills the space between the ground and the JC frequency selective surface. The dielectric is made of fiberglass reinforced by Polytetrafluorethylene (PTFE). In 4.73GHz and 7.43GHz, structure operates as a magnetic conductor. Using computer simulations, this structure is compared with a widely used artificial magnetic conductor. Aluminum and polymer chain of Carbon and Fluorine are composed of light elements, therefore using this material in antenna structure not only can improve specification of antenna but also can reduce cosmic ray effects.

OSL dosimeter system was introduced first time in 1963 and it has been used for space application science 2005 by space organizations. In this work we try to design and fabricate this system in Iran for the first time .Basic physical quantum of this system is optically stimulated luminescence. This system consist of OSL material, Optical section for Stimulation and reader section. In this work, first the basic theory of OSL phenomena has been reviewed, then the space applications and the advantage of this system has been compared with other dosimeter system. Afterward laboratory construction of this system and some characterizations of that such as primary calibration by Co-60 source, has been introduced. Finally, results of evaluation of this system shows that, this fabricated system has linear response function in rang of 1-10 Gy.