Journal of Space Science and Technology
Year:2016 | Volume:9 | Issue:3 |Papers Count:6

In this paper, an approximate solution of required velocity with final position constraint is derived using a piecewise linear gravity assumption for elliptical earth model. In this approach, the total flight time is divided into several time intervals and the gravitational acceleration is assumed to be linear at each interval. The solution gives an explicit relation in terms of the current position vector, desired final position and flight time in three dimensions. The accuracy and computational burden of the method are obtained numerically in terms of the number of time intervals, and compared with linearized solution and Zarchan's iterative algorithm. Numerical solution shows that the present method has better accuracy than the two mentioned approaches with the same computational burden up to a range angle of 18 deg for minimum energy trajectory in an elliptical earth model. The presented method can be extended for two or multi-body problem and also for the computation of sensitivity matrix of required velocity.

This paper is dedicated to determining the orbit of a satellite by using Unscented Kalman Filter (UKF), in which, a GNSS is used as the observation sensor. During this goal, firstly we have simulated the satellite orbit; considering oblations effect. Secondly, exploiting a nonlinear model of orbit dynamics, preliminary orbit determination is prepared via UKF algorithm. The range between the satellites and space vehicle as the parameter of observation in the filter is obtained. Afterwards, the estimated preliminary output data is corrected and more precise position of the GNSS satellite is determined based on predicted observations errors. Consequently, the outcomes of the research exhibits the acceptable satellite orbit determination error range.

Orbital parameters are raised as one of the main inputs of electrical power subsystem and thermal control subsystem of a satellite. Some variables such as eclipse time, sun incidence angle to the panels, albedo and thermal radiation of Earth are dependent on satellite orbital features. In this paper, all of the parameters above are simulated using precise simulation methods within the satellite mission. That is, the process of optimal orbital design is performed with the aid of evolutionary optimization methods. This process is aimed at minimizing number of mission days that misses the assurance of satellite power supply in addition to minimizing thermal load exerted to satellite and also its standard deviation. At last, a pair of optimal solutions for two different configurations is compared.

In this article the design and the development of spool type pin puller mechanism from concept model to engineering model was expressed. At first, present models and designs were investigated and the conceptual design was based on positive aspects of these models and in order to better study the operation of mechanism, the concept model was built 5 times bigger than the real model. After this model the pre-engineering model with 350N pulling force was designed and built. It was tried to reduce the operational defects of concept model like fuse operation and the rupture of warping wire, in the pre-engineering model. Assembling of the model was carried out with special tools and operation test carried out in room temperature. In the engineering model pulling force was increased to 500 N and the material of inside parts was changed due to special electrical and mechanical conditions. Temperature and atmospheric test conditions were considered in the last model and the model was prepared to pass all qualification tests. Vibration tests and also Temperature tests were performed in vacuum chamber with respect to space standards. Reliability calculations were done on each pin puller parts and at last reliability of whole pin puller system were obtained.

The mechanism is a set of mechanical components that are connected and can move relative to each other. If it can be used in space, it is called space mechanism. The space mechanisms are widely used in space missions. Many space missions have been failed due to malfunction of space mechanisms. This clears the importance in research and development of space mechanism. The deployable mechanisms are categorized based on geometry and performance. A variety of space deployable mechanisms are investigated and their advantages and limitations are introduced in this paper. All types of space mechanisms which have been used since the beginning of space travels are covered in this paper, hence this paper is a thorough review paper on this topic. This feature of paper, makes it unique in the field of information about new space mechanisms and usable in the country space industry.

The main goal of this paper is development of multi-stage Launch Vehicle (LV) system design software based on advanced classical method. This software has been named Launch Vehicle Conceptual Classical Design (LVCCD). This software covers the complete syllabuses of LV System Design (LVSD) course. The main characteristic of the software development is to step by step training the LVSD. Also it can help the better understand in the course in the best quality and lower time. The algorithm used in the software developed according to the outline of LVSD (major design parameters, LV's mass-energy equations and velocity losses and etc.) and using the multi-stage LV statistical data. Hence, these advantages led to better understanding and conceive. Also LVCCD can improve the qualification of training. Finally, the LVCCD software evaluated and verified with the design software as Launch Vehicle Conceptual Design (LVCD) and PBRM by using existing multi-stage LV.