نشریه فناوری در مهندسی هوافضا
سال سوم شماره 2 (پیاپی 9، تابستان 1398)

In this paper, the dissipative particle dynamic method is used to simulate the electrosmotic micro pump as the main part of a spatial-chemical propulsion system. In this simulation, the micro-pump is driven by the principle of  electrosmotic flow.Furthermore,the effective parameters, such as channel dimensions, applied voltage, surface effect, or zeta potential are analyzed. This research focuses on developing a simulation method for applying external force (electrosmotic force) as well as developing a method to a channel with different sizes and conditions. Our results include velocity profile in a channel with different effective parameters. The result were compared with and validated by analytical solution. It was shown that the electrosmotic method is an ideal method for transferring fluid as a micro-pump in different conditions and also in fine-scales applications, such as in micro-satellites.

New product development process include several activities and decisions. It starts with idea stage and ends when product enters market stage. Concurrent engineering is a product development approach that helps improving the performance of companies by reducing costs, increasing quality, creating new knowledge, and having a shorter product development time. In this research, the evolution of concurrent engineering in space projects and issues related to the implementation of concurrent engineering in design facilities were examined. For this reason, European Space Agency's Concurrent Design Facility and NASA Integrated Mission Design Center have been studied. The implementation of concurrent engineering in Instituto Superior Técnico's Concurrent Design Facility has also been studied.

Growing the number of satellites ready to be launched emphasizes the need for reduction of space hardware and subsystems cost, volume, and mass. Realizing these reductions can be implemented deploying new mechanisms for space structures. The performance benefit margin of deploying structures increases, as the size of the structure increases. Thus, it makes the technology more attractive for large-scale space systems. Examples of satellite components benefiingt from the utilization of inflatable structures including solar arrays, gravity gradient booms, communication antennas and solar sails. This paper discusses different types of deploying mechanism with their advantageous and disadvantageous focusing on solar arrays and required driven equipments after being placed in an operational orbit.

This paper presents advanced controllers for maneuver and vibration control of dynamic systems with rigid-flexible coordinates. Stability analysis of such a control system is one of the important issues. The control of flexible spacecrafts or flexible manipulators with rigid-flexible body dynamics has challenges that encourage designers to develop advanced controllers. Each of these control systems has some advantages and some disadvantages. The purpose of the present paper is to study various control design methods and to review the literature by addressing the weaknesses and strengths of existing techniques.

Basic plant research under complex space conditions is required. this is frequently quoted by the world's space agencies, such as NASA. The aim of the present research is to investigate the effects of simulated microgravity on pollen germination and tube growth of Lily. Pollen viability was ascertained by staining with acetocarmine stain. Pollen grains were germinated on the growing media containing 10% sucrose, 1.6 mM H3BO3, 1 mM Kcl, 0.1 mM CaCl2 (pH=5.7), and were incubated both in 1g and on the clinostat. After incubating for 2 h, pollen grains were studied to count for germinated grains and to determine percent germination and pollen tube length. The germination rate of pollen grains showed a tendency to increase under microgravity condition. However, pollen tube length showed a decrease when incubation was performed in simulated microgravity.

This paper is mainly concentrated on performance improvement and miss-distance reduction in a typical guidance system. These goals would be achieved by adding some attitude control motors (ACM) to the existing guidance algorithm. The ACM system usually contains some disposable thrusters, which are installed on lateral body of a vehicle. An extra force would be applied to the vehicle body through each thruster activation. Hence, it may cause a torque about the center of gravity. Then the induced rotation can be used to the attitude control. For increasing the agility and supplying the lateral acceleration in the end game phase, the lateral thrusters may be added to the guidance system. The yaw and pitch components of the line of sight (LOS) rates would be used to guide the vehicle with multiple actuators. For this purpose, a six degree of freedom vehicle model would be generated, considering the physical information, engineering assumptions, and adaptations images. The vehicle model would be firstly obtained by the DATCOM software. Then, the guidance system is numerically simulated in the MATLAB environment. The effectiveness of the proposed guidance method is shown compared with the existing algorithm.