Sharif Digital Repository

The purpose of this project is to identify the most suitable propulsion system for a micro-satellite in LEO for orbit, altitude, and pointing corrections. Hence, different propulsion systems are investigated by comparing the propulsion thrust, mass, volume, cost, and specific impulse. In the first chapter, an introduction is given on micro-satellite and its subsystems. The second chapter discusses first the different types of disturbances that a microsatellite might face and second the control requirements for the satellite to counterbalance these disturbances. In the third chapter, different space propulsion systems are briefly reviewed and their main performance parameters discussed. In... 

Special geometrical sections, known as “duct”, which can be installed on merchant vessels stern in order to improve propulsion system and propeller performance, today have evolved considerably. The force which produces by the propeller depends on efficiency of propulsion system. In the way of improving the efficiency of propulsion systems, by using these special geometrical sections, to much research have been done from the mid-twentieth century. The Wake Equalizing Ducts (WEDs) in addition to conduct the more uniform fluid flow to the propeller disk (which causes to improve the propeller operation), affect on flow separation in ship stern zone and will decrease the separated flow zone.... 

Monopropellant thrusters are one of the most common types of propulsion systems that are used extensively in space applications. Especially thrusters with a capacity of less than 50N, they are used on space satellites and are developing rapidly. Problems such as contamination, toxicity of the propellant, difficulty in storing and custody, as well as price, led to the removal of the hydrazine from the focus of attention and focus on green propulsion. One of these, is the green propellant of hydrogen peroxide, which is decomposed in the proper catalytic vicinity, and the only chemical decomposition products are oxygen and water vapour. The present study aims to design and construct mono... 

Improving the performance of modular, low-cost autonomous underwater vehicles (AUVs) in such applications as long-range oceanographic survey, autonomous docking, and shallow-water mine countermeasures requires improving the vehicles’ maneuvering precision and battery life. These goals can be achieved through the improvement of the vehicle control system. A vehicle dynamics model based on a combination of theory and empirical data would provide an efficient platform for vehicle control system development, and an alternative to the typical trial-and-error method of vehicle control system field tuning. As there exists no standard procedure for vehicle modeling in industry, the simulation of... 

Fault detection and diagnostics of rotating machinery are considered one of the most important issues. Propulsion system, power generator motor, shaft couplings and transmissions system prepare trust necessary to move the high speed craft. Vibration measurement, control and obtain the critical velocity and dynamic forces on bearings and joints is one of the most important issues in this case. In this project dynamic modeling of surface piercing system was analyzed which this system has ability to change trim and steering angles by hydraulic cylinder. Dynamic modeling regard to the driving forces of surface piercing propeller modes of in different operation state is performed. At the end,... 

Injecting liquid fuel into the cross flow of air provides high penetration of the liquid, rapid mixing with air, and increased efficiency. This method has widespread applications in the propulsion systems of gas turbines, scramjets, turbine blade cooling, and fuel injection for engine afterburners. One of the design strategies for future aircraft engines is to reduce pollutants using fuel spray into the cross flow instead of direct jet fuel injection and using renewable energy sources. The applications of cross flows include injecting fluid through rotating pressure injectors in exhaust flows, injecting fluid through pressure-rotating injectors in radial injectors, and using slinger...