This lecture provides an overview of space propulsion systems, focusing on their principles and applications. It begins by discussing the importance of propulsion in space exploration and the various types of propulsion systems available. The instructor explains the basic working principles of propulsion, including the Tsiolkovsky rocket equation, which describes how rockets achieve thrust by ejecting mass at high velocity. The lecture also covers the differences between propulsion in Earth's atmosphere and in space, highlighting the challenges posed by microgravity and vacuum conditions. Additionally, the instructor discusses specific impulse and exhaust velocity as key performance metrics for propulsion systems. The lecture concludes with a recap of the significance of thrust and the various factors that influence propulsion efficiency, including mass flow rates and energy conversion methods. Overall, this lecture serves as a foundational introduction to the principles of space propulsion, essential for understanding advanced topics in aerospace engineering.