This document provides an introduction to rocket propulsion systems used in NASA's space shuttle. It first describes that rocket engines operate based on Newton's third law of motion. It then outlines the main components of rocket engines, including fuel, oxidizer, combustion chamber, and nozzle. Several types of fuels and engine cycles are described, such as cryogenic fuels, solid rocket boosters, monopropellants, and pressure-fed, gas generator, staged combustion, and expander cycles. Design parameters for rocket engines like specific impulse and thrust are also covered. The document concludes with an overview of challenges such as cooling and combustion instabilities, and alternatives like solar electric propulsion and ion thrusters.