Hello Reader!! Welcome to another article on Rocket Science. In this article, I will discuss a very important topic, or you may consider as the most important topic, named Propulsion System. This is one of the most complicated topics of rocket science. Don't worry, I will keep it simple for you. If you are new to space science, please go through the previous articles for a better understanding.

We discussed a little about the propulsion of a rocket in the first article and we found that to propel a rocket in the desired direction we need to exhaust mass in the opposite direction. So, the primary objective of the propulsion system is to exhaust mass in the opposite direction of the motion of the rocket. The exhaust of mass generates thrust which tends to move the rocket in the desired direction. The generated thrust depends upon the exhaust velocity. The higher velocity of exhaust mass generates higher thrust.

In a rocket, fuels are combusted in a Chamber in presence of oxidizers. Hot gases are generated in this combustion and these gases are exhausted through a Nozzle with a high velocity which creates the thrust to propel the rocket. Studies reveal that the velocity is directly proportional to the temperature of the combustion chamber. A higher temperature of the combustion chamber leads to a higher exhaust velocity of product gases and a higher thrust. So, fuels to be used are chosen such that they produce a higher temperature when combusted.