Hello readers!! Welcome to another article on Rocket Science. In this article, I will discuss another type of propulsion system, Liquid Propulsion System. In the last article, I discussed the Solid Propulsion System. But there are some problems in using Solid Rocket Motor in the Upper-stages of a Launch Vehicle.

Liquid Propulsion Systems are a little complicated with respect to the Solid Propulsion System. But we will keep our discussion simple. If you are new to this domain, please go through the previous articles for a better understanding.

What is Liquid Propulsion Rocket?

Liquid Propulsion Rockets are those rockets that use fuels and oxidizers in liquid form to propel in a particular direction.

A liquid Propulsion system is generally termed as Liquid Propulsion Engine as it has moving parts.

Advantages of Liquid Propulsion Engine over Solid Propulsion Motor:

In the case of Solid Propellent rockets, the generated thrust can not be regulated after the ignition of the solid propellant grain. The thrust requirement is calculated before designing the propellant grain. So, they can not be throttled or restarted.

But in the case of an upper stage rocket, the thrust may not be calculated in advance.

For example, in the case of a satellite, the position and orientation always may not be perfect. Thrusters are required to bring them to a suitable position and orientation. The required thurst for this job varies and depends upon the satellite. Here Liquid Propulsion Engine comes into action. They can be throttled and restarted to produce thrust when required.

How does Liquid Propulsion Engine work?

In liquid propulsion systems, the propellants are stored in tanks and they are carried to the combustion chamber by some means. Then the propellants are injected into the chamber using an injector. There may or may not be an ignitor in the chamber. The propellants are combusted in the chamber and hot gasses are produced. These hot gasses are exhausted through the nozzle with high velocity. This generates thrust which propels the rocket in the desired direction.

Different parts of Liquid Propulsion Engine:

The liquid Propulsion system consists of four major parts:

Propellant Tanks

Feed System

Combustion Chamber

Nozzle

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