Liquid Fuel Rocket

Overview

Liquid Fuel Rocket/ Liquid Rocket is a rocket with a Rocket engine that uses a Liquid propellant  Liquids are desirable because they have relatively high density and high specific impulse. Usage of liquid tanks allows the volume of propellant tanks to be relatively low.

What is a Liquid Rocket Engine ?

A liquid Rocket Engine is a Rocket engine that uses liquid as a fuel for combustion. In a liquid rocket, stored fuel and stored oxidizer are pumped into a combustion chamber where they are mixed and burned. The combustion produces great amounts of exhaust gas at high temperatures and pressure. The hot exhaust is passed through a nozzle which accelerates the flow. Thrust is produced according to Newton's third law of motion.

po

nozzel

exhaust

Ve

pe

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m

Ae

fuel

oxidizer

pumps

throat

exit - e

V = Velocity

m = mass flow rate

p = pressure

Thrust = F = mVe + (pe - po)Ae

Where is it Used ?

Liquid rocket engines are used on the Space Shuttle to place humans in orbit, on many un-manned missiles to place satellites in orbit, and on several high-speed research aircraft.

How does the Engine work ?

Liquid rocket engines are used on the Space Shuttle to place humans in orbit, on many un-manned missiles to place satellites in orbit, and on several high-speed research aircraft. 

In a liquid rocket, stored fuel and stored oxidizer are pumped into a combustion chamber where they are mixed and burned. The combustion produces great amounts of exhaust gas at high temperatures and pressure. The hot exhaust is passed through a nozzle which accelerates the flow. Thrust is produced according to Newton's third law of motion.

The amount of thrust produced by the rocket depends on the mass flow rate through the engine, the exit velocity of the exhaust, and the pressure at the nozzle exit. All of these variables depend on the design of the nozzle. The smallest cross-sectional area of the nozzle is called the throat of the nozzle. The hot exhaust flow is choked at the throat, which means that the Mach number is equal to 1.0 in the throat and the mass flow rate m is determined by the throat area. The area ratio from the throat to the exit Ae sets the exit velocity Ve and the exit pressure pe.

Types of liquid propellants

The liquid propellants, which are the working substance of rocket engines, constitute the fluid that undergoes chemical and thermodynamic changes. The term liquid propellant embraces all the various liquids used and maybe one of the following:
1. Oxidizer (liquid oxygen, nitric acid, nitrogen tetroxide, etc.)
2. Fuel (kerosene, alcohol, liquid hydrogen, etc.)
3. Chemical compound or a mixture of oxidizer and fuel ingredients, capable of self-decomposition, such as hydrazine
4. Any of the above, but with a gelling agent. Used only rarely.

Source Credits : NASA