Basics of rocket propulsion

Basics of rocket propulsion.

This article discusses 2 main types of rocket propulsion, solid and liquid fueled. Another type of rocket propulsion which would be electromagnetic thrusters such as ion and plasma thrusters. However these methods are more appropriate for long duration flights as their thrust is less but their efficiency is much greater than traditional chemical rockets.

Both solid fueled and liquid fueled rockets use a combination of fuel and oxidizer to ignite a fire inside the combustion chamber which is then forced out of the nozzle at great speed, 10x the speed of sound at sea level is not unheard of.

The thrust from this reaction is mostly placed on the bell housing of the nozzle. As the gases inside the combustion chamber try to escape they push against the walls of the nozzle propelling the rocket forward. The more pressure applied to the combustion chamber and nozzle driving the rocket forward the more efficient the rocket is.

There are several ways of increasing the pressure released by the combustion of fuel/oxidizer. One is to pump these chemicals to very high pressures before they are injected into the combustion chamber. Another is to heat the fuel as high as possible before entering the combustion chamber. Use of high density gases and chemicals that breakdown into their most basic elements is yet another way to get the most thrust out of your rockets.

The temperature of the gas as it exit’s the nozzle of the rocket is also important. The temperature of the rocket exhaust affects how fast the gas not only escapes the nozzle but also how much thrust will be lost to the atmosphere the rocket is traveling through. If the rocket exhaust is not close to the ambient pressure of the surrounding atmosphere then thrust will be sapped away as the atmosphere interferes with the exhaust.

Other factors relating to rocket efficiency include the size and shape of the nozzle as well as the speed of the craft. A rocket is most efficient when you are traveling at if not greater than the speed of the exhaust being shot out of the rocket.

As the combustion temperatures of the rocket typically is greater than the melting temperatures of the metals used to make the motor special consideration has to be given to cooling the rocket. There are in fact dozens of ways though to keep your rocket from melting itself. From simply using it in short bursts to lining the combustion chamber and nozzle with a material that will gradually burn away before the temperature gets high enough to melt the engine to using the heat from the exhaust to heat the fuel/use the cold exhaust to cool the engine.

As you can see a rocket is not that complicated though getting one to work best for your application may seem like more art than science at times.