NASA, Public domain (link).
Rockets have advanced in the world. They have come from small weapons used in war to the giant space roaming vehicles they are today. Scientists are not sure when rockets were first used. Some think that rockets were first used in a war between the Chinese and the Mongols in 1232. Fire arrows were a rocket like weapon. The basic design was a long stick with a pouch of black powder attached to it. Mongols reported fire arrows that could destroy anything 2000 ft. from where they hit the ground. However some scientists think that these could just be advanced fire arrows. Koreans were later recorded using rockets that shot very far. Korean rockets were very much like the Chinese fire arrows and were arrows with small explosives on them. Other early uses for rockets were the well known fire works. The first fireworks were used in 1264 at a feast.
Today's rockets are vehicles which obtain thrust by pushing a substance out the bottom. Rockets achieve this usually by burning the fuel to obtain thrust. Modern rockets are made for commercial and military purposes. They are also used for interplanetary travel. The main types of rocket engines are solid fuel chemical propulsion, liquid chemical fuel chemical propulsion, cold gas chemical propulsion, and ion propulsion. They all have good and bad things about them.
Solid fuel chemical propulsion
Solid fuel chemical propulsion is the most basic of the 4 main types of rocket propulsions. This type is used in model rockets. It is simple, reliable, has few moving parts, and it has lots of thrust. It is probably the most simple of the types. It is a one-time use engine, though. It is used as a main booster rocket engine.
Liquid fuel chemical propulsion
This kind of rocket propulsion is one of the most common in commercial, military, and rockets used for interplanetary travel. It is reusable, controllable, and has lots of thrust. It is used as a main booster, and small control engine. A bad thing is it is a very complicated engine.
Cold gas chemical propulsion
This type of rocket engine is used for small control engines. It is reusable and controllable. It doesn’t have much thrust, though.