ROCKET

ROCKET
A rocket is a vehicle, missile or aircraft which obtains thrust by the reaction to the ejection of fast moving fluid from within a rocket engine.
The history of rockets goes back to the 13th century. By the 20th century it included human spaceflight to the Moon, and in the 21st century rockets have enabled commercial space tourism.
Rockets are used for fireworks and weaponry, as launch vehicles for artificial satellites, and for human spaceflight and exploration of other planets. While they are inefficient for low speed use, they are, compared to other propulsion systems, very lightweight, enormously powerful and can achieve extremely high speeds.
Chemical rockets operate by expanding hot exhaust gas made from propellant against the inside of a bell nozzle, this generates forces that both accelerate the gas to extremely high speed, as well as, since every action has an equal and opposite reaction, generating a large thrust on the rocket.
Chemical rockets contain a large amount of energy in an easily liberated form, and can be very dangerous, although careful design, testing, construction and use can minimise the risks.